Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

39 files changed, 23522 insertions, 0 deletions

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
new file mode 100644
index 0000000000..bae8f11070
--- /dev/null
+++ b/kernel/time/Kconfig
@@ -0,0 +1,213 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Timer subsystem related configuration options
+#
+
+# Options selectable by arch Kconfig
+
+# Watchdog function for clocksources to detect instabilities
+config CLOCKSOURCE_WATCHDOG
+	bool
+
+# Architecture has extra clocksource data
+config ARCH_CLOCKSOURCE_DATA
+	bool
+
+# Architecture has extra clocksource init called from registration
+config ARCH_CLOCKSOURCE_INIT
+	bool
+
+# Clocksources require validation of the clocksource against the last
+# cycle update - x86/TSC misfeature
+config CLOCKSOURCE_VALIDATE_LAST_CYCLE
+	bool
+
+# Timekeeping vsyscall support
+config GENERIC_TIME_VSYSCALL
+	bool
+
+# The generic clock events infrastructure
+config GENERIC_CLOCKEVENTS
+	def_bool !LEGACY_TIMER_TICK
+
+# Architecture can handle broadcast in a driver-agnostic way
+config ARCH_HAS_TICK_BROADCAST
+	bool
+
+# Clockevents broadcasting infrastructure
+config GENERIC_CLOCKEVENTS_BROADCAST
+	bool
+	depends on GENERIC_CLOCKEVENTS
+
+# Automatically adjust the min. reprogramming time for
+# clock event device
+config GENERIC_CLOCKEVENTS_MIN_ADJUST
+	bool
+
+# Generic update of CMOS clock
+config GENERIC_CMOS_UPDATE
+	bool
+
+# Select to handle posix CPU timers from task_work
+# and not from the timer interrupt context
+config HAVE_POSIX_CPU_TIMERS_TASK_WORK
+	bool
+
+config POSIX_CPU_TIMERS_TASK_WORK
+	bool
+	default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK
+
+config LEGACY_TIMER_TICK
+	bool
+	help
+	  The legacy timer tick helper is used by platforms that
+	  lack support for the generic clockevent framework.
+	  New platforms should use generic clockevents instead.
+
+config TIME_KUNIT_TEST
+	tristate "KUnit test for kernel/time functions" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Enable this option to test RTC library functions.
+
+	  If unsure, say N.
+
+config CONTEXT_TRACKING
+	bool
+
+config CONTEXT_TRACKING_IDLE
+	bool
+	select CONTEXT_TRACKING
+	help
+	  Tracks idle state on behalf of RCU.
+
+if GENERIC_CLOCKEVENTS
+menu "Timers subsystem"
+
+# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
+# only related to the tick functionality. Oneshot clockevent devices
+# are supported independent of this.
+config TICK_ONESHOT
+	bool
+
+config NO_HZ_COMMON
+	bool
+	select TICK_ONESHOT
+
+choice
+	prompt "Timer tick handling"
+	default NO_HZ_IDLE if NO_HZ
+
+config HZ_PERIODIC
+	bool "Periodic timer ticks (constant rate, no dynticks)"
+	help
+	  This option keeps the tick running periodically at a constant
+	  rate, even when the CPU doesn't need it.
+
+config NO_HZ_IDLE
+	bool "Idle dynticks system (tickless idle)"
+	select NO_HZ_COMMON
+	help
+	  This option enables a tickless idle system: timer interrupts
+	  will only trigger on an as-needed basis when the system is idle.
+	  This is usually interesting for energy saving.
+
+	  Most of the time you want to say Y here.
+
+config NO_HZ_FULL
+	bool "Full dynticks system (tickless)"
+	# NO_HZ_COMMON dependency
+	# We need at least one periodic CPU for timekeeping
+	depends on SMP
+	depends on HAVE_CONTEXT_TRACKING_USER
+	# VIRT_CPU_ACCOUNTING_GEN dependency
+	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
+	select NO_HZ_COMMON
+	select RCU_NOCB_CPU
+	select VIRT_CPU_ACCOUNTING_GEN
+	select IRQ_WORK
+	select CPU_ISOLATION
+	help
+	 Adaptively try to shutdown the tick whenever possible, even when
+	 the CPU is running tasks. Typically this requires running a single
+	 task on the CPU. Chances for running tickless are maximized when
+	 the task mostly runs in userspace and has few kernel activity.
+
+	 You need to fill up the nohz_full boot parameter with the
+	 desired range of dynticks CPUs to use it. This is implemented at
+	 the expense of some overhead in user <-> kernel transitions:
+	 syscalls, exceptions and interrupts.
+
+	 By default, without passing the nohz_full parameter, this behaves just
+	 like NO_HZ_IDLE.
+
+	 If you're a distro say Y.
+
+endchoice
+
+config CONTEXT_TRACKING_USER
+	bool
+	depends on HAVE_CONTEXT_TRACKING_USER
+	select CONTEXT_TRACKING
+	help
+	  Track transitions between kernel and user on behalf of RCU and
+	  tickless cputime accounting. The former case relies on context
+	  tracking to enter/exit RCU extended quiescent states.
+
+config CONTEXT_TRACKING_USER_FORCE
+	bool "Force user context tracking"
+	depends on CONTEXT_TRACKING_USER
+	default y if !NO_HZ_FULL
+	help
+	  The major pre-requirement for full dynticks to work is to
+	  support the user context tracking subsystem. But there are also
+	  other dependencies to provide in order to make the full
+	  dynticks working.
+
+	  This option stands for testing when an arch implements the
+	  user context tracking backend but doesn't yet fulfill all the
+	  requirements to make the full dynticks feature working.
+	  Without the full dynticks, there is no way to test the support
+	  for user context tracking and the subsystems that rely on it: RCU
+	  userspace extended quiescent state and tickless cputime
+	  accounting. This option copes with the absence of the full
+	  dynticks subsystem by forcing the user context tracking on all
+	  CPUs in the system.
+
+	  Say Y only if you're working on the development of an
+	  architecture backend for the user context tracking.
+
+	  Say N otherwise, this option brings an overhead that you
+	  don't want in production.
+
+config NO_HZ
+	bool "Old Idle dynticks config"
+	help
+	  This is the old config entry that enables dynticks idle.
+	  We keep it around for a little while to enforce backward
+	  compatibility with older config files.
+
+config HIGH_RES_TIMERS
+	bool "High Resolution Timer Support"
+	select TICK_ONESHOT
+	help
+	  This option enables high resolution timer support. If your
+	  hardware is not capable then this option only increases
+	  the size of the kernel image.
+
+config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+	int "Clocksource watchdog maximum allowable skew (in μs)"
+	depends on CLOCKSOURCE_WATCHDOG
+	range 50 1000
+	default 125
+	help
+	  Specify the maximum amount of allowable watchdog skew in
+	  microseconds before reporting the clocksource to be unstable.
+	  The default is based on a half-second clocksource watchdog
+	  interval and NTP's maximum frequency drift of 500 parts
+	  per million.	If the clocksource is good enough for NTP,
+	  it is good enough for the clocksource watchdog!
+
+endmenu
+endif
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
new file mode 100644
index 0000000000..7e875e63ff
--- /dev/null
+++ b/kernel/time/Makefile
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y += time.o timer.o hrtimer.o
+obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o
+obj-y += timeconv.o timecounter.o alarmtimer.o
+
+ifeq ($(CONFIG_POSIX_TIMERS),y)
+ obj-y += posix-timers.o posix-cpu-timers.o posix-clock.o itimer.o
+else
+ obj-y += posix-stubs.o
+endif
+
+obj-$(CONFIG_GENERIC_CLOCKEVENTS)		+= clockevents.o tick-common.o
+ifeq ($(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST),y)
+ obj-y						+= tick-broadcast.o
+ obj-$(CONFIG_TICK_ONESHOT)			+= tick-broadcast-hrtimer.o
+endif
+obj-$(CONFIG_GENERIC_SCHED_CLOCK)		+= sched_clock.o
+obj-$(CONFIG_TICK_ONESHOT)			+= tick-oneshot.o tick-sched.o
+obj-$(CONFIG_LEGACY_TIMER_TICK)			+= tick-legacy.o
+obj-$(CONFIG_HAVE_GENERIC_VDSO)			+= vsyscall.o
+obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
+obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
+obj-$(CONFIG_TIME_NS)				+= namespace.o
+obj-$(CONFIG_TEST_CLOCKSOURCE_WATCHDOG)		+= clocksource-wdtest.o
+obj-$(CONFIG_TIME_KUNIT_TEST)			+= time_test.o
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
new file mode 100644
index 0000000000..8d9f13d847
--- /dev/null
+++ b/kernel/time/alarmtimer.c
@@ -0,0 +1,963 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Alarmtimer interface
+ *
+ * This interface provides a timer which is similar to hrtimers,
+ * but triggers a RTC alarm if the box is suspend.
+ *
+ * This interface is influenced by the Android RTC Alarm timer
+ * interface.
+ *
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * Author: John Stultz <john.stultz@linaro.org>
+ */
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/timerqueue.h>
+#include <linux/rtc.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/debug.h>
+#include <linux/alarmtimer.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/posix-timers.h>
+#include <linux/workqueue.h>
+#include <linux/freezer.h>
+#include <linux/compat.h>
+#include <linux/module.h>
+#include <linux/time_namespace.h>
+
+#include "posix-timers.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/alarmtimer.h>
+
+/**
+ * struct alarm_base - Alarm timer bases
+ * @lock:		Lock for syncrhonized access to the base
+ * @timerqueue:		Timerqueue head managing the list of events
+ * @get_ktime:		Function to read the time correlating to the base
+ * @get_timespec:	Function to read the namespace time correlating to the base
+ * @base_clockid:	clockid for the base
+ */
+static struct alarm_base {
+	spinlock_t		lock;
+	struct timerqueue_head	timerqueue;
+	ktime_t			(*get_ktime)(void);
+	void			(*get_timespec)(struct timespec64 *tp);
+	clockid_t		base_clockid;
+} alarm_bases[ALARM_NUMTYPE];
+
+#if defined(CONFIG_POSIX_TIMERS) || defined(CONFIG_RTC_CLASS)
+/* freezer information to handle clock_nanosleep triggered wakeups */
+static enum alarmtimer_type freezer_alarmtype;
+static ktime_t freezer_expires;
+static ktime_t freezer_delta;
+static DEFINE_SPINLOCK(freezer_delta_lock);
+#endif
+
+#ifdef CONFIG_RTC_CLASS
+/* rtc timer and device for setting alarm wakeups at suspend */
+static struct rtc_timer		rtctimer;
+static struct rtc_device	*rtcdev;
+static DEFINE_SPINLOCK(rtcdev_lock);
+
+/**
+ * alarmtimer_get_rtcdev - Return selected rtcdevice
+ *
+ * This function returns the rtc device to use for wakealarms.
+ */
+struct rtc_device *alarmtimer_get_rtcdev(void)
+{
+	unsigned long flags;
+	struct rtc_device *ret;
+
+	spin_lock_irqsave(&rtcdev_lock, flags);
+	ret = rtcdev;
+	spin_unlock_irqrestore(&rtcdev_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(alarmtimer_get_rtcdev);
+
+static int alarmtimer_rtc_add_device(struct device *dev)
+{
+	unsigned long flags;
+	struct rtc_device *rtc = to_rtc_device(dev);
+	struct platform_device *pdev;
+	int ret = 0;
+
+	if (rtcdev)
+		return -EBUSY;
+
+	if (!test_bit(RTC_FEATURE_ALARM, rtc->features))
+		return -1;
+	if (!device_may_wakeup(rtc->dev.parent))
+		return -1;
+
+	pdev = platform_device_register_data(dev, "alarmtimer",
+					     PLATFORM_DEVID_AUTO, NULL, 0);
+	if (!IS_ERR(pdev))
+		device_init_wakeup(&pdev->dev, true);
+
+	spin_lock_irqsave(&rtcdev_lock, flags);
+	if (!IS_ERR(pdev) && !rtcdev) {
+		if (!try_module_get(rtc->owner)) {
+			ret = -1;
+			goto unlock;
+		}
+
+		rtcdev = rtc;
+		/* hold a reference so it doesn't go away */
+		get_device(dev);
+		pdev = NULL;
+	} else {
+		ret = -1;
+	}
+unlock:
+	spin_unlock_irqrestore(&rtcdev_lock, flags);
+
+	platform_device_unregister(pdev);
+
+	return ret;
+}
+
+static inline void alarmtimer_rtc_timer_init(void)
+{
+	rtc_timer_init(&rtctimer, NULL, NULL);
+}
+
+static struct class_interface alarmtimer_rtc_interface = {
+	.add_dev = &alarmtimer_rtc_add_device,
+};
+
+static int alarmtimer_rtc_interface_setup(void)
+{
+	alarmtimer_rtc_interface.class = rtc_class;
+	return class_interface_register(&alarmtimer_rtc_interface);
+}
+static void alarmtimer_rtc_interface_remove(void)
+{
+	class_interface_unregister(&alarmtimer_rtc_interface);
+}
+#else
+static inline int alarmtimer_rtc_interface_setup(void) { return 0; }
+static inline void alarmtimer_rtc_interface_remove(void) { }
+static inline void alarmtimer_rtc_timer_init(void) { }
+#endif
+
+/**
+ * alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerqueue
+ * @base: pointer to the base where the timer is being run
+ * @alarm: pointer to alarm being enqueued.
+ *
+ * Adds alarm to a alarm_base timerqueue
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
+{
+	if (alarm->state & ALARMTIMER_STATE_ENQUEUED)
+		timerqueue_del(&base->timerqueue, &alarm->node);
+
+	timerqueue_add(&base->timerqueue, &alarm->node);
+	alarm->state |= ALARMTIMER_STATE_ENQUEUED;
+}
+
+/**
+ * alarmtimer_dequeue - Removes an alarm timer from an alarm_base timerqueue
+ * @base: pointer to the base where the timer is running
+ * @alarm: pointer to alarm being removed
+ *
+ * Removes alarm to a alarm_base timerqueue
+ *
+ * Must hold base->lock when calling.
+ */
+static void alarmtimer_dequeue(struct alarm_base *base, struct alarm *alarm)
+{
+	if (!(alarm->state & ALARMTIMER_STATE_ENQUEUED))
+		return;
+
+	timerqueue_del(&base->timerqueue, &alarm->node);
+	alarm->state &= ~ALARMTIMER_STATE_ENQUEUED;
+}
+
+
+/**
+ * alarmtimer_fired - Handles alarm hrtimer being fired.
+ * @timer: pointer to hrtimer being run
+ *
+ * When a alarm timer fires, this runs through the timerqueue to
+ * see which alarms expired, and runs those. If there are more alarm
+ * timers queued for the future, we set the hrtimer to fire when
+ * the next future alarm timer expires.
+ */
+static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
+{
+	struct alarm *alarm = container_of(timer, struct alarm, timer);
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	unsigned long flags;
+	int ret = HRTIMER_NORESTART;
+	int restart = ALARMTIMER_NORESTART;
+
+	spin_lock_irqsave(&base->lock, flags);
+	alarmtimer_dequeue(base, alarm);
+	spin_unlock_irqrestore(&base->lock, flags);
+
+	if (alarm->function)
+		restart = alarm->function(alarm, base->get_ktime());
+
+	spin_lock_irqsave(&base->lock, flags);
+	if (restart != ALARMTIMER_NORESTART) {
+		hrtimer_set_expires(&alarm->timer, alarm->node.expires);
+		alarmtimer_enqueue(base, alarm);
+		ret = HRTIMER_RESTART;
+	}
+	spin_unlock_irqrestore(&base->lock, flags);
+
+	trace_alarmtimer_fired(alarm, base->get_ktime());
+	return ret;
+
+}
+
+ktime_t alarm_expires_remaining(const struct alarm *alarm)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	return ktime_sub(alarm->node.expires, base->get_ktime());
+}
+EXPORT_SYMBOL_GPL(alarm_expires_remaining);
+
+#ifdef CONFIG_RTC_CLASS
+/**
+ * alarmtimer_suspend - Suspend time callback
+ * @dev: unused
+ *
+ * When we are going into suspend, we look through the bases
+ * to see which is the soonest timer to expire. We then
+ * set an rtc timer to fire that far into the future, which
+ * will wake us from suspend.
+ */
+static int alarmtimer_suspend(struct device *dev)
+{
+	ktime_t min, now, expires;
+	int i, ret, type;
+	struct rtc_device *rtc;
+	unsigned long flags;
+	struct rtc_time tm;
+
+	spin_lock_irqsave(&freezer_delta_lock, flags);
+	min = freezer_delta;
+	expires = freezer_expires;
+	type = freezer_alarmtype;
+	freezer_delta = 0;
+	spin_unlock_irqrestore(&freezer_delta_lock, flags);
+
+	rtc = alarmtimer_get_rtcdev();
+	/* If we have no rtcdev, just return */
+	if (!rtc)
+		return 0;
+
+	/* Find the soonest timer to expire*/
+	for (i = 0; i < ALARM_NUMTYPE; i++) {
+		struct alarm_base *base = &alarm_bases[i];
+		struct timerqueue_node *next;
+		ktime_t delta;
+
+		spin_lock_irqsave(&base->lock, flags);
+		next = timerqueue_getnext(&base->timerqueue);
+		spin_unlock_irqrestore(&base->lock, flags);
+		if (!next)
+			continue;
+		delta = ktime_sub(next->expires, base->get_ktime());
+		if (!min || (delta < min)) {
+			expires = next->expires;
+			min = delta;
+			type = i;
+		}
+	}
+	if (min == 0)
+		return 0;
+
+	if (ktime_to_ns(min) < 2 * NSEC_PER_SEC) {
+		pm_wakeup_event(dev, 2 * MSEC_PER_SEC);
+		return -EBUSY;
+	}
+
+	trace_alarmtimer_suspend(expires, type);
+
+	/* Setup an rtc timer to fire that far in the future */
+	rtc_timer_cancel(rtc, &rtctimer);
+	rtc_read_time(rtc, &tm);
+	now = rtc_tm_to_ktime(tm);
+	now = ktime_add(now, min);
+
+	/* Set alarm, if in the past reject suspend briefly to handle */
+	ret = rtc_timer_start(rtc, &rtctimer, now, 0);
+	if (ret < 0)
+		pm_wakeup_event(dev, MSEC_PER_SEC);
+	return ret;
+}
+
+static int alarmtimer_resume(struct device *dev)
+{
+	struct rtc_device *rtc;
+
+	rtc = alarmtimer_get_rtcdev();
+	if (rtc)
+		rtc_timer_cancel(rtc, &rtctimer);
+	return 0;
+}
+
+#else
+static int alarmtimer_suspend(struct device *dev)
+{
+	return 0;
+}
+
+static int alarmtimer_resume(struct device *dev)
+{
+	return 0;
+}
+#endif
+
+static void
+__alarm_init(struct alarm *alarm, enum alarmtimer_type type,
+	     enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
+{
+	timerqueue_init(&alarm->node);
+	alarm->timer.function = alarmtimer_fired;
+	alarm->function = function;
+	alarm->type = type;
+	alarm->state = ALARMTIMER_STATE_INACTIVE;
+}
+
+/**
+ * alarm_init - Initialize an alarm structure
+ * @alarm: ptr to alarm to be initialized
+ * @type: the type of the alarm
+ * @function: callback that is run when the alarm fires
+ */
+void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
+		enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
+{
+	hrtimer_init(&alarm->timer, alarm_bases[type].base_clockid,
+		     HRTIMER_MODE_ABS);
+	__alarm_init(alarm, type, function);
+}
+EXPORT_SYMBOL_GPL(alarm_init);
+
+/**
+ * alarm_start - Sets an absolute alarm to fire
+ * @alarm: ptr to alarm to set
+ * @start: time to run the alarm
+ */
+void alarm_start(struct alarm *alarm, ktime_t start)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	unsigned long flags;
+
+	spin_lock_irqsave(&base->lock, flags);
+	alarm->node.expires = start;
+	alarmtimer_enqueue(base, alarm);
+	hrtimer_start(&alarm->timer, alarm->node.expires, HRTIMER_MODE_ABS);
+	spin_unlock_irqrestore(&base->lock, flags);
+
+	trace_alarmtimer_start(alarm, base->get_ktime());
+}
+EXPORT_SYMBOL_GPL(alarm_start);
+
+/**
+ * alarm_start_relative - Sets a relative alarm to fire
+ * @alarm: ptr to alarm to set
+ * @start: time relative to now to run the alarm
+ */
+void alarm_start_relative(struct alarm *alarm, ktime_t start)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+
+	start = ktime_add_safe(start, base->get_ktime());
+	alarm_start(alarm, start);
+}
+EXPORT_SYMBOL_GPL(alarm_start_relative);
+
+void alarm_restart(struct alarm *alarm)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	unsigned long flags;
+
+	spin_lock_irqsave(&base->lock, flags);
+	hrtimer_set_expires(&alarm->timer, alarm->node.expires);
+	hrtimer_restart(&alarm->timer);
+	alarmtimer_enqueue(base, alarm);
+	spin_unlock_irqrestore(&base->lock, flags);
+}
+EXPORT_SYMBOL_GPL(alarm_restart);
+
+/**
+ * alarm_try_to_cancel - Tries to cancel an alarm timer
+ * @alarm: ptr to alarm to be canceled
+ *
+ * Returns 1 if the timer was canceled, 0 if it was not running,
+ * and -1 if the callback was running
+ */
+int alarm_try_to_cancel(struct alarm *alarm)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&base->lock, flags);
+	ret = hrtimer_try_to_cancel(&alarm->timer);
+	if (ret >= 0)
+		alarmtimer_dequeue(base, alarm);
+	spin_unlock_irqrestore(&base->lock, flags);
+
+	trace_alarmtimer_cancel(alarm, base->get_ktime());
+	return ret;
+}
+EXPORT_SYMBOL_GPL(alarm_try_to_cancel);
+
+
+/**
+ * alarm_cancel - Spins trying to cancel an alarm timer until it is done
+ * @alarm: ptr to alarm to be canceled
+ *
+ * Returns 1 if the timer was canceled, 0 if it was not active.
+ */
+int alarm_cancel(struct alarm *alarm)
+{
+	for (;;) {
+		int ret = alarm_try_to_cancel(alarm);
+		if (ret >= 0)
+			return ret;
+		hrtimer_cancel_wait_running(&alarm->timer);
+	}
+}
+EXPORT_SYMBOL_GPL(alarm_cancel);
+
+
+u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)
+{
+	u64 overrun = 1;
+	ktime_t delta;
+
+	delta = ktime_sub(now, alarm->node.expires);
+
+	if (delta < 0)
+		return 0;
+
+	if (unlikely(delta >= interval)) {
+		s64 incr = ktime_to_ns(interval);
+
+		overrun = ktime_divns(delta, incr);
+
+		alarm->node.expires = ktime_add_ns(alarm->node.expires,
+							incr*overrun);
+
+		if (alarm->node.expires > now)
+			return overrun;
+		/*
+		 * This (and the ktime_add() below) is the
+		 * correction for exact:
+		 */
+		overrun++;
+	}
+
+	alarm->node.expires = ktime_add_safe(alarm->node.expires, interval);
+	return overrun;
+}
+EXPORT_SYMBOL_GPL(alarm_forward);
+
+static u64 __alarm_forward_now(struct alarm *alarm, ktime_t interval, bool throttle)
+{
+	struct alarm_base *base = &alarm_bases[alarm->type];
+	ktime_t now = base->get_ktime();
+
+	if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && throttle) {
+		/*
+		 * Same issue as with posix_timer_fn(). Timers which are
+		 * periodic but the signal is ignored can starve the system
+		 * with a very small interval. The real fix which was
+		 * promised in the context of posix_timer_fn() never
+		 * materialized, but someone should really work on it.
+		 *
+		 * To prevent DOS fake @now to be 1 jiffie out which keeps
+		 * the overrun accounting correct but creates an
+		 * inconsistency vs. timer_gettime(2).
+		 */
+		ktime_t kj = NSEC_PER_SEC / HZ;
+
+		if (interval < kj)
+			now = ktime_add(now, kj);
+	}
+
+	return alarm_forward(alarm, now, interval);
+}
+
+u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
+{
+	return __alarm_forward_now(alarm, interval, false);
+}
+EXPORT_SYMBOL_GPL(alarm_forward_now);
+
+#ifdef CONFIG_POSIX_TIMERS
+
+static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
+{
+	struct alarm_base *base;
+	unsigned long flags;
+	ktime_t delta;
+
+	switch(type) {
+	case ALARM_REALTIME:
+		base = &alarm_bases[ALARM_REALTIME];
+		type = ALARM_REALTIME_FREEZER;
+		break;
+	case ALARM_BOOTTIME:
+		base = &alarm_bases[ALARM_BOOTTIME];
+		type = ALARM_BOOTTIME_FREEZER;
+		break;
+	default:
+		WARN_ONCE(1, "Invalid alarm type: %d\n", type);
+		return;
+	}
+
+	delta = ktime_sub(absexp, base->get_ktime());
+
+	spin_lock_irqsave(&freezer_delta_lock, flags);
+	if (!freezer_delta || (delta < freezer_delta)) {
+		freezer_delta = delta;
+		freezer_expires = absexp;
+		freezer_alarmtype = type;
+	}
+	spin_unlock_irqrestore(&freezer_delta_lock, flags);
+}
+
+/**
+ * clock2alarm - helper that converts from clockid to alarmtypes
+ * @clockid: clockid.
+ */
+static enum alarmtimer_type clock2alarm(clockid_t clockid)
+{
+	if (clockid == CLOCK_REALTIME_ALARM)
+		return ALARM_REALTIME;
+	if (clockid == CLOCK_BOOTTIME_ALARM)
+		return ALARM_BOOTTIME;
+	return -1;
+}
+
+/**
+ * alarm_handle_timer - Callback for posix timers
+ * @alarm: alarm that fired
+ * @now: time at the timer expiration
+ *
+ * Posix timer callback for expired alarm timers.
+ *
+ * Return: whether the timer is to be restarted
+ */
+static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
+							ktime_t now)
+{
+	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
+					    it.alarm.alarmtimer);
+	enum alarmtimer_restart result = ALARMTIMER_NORESTART;
+	unsigned long flags;
+	int si_private = 0;
+
+	spin_lock_irqsave(&ptr->it_lock, flags);
+
+	ptr->it_active = 0;
+	if (ptr->it_interval)
+		si_private = ++ptr->it_requeue_pending;
+
+	if (posix_timer_event(ptr, si_private) && ptr->it_interval) {
+		/*
+		 * Handle ignored signals and rearm the timer. This will go
+		 * away once we handle ignored signals proper. Ensure that
+		 * small intervals cannot starve the system.
+		 */
+		ptr->it_overrun += __alarm_forward_now(alarm, ptr->it_interval, true);
+		++ptr->it_requeue_pending;
+		ptr->it_active = 1;
+		result = ALARMTIMER_RESTART;
+	}
+	spin_unlock_irqrestore(&ptr->it_lock, flags);
+
+	return result;
+}
+
+/**
+ * alarm_timer_rearm - Posix timer callback for rearming timer
+ * @timr:	Pointer to the posixtimer data struct
+ */
+static void alarm_timer_rearm(struct k_itimer *timr)
+{
+	struct alarm *alarm = &timr->it.alarm.alarmtimer;
+
+	timr->it_overrun += alarm_forward_now(alarm, timr->it_interval);
+	alarm_start(alarm, alarm->node.expires);
+}
+
+/**
+ * alarm_timer_forward - Posix timer callback for forwarding timer
+ * @timr:	Pointer to the posixtimer data struct
+ * @now:	Current time to forward the timer against
+ */
+static s64 alarm_timer_forward(struct k_itimer *timr, ktime_t now)
+{
+	struct alarm *alarm = &timr->it.alarm.alarmtimer;
+
+	return alarm_forward(alarm, timr->it_interval, now);
+}
+
+/**
+ * alarm_timer_remaining - Posix timer callback to retrieve remaining time
+ * @timr:	Pointer to the posixtimer data struct
+ * @now:	Current time to calculate against
+ */
+static ktime_t alarm_timer_remaining(struct k_itimer *timr, ktime_t now)
+{
+	struct alarm *alarm = &timr->it.alarm.alarmtimer;
+
+	return ktime_sub(alarm->node.expires, now);
+}
+
+/**
+ * alarm_timer_try_to_cancel - Posix timer callback to cancel a timer
+ * @timr:	Pointer to the posixtimer data struct
+ */
+static int alarm_timer_try_to_cancel(struct k_itimer *timr)
+{
+	return alarm_try_to_cancel(&timr->it.alarm.alarmtimer);
+}
+
+/**
+ * alarm_timer_wait_running - Posix timer callback to wait for a timer
+ * @timr:	Pointer to the posixtimer data struct
+ *
+ * Called from the core code when timer cancel detected that the callback
+ * is running. @timr is unlocked and rcu read lock is held to prevent it
+ * from being freed.
+ */
+static void alarm_timer_wait_running(struct k_itimer *timr)
+{
+	hrtimer_cancel_wait_running(&timr->it.alarm.alarmtimer.timer);
+}
+
+/**
+ * alarm_timer_arm - Posix timer callback to arm a timer
+ * @timr:	Pointer to the posixtimer data struct
+ * @expires:	The new expiry time
+ * @absolute:	Expiry value is absolute time
+ * @sigev_none:	Posix timer does not deliver signals
+ */
+static void alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
+			    bool absolute, bool sigev_none)
+{
+	struct alarm *alarm = &timr->it.alarm.alarmtimer;
+	struct alarm_base *base = &alarm_bases[alarm->type];
+
+	if (!absolute)
+		expires = ktime_add_safe(expires, base->get_ktime());
+	if (sigev_none)
+		alarm->node.expires = expires;
+	else
+		alarm_start(&timr->it.alarm.alarmtimer, expires);
+}
+
+/**
+ * alarm_clock_getres - posix getres interface
+ * @which_clock: clockid
+ * @tp: timespec to fill
+ *
+ * Returns the granularity of underlying alarm base clock
+ */
+static int alarm_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
+{
+	if (!alarmtimer_get_rtcdev())
+		return -EINVAL;
+
+	tp->tv_sec = 0;
+	tp->tv_nsec = hrtimer_resolution;
+	return 0;
+}
+
+/**
+ * alarm_clock_get_timespec - posix clock_get_timespec interface
+ * @which_clock: clockid
+ * @tp: timespec to fill.
+ *
+ * Provides the underlying alarm base time in a tasks time namespace.
+ */
+static int alarm_clock_get_timespec(clockid_t which_clock, struct timespec64 *tp)
+{
+	struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
+
+	if (!alarmtimer_get_rtcdev())
+		return -EINVAL;
+
+	base->get_timespec(tp);
+
+	return 0;
+}
+
+/**
+ * alarm_clock_get_ktime - posix clock_get_ktime interface
+ * @which_clock: clockid
+ *
+ * Provides the underlying alarm base time in the root namespace.
+ */
+static ktime_t alarm_clock_get_ktime(clockid_t which_clock)
+{
+	struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
+
+	if (!alarmtimer_get_rtcdev())
+		return -EINVAL;
+
+	return base->get_ktime();
+}
+
+/**
+ * alarm_timer_create - posix timer_create interface
+ * @new_timer: k_itimer pointer to manage
+ *
+ * Initializes the k_itimer structure.
+ */
+static int alarm_timer_create(struct k_itimer *new_timer)
+{
+	enum  alarmtimer_type type;
+
+	if (!alarmtimer_get_rtcdev())
+		return -EOPNOTSUPP;
+
+	if (!capable(CAP_WAKE_ALARM))
+		return -EPERM;
+
+	type = clock2alarm(new_timer->it_clock);
+	alarm_init(&new_timer->it.alarm.alarmtimer, type, alarm_handle_timer);
+	return 0;
+}
+
+/**
+ * alarmtimer_nsleep_wakeup - Wakeup function for alarm_timer_nsleep
+ * @alarm: ptr to alarm that fired
+ * @now: time at the timer expiration
+ *
+ * Wakes up the task that set the alarmtimer
+ *
+ * Return: ALARMTIMER_NORESTART
+ */
+static enum alarmtimer_restart alarmtimer_nsleep_wakeup(struct alarm *alarm,
+								ktime_t now)
+{
+	struct task_struct *task = alarm->data;
+
+	alarm->data = NULL;
+	if (task)
+		wake_up_process(task);
+	return ALARMTIMER_NORESTART;
+}
+
+/**
+ * alarmtimer_do_nsleep - Internal alarmtimer nsleep implementation
+ * @alarm: ptr to alarmtimer
+ * @absexp: absolute expiration time
+ * @type: alarm type (BOOTTIME/REALTIME).
+ *
+ * Sets the alarm timer and sleeps until it is fired or interrupted.
+ */
+static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp,
+				enum alarmtimer_type type)
+{
+	struct restart_block *restart;
+	alarm->data = (void *)current;
+	do {
+		set_current_state(TASK_INTERRUPTIBLE);
+		alarm_start(alarm, absexp);
+		if (likely(alarm->data))
+			schedule();
+
+		alarm_cancel(alarm);
+	} while (alarm->data && !signal_pending(current));
+
+	__set_current_state(TASK_RUNNING);
+
+	destroy_hrtimer_on_stack(&alarm->timer);
+
+	if (!alarm->data)
+		return 0;
+
+	if (freezing(current))
+		alarmtimer_freezerset(absexp, type);
+	restart = &current->restart_block;
+	if (restart->nanosleep.type != TT_NONE) {
+		struct timespec64 rmt;
+		ktime_t rem;
+
+		rem = ktime_sub(absexp, alarm_bases[type].get_ktime());
+
+		if (rem <= 0)
+			return 0;
+		rmt = ktime_to_timespec64(rem);
+
+		return nanosleep_copyout(restart, &rmt);
+	}
+	return -ERESTART_RESTARTBLOCK;
+}
+
+static void
+alarm_init_on_stack(struct alarm *alarm, enum alarmtimer_type type,
+		    enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
+{
+	hrtimer_init_on_stack(&alarm->timer, alarm_bases[type].base_clockid,
+			      HRTIMER_MODE_ABS);
+	__alarm_init(alarm, type, function);
+}
+
+/**
+ * alarm_timer_nsleep_restart - restartblock alarmtimer nsleep
+ * @restart: ptr to restart block
+ *
+ * Handles restarted clock_nanosleep calls
+ */
+static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
+{
+	enum  alarmtimer_type type = restart->nanosleep.clockid;
+	ktime_t exp = restart->nanosleep.expires;
+	struct alarm alarm;
+
+	alarm_init_on_stack(&alarm, type, alarmtimer_nsleep_wakeup);
+
+	return alarmtimer_do_nsleep(&alarm, exp, type);
+}
+
+/**
+ * alarm_timer_nsleep - alarmtimer nanosleep
+ * @which_clock: clockid
+ * @flags: determines abstime or relative
+ * @tsreq: requested sleep time (abs or rel)
+ *
+ * Handles clock_nanosleep calls against _ALARM clockids
+ */
+static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
+			      const struct timespec64 *tsreq)
+{
+	enum  alarmtimer_type type = clock2alarm(which_clock);
+	struct restart_block *restart = &current->restart_block;
+	struct alarm alarm;
+	ktime_t exp;
+	int ret;
+
+	if (!alarmtimer_get_rtcdev())
+		return -EOPNOTSUPP;
+
+	if (flags & ~TIMER_ABSTIME)
+		return -EINVAL;
+
+	if (!capable(CAP_WAKE_ALARM))
+		return -EPERM;
+
+	alarm_init_on_stack(&alarm, type, alarmtimer_nsleep_wakeup);
+
+	exp = timespec64_to_ktime(*tsreq);
+	/* Convert (if necessary) to absolute time */
+	if (flags != TIMER_ABSTIME) {
+		ktime_t now = alarm_bases[type].get_ktime();
+
+		exp = ktime_add_safe(now, exp);
+	} else {
+		exp = timens_ktime_to_host(which_clock, exp);
+	}
+
+	ret = alarmtimer_do_nsleep(&alarm, exp, type);
+	if (ret != -ERESTART_RESTARTBLOCK)
+		return ret;
+
+	/* abs timers don't set remaining time or restart */
+	if (flags == TIMER_ABSTIME)
+		return -ERESTARTNOHAND;
+
+	restart->nanosleep.clockid = type;
+	restart->nanosleep.expires = exp;
+	set_restart_fn(restart, alarm_timer_nsleep_restart);
+	return ret;
+}
+
+const struct k_clock alarm_clock = {
+	.clock_getres		= alarm_clock_getres,
+	.clock_get_ktime	= alarm_clock_get_ktime,
+	.clock_get_timespec	= alarm_clock_get_timespec,
+	.timer_create		= alarm_timer_create,
+	.timer_set		= common_timer_set,
+	.timer_del		= common_timer_del,
+	.timer_get		= common_timer_get,
+	.timer_arm		= alarm_timer_arm,
+	.timer_rearm		= alarm_timer_rearm,
+	.timer_forward		= alarm_timer_forward,
+	.timer_remaining	= alarm_timer_remaining,
+	.timer_try_to_cancel	= alarm_timer_try_to_cancel,
+	.timer_wait_running	= alarm_timer_wait_running,
+	.nsleep			= alarm_timer_nsleep,
+};
+#endif /* CONFIG_POSIX_TIMERS */
+
+
+/* Suspend hook structures */
+static const struct dev_pm_ops alarmtimer_pm_ops = {
+	.suspend = alarmtimer_suspend,
+	.resume = alarmtimer_resume,
+};
+
+static struct platform_driver alarmtimer_driver = {
+	.driver = {
+		.name = "alarmtimer",
+		.pm = &alarmtimer_pm_ops,
+	}
+};
+
+static void get_boottime_timespec(struct timespec64 *tp)
+{
+	ktime_get_boottime_ts64(tp);
+	timens_add_boottime(tp);
+}
+
+/**
+ * alarmtimer_init - Initialize alarm timer code
+ *
+ * This function initializes the alarm bases and registers
+ * the posix clock ids.
+ */
+static int __init alarmtimer_init(void)
+{
+	int error;
+	int i;
+
+	alarmtimer_rtc_timer_init();
+
+	/* Initialize alarm bases */
+	alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
+	alarm_bases[ALARM_REALTIME].get_ktime = &ktime_get_real;
+	alarm_bases[ALARM_REALTIME].get_timespec = ktime_get_real_ts64;
+	alarm_bases[ALARM_BOOTTIME].base_clockid = CLOCK_BOOTTIME;
+	alarm_bases[ALARM_BOOTTIME].get_ktime = &ktime_get_boottime;
+	alarm_bases[ALARM_BOOTTIME].get_timespec = get_boottime_timespec;
+	for (i = 0; i < ALARM_NUMTYPE; i++) {
+		timerqueue_init_head(&alarm_bases[i].timerqueue);
+		spin_lock_init(&alarm_bases[i].lock);
+	}
+
+	error = alarmtimer_rtc_interface_setup();
+	if (error)
+		return error;
+
+	error = platform_driver_register(&alarmtimer_driver);
+	if (error)
+		goto out_if;
+
+	return 0;
+out_if:
+	alarmtimer_rtc_interface_remove();
+	return error;
+}
+device_initcall(alarmtimer_init);
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
new file mode 100644
index 0000000000..960143b183
--- /dev/null
+++ b/kernel/time/clockevents.c
@@ -0,0 +1,778 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file contains functions which manage clock event devices.
+ *
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
+ */
+
+#include <linux/clockchips.h>
+#include <linux/hrtimer.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/smp.h>
+#include <linux/device.h>
+
+#include "tick-internal.h"
+
+/* The registered clock event devices */
+static LIST_HEAD(clockevent_devices);
+static LIST_HEAD(clockevents_released);
+/* Protection for the above */
+static DEFINE_RAW_SPINLOCK(clockevents_lock);
+/* Protection for unbind operations */
+static DEFINE_MUTEX(clockevents_mutex);
+
+struct ce_unbind {
+	struct clock_event_device *ce;
+	int res;
+};
+
+static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
+			bool ismax)
+{
+	u64 clc = (u64) latch << evt->shift;
+	u64 rnd;
+
+	if (WARN_ON(!evt->mult))
+		evt->mult = 1;
+	rnd = (u64) evt->mult - 1;
+
+	/*
+	 * Upper bound sanity check. If the backwards conversion is
+	 * not equal latch, we know that the above shift overflowed.
+	 */
+	if ((clc >> evt->shift) != (u64)latch)
+		clc = ~0ULL;
+
+	/*
+	 * Scaled math oddities:
+	 *
+	 * For mult <= (1 << shift) we can safely add mult - 1 to
+	 * prevent integer rounding loss. So the backwards conversion
+	 * from nsec to device ticks will be correct.
+	 *
+	 * For mult > (1 << shift), i.e. device frequency is > 1GHz we
+	 * need to be careful. Adding mult - 1 will result in a value
+	 * which when converted back to device ticks can be larger
+	 * than latch by up to (mult - 1) >> shift. For the min_delta
+	 * calculation we still want to apply this in order to stay
+	 * above the minimum device ticks limit. For the upper limit
+	 * we would end up with a latch value larger than the upper
+	 * limit of the device, so we omit the add to stay below the
+	 * device upper boundary.
+	 *
+	 * Also omit the add if it would overflow the u64 boundary.
+	 */
+	if ((~0ULL - clc > rnd) &&
+	    (!ismax || evt->mult <= (1ULL << evt->shift)))
+		clc += rnd;
+
+	do_div(clc, evt->mult);
+
+	/* Deltas less than 1usec are pointless noise */
+	return clc > 1000 ? clc : 1000;
+}
+
+/**
+ * clockevent_delta2ns - Convert a latch value (device ticks) to nanoseconds
+ * @latch:	value to convert
+ * @evt:	pointer to clock event device descriptor
+ *
+ * Math helper, returns latch value converted to nanoseconds (bound checked)
+ */
+u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
+{
+	return cev_delta2ns(latch, evt, false);
+}
+EXPORT_SYMBOL_GPL(clockevent_delta2ns);
+
+static int __clockevents_switch_state(struct clock_event_device *dev,
+				      enum clock_event_state state)
+{
+	if (dev->features & CLOCK_EVT_FEAT_DUMMY)
+		return 0;
+
+	/* Transition with new state-specific callbacks */
+	switch (state) {
+	case CLOCK_EVT_STATE_DETACHED:
+		/* The clockevent device is getting replaced. Shut it down. */
+
+	case CLOCK_EVT_STATE_SHUTDOWN:
+		if (dev->set_state_shutdown)
+			return dev->set_state_shutdown(dev);
+		return 0;
+
+	case CLOCK_EVT_STATE_PERIODIC:
+		/* Core internal bug */
+		if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
+			return -ENOSYS;
+		if (dev->set_state_periodic)
+			return dev->set_state_periodic(dev);
+		return 0;
+
+	case CLOCK_EVT_STATE_ONESHOT:
+		/* Core internal bug */
+		if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+			return -ENOSYS;
+		if (dev->set_state_oneshot)
+			return dev->set_state_oneshot(dev);
+		return 0;
+
+	case CLOCK_EVT_STATE_ONESHOT_STOPPED:
+		/* Core internal bug */
+		if (WARN_ONCE(!clockevent_state_oneshot(dev),
+			      "Current state: %d\n",
+			      clockevent_get_state(dev)))
+			return -EINVAL;
+
+		if (dev->set_state_oneshot_stopped)
+			return dev->set_state_oneshot_stopped(dev);
+		else
+			return -ENOSYS;
+
+	default:
+		return -ENOSYS;
+	}
+}
+
+/**
+ * clockevents_switch_state - set the operating state of a clock event device
+ * @dev:	device to modify
+ * @state:	new state
+ *
+ * Must be called with interrupts disabled !
+ */
+void clockevents_switch_state(struct clock_event_device *dev,
+			      enum clock_event_state state)
+{
+	if (clockevent_get_state(dev) != state) {
+		if (__clockevents_switch_state(dev, state))
+			return;
+
+		clockevent_set_state(dev, state);
+
+		/*
+		 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
+		 * on it, so fix it up and emit a warning:
+		 */
+		if (clockevent_state_oneshot(dev)) {
+			if (WARN_ON(!dev->mult))
+				dev->mult = 1;
+		}
+	}
+}
+
+/**
+ * clockevents_shutdown - shutdown the device and clear next_event
+ * @dev:	device to shutdown
+ */
+void clockevents_shutdown(struct clock_event_device *dev)
+{
+	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
+	dev->next_event = KTIME_MAX;
+}
+
+/**
+ * clockevents_tick_resume -	Resume the tick device before using it again
+ * @dev:			device to resume
+ */
+int clockevents_tick_resume(struct clock_event_device *dev)
+{
+	int ret = 0;
+
+	if (dev->tick_resume)
+		ret = dev->tick_resume(dev);
+
+	return ret;
+}
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
+
+/* Limit min_delta to a jiffie */
+#define MIN_DELTA_LIMIT		(NSEC_PER_SEC / HZ)
+
+/**
+ * clockevents_increase_min_delta - raise minimum delta of a clock event device
+ * @dev:       device to increase the minimum delta
+ *
+ * Returns 0 on success, -ETIME when the minimum delta reached the limit.
+ */
+static int clockevents_increase_min_delta(struct clock_event_device *dev)
+{
+	/* Nothing to do if we already reached the limit */
+	if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
+		printk_deferred(KERN_WARNING
+				"CE: Reprogramming failure. Giving up\n");
+		dev->next_event = KTIME_MAX;
+		return -ETIME;
+	}
+
+	if (dev->min_delta_ns < 5000)
+		dev->min_delta_ns = 5000;
+	else
+		dev->min_delta_ns += dev->min_delta_ns >> 1;
+
+	if (dev->min_delta_ns > MIN_DELTA_LIMIT)
+		dev->min_delta_ns = MIN_DELTA_LIMIT;
+
+	printk_deferred(KERN_WARNING
+			"CE: %s increased min_delta_ns to %llu nsec\n",
+			dev->name ? dev->name : "?",
+			(unsigned long long) dev->min_delta_ns);
+	return 0;
+}
+
+/**
+ * clockevents_program_min_delta - Set clock event device to the minimum delay.
+ * @dev:	device to program
+ *
+ * Returns 0 on success, -ETIME when the retry loop failed.
+ */
+static int clockevents_program_min_delta(struct clock_event_device *dev)
+{
+	unsigned long long clc;
+	int64_t delta;
+	int i;
+
+	for (i = 0;;) {
+		delta = dev->min_delta_ns;
+		dev->next_event = ktime_add_ns(ktime_get(), delta);
+
+		if (clockevent_state_shutdown(dev))
+			return 0;
+
+		dev->retries++;
+		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+		if (dev->set_next_event((unsigned long) clc, dev) == 0)
+			return 0;
+
+		if (++i > 2) {
+			/*
+			 * We tried 3 times to program the device with the
+			 * given min_delta_ns. Try to increase the minimum
+			 * delta, if that fails as well get out of here.
+			 */
+			if (clockevents_increase_min_delta(dev))
+				return -ETIME;
+			i = 0;
+		}
+	}
+}
+
+#else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
+
+/**
+ * clockevents_program_min_delta - Set clock event device to the minimum delay.
+ * @dev:	device to program
+ *
+ * Returns 0 on success, -ETIME when the retry loop failed.
+ */
+static int clockevents_program_min_delta(struct clock_event_device *dev)
+{
+	unsigned long long clc;
+	int64_t delta = 0;
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		delta += dev->min_delta_ns;
+		dev->next_event = ktime_add_ns(ktime_get(), delta);
+
+		if (clockevent_state_shutdown(dev))
+			return 0;
+
+		dev->retries++;
+		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+		if (dev->set_next_event((unsigned long) clc, dev) == 0)
+			return 0;
+	}
+	return -ETIME;
+}
+
+#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
+
+/**
+ * clockevents_program_event - Reprogram the clock event device.
+ * @dev:	device to program
+ * @expires:	absolute expiry time (monotonic clock)
+ * @force:	program minimum delay if expires can not be set
+ *
+ * Returns 0 on success, -ETIME when the event is in the past.
+ */
+int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
+			      bool force)
+{
+	unsigned long long clc;
+	int64_t delta;
+	int rc;
+
+	if (WARN_ON_ONCE(expires < 0))
+		return -ETIME;
+
+	dev->next_event = expires;
+
+	if (clockevent_state_shutdown(dev))
+		return 0;
+
+	/* We must be in ONESHOT state here */
+	WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
+		  clockevent_get_state(dev));
+
+	/* Shortcut for clockevent devices that can deal with ktime. */
+	if (dev->features & CLOCK_EVT_FEAT_KTIME)
+		return dev->set_next_ktime(expires, dev);
+
+	delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
+	if (delta <= 0)
+		return force ? clockevents_program_min_delta(dev) : -ETIME;
+
+	delta = min(delta, (int64_t) dev->max_delta_ns);
+	delta = max(delta, (int64_t) dev->min_delta_ns);
+
+	clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
+	rc = dev->set_next_event((unsigned long) clc, dev);
+
+	return (rc && force) ? clockevents_program_min_delta(dev) : rc;
+}
+
+/*
+ * Called after a notify add to make devices available which were
+ * released from the notifier call.
+ */
+static void clockevents_notify_released(void)
+{
+	struct clock_event_device *dev;
+
+	while (!list_empty(&clockevents_released)) {
+		dev = list_entry(clockevents_released.next,
+				 struct clock_event_device, list);
+		list_move(&dev->list, &clockevent_devices);
+		tick_check_new_device(dev);
+	}
+}
+
+/*
+ * Try to install a replacement clock event device
+ */
+static int clockevents_replace(struct clock_event_device *ced)
+{
+	struct clock_event_device *dev, *newdev = NULL;
+
+	list_for_each_entry(dev, &clockevent_devices, list) {
+		if (dev == ced || !clockevent_state_detached(dev))
+			continue;
+
+		if (!tick_check_replacement(newdev, dev))
+			continue;
+
+		if (!try_module_get(dev->owner))
+			continue;
+
+		if (newdev)
+			module_put(newdev->owner);
+		newdev = dev;
+	}
+	if (newdev) {
+		tick_install_replacement(newdev);
+		list_del_init(&ced->list);
+	}
+	return newdev ? 0 : -EBUSY;
+}
+
+/*
+ * Called with clockevents_mutex and clockevents_lock held
+ */
+static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
+{
+	/* Fast track. Device is unused */
+	if (clockevent_state_detached(ced)) {
+		list_del_init(&ced->list);
+		return 0;
+	}
+
+	return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
+}
+
+/*
+ * SMP function call to unbind a device
+ */
+static void __clockevents_unbind(void *arg)
+{
+	struct ce_unbind *cu = arg;
+	int res;
+
+	raw_spin_lock(&clockevents_lock);
+	res = __clockevents_try_unbind(cu->ce, smp_processor_id());
+	if (res == -EAGAIN)
+		res = clockevents_replace(cu->ce);
+	cu->res = res;
+	raw_spin_unlock(&clockevents_lock);
+}
+
+/*
+ * Issues smp function call to unbind a per cpu device. Called with
+ * clockevents_mutex held.
+ */
+static int clockevents_unbind(struct clock_event_device *ced, int cpu)
+{
+	struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
+
+	smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
+	return cu.res;
+}
+
+/*
+ * Unbind a clockevents device.
+ */
+int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
+{
+	int ret;
+
+	mutex_lock(&clockevents_mutex);
+	ret = clockevents_unbind(ced, cpu);
+	mutex_unlock(&clockevents_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(clockevents_unbind_device);
+
+/**
+ * clockevents_register_device - register a clock event device
+ * @dev:	device to register
+ */
+void clockevents_register_device(struct clock_event_device *dev)
+{
+	unsigned long flags;
+
+	/* Initialize state to DETACHED */
+	clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
+
+	if (!dev->cpumask) {
+		WARN_ON(num_possible_cpus() > 1);
+		dev->cpumask = cpumask_of(smp_processor_id());
+	}
+
+	if (dev->cpumask == cpu_all_mask) {
+		WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
+		     dev->name);
+		dev->cpumask = cpu_possible_mask;
+	}
+
+	raw_spin_lock_irqsave(&clockevents_lock, flags);
+
+	list_add(&dev->list, &clockevent_devices);
+	tick_check_new_device(dev);
+	clockevents_notify_released();
+
+	raw_spin_unlock_irqrestore(&clockevents_lock, flags);
+}
+EXPORT_SYMBOL_GPL(clockevents_register_device);
+
+static void clockevents_config(struct clock_event_device *dev, u32 freq)
+{
+	u64 sec;
+
+	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return;
+
+	/*
+	 * Calculate the maximum number of seconds we can sleep. Limit
+	 * to 10 minutes for hardware which can program more than
+	 * 32bit ticks so we still get reasonable conversion values.
+	 */
+	sec = dev->max_delta_ticks;
+	do_div(sec, freq);
+	if (!sec)
+		sec = 1;
+	else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
+		sec = 600;
+
+	clockevents_calc_mult_shift(dev, freq, sec);
+	dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
+	dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
+}
+
+/**
+ * clockevents_config_and_register - Configure and register a clock event device
+ * @dev:	device to register
+ * @freq:	The clock frequency
+ * @min_delta:	The minimum clock ticks to program in oneshot mode
+ * @max_delta:	The maximum clock ticks to program in oneshot mode
+ *
+ * min/max_delta can be 0 for devices which do not support oneshot mode.
+ */
+void clockevents_config_and_register(struct clock_event_device *dev,
+				     u32 freq, unsigned long min_delta,
+				     unsigned long max_delta)
+{
+	dev->min_delta_ticks = min_delta;
+	dev->max_delta_ticks = max_delta;
+	clockevents_config(dev, freq);
+	clockevents_register_device(dev);
+}
+EXPORT_SYMBOL_GPL(clockevents_config_and_register);
+
+int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
+{
+	clockevents_config(dev, freq);
+
+	if (clockevent_state_oneshot(dev))
+		return clockevents_program_event(dev, dev->next_event, false);
+
+	if (clockevent_state_periodic(dev))
+		return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
+
+	return 0;
+}
+
+/**
+ * clockevents_update_freq - Update frequency and reprogram a clock event device.
+ * @dev:	device to modify
+ * @freq:	new device frequency
+ *
+ * Reconfigure and reprogram a clock event device in oneshot
+ * mode. Must be called on the cpu for which the device delivers per
+ * cpu timer events. If called for the broadcast device the core takes
+ * care of serialization.
+ *
+ * Returns 0 on success, -ETIME when the event is in the past.
+ */
+int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
+{
+	unsigned long flags;
+	int ret;
+
+	local_irq_save(flags);
+	ret = tick_broadcast_update_freq(dev, freq);
+	if (ret == -ENODEV)
+		ret = __clockevents_update_freq(dev, freq);
+	local_irq_restore(flags);
+	return ret;
+}
+
+/*
+ * Noop handler when we shut down an event device
+ */
+void clockevents_handle_noop(struct clock_event_device *dev)
+{
+}
+
+/**
+ * clockevents_exchange_device - release and request clock devices
+ * @old:	device to release (can be NULL)
+ * @new:	device to request (can be NULL)
+ *
+ * Called from various tick functions with clockevents_lock held and
+ * interrupts disabled.
+ */
+void clockevents_exchange_device(struct clock_event_device *old,
+				 struct clock_event_device *new)
+{
+	/*
+	 * Caller releases a clock event device. We queue it into the
+	 * released list and do a notify add later.
+	 */
+	if (old) {
+		module_put(old->owner);
+		clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
+		list_move(&old->list, &clockevents_released);
+	}
+
+	if (new) {
+		BUG_ON(!clockevent_state_detached(new));
+		clockevents_shutdown(new);
+	}
+}
+
+/**
+ * clockevents_suspend - suspend clock devices
+ */
+void clockevents_suspend(void)
+{
+	struct clock_event_device *dev;
+
+	list_for_each_entry_reverse(dev, &clockevent_devices, list)
+		if (dev->suspend && !clockevent_state_detached(dev))
+			dev->suspend(dev);
+}
+
+/**
+ * clockevents_resume - resume clock devices
+ */
+void clockevents_resume(void)
+{
+	struct clock_event_device *dev;
+
+	list_for_each_entry(dev, &clockevent_devices, list)
+		if (dev->resume && !clockevent_state_detached(dev))
+			dev->resume(dev);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+/**
+ * tick_offline_cpu - Take CPU out of the broadcast mechanism
+ * @cpu:	The outgoing CPU
+ *
+ * Called on the outgoing CPU after it took itself offline.
+ */
+void tick_offline_cpu(unsigned int cpu)
+{
+	raw_spin_lock(&clockevents_lock);
+	tick_broadcast_offline(cpu);
+	raw_spin_unlock(&clockevents_lock);
+}
+# endif
+
+/**
+ * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
+ * @cpu:	The dead CPU
+ */
+void tick_cleanup_dead_cpu(int cpu)
+{
+	struct clock_event_device *dev, *tmp;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&clockevents_lock, flags);
+
+	tick_shutdown(cpu);
+	/*
+	 * Unregister the clock event devices which were
+	 * released from the users in the notify chain.
+	 */
+	list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
+		list_del(&dev->list);
+	/*
+	 * Now check whether the CPU has left unused per cpu devices
+	 */
+	list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
+		if (cpumask_test_cpu(cpu, dev->cpumask) &&
+		    cpumask_weight(dev->cpumask) == 1 &&
+		    !tick_is_broadcast_device(dev)) {
+			BUG_ON(!clockevent_state_detached(dev));
+			list_del(&dev->list);
+		}
+	}
+	raw_spin_unlock_irqrestore(&clockevents_lock, flags);
+}
+#endif
+
+#ifdef CONFIG_SYSFS
+static struct bus_type clockevents_subsys = {
+	.name		= "clockevents",
+	.dev_name       = "clockevent",
+};
+
+static DEFINE_PER_CPU(struct device, tick_percpu_dev);
+static struct tick_device *tick_get_tick_dev(struct device *dev);
+
+static ssize_t current_device_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct tick_device *td;
+	ssize_t count = 0;
+
+	raw_spin_lock_irq(&clockevents_lock);
+	td = tick_get_tick_dev(dev);
+	if (td && td->evtdev)
+		count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
+	raw_spin_unlock_irq(&clockevents_lock);
+	return count;
+}
+static DEVICE_ATTR_RO(current_device);
+
+/* We don't support the abomination of removable broadcast devices */
+static ssize_t unbind_device_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	char name[CS_NAME_LEN];
+	ssize_t ret = sysfs_get_uname(buf, name, count);
+	struct clock_event_device *ce = NULL, *iter;
+
+	if (ret < 0)
+		return ret;
+
+	ret = -ENODEV;
+	mutex_lock(&clockevents_mutex);
+	raw_spin_lock_irq(&clockevents_lock);
+	list_for_each_entry(iter, &clockevent_devices, list) {
+		if (!strcmp(iter->name, name)) {
+			ret = __clockevents_try_unbind(iter, dev->id);
+			ce = iter;
+			break;
+		}
+	}
+	raw_spin_unlock_irq(&clockevents_lock);
+	/*
+	 * We hold clockevents_mutex, so ce can't go away
+	 */
+	if (ret == -EAGAIN)
+		ret = clockevents_unbind(ce, dev->id);
+	mutex_unlock(&clockevents_mutex);
+	return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(unbind_device);
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+static struct device tick_bc_dev = {
+	.init_name	= "broadcast",
+	.id		= 0,
+	.bus		= &clockevents_subsys,
+};
+
+static struct tick_device *tick_get_tick_dev(struct device *dev)
+{
+	return dev == &tick_bc_dev ? tick_get_broadcast_device() :
+		&per_cpu(tick_cpu_device, dev->id);
+}
+
+static __init int tick_broadcast_init_sysfs(void)
+{
+	int err = device_register(&tick_bc_dev);
+
+	if (!err)
+		err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
+	return err;
+}
+#else
+static struct tick_device *tick_get_tick_dev(struct device *dev)
+{
+	return &per_cpu(tick_cpu_device, dev->id);
+}
+static inline int tick_broadcast_init_sysfs(void) { return 0; }
+#endif
+
+static int __init tick_init_sysfs(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct device *dev = &per_cpu(tick_percpu_dev, cpu);
+		int err;
+
+		dev->id = cpu;
+		dev->bus = &clockevents_subsys;
+		err = device_register(dev);
+		if (!err)
+			err = device_create_file(dev, &dev_attr_current_device);
+		if (!err)
+			err = device_create_file(dev, &dev_attr_unbind_device);
+		if (err)
+			return err;
+	}
+	return tick_broadcast_init_sysfs();
+}
+
+static int __init clockevents_init_sysfs(void)
+{
+	int err = subsys_system_register(&clockevents_subsys, NULL);
+
+	if (!err)
+		err = tick_init_sysfs();
+	return err;
+}
+device_initcall(clockevents_init_sysfs);
+#endif /* SYSFS */
diff --git a/kernel/time/clocksource-wdtest.c b/kernel/time/clocksource-wdtest.c
new file mode 100644
index 0000000000..df922f49d1
--- /dev/null
+++ b/kernel/time/clocksource-wdtest.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Unit test for the clocksource watchdog.
+ *
+ * Copyright (C) 2021 Facebook, Inc.
+ *
+ * Author: Paul E. McKenney <paulmck@kernel.org>
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/device.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
+#include <linux/tick.h>
+#include <linux/kthread.h>
+#include <linux/delay.h>
+#include <linux/prandom.h>
+#include <linux/cpu.h>
+
+#include "tick-internal.h"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>");
+
+static int holdoff = IS_BUILTIN(CONFIG_TEST_CLOCKSOURCE_WATCHDOG) ? 10 : 0;
+module_param(holdoff, int, 0444);
+MODULE_PARM_DESC(holdoff, "Time to wait to start test (s).");
+
+/* Watchdog kthread's task_struct pointer for debug purposes. */
+static struct task_struct *wdtest_task;
+
+static u64 wdtest_jiffies_read(struct clocksource *cs)
+{
+	return (u64)jiffies;
+}
+
+static struct clocksource clocksource_wdtest_jiffies = {
+	.name			= "wdtest-jiffies",
+	.rating			= 1, /* lowest valid rating*/
+	.uncertainty_margin	= TICK_NSEC,
+	.read			= wdtest_jiffies_read,
+	.mask			= CLOCKSOURCE_MASK(32),
+	.flags			= CLOCK_SOURCE_MUST_VERIFY,
+	.mult			= TICK_NSEC << JIFFIES_SHIFT, /* details above */
+	.shift			= JIFFIES_SHIFT,
+	.max_cycles		= 10,
+};
+
+static int wdtest_ktime_read_ndelays;
+static bool wdtest_ktime_read_fuzz;
+
+static u64 wdtest_ktime_read(struct clocksource *cs)
+{
+	int wkrn = READ_ONCE(wdtest_ktime_read_ndelays);
+	static int sign = 1;
+	u64 ret;
+
+	if (wkrn) {
+		udelay(cs->uncertainty_margin / 250);
+		WRITE_ONCE(wdtest_ktime_read_ndelays, wkrn - 1);
+	}
+	ret = ktime_get_real_fast_ns();
+	if (READ_ONCE(wdtest_ktime_read_fuzz)) {
+		sign = -sign;
+		ret = ret + sign * 100 * NSEC_PER_MSEC;
+	}
+	return ret;
+}
+
+static void wdtest_ktime_cs_mark_unstable(struct clocksource *cs)
+{
+	pr_info("--- Marking %s unstable due to clocksource watchdog.\n", cs->name);
+}
+
+#define KTIME_FLAGS (CLOCK_SOURCE_IS_CONTINUOUS | \
+		     CLOCK_SOURCE_VALID_FOR_HRES | \
+		     CLOCK_SOURCE_MUST_VERIFY | \
+		     CLOCK_SOURCE_VERIFY_PERCPU)
+
+static struct clocksource clocksource_wdtest_ktime = {
+	.name			= "wdtest-ktime",
+	.rating			= 300,
+	.read			= wdtest_ktime_read,
+	.mask			= CLOCKSOURCE_MASK(64),
+	.flags			= KTIME_FLAGS,
+	.mark_unstable		= wdtest_ktime_cs_mark_unstable,
+	.list			= LIST_HEAD_INIT(clocksource_wdtest_ktime.list),
+};
+
+/* Reset the clocksource if needed. */
+static void wdtest_ktime_clocksource_reset(void)
+{
+	if (clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE) {
+		clocksource_unregister(&clocksource_wdtest_ktime);
+		clocksource_wdtest_ktime.flags = KTIME_FLAGS;
+		schedule_timeout_uninterruptible(HZ / 10);
+		clocksource_register_khz(&clocksource_wdtest_ktime, 1000 * 1000);
+	}
+}
+
+/* Run the specified series of watchdog tests. */
+static int wdtest_func(void *arg)
+{
+	unsigned long j1, j2;
+	char *s;
+	int i;
+
+	schedule_timeout_uninterruptible(holdoff * HZ);
+
+	/*
+	 * Verify that jiffies-like clocksources get the manually
+	 * specified uncertainty margin.
+	 */
+	pr_info("--- Verify jiffies-like uncertainty margin.\n");
+	__clocksource_register(&clocksource_wdtest_jiffies);
+	WARN_ON_ONCE(clocksource_wdtest_jiffies.uncertainty_margin != TICK_NSEC);
+
+	j1 = clocksource_wdtest_jiffies.read(&clocksource_wdtest_jiffies);
+	schedule_timeout_uninterruptible(HZ);
+	j2 = clocksource_wdtest_jiffies.read(&clocksource_wdtest_jiffies);
+	WARN_ON_ONCE(j1 == j2);
+
+	clocksource_unregister(&clocksource_wdtest_jiffies);
+
+	/*
+	 * Verify that tsc-like clocksources are assigned a reasonable
+	 * uncertainty margin.
+	 */
+	pr_info("--- Verify tsc-like uncertainty margin.\n");
+	clocksource_register_khz(&clocksource_wdtest_ktime, 1000 * 1000);
+	WARN_ON_ONCE(clocksource_wdtest_ktime.uncertainty_margin < NSEC_PER_USEC);
+
+	j1 = clocksource_wdtest_ktime.read(&clocksource_wdtest_ktime);
+	udelay(1);
+	j2 = clocksource_wdtest_ktime.read(&clocksource_wdtest_ktime);
+	pr_info("--- tsc-like times: %lu - %lu = %lu.\n", j2, j1, j2 - j1);
+	WARN_ON_ONCE(time_before(j2, j1 + NSEC_PER_USEC));
+
+	/* Verify tsc-like stability with various numbers of errors injected. */
+	for (i = 0; i <= max_cswd_read_retries + 1; i++) {
+		if (i <= 1 && i < max_cswd_read_retries)
+			s = "";
+		else if (i <= max_cswd_read_retries)
+			s = ", expect message";
+		else
+			s = ", expect clock skew";
+		pr_info("--- Watchdog with %dx error injection, %lu retries%s.\n", i, max_cswd_read_retries, s);
+		WRITE_ONCE(wdtest_ktime_read_ndelays, i);
+		schedule_timeout_uninterruptible(2 * HZ);
+		WARN_ON_ONCE(READ_ONCE(wdtest_ktime_read_ndelays));
+		WARN_ON_ONCE((i <= max_cswd_read_retries) !=
+			     !(clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE));
+		wdtest_ktime_clocksource_reset();
+	}
+
+	/* Verify tsc-like stability with clock-value-fuzz error injection. */
+	pr_info("--- Watchdog clock-value-fuzz error injection, expect clock skew and per-CPU mismatches.\n");
+	WRITE_ONCE(wdtest_ktime_read_fuzz, true);
+	schedule_timeout_uninterruptible(2 * HZ);
+	WARN_ON_ONCE(!(clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE));
+	clocksource_verify_percpu(&clocksource_wdtest_ktime);
+	WRITE_ONCE(wdtest_ktime_read_fuzz, false);
+
+	clocksource_unregister(&clocksource_wdtest_ktime);
+
+	pr_info("--- Done with test.\n");
+	return 0;
+}
+
+static void wdtest_print_module_parms(void)
+{
+	pr_alert("--- holdoff=%d\n", holdoff);
+}
+
+/* Cleanup function. */
+static void clocksource_wdtest_cleanup(void)
+{
+}
+
+static int __init clocksource_wdtest_init(void)
+{
+	int ret = 0;
+
+	wdtest_print_module_parms();
+
+	/* Create watchdog-test task. */
+	wdtest_task = kthread_run(wdtest_func, NULL, "wdtest");
+	if (IS_ERR(wdtest_task)) {
+		ret = PTR_ERR(wdtest_task);
+		pr_warn("%s: Failed to create wdtest kthread.\n", __func__);
+		wdtest_task = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+module_init(clocksource_wdtest_init);
+module_exit(clocksource_wdtest_cleanup);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
new file mode 100644
index 0000000000..3052b1f116
--- /dev/null
+++ b/kernel/time/clocksource.c
@@ -0,0 +1,1530 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * This file contains the functions which manage clocksource drivers.
+ *
+ * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/device.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
+#include <linux/tick.h>
+#include <linux/kthread.h>
+#include <linux/prandom.h>
+#include <linux/cpu.h>
+
+#include "tick-internal.h"
+#include "timekeeping_internal.h"
+
+/**
+ * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
+ * @mult:	pointer to mult variable
+ * @shift:	pointer to shift variable
+ * @from:	frequency to convert from
+ * @to:		frequency to convert to
+ * @maxsec:	guaranteed runtime conversion range in seconds
+ *
+ * The function evaluates the shift/mult pair for the scaled math
+ * operations of clocksources and clockevents.
+ *
+ * @to and @from are frequency values in HZ. For clock sources @to is
+ * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
+ * event @to is the counter frequency and @from is NSEC_PER_SEC.
+ *
+ * The @maxsec conversion range argument controls the time frame in
+ * seconds which must be covered by the runtime conversion with the
+ * calculated mult and shift factors. This guarantees that no 64bit
+ * overflow happens when the input value of the conversion is
+ * multiplied with the calculated mult factor. Larger ranges may
+ * reduce the conversion accuracy by choosing smaller mult and shift
+ * factors.
+ */
+void
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
+{
+	u64 tmp;
+	u32 sft, sftacc= 32;
+
+	/*
+	 * Calculate the shift factor which is limiting the conversion
+	 * range:
+	 */
+	tmp = ((u64)maxsec * from) >> 32;
+	while (tmp) {
+		tmp >>=1;
+		sftacc--;
+	}
+
+	/*
+	 * Find the conversion shift/mult pair which has the best
+	 * accuracy and fits the maxsec conversion range:
+	 */
+	for (sft = 32; sft > 0; sft--) {
+		tmp = (u64) to << sft;
+		tmp += from / 2;
+		do_div(tmp, from);
+		if ((tmp >> sftacc) == 0)
+			break;
+	}
+	*mult = tmp;
+	*shift = sft;
+}
+EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
+
+/*[Clocksource internal variables]---------
+ * curr_clocksource:
+ *	currently selected clocksource.
+ * suspend_clocksource:
+ *	used to calculate the suspend time.
+ * clocksource_list:
+ *	linked list with the registered clocksources
+ * clocksource_mutex:
+ *	protects manipulations to curr_clocksource and the clocksource_list
+ * override_name:
+ *	Name of the user-specified clocksource.
+ */
+static struct clocksource *curr_clocksource;
+static struct clocksource *suspend_clocksource;
+static LIST_HEAD(clocksource_list);
+static DEFINE_MUTEX(clocksource_mutex);
+static char override_name[CS_NAME_LEN];
+static int finished_booting;
+static u64 suspend_start;
+
+/*
+ * Interval: 0.5sec.
+ */
+#define WATCHDOG_INTERVAL (HZ >> 1)
+#define WATCHDOG_INTERVAL_MAX_NS ((2 * WATCHDOG_INTERVAL) * (NSEC_PER_SEC / HZ))
+
+/*
+ * Threshold: 0.0312s, when doubled: 0.0625s.
+ * Also a default for cs->uncertainty_margin when registering clocks.
+ */
+#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
+
+/*
+ * Maximum permissible delay between two readouts of the watchdog
+ * clocksource surrounding a read of the clocksource being validated.
+ * This delay could be due to SMIs, NMIs, or to VCPU preemptions.  Used as
+ * a lower bound for cs->uncertainty_margin values when registering clocks.
+ *
+ * The default of 500 parts per million is based on NTP's limits.
+ * If a clocksource is good enough for NTP, it is good enough for us!
+ */
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+#define MAX_SKEW_USEC	CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+#else
+#define MAX_SKEW_USEC	(125 * WATCHDOG_INTERVAL / HZ)
+#endif
+
+#define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
+
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+static void clocksource_watchdog_work(struct work_struct *work);
+static void clocksource_select(void);
+
+static LIST_HEAD(watchdog_list);
+static struct clocksource *watchdog;
+static struct timer_list watchdog_timer;
+static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
+static DEFINE_SPINLOCK(watchdog_lock);
+static int watchdog_running;
+static atomic_t watchdog_reset_pending;
+static int64_t watchdog_max_interval;
+
+static inline void clocksource_watchdog_lock(unsigned long *flags)
+{
+	spin_lock_irqsave(&watchdog_lock, *flags);
+}
+
+static inline void clocksource_watchdog_unlock(unsigned long *flags)
+{
+	spin_unlock_irqrestore(&watchdog_lock, *flags);
+}
+
+static int clocksource_watchdog_kthread(void *data);
+static void __clocksource_change_rating(struct clocksource *cs, int rating);
+
+static void clocksource_watchdog_work(struct work_struct *work)
+{
+	/*
+	 * We cannot directly run clocksource_watchdog_kthread() here, because
+	 * clocksource_select() calls timekeeping_notify() which uses
+	 * stop_machine(). One cannot use stop_machine() from a workqueue() due
+	 * lock inversions wrt CPU hotplug.
+	 *
+	 * Also, we only ever run this work once or twice during the lifetime
+	 * of the kernel, so there is no point in creating a more permanent
+	 * kthread for this.
+	 *
+	 * If kthread_run fails the next watchdog scan over the
+	 * watchdog_list will find the unstable clock again.
+	 */
+	kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
+}
+
+static void __clocksource_unstable(struct clocksource *cs)
+{
+	cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
+	cs->flags |= CLOCK_SOURCE_UNSTABLE;
+
+	/*
+	 * If the clocksource is registered clocksource_watchdog_kthread() will
+	 * re-rate and re-select.
+	 */
+	if (list_empty(&cs->list)) {
+		cs->rating = 0;
+		return;
+	}
+
+	if (cs->mark_unstable)
+		cs->mark_unstable(cs);
+
+	/* kick clocksource_watchdog_kthread() */
+	if (finished_booting)
+		schedule_work(&watchdog_work);
+}
+
+/**
+ * clocksource_mark_unstable - mark clocksource unstable via watchdog
+ * @cs:		clocksource to be marked unstable
+ *
+ * This function is called by the x86 TSC code to mark clocksources as unstable;
+ * it defers demotion and re-selection to a kthread.
+ */
+void clocksource_mark_unstable(struct clocksource *cs)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&watchdog_lock, flags);
+	if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
+		if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
+			list_add(&cs->wd_list, &watchdog_list);
+		__clocksource_unstable(cs);
+	}
+	spin_unlock_irqrestore(&watchdog_lock, flags);
+}
+
+ulong max_cswd_read_retries = 2;
+module_param(max_cswd_read_retries, ulong, 0644);
+EXPORT_SYMBOL_GPL(max_cswd_read_retries);
+static int verify_n_cpus = 8;
+module_param(verify_n_cpus, int, 0644);
+
+enum wd_read_status {
+	WD_READ_SUCCESS,
+	WD_READ_UNSTABLE,
+	WD_READ_SKIP
+};
+
+static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
+{
+	unsigned int nretries;
+	u64 wd_end, wd_end2, wd_delta;
+	int64_t wd_delay, wd_seq_delay;
+
+	for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
+		local_irq_disable();
+		*wdnow = watchdog->read(watchdog);
+		*csnow = cs->read(cs);
+		wd_end = watchdog->read(watchdog);
+		wd_end2 = watchdog->read(watchdog);
+		local_irq_enable();
+
+		wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
+		wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
+					      watchdog->shift);
+		if (wd_delay <= WATCHDOG_MAX_SKEW) {
+			if (nretries > 1 || nretries >= max_cswd_read_retries) {
+				pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
+					smp_processor_id(), watchdog->name, nretries);
+			}
+			return WD_READ_SUCCESS;
+		}
+
+		/*
+		 * Now compute delay in consecutive watchdog read to see if
+		 * there is too much external interferences that cause
+		 * significant delay in reading both clocksource and watchdog.
+		 *
+		 * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
+		 * report system busy, reinit the watchdog and skip the current
+		 * watchdog test.
+		 */
+		wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
+		wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
+		if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
+			goto skip_test;
+	}
+
+	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd excessive read-back delay of %lldns vs. limit of %ldns, wd-wd read-back delay only %lldns, attempt %d, marking %s unstable\n",
+		smp_processor_id(), cs->name, wd_delay, WATCHDOG_MAX_SKEW, wd_seq_delay, nretries, cs->name);
+	return WD_READ_UNSTABLE;
+
+skip_test:
+	pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
+		smp_processor_id(), watchdog->name, wd_seq_delay);
+	pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
+		cs->name, wd_delay);
+	return WD_READ_SKIP;
+}
+
+static u64 csnow_mid;
+static cpumask_t cpus_ahead;
+static cpumask_t cpus_behind;
+static cpumask_t cpus_chosen;
+
+static void clocksource_verify_choose_cpus(void)
+{
+	int cpu, i, n = verify_n_cpus;
+
+	if (n < 0) {
+		/* Check all of the CPUs. */
+		cpumask_copy(&cpus_chosen, cpu_online_mask);
+		cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
+		return;
+	}
+
+	/* If no checking desired, or no other CPU to check, leave. */
+	cpumask_clear(&cpus_chosen);
+	if (n == 0 || num_online_cpus() <= 1)
+		return;
+
+	/* Make sure to select at least one CPU other than the current CPU. */
+	cpu = cpumask_first(cpu_online_mask);
+	if (cpu == smp_processor_id())
+		cpu = cpumask_next(cpu, cpu_online_mask);
+	if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
+		return;
+	cpumask_set_cpu(cpu, &cpus_chosen);
+
+	/* Force a sane value for the boot parameter. */
+	if (n > nr_cpu_ids)
+		n = nr_cpu_ids;
+
+	/*
+	 * Randomly select the specified number of CPUs.  If the same
+	 * CPU is selected multiple times, that CPU is checked only once,
+	 * and no replacement CPU is selected.  This gracefully handles
+	 * situations where verify_n_cpus is greater than the number of
+	 * CPUs that are currently online.
+	 */
+	for (i = 1; i < n; i++) {
+		cpu = get_random_u32_below(nr_cpu_ids);
+		cpu = cpumask_next(cpu - 1, cpu_online_mask);
+		if (cpu >= nr_cpu_ids)
+			cpu = cpumask_first(cpu_online_mask);
+		if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
+			cpumask_set_cpu(cpu, &cpus_chosen);
+	}
+
+	/* Don't verify ourselves. */
+	cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
+}
+
+static void clocksource_verify_one_cpu(void *csin)
+{
+	struct clocksource *cs = (struct clocksource *)csin;
+
+	csnow_mid = cs->read(cs);
+}
+
+void clocksource_verify_percpu(struct clocksource *cs)
+{
+	int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
+	u64 csnow_begin, csnow_end;
+	int cpu, testcpu;
+	s64 delta;
+
+	if (verify_n_cpus == 0)
+		return;
+	cpumask_clear(&cpus_ahead);
+	cpumask_clear(&cpus_behind);
+	cpus_read_lock();
+	preempt_disable();
+	clocksource_verify_choose_cpus();
+	if (cpumask_empty(&cpus_chosen)) {
+		preempt_enable();
+		cpus_read_unlock();
+		pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
+		return;
+	}
+	testcpu = smp_processor_id();
+	pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
+	for_each_cpu(cpu, &cpus_chosen) {
+		if (cpu == testcpu)
+			continue;
+		csnow_begin = cs->read(cs);
+		smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
+		csnow_end = cs->read(cs);
+		delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
+		if (delta < 0)
+			cpumask_set_cpu(cpu, &cpus_behind);
+		delta = (csnow_end - csnow_mid) & cs->mask;
+		if (delta < 0)
+			cpumask_set_cpu(cpu, &cpus_ahead);
+		delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
+		cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
+		if (cs_nsec > cs_nsec_max)
+			cs_nsec_max = cs_nsec;
+		if (cs_nsec < cs_nsec_min)
+			cs_nsec_min = cs_nsec;
+	}
+	preempt_enable();
+	cpus_read_unlock();
+	if (!cpumask_empty(&cpus_ahead))
+		pr_warn("        CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
+			cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
+	if (!cpumask_empty(&cpus_behind))
+		pr_warn("        CPUs %*pbl behind CPU %d for clocksource %s.\n",
+			cpumask_pr_args(&cpus_behind), testcpu, cs->name);
+	if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
+		pr_warn("        CPU %d check durations %lldns - %lldns for clocksource %s.\n",
+			testcpu, cs_nsec_min, cs_nsec_max, cs->name);
+}
+EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
+
+static inline void clocksource_reset_watchdog(void)
+{
+	struct clocksource *cs;
+
+	list_for_each_entry(cs, &watchdog_list, wd_list)
+		cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
+}
+
+
+static void clocksource_watchdog(struct timer_list *unused)
+{
+	u64 csnow, wdnow, cslast, wdlast, delta;
+	int64_t wd_nsec, cs_nsec, interval;
+	int next_cpu, reset_pending;
+	struct clocksource *cs;
+	enum wd_read_status read_ret;
+	unsigned long extra_wait = 0;
+	u32 md;
+
+	spin_lock(&watchdog_lock);
+	if (!watchdog_running)
+		goto out;
+
+	reset_pending = atomic_read(&watchdog_reset_pending);
+
+	list_for_each_entry(cs, &watchdog_list, wd_list) {
+
+		/* Clocksource already marked unstable? */
+		if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
+			if (finished_booting)
+				schedule_work(&watchdog_work);
+			continue;
+		}
+
+		read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
+
+		if (read_ret == WD_READ_UNSTABLE) {
+			/* Clock readout unreliable, so give it up. */
+			__clocksource_unstable(cs);
+			continue;
+		}
+
+		/*
+		 * When WD_READ_SKIP is returned, it means the system is likely
+		 * under very heavy load, where the latency of reading
+		 * watchdog/clocksource is very big, and affect the accuracy of
+		 * watchdog check. So give system some space and suspend the
+		 * watchdog check for 5 minutes.
+		 */
+		if (read_ret == WD_READ_SKIP) {
+			/*
+			 * As the watchdog timer will be suspended, and
+			 * cs->last could keep unchanged for 5 minutes, reset
+			 * the counters.
+			 */
+			clocksource_reset_watchdog();
+			extra_wait = HZ * 300;
+			break;
+		}
+
+		/* Clocksource initialized ? */
+		if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
+		    atomic_read(&watchdog_reset_pending)) {
+			cs->flags |= CLOCK_SOURCE_WATCHDOG;
+			cs->wd_last = wdnow;
+			cs->cs_last = csnow;
+			continue;
+		}
+
+		delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
+		wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
+					     watchdog->shift);
+
+		delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
+		cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
+		wdlast = cs->wd_last; /* save these in case we print them */
+		cslast = cs->cs_last;
+		cs->cs_last = csnow;
+		cs->wd_last = wdnow;
+
+		if (atomic_read(&watchdog_reset_pending))
+			continue;
+
+		/*
+		 * The processing of timer softirqs can get delayed (usually
+		 * on account of ksoftirqd not getting to run in a timely
+		 * manner), which causes the watchdog interval to stretch.
+		 * Skew detection may fail for longer watchdog intervals
+		 * on account of fixed margins being used.
+		 * Some clocksources, e.g. acpi_pm, cannot tolerate
+		 * watchdog intervals longer than a few seconds.
+		 */
+		interval = max(cs_nsec, wd_nsec);
+		if (unlikely(interval > WATCHDOG_INTERVAL_MAX_NS)) {
+			if (system_state > SYSTEM_SCHEDULING &&
+			    interval > 2 * watchdog_max_interval) {
+				watchdog_max_interval = interval;
+				pr_warn("Long readout interval, skipping watchdog check: cs_nsec: %lld wd_nsec: %lld\n",
+					cs_nsec, wd_nsec);
+			}
+			watchdog_timer.expires = jiffies;
+			continue;
+		}
+
+		/* Check the deviation from the watchdog clocksource. */
+		md = cs->uncertainty_margin + watchdog->uncertainty_margin;
+		if (abs(cs_nsec - wd_nsec) > md) {
+			s64 cs_wd_msec;
+			s64 wd_msec;
+			u32 wd_rem;
+
+			pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
+				smp_processor_id(), cs->name);
+			pr_warn("                      '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
+				watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
+			pr_warn("                      '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
+				cs->name, cs_nsec, csnow, cslast, cs->mask);
+			cs_wd_msec = div_s64_rem(cs_nsec - wd_nsec, 1000 * 1000, &wd_rem);
+			wd_msec = div_s64_rem(wd_nsec, 1000 * 1000, &wd_rem);
+			pr_warn("                      Clocksource '%s' skewed %lld ns (%lld ms) over watchdog '%s' interval of %lld ns (%lld ms)\n",
+				cs->name, cs_nsec - wd_nsec, cs_wd_msec, watchdog->name, wd_nsec, wd_msec);
+			if (curr_clocksource == cs)
+				pr_warn("                      '%s' is current clocksource.\n", cs->name);
+			else if (curr_clocksource)
+				pr_warn("                      '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name);
+			else
+				pr_warn("                      No current clocksource.\n");
+			__clocksource_unstable(cs);
+			continue;
+		}
+
+		if (cs == curr_clocksource && cs->tick_stable)
+			cs->tick_stable(cs);
+
+		if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
+		    (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
+		    (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
+			/* Mark it valid for high-res. */
+			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+
+			/*
+			 * clocksource_done_booting() will sort it if
+			 * finished_booting is not set yet.
+			 */
+			if (!finished_booting)
+				continue;
+
+			/*
+			 * If this is not the current clocksource let
+			 * the watchdog thread reselect it. Due to the
+			 * change to high res this clocksource might
+			 * be preferred now. If it is the current
+			 * clocksource let the tick code know about
+			 * that change.
+			 */
+			if (cs != curr_clocksource) {
+				cs->flags |= CLOCK_SOURCE_RESELECT;
+				schedule_work(&watchdog_work);
+			} else {
+				tick_clock_notify();
+			}
+		}
+	}
+
+	/*
+	 * We only clear the watchdog_reset_pending, when we did a
+	 * full cycle through all clocksources.
+	 */
+	if (reset_pending)
+		atomic_dec(&watchdog_reset_pending);
+
+	/*
+	 * Cycle through CPUs to check if the CPUs stay synchronized
+	 * to each other.
+	 */
+	next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
+	if (next_cpu >= nr_cpu_ids)
+		next_cpu = cpumask_first(cpu_online_mask);
+
+	/*
+	 * Arm timer if not already pending: could race with concurrent
+	 * pair clocksource_stop_watchdog() clocksource_start_watchdog().
+	 */
+	if (!timer_pending(&watchdog_timer)) {
+		watchdog_timer.expires += WATCHDOG_INTERVAL + extra_wait;
+		add_timer_on(&watchdog_timer, next_cpu);
+	}
+out:
+	spin_unlock(&watchdog_lock);
+}
+
+static inline void clocksource_start_watchdog(void)
+{
+	if (watchdog_running || !watchdog || list_empty(&watchdog_list))
+		return;
+	timer_setup(&watchdog_timer, clocksource_watchdog, 0);
+	watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
+	add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
+	watchdog_running = 1;
+}
+
+static inline void clocksource_stop_watchdog(void)
+{
+	if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
+		return;
+	del_timer(&watchdog_timer);
+	watchdog_running = 0;
+}
+
+static void clocksource_resume_watchdog(void)
+{
+	atomic_inc(&watchdog_reset_pending);
+}
+
+static void clocksource_enqueue_watchdog(struct clocksource *cs)
+{
+	INIT_LIST_HEAD(&cs->wd_list);
+
+	if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
+		/* cs is a clocksource to be watched. */
+		list_add(&cs->wd_list, &watchdog_list);
+		cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
+	} else {
+		/* cs is a watchdog. */
+		if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
+			cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+	}
+}
+
+static void clocksource_select_watchdog(bool fallback)
+{
+	struct clocksource *cs, *old_wd;
+	unsigned long flags;
+
+	spin_lock_irqsave(&watchdog_lock, flags);
+	/* save current watchdog */
+	old_wd = watchdog;
+	if (fallback)
+		watchdog = NULL;
+
+	list_for_each_entry(cs, &clocksource_list, list) {
+		/* cs is a clocksource to be watched. */
+		if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
+			continue;
+
+		/* Skip current if we were requested for a fallback. */
+		if (fallback && cs == old_wd)
+			continue;
+
+		/* Pick the best watchdog. */
+		if (!watchdog || cs->rating > watchdog->rating)
+			watchdog = cs;
+	}
+	/* If we failed to find a fallback restore the old one. */
+	if (!watchdog)
+		watchdog = old_wd;
+
+	/* If we changed the watchdog we need to reset cycles. */
+	if (watchdog != old_wd)
+		clocksource_reset_watchdog();
+
+	/* Check if the watchdog timer needs to be started. */
+	clocksource_start_watchdog();
+	spin_unlock_irqrestore(&watchdog_lock, flags);
+}
+
+static void clocksource_dequeue_watchdog(struct clocksource *cs)
+{
+	if (cs != watchdog) {
+		if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
+			/* cs is a watched clocksource. */
+			list_del_init(&cs->wd_list);
+			/* Check if the watchdog timer needs to be stopped. */
+			clocksource_stop_watchdog();
+		}
+	}
+}
+
+static int __clocksource_watchdog_kthread(void)
+{
+	struct clocksource *cs, *tmp;
+	unsigned long flags;
+	int select = 0;
+
+	/* Do any required per-CPU skew verification. */
+	if (curr_clocksource &&
+	    curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
+	    curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
+		clocksource_verify_percpu(curr_clocksource);
+
+	spin_lock_irqsave(&watchdog_lock, flags);
+	list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
+		if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
+			list_del_init(&cs->wd_list);
+			__clocksource_change_rating(cs, 0);
+			select = 1;
+		}
+		if (cs->flags & CLOCK_SOURCE_RESELECT) {
+			cs->flags &= ~CLOCK_SOURCE_RESELECT;
+			select = 1;
+		}
+	}
+	/* Check if the watchdog timer needs to be stopped. */
+	clocksource_stop_watchdog();
+	spin_unlock_irqrestore(&watchdog_lock, flags);
+
+	return select;
+}
+
+static int clocksource_watchdog_kthread(void *data)
+{
+	mutex_lock(&clocksource_mutex);
+	if (__clocksource_watchdog_kthread())
+		clocksource_select();
+	mutex_unlock(&clocksource_mutex);
+	return 0;
+}
+
+static bool clocksource_is_watchdog(struct clocksource *cs)
+{
+	return cs == watchdog;
+}
+
+#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
+
+static void clocksource_enqueue_watchdog(struct clocksource *cs)
+{
+	if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
+		cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
+}
+
+static void clocksource_select_watchdog(bool fallback) { }
+static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
+static inline void clocksource_resume_watchdog(void) { }
+static inline int __clocksource_watchdog_kthread(void) { return 0; }
+static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
+void clocksource_mark_unstable(struct clocksource *cs) { }
+
+static inline void clocksource_watchdog_lock(unsigned long *flags) { }
+static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
+
+#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
+
+static bool clocksource_is_suspend(struct clocksource *cs)
+{
+	return cs == suspend_clocksource;
+}
+
+static void __clocksource_suspend_select(struct clocksource *cs)
+{
+	/*
+	 * Skip the clocksource which will be stopped in suspend state.
+	 */
+	if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
+		return;
+
+	/*
+	 * The nonstop clocksource can be selected as the suspend clocksource to
+	 * calculate the suspend time, so it should not supply suspend/resume
+	 * interfaces to suspend the nonstop clocksource when system suspends.
+	 */
+	if (cs->suspend || cs->resume) {
+		pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
+			cs->name);
+	}
+
+	/* Pick the best rating. */
+	if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
+		suspend_clocksource = cs;
+}
+
+/**
+ * clocksource_suspend_select - Select the best clocksource for suspend timing
+ * @fallback:	if select a fallback clocksource
+ */
+static void clocksource_suspend_select(bool fallback)
+{
+	struct clocksource *cs, *old_suspend;
+
+	old_suspend = suspend_clocksource;
+	if (fallback)
+		suspend_clocksource = NULL;
+
+	list_for_each_entry(cs, &clocksource_list, list) {
+		/* Skip current if we were requested for a fallback. */
+		if (fallback && cs == old_suspend)
+			continue;
+
+		__clocksource_suspend_select(cs);
+	}
+}
+
+/**
+ * clocksource_start_suspend_timing - Start measuring the suspend timing
+ * @cs:			current clocksource from timekeeping
+ * @start_cycles:	current cycles from timekeeping
+ *
+ * This function will save the start cycle values of suspend timer to calculate
+ * the suspend time when resuming system.
+ *
+ * This function is called late in the suspend process from timekeeping_suspend(),
+ * that means processes are frozen, non-boot cpus and interrupts are disabled
+ * now. It is therefore possible to start the suspend timer without taking the
+ * clocksource mutex.
+ */
+void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
+{
+	if (!suspend_clocksource)
+		return;
+
+	/*
+	 * If current clocksource is the suspend timer, we should use the
+	 * tkr_mono.cycle_last value as suspend_start to avoid same reading
+	 * from suspend timer.
+	 */
+	if (clocksource_is_suspend(cs)) {
+		suspend_start = start_cycles;
+		return;
+	}
+
+	if (suspend_clocksource->enable &&
+	    suspend_clocksource->enable(suspend_clocksource)) {
+		pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
+		return;
+	}
+
+	suspend_start = suspend_clocksource->read(suspend_clocksource);
+}
+
+/**
+ * clocksource_stop_suspend_timing - Stop measuring the suspend timing
+ * @cs:		current clocksource from timekeeping
+ * @cycle_now:	current cycles from timekeeping
+ *
+ * This function will calculate the suspend time from suspend timer.
+ *
+ * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
+ *
+ * This function is called early in the resume process from timekeeping_resume(),
+ * that means there is only one cpu, no processes are running and the interrupts
+ * are disabled. It is therefore possible to stop the suspend timer without
+ * taking the clocksource mutex.
+ */
+u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
+{
+	u64 now, delta, nsec = 0;
+
+	if (!suspend_clocksource)
+		return 0;
+
+	/*
+	 * If current clocksource is the suspend timer, we should use the
+	 * tkr_mono.cycle_last value from timekeeping as current cycle to
+	 * avoid same reading from suspend timer.
+	 */
+	if (clocksource_is_suspend(cs))
+		now = cycle_now;
+	else
+		now = suspend_clocksource->read(suspend_clocksource);
+
+	if (now > suspend_start) {
+		delta = clocksource_delta(now, suspend_start,
+					  suspend_clocksource->mask);
+		nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
+				       suspend_clocksource->shift);
+	}
+
+	/*
+	 * Disable the suspend timer to save power if current clocksource is
+	 * not the suspend timer.
+	 */
+	if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
+		suspend_clocksource->disable(suspend_clocksource);
+
+	return nsec;
+}
+
+/**
+ * clocksource_suspend - suspend the clocksource(s)
+ */
+void clocksource_suspend(void)
+{
+	struct clocksource *cs;
+
+	list_for_each_entry_reverse(cs, &clocksource_list, list)
+		if (cs->suspend)
+			cs->suspend(cs);
+}
+
+/**
+ * clocksource_resume - resume the clocksource(s)
+ */
+void clocksource_resume(void)
+{
+	struct clocksource *cs;
+
+	list_for_each_entry(cs, &clocksource_list, list)
+		if (cs->resume)
+			cs->resume(cs);
+
+	clocksource_resume_watchdog();
+}
+
+/**
+ * clocksource_touch_watchdog - Update watchdog
+ *
+ * Update the watchdog after exception contexts such as kgdb so as not
+ * to incorrectly trip the watchdog. This might fail when the kernel
+ * was stopped in code which holds watchdog_lock.
+ */
+void clocksource_touch_watchdog(void)
+{
+	clocksource_resume_watchdog();
+}
+
+/**
+ * clocksource_max_adjustment- Returns max adjustment amount
+ * @cs:         Pointer to clocksource
+ *
+ */
+static u32 clocksource_max_adjustment(struct clocksource *cs)
+{
+	u64 ret;
+	/*
+	 * We won't try to correct for more than 11% adjustments (110,000 ppm),
+	 */
+	ret = (u64)cs->mult * 11;
+	do_div(ret,100);
+	return (u32)ret;
+}
+
+/**
+ * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
+ * @mult:	cycle to nanosecond multiplier
+ * @shift:	cycle to nanosecond divisor (power of two)
+ * @maxadj:	maximum adjustment value to mult (~11%)
+ * @mask:	bitmask for two's complement subtraction of non 64 bit counters
+ * @max_cyc:	maximum cycle value before potential overflow (does not include
+ *		any safety margin)
+ *
+ * NOTE: This function includes a safety margin of 50%, in other words, we
+ * return half the number of nanoseconds the hardware counter can technically
+ * cover. This is done so that we can potentially detect problems caused by
+ * delayed timers or bad hardware, which might result in time intervals that
+ * are larger than what the math used can handle without overflows.
+ */
+u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
+{
+	u64 max_nsecs, max_cycles;
+
+	/*
+	 * Calculate the maximum number of cycles that we can pass to the
+	 * cyc2ns() function without overflowing a 64-bit result.
+	 */
+	max_cycles = ULLONG_MAX;
+	do_div(max_cycles, mult+maxadj);
+
+	/*
+	 * The actual maximum number of cycles we can defer the clocksource is
+	 * determined by the minimum of max_cycles and mask.
+	 * Note: Here we subtract the maxadj to make sure we don't sleep for
+	 * too long if there's a large negative adjustment.
+	 */
+	max_cycles = min(max_cycles, mask);
+	max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
+
+	/* return the max_cycles value as well if requested */
+	if (max_cyc)
+		*max_cyc = max_cycles;
+
+	/* Return 50% of the actual maximum, so we can detect bad values */
+	max_nsecs >>= 1;
+
+	return max_nsecs;
+}
+
+/**
+ * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
+ * @cs:         Pointer to clocksource to be updated
+ *
+ */
+static inline void clocksource_update_max_deferment(struct clocksource *cs)
+{
+	cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
+						cs->maxadj, cs->mask,
+						&cs->max_cycles);
+}
+
+static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
+{
+	struct clocksource *cs;
+
+	if (!finished_booting || list_empty(&clocksource_list))
+		return NULL;
+
+	/*
+	 * We pick the clocksource with the highest rating. If oneshot
+	 * mode is active, we pick the highres valid clocksource with
+	 * the best rating.
+	 */
+	list_for_each_entry(cs, &clocksource_list, list) {
+		if (skipcur && cs == curr_clocksource)
+			continue;
+		if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+			continue;
+		return cs;
+	}
+	return NULL;
+}
+
+static void __clocksource_select(bool skipcur)
+{
+	bool oneshot = tick_oneshot_mode_active();
+	struct clocksource *best, *cs;
+
+	/* Find the best suitable clocksource */
+	best = clocksource_find_best(oneshot, skipcur);
+	if (!best)
+		return;
+
+	if (!strlen(override_name))
+		goto found;
+
+	/* Check for the override clocksource. */
+	list_for_each_entry(cs, &clocksource_list, list) {
+		if (skipcur && cs == curr_clocksource)
+			continue;
+		if (strcmp(cs->name, override_name) != 0)
+			continue;
+		/*
+		 * Check to make sure we don't switch to a non-highres
+		 * capable clocksource if the tick code is in oneshot
+		 * mode (highres or nohz)
+		 */
+		if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
+			/* Override clocksource cannot be used. */
+			if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
+				pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
+					cs->name);
+				override_name[0] = 0;
+			} else {
+				/*
+				 * The override cannot be currently verified.
+				 * Deferring to let the watchdog check.
+				 */
+				pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
+					cs->name);
+			}
+		} else
+			/* Override clocksource can be used. */
+			best = cs;
+		break;
+	}
+
+found:
+	if (curr_clocksource != best && !timekeeping_notify(best)) {
+		pr_info("Switched to clocksource %s\n", best->name);
+		curr_clocksource = best;
+	}
+}
+
+/**
+ * clocksource_select - Select the best clocksource available
+ *
+ * Private function. Must hold clocksource_mutex when called.
+ *
+ * Select the clocksource with the best rating, or the clocksource,
+ * which is selected by userspace override.
+ */
+static void clocksource_select(void)
+{
+	__clocksource_select(false);
+}
+
+static void clocksource_select_fallback(void)
+{
+	__clocksource_select(true);
+}
+
+/*
+ * clocksource_done_booting - Called near the end of core bootup
+ *
+ * Hack to avoid lots of clocksource churn at boot time.
+ * We use fs_initcall because we want this to start before
+ * device_initcall but after subsys_initcall.
+ */
+static int __init clocksource_done_booting(void)
+{
+	mutex_lock(&clocksource_mutex);
+	curr_clocksource = clocksource_default_clock();
+	finished_booting = 1;
+	/*
+	 * Run the watchdog first to eliminate unstable clock sources
+	 */
+	__clocksource_watchdog_kthread();
+	clocksource_select();
+	mutex_unlock(&clocksource_mutex);
+	return 0;
+}
+fs_initcall(clocksource_done_booting);
+
+/*
+ * Enqueue the clocksource sorted by rating
+ */
+static void clocksource_enqueue(struct clocksource *cs)
+{
+	struct list_head *entry = &clocksource_list;
+	struct clocksource *tmp;
+
+	list_for_each_entry(tmp, &clocksource_list, list) {
+		/* Keep track of the place, where to insert */
+		if (tmp->rating < cs->rating)
+			break;
+		entry = &tmp->list;
+	}
+	list_add(&cs->list, entry);
+}
+
+/**
+ * __clocksource_update_freq_scale - Used update clocksource with new freq
+ * @cs:		clocksource to be registered
+ * @scale:	Scale factor multiplied against freq to get clocksource hz
+ * @freq:	clocksource frequency (cycles per second) divided by scale
+ *
+ * This should only be called from the clocksource->enable() method.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
+ * functions.
+ */
+void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+	u64 sec;
+
+	/*
+	 * Default clocksources are *special* and self-define their mult/shift.
+	 * But, you're not special, so you should specify a freq value.
+	 */
+	if (freq) {
+		/*
+		 * Calc the maximum number of seconds which we can run before
+		 * wrapping around. For clocksources which have a mask > 32-bit
+		 * we need to limit the max sleep time to have a good
+		 * conversion precision. 10 minutes is still a reasonable
+		 * amount. That results in a shift value of 24 for a
+		 * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
+		 * ~ 0.06ppm granularity for NTP.
+		 */
+		sec = cs->mask;
+		do_div(sec, freq);
+		do_div(sec, scale);
+		if (!sec)
+			sec = 1;
+		else if (sec > 600 && cs->mask > UINT_MAX)
+			sec = 600;
+
+		clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+				       NSEC_PER_SEC / scale, sec * scale);
+	}
+
+	/*
+	 * If the uncertainty margin is not specified, calculate it.
+	 * If both scale and freq are non-zero, calculate the clock
+	 * period, but bound below at 2*WATCHDOG_MAX_SKEW.  However,
+	 * if either of scale or freq is zero, be very conservative and
+	 * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the
+	 * uncertainty margin.  Allow stupidly small uncertainty margins
+	 * to be specified by the caller for testing purposes, but warn
+	 * to discourage production use of this capability.
+	 */
+	if (scale && freq && !cs->uncertainty_margin) {
+		cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq);
+		if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW)
+			cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW;
+	} else if (!cs->uncertainty_margin) {
+		cs->uncertainty_margin = WATCHDOG_THRESHOLD;
+	}
+	WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW);
+
+	/*
+	 * Ensure clocksources that have large 'mult' values don't overflow
+	 * when adjusted.
+	 */
+	cs->maxadj = clocksource_max_adjustment(cs);
+	while (freq && ((cs->mult + cs->maxadj < cs->mult)
+		|| (cs->mult - cs->maxadj > cs->mult))) {
+		cs->mult >>= 1;
+		cs->shift--;
+		cs->maxadj = clocksource_max_adjustment(cs);
+	}
+
+	/*
+	 * Only warn for *special* clocksources that self-define
+	 * their mult/shift values and don't specify a freq.
+	 */
+	WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
+		"timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
+		cs->name);
+
+	clocksource_update_max_deferment(cs);
+
+	pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
+		cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
+}
+EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
+
+/**
+ * __clocksource_register_scale - Used to install new clocksources
+ * @cs:		clocksource to be registered
+ * @scale:	Scale factor multiplied against freq to get clocksource hz
+ * @freq:	clocksource frequency (cycles per second) divided by scale
+ *
+ * Returns -EBUSY if registration fails, zero otherwise.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * clocksource_register_hz() or clocksource_register_khz helper functions.
+ */
+int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+	unsigned long flags;
+
+	clocksource_arch_init(cs);
+
+	if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX))
+		cs->id = CSID_GENERIC;
+	if (cs->vdso_clock_mode < 0 ||
+	    cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
+		pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
+			cs->name, cs->vdso_clock_mode);
+		cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
+	}
+
+	/* Initialize mult/shift and max_idle_ns */
+	__clocksource_update_freq_scale(cs, scale, freq);
+
+	/* Add clocksource to the clocksource list */
+	mutex_lock(&clocksource_mutex);
+
+	clocksource_watchdog_lock(&flags);
+	clocksource_enqueue(cs);
+	clocksource_enqueue_watchdog(cs);
+	clocksource_watchdog_unlock(&flags);
+
+	clocksource_select();
+	clocksource_select_watchdog(false);
+	__clocksource_suspend_select(cs);
+	mutex_unlock(&clocksource_mutex);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__clocksource_register_scale);
+
+static void __clocksource_change_rating(struct clocksource *cs, int rating)
+{
+	list_del(&cs->list);
+	cs->rating = rating;
+	clocksource_enqueue(cs);
+}
+
+/**
+ * clocksource_change_rating - Change the rating of a registered clocksource
+ * @cs:		clocksource to be changed
+ * @rating:	new rating
+ */
+void clocksource_change_rating(struct clocksource *cs, int rating)
+{
+	unsigned long flags;
+
+	mutex_lock(&clocksource_mutex);
+	clocksource_watchdog_lock(&flags);
+	__clocksource_change_rating(cs, rating);
+	clocksource_watchdog_unlock(&flags);
+
+	clocksource_select();
+	clocksource_select_watchdog(false);
+	clocksource_suspend_select(false);
+	mutex_unlock(&clocksource_mutex);
+}
+EXPORT_SYMBOL(clocksource_change_rating);
+
+/*
+ * Unbind clocksource @cs. Called with clocksource_mutex held
+ */
+static int clocksource_unbind(struct clocksource *cs)
+{
+	unsigned long flags;
+
+	if (clocksource_is_watchdog(cs)) {
+		/* Select and try to install a replacement watchdog. */
+		clocksource_select_watchdog(true);
+		if (clocksource_is_watchdog(cs))
+			return -EBUSY;
+	}
+
+	if (cs == curr_clocksource) {
+		/* Select and try to install a replacement clock source */
+		clocksource_select_fallback();
+		if (curr_clocksource == cs)
+			return -EBUSY;
+	}
+
+	if (clocksource_is_suspend(cs)) {
+		/*
+		 * Select and try to install a replacement suspend clocksource.
+		 * If no replacement suspend clocksource, we will just let the
+		 * clocksource go and have no suspend clocksource.
+		 */
+		clocksource_suspend_select(true);
+	}
+
+	clocksource_watchdog_lock(&flags);
+	clocksource_dequeue_watchdog(cs);
+	list_del_init(&cs->list);
+	clocksource_watchdog_unlock(&flags);
+
+	return 0;
+}
+
+/**
+ * clocksource_unregister - remove a registered clocksource
+ * @cs:	clocksource to be unregistered
+ */
+int clocksource_unregister(struct clocksource *cs)
+{
+	int ret = 0;
+
+	mutex_lock(&clocksource_mutex);
+	if (!list_empty(&cs->list))
+		ret = clocksource_unbind(cs);
+	mutex_unlock(&clocksource_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(clocksource_unregister);
+
+#ifdef CONFIG_SYSFS
+/**
+ * current_clocksource_show - sysfs interface for current clocksource
+ * @dev:	unused
+ * @attr:	unused
+ * @buf:	char buffer to be filled with clocksource list
+ *
+ * Provides sysfs interface for listing current clocksource.
+ */
+static ssize_t current_clocksource_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	ssize_t count = 0;
+
+	mutex_lock(&clocksource_mutex);
+	count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
+	mutex_unlock(&clocksource_mutex);
+
+	return count;
+}
+
+ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
+{
+	size_t ret = cnt;
+
+	/* strings from sysfs write are not 0 terminated! */
+	if (!cnt || cnt >= CS_NAME_LEN)
+		return -EINVAL;
+
+	/* strip of \n: */
+	if (buf[cnt-1] == '\n')
+		cnt--;
+	if (cnt > 0)
+		memcpy(dst, buf, cnt);
+	dst[cnt] = 0;
+	return ret;
+}
+
+/**
+ * current_clocksource_store - interface for manually overriding clocksource
+ * @dev:	unused
+ * @attr:	unused
+ * @buf:	name of override clocksource
+ * @count:	length of buffer
+ *
+ * Takes input from sysfs interface for manually overriding the default
+ * clocksource selection.
+ */
+static ssize_t current_clocksource_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	ssize_t ret;
+
+	mutex_lock(&clocksource_mutex);
+
+	ret = sysfs_get_uname(buf, override_name, count);
+	if (ret >= 0)
+		clocksource_select();
+
+	mutex_unlock(&clocksource_mutex);
+
+	return ret;
+}
+static DEVICE_ATTR_RW(current_clocksource);
+
+/**
+ * unbind_clocksource_store - interface for manually unbinding clocksource
+ * @dev:	unused
+ * @attr:	unused
+ * @buf:	unused
+ * @count:	length of buffer
+ *
+ * Takes input from sysfs interface for manually unbinding a clocksource.
+ */
+static ssize_t unbind_clocksource_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct clocksource *cs;
+	char name[CS_NAME_LEN];
+	ssize_t ret;
+
+	ret = sysfs_get_uname(buf, name, count);
+	if (ret < 0)
+		return ret;
+
+	ret = -ENODEV;
+	mutex_lock(&clocksource_mutex);
+	list_for_each_entry(cs, &clocksource_list, list) {
+		if (strcmp(cs->name, name))
+			continue;
+		ret = clocksource_unbind(cs);
+		break;
+	}
+	mutex_unlock(&clocksource_mutex);
+
+	return ret ? ret : count;
+}
+static DEVICE_ATTR_WO(unbind_clocksource);
+
+/**
+ * available_clocksource_show - sysfs interface for listing clocksource
+ * @dev:	unused
+ * @attr:	unused
+ * @buf:	char buffer to be filled with clocksource list
+ *
+ * Provides sysfs interface for listing registered clocksources
+ */
+static ssize_t available_clocksource_show(struct device *dev,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct clocksource *src;
+	ssize_t count = 0;
+
+	mutex_lock(&clocksource_mutex);
+	list_for_each_entry(src, &clocksource_list, list) {
+		/*
+		 * Don't show non-HRES clocksource if the tick code is
+		 * in one shot mode (highres=on or nohz=on)
+		 */
+		if (!tick_oneshot_mode_active() ||
+		    (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+			count += snprintf(buf + count,
+				  max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
+				  "%s ", src->name);
+	}
+	mutex_unlock(&clocksource_mutex);
+
+	count += snprintf(buf + count,
+			  max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
+
+	return count;
+}
+static DEVICE_ATTR_RO(available_clocksource);
+
+static struct attribute *clocksource_attrs[] = {
+	&dev_attr_current_clocksource.attr,
+	&dev_attr_unbind_clocksource.attr,
+	&dev_attr_available_clocksource.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(clocksource);
+
+static struct bus_type clocksource_subsys = {
+	.name = "clocksource",
+	.dev_name = "clocksource",
+};
+
+static struct device device_clocksource = {
+	.id	= 0,
+	.bus	= &clocksource_subsys,
+	.groups	= clocksource_groups,
+};
+
+static int __init init_clocksource_sysfs(void)
+{
+	int error = subsys_system_register(&clocksource_subsys, NULL);
+
+	if (!error)
+		error = device_register(&device_clocksource);
+
+	return error;
+}
+
+device_initcall(init_clocksource_sysfs);
+#endif /* CONFIG_SYSFS */
+
+/**
+ * boot_override_clocksource - boot clock override
+ * @str:	override name
+ *
+ * Takes a clocksource= boot argument and uses it
+ * as the clocksource override name.
+ */
+static int __init boot_override_clocksource(char* str)
+{
+	mutex_lock(&clocksource_mutex);
+	if (str)
+		strscpy(override_name, str, sizeof(override_name));
+	mutex_unlock(&clocksource_mutex);
+	return 1;
+}
+
+__setup("clocksource=", boot_override_clocksource);
+
+/**
+ * boot_override_clock - Compatibility layer for deprecated boot option
+ * @str:	override name
+ *
+ * DEPRECATED! Takes a clock= boot argument and uses it
+ * as the clocksource override name
+ */
+static int __init boot_override_clock(char* str)
+{
+	if (!strcmp(str, "pmtmr")) {
+		pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
+		return boot_override_clocksource("acpi_pm");
+	}
+	pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
+	return boot_override_clocksource(str);
+}
+
+__setup("clock=", boot_override_clock);
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
new file mode 100644
index 0000000000..760793998c
--- /dev/null
+++ b/kernel/time/hrtimer.c
@@ -0,0 +1,2391 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
+ *
+ *  High-resolution kernel timers
+ *
+ *  In contrast to the low-resolution timeout API, aka timer wheel,
+ *  hrtimers provide finer resolution and accuracy depending on system
+ *  configuration and capabilities.
+ *
+ *  Started by: Thomas Gleixner and Ingo Molnar
+ *
+ *  Credits:
+ *	Based on the original timer wheel code
+ *
+ *	Help, testing, suggestions, bugfixes, improvements were
+ *	provided by:
+ *
+ *	George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
+ *	et. al.
+ */
+
+#include <linux/cpu.h>
+#include <linux/export.h>
+#include <linux/percpu.h>
+#include <linux/hrtimer.h>
+#include <linux/notifier.h>
+#include <linux/syscalls.h>
+#include <linux/interrupt.h>
+#include <linux/tick.h>
+#include <linux/err.h>
+#include <linux/debugobjects.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/sysctl.h>
+#include <linux/sched/rt.h>
+#include <linux/sched/deadline.h>
+#include <linux/sched/nohz.h>
+#include <linux/sched/debug.h>
+#include <linux/timer.h>
+#include <linux/freezer.h>
+#include <linux/compat.h>
+
+#include <linux/uaccess.h>
+
+#include <trace/events/timer.h>
+
+#include "tick-internal.h"
+
+/*
+ * Masks for selecting the soft and hard context timers from
+ * cpu_base->active
+ */
+#define MASK_SHIFT		(HRTIMER_BASE_MONOTONIC_SOFT)
+#define HRTIMER_ACTIVE_HARD	((1U << MASK_SHIFT) - 1)
+#define HRTIMER_ACTIVE_SOFT	(HRTIMER_ACTIVE_HARD << MASK_SHIFT)
+#define HRTIMER_ACTIVE_ALL	(HRTIMER_ACTIVE_SOFT | HRTIMER_ACTIVE_HARD)
+
+/*
+ * The timer bases:
+ *
+ * There are more clockids than hrtimer bases. Thus, we index
+ * into the timer bases by the hrtimer_base_type enum. When trying
+ * to reach a base using a clockid, hrtimer_clockid_to_base()
+ * is used to convert from clockid to the proper hrtimer_base_type.
+ */
+DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
+{
+	.lock = __RAW_SPIN_LOCK_UNLOCKED(hrtimer_bases.lock),
+	.clock_base =
+	{
+		{
+			.index = HRTIMER_BASE_MONOTONIC,
+			.clockid = CLOCK_MONOTONIC,
+			.get_time = &ktime_get,
+		},
+		{
+			.index = HRTIMER_BASE_REALTIME,
+			.clockid = CLOCK_REALTIME,
+			.get_time = &ktime_get_real,
+		},
+		{
+			.index = HRTIMER_BASE_BOOTTIME,
+			.clockid = CLOCK_BOOTTIME,
+			.get_time = &ktime_get_boottime,
+		},
+		{
+			.index = HRTIMER_BASE_TAI,
+			.clockid = CLOCK_TAI,
+			.get_time = &ktime_get_clocktai,
+		},
+		{
+			.index = HRTIMER_BASE_MONOTONIC_SOFT,
+			.clockid = CLOCK_MONOTONIC,
+			.get_time = &ktime_get,
+		},
+		{
+			.index = HRTIMER_BASE_REALTIME_SOFT,
+			.clockid = CLOCK_REALTIME,
+			.get_time = &ktime_get_real,
+		},
+		{
+			.index = HRTIMER_BASE_BOOTTIME_SOFT,
+			.clockid = CLOCK_BOOTTIME,
+			.get_time = &ktime_get_boottime,
+		},
+		{
+			.index = HRTIMER_BASE_TAI_SOFT,
+			.clockid = CLOCK_TAI,
+			.get_time = &ktime_get_clocktai,
+		},
+	}
+};
+
+static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
+	/* Make sure we catch unsupported clockids */
+	[0 ... MAX_CLOCKS - 1]	= HRTIMER_MAX_CLOCK_BASES,
+
+	[CLOCK_REALTIME]	= HRTIMER_BASE_REALTIME,
+	[CLOCK_MONOTONIC]	= HRTIMER_BASE_MONOTONIC,
+	[CLOCK_BOOTTIME]	= HRTIMER_BASE_BOOTTIME,
+	[CLOCK_TAI]		= HRTIMER_BASE_TAI,
+};
+
+/*
+ * Functions and macros which are different for UP/SMP systems are kept in a
+ * single place
+ */
+#ifdef CONFIG_SMP
+
+/*
+ * We require the migration_base for lock_hrtimer_base()/switch_hrtimer_base()
+ * such that hrtimer_callback_running() can unconditionally dereference
+ * timer->base->cpu_base
+ */
+static struct hrtimer_cpu_base migration_cpu_base = {
+	.clock_base = { {
+		.cpu_base = &migration_cpu_base,
+		.seq      = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
+						     &migration_cpu_base.lock),
+	}, },
+};
+
+#define migration_base	migration_cpu_base.clock_base[0]
+
+static inline bool is_migration_base(struct hrtimer_clock_base *base)
+{
+	return base == &migration_base;
+}
+
+/*
+ * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
+ * means that all timers which are tied to this base via timer->base are
+ * locked, and the base itself is locked too.
+ *
+ * So __run_timers/migrate_timers can safely modify all timers which could
+ * be found on the lists/queues.
+ *
+ * When the timer's base is locked, and the timer removed from list, it is
+ * possible to set timer->base = &migration_base and drop the lock: the timer
+ * remains locked.
+ */
+static
+struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
+					     unsigned long *flags)
+	__acquires(&timer->base->lock)
+{
+	struct hrtimer_clock_base *base;
+
+	for (;;) {
+		base = READ_ONCE(timer->base);
+		if (likely(base != &migration_base)) {
+			raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
+			if (likely(base == timer->base))
+				return base;
+			/* The timer has migrated to another CPU: */
+			raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
+		}
+		cpu_relax();
+	}
+}
+
+/*
+ * We do not migrate the timer when it is expiring before the next
+ * event on the target cpu. When high resolution is enabled, we cannot
+ * reprogram the target cpu hardware and we would cause it to fire
+ * late. To keep it simple, we handle the high resolution enabled and
+ * disabled case similar.
+ *
+ * Called with cpu_base->lock of target cpu held.
+ */
+static int
+hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base)
+{
+	ktime_t expires;
+
+	expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
+	return expires < new_base->cpu_base->expires_next;
+}
+
+static inline
+struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
+					 int pinned)
+{
+#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
+	if (static_branch_likely(&timers_migration_enabled) && !pinned)
+		return &per_cpu(hrtimer_bases, get_nohz_timer_target());
+#endif
+	return base;
+}
+
+/*
+ * We switch the timer base to a power-optimized selected CPU target,
+ * if:
+ *	- NO_HZ_COMMON is enabled
+ *	- timer migration is enabled
+ *	- the timer callback is not running
+ *	- the timer is not the first expiring timer on the new target
+ *
+ * If one of the above requirements is not fulfilled we move the timer
+ * to the current CPU or leave it on the previously assigned CPU if
+ * the timer callback is currently running.
+ */
+static inline struct hrtimer_clock_base *
+switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
+		    int pinned)
+{
+	struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
+	struct hrtimer_clock_base *new_base;
+	int basenum = base->index;
+
+	this_cpu_base = this_cpu_ptr(&hrtimer_bases);
+	new_cpu_base = get_target_base(this_cpu_base, pinned);
+again:
+	new_base = &new_cpu_base->clock_base[basenum];
+
+	if (base != new_base) {
+		/*
+		 * We are trying to move timer to new_base.
+		 * However we can't change timer's base while it is running,
+		 * so we keep it on the same CPU. No hassle vs. reprogramming
+		 * the event source in the high resolution case. The softirq
+		 * code will take care of this when the timer function has
+		 * completed. There is no conflict as we hold the lock until
+		 * the timer is enqueued.
+		 */
+		if (unlikely(hrtimer_callback_running(timer)))
+			return base;
+
+		/* See the comment in lock_hrtimer_base() */
+		WRITE_ONCE(timer->base, &migration_base);
+		raw_spin_unlock(&base->cpu_base->lock);
+		raw_spin_lock(&new_base->cpu_base->lock);
+
+		if (new_cpu_base != this_cpu_base &&
+		    hrtimer_check_target(timer, new_base)) {
+			raw_spin_unlock(&new_base->cpu_base->lock);
+			raw_spin_lock(&base->cpu_base->lock);
+			new_cpu_base = this_cpu_base;
+			WRITE_ONCE(timer->base, base);
+			goto again;
+		}
+		WRITE_ONCE(timer->base, new_base);
+	} else {
+		if (new_cpu_base != this_cpu_base &&
+		    hrtimer_check_target(timer, new_base)) {
+			new_cpu_base = this_cpu_base;
+			goto again;
+		}
+	}
+	return new_base;
+}
+
+#else /* CONFIG_SMP */
+
+static inline bool is_migration_base(struct hrtimer_clock_base *base)
+{
+	return false;
+}
+
+static inline struct hrtimer_clock_base *
+lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
+	__acquires(&timer->base->cpu_base->lock)
+{
+	struct hrtimer_clock_base *base = timer->base;
+
+	raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
+
+	return base;
+}
+
+# define switch_hrtimer_base(t, b, p)	(b)
+
+#endif	/* !CONFIG_SMP */
+
+/*
+ * Functions for the union type storage format of ktime_t which are
+ * too large for inlining:
+ */
+#if BITS_PER_LONG < 64
+/*
+ * Divide a ktime value by a nanosecond value
+ */
+s64 __ktime_divns(const ktime_t kt, s64 div)
+{
+	int sft = 0;
+	s64 dclc;
+	u64 tmp;
+
+	dclc = ktime_to_ns(kt);
+	tmp = dclc < 0 ? -dclc : dclc;
+
+	/* Make sure the divisor is less than 2^32: */
+	while (div >> 32) {
+		sft++;
+		div >>= 1;
+	}
+	tmp >>= sft;
+	do_div(tmp, (u32) div);
+	return dclc < 0 ? -tmp : tmp;
+}
+EXPORT_SYMBOL_GPL(__ktime_divns);
+#endif /* BITS_PER_LONG >= 64 */
+
+/*
+ * Add two ktime values and do a safety check for overflow:
+ */
+ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
+{
+	ktime_t res = ktime_add_unsafe(lhs, rhs);
+
+	/*
+	 * We use KTIME_SEC_MAX here, the maximum timeout which we can
+	 * return to user space in a timespec:
+	 */
+	if (res < 0 || res < lhs || res < rhs)
+		res = ktime_set(KTIME_SEC_MAX, 0);
+
+	return res;
+}
+
+EXPORT_SYMBOL_GPL(ktime_add_safe);
+
+#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
+
+static const struct debug_obj_descr hrtimer_debug_descr;
+
+static void *hrtimer_debug_hint(void *addr)
+{
+	return ((struct hrtimer *) addr)->function;
+}
+
+/*
+ * fixup_init is called when:
+ * - an active object is initialized
+ */
+static bool hrtimer_fixup_init(void *addr, enum debug_obj_state state)
+{
+	struct hrtimer *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		hrtimer_cancel(timer);
+		debug_object_init(timer, &hrtimer_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * fixup_activate is called when:
+ * - an active object is activated
+ * - an unknown non-static object is activated
+ */
+static bool hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
+{
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		WARN_ON(1);
+		fallthrough;
+	default:
+		return false;
+	}
+}
+
+/*
+ * fixup_free is called when:
+ * - an active object is freed
+ */
+static bool hrtimer_fixup_free(void *addr, enum debug_obj_state state)
+{
+	struct hrtimer *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		hrtimer_cancel(timer);
+		debug_object_free(timer, &hrtimer_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct debug_obj_descr hrtimer_debug_descr = {
+	.name		= "hrtimer",
+	.debug_hint	= hrtimer_debug_hint,
+	.fixup_init	= hrtimer_fixup_init,
+	.fixup_activate	= hrtimer_fixup_activate,
+	.fixup_free	= hrtimer_fixup_free,
+};
+
+static inline void debug_hrtimer_init(struct hrtimer *timer)
+{
+	debug_object_init(timer, &hrtimer_debug_descr);
+}
+
+static inline void debug_hrtimer_activate(struct hrtimer *timer,
+					  enum hrtimer_mode mode)
+{
+	debug_object_activate(timer, &hrtimer_debug_descr);
+}
+
+static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
+{
+	debug_object_deactivate(timer, &hrtimer_debug_descr);
+}
+
+static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
+			   enum hrtimer_mode mode);
+
+void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
+			   enum hrtimer_mode mode)
+{
+	debug_object_init_on_stack(timer, &hrtimer_debug_descr);
+	__hrtimer_init(timer, clock_id, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_init_on_stack);
+
+static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
+				   clockid_t clock_id, enum hrtimer_mode mode);
+
+void hrtimer_init_sleeper_on_stack(struct hrtimer_sleeper *sl,
+				   clockid_t clock_id, enum hrtimer_mode mode)
+{
+	debug_object_init_on_stack(&sl->timer, &hrtimer_debug_descr);
+	__hrtimer_init_sleeper(sl, clock_id, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_init_sleeper_on_stack);
+
+void destroy_hrtimer_on_stack(struct hrtimer *timer)
+{
+	debug_object_free(timer, &hrtimer_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_hrtimer_on_stack);
+
+#else
+
+static inline void debug_hrtimer_init(struct hrtimer *timer) { }
+static inline void debug_hrtimer_activate(struct hrtimer *timer,
+					  enum hrtimer_mode mode) { }
+static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
+#endif
+
+static inline void
+debug_init(struct hrtimer *timer, clockid_t clockid,
+	   enum hrtimer_mode mode)
+{
+	debug_hrtimer_init(timer);
+	trace_hrtimer_init(timer, clockid, mode);
+}
+
+static inline void debug_activate(struct hrtimer *timer,
+				  enum hrtimer_mode mode)
+{
+	debug_hrtimer_activate(timer, mode);
+	trace_hrtimer_start(timer, mode);
+}
+
+static inline void debug_deactivate(struct hrtimer *timer)
+{
+	debug_hrtimer_deactivate(timer);
+	trace_hrtimer_cancel(timer);
+}
+
+static struct hrtimer_clock_base *
+__next_base(struct hrtimer_cpu_base *cpu_base, unsigned int *active)
+{
+	unsigned int idx;
+
+	if (!*active)
+		return NULL;
+
+	idx = __ffs(*active);
+	*active &= ~(1U << idx);
+
+	return &cpu_base->clock_base[idx];
+}
+
+#define for_each_active_base(base, cpu_base, active)	\
+	while ((base = __next_base((cpu_base), &(active))))
+
+static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
+					 const struct hrtimer *exclude,
+					 unsigned int active,
+					 ktime_t expires_next)
+{
+	struct hrtimer_clock_base *base;
+	ktime_t expires;
+
+	for_each_active_base(base, cpu_base, active) {
+		struct timerqueue_node *next;
+		struct hrtimer *timer;
+
+		next = timerqueue_getnext(&base->active);
+		timer = container_of(next, struct hrtimer, node);
+		if (timer == exclude) {
+			/* Get to the next timer in the queue. */
+			next = timerqueue_iterate_next(next);
+			if (!next)
+				continue;
+
+			timer = container_of(next, struct hrtimer, node);
+		}
+		expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
+		if (expires < expires_next) {
+			expires_next = expires;
+
+			/* Skip cpu_base update if a timer is being excluded. */
+			if (exclude)
+				continue;
+
+			if (timer->is_soft)
+				cpu_base->softirq_next_timer = timer;
+			else
+				cpu_base->next_timer = timer;
+		}
+	}
+	/*
+	 * clock_was_set() might have changed base->offset of any of
+	 * the clock bases so the result might be negative. Fix it up
+	 * to prevent a false positive in clockevents_program_event().
+	 */
+	if (expires_next < 0)
+		expires_next = 0;
+	return expires_next;
+}
+
+/*
+ * Recomputes cpu_base::*next_timer and returns the earliest expires_next
+ * but does not set cpu_base::*expires_next, that is done by
+ * hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
+ * cpu_base::*expires_next right away, reprogramming logic would no longer
+ * work.
+ *
+ * When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
+ * those timers will get run whenever the softirq gets handled, at the end of
+ * hrtimer_run_softirq(), hrtimer_update_softirq_timer() will re-add these bases.
+ *
+ * Therefore softirq values are those from the HRTIMER_ACTIVE_SOFT clock bases.
+ * The !softirq values are the minima across HRTIMER_ACTIVE_ALL, unless an actual
+ * softirq is pending, in which case they're the minima of HRTIMER_ACTIVE_HARD.
+ *
+ * @active_mask must be one of:
+ *  - HRTIMER_ACTIVE_ALL,
+ *  - HRTIMER_ACTIVE_SOFT, or
+ *  - HRTIMER_ACTIVE_HARD.
+ */
+static ktime_t
+__hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_mask)
+{
+	unsigned int active;
+	struct hrtimer *next_timer = NULL;
+	ktime_t expires_next = KTIME_MAX;
+
+	if (!cpu_base->softirq_activated && (active_mask & HRTIMER_ACTIVE_SOFT)) {
+		active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
+		cpu_base->softirq_next_timer = NULL;
+		expires_next = __hrtimer_next_event_base(cpu_base, NULL,
+							 active, KTIME_MAX);
+
+		next_timer = cpu_base->softirq_next_timer;
+	}
+
+	if (active_mask & HRTIMER_ACTIVE_HARD) {
+		active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
+		cpu_base->next_timer = next_timer;
+		expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
+							 expires_next);
+	}
+
+	return expires_next;
+}
+
+static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
+{
+	ktime_t expires_next, soft = KTIME_MAX;
+
+	/*
+	 * If the soft interrupt has already been activated, ignore the
+	 * soft bases. They will be handled in the already raised soft
+	 * interrupt.
+	 */
+	if (!cpu_base->softirq_activated) {
+		soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
+		/*
+		 * Update the soft expiry time. clock_settime() might have
+		 * affected it.
+		 */
+		cpu_base->softirq_expires_next = soft;
+	}
+
+	expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
+	/*
+	 * If a softirq timer is expiring first, update cpu_base->next_timer
+	 * and program the hardware with the soft expiry time.
+	 */
+	if (expires_next > soft) {
+		cpu_base->next_timer = cpu_base->softirq_next_timer;
+		expires_next = soft;
+	}
+
+	return expires_next;
+}
+
+static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
+{
+	ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
+	ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
+	ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
+
+	ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
+					    offs_real, offs_boot, offs_tai);
+
+	base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
+	base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
+	base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
+
+	return now;
+}
+
+/*
+ * Is the high resolution mode active ?
+ */
+static inline int __hrtimer_hres_active(struct hrtimer_cpu_base *cpu_base)
+{
+	return IS_ENABLED(CONFIG_HIGH_RES_TIMERS) ?
+		cpu_base->hres_active : 0;
+}
+
+static inline int hrtimer_hres_active(void)
+{
+	return __hrtimer_hres_active(this_cpu_ptr(&hrtimer_bases));
+}
+
+static void __hrtimer_reprogram(struct hrtimer_cpu_base *cpu_base,
+				struct hrtimer *next_timer,
+				ktime_t expires_next)
+{
+	cpu_base->expires_next = expires_next;
+
+	/*
+	 * If hres is not active, hardware does not have to be
+	 * reprogrammed yet.
+	 *
+	 * If a hang was detected in the last timer interrupt then we
+	 * leave the hang delay active in the hardware. We want the
+	 * system to make progress. That also prevents the following
+	 * scenario:
+	 * T1 expires 50ms from now
+	 * T2 expires 5s from now
+	 *
+	 * T1 is removed, so this code is called and would reprogram
+	 * the hardware to 5s from now. Any hrtimer_start after that
+	 * will not reprogram the hardware due to hang_detected being
+	 * set. So we'd effectively block all timers until the T2 event
+	 * fires.
+	 */
+	if (!__hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
+		return;
+
+	tick_program_event(expires_next, 1);
+}
+
+/*
+ * Reprogram the event source with checking both queues for the
+ * next event
+ * Called with interrupts disabled and base->lock held
+ */
+static void
+hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
+{
+	ktime_t expires_next;
+
+	expires_next = hrtimer_update_next_event(cpu_base);
+
+	if (skip_equal && expires_next == cpu_base->expires_next)
+		return;
+
+	__hrtimer_reprogram(cpu_base, cpu_base->next_timer, expires_next);
+}
+
+/* High resolution timer related functions */
+#ifdef CONFIG_HIGH_RES_TIMERS
+
+/*
+ * High resolution timer enabled ?
+ */
+static bool hrtimer_hres_enabled __read_mostly  = true;
+unsigned int hrtimer_resolution __read_mostly = LOW_RES_NSEC;
+EXPORT_SYMBOL_GPL(hrtimer_resolution);
+
+/*
+ * Enable / Disable high resolution mode
+ */
+static int __init setup_hrtimer_hres(char *str)
+{
+	return (kstrtobool(str, &hrtimer_hres_enabled) == 0);
+}
+
+__setup("highres=", setup_hrtimer_hres);
+
+/*
+ * hrtimer_high_res_enabled - query, if the highres mode is enabled
+ */
+static inline int hrtimer_is_hres_enabled(void)
+{
+	return hrtimer_hres_enabled;
+}
+
+static void retrigger_next_event(void *arg);
+
+/*
+ * Switch to high resolution mode
+ */
+static void hrtimer_switch_to_hres(void)
+{
+	struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
+
+	if (tick_init_highres()) {
+		pr_warn("Could not switch to high resolution mode on CPU %u\n",
+			base->cpu);
+		return;
+	}
+	base->hres_active = 1;
+	hrtimer_resolution = HIGH_RES_NSEC;
+
+	tick_setup_sched_timer();
+	/* "Retrigger" the interrupt to get things going */
+	retrigger_next_event(NULL);
+}
+
+#else
+
+static inline int hrtimer_is_hres_enabled(void) { return 0; }
+static inline void hrtimer_switch_to_hres(void) { }
+
+#endif /* CONFIG_HIGH_RES_TIMERS */
+/*
+ * Retrigger next event is called after clock was set with interrupts
+ * disabled through an SMP function call or directly from low level
+ * resume code.
+ *
+ * This is only invoked when:
+ *	- CONFIG_HIGH_RES_TIMERS is enabled.
+ *	- CONFIG_NOHZ_COMMON is enabled
+ *
+ * For the other cases this function is empty and because the call sites
+ * are optimized out it vanishes as well, i.e. no need for lots of
+ * #ifdeffery.
+ */
+static void retrigger_next_event(void *arg)
+{
+	struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
+
+	/*
+	 * When high resolution mode or nohz is active, then the offsets of
+	 * CLOCK_REALTIME/TAI/BOOTTIME have to be updated. Otherwise the
+	 * next tick will take care of that.
+	 *
+	 * If high resolution mode is active then the next expiring timer
+	 * must be reevaluated and the clock event device reprogrammed if
+	 * necessary.
+	 *
+	 * In the NOHZ case the update of the offset and the reevaluation
+	 * of the next expiring timer is enough. The return from the SMP
+	 * function call will take care of the reprogramming in case the
+	 * CPU was in a NOHZ idle sleep.
+	 */
+	if (!__hrtimer_hres_active(base) && !tick_nohz_active)
+		return;
+
+	raw_spin_lock(&base->lock);
+	hrtimer_update_base(base);
+	if (__hrtimer_hres_active(base))
+		hrtimer_force_reprogram(base, 0);
+	else
+		hrtimer_update_next_event(base);
+	raw_spin_unlock(&base->lock);
+}
+
+/*
+ * When a timer is enqueued and expires earlier than the already enqueued
+ * timers, we have to check, whether it expires earlier than the timer for
+ * which the clock event device was armed.
+ *
+ * Called with interrupts disabled and base->cpu_base.lock held
+ */
+static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	struct hrtimer_clock_base *base = timer->base;
+	ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
+
+	WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
+
+	/*
+	 * CLOCK_REALTIME timer might be requested with an absolute
+	 * expiry time which is less than base->offset. Set it to 0.
+	 */
+	if (expires < 0)
+		expires = 0;
+
+	if (timer->is_soft) {
+		/*
+		 * soft hrtimer could be started on a remote CPU. In this
+		 * case softirq_expires_next needs to be updated on the
+		 * remote CPU. The soft hrtimer will not expire before the
+		 * first hard hrtimer on the remote CPU -
+		 * hrtimer_check_target() prevents this case.
+		 */
+		struct hrtimer_cpu_base *timer_cpu_base = base->cpu_base;
+
+		if (timer_cpu_base->softirq_activated)
+			return;
+
+		if (!ktime_before(expires, timer_cpu_base->softirq_expires_next))
+			return;
+
+		timer_cpu_base->softirq_next_timer = timer;
+		timer_cpu_base->softirq_expires_next = expires;
+
+		if (!ktime_before(expires, timer_cpu_base->expires_next) ||
+		    !reprogram)
+			return;
+	}
+
+	/*
+	 * If the timer is not on the current cpu, we cannot reprogram
+	 * the other cpus clock event device.
+	 */
+	if (base->cpu_base != cpu_base)
+		return;
+
+	if (expires >= cpu_base->expires_next)
+		return;
+
+	/*
+	 * If the hrtimer interrupt is running, then it will reevaluate the
+	 * clock bases and reprogram the clock event device.
+	 */
+	if (cpu_base->in_hrtirq)
+		return;
+
+	cpu_base->next_timer = timer;
+
+	__hrtimer_reprogram(cpu_base, timer, expires);
+}
+
+static bool update_needs_ipi(struct hrtimer_cpu_base *cpu_base,
+			     unsigned int active)
+{
+	struct hrtimer_clock_base *base;
+	unsigned int seq;
+	ktime_t expires;
+
+	/*
+	 * Update the base offsets unconditionally so the following
+	 * checks whether the SMP function call is required works.
+	 *
+	 * The update is safe even when the remote CPU is in the hrtimer
+	 * interrupt or the hrtimer soft interrupt and expiring affected
+	 * bases. Either it will see the update before handling a base or
+	 * it will see it when it finishes the processing and reevaluates
+	 * the next expiring timer.
+	 */
+	seq = cpu_base->clock_was_set_seq;
+	hrtimer_update_base(cpu_base);
+
+	/*
+	 * If the sequence did not change over the update then the
+	 * remote CPU already handled it.
+	 */
+	if (seq == cpu_base->clock_was_set_seq)
+		return false;
+
+	/*
+	 * If the remote CPU is currently handling an hrtimer interrupt, it
+	 * will reevaluate the first expiring timer of all clock bases
+	 * before reprogramming. Nothing to do here.
+	 */
+	if (cpu_base->in_hrtirq)
+		return false;
+
+	/*
+	 * Walk the affected clock bases and check whether the first expiring
+	 * timer in a clock base is moving ahead of the first expiring timer of
+	 * @cpu_base. If so, the IPI must be invoked because per CPU clock
+	 * event devices cannot be remotely reprogrammed.
+	 */
+	active &= cpu_base->active_bases;
+
+	for_each_active_base(base, cpu_base, active) {
+		struct timerqueue_node *next;
+
+		next = timerqueue_getnext(&base->active);
+		expires = ktime_sub(next->expires, base->offset);
+		if (expires < cpu_base->expires_next)
+			return true;
+
+		/* Extra check for softirq clock bases */
+		if (base->clockid < HRTIMER_BASE_MONOTONIC_SOFT)
+			continue;
+		if (cpu_base->softirq_activated)
+			continue;
+		if (expires < cpu_base->softirq_expires_next)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * Clock was set. This might affect CLOCK_REALTIME, CLOCK_TAI and
+ * CLOCK_BOOTTIME (for late sleep time injection).
+ *
+ * This requires to update the offsets for these clocks
+ * vs. CLOCK_MONOTONIC. When high resolution timers are enabled, then this
+ * also requires to eventually reprogram the per CPU clock event devices
+ * when the change moves an affected timer ahead of the first expiring
+ * timer on that CPU. Obviously remote per CPU clock event devices cannot
+ * be reprogrammed. The other reason why an IPI has to be sent is when the
+ * system is in !HIGH_RES and NOHZ mode. The NOHZ mode updates the offsets
+ * in the tick, which obviously might be stopped, so this has to bring out
+ * the remote CPU which might sleep in idle to get this sorted.
+ */
+void clock_was_set(unsigned int bases)
+{
+	struct hrtimer_cpu_base *cpu_base = raw_cpu_ptr(&hrtimer_bases);
+	cpumask_var_t mask;
+	int cpu;
+
+	if (!__hrtimer_hres_active(cpu_base) && !tick_nohz_active)
+		goto out_timerfd;
+
+	if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
+		on_each_cpu(retrigger_next_event, NULL, 1);
+		goto out_timerfd;
+	}
+
+	/* Avoid interrupting CPUs if possible */
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		unsigned long flags;
+
+		cpu_base = &per_cpu(hrtimer_bases, cpu);
+		raw_spin_lock_irqsave(&cpu_base->lock, flags);
+
+		if (update_needs_ipi(cpu_base, bases))
+			cpumask_set_cpu(cpu, mask);
+
+		raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+	}
+
+	preempt_disable();
+	smp_call_function_many(mask, retrigger_next_event, NULL, 1);
+	preempt_enable();
+	cpus_read_unlock();
+	free_cpumask_var(mask);
+
+out_timerfd:
+	timerfd_clock_was_set();
+}
+
+static void clock_was_set_work(struct work_struct *work)
+{
+	clock_was_set(CLOCK_SET_WALL);
+}
+
+static DECLARE_WORK(hrtimer_work, clock_was_set_work);
+
+/*
+ * Called from timekeeping code to reprogram the hrtimer interrupt device
+ * on all cpus and to notify timerfd.
+ */
+void clock_was_set_delayed(void)
+{
+	schedule_work(&hrtimer_work);
+}
+
+/*
+ * Called during resume either directly from via timekeeping_resume()
+ * or in the case of s2idle from tick_unfreeze() to ensure that the
+ * hrtimers are up to date.
+ */
+void hrtimers_resume_local(void)
+{
+	lockdep_assert_irqs_disabled();
+	/* Retrigger on the local CPU */
+	retrigger_next_event(NULL);
+}
+
+/*
+ * Counterpart to lock_hrtimer_base above:
+ */
+static inline
+void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
+	__releases(&timer->base->cpu_base->lock)
+{
+	raw_spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
+}
+
+/**
+ * hrtimer_forward - forward the timer expiry
+ * @timer:	hrtimer to forward
+ * @now:	forward past this time
+ * @interval:	the interval to forward
+ *
+ * Forward the timer expiry so it will expire in the future.
+ * Returns the number of overruns.
+ *
+ * Can be safely called from the callback function of @timer. If
+ * called from other contexts @timer must neither be enqueued nor
+ * running the callback and the caller needs to take care of
+ * serialization.
+ *
+ * Note: This only updates the timer expiry value and does not requeue
+ * the timer.
+ */
+u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
+{
+	u64 orun = 1;
+	ktime_t delta;
+
+	delta = ktime_sub(now, hrtimer_get_expires(timer));
+
+	if (delta < 0)
+		return 0;
+
+	if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
+		return 0;
+
+	if (interval < hrtimer_resolution)
+		interval = hrtimer_resolution;
+
+	if (unlikely(delta >= interval)) {
+		s64 incr = ktime_to_ns(interval);
+
+		orun = ktime_divns(delta, incr);
+		hrtimer_add_expires_ns(timer, incr * orun);
+		if (hrtimer_get_expires_tv64(timer) > now)
+			return orun;
+		/*
+		 * This (and the ktime_add() below) is the
+		 * correction for exact:
+		 */
+		orun++;
+	}
+	hrtimer_add_expires(timer, interval);
+
+	return orun;
+}
+EXPORT_SYMBOL_GPL(hrtimer_forward);
+
+/*
+ * enqueue_hrtimer - internal function to (re)start a timer
+ *
+ * The timer is inserted in expiry order. Insertion into the
+ * red black tree is O(log(n)). Must hold the base lock.
+ *
+ * Returns 1 when the new timer is the leftmost timer in the tree.
+ */
+static int enqueue_hrtimer(struct hrtimer *timer,
+			   struct hrtimer_clock_base *base,
+			   enum hrtimer_mode mode)
+{
+	debug_activate(timer, mode);
+
+	base->cpu_base->active_bases |= 1 << base->index;
+
+	/* Pairs with the lockless read in hrtimer_is_queued() */
+	WRITE_ONCE(timer->state, HRTIMER_STATE_ENQUEUED);
+
+	return timerqueue_add(&base->active, &timer->node);
+}
+
+/*
+ * __remove_hrtimer - internal function to remove a timer
+ *
+ * Caller must hold the base lock.
+ *
+ * High resolution timer mode reprograms the clock event device when the
+ * timer is the one which expires next. The caller can disable this by setting
+ * reprogram to zero. This is useful, when the context does a reprogramming
+ * anyway (e.g. timer interrupt)
+ */
+static void __remove_hrtimer(struct hrtimer *timer,
+			     struct hrtimer_clock_base *base,
+			     u8 newstate, int reprogram)
+{
+	struct hrtimer_cpu_base *cpu_base = base->cpu_base;
+	u8 state = timer->state;
+
+	/* Pairs with the lockless read in hrtimer_is_queued() */
+	WRITE_ONCE(timer->state, newstate);
+	if (!(state & HRTIMER_STATE_ENQUEUED))
+		return;
+
+	if (!timerqueue_del(&base->active, &timer->node))
+		cpu_base->active_bases &= ~(1 << base->index);
+
+	/*
+	 * Note: If reprogram is false we do not update
+	 * cpu_base->next_timer. This happens when we remove the first
+	 * timer on a remote cpu. No harm as we never dereference
+	 * cpu_base->next_timer. So the worst thing what can happen is
+	 * an superfluous call to hrtimer_force_reprogram() on the
+	 * remote cpu later on if the same timer gets enqueued again.
+	 */
+	if (reprogram && timer == cpu_base->next_timer)
+		hrtimer_force_reprogram(cpu_base, 1);
+}
+
+/*
+ * remove hrtimer, called with base lock held
+ */
+static inline int
+remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
+	       bool restart, bool keep_local)
+{
+	u8 state = timer->state;
+
+	if (state & HRTIMER_STATE_ENQUEUED) {
+		bool reprogram;
+
+		/*
+		 * Remove the timer and force reprogramming when high
+		 * resolution mode is active and the timer is on the current
+		 * CPU. If we remove a timer on another CPU, reprogramming is
+		 * skipped. The interrupt event on this CPU is fired and
+		 * reprogramming happens in the interrupt handler. This is a
+		 * rare case and less expensive than a smp call.
+		 */
+		debug_deactivate(timer);
+		reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
+
+		/*
+		 * If the timer is not restarted then reprogramming is
+		 * required if the timer is local. If it is local and about
+		 * to be restarted, avoid programming it twice (on removal
+		 * and a moment later when it's requeued).
+		 */
+		if (!restart)
+			state = HRTIMER_STATE_INACTIVE;
+		else
+			reprogram &= !keep_local;
+
+		__remove_hrtimer(timer, base, state, reprogram);
+		return 1;
+	}
+	return 0;
+}
+
+static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
+					    const enum hrtimer_mode mode)
+{
+#ifdef CONFIG_TIME_LOW_RES
+	/*
+	 * CONFIG_TIME_LOW_RES indicates that the system has no way to return
+	 * granular time values. For relative timers we add hrtimer_resolution
+	 * (i.e. one jiffie) to prevent short timeouts.
+	 */
+	timer->is_rel = mode & HRTIMER_MODE_REL;
+	if (timer->is_rel)
+		tim = ktime_add_safe(tim, hrtimer_resolution);
+#endif
+	return tim;
+}
+
+static void
+hrtimer_update_softirq_timer(struct hrtimer_cpu_base *cpu_base, bool reprogram)
+{
+	ktime_t expires;
+
+	/*
+	 * Find the next SOFT expiration.
+	 */
+	expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
+
+	/*
+	 * reprogramming needs to be triggered, even if the next soft
+	 * hrtimer expires at the same time than the next hard
+	 * hrtimer. cpu_base->softirq_expires_next needs to be updated!
+	 */
+	if (expires == KTIME_MAX)
+		return;
+
+	/*
+	 * cpu_base->*next_timer is recomputed by __hrtimer_get_next_event()
+	 * cpu_base->*expires_next is only set by hrtimer_reprogram()
+	 */
+	hrtimer_reprogram(cpu_base->softirq_next_timer, reprogram);
+}
+
+static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
+				    u64 delta_ns, const enum hrtimer_mode mode,
+				    struct hrtimer_clock_base *base)
+{
+	struct hrtimer_clock_base *new_base;
+	bool force_local, first;
+
+	/*
+	 * If the timer is on the local cpu base and is the first expiring
+	 * timer then this might end up reprogramming the hardware twice
+	 * (on removal and on enqueue). To avoid that by prevent the
+	 * reprogram on removal, keep the timer local to the current CPU
+	 * and enforce reprogramming after it is queued no matter whether
+	 * it is the new first expiring timer again or not.
+	 */
+	force_local = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
+	force_local &= base->cpu_base->next_timer == timer;
+
+	/*
+	 * Remove an active timer from the queue. In case it is not queued
+	 * on the current CPU, make sure that remove_hrtimer() updates the
+	 * remote data correctly.
+	 *
+	 * If it's on the current CPU and the first expiring timer, then
+	 * skip reprogramming, keep the timer local and enforce
+	 * reprogramming later if it was the first expiring timer.  This
+	 * avoids programming the underlying clock event twice (once at
+	 * removal and once after enqueue).
+	 */
+	remove_hrtimer(timer, base, true, force_local);
+
+	if (mode & HRTIMER_MODE_REL)
+		tim = ktime_add_safe(tim, base->get_time());
+
+	tim = hrtimer_update_lowres(timer, tim, mode);
+
+	hrtimer_set_expires_range_ns(timer, tim, delta_ns);
+
+	/* Switch the timer base, if necessary: */
+	if (!force_local) {
+		new_base = switch_hrtimer_base(timer, base,
+					       mode & HRTIMER_MODE_PINNED);
+	} else {
+		new_base = base;
+	}
+
+	first = enqueue_hrtimer(timer, new_base, mode);
+	if (!force_local)
+		return first;
+
+	/*
+	 * Timer was forced to stay on the current CPU to avoid
+	 * reprogramming on removal and enqueue. Force reprogram the
+	 * hardware by evaluating the new first expiring timer.
+	 */
+	hrtimer_force_reprogram(new_base->cpu_base, 1);
+	return 0;
+}
+
+/**
+ * hrtimer_start_range_ns - (re)start an hrtimer
+ * @timer:	the timer to be added
+ * @tim:	expiry time
+ * @delta_ns:	"slack" range for the timer
+ * @mode:	timer mode: absolute (HRTIMER_MODE_ABS) or
+ *		relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
+ *		softirq based mode is considered for debug purpose only!
+ */
+void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
+			    u64 delta_ns, const enum hrtimer_mode mode)
+{
+	struct hrtimer_clock_base *base;
+	unsigned long flags;
+
+	/*
+	 * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
+	 * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
+	 * expiry mode because unmarked timers are moved to softirq expiry.
+	 */
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+		WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
+	else
+		WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
+
+	base = lock_hrtimer_base(timer, &flags);
+
+	if (__hrtimer_start_range_ns(timer, tim, delta_ns, mode, base))
+		hrtimer_reprogram(timer, true);
+
+	unlock_hrtimer_base(timer, &flags);
+}
+EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
+
+/**
+ * hrtimer_try_to_cancel - try to deactivate a timer
+ * @timer:	hrtimer to stop
+ *
+ * Returns:
+ *
+ *  *  0 when the timer was not active
+ *  *  1 when the timer was active
+ *  * -1 when the timer is currently executing the callback function and
+ *    cannot be stopped
+ */
+int hrtimer_try_to_cancel(struct hrtimer *timer)
+{
+	struct hrtimer_clock_base *base;
+	unsigned long flags;
+	int ret = -1;
+
+	/*
+	 * Check lockless first. If the timer is not active (neither
+	 * enqueued nor running the callback, nothing to do here.  The
+	 * base lock does not serialize against a concurrent enqueue,
+	 * so we can avoid taking it.
+	 */
+	if (!hrtimer_active(timer))
+		return 0;
+
+	base = lock_hrtimer_base(timer, &flags);
+
+	if (!hrtimer_callback_running(timer))
+		ret = remove_hrtimer(timer, base, false, false);
+
+	unlock_hrtimer_base(timer, &flags);
+
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
+
+#ifdef CONFIG_PREEMPT_RT
+static void hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base)
+{
+	spin_lock_init(&base->softirq_expiry_lock);
+}
+
+static void hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base)
+{
+	spin_lock(&base->softirq_expiry_lock);
+}
+
+static void hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base)
+{
+	spin_unlock(&base->softirq_expiry_lock);
+}
+
+/*
+ * The counterpart to hrtimer_cancel_wait_running().
+ *
+ * If there is a waiter for cpu_base->expiry_lock, then it was waiting for
+ * the timer callback to finish. Drop expiry_lock and reacquire it. That
+ * allows the waiter to acquire the lock and make progress.
+ */
+static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
+				      unsigned long flags)
+{
+	if (atomic_read(&cpu_base->timer_waiters)) {
+		raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+		spin_unlock(&cpu_base->softirq_expiry_lock);
+		spin_lock(&cpu_base->softirq_expiry_lock);
+		raw_spin_lock_irq(&cpu_base->lock);
+	}
+}
+
+/*
+ * This function is called on PREEMPT_RT kernels when the fast path
+ * deletion of a timer failed because the timer callback function was
+ * running.
+ *
+ * This prevents priority inversion: if the soft irq thread is preempted
+ * in the middle of a timer callback, then calling del_timer_sync() can
+ * lead to two issues:
+ *
+ *  - If the caller is on a remote CPU then it has to spin wait for the timer
+ *    handler to complete. This can result in unbound priority inversion.
+ *
+ *  - If the caller originates from the task which preempted the timer
+ *    handler on the same CPU, then spin waiting for the timer handler to
+ *    complete is never going to end.
+ */
+void hrtimer_cancel_wait_running(const struct hrtimer *timer)
+{
+	/* Lockless read. Prevent the compiler from reloading it below */
+	struct hrtimer_clock_base *base = READ_ONCE(timer->base);
+
+	/*
+	 * Just relax if the timer expires in hard interrupt context or if
+	 * it is currently on the migration base.
+	 */
+	if (!timer->is_soft || is_migration_base(base)) {
+		cpu_relax();
+		return;
+	}
+
+	/*
+	 * Mark the base as contended and grab the expiry lock, which is
+	 * held by the softirq across the timer callback. Drop the lock
+	 * immediately so the softirq can expire the next timer. In theory
+	 * the timer could already be running again, but that's more than
+	 * unlikely and just causes another wait loop.
+	 */
+	atomic_inc(&base->cpu_base->timer_waiters);
+	spin_lock_bh(&base->cpu_base->softirq_expiry_lock);
+	atomic_dec(&base->cpu_base->timer_waiters);
+	spin_unlock_bh(&base->cpu_base->softirq_expiry_lock);
+}
+#else
+static inline void
+hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base) { }
+static inline void
+hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base) { }
+static inline void
+hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base) { }
+static inline void hrtimer_sync_wait_running(struct hrtimer_cpu_base *base,
+					     unsigned long flags) { }
+#endif
+
+/**
+ * hrtimer_cancel - cancel a timer and wait for the handler to finish.
+ * @timer:	the timer to be cancelled
+ *
+ * Returns:
+ *  0 when the timer was not active
+ *  1 when the timer was active
+ */
+int hrtimer_cancel(struct hrtimer *timer)
+{
+	int ret;
+
+	do {
+		ret = hrtimer_try_to_cancel(timer);
+
+		if (ret < 0)
+			hrtimer_cancel_wait_running(timer);
+	} while (ret < 0);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(hrtimer_cancel);
+
+/**
+ * __hrtimer_get_remaining - get remaining time for the timer
+ * @timer:	the timer to read
+ * @adjust:	adjust relative timers when CONFIG_TIME_LOW_RES=y
+ */
+ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust)
+{
+	unsigned long flags;
+	ktime_t rem;
+
+	lock_hrtimer_base(timer, &flags);
+	if (IS_ENABLED(CONFIG_TIME_LOW_RES) && adjust)
+		rem = hrtimer_expires_remaining_adjusted(timer);
+	else
+		rem = hrtimer_expires_remaining(timer);
+	unlock_hrtimer_base(timer, &flags);
+
+	return rem;
+}
+EXPORT_SYMBOL_GPL(__hrtimer_get_remaining);
+
+#ifdef CONFIG_NO_HZ_COMMON
+/**
+ * hrtimer_get_next_event - get the time until next expiry event
+ *
+ * Returns the next expiry time or KTIME_MAX if no timer is pending.
+ */
+u64 hrtimer_get_next_event(void)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	u64 expires = KTIME_MAX;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+
+	if (!__hrtimer_hres_active(cpu_base))
+		expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
+
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+
+	return expires;
+}
+
+/**
+ * hrtimer_next_event_without - time until next expiry event w/o one timer
+ * @exclude:	timer to exclude
+ *
+ * Returns the next expiry time over all timers except for the @exclude one or
+ * KTIME_MAX if none of them is pending.
+ */
+u64 hrtimer_next_event_without(const struct hrtimer *exclude)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	u64 expires = KTIME_MAX;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+
+	if (__hrtimer_hres_active(cpu_base)) {
+		unsigned int active;
+
+		if (!cpu_base->softirq_activated) {
+			active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
+			expires = __hrtimer_next_event_base(cpu_base, exclude,
+							    active, KTIME_MAX);
+		}
+		active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
+		expires = __hrtimer_next_event_base(cpu_base, exclude, active,
+						    expires);
+	}
+
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+
+	return expires;
+}
+#endif
+
+static inline int hrtimer_clockid_to_base(clockid_t clock_id)
+{
+	if (likely(clock_id < MAX_CLOCKS)) {
+		int base = hrtimer_clock_to_base_table[clock_id];
+
+		if (likely(base != HRTIMER_MAX_CLOCK_BASES))
+			return base;
+	}
+	WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
+	return HRTIMER_BASE_MONOTONIC;
+}
+
+static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
+			   enum hrtimer_mode mode)
+{
+	bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
+	struct hrtimer_cpu_base *cpu_base;
+	int base;
+
+	/*
+	 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
+	 * marked for hard interrupt expiry mode are moved into soft
+	 * interrupt context for latency reasons and because the callbacks
+	 * can invoke functions which might sleep on RT, e.g. spin_lock().
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
+		softtimer = true;
+
+	memset(timer, 0, sizeof(struct hrtimer));
+
+	cpu_base = raw_cpu_ptr(&hrtimer_bases);
+
+	/*
+	 * POSIX magic: Relative CLOCK_REALTIME timers are not affected by
+	 * clock modifications, so they needs to become CLOCK_MONOTONIC to
+	 * ensure POSIX compliance.
+	 */
+	if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
+		clock_id = CLOCK_MONOTONIC;
+
+	base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
+	base += hrtimer_clockid_to_base(clock_id);
+	timer->is_soft = softtimer;
+	timer->is_hard = !!(mode & HRTIMER_MODE_HARD);
+	timer->base = &cpu_base->clock_base[base];
+	timerqueue_init(&timer->node);
+}
+
+/**
+ * hrtimer_init - initialize a timer to the given clock
+ * @timer:	the timer to be initialized
+ * @clock_id:	the clock to be used
+ * @mode:       The modes which are relevant for initialization:
+ *              HRTIMER_MODE_ABS, HRTIMER_MODE_REL, HRTIMER_MODE_ABS_SOFT,
+ *              HRTIMER_MODE_REL_SOFT
+ *
+ *              The PINNED variants of the above can be handed in,
+ *              but the PINNED bit is ignored as pinning happens
+ *              when the hrtimer is started
+ */
+void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
+		  enum hrtimer_mode mode)
+{
+	debug_init(timer, clock_id, mode);
+	__hrtimer_init(timer, clock_id, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_init);
+
+/*
+ * A timer is active, when it is enqueued into the rbtree or the
+ * callback function is running or it's in the state of being migrated
+ * to another cpu.
+ *
+ * It is important for this function to not return a false negative.
+ */
+bool hrtimer_active(const struct hrtimer *timer)
+{
+	struct hrtimer_clock_base *base;
+	unsigned int seq;
+
+	do {
+		base = READ_ONCE(timer->base);
+		seq = raw_read_seqcount_begin(&base->seq);
+
+		if (timer->state != HRTIMER_STATE_INACTIVE ||
+		    base->running == timer)
+			return true;
+
+	} while (read_seqcount_retry(&base->seq, seq) ||
+		 base != READ_ONCE(timer->base));
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(hrtimer_active);
+
+/*
+ * The write_seqcount_barrier()s in __run_hrtimer() split the thing into 3
+ * distinct sections:
+ *
+ *  - queued:	the timer is queued
+ *  - callback:	the timer is being ran
+ *  - post:	the timer is inactive or (re)queued
+ *
+ * On the read side we ensure we observe timer->state and cpu_base->running
+ * from the same section, if anything changed while we looked at it, we retry.
+ * This includes timer->base changing because sequence numbers alone are
+ * insufficient for that.
+ *
+ * The sequence numbers are required because otherwise we could still observe
+ * a false negative if the read side got smeared over multiple consecutive
+ * __run_hrtimer() invocations.
+ */
+
+static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
+			  struct hrtimer_clock_base *base,
+			  struct hrtimer *timer, ktime_t *now,
+			  unsigned long flags) __must_hold(&cpu_base->lock)
+{
+	enum hrtimer_restart (*fn)(struct hrtimer *);
+	bool expires_in_hardirq;
+	int restart;
+
+	lockdep_assert_held(&cpu_base->lock);
+
+	debug_deactivate(timer);
+	base->running = timer;
+
+	/*
+	 * Separate the ->running assignment from the ->state assignment.
+	 *
+	 * As with a regular write barrier, this ensures the read side in
+	 * hrtimer_active() cannot observe base->running == NULL &&
+	 * timer->state == INACTIVE.
+	 */
+	raw_write_seqcount_barrier(&base->seq);
+
+	__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
+	fn = timer->function;
+
+	/*
+	 * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
+	 * timer is restarted with a period then it becomes an absolute
+	 * timer. If its not restarted it does not matter.
+	 */
+	if (IS_ENABLED(CONFIG_TIME_LOW_RES))
+		timer->is_rel = false;
+
+	/*
+	 * The timer is marked as running in the CPU base, so it is
+	 * protected against migration to a different CPU even if the lock
+	 * is dropped.
+	 */
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+	trace_hrtimer_expire_entry(timer, now);
+	expires_in_hardirq = lockdep_hrtimer_enter(timer);
+
+	restart = fn(timer);
+
+	lockdep_hrtimer_exit(expires_in_hardirq);
+	trace_hrtimer_expire_exit(timer);
+	raw_spin_lock_irq(&cpu_base->lock);
+
+	/*
+	 * Note: We clear the running state after enqueue_hrtimer and
+	 * we do not reprogram the event hardware. Happens either in
+	 * hrtimer_start_range_ns() or in hrtimer_interrupt()
+	 *
+	 * Note: Because we dropped the cpu_base->lock above,
+	 * hrtimer_start_range_ns() can have popped in and enqueued the timer
+	 * for us already.
+	 */
+	if (restart != HRTIMER_NORESTART &&
+	    !(timer->state & HRTIMER_STATE_ENQUEUED))
+		enqueue_hrtimer(timer, base, HRTIMER_MODE_ABS);
+
+	/*
+	 * Separate the ->running assignment from the ->state assignment.
+	 *
+	 * As with a regular write barrier, this ensures the read side in
+	 * hrtimer_active() cannot observe base->running.timer == NULL &&
+	 * timer->state == INACTIVE.
+	 */
+	raw_write_seqcount_barrier(&base->seq);
+
+	WARN_ON_ONCE(base->running != timer);
+	base->running = NULL;
+}
+
+static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
+				 unsigned long flags, unsigned int active_mask)
+{
+	struct hrtimer_clock_base *base;
+	unsigned int active = cpu_base->active_bases & active_mask;
+
+	for_each_active_base(base, cpu_base, active) {
+		struct timerqueue_node *node;
+		ktime_t basenow;
+
+		basenow = ktime_add(now, base->offset);
+
+		while ((node = timerqueue_getnext(&base->active))) {
+			struct hrtimer *timer;
+
+			timer = container_of(node, struct hrtimer, node);
+
+			/*
+			 * The immediate goal for using the softexpires is
+			 * minimizing wakeups, not running timers at the
+			 * earliest interrupt after their soft expiration.
+			 * This allows us to avoid using a Priority Search
+			 * Tree, which can answer a stabbing query for
+			 * overlapping intervals and instead use the simple
+			 * BST we already have.
+			 * We don't add extra wakeups by delaying timers that
+			 * are right-of a not yet expired timer, because that
+			 * timer will have to trigger a wakeup anyway.
+			 */
+			if (basenow < hrtimer_get_softexpires_tv64(timer))
+				break;
+
+			__run_hrtimer(cpu_base, base, timer, &basenow, flags);
+			if (active_mask == HRTIMER_ACTIVE_SOFT)
+				hrtimer_sync_wait_running(cpu_base, flags);
+		}
+	}
+}
+
+static __latent_entropy void hrtimer_run_softirq(struct softirq_action *h)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	unsigned long flags;
+	ktime_t now;
+
+	hrtimer_cpu_base_lock_expiry(cpu_base);
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+
+	now = hrtimer_update_base(cpu_base);
+	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_SOFT);
+
+	cpu_base->softirq_activated = 0;
+	hrtimer_update_softirq_timer(cpu_base, true);
+
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+	hrtimer_cpu_base_unlock_expiry(cpu_base);
+}
+
+#ifdef CONFIG_HIGH_RES_TIMERS
+
+/*
+ * High resolution timer interrupt
+ * Called with interrupts disabled
+ */
+void hrtimer_interrupt(struct clock_event_device *dev)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	ktime_t expires_next, now, entry_time, delta;
+	unsigned long flags;
+	int retries = 0;
+
+	BUG_ON(!cpu_base->hres_active);
+	cpu_base->nr_events++;
+	dev->next_event = KTIME_MAX;
+
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+	entry_time = now = hrtimer_update_base(cpu_base);
+retry:
+	cpu_base->in_hrtirq = 1;
+	/*
+	 * We set expires_next to KTIME_MAX here with cpu_base->lock
+	 * held to prevent that a timer is enqueued in our queue via
+	 * the migration code. This does not affect enqueueing of
+	 * timers which run their callback and need to be requeued on
+	 * this CPU.
+	 */
+	cpu_base->expires_next = KTIME_MAX;
+
+	if (!ktime_before(now, cpu_base->softirq_expires_next)) {
+		cpu_base->softirq_expires_next = KTIME_MAX;
+		cpu_base->softirq_activated = 1;
+		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+	}
+
+	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
+
+	/* Reevaluate the clock bases for the [soft] next expiry */
+	expires_next = hrtimer_update_next_event(cpu_base);
+	/*
+	 * Store the new expiry value so the migration code can verify
+	 * against it.
+	 */
+	cpu_base->expires_next = expires_next;
+	cpu_base->in_hrtirq = 0;
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+
+	/* Reprogramming necessary ? */
+	if (!tick_program_event(expires_next, 0)) {
+		cpu_base->hang_detected = 0;
+		return;
+	}
+
+	/*
+	 * The next timer was already expired due to:
+	 * - tracing
+	 * - long lasting callbacks
+	 * - being scheduled away when running in a VM
+	 *
+	 * We need to prevent that we loop forever in the hrtimer
+	 * interrupt routine. We give it 3 attempts to avoid
+	 * overreacting on some spurious event.
+	 *
+	 * Acquire base lock for updating the offsets and retrieving
+	 * the current time.
+	 */
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+	now = hrtimer_update_base(cpu_base);
+	cpu_base->nr_retries++;
+	if (++retries < 3)
+		goto retry;
+	/*
+	 * Give the system a chance to do something else than looping
+	 * here. We stored the entry time, so we know exactly how long
+	 * we spent here. We schedule the next event this amount of
+	 * time away.
+	 */
+	cpu_base->nr_hangs++;
+	cpu_base->hang_detected = 1;
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+
+	delta = ktime_sub(now, entry_time);
+	if ((unsigned int)delta > cpu_base->max_hang_time)
+		cpu_base->max_hang_time = (unsigned int) delta;
+	/*
+	 * Limit it to a sensible value as we enforce a longer
+	 * delay. Give the CPU at least 100ms to catch up.
+	 */
+	if (delta > 100 * NSEC_PER_MSEC)
+		expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
+	else
+		expires_next = ktime_add(now, delta);
+	tick_program_event(expires_next, 1);
+	pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
+}
+
+/* called with interrupts disabled */
+static inline void __hrtimer_peek_ahead_timers(void)
+{
+	struct tick_device *td;
+
+	if (!hrtimer_hres_active())
+		return;
+
+	td = this_cpu_ptr(&tick_cpu_device);
+	if (td && td->evtdev)
+		hrtimer_interrupt(td->evtdev);
+}
+
+#else /* CONFIG_HIGH_RES_TIMERS */
+
+static inline void __hrtimer_peek_ahead_timers(void) { }
+
+#endif	/* !CONFIG_HIGH_RES_TIMERS */
+
+/*
+ * Called from run_local_timers in hardirq context every jiffy
+ */
+void hrtimer_run_queues(void)
+{
+	struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
+	unsigned long flags;
+	ktime_t now;
+
+	if (__hrtimer_hres_active(cpu_base))
+		return;
+
+	/*
+	 * This _is_ ugly: We have to check periodically, whether we
+	 * can switch to highres and / or nohz mode. The clocksource
+	 * switch happens with xtime_lock held. Notification from
+	 * there only sets the check bit in the tick_oneshot code,
+	 * otherwise we might deadlock vs. xtime_lock.
+	 */
+	if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) {
+		hrtimer_switch_to_hres();
+		return;
+	}
+
+	raw_spin_lock_irqsave(&cpu_base->lock, flags);
+	now = hrtimer_update_base(cpu_base);
+
+	if (!ktime_before(now, cpu_base->softirq_expires_next)) {
+		cpu_base->softirq_expires_next = KTIME_MAX;
+		cpu_base->softirq_activated = 1;
+		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+	}
+
+	__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
+	raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+}
+
+/*
+ * Sleep related functions:
+ */
+static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
+{
+	struct hrtimer_sleeper *t =
+		container_of(timer, struct hrtimer_sleeper, timer);
+	struct task_struct *task = t->task;
+
+	t->task = NULL;
+	if (task)
+		wake_up_process(task);
+
+	return HRTIMER_NORESTART;
+}
+
+/**
+ * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
+ * @sl:		sleeper to be started
+ * @mode:	timer mode abs/rel
+ *
+ * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
+ * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
+ */
+void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
+				   enum hrtimer_mode mode)
+{
+	/*
+	 * Make the enqueue delivery mode check work on RT. If the sleeper
+	 * was initialized for hard interrupt delivery, force the mode bit.
+	 * This is a special case for hrtimer_sleepers because
+	 * hrtimer_init_sleeper() determines the delivery mode on RT so the
+	 * fiddling with this decision is avoided at the call sites.
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard)
+		mode |= HRTIMER_MODE_HARD;
+
+	hrtimer_start_expires(&sl->timer, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
+
+static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
+				   clockid_t clock_id, enum hrtimer_mode mode)
+{
+	/*
+	 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
+	 * marked for hard interrupt expiry mode are moved into soft
+	 * interrupt context either for latency reasons or because the
+	 * hrtimer callback takes regular spinlocks or invokes other
+	 * functions which are not suitable for hard interrupt context on
+	 * PREEMPT_RT.
+	 *
+	 * The hrtimer_sleeper callback is RT compatible in hard interrupt
+	 * context, but there is a latency concern: Untrusted userspace can
+	 * spawn many threads which arm timers for the same expiry time on
+	 * the same CPU. That causes a latency spike due to the wakeup of
+	 * a gazillion threads.
+	 *
+	 * OTOH, privileged real-time user space applications rely on the
+	 * low latency of hard interrupt wakeups. If the current task is in
+	 * a real-time scheduling class, mark the mode for hard interrupt
+	 * expiry.
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+		if (task_is_realtime(current) && !(mode & HRTIMER_MODE_SOFT))
+			mode |= HRTIMER_MODE_HARD;
+	}
+
+	__hrtimer_init(&sl->timer, clock_id, mode);
+	sl->timer.function = hrtimer_wakeup;
+	sl->task = current;
+}
+
+/**
+ * hrtimer_init_sleeper - initialize sleeper to the given clock
+ * @sl:		sleeper to be initialized
+ * @clock_id:	the clock to be used
+ * @mode:	timer mode abs/rel
+ */
+void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, clockid_t clock_id,
+			  enum hrtimer_mode mode)
+{
+	debug_init(&sl->timer, clock_id, mode);
+	__hrtimer_init_sleeper(sl, clock_id, mode);
+
+}
+EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
+
+int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
+{
+	switch(restart->nanosleep.type) {
+#ifdef CONFIG_COMPAT_32BIT_TIME
+	case TT_COMPAT:
+		if (put_old_timespec32(ts, restart->nanosleep.compat_rmtp))
+			return -EFAULT;
+		break;
+#endif
+	case TT_NATIVE:
+		if (put_timespec64(ts, restart->nanosleep.rmtp))
+			return -EFAULT;
+		break;
+	default:
+		BUG();
+	}
+	return -ERESTART_RESTARTBLOCK;
+}
+
+static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
+{
+	struct restart_block *restart;
+
+	do {
+		set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
+		hrtimer_sleeper_start_expires(t, mode);
+
+		if (likely(t->task))
+			schedule();
+
+		hrtimer_cancel(&t->timer);
+		mode = HRTIMER_MODE_ABS;
+
+	} while (t->task && !signal_pending(current));
+
+	__set_current_state(TASK_RUNNING);
+
+	if (!t->task)
+		return 0;
+
+	restart = &current->restart_block;
+	if (restart->nanosleep.type != TT_NONE) {
+		ktime_t rem = hrtimer_expires_remaining(&t->timer);
+		struct timespec64 rmt;
+
+		if (rem <= 0)
+			return 0;
+		rmt = ktime_to_timespec64(rem);
+
+		return nanosleep_copyout(restart, &rmt);
+	}
+	return -ERESTART_RESTARTBLOCK;
+}
+
+static long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
+{
+	struct hrtimer_sleeper t;
+	int ret;
+
+	hrtimer_init_sleeper_on_stack(&t, restart->nanosleep.clockid,
+				      HRTIMER_MODE_ABS);
+	hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
+	ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
+	destroy_hrtimer_on_stack(&t.timer);
+	return ret;
+}
+
+long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode,
+		       const clockid_t clockid)
+{
+	struct restart_block *restart;
+	struct hrtimer_sleeper t;
+	int ret = 0;
+	u64 slack;
+
+	slack = current->timer_slack_ns;
+	if (rt_task(current))
+		slack = 0;
+
+	hrtimer_init_sleeper_on_stack(&t, clockid, mode);
+	hrtimer_set_expires_range_ns(&t.timer, rqtp, slack);
+	ret = do_nanosleep(&t, mode);
+	if (ret != -ERESTART_RESTARTBLOCK)
+		goto out;
+
+	/* Absolute timers do not update the rmtp value and restart: */
+	if (mode == HRTIMER_MODE_ABS) {
+		ret = -ERESTARTNOHAND;
+		goto out;
+	}
+
+	restart = &current->restart_block;
+	restart->nanosleep.clockid = t.timer.base->clockid;
+	restart->nanosleep.expires = hrtimer_get_expires_tv64(&t.timer);
+	set_restart_fn(restart, hrtimer_nanosleep_restart);
+out:
+	destroy_hrtimer_on_stack(&t.timer);
+	return ret;
+}
+
+#ifdef CONFIG_64BIT
+
+SYSCALL_DEFINE2(nanosleep, struct __kernel_timespec __user *, rqtp,
+		struct __kernel_timespec __user *, rmtp)
+{
+	struct timespec64 tu;
+
+	if (get_timespec64(&tu, rqtp))
+		return -EFAULT;
+
+	if (!timespec64_valid(&tu))
+		return -EINVAL;
+
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
+	current->restart_block.nanosleep.rmtp = rmtp;
+	return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
+				 CLOCK_MONOTONIC);
+}
+
+#endif
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+
+SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp,
+		       struct old_timespec32 __user *, rmtp)
+{
+	struct timespec64 tu;
+
+	if (get_old_timespec32(&tu, rqtp))
+		return -EFAULT;
+
+	if (!timespec64_valid(&tu))
+		return -EINVAL;
+
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
+	current->restart_block.nanosleep.compat_rmtp = rmtp;
+	return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
+				 CLOCK_MONOTONIC);
+}
+#endif
+
+/*
+ * Functions related to boot-time initialization:
+ */
+int hrtimers_prepare_cpu(unsigned int cpu)
+{
+	struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
+	int i;
+
+	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
+		struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];
+
+		clock_b->cpu_base = cpu_base;
+		seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
+		timerqueue_init_head(&clock_b->active);
+	}
+
+	cpu_base->cpu = cpu;
+	cpu_base->active_bases = 0;
+	cpu_base->hres_active = 0;
+	cpu_base->hang_detected = 0;
+	cpu_base->next_timer = NULL;
+	cpu_base->softirq_next_timer = NULL;
+	cpu_base->expires_next = KTIME_MAX;
+	cpu_base->softirq_expires_next = KTIME_MAX;
+	hrtimer_cpu_base_init_expiry_lock(cpu_base);
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
+				struct hrtimer_clock_base *new_base)
+{
+	struct hrtimer *timer;
+	struct timerqueue_node *node;
+
+	while ((node = timerqueue_getnext(&old_base->active))) {
+		timer = container_of(node, struct hrtimer, node);
+		BUG_ON(hrtimer_callback_running(timer));
+		debug_deactivate(timer);
+
+		/*
+		 * Mark it as ENQUEUED not INACTIVE otherwise the
+		 * timer could be seen as !active and just vanish away
+		 * under us on another CPU
+		 */
+		__remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0);
+		timer->base = new_base;
+		/*
+		 * Enqueue the timers on the new cpu. This does not
+		 * reprogram the event device in case the timer
+		 * expires before the earliest on this CPU, but we run
+		 * hrtimer_interrupt after we migrated everything to
+		 * sort out already expired timers and reprogram the
+		 * event device.
+		 */
+		enqueue_hrtimer(timer, new_base, HRTIMER_MODE_ABS);
+	}
+}
+
+int hrtimers_cpu_dying(unsigned int dying_cpu)
+{
+	struct hrtimer_cpu_base *old_base, *new_base;
+	int i, ncpu = cpumask_first(cpu_active_mask);
+
+	tick_cancel_sched_timer(dying_cpu);
+
+	old_base = this_cpu_ptr(&hrtimer_bases);
+	new_base = &per_cpu(hrtimer_bases, ncpu);
+
+	/*
+	 * The caller is globally serialized and nobody else
+	 * takes two locks at once, deadlock is not possible.
+	 */
+	raw_spin_lock(&old_base->lock);
+	raw_spin_lock_nested(&new_base->lock, SINGLE_DEPTH_NESTING);
+
+	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
+		migrate_hrtimer_list(&old_base->clock_base[i],
+				     &new_base->clock_base[i]);
+	}
+
+	/*
+	 * The migration might have changed the first expiring softirq
+	 * timer on this CPU. Update it.
+	 */
+	__hrtimer_get_next_event(new_base, HRTIMER_ACTIVE_SOFT);
+	/* Tell the other CPU to retrigger the next event */
+	smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);
+
+	raw_spin_unlock(&new_base->lock);
+	raw_spin_unlock(&old_base->lock);
+
+	return 0;
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
+void __init hrtimers_init(void)
+{
+	hrtimers_prepare_cpu(smp_processor_id());
+	open_softirq(HRTIMER_SOFTIRQ, hrtimer_run_softirq);
+}
+
+/**
+ * schedule_hrtimeout_range_clock - sleep until timeout
+ * @expires:	timeout value (ktime_t)
+ * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
+ * @mode:	timer mode
+ * @clock_id:	timer clock to be used
+ */
+int __sched
+schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
+			       const enum hrtimer_mode mode, clockid_t clock_id)
+{
+	struct hrtimer_sleeper t;
+
+	/*
+	 * Optimize when a zero timeout value is given. It does not
+	 * matter whether this is an absolute or a relative time.
+	 */
+	if (expires && *expires == 0) {
+		__set_current_state(TASK_RUNNING);
+		return 0;
+	}
+
+	/*
+	 * A NULL parameter means "infinite"
+	 */
+	if (!expires) {
+		schedule();
+		return -EINTR;
+	}
+
+	/*
+	 * Override any slack passed by the user if under
+	 * rt contraints.
+	 */
+	if (rt_task(current))
+		delta = 0;
+
+	hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
+	hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
+	hrtimer_sleeper_start_expires(&t, mode);
+
+	if (likely(t.task))
+		schedule();
+
+	hrtimer_cancel(&t.timer);
+	destroy_hrtimer_on_stack(&t.timer);
+
+	__set_current_state(TASK_RUNNING);
+
+	return !t.task ? 0 : -EINTR;
+}
+EXPORT_SYMBOL_GPL(schedule_hrtimeout_range_clock);
+
+/**
+ * schedule_hrtimeout_range - sleep until timeout
+ * @expires:	timeout value (ktime_t)
+ * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
+ * @mode:	timer mode
+ *
+ * Make the current task sleep until the given expiry time has
+ * elapsed. The routine will return immediately unless
+ * the current task state has been set (see set_current_state()).
+ *
+ * The @delta argument gives the kernel the freedom to schedule the
+ * actual wakeup to a time that is both power and performance friendly
+ * for regular (non RT/DL) tasks.
+ * The kernel give the normal best effort behavior for "@expires+@delta",
+ * but may decide to fire the timer earlier, but no earlier than @expires.
+ *
+ * You can set the task state as follows -
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process()).
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task or the current task is explicitly woken
+ * up.
+ *
+ * The current task state is guaranteed to be TASK_RUNNING when this
+ * routine returns.
+ *
+ * Returns 0 when the timer has expired. If the task was woken before the
+ * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
+ * by an explicit wakeup, it returns -EINTR.
+ */
+int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
+				     const enum hrtimer_mode mode)
+{
+	return schedule_hrtimeout_range_clock(expires, delta, mode,
+					      CLOCK_MONOTONIC);
+}
+EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
+
+/**
+ * schedule_hrtimeout - sleep until timeout
+ * @expires:	timeout value (ktime_t)
+ * @mode:	timer mode
+ *
+ * Make the current task sleep until the given expiry time has
+ * elapsed. The routine will return immediately unless
+ * the current task state has been set (see set_current_state()).
+ *
+ * You can set the task state as follows -
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process()).
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task or the current task is explicitly woken
+ * up.
+ *
+ * The current task state is guaranteed to be TASK_RUNNING when this
+ * routine returns.
+ *
+ * Returns 0 when the timer has expired. If the task was woken before the
+ * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
+ * by an explicit wakeup, it returns -EINTR.
+ */
+int __sched schedule_hrtimeout(ktime_t *expires,
+			       const enum hrtimer_mode mode)
+{
+	return schedule_hrtimeout_range(expires, 0, mode);
+}
+EXPORT_SYMBOL_GPL(schedule_hrtimeout);
diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c
new file mode 100644
index 0000000000..00629e658c
--- /dev/null
+++ b/kernel/time/itimer.c
@@ -0,0 +1,403 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1992 Darren Senn
+ */
+
+/* These are all the functions necessary to implement itimers */
+
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/syscalls.h>
+#include <linux/time.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/cputime.h>
+#include <linux/posix-timers.h>
+#include <linux/hrtimer.h>
+#include <trace/events/timer.h>
+#include <linux/compat.h>
+
+#include <linux/uaccess.h>
+
+/**
+ * itimer_get_remtime - get remaining time for the timer
+ *
+ * @timer: the timer to read
+ *
+ * Returns the delta between the expiry time and now, which can be
+ * less than zero or 1usec for an pending expired timer
+ */
+static struct timespec64 itimer_get_remtime(struct hrtimer *timer)
+{
+	ktime_t rem = __hrtimer_get_remaining(timer, true);
+
+	/*
+	 * Racy but safe: if the itimer expires after the above
+	 * hrtimer_get_remtime() call but before this condition
+	 * then we return 0 - which is correct.
+	 */
+	if (hrtimer_active(timer)) {
+		if (rem <= 0)
+			rem = NSEC_PER_USEC;
+	} else
+		rem = 0;
+
+	return ktime_to_timespec64(rem);
+}
+
+static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   struct itimerspec64 *const value)
+{
+	u64 val, interval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	val = it->expires;
+	interval = it->incr;
+	if (val) {
+		u64 t, samples[CPUCLOCK_MAX];
+
+		thread_group_sample_cputime(tsk, samples);
+		t = samples[clock_id];
+
+		if (val < t)
+			/* about to fire */
+			val = TICK_NSEC;
+		else
+			val -= t;
+	}
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	value->it_value = ns_to_timespec64(val);
+	value->it_interval = ns_to_timespec64(interval);
+}
+
+static int do_getitimer(int which, struct itimerspec64 *value)
+{
+	struct task_struct *tsk = current;
+
+	switch (which) {
+	case ITIMER_REAL:
+		spin_lock_irq(&tsk->sighand->siglock);
+		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
+		value->it_interval =
+			ktime_to_timespec64(tsk->signal->it_real_incr);
+		spin_unlock_irq(&tsk->sighand->siglock);
+		break;
+	case ITIMER_VIRTUAL:
+		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
+		break;
+	case ITIMER_PROF:
+		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
+		break;
+	default:
+		return(-EINVAL);
+	}
+	return 0;
+}
+
+static int put_itimerval(struct __kernel_old_itimerval __user *o,
+			 const struct itimerspec64 *i)
+{
+	struct __kernel_old_itimerval v;
+
+	v.it_interval.tv_sec = i->it_interval.tv_sec;
+	v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
+	v.it_value.tv_sec = i->it_value.tv_sec;
+	v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
+	return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0;
+}
+
+
+SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value)
+{
+	struct itimerspec64 get_buffer;
+	int error = do_getitimer(which, &get_buffer);
+
+	if (!error && put_itimerval(value, &get_buffer))
+		error = -EFAULT;
+	return error;
+}
+
+#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
+struct old_itimerval32 {
+	struct old_timeval32	it_interval;
+	struct old_timeval32	it_value;
+};
+
+static int put_old_itimerval32(struct old_itimerval32 __user *o,
+			       const struct itimerspec64 *i)
+{
+	struct old_itimerval32 v32;
+
+	v32.it_interval.tv_sec = i->it_interval.tv_sec;
+	v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
+	v32.it_value.tv_sec = i->it_value.tv_sec;
+	v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
+	return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0;
+}
+
+COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
+		       struct old_itimerval32 __user *, value)
+{
+	struct itimerspec64 get_buffer;
+	int error = do_getitimer(which, &get_buffer);
+
+	if (!error && put_old_itimerval32(value, &get_buffer))
+		error = -EFAULT;
+	return error;
+}
+#endif
+
+/*
+ * The timer is automagically restarted, when interval != 0
+ */
+enum hrtimer_restart it_real_fn(struct hrtimer *timer)
+{
+	struct signal_struct *sig =
+		container_of(timer, struct signal_struct, real_timer);
+	struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
+
+	trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
+	kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
+
+	return HRTIMER_NORESTART;
+}
+
+static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+			   const struct itimerspec64 *const value,
+			   struct itimerspec64 *const ovalue)
+{
+	u64 oval, nval, ointerval, ninterval;
+	struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+	nval = timespec64_to_ns(&value->it_value);
+	ninterval = timespec64_to_ns(&value->it_interval);
+
+	spin_lock_irq(&tsk->sighand->siglock);
+
+	oval = it->expires;
+	ointerval = it->incr;
+	if (oval || nval) {
+		if (nval > 0)
+			nval += TICK_NSEC;
+		set_process_cpu_timer(tsk, clock_id, &nval, &oval);
+	}
+	it->expires = nval;
+	it->incr = ninterval;
+	trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
+			   ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
+
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	if (ovalue) {
+		ovalue->it_value = ns_to_timespec64(oval);
+		ovalue->it_interval = ns_to_timespec64(ointerval);
+	}
+}
+
+/*
+ * Returns true if the timeval is in canonical form
+ */
+#define timeval_valid(t) \
+	(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
+
+static int do_setitimer(int which, struct itimerspec64 *value,
+			struct itimerspec64 *ovalue)
+{
+	struct task_struct *tsk = current;
+	struct hrtimer *timer;
+	ktime_t expires;
+
+	switch (which) {
+	case ITIMER_REAL:
+again:
+		spin_lock_irq(&tsk->sighand->siglock);
+		timer = &tsk->signal->real_timer;
+		if (ovalue) {
+			ovalue->it_value = itimer_get_remtime(timer);
+			ovalue->it_interval
+				= ktime_to_timespec64(tsk->signal->it_real_incr);
+		}
+		/* We are sharing ->siglock with it_real_fn() */
+		if (hrtimer_try_to_cancel(timer) < 0) {
+			spin_unlock_irq(&tsk->sighand->siglock);
+			hrtimer_cancel_wait_running(timer);
+			goto again;
+		}
+		expires = timespec64_to_ktime(value->it_value);
+		if (expires != 0) {
+			tsk->signal->it_real_incr =
+				timespec64_to_ktime(value->it_interval);
+			hrtimer_start(timer, expires, HRTIMER_MODE_REL);
+		} else
+			tsk->signal->it_real_incr = 0;
+
+		trace_itimer_state(ITIMER_REAL, value, 0);
+		spin_unlock_irq(&tsk->sighand->siglock);
+		break;
+	case ITIMER_VIRTUAL:
+		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
+		break;
+	case ITIMER_PROF:
+		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+#ifdef CONFIG_SECURITY_SELINUX
+void clear_itimer(void)
+{
+	struct itimerspec64 v = {};
+	int i;
+
+	for (i = 0; i < 3; i++)
+		do_setitimer(i, &v, NULL);
+}
+#endif
+
+#ifdef __ARCH_WANT_SYS_ALARM
+
+/**
+ * alarm_setitimer - set alarm in seconds
+ *
+ * @seconds:	number of seconds until alarm
+ *		0 disables the alarm
+ *
+ * Returns the remaining time in seconds of a pending timer or 0 when
+ * the timer is not active.
+ *
+ * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
+ * negative timeval settings which would cause immediate expiry.
+ */
+static unsigned int alarm_setitimer(unsigned int seconds)
+{
+	struct itimerspec64 it_new, it_old;
+
+#if BITS_PER_LONG < 64
+	if (seconds > INT_MAX)
+		seconds = INT_MAX;
+#endif
+	it_new.it_value.tv_sec = seconds;
+	it_new.it_value.tv_nsec = 0;
+	it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
+
+	do_setitimer(ITIMER_REAL, &it_new, &it_old);
+
+	/*
+	 * We can't return 0 if we have an alarm pending ...  And we'd
+	 * better return too much than too little anyway
+	 */
+	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
+	      it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
+		it_old.it_value.tv_sec++;
+
+	return it_old.it_value.tv_sec;
+}
+
+/*
+ * For backwards compatibility?  This can be done in libc so Alpha
+ * and all newer ports shouldn't need it.
+ */
+SYSCALL_DEFINE1(alarm, unsigned int, seconds)
+{
+	return alarm_setitimer(seconds);
+}
+
+#endif
+
+static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
+{
+	struct __kernel_old_itimerval v;
+
+	if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval)))
+		return -EFAULT;
+
+	/* Validate the timevals in value. */
+	if (!timeval_valid(&v.it_value) ||
+	    !timeval_valid(&v.it_interval))
+		return -EINVAL;
+
+	o->it_interval.tv_sec = v.it_interval.tv_sec;
+	o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
+	o->it_value.tv_sec = v.it_value.tv_sec;
+	o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
+	return 0;
+}
+
+SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
+		struct __kernel_old_itimerval __user *, ovalue)
+{
+	struct itimerspec64 set_buffer, get_buffer;
+	int error;
+
+	if (value) {
+		error = get_itimerval(&set_buffer, value);
+		if (error)
+			return error;
+	} else {
+		memset(&set_buffer, 0, sizeof(set_buffer));
+		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
+			    " Misfeature support will be removed\n",
+			    current->comm);
+	}
+
+	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
+	if (error || !ovalue)
+		return error;
+
+	if (put_itimerval(ovalue, &get_buffer))
+		return -EFAULT;
+	return 0;
+}
+
+#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
+static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
+{
+	struct old_itimerval32 v32;
+
+	if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
+		return -EFAULT;
+
+	/* Validate the timevals in value.  */
+	if (!timeval_valid(&v32.it_value) ||
+	    !timeval_valid(&v32.it_interval))
+		return -EINVAL;
+
+	o->it_interval.tv_sec = v32.it_interval.tv_sec;
+	o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
+	o->it_value.tv_sec = v32.it_value.tv_sec;
+	o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
+	return 0;
+}
+
+COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
+		       struct old_itimerval32 __user *, value,
+		       struct old_itimerval32 __user *, ovalue)
+{
+	struct itimerspec64 set_buffer, get_buffer;
+	int error;
+
+	if (value) {
+		error = get_old_itimerval32(&set_buffer, value);
+		if (error)
+			return error;
+	} else {
+		memset(&set_buffer, 0, sizeof(set_buffer));
+		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
+			    " Misfeature support will be removed\n",
+			    current->comm);
+	}
+
+	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
+	if (error || !ovalue)
+		return error;
+	if (put_old_itimerval32(ovalue, &get_buffer))
+		return -EFAULT;
+	return 0;
+}
+#endif
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
new file mode 100644
index 0000000000..bc4db9e5ab
--- /dev/null
+++ b/kernel/time/jiffies.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * This file contains the jiffies based clocksource.
+ *
+ * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
+ */
+#include <linux/clocksource.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+#include "timekeeping.h"
+#include "tick-internal.h"
+
+
+static u64 jiffies_read(struct clocksource *cs)
+{
+	return (u64) jiffies;
+}
+
+/*
+ * The Jiffies based clocksource is the lowest common
+ * denominator clock source which should function on
+ * all systems. It has the same coarse resolution as
+ * the timer interrupt frequency HZ and it suffers
+ * inaccuracies caused by missed or lost timer
+ * interrupts and the inability for the timer
+ * interrupt hardware to accurately tick at the
+ * requested HZ value. It is also not recommended
+ * for "tick-less" systems.
+ */
+static struct clocksource clocksource_jiffies = {
+	.name			= "jiffies",
+	.rating			= 1, /* lowest valid rating*/
+	.uncertainty_margin	= 32 * NSEC_PER_MSEC,
+	.read			= jiffies_read,
+	.mask			= CLOCKSOURCE_MASK(32),
+	.mult			= TICK_NSEC << JIFFIES_SHIFT, /* details above */
+	.shift			= JIFFIES_SHIFT,
+	.max_cycles		= 10,
+};
+
+__cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(jiffies_lock);
+__cacheline_aligned_in_smp seqcount_raw_spinlock_t jiffies_seq =
+	SEQCNT_RAW_SPINLOCK_ZERO(jiffies_seq, &jiffies_lock);
+
+#if (BITS_PER_LONG < 64)
+u64 get_jiffies_64(void)
+{
+	unsigned int seq;
+	u64 ret;
+
+	do {
+		seq = read_seqcount_begin(&jiffies_seq);
+		ret = jiffies_64;
+	} while (read_seqcount_retry(&jiffies_seq, seq));
+	return ret;
+}
+EXPORT_SYMBOL(get_jiffies_64);
+#endif
+
+EXPORT_SYMBOL(jiffies);
+
+static int __init init_jiffies_clocksource(void)
+{
+	return __clocksource_register(&clocksource_jiffies);
+}
+
+core_initcall(init_jiffies_clocksource);
+
+struct clocksource * __init __weak clocksource_default_clock(void)
+{
+	return &clocksource_jiffies;
+}
+
+static struct clocksource refined_jiffies;
+
+int register_refined_jiffies(long cycles_per_second)
+{
+	u64 nsec_per_tick, shift_hz;
+	long cycles_per_tick;
+
+
+
+	refined_jiffies = clocksource_jiffies;
+	refined_jiffies.name = "refined-jiffies";
+	refined_jiffies.rating++;
+
+	/* Calc cycles per tick */
+	cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
+	/* shift_hz stores hz<<8 for extra accuracy */
+	shift_hz = (u64)cycles_per_second << 8;
+	shift_hz += cycles_per_tick/2;
+	do_div(shift_hz, cycles_per_tick);
+	/* Calculate nsec_per_tick using shift_hz */
+	nsec_per_tick = (u64)NSEC_PER_SEC << 8;
+	nsec_per_tick += (u32)shift_hz/2;
+	do_div(nsec_per_tick, (u32)shift_hz);
+
+	refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
+
+	__clocksource_register(&refined_jiffies);
+	return 0;
+}
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
new file mode 100644
index 0000000000..0775b9ec95
--- /dev/null
+++ b/kernel/time/namespace.c
@@ -0,0 +1,485 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: Andrei Vagin <avagin@openvz.org>
+ * Author: Dmitry Safonov <dima@arista.com>
+ */
+
+#include <linux/time_namespace.h>
+#include <linux/user_namespace.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/clocksource.h>
+#include <linux/seq_file.h>
+#include <linux/proc_ns.h>
+#include <linux/export.h>
+#include <linux/time.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+
+#include <vdso/datapage.h>
+
+ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
+				struct timens_offsets *ns_offsets)
+{
+	ktime_t offset;
+
+	switch (clockid) {
+	case CLOCK_MONOTONIC:
+		offset = timespec64_to_ktime(ns_offsets->monotonic);
+		break;
+	case CLOCK_BOOTTIME:
+	case CLOCK_BOOTTIME_ALARM:
+		offset = timespec64_to_ktime(ns_offsets->boottime);
+		break;
+	default:
+		return tim;
+	}
+
+	/*
+	 * Check that @tim value is in [offset, KTIME_MAX + offset]
+	 * and subtract offset.
+	 */
+	if (tim < offset) {
+		/*
+		 * User can specify @tim *absolute* value - if it's lesser than
+		 * the time namespace's offset - it's already expired.
+		 */
+		tim = 0;
+	} else {
+		tim = ktime_sub(tim, offset);
+		if (unlikely(tim > KTIME_MAX))
+			tim = KTIME_MAX;
+	}
+
+	return tim;
+}
+
+static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
+{
+	return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
+}
+
+static void dec_time_namespaces(struct ucounts *ucounts)
+{
+	dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
+}
+
+/**
+ * clone_time_ns - Clone a time namespace
+ * @user_ns:	User namespace which owns a new namespace.
+ * @old_ns:	Namespace to clone
+ *
+ * Clone @old_ns and set the clone refcount to 1
+ *
+ * Return: The new namespace or ERR_PTR.
+ */
+static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
+					  struct time_namespace *old_ns)
+{
+	struct time_namespace *ns;
+	struct ucounts *ucounts;
+	int err;
+
+	err = -ENOSPC;
+	ucounts = inc_time_namespaces(user_ns);
+	if (!ucounts)
+		goto fail;
+
+	err = -ENOMEM;
+	ns = kmalloc(sizeof(*ns), GFP_KERNEL_ACCOUNT);
+	if (!ns)
+		goto fail_dec;
+
+	refcount_set(&ns->ns.count, 1);
+
+	ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	if (!ns->vvar_page)
+		goto fail_free;
+
+	err = ns_alloc_inum(&ns->ns);
+	if (err)
+		goto fail_free_page;
+
+	ns->ucounts = ucounts;
+	ns->ns.ops = &timens_operations;
+	ns->user_ns = get_user_ns(user_ns);
+	ns->offsets = old_ns->offsets;
+	ns->frozen_offsets = false;
+	return ns;
+
+fail_free_page:
+	__free_page(ns->vvar_page);
+fail_free:
+	kfree(ns);
+fail_dec:
+	dec_time_namespaces(ucounts);
+fail:
+	return ERR_PTR(err);
+}
+
+/**
+ * copy_time_ns - Create timens_for_children from @old_ns
+ * @flags:	Cloning flags
+ * @user_ns:	User namespace which owns a new namespace.
+ * @old_ns:	Namespace to clone
+ *
+ * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children;
+ * adds a refcounter to @old_ns otherwise.
+ *
+ * Return: timens_for_children namespace or ERR_PTR.
+ */
+struct time_namespace *copy_time_ns(unsigned long flags,
+	struct user_namespace *user_ns, struct time_namespace *old_ns)
+{
+	if (!(flags & CLONE_NEWTIME))
+		return get_time_ns(old_ns);
+
+	return clone_time_ns(user_ns, old_ns);
+}
+
+static struct timens_offset offset_from_ts(struct timespec64 off)
+{
+	struct timens_offset ret;
+
+	ret.sec = off.tv_sec;
+	ret.nsec = off.tv_nsec;
+
+	return ret;
+}
+
+/*
+ * A time namespace VVAR page has the same layout as the VVAR page which
+ * contains the system wide VDSO data.
+ *
+ * For a normal task the VVAR pages are installed in the normal ordering:
+ *     VVAR
+ *     PVCLOCK
+ *     HVCLOCK
+ *     TIMENS   <- Not really required
+ *
+ * Now for a timens task the pages are installed in the following order:
+ *     TIMENS
+ *     PVCLOCK
+ *     HVCLOCK
+ *     VVAR
+ *
+ * The check for vdso_data->clock_mode is in the unlikely path of
+ * the seq begin magic. So for the non-timens case most of the time
+ * 'seq' is even, so the branch is not taken.
+ *
+ * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
+ * for vdso_data->clock_mode is a non-issue. The task is spin waiting for the
+ * update to finish and for 'seq' to become even anyway.
+ *
+ * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which
+ * enforces the time namespace handling path.
+ */
+static void timens_setup_vdso_data(struct vdso_data *vdata,
+				   struct time_namespace *ns)
+{
+	struct timens_offset *offset = vdata->offset;
+	struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
+	struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
+
+	vdata->seq			= 1;
+	vdata->clock_mode		= VDSO_CLOCKMODE_TIMENS;
+	offset[CLOCK_MONOTONIC]		= monotonic;
+	offset[CLOCK_MONOTONIC_RAW]	= monotonic;
+	offset[CLOCK_MONOTONIC_COARSE]	= monotonic;
+	offset[CLOCK_BOOTTIME]		= boottime;
+	offset[CLOCK_BOOTTIME_ALARM]	= boottime;
+}
+
+struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+	if (likely(vma->vm_mm == current->mm))
+		return current->nsproxy->time_ns->vvar_page;
+
+	/*
+	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
+	 * through interfaces like /proc/$pid/mem or
+	 * process_vm_{readv,writev}() as long as there's no .access()
+	 * in special_mapping_vmops().
+	 * For more details check_vma_flags() and __access_remote_vm()
+	 */
+
+	WARN(1, "vvar_page accessed remotely");
+
+	return NULL;
+}
+
+/*
+ * Protects possibly multiple offsets writers racing each other
+ * and tasks entering the namespace.
+ */
+static DEFINE_MUTEX(offset_lock);
+
+static void timens_set_vvar_page(struct task_struct *task,
+				struct time_namespace *ns)
+{
+	struct vdso_data *vdata;
+	unsigned int i;
+
+	if (ns == &init_time_ns)
+		return;
+
+	/* Fast-path, taken by every task in namespace except the first. */
+	if (likely(ns->frozen_offsets))
+		return;
+
+	mutex_lock(&offset_lock);
+	/* Nothing to-do: vvar_page has been already initialized. */
+	if (ns->frozen_offsets)
+		goto out;
+
+	ns->frozen_offsets = true;
+	vdata = arch_get_vdso_data(page_address(ns->vvar_page));
+
+	for (i = 0; i < CS_BASES; i++)
+		timens_setup_vdso_data(&vdata[i], ns);
+
+out:
+	mutex_unlock(&offset_lock);
+}
+
+void free_time_ns(struct time_namespace *ns)
+{
+	dec_time_namespaces(ns->ucounts);
+	put_user_ns(ns->user_ns);
+	ns_free_inum(&ns->ns);
+	__free_page(ns->vvar_page);
+	kfree(ns);
+}
+
+static struct time_namespace *to_time_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct time_namespace, ns);
+}
+
+static struct ns_common *timens_get(struct task_struct *task)
+{
+	struct time_namespace *ns = NULL;
+	struct nsproxy *nsproxy;
+
+	task_lock(task);
+	nsproxy = task->nsproxy;
+	if (nsproxy) {
+		ns = nsproxy->time_ns;
+		get_time_ns(ns);
+	}
+	task_unlock(task);
+
+	return ns ? &ns->ns : NULL;
+}
+
+static struct ns_common *timens_for_children_get(struct task_struct *task)
+{
+	struct time_namespace *ns = NULL;
+	struct nsproxy *nsproxy;
+
+	task_lock(task);
+	nsproxy = task->nsproxy;
+	if (nsproxy) {
+		ns = nsproxy->time_ns_for_children;
+		get_time_ns(ns);
+	}
+	task_unlock(task);
+
+	return ns ? &ns->ns : NULL;
+}
+
+static void timens_put(struct ns_common *ns)
+{
+	put_time_ns(to_time_ns(ns));
+}
+
+void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
+{
+	timens_set_vvar_page(tsk, ns);
+	vdso_join_timens(tsk, ns);
+}
+
+static int timens_install(struct nsset *nsset, struct ns_common *new)
+{
+	struct nsproxy *nsproxy = nsset->nsproxy;
+	struct time_namespace *ns = to_time_ns(new);
+
+	if (!current_is_single_threaded())
+		return -EUSERS;
+
+	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
+	    !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
+		return -EPERM;
+
+	get_time_ns(ns);
+	put_time_ns(nsproxy->time_ns);
+	nsproxy->time_ns = ns;
+
+	get_time_ns(ns);
+	put_time_ns(nsproxy->time_ns_for_children);
+	nsproxy->time_ns_for_children = ns;
+	return 0;
+}
+
+void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
+{
+	struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
+	struct time_namespace *ns = to_time_ns(nsc);
+
+	/* create_new_namespaces() already incremented the ref counter */
+	if (nsproxy->time_ns == nsproxy->time_ns_for_children)
+		return;
+
+	get_time_ns(ns);
+	put_time_ns(nsproxy->time_ns);
+	nsproxy->time_ns = ns;
+
+	timens_commit(tsk, ns);
+}
+
+static struct user_namespace *timens_owner(struct ns_common *ns)
+{
+	return to_time_ns(ns)->user_ns;
+}
+
+static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts)
+{
+	char *clock;
+
+	switch (clockid) {
+	case CLOCK_BOOTTIME:
+		clock = "boottime";
+		break;
+	case CLOCK_MONOTONIC:
+		clock = "monotonic";
+		break;
+	default:
+		clock = "unknown";
+		break;
+	}
+	seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec);
+}
+
+void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m)
+{
+	struct ns_common *ns;
+	struct time_namespace *time_ns;
+
+	ns = timens_for_children_get(p);
+	if (!ns)
+		return;
+	time_ns = to_time_ns(ns);
+
+	show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic);
+	show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime);
+	put_time_ns(time_ns);
+}
+
+int proc_timens_set_offset(struct file *file, struct task_struct *p,
+			   struct proc_timens_offset *offsets, int noffsets)
+{
+	struct ns_common *ns;
+	struct time_namespace *time_ns;
+	struct timespec64 tp;
+	int i, err;
+
+	ns = timens_for_children_get(p);
+	if (!ns)
+		return -ESRCH;
+	time_ns = to_time_ns(ns);
+
+	if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) {
+		put_time_ns(time_ns);
+		return -EPERM;
+	}
+
+	for (i = 0; i < noffsets; i++) {
+		struct proc_timens_offset *off = &offsets[i];
+
+		switch (off->clockid) {
+		case CLOCK_MONOTONIC:
+			ktime_get_ts64(&tp);
+			break;
+		case CLOCK_BOOTTIME:
+			ktime_get_boottime_ts64(&tp);
+			break;
+		default:
+			err = -EINVAL;
+			goto out;
+		}
+
+		err = -ERANGE;
+
+		if (off->val.tv_sec > KTIME_SEC_MAX ||
+		    off->val.tv_sec < -KTIME_SEC_MAX)
+			goto out;
+
+		tp = timespec64_add(tp, off->val);
+		/*
+		 * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is
+		 * still unreachable.
+		 */
+		if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2)
+			goto out;
+	}
+
+	mutex_lock(&offset_lock);
+	if (time_ns->frozen_offsets) {
+		err = -EACCES;
+		goto out_unlock;
+	}
+
+	err = 0;
+	/* Don't report errors after this line */
+	for (i = 0; i < noffsets; i++) {
+		struct proc_timens_offset *off = &offsets[i];
+		struct timespec64 *offset = NULL;
+
+		switch (off->clockid) {
+		case CLOCK_MONOTONIC:
+			offset = &time_ns->offsets.monotonic;
+			break;
+		case CLOCK_BOOTTIME:
+			offset = &time_ns->offsets.boottime;
+			break;
+		}
+
+		*offset = off->val;
+	}
+
+out_unlock:
+	mutex_unlock(&offset_lock);
+out:
+	put_time_ns(time_ns);
+
+	return err;
+}
+
+const struct proc_ns_operations timens_operations = {
+	.name		= "time",
+	.type		= CLONE_NEWTIME,
+	.get		= timens_get,
+	.put		= timens_put,
+	.install	= timens_install,
+	.owner		= timens_owner,
+};
+
+const struct proc_ns_operations timens_for_children_operations = {
+	.name		= "time_for_children",
+	.real_ns_name	= "time",
+	.type		= CLONE_NEWTIME,
+	.get		= timens_for_children_get,
+	.put		= timens_put,
+	.install	= timens_install,
+	.owner		= timens_owner,
+};
+
+struct time_namespace init_time_ns = {
+	.ns.count	= REFCOUNT_INIT(3),
+	.user_ns	= &init_user_ns,
+	.ns.inum	= PROC_TIME_INIT_INO,
+	.ns.ops		= &timens_operations,
+	.frozen_offsets	= true,
+};
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
new file mode 100644
index 0000000000..406dccb79c
--- /dev/null
+++ b/kernel/time/ntp.c
@@ -0,0 +1,1096 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * NTP state machine interfaces and logic.
+ *
+ * This code was mainly moved from kernel/timer.c and kernel/time.c
+ * Please see those files for relevant copyright info and historical
+ * changelogs.
+ */
+#include <linux/capability.h>
+#include <linux/clocksource.h>
+#include <linux/workqueue.h>
+#include <linux/hrtimer.h>
+#include <linux/jiffies.h>
+#include <linux/math64.h>
+#include <linux/timex.h>
+#include <linux/time.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/audit.h>
+
+#include "ntp_internal.h"
+#include "timekeeping_internal.h"
+
+
+/*
+ * NTP timekeeping variables:
+ *
+ * Note: All of the NTP state is protected by the timekeeping locks.
+ */
+
+
+/* USER_HZ period (usecs): */
+unsigned long			tick_usec = USER_TICK_USEC;
+
+/* SHIFTED_HZ period (nsecs): */
+unsigned long			tick_nsec;
+
+static u64			tick_length;
+static u64			tick_length_base;
+
+#define SECS_PER_DAY		86400
+#define MAX_TICKADJ		500LL		/* usecs */
+#define MAX_TICKADJ_SCALED \
+	(((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
+#define MAX_TAI_OFFSET		100000
+
+/*
+ * phase-lock loop variables
+ */
+
+/*
+ * clock synchronization status
+ *
+ * (TIME_ERROR prevents overwriting the CMOS clock)
+ */
+static int			time_state = TIME_OK;
+
+/* clock status bits:							*/
+static int			time_status = STA_UNSYNC;
+
+/* time adjustment (nsecs):						*/
+static s64			time_offset;
+
+/* pll time constant:							*/
+static long			time_constant = 2;
+
+/* maximum error (usecs):						*/
+static long			time_maxerror = NTP_PHASE_LIMIT;
+
+/* estimated error (usecs):						*/
+static long			time_esterror = NTP_PHASE_LIMIT;
+
+/* frequency offset (scaled nsecs/secs):				*/
+static s64			time_freq;
+
+/* time at last adjustment (secs):					*/
+static time64_t		time_reftime;
+
+static long			time_adjust;
+
+/* constant (boot-param configurable) NTP tick adjustment (upscaled)	*/
+static s64			ntp_tick_adj;
+
+/* second value of the next pending leapsecond, or TIME64_MAX if no leap */
+static time64_t			ntp_next_leap_sec = TIME64_MAX;
+
+#ifdef CONFIG_NTP_PPS
+
+/*
+ * The following variables are used when a pulse-per-second (PPS) signal
+ * is available. They establish the engineering parameters of the clock
+ * discipline loop when controlled by the PPS signal.
+ */
+#define PPS_VALID	10	/* PPS signal watchdog max (s) */
+#define PPS_POPCORN	4	/* popcorn spike threshold (shift) */
+#define PPS_INTMIN	2	/* min freq interval (s) (shift) */
+#define PPS_INTMAX	8	/* max freq interval (s) (shift) */
+#define PPS_INTCOUNT	4	/* number of consecutive good intervals to
+				   increase pps_shift or consecutive bad
+				   intervals to decrease it */
+#define PPS_MAXWANDER	100000	/* max PPS freq wander (ns/s) */
+
+static int pps_valid;		/* signal watchdog counter */
+static long pps_tf[3];		/* phase median filter */
+static long pps_jitter;		/* current jitter (ns) */
+static struct timespec64 pps_fbase; /* beginning of the last freq interval */
+static int pps_shift;		/* current interval duration (s) (shift) */
+static int pps_intcnt;		/* interval counter */
+static s64 pps_freq;		/* frequency offset (scaled ns/s) */
+static long pps_stabil;		/* current stability (scaled ns/s) */
+
+/*
+ * PPS signal quality monitors
+ */
+static long pps_calcnt;		/* calibration intervals */
+static long pps_jitcnt;		/* jitter limit exceeded */
+static long pps_stbcnt;		/* stability limit exceeded */
+static long pps_errcnt;		/* calibration errors */
+
+
+/* PPS kernel consumer compensates the whole phase error immediately.
+ * Otherwise, reduce the offset by a fixed factor times the time constant.
+ */
+static inline s64 ntp_offset_chunk(s64 offset)
+{
+	if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
+		return offset;
+	else
+		return shift_right(offset, SHIFT_PLL + time_constant);
+}
+
+static inline void pps_reset_freq_interval(void)
+{
+	/* the PPS calibration interval may end
+	   surprisingly early */
+	pps_shift = PPS_INTMIN;
+	pps_intcnt = 0;
+}
+
+/**
+ * pps_clear - Clears the PPS state variables
+ */
+static inline void pps_clear(void)
+{
+	pps_reset_freq_interval();
+	pps_tf[0] = 0;
+	pps_tf[1] = 0;
+	pps_tf[2] = 0;
+	pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
+	pps_freq = 0;
+}
+
+/* Decrease pps_valid to indicate that another second has passed since
+ * the last PPS signal. When it reaches 0, indicate that PPS signal is
+ * missing.
+ */
+static inline void pps_dec_valid(void)
+{
+	if (pps_valid > 0)
+		pps_valid--;
+	else {
+		time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
+				 STA_PPSWANDER | STA_PPSERROR);
+		pps_clear();
+	}
+}
+
+static inline void pps_set_freq(s64 freq)
+{
+	pps_freq = freq;
+}
+
+static inline int is_error_status(int status)
+{
+	return (status & (STA_UNSYNC|STA_CLOCKERR))
+		/* PPS signal lost when either PPS time or
+		 * PPS frequency synchronization requested
+		 */
+		|| ((status & (STA_PPSFREQ|STA_PPSTIME))
+			&& !(status & STA_PPSSIGNAL))
+		/* PPS jitter exceeded when
+		 * PPS time synchronization requested */
+		|| ((status & (STA_PPSTIME|STA_PPSJITTER))
+			== (STA_PPSTIME|STA_PPSJITTER))
+		/* PPS wander exceeded or calibration error when
+		 * PPS frequency synchronization requested
+		 */
+		|| ((status & STA_PPSFREQ)
+			&& (status & (STA_PPSWANDER|STA_PPSERROR)));
+}
+
+static inline void pps_fill_timex(struct __kernel_timex *txc)
+{
+	txc->ppsfreq	   = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
+					 PPM_SCALE_INV, NTP_SCALE_SHIFT);
+	txc->jitter	   = pps_jitter;
+	if (!(time_status & STA_NANO))
+		txc->jitter = pps_jitter / NSEC_PER_USEC;
+	txc->shift	   = pps_shift;
+	txc->stabil	   = pps_stabil;
+	txc->jitcnt	   = pps_jitcnt;
+	txc->calcnt	   = pps_calcnt;
+	txc->errcnt	   = pps_errcnt;
+	txc->stbcnt	   = pps_stbcnt;
+}
+
+#else /* !CONFIG_NTP_PPS */
+
+static inline s64 ntp_offset_chunk(s64 offset)
+{
+	return shift_right(offset, SHIFT_PLL + time_constant);
+}
+
+static inline void pps_reset_freq_interval(void) {}
+static inline void pps_clear(void) {}
+static inline void pps_dec_valid(void) {}
+static inline void pps_set_freq(s64 freq) {}
+
+static inline int is_error_status(int status)
+{
+	return status & (STA_UNSYNC|STA_CLOCKERR);
+}
+
+static inline void pps_fill_timex(struct __kernel_timex *txc)
+{
+	/* PPS is not implemented, so these are zero */
+	txc->ppsfreq	   = 0;
+	txc->jitter	   = 0;
+	txc->shift	   = 0;
+	txc->stabil	   = 0;
+	txc->jitcnt	   = 0;
+	txc->calcnt	   = 0;
+	txc->errcnt	   = 0;
+	txc->stbcnt	   = 0;
+}
+
+#endif /* CONFIG_NTP_PPS */
+
+
+/**
+ * ntp_synced - Returns 1 if the NTP status is not UNSYNC
+ *
+ */
+static inline int ntp_synced(void)
+{
+	return !(time_status & STA_UNSYNC);
+}
+
+
+/*
+ * NTP methods:
+ */
+
+/*
+ * Update (tick_length, tick_length_base, tick_nsec), based
+ * on (tick_usec, ntp_tick_adj, time_freq):
+ */
+static void ntp_update_frequency(void)
+{
+	u64 second_length;
+	u64 new_base;
+
+	second_length		 = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
+						<< NTP_SCALE_SHIFT;
+
+	second_length		+= ntp_tick_adj;
+	second_length		+= time_freq;
+
+	tick_nsec		 = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
+	new_base		 = div_u64(second_length, NTP_INTERVAL_FREQ);
+
+	/*
+	 * Don't wait for the next second_overflow, apply
+	 * the change to the tick length immediately:
+	 */
+	tick_length		+= new_base - tick_length_base;
+	tick_length_base	 = new_base;
+}
+
+static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
+{
+	time_status &= ~STA_MODE;
+
+	if (secs < MINSEC)
+		return 0;
+
+	if (!(time_status & STA_FLL) && (secs <= MAXSEC))
+		return 0;
+
+	time_status |= STA_MODE;
+
+	return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
+}
+
+static void ntp_update_offset(long offset)
+{
+	s64 freq_adj;
+	s64 offset64;
+	long secs;
+
+	if (!(time_status & STA_PLL))
+		return;
+
+	if (!(time_status & STA_NANO)) {
+		/* Make sure the multiplication below won't overflow */
+		offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
+		offset *= NSEC_PER_USEC;
+	}
+
+	/*
+	 * Scale the phase adjustment and
+	 * clamp to the operating range.
+	 */
+	offset = clamp(offset, -MAXPHASE, MAXPHASE);
+
+	/*
+	 * Select how the frequency is to be controlled
+	 * and in which mode (PLL or FLL).
+	 */
+	secs = (long)(__ktime_get_real_seconds() - time_reftime);
+	if (unlikely(time_status & STA_FREQHOLD))
+		secs = 0;
+
+	time_reftime = __ktime_get_real_seconds();
+
+	offset64    = offset;
+	freq_adj    = ntp_update_offset_fll(offset64, secs);
+
+	/*
+	 * Clamp update interval to reduce PLL gain with low
+	 * sampling rate (e.g. intermittent network connection)
+	 * to avoid instability.
+	 */
+	if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
+		secs = 1 << (SHIFT_PLL + 1 + time_constant);
+
+	freq_adj    += (offset64 * secs) <<
+			(NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
+
+	freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
+
+	time_freq   = max(freq_adj, -MAXFREQ_SCALED);
+
+	time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
+}
+
+/**
+ * ntp_clear - Clears the NTP state variables
+ */
+void ntp_clear(void)
+{
+	time_adjust	= 0;		/* stop active adjtime() */
+	time_status	|= STA_UNSYNC;
+	time_maxerror	= NTP_PHASE_LIMIT;
+	time_esterror	= NTP_PHASE_LIMIT;
+
+	ntp_update_frequency();
+
+	tick_length	= tick_length_base;
+	time_offset	= 0;
+
+	ntp_next_leap_sec = TIME64_MAX;
+	/* Clear PPS state variables */
+	pps_clear();
+}
+
+
+u64 ntp_tick_length(void)
+{
+	return tick_length;
+}
+
+/**
+ * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
+ *
+ * Provides the time of the next leapsecond against CLOCK_REALTIME in
+ * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
+ */
+ktime_t ntp_get_next_leap(void)
+{
+	ktime_t ret;
+
+	if ((time_state == TIME_INS) && (time_status & STA_INS))
+		return ktime_set(ntp_next_leap_sec, 0);
+	ret = KTIME_MAX;
+	return ret;
+}
+
+/*
+ * this routine handles the overflow of the microsecond field
+ *
+ * The tricky bits of code to handle the accurate clock support
+ * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
+ * They were originally developed for SUN and DEC kernels.
+ * All the kudos should go to Dave for this stuff.
+ *
+ * Also handles leap second processing, and returns leap offset
+ */
+int second_overflow(time64_t secs)
+{
+	s64 delta;
+	int leap = 0;
+	s32 rem;
+
+	/*
+	 * Leap second processing. If in leap-insert state at the end of the
+	 * day, the system clock is set back one second; if in leap-delete
+	 * state, the system clock is set ahead one second.
+	 */
+	switch (time_state) {
+	case TIME_OK:
+		if (time_status & STA_INS) {
+			time_state = TIME_INS;
+			div_s64_rem(secs, SECS_PER_DAY, &rem);
+			ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
+		} else if (time_status & STA_DEL) {
+			time_state = TIME_DEL;
+			div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
+			ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
+		}
+		break;
+	case TIME_INS:
+		if (!(time_status & STA_INS)) {
+			ntp_next_leap_sec = TIME64_MAX;
+			time_state = TIME_OK;
+		} else if (secs == ntp_next_leap_sec) {
+			leap = -1;
+			time_state = TIME_OOP;
+			printk(KERN_NOTICE
+				"Clock: inserting leap second 23:59:60 UTC\n");
+		}
+		break;
+	case TIME_DEL:
+		if (!(time_status & STA_DEL)) {
+			ntp_next_leap_sec = TIME64_MAX;
+			time_state = TIME_OK;
+		} else if (secs == ntp_next_leap_sec) {
+			leap = 1;
+			ntp_next_leap_sec = TIME64_MAX;
+			time_state = TIME_WAIT;
+			printk(KERN_NOTICE
+				"Clock: deleting leap second 23:59:59 UTC\n");
+		}
+		break;
+	case TIME_OOP:
+		ntp_next_leap_sec = TIME64_MAX;
+		time_state = TIME_WAIT;
+		break;
+	case TIME_WAIT:
+		if (!(time_status & (STA_INS | STA_DEL)))
+			time_state = TIME_OK;
+		break;
+	}
+
+
+	/* Bump the maxerror field */
+	time_maxerror += MAXFREQ / NSEC_PER_USEC;
+	if (time_maxerror > NTP_PHASE_LIMIT) {
+		time_maxerror = NTP_PHASE_LIMIT;
+		time_status |= STA_UNSYNC;
+	}
+
+	/* Compute the phase adjustment for the next second */
+	tick_length	 = tick_length_base;
+
+	delta		 = ntp_offset_chunk(time_offset);
+	time_offset	-= delta;
+	tick_length	+= delta;
+
+	/* Check PPS signal */
+	pps_dec_valid();
+
+	if (!time_adjust)
+		goto out;
+
+	if (time_adjust > MAX_TICKADJ) {
+		time_adjust -= MAX_TICKADJ;
+		tick_length += MAX_TICKADJ_SCALED;
+		goto out;
+	}
+
+	if (time_adjust < -MAX_TICKADJ) {
+		time_adjust += MAX_TICKADJ;
+		tick_length -= MAX_TICKADJ_SCALED;
+		goto out;
+	}
+
+	tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
+							 << NTP_SCALE_SHIFT;
+	time_adjust = 0;
+
+out:
+	return leap;
+}
+
+#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
+static void sync_hw_clock(struct work_struct *work);
+static DECLARE_WORK(sync_work, sync_hw_clock);
+static struct hrtimer sync_hrtimer;
+#define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
+
+static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
+{
+	queue_work(system_freezable_power_efficient_wq, &sync_work);
+
+	return HRTIMER_NORESTART;
+}
+
+static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
+{
+	ktime_t exp = ktime_set(ktime_get_real_seconds(), 0);
+
+	if (retry)
+		exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
+	else
+		exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);
+
+	hrtimer_start(&sync_hrtimer, exp, HRTIMER_MODE_ABS);
+}
+
+/*
+ * Check whether @now is correct versus the required time to update the RTC
+ * and calculate the value which needs to be written to the RTC so that the
+ * next seconds increment of the RTC after the write is aligned with the next
+ * seconds increment of clock REALTIME.
+ *
+ * tsched     t1 write(t2.tv_sec - 1sec))	t2 RTC increments seconds
+ *
+ * t2.tv_nsec == 0
+ * tsched = t2 - set_offset_nsec
+ * newval = t2 - NSEC_PER_SEC
+ *
+ * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
+ *
+ * As the execution of this code is not guaranteed to happen exactly at
+ * tsched this allows it to happen within a fuzzy region:
+ *
+ *	abs(now - tsched) < FUZZ
+ *
+ * If @now is not inside the allowed window the function returns false.
+ */
+static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
+				  struct timespec64 *to_set,
+				  const struct timespec64 *now)
+{
+	/* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
+	const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
+	struct timespec64 delay = {.tv_sec = -1,
+				   .tv_nsec = set_offset_nsec};
+
+	*to_set = timespec64_add(*now, delay);
+
+	if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
+		to_set->tv_nsec = 0;
+		return true;
+	}
+
+	if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
+		to_set->tv_sec++;
+		to_set->tv_nsec = 0;
+		return true;
+	}
+	return false;
+}
+
+#ifdef CONFIG_GENERIC_CMOS_UPDATE
+int __weak update_persistent_clock64(struct timespec64 now64)
+{
+	return -ENODEV;
+}
+#else
+static inline int update_persistent_clock64(struct timespec64 now64)
+{
+	return -ENODEV;
+}
+#endif
+
+#ifdef CONFIG_RTC_SYSTOHC
+/* Save NTP synchronized time to the RTC */
+static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
+{
+	struct rtc_device *rtc;
+	struct rtc_time tm;
+	int err = -ENODEV;
+
+	rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
+	if (!rtc)
+		return -ENODEV;
+
+	if (!rtc->ops || !rtc->ops->set_time)
+		goto out_close;
+
+	/* First call might not have the correct offset */
+	if (*offset_nsec == rtc->set_offset_nsec) {
+		rtc_time64_to_tm(to_set->tv_sec, &tm);
+		err = rtc_set_time(rtc, &tm);
+	} else {
+		/* Store the update offset and let the caller try again */
+		*offset_nsec = rtc->set_offset_nsec;
+		err = -EAGAIN;
+	}
+out_close:
+	rtc_class_close(rtc);
+	return err;
+}
+#else
+static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
+{
+	return -ENODEV;
+}
+#endif
+
+/*
+ * If we have an externally synchronized Linux clock, then update RTC clock
+ * accordingly every ~11 minutes. Generally RTCs can only store second
+ * precision, but many RTCs will adjust the phase of their second tick to
+ * match the moment of update. This infrastructure arranges to call to the RTC
+ * set at the correct moment to phase synchronize the RTC second tick over
+ * with the kernel clock.
+ */
+static void sync_hw_clock(struct work_struct *work)
+{
+	/*
+	 * The default synchronization offset is 500ms for the deprecated
+	 * update_persistent_clock64() under the assumption that it uses
+	 * the infamous CMOS clock (MC146818).
+	 */
+	static unsigned long offset_nsec = NSEC_PER_SEC / 2;
+	struct timespec64 now, to_set;
+	int res = -EAGAIN;
+
+	/*
+	 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
+	 * managed to schedule the work between the timer firing and the
+	 * work being able to rearm the timer. Wait for the timer to expire.
+	 */
+	if (!ntp_synced() || hrtimer_is_queued(&sync_hrtimer))
+		return;
+
+	ktime_get_real_ts64(&now);
+	/* If @now is not in the allowed window, try again */
+	if (!rtc_tv_nsec_ok(offset_nsec, &to_set, &now))
+		goto rearm;
+
+	/* Take timezone adjusted RTCs into account */
+	if (persistent_clock_is_local)
+		to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);
+
+	/* Try the legacy RTC first. */
+	res = update_persistent_clock64(to_set);
+	if (res != -ENODEV)
+		goto rearm;
+
+	/* Try the RTC class */
+	res = update_rtc(&to_set, &offset_nsec);
+	if (res == -ENODEV)
+		return;
+rearm:
+	sched_sync_hw_clock(offset_nsec, res != 0);
+}
+
+void ntp_notify_cmos_timer(void)
+{
+	/*
+	 * When the work is currently executed but has not yet the timer
+	 * rearmed this queues the work immediately again. No big issue,
+	 * just a pointless work scheduled.
+	 */
+	if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
+		queue_work(system_freezable_power_efficient_wq, &sync_work);
+}
+
+static void __init ntp_init_cmos_sync(void)
+{
+	hrtimer_init(&sync_hrtimer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+	sync_hrtimer.function = sync_timer_callback;
+}
+#else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
+static inline void __init ntp_init_cmos_sync(void) { }
+#endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
+
+/*
+ * Propagate a new txc->status value into the NTP state:
+ */
+static inline void process_adj_status(const struct __kernel_timex *txc)
+{
+	if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
+		time_state = TIME_OK;
+		time_status = STA_UNSYNC;
+		ntp_next_leap_sec = TIME64_MAX;
+		/* restart PPS frequency calibration */
+		pps_reset_freq_interval();
+	}
+
+	/*
+	 * If we turn on PLL adjustments then reset the
+	 * reference time to current time.
+	 */
+	if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
+		time_reftime = __ktime_get_real_seconds();
+
+	/* only set allowed bits */
+	time_status &= STA_RONLY;
+	time_status |= txc->status & ~STA_RONLY;
+}
+
+
+static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
+					  s32 *time_tai)
+{
+	if (txc->modes & ADJ_STATUS)
+		process_adj_status(txc);
+
+	if (txc->modes & ADJ_NANO)
+		time_status |= STA_NANO;
+
+	if (txc->modes & ADJ_MICRO)
+		time_status &= ~STA_NANO;
+
+	if (txc->modes & ADJ_FREQUENCY) {
+		time_freq = txc->freq * PPM_SCALE;
+		time_freq = min(time_freq, MAXFREQ_SCALED);
+		time_freq = max(time_freq, -MAXFREQ_SCALED);
+		/* update pps_freq */
+		pps_set_freq(time_freq);
+	}
+
+	if (txc->modes & ADJ_MAXERROR)
+		time_maxerror = txc->maxerror;
+
+	if (txc->modes & ADJ_ESTERROR)
+		time_esterror = txc->esterror;
+
+	if (txc->modes & ADJ_TIMECONST) {
+		time_constant = txc->constant;
+		if (!(time_status & STA_NANO))
+			time_constant += 4;
+		time_constant = min(time_constant, (long)MAXTC);
+		time_constant = max(time_constant, 0l);
+	}
+
+	if (txc->modes & ADJ_TAI &&
+			txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
+		*time_tai = txc->constant;
+
+	if (txc->modes & ADJ_OFFSET)
+		ntp_update_offset(txc->offset);
+
+	if (txc->modes & ADJ_TICK)
+		tick_usec = txc->tick;
+
+	if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
+		ntp_update_frequency();
+}
+
+
+/*
+ * adjtimex mainly allows reading (and writing, if superuser) of
+ * kernel time-keeping variables. used by xntpd.
+ */
+int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
+		  s32 *time_tai, struct audit_ntp_data *ad)
+{
+	int result;
+
+	if (txc->modes & ADJ_ADJTIME) {
+		long save_adjust = time_adjust;
+
+		if (!(txc->modes & ADJ_OFFSET_READONLY)) {
+			/* adjtime() is independent from ntp_adjtime() */
+			time_adjust = txc->offset;
+			ntp_update_frequency();
+
+			audit_ntp_set_old(ad, AUDIT_NTP_ADJUST,	save_adjust);
+			audit_ntp_set_new(ad, AUDIT_NTP_ADJUST,	time_adjust);
+		}
+		txc->offset = save_adjust;
+	} else {
+		/* If there are input parameters, then process them: */
+		if (txc->modes) {
+			audit_ntp_set_old(ad, AUDIT_NTP_OFFSET,	time_offset);
+			audit_ntp_set_old(ad, AUDIT_NTP_FREQ,	time_freq);
+			audit_ntp_set_old(ad, AUDIT_NTP_STATUS,	time_status);
+			audit_ntp_set_old(ad, AUDIT_NTP_TAI,	*time_tai);
+			audit_ntp_set_old(ad, AUDIT_NTP_TICK,	tick_usec);
+
+			process_adjtimex_modes(txc, time_tai);
+
+			audit_ntp_set_new(ad, AUDIT_NTP_OFFSET,	time_offset);
+			audit_ntp_set_new(ad, AUDIT_NTP_FREQ,	time_freq);
+			audit_ntp_set_new(ad, AUDIT_NTP_STATUS,	time_status);
+			audit_ntp_set_new(ad, AUDIT_NTP_TAI,	*time_tai);
+			audit_ntp_set_new(ad, AUDIT_NTP_TICK,	tick_usec);
+		}
+
+		txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
+				  NTP_SCALE_SHIFT);
+		if (!(time_status & STA_NANO))
+			txc->offset = (u32)txc->offset / NSEC_PER_USEC;
+	}
+
+	result = time_state;	/* mostly `TIME_OK' */
+	/* check for errors */
+	if (is_error_status(time_status))
+		result = TIME_ERROR;
+
+	txc->freq	   = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
+					 PPM_SCALE_INV, NTP_SCALE_SHIFT);
+	txc->maxerror	   = time_maxerror;
+	txc->esterror	   = time_esterror;
+	txc->status	   = time_status;
+	txc->constant	   = time_constant;
+	txc->precision	   = 1;
+	txc->tolerance	   = MAXFREQ_SCALED / PPM_SCALE;
+	txc->tick	   = tick_usec;
+	txc->tai	   = *time_tai;
+
+	/* fill PPS status fields */
+	pps_fill_timex(txc);
+
+	txc->time.tv_sec = ts->tv_sec;
+	txc->time.tv_usec = ts->tv_nsec;
+	if (!(time_status & STA_NANO))
+		txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
+
+	/* Handle leapsec adjustments */
+	if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
+		if ((time_state == TIME_INS) && (time_status & STA_INS)) {
+			result = TIME_OOP;
+			txc->tai++;
+			txc->time.tv_sec--;
+		}
+		if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
+			result = TIME_WAIT;
+			txc->tai--;
+			txc->time.tv_sec++;
+		}
+		if ((time_state == TIME_OOP) &&
+					(ts->tv_sec == ntp_next_leap_sec)) {
+			result = TIME_WAIT;
+		}
+	}
+
+	return result;
+}
+
+#ifdef	CONFIG_NTP_PPS
+
+/* actually struct pps_normtime is good old struct timespec, but it is
+ * semantically different (and it is the reason why it was invented):
+ * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
+ * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
+struct pps_normtime {
+	s64		sec;	/* seconds */
+	long		nsec;	/* nanoseconds */
+};
+
+/* normalize the timestamp so that nsec is in the
+   ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
+static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
+{
+	struct pps_normtime norm = {
+		.sec = ts.tv_sec,
+		.nsec = ts.tv_nsec
+	};
+
+	if (norm.nsec > (NSEC_PER_SEC >> 1)) {
+		norm.nsec -= NSEC_PER_SEC;
+		norm.sec++;
+	}
+
+	return norm;
+}
+
+/* get current phase correction and jitter */
+static inline long pps_phase_filter_get(long *jitter)
+{
+	*jitter = pps_tf[0] - pps_tf[1];
+	if (*jitter < 0)
+		*jitter = -*jitter;
+
+	/* TODO: test various filters */
+	return pps_tf[0];
+}
+
+/* add the sample to the phase filter */
+static inline void pps_phase_filter_add(long err)
+{
+	pps_tf[2] = pps_tf[1];
+	pps_tf[1] = pps_tf[0];
+	pps_tf[0] = err;
+}
+
+/* decrease frequency calibration interval length.
+ * It is halved after four consecutive unstable intervals.
+ */
+static inline void pps_dec_freq_interval(void)
+{
+	if (--pps_intcnt <= -PPS_INTCOUNT) {
+		pps_intcnt = -PPS_INTCOUNT;
+		if (pps_shift > PPS_INTMIN) {
+			pps_shift--;
+			pps_intcnt = 0;
+		}
+	}
+}
+
+/* increase frequency calibration interval length.
+ * It is doubled after four consecutive stable intervals.
+ */
+static inline void pps_inc_freq_interval(void)
+{
+	if (++pps_intcnt >= PPS_INTCOUNT) {
+		pps_intcnt = PPS_INTCOUNT;
+		if (pps_shift < PPS_INTMAX) {
+			pps_shift++;
+			pps_intcnt = 0;
+		}
+	}
+}
+
+/* update clock frequency based on MONOTONIC_RAW clock PPS signal
+ * timestamps
+ *
+ * At the end of the calibration interval the difference between the
+ * first and last MONOTONIC_RAW clock timestamps divided by the length
+ * of the interval becomes the frequency update. If the interval was
+ * too long, the data are discarded.
+ * Returns the difference between old and new frequency values.
+ */
+static long hardpps_update_freq(struct pps_normtime freq_norm)
+{
+	long delta, delta_mod;
+	s64 ftemp;
+
+	/* check if the frequency interval was too long */
+	if (freq_norm.sec > (2 << pps_shift)) {
+		time_status |= STA_PPSERROR;
+		pps_errcnt++;
+		pps_dec_freq_interval();
+		printk_deferred(KERN_ERR
+			"hardpps: PPSERROR: interval too long - %lld s\n",
+			freq_norm.sec);
+		return 0;
+	}
+
+	/* here the raw frequency offset and wander (stability) is
+	 * calculated. If the wander is less than the wander threshold
+	 * the interval is increased; otherwise it is decreased.
+	 */
+	ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
+			freq_norm.sec);
+	delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
+	pps_freq = ftemp;
+	if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
+		printk_deferred(KERN_WARNING
+				"hardpps: PPSWANDER: change=%ld\n", delta);
+		time_status |= STA_PPSWANDER;
+		pps_stbcnt++;
+		pps_dec_freq_interval();
+	} else {	/* good sample */
+		pps_inc_freq_interval();
+	}
+
+	/* the stability metric is calculated as the average of recent
+	 * frequency changes, but is used only for performance
+	 * monitoring
+	 */
+	delta_mod = delta;
+	if (delta_mod < 0)
+		delta_mod = -delta_mod;
+	pps_stabil += (div_s64(((s64)delta_mod) <<
+				(NTP_SCALE_SHIFT - SHIFT_USEC),
+				NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
+
+	/* if enabled, the system clock frequency is updated */
+	if ((time_status & STA_PPSFREQ) != 0 &&
+	    (time_status & STA_FREQHOLD) == 0) {
+		time_freq = pps_freq;
+		ntp_update_frequency();
+	}
+
+	return delta;
+}
+
+/* correct REALTIME clock phase error against PPS signal */
+static void hardpps_update_phase(long error)
+{
+	long correction = -error;
+	long jitter;
+
+	/* add the sample to the median filter */
+	pps_phase_filter_add(correction);
+	correction = pps_phase_filter_get(&jitter);
+
+	/* Nominal jitter is due to PPS signal noise. If it exceeds the
+	 * threshold, the sample is discarded; otherwise, if so enabled,
+	 * the time offset is updated.
+	 */
+	if (jitter > (pps_jitter << PPS_POPCORN)) {
+		printk_deferred(KERN_WARNING
+				"hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
+				jitter, (pps_jitter << PPS_POPCORN));
+		time_status |= STA_PPSJITTER;
+		pps_jitcnt++;
+	} else if (time_status & STA_PPSTIME) {
+		/* correct the time using the phase offset */
+		time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
+				NTP_INTERVAL_FREQ);
+		/* cancel running adjtime() */
+		time_adjust = 0;
+	}
+	/* update jitter */
+	pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
+}
+
+/*
+ * __hardpps() - discipline CPU clock oscillator to external PPS signal
+ *
+ * This routine is called at each PPS signal arrival in order to
+ * discipline the CPU clock oscillator to the PPS signal. It takes two
+ * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
+ * is used to correct clock phase error and the latter is used to
+ * correct the frequency.
+ *
+ * This code is based on David Mills's reference nanokernel
+ * implementation. It was mostly rewritten but keeps the same idea.
+ */
+void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
+{
+	struct pps_normtime pts_norm, freq_norm;
+
+	pts_norm = pps_normalize_ts(*phase_ts);
+
+	/* clear the error bits, they will be set again if needed */
+	time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
+
+	/* indicate signal presence */
+	time_status |= STA_PPSSIGNAL;
+	pps_valid = PPS_VALID;
+
+	/* when called for the first time,
+	 * just start the frequency interval */
+	if (unlikely(pps_fbase.tv_sec == 0)) {
+		pps_fbase = *raw_ts;
+		return;
+	}
+
+	/* ok, now we have a base for frequency calculation */
+	freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
+
+	/* check that the signal is in the range
+	 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
+	if ((freq_norm.sec == 0) ||
+			(freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
+			(freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
+		time_status |= STA_PPSJITTER;
+		/* restart the frequency calibration interval */
+		pps_fbase = *raw_ts;
+		printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
+		return;
+	}
+
+	/* signal is ok */
+
+	/* check if the current frequency interval is finished */
+	if (freq_norm.sec >= (1 << pps_shift)) {
+		pps_calcnt++;
+		/* restart the frequency calibration interval */
+		pps_fbase = *raw_ts;
+		hardpps_update_freq(freq_norm);
+	}
+
+	hardpps_update_phase(pts_norm.nsec);
+
+}
+#endif	/* CONFIG_NTP_PPS */
+
+static int __init ntp_tick_adj_setup(char *str)
+{
+	int rc = kstrtos64(str, 0, &ntp_tick_adj);
+	if (rc)
+		return rc;
+
+	ntp_tick_adj <<= NTP_SCALE_SHIFT;
+	return 1;
+}
+
+__setup("ntp_tick_adj=", ntp_tick_adj_setup);
+
+void __init ntp_init(void)
+{
+	ntp_clear();
+	ntp_init_cmos_sync();
+}
diff --git a/kernel/time/ntp_internal.h b/kernel/time/ntp_internal.h
new file mode 100644
index 0000000000..23d1b74c30
--- /dev/null
+++ b/kernel/time/ntp_internal.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NTP_INTERNAL_H
+#define _LINUX_NTP_INTERNAL_H
+
+extern void ntp_init(void);
+extern void ntp_clear(void);
+/* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
+extern u64 ntp_tick_length(void);
+extern ktime_t ntp_get_next_leap(void);
+extern int second_overflow(time64_t secs);
+extern int __do_adjtimex(struct __kernel_timex *txc,
+			 const struct timespec64 *ts,
+			 s32 *time_tai, struct audit_ntp_data *ad);
+extern void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts);
+
+#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
+extern void ntp_notify_cmos_timer(void);
+#else
+static inline void ntp_notify_cmos_timer(void) { }
+#endif
+
+#endif /* _LINUX_NTP_INTERNAL_H */
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
new file mode 100644
index 0000000000..77c0c2370b
--- /dev/null
+++ b/kernel/time/posix-clock.c
@@ -0,0 +1,317 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Support for dynamic clock devices
+ *
+ * Copyright (C) 2010 OMICRON electronics GmbH
+ */
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/file.h>
+#include <linux/posix-clock.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+
+#include "posix-timers.h"
+
+/*
+ * Returns NULL if the posix_clock instance attached to 'fp' is old and stale.
+ */
+static struct posix_clock *get_posix_clock(struct file *fp)
+{
+	struct posix_clock *clk = fp->private_data;
+
+	down_read(&clk->rwsem);
+
+	if (!clk->zombie)
+		return clk;
+
+	up_read(&clk->rwsem);
+
+	return NULL;
+}
+
+static void put_posix_clock(struct posix_clock *clk)
+{
+	up_read(&clk->rwsem);
+}
+
+static ssize_t posix_clock_read(struct file *fp, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct posix_clock *clk = get_posix_clock(fp);
+	int err = -EINVAL;
+
+	if (!clk)
+		return -ENODEV;
+
+	if (clk->ops.read)
+		err = clk->ops.read(clk, fp->f_flags, buf, count);
+
+	put_posix_clock(clk);
+
+	return err;
+}
+
+static __poll_t posix_clock_poll(struct file *fp, poll_table *wait)
+{
+	struct posix_clock *clk = get_posix_clock(fp);
+	__poll_t result = 0;
+
+	if (!clk)
+		return EPOLLERR;
+
+	if (clk->ops.poll)
+		result = clk->ops.poll(clk, fp, wait);
+
+	put_posix_clock(clk);
+
+	return result;
+}
+
+static long posix_clock_ioctl(struct file *fp,
+			      unsigned int cmd, unsigned long arg)
+{
+	struct posix_clock *clk = get_posix_clock(fp);
+	int err = -ENOTTY;
+
+	if (!clk)
+		return -ENODEV;
+
+	if (clk->ops.ioctl)
+		err = clk->ops.ioctl(clk, cmd, arg);
+
+	put_posix_clock(clk);
+
+	return err;
+}
+
+#ifdef CONFIG_COMPAT
+static long posix_clock_compat_ioctl(struct file *fp,
+				     unsigned int cmd, unsigned long arg)
+{
+	struct posix_clock *clk = get_posix_clock(fp);
+	int err = -ENOTTY;
+
+	if (!clk)
+		return -ENODEV;
+
+	if (clk->ops.ioctl)
+		err = clk->ops.ioctl(clk, cmd, arg);
+
+	put_posix_clock(clk);
+
+	return err;
+}
+#endif
+
+static int posix_clock_open(struct inode *inode, struct file *fp)
+{
+	int err;
+	struct posix_clock *clk =
+		container_of(inode->i_cdev, struct posix_clock, cdev);
+
+	down_read(&clk->rwsem);
+
+	if (clk->zombie) {
+		err = -ENODEV;
+		goto out;
+	}
+	if (clk->ops.open)
+		err = clk->ops.open(clk, fp->f_mode);
+	else
+		err = 0;
+
+	if (!err) {
+		get_device(clk->dev);
+		fp->private_data = clk;
+	}
+out:
+	up_read(&clk->rwsem);
+	return err;
+}
+
+static int posix_clock_release(struct inode *inode, struct file *fp)
+{
+	struct posix_clock *clk = fp->private_data;
+	int err = 0;
+
+	if (clk->ops.release)
+		err = clk->ops.release(clk);
+
+	put_device(clk->dev);
+
+	fp->private_data = NULL;
+
+	return err;
+}
+
+static const struct file_operations posix_clock_file_operations = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.read		= posix_clock_read,
+	.poll		= posix_clock_poll,
+	.unlocked_ioctl	= posix_clock_ioctl,
+	.open		= posix_clock_open,
+	.release	= posix_clock_release,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= posix_clock_compat_ioctl,
+#endif
+};
+
+int posix_clock_register(struct posix_clock *clk, struct device *dev)
+{
+	int err;
+
+	init_rwsem(&clk->rwsem);
+
+	cdev_init(&clk->cdev, &posix_clock_file_operations);
+	err = cdev_device_add(&clk->cdev, dev);
+	if (err) {
+		pr_err("%s unable to add device %d:%d\n",
+			dev_name(dev), MAJOR(dev->devt), MINOR(dev->devt));
+		return err;
+	}
+	clk->cdev.owner = clk->ops.owner;
+	clk->dev = dev;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(posix_clock_register);
+
+void posix_clock_unregister(struct posix_clock *clk)
+{
+	cdev_device_del(&clk->cdev, clk->dev);
+
+	down_write(&clk->rwsem);
+	clk->zombie = true;
+	up_write(&clk->rwsem);
+
+	put_device(clk->dev);
+}
+EXPORT_SYMBOL_GPL(posix_clock_unregister);
+
+struct posix_clock_desc {
+	struct file *fp;
+	struct posix_clock *clk;
+};
+
+static int get_clock_desc(const clockid_t id, struct posix_clock_desc *cd)
+{
+	struct file *fp = fget(clockid_to_fd(id));
+	int err = -EINVAL;
+
+	if (!fp)
+		return err;
+
+	if (fp->f_op->open != posix_clock_open || !fp->private_data)
+		goto out;
+
+	cd->fp = fp;
+	cd->clk = get_posix_clock(fp);
+
+	err = cd->clk ? 0 : -ENODEV;
+out:
+	if (err)
+		fput(fp);
+	return err;
+}
+
+static void put_clock_desc(struct posix_clock_desc *cd)
+{
+	put_posix_clock(cd->clk);
+	fput(cd->fp);
+}
+
+static int pc_clock_adjtime(clockid_t id, struct __kernel_timex *tx)
+{
+	struct posix_clock_desc cd;
+	int err;
+
+	err = get_clock_desc(id, &cd);
+	if (err)
+		return err;
+
+	if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
+		err = -EACCES;
+		goto out;
+	}
+
+	if (cd.clk->ops.clock_adjtime)
+		err = cd.clk->ops.clock_adjtime(cd.clk, tx);
+	else
+		err = -EOPNOTSUPP;
+out:
+	put_clock_desc(&cd);
+
+	return err;
+}
+
+static int pc_clock_gettime(clockid_t id, struct timespec64 *ts)
+{
+	struct posix_clock_desc cd;
+	int err;
+
+	err = get_clock_desc(id, &cd);
+	if (err)
+		return err;
+
+	if (cd.clk->ops.clock_gettime)
+		err = cd.clk->ops.clock_gettime(cd.clk, ts);
+	else
+		err = -EOPNOTSUPP;
+
+	put_clock_desc(&cd);
+
+	return err;
+}
+
+static int pc_clock_getres(clockid_t id, struct timespec64 *ts)
+{
+	struct posix_clock_desc cd;
+	int err;
+
+	err = get_clock_desc(id, &cd);
+	if (err)
+		return err;
+
+	if (cd.clk->ops.clock_getres)
+		err = cd.clk->ops.clock_getres(cd.clk, ts);
+	else
+		err = -EOPNOTSUPP;
+
+	put_clock_desc(&cd);
+
+	return err;
+}
+
+static int pc_clock_settime(clockid_t id, const struct timespec64 *ts)
+{
+	struct posix_clock_desc cd;
+	int err;
+
+	err = get_clock_desc(id, &cd);
+	if (err)
+		return err;
+
+	if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
+		err = -EACCES;
+		goto out;
+	}
+
+	if (cd.clk->ops.clock_settime)
+		err = cd.clk->ops.clock_settime(cd.clk, ts);
+	else
+		err = -EOPNOTSUPP;
+out:
+	put_clock_desc(&cd);
+
+	return err;
+}
+
+const struct k_clock clock_posix_dynamic = {
+	.clock_getres		= pc_clock_getres,
+	.clock_set		= pc_clock_settime,
+	.clock_get_timespec	= pc_clock_gettime,
+	.clock_adj		= pc_clock_adjtime,
+};
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
new file mode 100644
index 0000000000..e9c6f9d0e4
--- /dev/null
+++ b/kernel/time/posix-cpu-timers.c
@@ -0,0 +1,1692 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implement CPU time clocks for the POSIX clock interface.
+ */
+
+#include <linux/sched/signal.h>
+#include <linux/sched/cputime.h>
+#include <linux/posix-timers.h>
+#include <linux/errno.h>
+#include <linux/math64.h>
+#include <linux/uaccess.h>
+#include <linux/kernel_stat.h>
+#include <trace/events/timer.h>
+#include <linux/tick.h>
+#include <linux/workqueue.h>
+#include <linux/compat.h>
+#include <linux/sched/deadline.h>
+#include <linux/task_work.h>
+
+#include "posix-timers.h"
+
+static void posix_cpu_timer_rearm(struct k_itimer *timer);
+
+void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
+{
+	posix_cputimers_init(pct);
+	if (cpu_limit != RLIM_INFINITY) {
+		pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
+		pct->timers_active = true;
+	}
+}
+
+/*
+ * Called after updating RLIMIT_CPU to run cpu timer and update
+ * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
+ * necessary. Needs siglock protection since other code may update the
+ * expiration cache as well.
+ *
+ * Returns 0 on success, -ESRCH on failure.  Can fail if the task is exiting and
+ * we cannot lock_task_sighand.  Cannot fail if task is current.
+ */
+int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
+{
+	u64 nsecs = rlim_new * NSEC_PER_SEC;
+	unsigned long irq_fl;
+
+	if (!lock_task_sighand(task, &irq_fl))
+		return -ESRCH;
+	set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
+	unlock_task_sighand(task, &irq_fl);
+	return 0;
+}
+
+/*
+ * Functions for validating access to tasks.
+ */
+static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
+{
+	const bool thread = !!CPUCLOCK_PERTHREAD(clock);
+	const pid_t upid = CPUCLOCK_PID(clock);
+	struct pid *pid;
+
+	if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
+		return NULL;
+
+	/*
+	 * If the encoded PID is 0, then the timer is targeted at current
+	 * or the process to which current belongs.
+	 */
+	if (upid == 0)
+		return thread ? task_pid(current) : task_tgid(current);
+
+	pid = find_vpid(upid);
+	if (!pid)
+		return NULL;
+
+	if (thread) {
+		struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
+		return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
+	}
+
+	/*
+	 * For clock_gettime(PROCESS) allow finding the process by
+	 * with the pid of the current task.  The code needs the tgid
+	 * of the process so that pid_task(pid, PIDTYPE_TGID) can be
+	 * used to find the process.
+	 */
+	if (gettime && (pid == task_pid(current)))
+		return task_tgid(current);
+
+	/*
+	 * For processes require that pid identifies a process.
+	 */
+	return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
+}
+
+static inline int validate_clock_permissions(const clockid_t clock)
+{
+	int ret;
+
+	rcu_read_lock();
+	ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static inline enum pid_type clock_pid_type(const clockid_t clock)
+{
+	return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
+}
+
+static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
+{
+	return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
+}
+
+/*
+ * Update expiry time from increment, and increase overrun count,
+ * given the current clock sample.
+ */
+static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
+{
+	u64 delta, incr, expires = timer->it.cpu.node.expires;
+	int i;
+
+	if (!timer->it_interval)
+		return expires;
+
+	if (now < expires)
+		return expires;
+
+	incr = timer->it_interval;
+	delta = now + incr - expires;
+
+	/* Don't use (incr*2 < delta), incr*2 might overflow. */
+	for (i = 0; incr < delta - incr; i++)
+		incr = incr << 1;
+
+	for (; i >= 0; incr >>= 1, i--) {
+		if (delta < incr)
+			continue;
+
+		timer->it.cpu.node.expires += incr;
+		timer->it_overrun += 1LL << i;
+		delta -= incr;
+	}
+	return timer->it.cpu.node.expires;
+}
+
+/* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
+static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
+{
+	return !(~pct->bases[CPUCLOCK_PROF].nextevt |
+		 ~pct->bases[CPUCLOCK_VIRT].nextevt |
+		 ~pct->bases[CPUCLOCK_SCHED].nextevt);
+}
+
+static int
+posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
+{
+	int error = validate_clock_permissions(which_clock);
+
+	if (!error) {
+		tp->tv_sec = 0;
+		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
+		if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
+			/*
+			 * If sched_clock is using a cycle counter, we
+			 * don't have any idea of its true resolution
+			 * exported, but it is much more than 1s/HZ.
+			 */
+			tp->tv_nsec = 1;
+		}
+	}
+	return error;
+}
+
+static int
+posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
+{
+	int error = validate_clock_permissions(clock);
+
+	/*
+	 * You can never reset a CPU clock, but we check for other errors
+	 * in the call before failing with EPERM.
+	 */
+	return error ? : -EPERM;
+}
+
+/*
+ * Sample a per-thread clock for the given task. clkid is validated.
+ */
+static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
+{
+	u64 utime, stime;
+
+	if (clkid == CPUCLOCK_SCHED)
+		return task_sched_runtime(p);
+
+	task_cputime(p, &utime, &stime);
+
+	switch (clkid) {
+	case CPUCLOCK_PROF:
+		return utime + stime;
+	case CPUCLOCK_VIRT:
+		return utime;
+	default:
+		WARN_ON_ONCE(1);
+	}
+	return 0;
+}
+
+static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
+{
+	samples[CPUCLOCK_PROF] = stime + utime;
+	samples[CPUCLOCK_VIRT] = utime;
+	samples[CPUCLOCK_SCHED] = rtime;
+}
+
+static void task_sample_cputime(struct task_struct *p, u64 *samples)
+{
+	u64 stime, utime;
+
+	task_cputime(p, &utime, &stime);
+	store_samples(samples, stime, utime, p->se.sum_exec_runtime);
+}
+
+static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
+				       u64 *samples)
+{
+	u64 stime, utime, rtime;
+
+	utime = atomic64_read(&at->utime);
+	stime = atomic64_read(&at->stime);
+	rtime = atomic64_read(&at->sum_exec_runtime);
+	store_samples(samples, stime, utime, rtime);
+}
+
+/*
+ * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
+ * to avoid race conditions with concurrent updates to cputime.
+ */
+static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
+{
+	u64 curr_cputime = atomic64_read(cputime);
+
+	do {
+		if (sum_cputime <= curr_cputime)
+			return;
+	} while (!atomic64_try_cmpxchg(cputime, &curr_cputime, sum_cputime));
+}
+
+static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
+			      struct task_cputime *sum)
+{
+	__update_gt_cputime(&cputime_atomic->utime, sum->utime);
+	__update_gt_cputime(&cputime_atomic->stime, sum->stime);
+	__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
+}
+
+/**
+ * thread_group_sample_cputime - Sample cputime for a given task
+ * @tsk:	Task for which cputime needs to be started
+ * @samples:	Storage for time samples
+ *
+ * Called from sys_getitimer() to calculate the expiry time of an active
+ * timer. That means group cputime accounting is already active. Called
+ * with task sighand lock held.
+ *
+ * Updates @times with an uptodate sample of the thread group cputimes.
+ */
+void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
+{
+	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
+
+	WARN_ON_ONCE(!pct->timers_active);
+
+	proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
+}
+
+/**
+ * thread_group_start_cputime - Start cputime and return a sample
+ * @tsk:	Task for which cputime needs to be started
+ * @samples:	Storage for time samples
+ *
+ * The thread group cputime accounting is avoided when there are no posix
+ * CPU timers armed. Before starting a timer it's required to check whether
+ * the time accounting is active. If not, a full update of the atomic
+ * accounting store needs to be done and the accounting enabled.
+ *
+ * Updates @times with an uptodate sample of the thread group cputimes.
+ */
+static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
+{
+	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
+
+	lockdep_assert_task_sighand_held(tsk);
+
+	/* Check if cputimer isn't running. This is accessed without locking. */
+	if (!READ_ONCE(pct->timers_active)) {
+		struct task_cputime sum;
+
+		/*
+		 * The POSIX timer interface allows for absolute time expiry
+		 * values through the TIMER_ABSTIME flag, therefore we have
+		 * to synchronize the timer to the clock every time we start it.
+		 */
+		thread_group_cputime(tsk, &sum);
+		update_gt_cputime(&cputimer->cputime_atomic, &sum);
+
+		/*
+		 * We're setting timers_active without a lock. Ensure this
+		 * only gets written to in one operation. We set it after
+		 * update_gt_cputime() as a small optimization, but
+		 * barriers are not required because update_gt_cputime()
+		 * can handle concurrent updates.
+		 */
+		WRITE_ONCE(pct->timers_active, true);
+	}
+	proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
+}
+
+static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
+{
+	struct task_cputime ct;
+
+	thread_group_cputime(tsk, &ct);
+	store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
+}
+
+/*
+ * Sample a process (thread group) clock for the given task clkid. If the
+ * group's cputime accounting is already enabled, read the atomic
+ * store. Otherwise a full update is required.  clkid is already validated.
+ */
+static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
+				  bool start)
+{
+	struct thread_group_cputimer *cputimer = &p->signal->cputimer;
+	struct posix_cputimers *pct = &p->signal->posix_cputimers;
+	u64 samples[CPUCLOCK_MAX];
+
+	if (!READ_ONCE(pct->timers_active)) {
+		if (start)
+			thread_group_start_cputime(p, samples);
+		else
+			__thread_group_cputime(p, samples);
+	} else {
+		proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
+	}
+
+	return samples[clkid];
+}
+
+static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
+{
+	const clockid_t clkid = CPUCLOCK_WHICH(clock);
+	struct task_struct *tsk;
+	u64 t;
+
+	rcu_read_lock();
+	tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
+	if (!tsk) {
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	if (CPUCLOCK_PERTHREAD(clock))
+		t = cpu_clock_sample(clkid, tsk);
+	else
+		t = cpu_clock_sample_group(clkid, tsk, false);
+	rcu_read_unlock();
+
+	*tp = ns_to_timespec64(t);
+	return 0;
+}
+
+/*
+ * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
+ * This is called from sys_timer_create() and do_cpu_nanosleep() with the
+ * new timer already all-zeros initialized.
+ */
+static int posix_cpu_timer_create(struct k_itimer *new_timer)
+{
+	static struct lock_class_key posix_cpu_timers_key;
+	struct pid *pid;
+
+	rcu_read_lock();
+	pid = pid_for_clock(new_timer->it_clock, false);
+	if (!pid) {
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	/*
+	 * If posix timer expiry is handled in task work context then
+	 * timer::it_lock can be taken without disabling interrupts as all
+	 * other locking happens in task context. This requires a separate
+	 * lock class key otherwise regular posix timer expiry would record
+	 * the lock class being taken in interrupt context and generate a
+	 * false positive warning.
+	 */
+	if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
+		lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
+
+	new_timer->kclock = &clock_posix_cpu;
+	timerqueue_init(&new_timer->it.cpu.node);
+	new_timer->it.cpu.pid = get_pid(pid);
+	rcu_read_unlock();
+	return 0;
+}
+
+static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
+					      struct task_struct *tsk)
+{
+	int clkidx = CPUCLOCK_WHICH(timer->it_clock);
+
+	if (CPUCLOCK_PERTHREAD(timer->it_clock))
+		return tsk->posix_cputimers.bases + clkidx;
+	else
+		return tsk->signal->posix_cputimers.bases + clkidx;
+}
+
+/*
+ * Force recalculating the base earliest expiration on the next tick.
+ * This will also re-evaluate the need to keep around the process wide
+ * cputime counter and tick dependency and eventually shut these down
+ * if necessary.
+ */
+static void trigger_base_recalc_expires(struct k_itimer *timer,
+					struct task_struct *tsk)
+{
+	struct posix_cputimer_base *base = timer_base(timer, tsk);
+
+	base->nextevt = 0;
+}
+
+/*
+ * Dequeue the timer and reset the base if it was its earliest expiration.
+ * It makes sure the next tick recalculates the base next expiration so we
+ * don't keep the costly process wide cputime counter around for a random
+ * amount of time, along with the tick dependency.
+ *
+ * If another timer gets queued between this and the next tick, its
+ * expiration will update the base next event if necessary on the next
+ * tick.
+ */
+static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
+{
+	struct cpu_timer *ctmr = &timer->it.cpu;
+	struct posix_cputimer_base *base;
+
+	if (!cpu_timer_dequeue(ctmr))
+		return;
+
+	base = timer_base(timer, p);
+	if (cpu_timer_getexpires(ctmr) == base->nextevt)
+		trigger_base_recalc_expires(timer, p);
+}
+
+
+/*
+ * Clean up a CPU-clock timer that is about to be destroyed.
+ * This is called from timer deletion with the timer already locked.
+ * If we return TIMER_RETRY, it's necessary to release the timer's lock
+ * and try again.  (This happens when the timer is in the middle of firing.)
+ */
+static int posix_cpu_timer_del(struct k_itimer *timer)
+{
+	struct cpu_timer *ctmr = &timer->it.cpu;
+	struct sighand_struct *sighand;
+	struct task_struct *p;
+	unsigned long flags;
+	int ret = 0;
+
+	rcu_read_lock();
+	p = cpu_timer_task_rcu(timer);
+	if (!p)
+		goto out;
+
+	/*
+	 * Protect against sighand release/switch in exit/exec and process/
+	 * thread timer list entry concurrent read/writes.
+	 */
+	sighand = lock_task_sighand(p, &flags);
+	if (unlikely(sighand == NULL)) {
+		/*
+		 * This raced with the reaping of the task. The exit cleanup
+		 * should have removed this timer from the timer queue.
+		 */
+		WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
+	} else {
+		if (timer->it.cpu.firing)
+			ret = TIMER_RETRY;
+		else
+			disarm_timer(timer, p);
+
+		unlock_task_sighand(p, &flags);
+	}
+
+out:
+	rcu_read_unlock();
+	if (!ret)
+		put_pid(ctmr->pid);
+
+	return ret;
+}
+
+static void cleanup_timerqueue(struct timerqueue_head *head)
+{
+	struct timerqueue_node *node;
+	struct cpu_timer *ctmr;
+
+	while ((node = timerqueue_getnext(head))) {
+		timerqueue_del(head, node);
+		ctmr = container_of(node, struct cpu_timer, node);
+		ctmr->head = NULL;
+	}
+}
+
+/*
+ * Clean out CPU timers which are still armed when a thread exits. The
+ * timers are only removed from the list. No other updates are done. The
+ * corresponding posix timers are still accessible, but cannot be rearmed.
+ *
+ * This must be called with the siglock held.
+ */
+static void cleanup_timers(struct posix_cputimers *pct)
+{
+	cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
+	cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
+	cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
+}
+
+/*
+ * These are both called with the siglock held, when the current thread
+ * is being reaped.  When the final (leader) thread in the group is reaped,
+ * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
+ */
+void posix_cpu_timers_exit(struct task_struct *tsk)
+{
+	cleanup_timers(&tsk->posix_cputimers);
+}
+void posix_cpu_timers_exit_group(struct task_struct *tsk)
+{
+	cleanup_timers(&tsk->signal->posix_cputimers);
+}
+
+/*
+ * Insert the timer on the appropriate list before any timers that
+ * expire later.  This must be called with the sighand lock held.
+ */
+static void arm_timer(struct k_itimer *timer, struct task_struct *p)
+{
+	struct posix_cputimer_base *base = timer_base(timer, p);
+	struct cpu_timer *ctmr = &timer->it.cpu;
+	u64 newexp = cpu_timer_getexpires(ctmr);
+
+	if (!cpu_timer_enqueue(&base->tqhead, ctmr))
+		return;
+
+	/*
+	 * We are the new earliest-expiring POSIX 1.b timer, hence
+	 * need to update expiration cache. Take into account that
+	 * for process timers we share expiration cache with itimers
+	 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
+	 */
+	if (newexp < base->nextevt)
+		base->nextevt = newexp;
+
+	if (CPUCLOCK_PERTHREAD(timer->it_clock))
+		tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
+	else
+		tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
+}
+
+/*
+ * The timer is locked, fire it and arrange for its reload.
+ */
+static void cpu_timer_fire(struct k_itimer *timer)
+{
+	struct cpu_timer *ctmr = &timer->it.cpu;
+
+	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
+		/*
+		 * User don't want any signal.
+		 */
+		cpu_timer_setexpires(ctmr, 0);
+	} else if (unlikely(timer->sigq == NULL)) {
+		/*
+		 * This a special case for clock_nanosleep,
+		 * not a normal timer from sys_timer_create.
+		 */
+		wake_up_process(timer->it_process);
+		cpu_timer_setexpires(ctmr, 0);
+	} else if (!timer->it_interval) {
+		/*
+		 * One-shot timer.  Clear it as soon as it's fired.
+		 */
+		posix_timer_event(timer, 0);
+		cpu_timer_setexpires(ctmr, 0);
+	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
+		/*
+		 * The signal did not get queued because the signal
+		 * was ignored, so we won't get any callback to
+		 * reload the timer.  But we need to keep it
+		 * ticking in case the signal is deliverable next time.
+		 */
+		posix_cpu_timer_rearm(timer);
+		++timer->it_requeue_pending;
+	}
+}
+
+/*
+ * Guts of sys_timer_settime for CPU timers.
+ * This is called with the timer locked and interrupts disabled.
+ * If we return TIMER_RETRY, it's necessary to release the timer's lock
+ * and try again.  (This happens when the timer is in the middle of firing.)
+ */
+static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
+			       struct itimerspec64 *new, struct itimerspec64 *old)
+{
+	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
+	u64 old_expires, new_expires, old_incr, val;
+	struct cpu_timer *ctmr = &timer->it.cpu;
+	struct sighand_struct *sighand;
+	struct task_struct *p;
+	unsigned long flags;
+	int ret = 0;
+
+	rcu_read_lock();
+	p = cpu_timer_task_rcu(timer);
+	if (!p) {
+		/*
+		 * If p has just been reaped, we can no
+		 * longer get any information about it at all.
+		 */
+		rcu_read_unlock();
+		return -ESRCH;
+	}
+
+	/*
+	 * Use the to_ktime conversion because that clamps the maximum
+	 * value to KTIME_MAX and avoid multiplication overflows.
+	 */
+	new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
+
+	/*
+	 * Protect against sighand release/switch in exit/exec and p->cpu_timers
+	 * and p->signal->cpu_timers read/write in arm_timer()
+	 */
+	sighand = lock_task_sighand(p, &flags);
+	/*
+	 * If p has just been reaped, we can no
+	 * longer get any information about it at all.
+	 */
+	if (unlikely(sighand == NULL)) {
+		rcu_read_unlock();
+		return -ESRCH;
+	}
+
+	/*
+	 * Disarm any old timer after extracting its expiry time.
+	 */
+	old_incr = timer->it_interval;
+	old_expires = cpu_timer_getexpires(ctmr);
+
+	if (unlikely(timer->it.cpu.firing)) {
+		timer->it.cpu.firing = -1;
+		ret = TIMER_RETRY;
+	} else {
+		cpu_timer_dequeue(ctmr);
+	}
+
+	/*
+	 * We need to sample the current value to convert the new
+	 * value from to relative and absolute, and to convert the
+	 * old value from absolute to relative.  To set a process
+	 * timer, we need a sample to balance the thread expiry
+	 * times (in arm_timer).  With an absolute time, we must
+	 * check if it's already passed.  In short, we need a sample.
+	 */
+	if (CPUCLOCK_PERTHREAD(timer->it_clock))
+		val = cpu_clock_sample(clkid, p);
+	else
+		val = cpu_clock_sample_group(clkid, p, true);
+
+	if (old) {
+		if (old_expires == 0) {
+			old->it_value.tv_sec = 0;
+			old->it_value.tv_nsec = 0;
+		} else {
+			/*
+			 * Update the timer in case it has overrun already.
+			 * If it has, we'll report it as having overrun and
+			 * with the next reloaded timer already ticking,
+			 * though we are swallowing that pending
+			 * notification here to install the new setting.
+			 */
+			u64 exp = bump_cpu_timer(timer, val);
+
+			if (val < exp) {
+				old_expires = exp - val;
+				old->it_value = ns_to_timespec64(old_expires);
+			} else {
+				old->it_value.tv_nsec = 1;
+				old->it_value.tv_sec = 0;
+			}
+		}
+	}
+
+	if (unlikely(ret)) {
+		/*
+		 * We are colliding with the timer actually firing.
+		 * Punt after filling in the timer's old value, and
+		 * disable this firing since we are already reporting
+		 * it as an overrun (thanks to bump_cpu_timer above).
+		 */
+		unlock_task_sighand(p, &flags);
+		goto out;
+	}
+
+	if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
+		new_expires += val;
+	}
+
+	/*
+	 * Install the new expiry time (or zero).
+	 * For a timer with no notification action, we don't actually
+	 * arm the timer (we'll just fake it for timer_gettime).
+	 */
+	cpu_timer_setexpires(ctmr, new_expires);
+	if (new_expires != 0 && val < new_expires) {
+		arm_timer(timer, p);
+	}
+
+	unlock_task_sighand(p, &flags);
+	/*
+	 * Install the new reload setting, and
+	 * set up the signal and overrun bookkeeping.
+	 */
+	timer->it_interval = timespec64_to_ktime(new->it_interval);
+
+	/*
+	 * This acts as a modification timestamp for the timer,
+	 * so any automatic reload attempt will punt on seeing
+	 * that we have reset the timer manually.
+	 */
+	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
+		~REQUEUE_PENDING;
+	timer->it_overrun_last = 0;
+	timer->it_overrun = -1;
+
+	if (val >= new_expires) {
+		if (new_expires != 0) {
+			/*
+			 * The designated time already passed, so we notify
+			 * immediately, even if the thread never runs to
+			 * accumulate more time on this clock.
+			 */
+			cpu_timer_fire(timer);
+		}
+
+		/*
+		 * Make sure we don't keep around the process wide cputime
+		 * counter or the tick dependency if they are not necessary.
+		 */
+		sighand = lock_task_sighand(p, &flags);
+		if (!sighand)
+			goto out;
+
+		if (!cpu_timer_queued(ctmr))
+			trigger_base_recalc_expires(timer, p);
+
+		unlock_task_sighand(p, &flags);
+	}
+ out:
+	rcu_read_unlock();
+	if (old)
+		old->it_interval = ns_to_timespec64(old_incr);
+
+	return ret;
+}
+
+static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
+{
+	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
+	struct cpu_timer *ctmr = &timer->it.cpu;
+	u64 now, expires = cpu_timer_getexpires(ctmr);
+	struct task_struct *p;
+
+	rcu_read_lock();
+	p = cpu_timer_task_rcu(timer);
+	if (!p)
+		goto out;
+
+	/*
+	 * Easy part: convert the reload time.
+	 */
+	itp->it_interval = ktime_to_timespec64(timer->it_interval);
+
+	if (!expires)
+		goto out;
+
+	/*
+	 * Sample the clock to take the difference with the expiry time.
+	 */
+	if (CPUCLOCK_PERTHREAD(timer->it_clock))
+		now = cpu_clock_sample(clkid, p);
+	else
+		now = cpu_clock_sample_group(clkid, p, false);
+
+	if (now < expires) {
+		itp->it_value = ns_to_timespec64(expires - now);
+	} else {
+		/*
+		 * The timer should have expired already, but the firing
+		 * hasn't taken place yet.  Say it's just about to expire.
+		 */
+		itp->it_value.tv_nsec = 1;
+		itp->it_value.tv_sec = 0;
+	}
+out:
+	rcu_read_unlock();
+}
+
+#define MAX_COLLECTED	20
+
+static u64 collect_timerqueue(struct timerqueue_head *head,
+			      struct list_head *firing, u64 now)
+{
+	struct timerqueue_node *next;
+	int i = 0;
+
+	while ((next = timerqueue_getnext(head))) {
+		struct cpu_timer *ctmr;
+		u64 expires;
+
+		ctmr = container_of(next, struct cpu_timer, node);
+		expires = cpu_timer_getexpires(ctmr);
+		/* Limit the number of timers to expire at once */
+		if (++i == MAX_COLLECTED || now < expires)
+			return expires;
+
+		ctmr->firing = 1;
+		/* See posix_cpu_timer_wait_running() */
+		rcu_assign_pointer(ctmr->handling, current);
+		cpu_timer_dequeue(ctmr);
+		list_add_tail(&ctmr->elist, firing);
+	}
+
+	return U64_MAX;
+}
+
+static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
+				    struct list_head *firing)
+{
+	struct posix_cputimer_base *base = pct->bases;
+	int i;
+
+	for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
+		base->nextevt = collect_timerqueue(&base->tqhead, firing,
+						    samples[i]);
+	}
+}
+
+static inline void check_dl_overrun(struct task_struct *tsk)
+{
+	if (tsk->dl.dl_overrun) {
+		tsk->dl.dl_overrun = 0;
+		send_signal_locked(SIGXCPU, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
+	}
+}
+
+static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
+{
+	if (time < limit)
+		return false;
+
+	if (print_fatal_signals) {
+		pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
+			rt ? "RT" : "CPU", hard ? "hard" : "soft",
+			current->comm, task_pid_nr(current));
+	}
+	send_signal_locked(signo, SEND_SIG_PRIV, current, PIDTYPE_TGID);
+	return true;
+}
+
+/*
+ * Check for any per-thread CPU timers that have fired and move them off
+ * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
+ * tsk->it_*_expires values to reflect the remaining thread CPU timers.
+ */
+static void check_thread_timers(struct task_struct *tsk,
+				struct list_head *firing)
+{
+	struct posix_cputimers *pct = &tsk->posix_cputimers;
+	u64 samples[CPUCLOCK_MAX];
+	unsigned long soft;
+
+	if (dl_task(tsk))
+		check_dl_overrun(tsk);
+
+	if (expiry_cache_is_inactive(pct))
+		return;
+
+	task_sample_cputime(tsk, samples);
+	collect_posix_cputimers(pct, samples, firing);
+
+	/*
+	 * Check for the special case thread timers.
+	 */
+	soft = task_rlimit(tsk, RLIMIT_RTTIME);
+	if (soft != RLIM_INFINITY) {
+		/* Task RT timeout is accounted in jiffies. RTTIME is usec */
+		unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
+		unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
+
+		/* At the hard limit, send SIGKILL. No further action. */
+		if (hard != RLIM_INFINITY &&
+		    check_rlimit(rttime, hard, SIGKILL, true, true))
+			return;
+
+		/* At the soft limit, send a SIGXCPU every second */
+		if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
+			soft += USEC_PER_SEC;
+			tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
+		}
+	}
+
+	if (expiry_cache_is_inactive(pct))
+		tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
+}
+
+static inline void stop_process_timers(struct signal_struct *sig)
+{
+	struct posix_cputimers *pct = &sig->posix_cputimers;
+
+	/* Turn off the active flag. This is done without locking. */
+	WRITE_ONCE(pct->timers_active, false);
+	tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
+}
+
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+			     u64 *expires, u64 cur_time, int signo)
+{
+	if (!it->expires)
+		return;
+
+	if (cur_time >= it->expires) {
+		if (it->incr)
+			it->expires += it->incr;
+		else
+			it->expires = 0;
+
+		trace_itimer_expire(signo == SIGPROF ?
+				    ITIMER_PROF : ITIMER_VIRTUAL,
+				    task_tgid(tsk), cur_time);
+		send_signal_locked(signo, SEND_SIG_PRIV, tsk, PIDTYPE_TGID);
+	}
+
+	if (it->expires && it->expires < *expires)
+		*expires = it->expires;
+}
+
+/*
+ * Check for any per-thread CPU timers that have fired and move them
+ * off the tsk->*_timers list onto the firing list.  Per-thread timers
+ * have already been taken off.
+ */
+static void check_process_timers(struct task_struct *tsk,
+				 struct list_head *firing)
+{
+	struct signal_struct *const sig = tsk->signal;
+	struct posix_cputimers *pct = &sig->posix_cputimers;
+	u64 samples[CPUCLOCK_MAX];
+	unsigned long soft;
+
+	/*
+	 * If there are no active process wide timers (POSIX 1.b, itimers,
+	 * RLIMIT_CPU) nothing to check. Also skip the process wide timer
+	 * processing when there is already another task handling them.
+	 */
+	if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
+		return;
+
+	/*
+	 * Signify that a thread is checking for process timers.
+	 * Write access to this field is protected by the sighand lock.
+	 */
+	pct->expiry_active = true;
+
+	/*
+	 * Collect the current process totals. Group accounting is active
+	 * so the sample can be taken directly.
+	 */
+	proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
+	collect_posix_cputimers(pct, samples, firing);
+
+	/*
+	 * Check for the special case process timers.
+	 */
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
+			 &pct->bases[CPUCLOCK_PROF].nextevt,
+			 samples[CPUCLOCK_PROF], SIGPROF);
+	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
+			 &pct->bases[CPUCLOCK_VIRT].nextevt,
+			 samples[CPUCLOCK_VIRT], SIGVTALRM);
+
+	soft = task_rlimit(tsk, RLIMIT_CPU);
+	if (soft != RLIM_INFINITY) {
+		/* RLIMIT_CPU is in seconds. Samples are nanoseconds */
+		unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
+		u64 ptime = samples[CPUCLOCK_PROF];
+		u64 softns = (u64)soft * NSEC_PER_SEC;
+		u64 hardns = (u64)hard * NSEC_PER_SEC;
+
+		/* At the hard limit, send SIGKILL. No further action. */
+		if (hard != RLIM_INFINITY &&
+		    check_rlimit(ptime, hardns, SIGKILL, false, true))
+			return;
+
+		/* At the soft limit, send a SIGXCPU every second */
+		if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
+			sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
+			softns += NSEC_PER_SEC;
+		}
+
+		/* Update the expiry cache */
+		if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
+			pct->bases[CPUCLOCK_PROF].nextevt = softns;
+	}
+
+	if (expiry_cache_is_inactive(pct))
+		stop_process_timers(sig);
+
+	pct->expiry_active = false;
+}
+
+/*
+ * This is called from the signal code (via posixtimer_rearm)
+ * when the last timer signal was delivered and we have to reload the timer.
+ */
+static void posix_cpu_timer_rearm(struct k_itimer *timer)
+{
+	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
+	struct task_struct *p;
+	struct sighand_struct *sighand;
+	unsigned long flags;
+	u64 now;
+
+	rcu_read_lock();
+	p = cpu_timer_task_rcu(timer);
+	if (!p)
+		goto out;
+
+	/* Protect timer list r/w in arm_timer() */
+	sighand = lock_task_sighand(p, &flags);
+	if (unlikely(sighand == NULL))
+		goto out;
+
+	/*
+	 * Fetch the current sample and update the timer's expiry time.
+	 */
+	if (CPUCLOCK_PERTHREAD(timer->it_clock))
+		now = cpu_clock_sample(clkid, p);
+	else
+		now = cpu_clock_sample_group(clkid, p, true);
+
+	bump_cpu_timer(timer, now);
+
+	/*
+	 * Now re-arm for the new expiry time.
+	 */
+	arm_timer(timer, p);
+	unlock_task_sighand(p, &flags);
+out:
+	rcu_read_unlock();
+}
+
+/**
+ * task_cputimers_expired - Check whether posix CPU timers are expired
+ *
+ * @samples:	Array of current samples for the CPUCLOCK clocks
+ * @pct:	Pointer to a posix_cputimers container
+ *
+ * Returns true if any member of @samples is greater than the corresponding
+ * member of @pct->bases[CLK].nextevt. False otherwise
+ */
+static inline bool
+task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
+{
+	int i;
+
+	for (i = 0; i < CPUCLOCK_MAX; i++) {
+		if (samples[i] >= pct->bases[i].nextevt)
+			return true;
+	}
+	return false;
+}
+
+/**
+ * fastpath_timer_check - POSIX CPU timers fast path.
+ *
+ * @tsk:	The task (thread) being checked.
+ *
+ * Check the task and thread group timers.  If both are zero (there are no
+ * timers set) return false.  Otherwise snapshot the task and thread group
+ * timers and compare them with the corresponding expiration times.  Return
+ * true if a timer has expired, else return false.
+ */
+static inline bool fastpath_timer_check(struct task_struct *tsk)
+{
+	struct posix_cputimers *pct = &tsk->posix_cputimers;
+	struct signal_struct *sig;
+
+	if (!expiry_cache_is_inactive(pct)) {
+		u64 samples[CPUCLOCK_MAX];
+
+		task_sample_cputime(tsk, samples);
+		if (task_cputimers_expired(samples, pct))
+			return true;
+	}
+
+	sig = tsk->signal;
+	pct = &sig->posix_cputimers;
+	/*
+	 * Check if thread group timers expired when timers are active and
+	 * no other thread in the group is already handling expiry for
+	 * thread group cputimers. These fields are read without the
+	 * sighand lock. However, this is fine because this is meant to be
+	 * a fastpath heuristic to determine whether we should try to
+	 * acquire the sighand lock to handle timer expiry.
+	 *
+	 * In the worst case scenario, if concurrently timers_active is set
+	 * or expiry_active is cleared, but the current thread doesn't see
+	 * the change yet, the timer checks are delayed until the next
+	 * thread in the group gets a scheduler interrupt to handle the
+	 * timer. This isn't an issue in practice because these types of
+	 * delays with signals actually getting sent are expected.
+	 */
+	if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
+		u64 samples[CPUCLOCK_MAX];
+
+		proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
+					   samples);
+
+		if (task_cputimers_expired(samples, pct))
+			return true;
+	}
+
+	if (dl_task(tsk) && tsk->dl.dl_overrun)
+		return true;
+
+	return false;
+}
+
+static void handle_posix_cpu_timers(struct task_struct *tsk);
+
+#ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
+static void posix_cpu_timers_work(struct callback_head *work)
+{
+	struct posix_cputimers_work *cw = container_of(work, typeof(*cw), work);
+
+	mutex_lock(&cw->mutex);
+	handle_posix_cpu_timers(current);
+	mutex_unlock(&cw->mutex);
+}
+
+/*
+ * Invoked from the posix-timer core when a cancel operation failed because
+ * the timer is marked firing. The caller holds rcu_read_lock(), which
+ * protects the timer and the task which is expiring it from being freed.
+ */
+static void posix_cpu_timer_wait_running(struct k_itimer *timr)
+{
+	struct task_struct *tsk = rcu_dereference(timr->it.cpu.handling);
+
+	/* Has the handling task completed expiry already? */
+	if (!tsk)
+		return;
+
+	/* Ensure that the task cannot go away */
+	get_task_struct(tsk);
+	/* Now drop the RCU protection so the mutex can be locked */
+	rcu_read_unlock();
+	/* Wait on the expiry mutex */
+	mutex_lock(&tsk->posix_cputimers_work.mutex);
+	/* Release it immediately again. */
+	mutex_unlock(&tsk->posix_cputimers_work.mutex);
+	/* Drop the task reference. */
+	put_task_struct(tsk);
+	/* Relock RCU so the callsite is balanced */
+	rcu_read_lock();
+}
+
+static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
+{
+	/* Ensure that timr->it.cpu.handling task cannot go away */
+	rcu_read_lock();
+	spin_unlock_irq(&timr->it_lock);
+	posix_cpu_timer_wait_running(timr);
+	rcu_read_unlock();
+	/* @timr is on stack and is valid */
+	spin_lock_irq(&timr->it_lock);
+}
+
+/*
+ * Clear existing posix CPU timers task work.
+ */
+void clear_posix_cputimers_work(struct task_struct *p)
+{
+	/*
+	 * A copied work entry from the old task is not meaningful, clear it.
+	 * N.B. init_task_work will not do this.
+	 */
+	memset(&p->posix_cputimers_work.work, 0,
+	       sizeof(p->posix_cputimers_work.work));
+	init_task_work(&p->posix_cputimers_work.work,
+		       posix_cpu_timers_work);
+	mutex_init(&p->posix_cputimers_work.mutex);
+	p->posix_cputimers_work.scheduled = false;
+}
+
+/*
+ * Initialize posix CPU timers task work in init task. Out of line to
+ * keep the callback static and to avoid header recursion hell.
+ */
+void __init posix_cputimers_init_work(void)
+{
+	clear_posix_cputimers_work(current);
+}
+
+/*
+ * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
+ * in hard interrupt context or in task context with interrupts
+ * disabled. Aside of that the writer/reader interaction is always in the
+ * context of the current task, which means they are strict per CPU.
+ */
+static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
+{
+	return tsk->posix_cputimers_work.scheduled;
+}
+
+static inline void __run_posix_cpu_timers(struct task_struct *tsk)
+{
+	if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
+		return;
+
+	/* Schedule task work to actually expire the timers */
+	tsk->posix_cputimers_work.scheduled = true;
+	task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
+}
+
+static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
+						unsigned long start)
+{
+	bool ret = true;
+
+	/*
+	 * On !RT kernels interrupts are disabled while collecting expired
+	 * timers, so no tick can happen and the fast path check can be
+	 * reenabled without further checks.
+	 */
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+		tsk->posix_cputimers_work.scheduled = false;
+		return true;
+	}
+
+	/*
+	 * On RT enabled kernels ticks can happen while the expired timers
+	 * are collected under sighand lock. But any tick which observes
+	 * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
+	 * checks. So reenabling the tick work has do be done carefully:
+	 *
+	 * Disable interrupts and run the fast path check if jiffies have
+	 * advanced since the collecting of expired timers started. If
+	 * jiffies have not advanced or the fast path check did not find
+	 * newly expired timers, reenable the fast path check in the timer
+	 * interrupt. If there are newly expired timers, return false and
+	 * let the collection loop repeat.
+	 */
+	local_irq_disable();
+	if (start != jiffies && fastpath_timer_check(tsk))
+		ret = false;
+	else
+		tsk->posix_cputimers_work.scheduled = false;
+	local_irq_enable();
+
+	return ret;
+}
+#else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
+static inline void __run_posix_cpu_timers(struct task_struct *tsk)
+{
+	lockdep_posixtimer_enter();
+	handle_posix_cpu_timers(tsk);
+	lockdep_posixtimer_exit();
+}
+
+static void posix_cpu_timer_wait_running(struct k_itimer *timr)
+{
+	cpu_relax();
+}
+
+static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr)
+{
+	spin_unlock_irq(&timr->it_lock);
+	cpu_relax();
+	spin_lock_irq(&timr->it_lock);
+}
+
+static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
+{
+	return false;
+}
+
+static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
+						unsigned long start)
+{
+	return true;
+}
+#endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
+
+static void handle_posix_cpu_timers(struct task_struct *tsk)
+{
+	struct k_itimer *timer, *next;
+	unsigned long flags, start;
+	LIST_HEAD(firing);
+
+	if (!lock_task_sighand(tsk, &flags))
+		return;
+
+	do {
+		/*
+		 * On RT locking sighand lock does not disable interrupts,
+		 * so this needs to be careful vs. ticks. Store the current
+		 * jiffies value.
+		 */
+		start = READ_ONCE(jiffies);
+		barrier();
+
+		/*
+		 * Here we take off tsk->signal->cpu_timers[N] and
+		 * tsk->cpu_timers[N] all the timers that are firing, and
+		 * put them on the firing list.
+		 */
+		check_thread_timers(tsk, &firing);
+
+		check_process_timers(tsk, &firing);
+
+		/*
+		 * The above timer checks have updated the expiry cache and
+		 * because nothing can have queued or modified timers after
+		 * sighand lock was taken above it is guaranteed to be
+		 * consistent. So the next timer interrupt fastpath check
+		 * will find valid data.
+		 *
+		 * If timer expiry runs in the timer interrupt context then
+		 * the loop is not relevant as timers will be directly
+		 * expired in interrupt context. The stub function below
+		 * returns always true which allows the compiler to
+		 * optimize the loop out.
+		 *
+		 * If timer expiry is deferred to task work context then
+		 * the following rules apply:
+		 *
+		 * - On !RT kernels no tick can have happened on this CPU
+		 *   after sighand lock was acquired because interrupts are
+		 *   disabled. So reenabling task work before dropping
+		 *   sighand lock and reenabling interrupts is race free.
+		 *
+		 * - On RT kernels ticks might have happened but the tick
+		 *   work ignored posix CPU timer handling because the
+		 *   CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
+		 *   must be done very carefully including a check whether
+		 *   ticks have happened since the start of the timer
+		 *   expiry checks. posix_cpu_timers_enable_work() takes
+		 *   care of that and eventually lets the expiry checks
+		 *   run again.
+		 */
+	} while (!posix_cpu_timers_enable_work(tsk, start));
+
+	/*
+	 * We must release sighand lock before taking any timer's lock.
+	 * There is a potential race with timer deletion here, as the
+	 * siglock now protects our private firing list.  We have set
+	 * the firing flag in each timer, so that a deletion attempt
+	 * that gets the timer lock before we do will give it up and
+	 * spin until we've taken care of that timer below.
+	 */
+	unlock_task_sighand(tsk, &flags);
+
+	/*
+	 * Now that all the timers on our list have the firing flag,
+	 * no one will touch their list entries but us.  We'll take
+	 * each timer's lock before clearing its firing flag, so no
+	 * timer call will interfere.
+	 */
+	list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
+		int cpu_firing;
+
+		/*
+		 * spin_lock() is sufficient here even independent of the
+		 * expiry context. If expiry happens in hard interrupt
+		 * context it's obvious. For task work context it's safe
+		 * because all other operations on timer::it_lock happen in
+		 * task context (syscall or exit).
+		 */
+		spin_lock(&timer->it_lock);
+		list_del_init(&timer->it.cpu.elist);
+		cpu_firing = timer->it.cpu.firing;
+		timer->it.cpu.firing = 0;
+		/*
+		 * The firing flag is -1 if we collided with a reset
+		 * of the timer, which already reported this
+		 * almost-firing as an overrun.  So don't generate an event.
+		 */
+		if (likely(cpu_firing >= 0))
+			cpu_timer_fire(timer);
+		/* See posix_cpu_timer_wait_running() */
+		rcu_assign_pointer(timer->it.cpu.handling, NULL);
+		spin_unlock(&timer->it_lock);
+	}
+}
+
+/*
+ * This is called from the timer interrupt handler.  The irq handler has
+ * already updated our counts.  We need to check if any timers fire now.
+ * Interrupts are disabled.
+ */
+void run_posix_cpu_timers(void)
+{
+	struct task_struct *tsk = current;
+
+	lockdep_assert_irqs_disabled();
+
+	/*
+	 * If the actual expiry is deferred to task work context and the
+	 * work is already scheduled there is no point to do anything here.
+	 */
+	if (posix_cpu_timers_work_scheduled(tsk))
+		return;
+
+	/*
+	 * The fast path checks that there are no expired thread or thread
+	 * group timers.  If that's so, just return.
+	 */
+	if (!fastpath_timer_check(tsk))
+		return;
+
+	__run_posix_cpu_timers(tsk);
+}
+
+/*
+ * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
+ * The tsk->sighand->siglock must be held by the caller.
+ */
+void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
+			   u64 *newval, u64 *oldval)
+{
+	u64 now, *nextevt;
+
+	if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
+		return;
+
+	nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
+	now = cpu_clock_sample_group(clkid, tsk, true);
+
+	if (oldval) {
+		/*
+		 * We are setting itimer. The *oldval is absolute and we update
+		 * it to be relative, *newval argument is relative and we update
+		 * it to be absolute.
+		 */
+		if (*oldval) {
+			if (*oldval <= now) {
+				/* Just about to fire. */
+				*oldval = TICK_NSEC;
+			} else {
+				*oldval -= now;
+			}
+		}
+
+		if (*newval)
+			*newval += now;
+	}
+
+	/*
+	 * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
+	 * expiry cache is also used by RLIMIT_CPU!.
+	 */
+	if (*newval < *nextevt)
+		*nextevt = *newval;
+
+	tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
+}
+
+static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
+			    const struct timespec64 *rqtp)
+{
+	struct itimerspec64 it;
+	struct k_itimer timer;
+	u64 expires;
+	int error;
+
+	/*
+	 * Set up a temporary timer and then wait for it to go off.
+	 */
+	memset(&timer, 0, sizeof timer);
+	spin_lock_init(&timer.it_lock);
+	timer.it_clock = which_clock;
+	timer.it_overrun = -1;
+	error = posix_cpu_timer_create(&timer);
+	timer.it_process = current;
+
+	if (!error) {
+		static struct itimerspec64 zero_it;
+		struct restart_block *restart;
+
+		memset(&it, 0, sizeof(it));
+		it.it_value = *rqtp;
+
+		spin_lock_irq(&timer.it_lock);
+		error = posix_cpu_timer_set(&timer, flags, &it, NULL);
+		if (error) {
+			spin_unlock_irq(&timer.it_lock);
+			return error;
+		}
+
+		while (!signal_pending(current)) {
+			if (!cpu_timer_getexpires(&timer.it.cpu)) {
+				/*
+				 * Our timer fired and was reset, below
+				 * deletion can not fail.
+				 */
+				posix_cpu_timer_del(&timer);
+				spin_unlock_irq(&timer.it_lock);
+				return 0;
+			}
+
+			/*
+			 * Block until cpu_timer_fire (or a signal) wakes us.
+			 */
+			__set_current_state(TASK_INTERRUPTIBLE);
+			spin_unlock_irq(&timer.it_lock);
+			schedule();
+			spin_lock_irq(&timer.it_lock);
+		}
+
+		/*
+		 * We were interrupted by a signal.
+		 */
+		expires = cpu_timer_getexpires(&timer.it.cpu);
+		error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
+		if (!error) {
+			/* Timer is now unarmed, deletion can not fail. */
+			posix_cpu_timer_del(&timer);
+		} else {
+			while (error == TIMER_RETRY) {
+				posix_cpu_timer_wait_running_nsleep(&timer);
+				error = posix_cpu_timer_del(&timer);
+			}
+		}
+
+		spin_unlock_irq(&timer.it_lock);
+
+		if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
+			/*
+			 * It actually did fire already.
+			 */
+			return 0;
+		}
+
+		error = -ERESTART_RESTARTBLOCK;
+		/*
+		 * Report back to the user the time still remaining.
+		 */
+		restart = &current->restart_block;
+		restart->nanosleep.expires = expires;
+		if (restart->nanosleep.type != TT_NONE)
+			error = nanosleep_copyout(restart, &it.it_value);
+	}
+
+	return error;
+}
+
+static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
+
+static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
+			    const struct timespec64 *rqtp)
+{
+	struct restart_block *restart_block = &current->restart_block;
+	int error;
+
+	/*
+	 * Diagnose required errors first.
+	 */
+	if (CPUCLOCK_PERTHREAD(which_clock) &&
+	    (CPUCLOCK_PID(which_clock) == 0 ||
+	     CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
+		return -EINVAL;
+
+	error = do_cpu_nanosleep(which_clock, flags, rqtp);
+
+	if (error == -ERESTART_RESTARTBLOCK) {
+
+		if (flags & TIMER_ABSTIME)
+			return -ERESTARTNOHAND;
+
+		restart_block->nanosleep.clockid = which_clock;
+		set_restart_fn(restart_block, posix_cpu_nsleep_restart);
+	}
+	return error;
+}
+
+static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
+{
+	clockid_t which_clock = restart_block->nanosleep.clockid;
+	struct timespec64 t;
+
+	t = ns_to_timespec64(restart_block->nanosleep.expires);
+
+	return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
+}
+
+#define PROCESS_CLOCK	make_process_cpuclock(0, CPUCLOCK_SCHED)
+#define THREAD_CLOCK	make_thread_cpuclock(0, CPUCLOCK_SCHED)
+
+static int process_cpu_clock_getres(const clockid_t which_clock,
+				    struct timespec64 *tp)
+{
+	return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
+}
+static int process_cpu_clock_get(const clockid_t which_clock,
+				 struct timespec64 *tp)
+{
+	return posix_cpu_clock_get(PROCESS_CLOCK, tp);
+}
+static int process_cpu_timer_create(struct k_itimer *timer)
+{
+	timer->it_clock = PROCESS_CLOCK;
+	return posix_cpu_timer_create(timer);
+}
+static int process_cpu_nsleep(const clockid_t which_clock, int flags,
+			      const struct timespec64 *rqtp)
+{
+	return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
+}
+static int thread_cpu_clock_getres(const clockid_t which_clock,
+				   struct timespec64 *tp)
+{
+	return posix_cpu_clock_getres(THREAD_CLOCK, tp);
+}
+static int thread_cpu_clock_get(const clockid_t which_clock,
+				struct timespec64 *tp)
+{
+	return posix_cpu_clock_get(THREAD_CLOCK, tp);
+}
+static int thread_cpu_timer_create(struct k_itimer *timer)
+{
+	timer->it_clock = THREAD_CLOCK;
+	return posix_cpu_timer_create(timer);
+}
+
+const struct k_clock clock_posix_cpu = {
+	.clock_getres		= posix_cpu_clock_getres,
+	.clock_set		= posix_cpu_clock_set,
+	.clock_get_timespec	= posix_cpu_clock_get,
+	.timer_create		= posix_cpu_timer_create,
+	.nsleep			= posix_cpu_nsleep,
+	.timer_set		= posix_cpu_timer_set,
+	.timer_del		= posix_cpu_timer_del,
+	.timer_get		= posix_cpu_timer_get,
+	.timer_rearm		= posix_cpu_timer_rearm,
+	.timer_wait_running	= posix_cpu_timer_wait_running,
+};
+
+const struct k_clock clock_process = {
+	.clock_getres		= process_cpu_clock_getres,
+	.clock_get_timespec	= process_cpu_clock_get,
+	.timer_create		= process_cpu_timer_create,
+	.nsleep			= process_cpu_nsleep,
+};
+
+const struct k_clock clock_thread = {
+	.clock_getres		= thread_cpu_clock_getres,
+	.clock_get_timespec	= thread_cpu_clock_get,
+	.timer_create		= thread_cpu_timer_create,
+};
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
new file mode 100644
index 0000000000..9b6fcb8d85
--- /dev/null
+++ b/kernel/time/posix-stubs.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dummy stubs used when CONFIG_POSIX_TIMERS=n
+ *
+ * Created by:  Nicolas Pitre, July 2016
+ * Copyright:   (C) 2016 Linaro Limited
+ */
+
+#include <linux/linkage.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/syscalls.h>
+#include <linux/ktime.h>
+#include <linux/timekeeping.h>
+#include <linux/posix-timers.h>
+#include <linux/time_namespace.h>
+#include <linux/compat.h>
+
+/*
+ * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC
+ * as it is easy to remain compatible with little code. CLOCK_BOOTTIME
+ * is also included for convenience as at least systemd uses it.
+ */
+
+SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
+		const struct __kernel_timespec __user *, tp)
+{
+	struct timespec64 new_tp;
+
+	if (which_clock != CLOCK_REALTIME)
+		return -EINVAL;
+	if (get_timespec64(&new_tp, tp))
+		return -EFAULT;
+
+	return do_sys_settimeofday64(&new_tp, NULL);
+}
+
+static int do_clock_gettime(clockid_t which_clock, struct timespec64 *tp)
+{
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+		ktime_get_real_ts64(tp);
+		break;
+	case CLOCK_MONOTONIC:
+		ktime_get_ts64(tp);
+		timens_add_monotonic(tp);
+		break;
+	case CLOCK_BOOTTIME:
+		ktime_get_boottime_ts64(tp);
+		timens_add_boottime(tp);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
+		struct __kernel_timespec __user *, tp)
+{
+	int ret;
+	struct timespec64 kernel_tp;
+
+	ret = do_clock_gettime(which_clock, &kernel_tp);
+	if (ret)
+		return ret;
+
+	if (put_timespec64(&kernel_tp, tp))
+		return -EFAULT;
+	return 0;
+}
+
+SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock, struct __kernel_timespec __user *, tp)
+{
+	struct timespec64 rtn_tp = {
+		.tv_sec = 0,
+		.tv_nsec = hrtimer_resolution,
+	};
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		if (put_timespec64(&rtn_tp, tp))
+			return -EFAULT;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
+		const struct __kernel_timespec __user *, rqtp,
+		struct __kernel_timespec __user *, rmtp)
+{
+	struct timespec64 t;
+	ktime_t texp;
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (get_timespec64(&t, rqtp))
+		return -EFAULT;
+	if (!timespec64_valid(&t))
+		return -EINVAL;
+	if (flags & TIMER_ABSTIME)
+		rmtp = NULL;
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
+	current->restart_block.nanosleep.rmtp = rmtp;
+	texp = timespec64_to_ktime(t);
+	if (flags & TIMER_ABSTIME)
+		texp = timens_ktime_to_host(which_clock, texp);
+	return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
+				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+				 which_clock);
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+
+SYSCALL_DEFINE2(clock_settime32, const clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	struct timespec64 new_tp;
+
+	if (which_clock != CLOCK_REALTIME)
+		return -EINVAL;
+	if (get_old_timespec32(&new_tp, tp))
+		return -EFAULT;
+
+	return do_sys_settimeofday64(&new_tp, NULL);
+}
+
+SYSCALL_DEFINE2(clock_gettime32, clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	int ret;
+	struct timespec64 kernel_tp;
+
+	ret = do_clock_gettime(which_clock, &kernel_tp);
+	if (ret)
+		return ret;
+
+	if (put_old_timespec32(&kernel_tp, tp))
+		return -EFAULT;
+	return 0;
+}
+
+SYSCALL_DEFINE2(clock_getres_time32, clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	struct timespec64 rtn_tp = {
+		.tv_sec = 0,
+		.tv_nsec = hrtimer_resolution,
+	};
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		if (put_old_timespec32(&rtn_tp, tp))
+			return -EFAULT;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags,
+		struct old_timespec32 __user *, rqtp,
+		struct old_timespec32 __user *, rmtp)
+{
+	struct timespec64 t;
+	ktime_t texp;
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (get_old_timespec32(&t, rqtp))
+		return -EFAULT;
+	if (!timespec64_valid(&t))
+		return -EINVAL;
+	if (flags & TIMER_ABSTIME)
+		rmtp = NULL;
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
+	current->restart_block.nanosleep.compat_rmtp = rmtp;
+	texp = timespec64_to_ktime(t);
+	if (flags & TIMER_ABSTIME)
+		texp = timens_ktime_to_host(which_clock, texp);
+	return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
+				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+				 which_clock);
+}
+#endif
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
new file mode 100644
index 0000000000..b924f0f096
--- /dev/null
+++ b/kernel/time/posix-timers.c
@@ -0,0 +1,1541 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * 2002-10-15  Posix Clocks & timers
+ *                           by George Anzinger george@mvista.com
+ *			     Copyright (C) 2002 2003 by MontaVista Software.
+ *
+ * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
+ *			     Copyright (C) 2004 Boris Hu
+ *
+ * These are all the functions necessary to implement POSIX clocks & timers
+ */
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include <linux/mutex.h>
+#include <linux/sched/task.h>
+
+#include <linux/uaccess.h>
+#include <linux/list.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/hash.h>
+#include <linux/posix-clock.h>
+#include <linux/posix-timers.h>
+#include <linux/syscalls.h>
+#include <linux/wait.h>
+#include <linux/workqueue.h>
+#include <linux/export.h>
+#include <linux/hashtable.h>
+#include <linux/compat.h>
+#include <linux/nospec.h>
+#include <linux/time_namespace.h>
+
+#include "timekeeping.h"
+#include "posix-timers.h"
+
+static struct kmem_cache *posix_timers_cache;
+
+/*
+ * Timers are managed in a hash table for lockless lookup. The hash key is
+ * constructed from current::signal and the timer ID and the timer is
+ * matched against current::signal and the timer ID when walking the hash
+ * bucket list.
+ *
+ * This allows checkpoint/restore to reconstruct the exact timer IDs for
+ * a process.
+ */
+static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
+static DEFINE_SPINLOCK(hash_lock);
+
+static const struct k_clock * const posix_clocks[];
+static const struct k_clock *clockid_to_kclock(const clockid_t id);
+static const struct k_clock clock_realtime, clock_monotonic;
+
+/* SIGEV_THREAD_ID cannot share a bit with the other SIGEV values. */
+#if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
+			~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
+#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
+#endif
+
+static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);
+
+#define lock_timer(tid, flags)						   \
+({	struct k_itimer *__timr;					   \
+	__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags));  \
+	__timr;								   \
+})
+
+static int hash(struct signal_struct *sig, unsigned int nr)
+{
+	return hash_32(hash32_ptr(sig) ^ nr, HASH_BITS(posix_timers_hashtable));
+}
+
+static struct k_itimer *__posix_timers_find(struct hlist_head *head,
+					    struct signal_struct *sig,
+					    timer_t id)
+{
+	struct k_itimer *timer;
+
+	hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&hash_lock)) {
+		/* timer->it_signal can be set concurrently */
+		if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id))
+			return timer;
+	}
+	return NULL;
+}
+
+static struct k_itimer *posix_timer_by_id(timer_t id)
+{
+	struct signal_struct *sig = current->signal;
+	struct hlist_head *head = &posix_timers_hashtable[hash(sig, id)];
+
+	return __posix_timers_find(head, sig, id);
+}
+
+static int posix_timer_add(struct k_itimer *timer)
+{
+	struct signal_struct *sig = current->signal;
+	struct hlist_head *head;
+	unsigned int cnt, id;
+
+	/*
+	 * FIXME: Replace this by a per signal struct xarray once there is
+	 * a plan to handle the resulting CRIU regression gracefully.
+	 */
+	for (cnt = 0; cnt <= INT_MAX; cnt++) {
+		spin_lock(&hash_lock);
+		id = sig->next_posix_timer_id;
+
+		/* Write the next ID back. Clamp it to the positive space */
+		sig->next_posix_timer_id = (id + 1) & INT_MAX;
+
+		head = &posix_timers_hashtable[hash(sig, id)];
+		if (!__posix_timers_find(head, sig, id)) {
+			hlist_add_head_rcu(&timer->t_hash, head);
+			spin_unlock(&hash_lock);
+			return id;
+		}
+		spin_unlock(&hash_lock);
+	}
+	/* POSIX return code when no timer ID could be allocated */
+	return -EAGAIN;
+}
+
+static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
+{
+	spin_unlock_irqrestore(&timr->it_lock, flags);
+}
+
+static int posix_get_realtime_timespec(clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_real_ts64(tp);
+	return 0;
+}
+
+static ktime_t posix_get_realtime_ktime(clockid_t which_clock)
+{
+	return ktime_get_real();
+}
+
+static int posix_clock_realtime_set(const clockid_t which_clock,
+				    const struct timespec64 *tp)
+{
+	return do_sys_settimeofday64(tp, NULL);
+}
+
+static int posix_clock_realtime_adj(const clockid_t which_clock,
+				    struct __kernel_timex *t)
+{
+	return do_adjtimex(t);
+}
+
+static int posix_get_monotonic_timespec(clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_ts64(tp);
+	timens_add_monotonic(tp);
+	return 0;
+}
+
+static ktime_t posix_get_monotonic_ktime(clockid_t which_clock)
+{
+	return ktime_get();
+}
+
+static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_raw_ts64(tp);
+	timens_add_monotonic(tp);
+	return 0;
+}
+
+static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_coarse_real_ts64(tp);
+	return 0;
+}
+
+static int posix_get_monotonic_coarse(clockid_t which_clock,
+						struct timespec64 *tp)
+{
+	ktime_get_coarse_ts64(tp);
+	timens_add_monotonic(tp);
+	return 0;
+}
+
+static int posix_get_coarse_res(const clockid_t which_clock, struct timespec64 *tp)
+{
+	*tp = ktime_to_timespec64(KTIME_LOW_RES);
+	return 0;
+}
+
+static int posix_get_boottime_timespec(const clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_boottime_ts64(tp);
+	timens_add_boottime(tp);
+	return 0;
+}
+
+static ktime_t posix_get_boottime_ktime(const clockid_t which_clock)
+{
+	return ktime_get_boottime();
+}
+
+static int posix_get_tai_timespec(clockid_t which_clock, struct timespec64 *tp)
+{
+	ktime_get_clocktai_ts64(tp);
+	return 0;
+}
+
+static ktime_t posix_get_tai_ktime(clockid_t which_clock)
+{
+	return ktime_get_clocktai();
+}
+
+static int posix_get_hrtimer_res(clockid_t which_clock, struct timespec64 *tp)
+{
+	tp->tv_sec = 0;
+	tp->tv_nsec = hrtimer_resolution;
+	return 0;
+}
+
+static __init int init_posix_timers(void)
+{
+	posix_timers_cache = kmem_cache_create("posix_timers_cache",
+					sizeof(struct k_itimer), 0,
+					SLAB_PANIC | SLAB_ACCOUNT, NULL);
+	return 0;
+}
+__initcall(init_posix_timers);
+
+/*
+ * The siginfo si_overrun field and the return value of timer_getoverrun(2)
+ * are of type int. Clamp the overrun value to INT_MAX
+ */
+static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval)
+{
+	s64 sum = timr->it_overrun_last + (s64)baseval;
+
+	return sum > (s64)INT_MAX ? INT_MAX : (int)sum;
+}
+
+static void common_hrtimer_rearm(struct k_itimer *timr)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+
+	timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(),
+					    timr->it_interval);
+	hrtimer_restart(timer);
+}
+
+/*
+ * This function is called from the signal delivery code if
+ * info->si_sys_private is not zero, which indicates that the timer has to
+ * be rearmed. Restart the timer and update info::si_overrun.
+ */
+void posixtimer_rearm(struct kernel_siginfo *info)
+{
+	struct k_itimer *timr;
+	unsigned long flags;
+
+	timr = lock_timer(info->si_tid, &flags);
+	if (!timr)
+		return;
+
+	if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) {
+		timr->kclock->timer_rearm(timr);
+
+		timr->it_active = 1;
+		timr->it_overrun_last = timr->it_overrun;
+		timr->it_overrun = -1LL;
+		++timr->it_requeue_pending;
+
+		info->si_overrun = timer_overrun_to_int(timr, info->si_overrun);
+	}
+
+	unlock_timer(timr, flags);
+}
+
+int posix_timer_event(struct k_itimer *timr, int si_private)
+{
+	enum pid_type type;
+	int ret;
+	/*
+	 * FIXME: if ->sigq is queued we can race with
+	 * dequeue_signal()->posixtimer_rearm().
+	 *
+	 * If dequeue_signal() sees the "right" value of
+	 * si_sys_private it calls posixtimer_rearm().
+	 * We re-queue ->sigq and drop ->it_lock().
+	 * posixtimer_rearm() locks the timer
+	 * and re-schedules it while ->sigq is pending.
+	 * Not really bad, but not that we want.
+	 */
+	timr->sigq->info.si_sys_private = si_private;
+
+	type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;
+	ret = send_sigqueue(timr->sigq, timr->it_pid, type);
+	/* If we failed to send the signal the timer stops. */
+	return ret > 0;
+}
+
+/*
+ * This function gets called when a POSIX.1b interval timer expires from
+ * the HRTIMER interrupt (soft interrupt on RT kernels).
+ *
+ * Handles CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_BOOTTIME and CLOCK_TAI
+ * based timers.
+ */
+static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
+{
+	enum hrtimer_restart ret = HRTIMER_NORESTART;
+	struct k_itimer *timr;
+	unsigned long flags;
+	int si_private = 0;
+
+	timr = container_of(timer, struct k_itimer, it.real.timer);
+	spin_lock_irqsave(&timr->it_lock, flags);
+
+	timr->it_active = 0;
+	if (timr->it_interval != 0)
+		si_private = ++timr->it_requeue_pending;
+
+	if (posix_timer_event(timr, si_private)) {
+		/*
+		 * The signal was not queued due to SIG_IGN. As a
+		 * consequence the timer is not going to be rearmed from
+		 * the signal delivery path. But as a real signal handler
+		 * can be installed later the timer must be rearmed here.
+		 */
+		if (timr->it_interval != 0) {
+			ktime_t now = hrtimer_cb_get_time(timer);
+
+			/*
+			 * FIXME: What we really want, is to stop this
+			 * timer completely and restart it in case the
+			 * SIG_IGN is removed. This is a non trivial
+			 * change to the signal handling code.
+			 *
+			 * For now let timers with an interval less than a
+			 * jiffie expire every jiffie and recheck for a
+			 * valid signal handler.
+			 *
+			 * This avoids interrupt starvation in case of a
+			 * very small interval, which would expire the
+			 * timer immediately again.
+			 *
+			 * Moving now ahead of time by one jiffie tricks
+			 * hrtimer_forward() to expire the timer later,
+			 * while it still maintains the overrun accuracy
+			 * for the price of a slight inconsistency in the
+			 * timer_gettime() case. This is at least better
+			 * than a timer storm.
+			 *
+			 * Only required when high resolution timers are
+			 * enabled as the periodic tick based timers are
+			 * automatically aligned to the next tick.
+			 */
+			if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS)) {
+				ktime_t kj = TICK_NSEC;
+
+				if (timr->it_interval < kj)
+					now = ktime_add(now, kj);
+			}
+
+			timr->it_overrun += hrtimer_forward(timer, now, timr->it_interval);
+			ret = HRTIMER_RESTART;
+			++timr->it_requeue_pending;
+			timr->it_active = 1;
+		}
+	}
+
+	unlock_timer(timr, flags);
+	return ret;
+}
+
+static struct pid *good_sigevent(sigevent_t * event)
+{
+	struct pid *pid = task_tgid(current);
+	struct task_struct *rtn;
+
+	switch (event->sigev_notify) {
+	case SIGEV_SIGNAL | SIGEV_THREAD_ID:
+		pid = find_vpid(event->sigev_notify_thread_id);
+		rtn = pid_task(pid, PIDTYPE_PID);
+		if (!rtn || !same_thread_group(rtn, current))
+			return NULL;
+		fallthrough;
+	case SIGEV_SIGNAL:
+	case SIGEV_THREAD:
+		if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
+			return NULL;
+		fallthrough;
+	case SIGEV_NONE:
+		return pid;
+	default:
+		return NULL;
+	}
+}
+
+static struct k_itimer * alloc_posix_timer(void)
+{
+	struct k_itimer *tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL);
+
+	if (!tmr)
+		return tmr;
+	if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
+		kmem_cache_free(posix_timers_cache, tmr);
+		return NULL;
+	}
+	clear_siginfo(&tmr->sigq->info);
+	return tmr;
+}
+
+static void k_itimer_rcu_free(struct rcu_head *head)
+{
+	struct k_itimer *tmr = container_of(head, struct k_itimer, rcu);
+
+	kmem_cache_free(posix_timers_cache, tmr);
+}
+
+static void posix_timer_free(struct k_itimer *tmr)
+{
+	put_pid(tmr->it_pid);
+	sigqueue_free(tmr->sigq);
+	call_rcu(&tmr->rcu, k_itimer_rcu_free);
+}
+
+static void posix_timer_unhash_and_free(struct k_itimer *tmr)
+{
+	spin_lock(&hash_lock);
+	hlist_del_rcu(&tmr->t_hash);
+	spin_unlock(&hash_lock);
+	posix_timer_free(tmr);
+}
+
+static int common_timer_create(struct k_itimer *new_timer)
+{
+	hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
+	return 0;
+}
+
+/* Create a POSIX.1b interval timer. */
+static int do_timer_create(clockid_t which_clock, struct sigevent *event,
+			   timer_t __user *created_timer_id)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct k_itimer *new_timer;
+	int error, new_timer_id;
+
+	if (!kc)
+		return -EINVAL;
+	if (!kc->timer_create)
+		return -EOPNOTSUPP;
+
+	new_timer = alloc_posix_timer();
+	if (unlikely(!new_timer))
+		return -EAGAIN;
+
+	spin_lock_init(&new_timer->it_lock);
+
+	/*
+	 * Add the timer to the hash table. The timer is not yet valid
+	 * because new_timer::it_signal is still NULL. The timer id is also
+	 * not yet visible to user space.
+	 */
+	new_timer_id = posix_timer_add(new_timer);
+	if (new_timer_id < 0) {
+		posix_timer_free(new_timer);
+		return new_timer_id;
+	}
+
+	new_timer->it_id = (timer_t) new_timer_id;
+	new_timer->it_clock = which_clock;
+	new_timer->kclock = kc;
+	new_timer->it_overrun = -1LL;
+
+	if (event) {
+		rcu_read_lock();
+		new_timer->it_pid = get_pid(good_sigevent(event));
+		rcu_read_unlock();
+		if (!new_timer->it_pid) {
+			error = -EINVAL;
+			goto out;
+		}
+		new_timer->it_sigev_notify     = event->sigev_notify;
+		new_timer->sigq->info.si_signo = event->sigev_signo;
+		new_timer->sigq->info.si_value = event->sigev_value;
+	} else {
+		new_timer->it_sigev_notify     = SIGEV_SIGNAL;
+		new_timer->sigq->info.si_signo = SIGALRM;
+		memset(&new_timer->sigq->info.si_value, 0, sizeof(sigval_t));
+		new_timer->sigq->info.si_value.sival_int = new_timer->it_id;
+		new_timer->it_pid = get_pid(task_tgid(current));
+	}
+
+	new_timer->sigq->info.si_tid   = new_timer->it_id;
+	new_timer->sigq->info.si_code  = SI_TIMER;
+
+	if (copy_to_user(created_timer_id, &new_timer_id, sizeof (new_timer_id))) {
+		error = -EFAULT;
+		goto out;
+	}
+	/*
+	 * After succesful copy out, the timer ID is visible to user space
+	 * now but not yet valid because new_timer::signal is still NULL.
+	 *
+	 * Complete the initialization with the clock specific create
+	 * callback.
+	 */
+	error = kc->timer_create(new_timer);
+	if (error)
+		goto out;
+
+	spin_lock_irq(&current->sighand->siglock);
+	/* This makes the timer valid in the hash table */
+	WRITE_ONCE(new_timer->it_signal, current->signal);
+	list_add(&new_timer->list, &current->signal->posix_timers);
+	spin_unlock_irq(&current->sighand->siglock);
+	/*
+	 * After unlocking sighand::siglock @new_timer is subject to
+	 * concurrent removal and cannot be touched anymore
+	 */
+	return 0;
+out:
+	posix_timer_unhash_and_free(new_timer);
+	return error;
+}
+
+SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
+		struct sigevent __user *, timer_event_spec,
+		timer_t __user *, created_timer_id)
+{
+	if (timer_event_spec) {
+		sigevent_t event;
+
+		if (copy_from_user(&event, timer_event_spec, sizeof (event)))
+			return -EFAULT;
+		return do_timer_create(which_clock, &event, created_timer_id);
+	}
+	return do_timer_create(which_clock, NULL, created_timer_id);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE3(timer_create, clockid_t, which_clock,
+		       struct compat_sigevent __user *, timer_event_spec,
+		       timer_t __user *, created_timer_id)
+{
+	if (timer_event_spec) {
+		sigevent_t event;
+
+		if (get_compat_sigevent(&event, timer_event_spec))
+			return -EFAULT;
+		return do_timer_create(which_clock, &event, created_timer_id);
+	}
+	return do_timer_create(which_clock, NULL, created_timer_id);
+}
+#endif
+
+static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
+{
+	struct k_itimer *timr;
+
+	/*
+	 * timer_t could be any type >= int and we want to make sure any
+	 * @timer_id outside positive int range fails lookup.
+	 */
+	if ((unsigned long long)timer_id > INT_MAX)
+		return NULL;
+
+	/*
+	 * The hash lookup and the timers are RCU protected.
+	 *
+	 * Timers are added to the hash in invalid state where
+	 * timr::it_signal == NULL. timer::it_signal is only set after the
+	 * rest of the initialization succeeded.
+	 *
+	 * Timer destruction happens in steps:
+	 *  1) Set timr::it_signal to NULL with timr::it_lock held
+	 *  2) Release timr::it_lock
+	 *  3) Remove from the hash under hash_lock
+	 *  4) Call RCU for removal after the grace period
+	 *
+	 * Holding rcu_read_lock() accross the lookup ensures that
+	 * the timer cannot be freed.
+	 *
+	 * The lookup validates locklessly that timr::it_signal ==
+	 * current::it_signal and timr::it_id == @timer_id. timr::it_id
+	 * can't change, but timr::it_signal becomes NULL during
+	 * destruction.
+	 */
+	rcu_read_lock();
+	timr = posix_timer_by_id(timer_id);
+	if (timr) {
+		spin_lock_irqsave(&timr->it_lock, *flags);
+		/*
+		 * Validate under timr::it_lock that timr::it_signal is
+		 * still valid. Pairs with #1 above.
+		 */
+		if (timr->it_signal == current->signal) {
+			rcu_read_unlock();
+			return timr;
+		}
+		spin_unlock_irqrestore(&timr->it_lock, *flags);
+	}
+	rcu_read_unlock();
+
+	return NULL;
+}
+
+static ktime_t common_hrtimer_remaining(struct k_itimer *timr, ktime_t now)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+
+	return __hrtimer_expires_remaining_adjusted(timer, now);
+}
+
+static s64 common_hrtimer_forward(struct k_itimer *timr, ktime_t now)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+
+	return hrtimer_forward(timer, now, timr->it_interval);
+}
+
+/*
+ * Get the time remaining on a POSIX.1b interval timer.
+ *
+ * Two issues to handle here:
+ *
+ *  1) The timer has a requeue pending. The return value must appear as
+ *     if the timer has been requeued right now.
+ *
+ *  2) The timer is a SIGEV_NONE timer. These timers are never enqueued
+ *     into the hrtimer queue and therefore never expired. Emulate expiry
+ *     here taking #1 into account.
+ */
+void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
+{
+	const struct k_clock *kc = timr->kclock;
+	ktime_t now, remaining, iv;
+	bool sig_none;
+
+	sig_none = timr->it_sigev_notify == SIGEV_NONE;
+	iv = timr->it_interval;
+
+	/* interval timer ? */
+	if (iv) {
+		cur_setting->it_interval = ktime_to_timespec64(iv);
+	} else if (!timr->it_active) {
+		/*
+		 * SIGEV_NONE oneshot timers are never queued and therefore
+		 * timr->it_active is always false. The check below
+		 * vs. remaining time will handle this case.
+		 *
+		 * For all other timers there is nothing to update here, so
+		 * return.
+		 */
+		if (!sig_none)
+			return;
+	}
+
+	now = kc->clock_get_ktime(timr->it_clock);
+
+	/*
+	 * If this is an interval timer and either has requeue pending or
+	 * is a SIGEV_NONE timer move the expiry time forward by intervals,
+	 * so expiry is > now.
+	 */
+	if (iv && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))
+		timr->it_overrun += kc->timer_forward(timr, now);
+
+	remaining = kc->timer_remaining(timr, now);
+	/*
+	 * As @now is retrieved before a possible timer_forward() and
+	 * cannot be reevaluated by the compiler @remaining is based on the
+	 * same @now value. Therefore @remaining is consistent vs. @now.
+	 *
+	 * Consequently all interval timers, i.e. @iv > 0, cannot have a
+	 * remaining time <= 0 because timer_forward() guarantees to move
+	 * them forward so that the next timer expiry is > @now.
+	 */
+	if (remaining <= 0) {
+		/*
+		 * A single shot SIGEV_NONE timer must return 0, when it is
+		 * expired! Timers which have a real signal delivery mode
+		 * must return a remaining time greater than 0 because the
+		 * signal has not yet been delivered.
+		 */
+		if (!sig_none)
+			cur_setting->it_value.tv_nsec = 1;
+	} else {
+		cur_setting->it_value = ktime_to_timespec64(remaining);
+	}
+}
+
+static int do_timer_gettime(timer_t timer_id,  struct itimerspec64 *setting)
+{
+	const struct k_clock *kc;
+	struct k_itimer *timr;
+	unsigned long flags;
+	int ret = 0;
+
+	timr = lock_timer(timer_id, &flags);
+	if (!timr)
+		return -EINVAL;
+
+	memset(setting, 0, sizeof(*setting));
+	kc = timr->kclock;
+	if (WARN_ON_ONCE(!kc || !kc->timer_get))
+		ret = -EINVAL;
+	else
+		kc->timer_get(timr, setting);
+
+	unlock_timer(timr, flags);
+	return ret;
+}
+
+/* Get the time remaining on a POSIX.1b interval timer. */
+SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
+		struct __kernel_itimerspec __user *, setting)
+{
+	struct itimerspec64 cur_setting;
+
+	int ret = do_timer_gettime(timer_id, &cur_setting);
+	if (!ret) {
+		if (put_itimerspec64(&cur_setting, setting))
+			ret = -EFAULT;
+	}
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+
+SYSCALL_DEFINE2(timer_gettime32, timer_t, timer_id,
+		struct old_itimerspec32 __user *, setting)
+{
+	struct itimerspec64 cur_setting;
+
+	int ret = do_timer_gettime(timer_id, &cur_setting);
+	if (!ret) {
+		if (put_old_itimerspec32(&cur_setting, setting))
+			ret = -EFAULT;
+	}
+	return ret;
+}
+
+#endif
+
+/**
+ * sys_timer_getoverrun - Get the number of overruns of a POSIX.1b interval timer
+ * @timer_id:	The timer ID which identifies the timer
+ *
+ * The "overrun count" of a timer is one plus the number of expiration
+ * intervals which have elapsed between the first expiry, which queues the
+ * signal and the actual signal delivery. On signal delivery the "overrun
+ * count" is calculated and cached, so it can be returned directly here.
+ *
+ * As this is relative to the last queued signal the returned overrun count
+ * is meaningless outside of the signal delivery path and even there it
+ * does not accurately reflect the current state when user space evaluates
+ * it.
+ *
+ * Returns:
+ *	-EINVAL		@timer_id is invalid
+ *	1..INT_MAX	The number of overruns related to the last delivered signal
+ */
+SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
+{
+	struct k_itimer *timr;
+	unsigned long flags;
+	int overrun;
+
+	timr = lock_timer(timer_id, &flags);
+	if (!timr)
+		return -EINVAL;
+
+	overrun = timer_overrun_to_int(timr, 0);
+	unlock_timer(timr, flags);
+
+	return overrun;
+}
+
+static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
+			       bool absolute, bool sigev_none)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+	enum hrtimer_mode mode;
+
+	mode = absolute ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
+	/*
+	 * Posix magic: Relative CLOCK_REALTIME timers are not affected by
+	 * clock modifications, so they become CLOCK_MONOTONIC based under the
+	 * hood. See hrtimer_init(). Update timr->kclock, so the generic
+	 * functions which use timr->kclock->clock_get_*() work.
+	 *
+	 * Note: it_clock stays unmodified, because the next timer_set() might
+	 * use ABSTIME, so it needs to switch back.
+	 */
+	if (timr->it_clock == CLOCK_REALTIME)
+		timr->kclock = absolute ? &clock_realtime : &clock_monotonic;
+
+	hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
+	timr->it.real.timer.function = posix_timer_fn;
+
+	if (!absolute)
+		expires = ktime_add_safe(expires, timer->base->get_time());
+	hrtimer_set_expires(timer, expires);
+
+	if (!sigev_none)
+		hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+}
+
+static int common_hrtimer_try_to_cancel(struct k_itimer *timr)
+{
+	return hrtimer_try_to_cancel(&timr->it.real.timer);
+}
+
+static void common_timer_wait_running(struct k_itimer *timer)
+{
+	hrtimer_cancel_wait_running(&timer->it.real.timer);
+}
+
+/*
+ * On PREEMPT_RT this prevents priority inversion and a potential livelock
+ * against the ksoftirqd thread in case that ksoftirqd gets preempted while
+ * executing a hrtimer callback.
+ *
+ * See the comments in hrtimer_cancel_wait_running(). For PREEMPT_RT=n this
+ * just results in a cpu_relax().
+ *
+ * For POSIX CPU timers with CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n this is
+ * just a cpu_relax(). With CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this
+ * prevents spinning on an eventually scheduled out task and a livelock
+ * when the task which tries to delete or disarm the timer has preempted
+ * the task which runs the expiry in task work context.
+ */
+static struct k_itimer *timer_wait_running(struct k_itimer *timer,
+					   unsigned long *flags)
+{
+	const struct k_clock *kc = READ_ONCE(timer->kclock);
+	timer_t timer_id = READ_ONCE(timer->it_id);
+
+	/* Prevent kfree(timer) after dropping the lock */
+	rcu_read_lock();
+	unlock_timer(timer, *flags);
+
+	/*
+	 * kc->timer_wait_running() might drop RCU lock. So @timer
+	 * cannot be touched anymore after the function returns!
+	 */
+	if (!WARN_ON_ONCE(!kc->timer_wait_running))
+		kc->timer_wait_running(timer);
+
+	rcu_read_unlock();
+	/* Relock the timer. It might be not longer hashed. */
+	return lock_timer(timer_id, flags);
+}
+
+/* Set a POSIX.1b interval timer. */
+int common_timer_set(struct k_itimer *timr, int flags,
+		     struct itimerspec64 *new_setting,
+		     struct itimerspec64 *old_setting)
+{
+	const struct k_clock *kc = timr->kclock;
+	bool sigev_none;
+	ktime_t expires;
+
+	if (old_setting)
+		common_timer_get(timr, old_setting);
+
+	/* Prevent rearming by clearing the interval */
+	timr->it_interval = 0;
+	/*
+	 * Careful here. On SMP systems the timer expiry function could be
+	 * active and spinning on timr->it_lock.
+	 */
+	if (kc->timer_try_to_cancel(timr) < 0)
+		return TIMER_RETRY;
+
+	timr->it_active = 0;
+	timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
+		~REQUEUE_PENDING;
+	timr->it_overrun_last = 0;
+
+	/* Switch off the timer when it_value is zero */
+	if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
+		return 0;
+
+	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
+	expires = timespec64_to_ktime(new_setting->it_value);
+	if (flags & TIMER_ABSTIME)
+		expires = timens_ktime_to_host(timr->it_clock, expires);
+	sigev_none = timr->it_sigev_notify == SIGEV_NONE;
+
+	kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none);
+	timr->it_active = !sigev_none;
+	return 0;
+}
+
+static int do_timer_settime(timer_t timer_id, int tmr_flags,
+			    struct itimerspec64 *new_spec64,
+			    struct itimerspec64 *old_spec64)
+{
+	const struct k_clock *kc;
+	struct k_itimer *timr;
+	unsigned long flags;
+	int error = 0;
+
+	if (!timespec64_valid(&new_spec64->it_interval) ||
+	    !timespec64_valid(&new_spec64->it_value))
+		return -EINVAL;
+
+	if (old_spec64)
+		memset(old_spec64, 0, sizeof(*old_spec64));
+
+	timr = lock_timer(timer_id, &flags);
+retry:
+	if (!timr)
+		return -EINVAL;
+
+	kc = timr->kclock;
+	if (WARN_ON_ONCE(!kc || !kc->timer_set))
+		error = -EINVAL;
+	else
+		error = kc->timer_set(timr, tmr_flags, new_spec64, old_spec64);
+
+	if (error == TIMER_RETRY) {
+		// We already got the old time...
+		old_spec64 = NULL;
+		/* Unlocks and relocks the timer if it still exists */
+		timr = timer_wait_running(timr, &flags);
+		goto retry;
+	}
+	unlock_timer(timr, flags);
+
+	return error;
+}
+
+/* Set a POSIX.1b interval timer */
+SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
+		const struct __kernel_itimerspec __user *, new_setting,
+		struct __kernel_itimerspec __user *, old_setting)
+{
+	struct itimerspec64 new_spec, old_spec, *rtn;
+	int error = 0;
+
+	if (!new_setting)
+		return -EINVAL;
+
+	if (get_itimerspec64(&new_spec, new_setting))
+		return -EFAULT;
+
+	rtn = old_setting ? &old_spec : NULL;
+	error = do_timer_settime(timer_id, flags, &new_spec, rtn);
+	if (!error && old_setting) {
+		if (put_itimerspec64(&old_spec, old_setting))
+			error = -EFAULT;
+	}
+	return error;
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+SYSCALL_DEFINE4(timer_settime32, timer_t, timer_id, int, flags,
+		struct old_itimerspec32 __user *, new,
+		struct old_itimerspec32 __user *, old)
+{
+	struct itimerspec64 new_spec, old_spec;
+	struct itimerspec64 *rtn = old ? &old_spec : NULL;
+	int error = 0;
+
+	if (!new)
+		return -EINVAL;
+	if (get_old_itimerspec32(&new_spec, new))
+		return -EFAULT;
+
+	error = do_timer_settime(timer_id, flags, &new_spec, rtn);
+	if (!error && old) {
+		if (put_old_itimerspec32(&old_spec, old))
+			error = -EFAULT;
+	}
+	return error;
+}
+#endif
+
+int common_timer_del(struct k_itimer *timer)
+{
+	const struct k_clock *kc = timer->kclock;
+
+	timer->it_interval = 0;
+	if (kc->timer_try_to_cancel(timer) < 0)
+		return TIMER_RETRY;
+	timer->it_active = 0;
+	return 0;
+}
+
+static inline int timer_delete_hook(struct k_itimer *timer)
+{
+	const struct k_clock *kc = timer->kclock;
+
+	if (WARN_ON_ONCE(!kc || !kc->timer_del))
+		return -EINVAL;
+	return kc->timer_del(timer);
+}
+
+/* Delete a POSIX.1b interval timer. */
+SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)
+{
+	struct k_itimer *timer;
+	unsigned long flags;
+
+	timer = lock_timer(timer_id, &flags);
+
+retry_delete:
+	if (!timer)
+		return -EINVAL;
+
+	if (unlikely(timer_delete_hook(timer) == TIMER_RETRY)) {
+		/* Unlocks and relocks the timer if it still exists */
+		timer = timer_wait_running(timer, &flags);
+		goto retry_delete;
+	}
+
+	spin_lock(&current->sighand->siglock);
+	list_del(&timer->list);
+	spin_unlock(&current->sighand->siglock);
+	/*
+	 * A concurrent lookup could check timer::it_signal lockless. It
+	 * will reevaluate with timer::it_lock held and observe the NULL.
+	 */
+	WRITE_ONCE(timer->it_signal, NULL);
+
+	unlock_timer(timer, flags);
+	posix_timer_unhash_and_free(timer);
+	return 0;
+}
+
+/*
+ * Delete a timer if it is armed, remove it from the hash and schedule it
+ * for RCU freeing.
+ */
+static void itimer_delete(struct k_itimer *timer)
+{
+	unsigned long flags;
+
+	/*
+	 * irqsave is required to make timer_wait_running() work.
+	 */
+	spin_lock_irqsave(&timer->it_lock, flags);
+
+retry_delete:
+	/*
+	 * Even if the timer is not longer accessible from other tasks
+	 * it still might be armed and queued in the underlying timer
+	 * mechanism. Worse, that timer mechanism might run the expiry
+	 * function concurrently.
+	 */
+	if (timer_delete_hook(timer) == TIMER_RETRY) {
+		/*
+		 * Timer is expired concurrently, prevent livelocks
+		 * and pointless spinning on RT.
+		 *
+		 * timer_wait_running() drops timer::it_lock, which opens
+		 * the possibility for another task to delete the timer.
+		 *
+		 * That's not possible here because this is invoked from
+		 * do_exit() only for the last thread of the thread group.
+		 * So no other task can access and delete that timer.
+		 */
+		if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer))
+			return;
+
+		goto retry_delete;
+	}
+	list_del(&timer->list);
+
+	/*
+	 * Setting timer::it_signal to NULL is technically not required
+	 * here as nothing can access the timer anymore legitimately via
+	 * the hash table. Set it to NULL nevertheless so that all deletion
+	 * paths are consistent.
+	 */
+	WRITE_ONCE(timer->it_signal, NULL);
+
+	spin_unlock_irqrestore(&timer->it_lock, flags);
+	posix_timer_unhash_and_free(timer);
+}
+
+/*
+ * Invoked from do_exit() when the last thread of a thread group exits.
+ * At that point no other task can access the timers of the dying
+ * task anymore.
+ */
+void exit_itimers(struct task_struct *tsk)
+{
+	struct list_head timers;
+	struct k_itimer *tmr;
+
+	if (list_empty(&tsk->signal->posix_timers))
+		return;
+
+	/* Protect against concurrent read via /proc/$PID/timers */
+	spin_lock_irq(&tsk->sighand->siglock);
+	list_replace_init(&tsk->signal->posix_timers, &timers);
+	spin_unlock_irq(&tsk->sighand->siglock);
+
+	/* The timers are not longer accessible via tsk::signal */
+	while (!list_empty(&timers)) {
+		tmr = list_first_entry(&timers, struct k_itimer, list);
+		itimer_delete(tmr);
+	}
+}
+
+SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
+		const struct __kernel_timespec __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 new_tp;
+
+	if (!kc || !kc->clock_set)
+		return -EINVAL;
+
+	if (get_timespec64(&new_tp, tp))
+		return -EFAULT;
+
+	/*
+	 * Permission checks have to be done inside the clock specific
+	 * setter callback.
+	 */
+	return kc->clock_set(which_clock, &new_tp);
+}
+
+SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
+		struct __kernel_timespec __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 kernel_tp;
+	int error;
+
+	if (!kc)
+		return -EINVAL;
+
+	error = kc->clock_get_timespec(which_clock, &kernel_tp);
+
+	if (!error && put_timespec64(&kernel_tp, tp))
+		error = -EFAULT;
+
+	return error;
+}
+
+int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+
+	if (!kc)
+		return -EINVAL;
+	if (!kc->clock_adj)
+		return -EOPNOTSUPP;
+
+	return kc->clock_adj(which_clock, ktx);
+}
+
+SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
+		struct __kernel_timex __user *, utx)
+{
+	struct __kernel_timex ktx;
+	int err;
+
+	if (copy_from_user(&ktx, utx, sizeof(ktx)))
+		return -EFAULT;
+
+	err = do_clock_adjtime(which_clock, &ktx);
+
+	if (err >= 0 && copy_to_user(utx, &ktx, sizeof(ktx)))
+		return -EFAULT;
+
+	return err;
+}
+
+/**
+ * sys_clock_getres - Get the resolution of a clock
+ * @which_clock:	The clock to get the resolution for
+ * @tp:			Pointer to a a user space timespec64 for storage
+ *
+ * POSIX defines:
+ *
+ * "The clock_getres() function shall return the resolution of any
+ * clock. Clock resolutions are implementation-defined and cannot be set by
+ * a process. If the argument res is not NULL, the resolution of the
+ * specified clock shall be stored in the location pointed to by res. If
+ * res is NULL, the clock resolution is not returned. If the time argument
+ * of clock_settime() is not a multiple of res, then the value is truncated
+ * to a multiple of res."
+ *
+ * Due to the various hardware constraints the real resolution can vary
+ * wildly and even change during runtime when the underlying devices are
+ * replaced. The kernel also can use hardware devices with different
+ * resolutions for reading the time and for arming timers.
+ *
+ * The kernel therefore deviates from the POSIX spec in various aspects:
+ *
+ * 1) The resolution returned to user space
+ *
+ *    For CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_BOOTTIME, CLOCK_TAI,
+ *    CLOCK_REALTIME_ALARM, CLOCK_BOOTTIME_ALAREM and CLOCK_MONOTONIC_RAW
+ *    the kernel differentiates only two cases:
+ *
+ *    I)  Low resolution mode:
+ *
+ *	  When high resolution timers are disabled at compile or runtime
+ *	  the resolution returned is nanoseconds per tick, which represents
+ *	  the precision at which timers expire.
+ *
+ *    II) High resolution mode:
+ *
+ *	  When high resolution timers are enabled the resolution returned
+ *	  is always one nanosecond independent of the actual resolution of
+ *	  the underlying hardware devices.
+ *
+ *	  For CLOCK_*_ALARM the actual resolution depends on system
+ *	  state. When system is running the resolution is the same as the
+ *	  resolution of the other clocks. During suspend the actual
+ *	  resolution is the resolution of the underlying RTC device which
+ *	  might be way less precise than the clockevent device used during
+ *	  running state.
+ *
+ *   For CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE the resolution
+ *   returned is always nanoseconds per tick.
+ *
+ *   For CLOCK_PROCESS_CPUTIME and CLOCK_THREAD_CPUTIME the resolution
+ *   returned is always one nanosecond under the assumption that the
+ *   underlying scheduler clock has a better resolution than nanoseconds
+ *   per tick.
+ *
+ *   For dynamic POSIX clocks (PTP devices) the resolution returned is
+ *   always one nanosecond.
+ *
+ * 2) Affect on sys_clock_settime()
+ *
+ *    The kernel does not truncate the time which is handed in to
+ *    sys_clock_settime(). The kernel internal timekeeping is always using
+ *    nanoseconds precision independent of the clocksource device which is
+ *    used to read the time from. The resolution of that device only
+ *    affects the presicion of the time returned by sys_clock_gettime().
+ *
+ * Returns:
+ *	0		Success. @tp contains the resolution
+ *	-EINVAL		@which_clock is not a valid clock ID
+ *	-EFAULT		Copying the resolution to @tp faulted
+ *	-ENODEV		Dynamic POSIX clock is not backed by a device
+ *	-EOPNOTSUPP	Dynamic POSIX clock does not support getres()
+ */
+SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
+		struct __kernel_timespec __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 rtn_tp;
+	int error;
+
+	if (!kc)
+		return -EINVAL;
+
+	error = kc->clock_getres(which_clock, &rtn_tp);
+
+	if (!error && tp && put_timespec64(&rtn_tp, tp))
+		error = -EFAULT;
+
+	return error;
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+
+SYSCALL_DEFINE2(clock_settime32, clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 ts;
+
+	if (!kc || !kc->clock_set)
+		return -EINVAL;
+
+	if (get_old_timespec32(&ts, tp))
+		return -EFAULT;
+
+	return kc->clock_set(which_clock, &ts);
+}
+
+SYSCALL_DEFINE2(clock_gettime32, clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 ts;
+	int err;
+
+	if (!kc)
+		return -EINVAL;
+
+	err = kc->clock_get_timespec(which_clock, &ts);
+
+	if (!err && put_old_timespec32(&ts, tp))
+		err = -EFAULT;
+
+	return err;
+}
+
+SYSCALL_DEFINE2(clock_adjtime32, clockid_t, which_clock,
+		struct old_timex32 __user *, utp)
+{
+	struct __kernel_timex ktx;
+	int err;
+
+	err = get_old_timex32(&ktx, utp);
+	if (err)
+		return err;
+
+	err = do_clock_adjtime(which_clock, &ktx);
+
+	if (err >= 0 && put_old_timex32(utp, &ktx))
+		return -EFAULT;
+
+	return err;
+}
+
+SYSCALL_DEFINE2(clock_getres_time32, clockid_t, which_clock,
+		struct old_timespec32 __user *, tp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 ts;
+	int err;
+
+	if (!kc)
+		return -EINVAL;
+
+	err = kc->clock_getres(which_clock, &ts);
+	if (!err && tp && put_old_timespec32(&ts, tp))
+		return -EFAULT;
+
+	return err;
+}
+
+#endif
+
+/*
+ * sys_clock_nanosleep() for CLOCK_REALTIME and CLOCK_TAI
+ */
+static int common_nsleep(const clockid_t which_clock, int flags,
+			 const struct timespec64 *rqtp)
+{
+	ktime_t texp = timespec64_to_ktime(*rqtp);
+
+	return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
+				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+				 which_clock);
+}
+
+/*
+ * sys_clock_nanosleep() for CLOCK_MONOTONIC and CLOCK_BOOTTIME
+ *
+ * Absolute nanosleeps for these clocks are time-namespace adjusted.
+ */
+static int common_nsleep_timens(const clockid_t which_clock, int flags,
+				const struct timespec64 *rqtp)
+{
+	ktime_t texp = timespec64_to_ktime(*rqtp);
+
+	if (flags & TIMER_ABSTIME)
+		texp = timens_ktime_to_host(which_clock, texp);
+
+	return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
+				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+				 which_clock);
+}
+
+SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
+		const struct __kernel_timespec __user *, rqtp,
+		struct __kernel_timespec __user *, rmtp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 t;
+
+	if (!kc)
+		return -EINVAL;
+	if (!kc->nsleep)
+		return -EOPNOTSUPP;
+
+	if (get_timespec64(&t, rqtp))
+		return -EFAULT;
+
+	if (!timespec64_valid(&t))
+		return -EINVAL;
+	if (flags & TIMER_ABSTIME)
+		rmtp = NULL;
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
+	current->restart_block.nanosleep.rmtp = rmtp;
+
+	return kc->nsleep(which_clock, flags, &t);
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+
+SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags,
+		struct old_timespec32 __user *, rqtp,
+		struct old_timespec32 __user *, rmtp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timespec64 t;
+
+	if (!kc)
+		return -EINVAL;
+	if (!kc->nsleep)
+		return -EOPNOTSUPP;
+
+	if (get_old_timespec32(&t, rqtp))
+		return -EFAULT;
+
+	if (!timespec64_valid(&t))
+		return -EINVAL;
+	if (flags & TIMER_ABSTIME)
+		rmtp = NULL;
+	current->restart_block.fn = do_no_restart_syscall;
+	current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
+	current->restart_block.nanosleep.compat_rmtp = rmtp;
+
+	return kc->nsleep(which_clock, flags, &t);
+}
+
+#endif
+
+static const struct k_clock clock_realtime = {
+	.clock_getres		= posix_get_hrtimer_res,
+	.clock_get_timespec	= posix_get_realtime_timespec,
+	.clock_get_ktime	= posix_get_realtime_ktime,
+	.clock_set		= posix_clock_realtime_set,
+	.clock_adj		= posix_clock_realtime_adj,
+	.nsleep			= common_nsleep,
+	.timer_create		= common_timer_create,
+	.timer_set		= common_timer_set,
+	.timer_get		= common_timer_get,
+	.timer_del		= common_timer_del,
+	.timer_rearm		= common_hrtimer_rearm,
+	.timer_forward		= common_hrtimer_forward,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_wait_running	= common_timer_wait_running,
+	.timer_arm		= common_hrtimer_arm,
+};
+
+static const struct k_clock clock_monotonic = {
+	.clock_getres		= posix_get_hrtimer_res,
+	.clock_get_timespec	= posix_get_monotonic_timespec,
+	.clock_get_ktime	= posix_get_monotonic_ktime,
+	.nsleep			= common_nsleep_timens,
+	.timer_create		= common_timer_create,
+	.timer_set		= common_timer_set,
+	.timer_get		= common_timer_get,
+	.timer_del		= common_timer_del,
+	.timer_rearm		= common_hrtimer_rearm,
+	.timer_forward		= common_hrtimer_forward,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_wait_running	= common_timer_wait_running,
+	.timer_arm		= common_hrtimer_arm,
+};
+
+static const struct k_clock clock_monotonic_raw = {
+	.clock_getres		= posix_get_hrtimer_res,
+	.clock_get_timespec	= posix_get_monotonic_raw,
+};
+
+static const struct k_clock clock_realtime_coarse = {
+	.clock_getres		= posix_get_coarse_res,
+	.clock_get_timespec	= posix_get_realtime_coarse,
+};
+
+static const struct k_clock clock_monotonic_coarse = {
+	.clock_getres		= posix_get_coarse_res,
+	.clock_get_timespec	= posix_get_monotonic_coarse,
+};
+
+static const struct k_clock clock_tai = {
+	.clock_getres		= posix_get_hrtimer_res,
+	.clock_get_ktime	= posix_get_tai_ktime,
+	.clock_get_timespec	= posix_get_tai_timespec,
+	.nsleep			= common_nsleep,
+	.timer_create		= common_timer_create,
+	.timer_set		= common_timer_set,
+	.timer_get		= common_timer_get,
+	.timer_del		= common_timer_del,
+	.timer_rearm		= common_hrtimer_rearm,
+	.timer_forward		= common_hrtimer_forward,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_wait_running	= common_timer_wait_running,
+	.timer_arm		= common_hrtimer_arm,
+};
+
+static const struct k_clock clock_boottime = {
+	.clock_getres		= posix_get_hrtimer_res,
+	.clock_get_ktime	= posix_get_boottime_ktime,
+	.clock_get_timespec	= posix_get_boottime_timespec,
+	.nsleep			= common_nsleep_timens,
+	.timer_create		= common_timer_create,
+	.timer_set		= common_timer_set,
+	.timer_get		= common_timer_get,
+	.timer_del		= common_timer_del,
+	.timer_rearm		= common_hrtimer_rearm,
+	.timer_forward		= common_hrtimer_forward,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_wait_running	= common_timer_wait_running,
+	.timer_arm		= common_hrtimer_arm,
+};
+
+static const struct k_clock * const posix_clocks[] = {
+	[CLOCK_REALTIME]		= &clock_realtime,
+	[CLOCK_MONOTONIC]		= &clock_monotonic,
+	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
+	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
+	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
+	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
+	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
+	[CLOCK_BOOTTIME]		= &clock_boottime,
+	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
+	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
+	[CLOCK_TAI]			= &clock_tai,
+};
+
+static const struct k_clock *clockid_to_kclock(const clockid_t id)
+{
+	clockid_t idx = id;
+
+	if (id < 0) {
+		return (id & CLOCKFD_MASK) == CLOCKFD ?
+			&clock_posix_dynamic : &clock_posix_cpu;
+	}
+
+	if (id >= ARRAY_SIZE(posix_clocks))
+		return NULL;
+
+	return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
+}
diff --git a/kernel/time/posix-timers.h b/kernel/time/posix-timers.h
new file mode 100644
index 0000000000..f32a2ebba9
--- /dev/null
+++ b/kernel/time/posix-timers.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#define TIMER_RETRY 1
+
+struct k_clock {
+	int	(*clock_getres)(const clockid_t which_clock,
+				struct timespec64 *tp);
+	int	(*clock_set)(const clockid_t which_clock,
+			     const struct timespec64 *tp);
+	/* Returns the clock value in the current time namespace. */
+	int	(*clock_get_timespec)(const clockid_t which_clock,
+				      struct timespec64 *tp);
+	/* Returns the clock value in the root time namespace. */
+	ktime_t	(*clock_get_ktime)(const clockid_t which_clock);
+	int	(*clock_adj)(const clockid_t which_clock, struct __kernel_timex *tx);
+	int	(*timer_create)(struct k_itimer *timer);
+	int	(*nsleep)(const clockid_t which_clock, int flags,
+			  const struct timespec64 *);
+	int	(*timer_set)(struct k_itimer *timr, int flags,
+			     struct itimerspec64 *new_setting,
+			     struct itimerspec64 *old_setting);
+	int	(*timer_del)(struct k_itimer *timr);
+	void	(*timer_get)(struct k_itimer *timr,
+			     struct itimerspec64 *cur_setting);
+	void	(*timer_rearm)(struct k_itimer *timr);
+	s64	(*timer_forward)(struct k_itimer *timr, ktime_t now);
+	ktime_t	(*timer_remaining)(struct k_itimer *timr, ktime_t now);
+	int	(*timer_try_to_cancel)(struct k_itimer *timr);
+	void	(*timer_arm)(struct k_itimer *timr, ktime_t expires,
+			     bool absolute, bool sigev_none);
+	void	(*timer_wait_running)(struct k_itimer *timr);
+};
+
+extern const struct k_clock clock_posix_cpu;
+extern const struct k_clock clock_posix_dynamic;
+extern const struct k_clock clock_process;
+extern const struct k_clock clock_thread;
+extern const struct k_clock alarm_clock;
+
+int posix_timer_event(struct k_itimer *timr, int si_private);
+
+void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting);
+int common_timer_set(struct k_itimer *timr, int flags,
+		     struct itimerspec64 *new_setting,
+		     struct itimerspec64 *old_setting);
+int common_timer_del(struct k_itimer *timer);
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
new file mode 100644
index 0000000000..68d6c1190a
--- /dev/null
+++ b/kernel/time/sched_clock.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic sched_clock() support, to extend low level hardware time
+ * counters to full 64-bit ns values.
+ */
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/ktime.h>
+#include <linux/kernel.h>
+#include <linux/math.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/syscore_ops.h>
+#include <linux/hrtimer.h>
+#include <linux/sched_clock.h>
+#include <linux/seqlock.h>
+#include <linux/bitops.h>
+
+#include "timekeeping.h"
+
+/**
+ * struct clock_data - all data needed for sched_clock() (including
+ *                     registration of a new clock source)
+ *
+ * @seq:		Sequence counter for protecting updates. The lowest
+ *			bit is the index for @read_data.
+ * @read_data:		Data required to read from sched_clock.
+ * @wrap_kt:		Duration for which clock can run before wrapping.
+ * @rate:		Tick rate of the registered clock.
+ * @actual_read_sched_clock: Registered hardware level clock read function.
+ *
+ * The ordering of this structure has been chosen to optimize cache
+ * performance. In particular 'seq' and 'read_data[0]' (combined) should fit
+ * into a single 64-byte cache line.
+ */
+struct clock_data {
+	seqcount_latch_t	seq;
+	struct clock_read_data	read_data[2];
+	ktime_t			wrap_kt;
+	unsigned long		rate;
+
+	u64 (*actual_read_sched_clock)(void);
+};
+
+static struct hrtimer sched_clock_timer;
+static int irqtime = -1;
+
+core_param(irqtime, irqtime, int, 0400);
+
+static u64 notrace jiffy_sched_clock_read(void)
+{
+	/*
+	 * We don't need to use get_jiffies_64 on 32-bit arches here
+	 * because we register with BITS_PER_LONG
+	 */
+	return (u64)(jiffies - INITIAL_JIFFIES);
+}
+
+static struct clock_data cd ____cacheline_aligned = {
+	.read_data[0] = { .mult = NSEC_PER_SEC / HZ,
+			  .read_sched_clock = jiffy_sched_clock_read, },
+	.actual_read_sched_clock = jiffy_sched_clock_read,
+};
+
+static __always_inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
+{
+	return (cyc * mult) >> shift;
+}
+
+notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
+{
+	*seq = raw_read_seqcount_latch(&cd.seq);
+	return cd.read_data + (*seq & 1);
+}
+
+notrace int sched_clock_read_retry(unsigned int seq)
+{
+	return raw_read_seqcount_latch_retry(&cd.seq, seq);
+}
+
+unsigned long long noinstr sched_clock_noinstr(void)
+{
+	struct clock_read_data *rd;
+	unsigned int seq;
+	u64 cyc, res;
+
+	do {
+		seq = raw_read_seqcount_latch(&cd.seq);
+		rd = cd.read_data + (seq & 1);
+
+		cyc = (rd->read_sched_clock() - rd->epoch_cyc) &
+		      rd->sched_clock_mask;
+		res = rd->epoch_ns + cyc_to_ns(cyc, rd->mult, rd->shift);
+	} while (raw_read_seqcount_latch_retry(&cd.seq, seq));
+
+	return res;
+}
+
+unsigned long long notrace sched_clock(void)
+{
+	unsigned long long ns;
+	preempt_disable_notrace();
+	ns = sched_clock_noinstr();
+	preempt_enable_notrace();
+	return ns;
+}
+
+/*
+ * Updating the data required to read the clock.
+ *
+ * sched_clock() will never observe mis-matched data even if called from
+ * an NMI. We do this by maintaining an odd/even copy of the data and
+ * steering sched_clock() to one or the other using a sequence counter.
+ * In order to preserve the data cache profile of sched_clock() as much
+ * as possible the system reverts back to the even copy when the update
+ * completes; the odd copy is used *only* during an update.
+ */
+static void update_clock_read_data(struct clock_read_data *rd)
+{
+	/* update the backup (odd) copy with the new data */
+	cd.read_data[1] = *rd;
+
+	/* steer readers towards the odd copy */
+	raw_write_seqcount_latch(&cd.seq);
+
+	/* now its safe for us to update the normal (even) copy */
+	cd.read_data[0] = *rd;
+
+	/* switch readers back to the even copy */
+	raw_write_seqcount_latch(&cd.seq);
+}
+
+/*
+ * Atomically update the sched_clock() epoch.
+ */
+static void update_sched_clock(void)
+{
+	u64 cyc;
+	u64 ns;
+	struct clock_read_data rd;
+
+	rd = cd.read_data[0];
+
+	cyc = cd.actual_read_sched_clock();
+	ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
+
+	rd.epoch_ns = ns;
+	rd.epoch_cyc = cyc;
+
+	update_clock_read_data(&rd);
+}
+
+static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
+{
+	update_sched_clock();
+	hrtimer_forward_now(hrt, cd.wrap_kt);
+
+	return HRTIMER_RESTART;
+}
+
+void __init
+sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
+{
+	u64 res, wrap, new_mask, new_epoch, cyc, ns;
+	u32 new_mult, new_shift;
+	unsigned long r, flags;
+	char r_unit;
+	struct clock_read_data rd;
+
+	if (cd.rate > rate)
+		return;
+
+	/* Cannot register a sched_clock with interrupts on */
+	local_irq_save(flags);
+
+	/* Calculate the mult/shift to convert counter ticks to ns. */
+	clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
+
+	new_mask = CLOCKSOURCE_MASK(bits);
+	cd.rate = rate;
+
+	/* Calculate how many nanosecs until we risk wrapping */
+	wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL);
+	cd.wrap_kt = ns_to_ktime(wrap);
+
+	rd = cd.read_data[0];
+
+	/* Update epoch for new counter and update 'epoch_ns' from old counter*/
+	new_epoch = read();
+	cyc = cd.actual_read_sched_clock();
+	ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
+	cd.actual_read_sched_clock = read;
+
+	rd.read_sched_clock	= read;
+	rd.sched_clock_mask	= new_mask;
+	rd.mult			= new_mult;
+	rd.shift		= new_shift;
+	rd.epoch_cyc		= new_epoch;
+	rd.epoch_ns		= ns;
+
+	update_clock_read_data(&rd);
+
+	if (sched_clock_timer.function != NULL) {
+		/* update timeout for clock wrap */
+		hrtimer_start(&sched_clock_timer, cd.wrap_kt,
+			      HRTIMER_MODE_REL_HARD);
+	}
+
+	r = rate;
+	if (r >= 4000000) {
+		r = DIV_ROUND_CLOSEST(r, 1000000);
+		r_unit = 'M';
+	} else if (r >= 4000) {
+		r = DIV_ROUND_CLOSEST(r, 1000);
+		r_unit = 'k';
+	} else {
+		r_unit = ' ';
+	}
+
+	/* Calculate the ns resolution of this counter */
+	res = cyc_to_ns(1ULL, new_mult, new_shift);
+
+	pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",
+		bits, r, r_unit, res, wrap);
+
+	/* Enable IRQ time accounting if we have a fast enough sched_clock() */
+	if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
+		enable_sched_clock_irqtime();
+
+	local_irq_restore(flags);
+
+	pr_debug("Registered %pS as sched_clock source\n", read);
+}
+
+void __init generic_sched_clock_init(void)
+{
+	/*
+	 * If no sched_clock() function has been provided at that point,
+	 * make it the final one.
+	 */
+	if (cd.actual_read_sched_clock == jiffy_sched_clock_read)
+		sched_clock_register(jiffy_sched_clock_read, BITS_PER_LONG, HZ);
+
+	update_sched_clock();
+
+	/*
+	 * Start the timer to keep sched_clock() properly updated and
+	 * sets the initial epoch.
+	 */
+	hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
+	sched_clock_timer.function = sched_clock_poll;
+	hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL_HARD);
+}
+
+/*
+ * Clock read function for use when the clock is suspended.
+ *
+ * This function makes it appear to sched_clock() as if the clock
+ * stopped counting at its last update.
+ *
+ * This function must only be called from the critical
+ * section in sched_clock(). It relies on the read_seqcount_retry()
+ * at the end of the critical section to be sure we observe the
+ * correct copy of 'epoch_cyc'.
+ */
+static u64 notrace suspended_sched_clock_read(void)
+{
+	unsigned int seq = raw_read_seqcount_latch(&cd.seq);
+
+	return cd.read_data[seq & 1].epoch_cyc;
+}
+
+int sched_clock_suspend(void)
+{
+	struct clock_read_data *rd = &cd.read_data[0];
+
+	update_sched_clock();
+	hrtimer_cancel(&sched_clock_timer);
+	rd->read_sched_clock = suspended_sched_clock_read;
+
+	return 0;
+}
+
+void sched_clock_resume(void)
+{
+	struct clock_read_data *rd = &cd.read_data[0];
+
+	rd->epoch_cyc = cd.actual_read_sched_clock();
+	hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL_HARD);
+	rd->read_sched_clock = cd.actual_read_sched_clock;
+}
+
+static struct syscore_ops sched_clock_ops = {
+	.suspend	= sched_clock_suspend,
+	.resume		= sched_clock_resume,
+};
+
+static int __init sched_clock_syscore_init(void)
+{
+	register_syscore_ops(&sched_clock_ops);
+
+	return 0;
+}
+device_initcall(sched_clock_syscore_init);
diff --git a/kernel/time/test_udelay.c b/kernel/time/test_udelay.c
new file mode 100644
index 0000000000..20d5df6315
--- /dev/null
+++ b/kernel/time/test_udelay.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * udelay() test kernel module
+ *
+ * Test is executed by writing and reading to /sys/kernel/debug/udelay_test
+ * Tests are configured by writing: USECS ITERATIONS
+ * Tests are executed by reading from the same file.
+ * Specifying usecs of 0 or negative values will run multiples tests.
+ *
+ * Copyright (C) 2014 Google, Inc.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+#define DEFAULT_ITERATIONS 100
+
+#define DEBUGFS_FILENAME "udelay_test"
+
+static DEFINE_MUTEX(udelay_test_lock);
+static int udelay_test_usecs;
+static int udelay_test_iterations = DEFAULT_ITERATIONS;
+
+static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters)
+{
+	int min = 0, max = 0, fail_count = 0;
+	uint64_t sum = 0;
+	uint64_t avg;
+	int i;
+	/* Allow udelay to be up to 0.5% fast */
+	int allowed_error_ns = usecs * 5;
+
+	for (i = 0; i < iters; ++i) {
+		s64 kt1, kt2;
+		int time_passed;
+
+		kt1 = ktime_get_ns();
+		udelay(usecs);
+		kt2 = ktime_get_ns();
+		time_passed = kt2 - kt1;
+
+		if (i == 0 || time_passed < min)
+			min = time_passed;
+		if (i == 0 || time_passed > max)
+			max = time_passed;
+		if ((time_passed + allowed_error_ns) / 1000 < usecs)
+			++fail_count;
+		WARN_ON(time_passed < 0);
+		sum += time_passed;
+	}
+
+	avg = sum;
+	do_div(avg, iters);
+	seq_printf(s, "%d usecs x %d: exp=%d allowed=%d min=%d avg=%lld max=%d",
+			usecs, iters, usecs * 1000,
+			(usecs * 1000) - allowed_error_ns, min, avg, max);
+	if (fail_count)
+		seq_printf(s, " FAIL=%d", fail_count);
+	seq_puts(s, "\n");
+
+	return 0;
+}
+
+static int udelay_test_show(struct seq_file *s, void *v)
+{
+	int usecs;
+	int iters;
+	int ret = 0;
+
+	mutex_lock(&udelay_test_lock);
+	usecs = udelay_test_usecs;
+	iters = udelay_test_iterations;
+	mutex_unlock(&udelay_test_lock);
+
+	if (usecs > 0 && iters > 0) {
+		return udelay_test_single(s, usecs, iters);
+	} else if (usecs == 0) {
+		struct timespec64 ts;
+
+		ktime_get_ts64(&ts);
+		seq_printf(s, "udelay() test (lpj=%ld kt=%lld.%09ld)\n",
+				loops_per_jiffy, (s64)ts.tv_sec, ts.tv_nsec);
+		seq_puts(s, "usage:\n");
+		seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n");
+		seq_puts(s, "cat " DEBUGFS_FILENAME "\n");
+	}
+
+	return ret;
+}
+
+static int udelay_test_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, udelay_test_show, inode->i_private);
+}
+
+static ssize_t udelay_test_write(struct file *file, const char __user *buf,
+		size_t count, loff_t *pos)
+{
+	char lbuf[32];
+	int ret;
+	int usecs;
+	int iters;
+
+	if (count >= sizeof(lbuf))
+		return -EINVAL;
+
+	if (copy_from_user(lbuf, buf, count))
+		return -EFAULT;
+	lbuf[count] = '\0';
+
+	ret = sscanf(lbuf, "%d %d", &usecs, &iters);
+	if (ret < 1)
+		return -EINVAL;
+	else if (ret < 2)
+		iters = DEFAULT_ITERATIONS;
+
+	mutex_lock(&udelay_test_lock);
+	udelay_test_usecs = usecs;
+	udelay_test_iterations = iters;
+	mutex_unlock(&udelay_test_lock);
+
+	return count;
+}
+
+static const struct file_operations udelay_test_debugfs_ops = {
+	.owner = THIS_MODULE,
+	.open = udelay_test_open,
+	.read = seq_read,
+	.write = udelay_test_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static int __init udelay_test_init(void)
+{
+	mutex_lock(&udelay_test_lock);
+	debugfs_create_file(DEBUGFS_FILENAME, S_IRUSR, NULL, NULL,
+			    &udelay_test_debugfs_ops);
+	mutex_unlock(&udelay_test_lock);
+
+	return 0;
+}
+
+module_init(udelay_test_init);
+
+static void __exit udelay_test_exit(void)
+{
+	mutex_lock(&udelay_test_lock);
+	debugfs_lookup_and_remove(DEBUGFS_FILENAME, NULL);
+	mutex_unlock(&udelay_test_lock);
+}
+
+module_exit(udelay_test_exit);
+
+MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
+MODULE_LICENSE("GPL");
diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c
new file mode 100644
index 0000000000..e28f9210f8
--- /dev/null
+++ b/kernel/time/tick-broadcast-hrtimer.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Emulate a local clock event device via a pseudo clock device.
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/clockchips.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/module.h>
+
+#include "tick-internal.h"
+
+static struct hrtimer bctimer;
+
+static int bc_shutdown(struct clock_event_device *evt)
+{
+	/*
+	 * Note, we cannot cancel the timer here as we might
+	 * run into the following live lock scenario:
+	 *
+	 * cpu 0		cpu1
+	 * lock(broadcast_lock);
+	 *			hrtimer_interrupt()
+	 *			bc_handler()
+	 *			   tick_handle_oneshot_broadcast();
+	 *			    lock(broadcast_lock);
+	 * hrtimer_cancel()
+	 *  wait_for_callback()
+	 */
+	hrtimer_try_to_cancel(&bctimer);
+	return 0;
+}
+
+/*
+ * This is called from the guts of the broadcast code when the cpu
+ * which is about to enter idle has the earliest broadcast timer event.
+ */
+static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
+{
+	/*
+	 * This is called either from enter/exit idle code or from the
+	 * broadcast handler. In all cases tick_broadcast_lock is held.
+	 *
+	 * hrtimer_cancel() cannot be called here neither from the
+	 * broadcast handler nor from the enter/exit idle code. The idle
+	 * code can run into the problem described in bc_shutdown() and the
+	 * broadcast handler cannot wait for itself to complete for obvious
+	 * reasons.
+	 *
+	 * Each caller tries to arm the hrtimer on its own CPU, but if the
+	 * hrtimer callback function is currently running, then
+	 * hrtimer_start() cannot move it and the timer stays on the CPU on
+	 * which it is assigned at the moment.
+	 */
+	hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED_HARD);
+	/*
+	 * The core tick broadcast mode expects bc->bound_on to be set
+	 * correctly to prevent a CPU which has the broadcast hrtimer
+	 * armed from going deep idle.
+	 *
+	 * As tick_broadcast_lock is held, nothing can change the cpu
+	 * base which was just established in hrtimer_start() above. So
+	 * the below access is safe even without holding the hrtimer
+	 * base lock.
+	 */
+	bc->bound_on = bctimer.base->cpu_base->cpu;
+
+	return 0;
+}
+
+static struct clock_event_device ce_broadcast_hrtimer = {
+	.name			= "bc_hrtimer",
+	.set_state_shutdown	= bc_shutdown,
+	.set_next_ktime		= bc_set_next,
+	.features		= CLOCK_EVT_FEAT_ONESHOT |
+				  CLOCK_EVT_FEAT_KTIME |
+				  CLOCK_EVT_FEAT_HRTIMER,
+	.rating			= 0,
+	.bound_on		= -1,
+	.min_delta_ns		= 1,
+	.max_delta_ns		= KTIME_MAX,
+	.min_delta_ticks	= 1,
+	.max_delta_ticks	= ULONG_MAX,
+	.mult			= 1,
+	.shift			= 0,
+	.cpumask		= cpu_possible_mask,
+};
+
+static enum hrtimer_restart bc_handler(struct hrtimer *t)
+{
+	ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);
+
+	return HRTIMER_NORESTART;
+}
+
+void tick_setup_hrtimer_broadcast(void)
+{
+	hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
+	bctimer.function = bc_handler;
+	clockevents_register_device(&ce_broadcast_hrtimer);
+}
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
new file mode 100644
index 0000000000..771d1e0403
--- /dev/null
+++ b/kernel/time/tick-broadcast.c
@@ -0,0 +1,1215 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file contains functions which emulate a local clock-event
+ * device via a broadcast event source.
+ *
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/module.h>
+
+#include "tick-internal.h"
+
+/*
+ * Broadcast support for broken x86 hardware, where the local apic
+ * timer stops in C3 state.
+ */
+
+static struct tick_device tick_broadcast_device;
+static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
+static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
+static cpumask_var_t tmpmask __cpumask_var_read_mostly;
+static int tick_broadcast_forced;
+
+static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
+
+#ifdef CONFIG_TICK_ONESHOT
+static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
+
+static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);
+static void tick_broadcast_clear_oneshot(int cpu);
+static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
+# ifdef CONFIG_HOTPLUG_CPU
+static void tick_broadcast_oneshot_offline(unsigned int cpu);
+# endif
+#else
+static inline void
+tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
+static inline void tick_broadcast_clear_oneshot(int cpu) { }
+static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
+# ifdef CONFIG_HOTPLUG_CPU
+static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
+# endif
+#endif
+
+/*
+ * Debugging: see timer_list.c
+ */
+struct tick_device *tick_get_broadcast_device(void)
+{
+	return &tick_broadcast_device;
+}
+
+struct cpumask *tick_get_broadcast_mask(void)
+{
+	return tick_broadcast_mask;
+}
+
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
+
+const struct clock_event_device *tick_get_wakeup_device(int cpu)
+{
+	return tick_get_oneshot_wakeup_device(cpu);
+}
+
+/*
+ * Start the device in periodic mode
+ */
+static void tick_broadcast_start_periodic(struct clock_event_device *bc)
+{
+	if (bc)
+		tick_setup_periodic(bc, 1);
+}
+
+/*
+ * Check, if the device can be utilized as broadcast device:
+ */
+static bool tick_check_broadcast_device(struct clock_event_device *curdev,
+					struct clock_event_device *newdev)
+{
+	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
+	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
+	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
+		return false;
+
+	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
+	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return false;
+
+	return !curdev || newdev->rating > curdev->rating;
+}
+
+#ifdef CONFIG_TICK_ONESHOT
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+	return per_cpu(tick_oneshot_wakeup_device, cpu);
+}
+
+static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
+{
+	/*
+	 * If we woke up early and the tick was reprogrammed in the
+	 * meantime then this may be spurious but harmless.
+	 */
+	tick_receive_broadcast();
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+					   int cpu)
+{
+	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
+
+	if (!newdev)
+		goto set_device;
+
+	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
+	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
+		 return false;
+
+	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
+	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return false;
+
+	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
+		return false;
+
+	if (curdev && newdev->rating <= curdev->rating)
+		return false;
+
+	if (!try_module_get(newdev->owner))
+		return false;
+
+	newdev->event_handler = tick_oneshot_wakeup_handler;
+set_device:
+	clockevents_exchange_device(curdev, newdev);
+	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
+	return true;
+}
+#else
+static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
+{
+	return NULL;
+}
+
+static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
+					   int cpu)
+{
+	return false;
+}
+#endif
+
+/*
+ * Conditionally install/replace broadcast device
+ */
+void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
+{
+	struct clock_event_device *cur = tick_broadcast_device.evtdev;
+
+	if (tick_set_oneshot_wakeup_device(dev, cpu))
+		return;
+
+	if (!tick_check_broadcast_device(cur, dev))
+		return;
+
+	if (!try_module_get(dev->owner))
+		return;
+
+	clockevents_exchange_device(cur, dev);
+	if (cur)
+		cur->event_handler = clockevents_handle_noop;
+	tick_broadcast_device.evtdev = dev;
+	if (!cpumask_empty(tick_broadcast_mask))
+		tick_broadcast_start_periodic(dev);
+
+	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return;
+
+	/*
+	 * If the system already runs in oneshot mode, switch the newly
+	 * registered broadcast device to oneshot mode explicitly.
+	 */
+	if (tick_broadcast_oneshot_active()) {
+		tick_broadcast_switch_to_oneshot();
+		return;
+	}
+
+	/*
+	 * Inform all cpus about this. We might be in a situation
+	 * where we did not switch to oneshot mode because the per cpu
+	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
+	 * of a oneshot capable broadcast device. Without that
+	 * notification the systems stays stuck in periodic mode
+	 * forever.
+	 */
+	tick_clock_notify();
+}
+
+/*
+ * Check, if the device is the broadcast device
+ */
+int tick_is_broadcast_device(struct clock_event_device *dev)
+{
+	return (dev && tick_broadcast_device.evtdev == dev);
+}
+
+int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
+{
+	int ret = -ENODEV;
+
+	if (tick_is_broadcast_device(dev)) {
+		raw_spin_lock(&tick_broadcast_lock);
+		ret = __clockevents_update_freq(dev, freq);
+		raw_spin_unlock(&tick_broadcast_lock);
+	}
+	return ret;
+}
+
+
+static void err_broadcast(const struct cpumask *mask)
+{
+	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
+}
+
+static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
+{
+	if (!dev->broadcast)
+		dev->broadcast = tick_broadcast;
+	if (!dev->broadcast) {
+		pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
+			     dev->name);
+		dev->broadcast = err_broadcast;
+	}
+}
+
+/*
+ * Check, if the device is dysfunctional and a placeholder, which
+ * needs to be handled by the broadcast device.
+ */
+int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
+{
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
+	unsigned long flags;
+	int ret = 0;
+
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	/*
+	 * Devices might be registered with both periodic and oneshot
+	 * mode disabled. This signals, that the device needs to be
+	 * operated from the broadcast device and is a placeholder for
+	 * the cpu local device.
+	 */
+	if (!tick_device_is_functional(dev)) {
+		dev->event_handler = tick_handle_periodic;
+		tick_device_setup_broadcast_func(dev);
+		cpumask_set_cpu(cpu, tick_broadcast_mask);
+		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+			tick_broadcast_start_periodic(bc);
+		else
+			tick_broadcast_setup_oneshot(bc, false);
+		ret = 1;
+	} else {
+		/*
+		 * Clear the broadcast bit for this cpu if the
+		 * device is not power state affected.
+		 */
+		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+			cpumask_clear_cpu(cpu, tick_broadcast_mask);
+		else
+			tick_device_setup_broadcast_func(dev);
+
+		/*
+		 * Clear the broadcast bit if the CPU is not in
+		 * periodic broadcast on state.
+		 */
+		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
+			cpumask_clear_cpu(cpu, tick_broadcast_mask);
+
+		switch (tick_broadcast_device.mode) {
+		case TICKDEV_MODE_ONESHOT:
+			/*
+			 * If the system is in oneshot mode we can
+			 * unconditionally clear the oneshot mask bit,
+			 * because the CPU is running and therefore
+			 * not in an idle state which causes the power
+			 * state affected device to stop. Let the
+			 * caller initialize the device.
+			 */
+			tick_broadcast_clear_oneshot(cpu);
+			ret = 0;
+			break;
+
+		case TICKDEV_MODE_PERIODIC:
+			/*
+			 * If the system is in periodic mode, check
+			 * whether the broadcast device can be
+			 * switched off now.
+			 */
+			if (cpumask_empty(tick_broadcast_mask) && bc)
+				clockevents_shutdown(bc);
+			/*
+			 * If we kept the cpu in the broadcast mask,
+			 * tell the caller to leave the per cpu device
+			 * in shutdown state. The periodic interrupt
+			 * is delivered by the broadcast device, if
+			 * the broadcast device exists and is not
+			 * hrtimer based.
+			 */
+			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
+				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
+			break;
+		default:
+			break;
+		}
+	}
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+	return ret;
+}
+
+int tick_receive_broadcast(void)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	struct clock_event_device *evt = td->evtdev;
+
+	if (!evt)
+		return -ENODEV;
+
+	if (!evt->event_handler)
+		return -EINVAL;
+
+	evt->event_handler(evt);
+	return 0;
+}
+
+/*
+ * Broadcast the event to the cpus, which are set in the mask (mangled).
+ */
+static bool tick_do_broadcast(struct cpumask *mask)
+{
+	int cpu = smp_processor_id();
+	struct tick_device *td;
+	bool local = false;
+
+	/*
+	 * Check, if the current cpu is in the mask
+	 */
+	if (cpumask_test_cpu(cpu, mask)) {
+		struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+		cpumask_clear_cpu(cpu, mask);
+		/*
+		 * We only run the local handler, if the broadcast
+		 * device is not hrtimer based. Otherwise we run into
+		 * a hrtimer recursion.
+		 *
+		 * local timer_interrupt()
+		 *   local_handler()
+		 *     expire_hrtimers()
+		 *       bc_handler()
+		 *         local_handler()
+		 *	     expire_hrtimers()
+		 */
+		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
+	}
+
+	if (!cpumask_empty(mask)) {
+		/*
+		 * It might be necessary to actually check whether the devices
+		 * have different broadcast functions. For now, just use the
+		 * one of the first device. This works as long as we have this
+		 * misfeature only on x86 (lapic)
+		 */
+		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
+		td->evtdev->broadcast(mask);
+	}
+	return local;
+}
+
+/*
+ * Periodic broadcast:
+ * - invoke the broadcast handlers
+ */
+static bool tick_do_periodic_broadcast(void)
+{
+	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
+	return tick_do_broadcast(tmpmask);
+}
+
+/*
+ * Event handler for periodic broadcast ticks
+ */
+static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	bool bc_local;
+
+	raw_spin_lock(&tick_broadcast_lock);
+
+	/* Handle spurious interrupts gracefully */
+	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
+		raw_spin_unlock(&tick_broadcast_lock);
+		return;
+	}
+
+	bc_local = tick_do_periodic_broadcast();
+
+	if (clockevent_state_oneshot(dev)) {
+		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
+
+		clockevents_program_event(dev, next, true);
+	}
+	raw_spin_unlock(&tick_broadcast_lock);
+
+	/*
+	 * We run the handler of the local cpu after dropping
+	 * tick_broadcast_lock because the handler might deadlock when
+	 * trying to switch to oneshot mode.
+	 */
+	if (bc_local)
+		td->evtdev->event_handler(td->evtdev);
+}
+
+/**
+ * tick_broadcast_control - Enable/disable or force broadcast mode
+ * @mode:	The selected broadcast mode
+ *
+ * Called when the system enters a state where affected tick devices
+ * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
+ */
+void tick_broadcast_control(enum tick_broadcast_mode mode)
+{
+	struct clock_event_device *bc, *dev;
+	struct tick_device *td;
+	int cpu, bc_stopped;
+	unsigned long flags;
+
+	/* Protects also the local clockevent device. */
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+	td = this_cpu_ptr(&tick_cpu_device);
+	dev = td->evtdev;
+
+	/*
+	 * Is the device not affected by the powerstate ?
+	 */
+	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
+		goto out;
+
+	if (!tick_device_is_functional(dev))
+		goto out;
+
+	cpu = smp_processor_id();
+	bc = tick_broadcast_device.evtdev;
+	bc_stopped = cpumask_empty(tick_broadcast_mask);
+
+	switch (mode) {
+	case TICK_BROADCAST_FORCE:
+		tick_broadcast_forced = 1;
+		fallthrough;
+	case TICK_BROADCAST_ON:
+		cpumask_set_cpu(cpu, tick_broadcast_on);
+		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
+			/*
+			 * Only shutdown the cpu local device, if:
+			 *
+			 * - the broadcast device exists
+			 * - the broadcast device is not a hrtimer based one
+			 * - the broadcast device is in periodic mode to
+			 *   avoid a hiccup during switch to oneshot mode
+			 */
+			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
+			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+				clockevents_shutdown(dev);
+		}
+		break;
+
+	case TICK_BROADCAST_OFF:
+		if (tick_broadcast_forced)
+			break;
+		cpumask_clear_cpu(cpu, tick_broadcast_on);
+		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
+			if (tick_broadcast_device.mode ==
+			    TICKDEV_MODE_PERIODIC)
+				tick_setup_periodic(dev, 0);
+		}
+		break;
+	}
+
+	if (bc) {
+		if (cpumask_empty(tick_broadcast_mask)) {
+			if (!bc_stopped)
+				clockevents_shutdown(bc);
+		} else if (bc_stopped) {
+			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+				tick_broadcast_start_periodic(bc);
+			else
+				tick_broadcast_setup_oneshot(bc, false);
+		}
+	}
+out:
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+EXPORT_SYMBOL_GPL(tick_broadcast_control);
+
+/*
+ * Set the periodic handler depending on broadcast on/off
+ */
+void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
+{
+	if (!broadcast)
+		dev->event_handler = tick_handle_periodic;
+	else
+		dev->event_handler = tick_handle_periodic_broadcast;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void tick_shutdown_broadcast(void)
+{
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
+		if (bc && cpumask_empty(tick_broadcast_mask))
+			clockevents_shutdown(bc);
+	}
+}
+
+/*
+ * Remove a CPU from broadcasting
+ */
+void tick_broadcast_offline(unsigned int cpu)
+{
+	raw_spin_lock(&tick_broadcast_lock);
+	cpumask_clear_cpu(cpu, tick_broadcast_mask);
+	cpumask_clear_cpu(cpu, tick_broadcast_on);
+	tick_broadcast_oneshot_offline(cpu);
+	tick_shutdown_broadcast();
+	raw_spin_unlock(&tick_broadcast_lock);
+}
+
+#endif
+
+void tick_suspend_broadcast(void)
+{
+	struct clock_event_device *bc;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	bc = tick_broadcast_device.evtdev;
+	if (bc)
+		clockevents_shutdown(bc);
+
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+
+/*
+ * This is called from tick_resume_local() on a resuming CPU. That's
+ * called from the core resume function, tick_unfreeze() and the magic XEN
+ * resume hackery.
+ *
+ * In none of these cases the broadcast device mode can change and the
+ * bit of the resuming CPU in the broadcast mask is safe as well.
+ */
+bool tick_resume_check_broadcast(void)
+{
+	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
+		return false;
+	else
+		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
+}
+
+void tick_resume_broadcast(void)
+{
+	struct clock_event_device *bc;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	bc = tick_broadcast_device.evtdev;
+
+	if (bc) {
+		clockevents_tick_resume(bc);
+
+		switch (tick_broadcast_device.mode) {
+		case TICKDEV_MODE_PERIODIC:
+			if (!cpumask_empty(tick_broadcast_mask))
+				tick_broadcast_start_periodic(bc);
+			break;
+		case TICKDEV_MODE_ONESHOT:
+			if (!cpumask_empty(tick_broadcast_mask))
+				tick_resume_broadcast_oneshot(bc);
+			break;
+		}
+	}
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+
+#ifdef CONFIG_TICK_ONESHOT
+
+static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
+static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
+static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
+
+/*
+ * Exposed for debugging: see timer_list.c
+ */
+struct cpumask *tick_get_broadcast_oneshot_mask(void)
+{
+	return tick_broadcast_oneshot_mask;
+}
+
+/*
+ * Called before going idle with interrupts disabled. Checks whether a
+ * broadcast event from the other core is about to happen. We detected
+ * that in tick_broadcast_oneshot_control(). The callsite can use this
+ * to avoid a deep idle transition as we are about to get the
+ * broadcast IPI right away.
+ */
+noinstr int tick_check_broadcast_expired(void)
+{
+#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
+	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
+#else
+	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
+#endif
+}
+
+/*
+ * Set broadcast interrupt affinity
+ */
+static void tick_broadcast_set_affinity(struct clock_event_device *bc,
+					const struct cpumask *cpumask)
+{
+	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
+		return;
+
+	if (cpumask_equal(bc->cpumask, cpumask))
+		return;
+
+	bc->cpumask = cpumask;
+	irq_set_affinity(bc->irq, bc->cpumask);
+}
+
+static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
+				     ktime_t expires)
+{
+	if (!clockevent_state_oneshot(bc))
+		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
+
+	clockevents_program_event(bc, expires, 1);
+	tick_broadcast_set_affinity(bc, cpumask_of(cpu));
+}
+
+static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
+{
+	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
+}
+
+/*
+ * Called from irq_enter() when idle was interrupted to reenable the
+ * per cpu device.
+ */
+void tick_check_oneshot_broadcast_this_cpu(void)
+{
+	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
+		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+		/*
+		 * We might be in the middle of switching over from
+		 * periodic to oneshot. If the CPU has not yet
+		 * switched over, leave the device alone.
+		 */
+		if (td->mode == TICKDEV_MODE_ONESHOT) {
+			clockevents_switch_state(td->evtdev,
+					      CLOCK_EVT_STATE_ONESHOT);
+		}
+	}
+}
+
+/*
+ * Handle oneshot mode broadcasting
+ */
+static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
+{
+	struct tick_device *td;
+	ktime_t now, next_event;
+	int cpu, next_cpu = 0;
+	bool bc_local;
+
+	raw_spin_lock(&tick_broadcast_lock);
+	dev->next_event = KTIME_MAX;
+	next_event = KTIME_MAX;
+	cpumask_clear(tmpmask);
+	now = ktime_get();
+	/* Find all expired events */
+	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
+		/*
+		 * Required for !SMP because for_each_cpu() reports
+		 * unconditionally CPU0 as set on UP kernels.
+		 */
+		if (!IS_ENABLED(CONFIG_SMP) &&
+		    cpumask_empty(tick_broadcast_oneshot_mask))
+			break;
+
+		td = &per_cpu(tick_cpu_device, cpu);
+		if (td->evtdev->next_event <= now) {
+			cpumask_set_cpu(cpu, tmpmask);
+			/*
+			 * Mark the remote cpu in the pending mask, so
+			 * it can avoid reprogramming the cpu local
+			 * timer in tick_broadcast_oneshot_control().
+			 */
+			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
+		} else if (td->evtdev->next_event < next_event) {
+			next_event = td->evtdev->next_event;
+			next_cpu = cpu;
+		}
+	}
+
+	/*
+	 * Remove the current cpu from the pending mask. The event is
+	 * delivered immediately in tick_do_broadcast() !
+	 */
+	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
+
+	/* Take care of enforced broadcast requests */
+	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
+	cpumask_clear(tick_broadcast_force_mask);
+
+	/*
+	 * Sanity check. Catch the case where we try to broadcast to
+	 * offline cpus.
+	 */
+	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
+		cpumask_and(tmpmask, tmpmask, cpu_online_mask);
+
+	/*
+	 * Wakeup the cpus which have an expired event.
+	 */
+	bc_local = tick_do_broadcast(tmpmask);
+
+	/*
+	 * Two reasons for reprogram:
+	 *
+	 * - The global event did not expire any CPU local
+	 * events. This happens in dyntick mode, as the maximum PIT
+	 * delta is quite small.
+	 *
+	 * - There are pending events on sleeping CPUs which were not
+	 * in the event mask
+	 */
+	if (next_event != KTIME_MAX)
+		tick_broadcast_set_event(dev, next_cpu, next_event);
+
+	raw_spin_unlock(&tick_broadcast_lock);
+
+	if (bc_local) {
+		td = this_cpu_ptr(&tick_cpu_device);
+		td->evtdev->event_handler(td->evtdev);
+	}
+}
+
+static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
+{
+	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
+		return 0;
+	if (bc->next_event == KTIME_MAX)
+		return 0;
+	return bc->bound_on == cpu ? -EBUSY : 0;
+}
+
+static void broadcast_shutdown_local(struct clock_event_device *bc,
+				     struct clock_event_device *dev)
+{
+	/*
+	 * For hrtimer based broadcasting we cannot shutdown the cpu
+	 * local device if our own event is the first one to expire or
+	 * if we own the broadcast timer.
+	 */
+	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
+		if (broadcast_needs_cpu(bc, smp_processor_id()))
+			return;
+		if (dev->next_event < bc->next_event)
+			return;
+	}
+	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
+}
+
+static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
+					     struct tick_device *td,
+					     int cpu)
+{
+	struct clock_event_device *bc, *dev = td->evtdev;
+	int ret = 0;
+	ktime_t now;
+
+	raw_spin_lock(&tick_broadcast_lock);
+	bc = tick_broadcast_device.evtdev;
+
+	if (state == TICK_BROADCAST_ENTER) {
+		/*
+		 * If the current CPU owns the hrtimer broadcast
+		 * mechanism, it cannot go deep idle and we do not add
+		 * the CPU to the broadcast mask. We don't have to go
+		 * through the EXIT path as the local timer is not
+		 * shutdown.
+		 */
+		ret = broadcast_needs_cpu(bc, cpu);
+		if (ret)
+			goto out;
+
+		/*
+		 * If the broadcast device is in periodic mode, we
+		 * return.
+		 */
+		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
+			/* If it is a hrtimer based broadcast, return busy */
+			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
+				ret = -EBUSY;
+			goto out;
+		}
+
+		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
+			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
+
+			/* Conditionally shut down the local timer. */
+			broadcast_shutdown_local(bc, dev);
+
+			/*
+			 * We only reprogram the broadcast timer if we
+			 * did not mark ourself in the force mask and
+			 * if the cpu local event is earlier than the
+			 * broadcast event. If the current CPU is in
+			 * the force mask, then we are going to be
+			 * woken by the IPI right away; we return
+			 * busy, so the CPU does not try to go deep
+			 * idle.
+			 */
+			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
+				ret = -EBUSY;
+			} else if (dev->next_event < bc->next_event) {
+				tick_broadcast_set_event(bc, cpu, dev->next_event);
+				/*
+				 * In case of hrtimer broadcasts the
+				 * programming might have moved the
+				 * timer to this cpu. If yes, remove
+				 * us from the broadcast mask and
+				 * return busy.
+				 */
+				ret = broadcast_needs_cpu(bc, cpu);
+				if (ret) {
+					cpumask_clear_cpu(cpu,
+						tick_broadcast_oneshot_mask);
+				}
+			}
+		}
+	} else {
+		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
+			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
+			/*
+			 * The cpu which was handling the broadcast
+			 * timer marked this cpu in the broadcast
+			 * pending mask and fired the broadcast
+			 * IPI. So we are going to handle the expired
+			 * event anyway via the broadcast IPI
+			 * handler. No need to reprogram the timer
+			 * with an already expired event.
+			 */
+			if (cpumask_test_and_clear_cpu(cpu,
+				       tick_broadcast_pending_mask))
+				goto out;
+
+			/*
+			 * Bail out if there is no next event.
+			 */
+			if (dev->next_event == KTIME_MAX)
+				goto out;
+			/*
+			 * If the pending bit is not set, then we are
+			 * either the CPU handling the broadcast
+			 * interrupt or we got woken by something else.
+			 *
+			 * We are no longer in the broadcast mask, so
+			 * if the cpu local expiry time is already
+			 * reached, we would reprogram the cpu local
+			 * timer with an already expired event.
+			 *
+			 * This can lead to a ping-pong when we return
+			 * to idle and therefore rearm the broadcast
+			 * timer before the cpu local timer was able
+			 * to fire. This happens because the forced
+			 * reprogramming makes sure that the event
+			 * will happen in the future and depending on
+			 * the min_delta setting this might be far
+			 * enough out that the ping-pong starts.
+			 *
+			 * If the cpu local next_event has expired
+			 * then we know that the broadcast timer
+			 * next_event has expired as well and
+			 * broadcast is about to be handled. So we
+			 * avoid reprogramming and enforce that the
+			 * broadcast handler, which did not run yet,
+			 * will invoke the cpu local handler.
+			 *
+			 * We cannot call the handler directly from
+			 * here, because we might be in a NOHZ phase
+			 * and we did not go through the irq_enter()
+			 * nohz fixups.
+			 */
+			now = ktime_get();
+			if (dev->next_event <= now) {
+				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
+				goto out;
+			}
+			/*
+			 * We got woken by something else. Reprogram
+			 * the cpu local timer device.
+			 */
+			tick_program_event(dev->next_event, 1);
+		}
+	}
+out:
+	raw_spin_unlock(&tick_broadcast_lock);
+	return ret;
+}
+
+static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
+				       struct tick_device *td,
+				       int cpu)
+{
+	struct clock_event_device *dev, *wd;
+
+	dev = td->evtdev;
+	if (td->mode != TICKDEV_MODE_ONESHOT)
+		return -EINVAL;
+
+	wd = tick_get_oneshot_wakeup_device(cpu);
+	if (!wd)
+		return -ENODEV;
+
+	switch (state) {
+	case TICK_BROADCAST_ENTER:
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
+		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
+		clockevents_program_event(wd, dev->next_event, 1);
+		break;
+	case TICK_BROADCAST_EXIT:
+		/* We may have transitioned to oneshot mode while idle */
+		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	int cpu = smp_processor_id();
+
+	if (!tick_oneshot_wakeup_control(state, td, cpu))
+		return 0;
+
+	if (tick_broadcast_device.evtdev)
+		return ___tick_broadcast_oneshot_control(state, td, cpu);
+
+	/*
+	 * If there is no broadcast or wakeup device, tell the caller not
+	 * to go into deep idle.
+	 */
+	return -EBUSY;
+}
+
+/*
+ * Reset the one shot broadcast for a cpu
+ *
+ * Called with tick_broadcast_lock held
+ */
+static void tick_broadcast_clear_oneshot(int cpu)
+{
+	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
+	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
+}
+
+static void tick_broadcast_init_next_event(struct cpumask *mask,
+					   ktime_t expires)
+{
+	struct tick_device *td;
+	int cpu;
+
+	for_each_cpu(cpu, mask) {
+		td = &per_cpu(tick_cpu_device, cpu);
+		if (td->evtdev)
+			td->evtdev->next_event = expires;
+	}
+}
+
+static inline ktime_t tick_get_next_period(void)
+{
+	ktime_t next;
+
+	/*
+	 * Protect against concurrent updates (store /load tearing on
+	 * 32bit). It does not matter if the time is already in the
+	 * past. The broadcast device which is about to be programmed will
+	 * fire in any case.
+	 */
+	raw_spin_lock(&jiffies_lock);
+	next = tick_next_period;
+	raw_spin_unlock(&jiffies_lock);
+	return next;
+}
+
+/**
+ * tick_broadcast_setup_oneshot - setup the broadcast device
+ */
+static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
+					 bool from_periodic)
+{
+	int cpu = smp_processor_id();
+	ktime_t nexttick = 0;
+
+	if (!bc)
+		return;
+
+	/*
+	 * When the broadcast device was switched to oneshot by the first
+	 * CPU handling the NOHZ change, the other CPUs will reach this
+	 * code via hrtimer_run_queues() -> tick_check_oneshot_change()
+	 * too. Set up the broadcast device only once!
+	 */
+	if (bc->event_handler == tick_handle_oneshot_broadcast) {
+		/*
+		 * The CPU which switched from periodic to oneshot mode
+		 * set the broadcast oneshot bit for all other CPUs which
+		 * are in the general (periodic) broadcast mask to ensure
+		 * that CPUs which wait for the periodic broadcast are
+		 * woken up.
+		 *
+		 * Clear the bit for the local CPU as the set bit would
+		 * prevent the first tick_broadcast_enter() after this CPU
+		 * switched to oneshot state to program the broadcast
+		 * device.
+		 *
+		 * This code can also be reached via tick_broadcast_control(),
+		 * but this cannot avoid the tick_broadcast_clear_oneshot()
+		 * as that would break the periodic to oneshot transition of
+		 * secondary CPUs. But that's harmless as the below only
+		 * clears already cleared bits.
+		 */
+		tick_broadcast_clear_oneshot(cpu);
+		return;
+	}
+
+
+	bc->event_handler = tick_handle_oneshot_broadcast;
+	bc->next_event = KTIME_MAX;
+
+	/*
+	 * When the tick mode is switched from periodic to oneshot it must
+	 * be ensured that CPUs which are waiting for periodic broadcast
+	 * get their wake-up at the next tick.  This is achieved by ORing
+	 * tick_broadcast_mask into tick_broadcast_oneshot_mask.
+	 *
+	 * For other callers, e.g. broadcast device replacement,
+	 * tick_broadcast_oneshot_mask must not be touched as this would
+	 * set bits for CPUs which are already NOHZ, but not idle. Their
+	 * next tick_broadcast_enter() would observe the bit set and fail
+	 * to update the expiry time and the broadcast event device.
+	 */
+	if (from_periodic) {
+		cpumask_copy(tmpmask, tick_broadcast_mask);
+		/* Remove the local CPU as it is obviously not idle */
+		cpumask_clear_cpu(cpu, tmpmask);
+		cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
+
+		/*
+		 * Ensure that the oneshot broadcast handler will wake the
+		 * CPUs which are still waiting for periodic broadcast.
+		 */
+		nexttick = tick_get_next_period();
+		tick_broadcast_init_next_event(tmpmask, nexttick);
+
+		/*
+		 * If the underlying broadcast clock event device is
+		 * already in oneshot state, then there is nothing to do.
+		 * The device was already armed for the next tick
+		 * in tick_handle_broadcast_periodic()
+		 */
+		if (clockevent_state_oneshot(bc))
+			return;
+	}
+
+	/*
+	 * When switching from periodic to oneshot mode arm the broadcast
+	 * device for the next tick.
+	 *
+	 * If the broadcast device has been replaced in oneshot mode and
+	 * the oneshot broadcast mask is not empty, then arm it to expire
+	 * immediately in order to reevaluate the next expiring timer.
+	 * @nexttick is 0 and therefore in the past which will cause the
+	 * clockevent code to force an event.
+	 *
+	 * For both cases the programming can be avoided when the oneshot
+	 * broadcast mask is empty.
+	 *
+	 * tick_broadcast_set_event() implicitly switches the broadcast
+	 * device to oneshot state.
+	 */
+	if (!cpumask_empty(tick_broadcast_oneshot_mask))
+		tick_broadcast_set_event(bc, cpu, nexttick);
+}
+
+/*
+ * Select oneshot operating mode for the broadcast device
+ */
+void tick_broadcast_switch_to_oneshot(void)
+{
+	struct clock_event_device *bc;
+	enum tick_device_mode oldmode;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+
+	oldmode = tick_broadcast_device.mode;
+	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
+	bc = tick_broadcast_device.evtdev;
+	if (bc)
+		tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
+
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+void hotplug_cpu__broadcast_tick_pull(int deadcpu)
+{
+	struct clock_event_device *bc;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
+	bc = tick_broadcast_device.evtdev;
+
+	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
+		/* This moves the broadcast assignment to this CPU: */
+		clockevents_program_event(bc, bc->next_event, 1);
+	}
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
+}
+
+/*
+ * Remove a dying CPU from broadcasting
+ */
+static void tick_broadcast_oneshot_offline(unsigned int cpu)
+{
+	if (tick_get_oneshot_wakeup_device(cpu))
+		tick_set_oneshot_wakeup_device(NULL, cpu);
+
+	/*
+	 * Clear the broadcast masks for the dead cpu, but do not stop
+	 * the broadcast device!
+	 */
+	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
+	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
+	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
+}
+#endif
+
+/*
+ * Check, whether the broadcast device is in one shot mode
+ */
+int tick_broadcast_oneshot_active(void)
+{
+	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
+}
+
+/*
+ * Check whether the broadcast device supports oneshot.
+ */
+bool tick_broadcast_oneshot_available(void)
+{
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
+}
+
+#else
+int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
+		return -EBUSY;
+
+	return 0;
+}
+#endif
+
+void __init tick_broadcast_init(void)
+{
+	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
+	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
+	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
+#ifdef CONFIG_TICK_ONESHOT
+	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
+	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
+	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
+#endif
+}
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
new file mode 100644
index 0000000000..e9138cd7a0
--- /dev/null
+++ b/kernel/time/tick-common.c
@@ -0,0 +1,578 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file contains the base functions to manage periodic tick
+ * related events.
+ *
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/nmi.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <trace/events/power.h>
+
+#include <asm/irq_regs.h>
+
+#include "tick-internal.h"
+
+/*
+ * Tick devices
+ */
+DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
+/*
+ * Tick next event: keeps track of the tick time. It's updated by the
+ * CPU which handles the tick and protected by jiffies_lock. There is
+ * no requirement to write hold the jiffies seqcount for it.
+ */
+ktime_t tick_next_period;
+
+/*
+ * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
+ * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
+ * variable has two functions:
+ *
+ * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
+ *    timekeeping lock all at once. Only the CPU which is assigned to do the
+ *    update is handling it.
+ *
+ * 2) Hand off the duty in the NOHZ idle case by setting the value to
+ *    TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
+ *    at it will take over and keep the time keeping alive.  The handover
+ *    procedure also covers cpu hotplug.
+ */
+int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
+#ifdef CONFIG_NO_HZ_FULL
+/*
+ * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
+ * tick_do_timer_cpu and it should be taken over by an eligible secondary
+ * when one comes online.
+ */
+static int tick_do_timer_boot_cpu __read_mostly = -1;
+#endif
+
+/*
+ * Debugging: see timer_list.c
+ */
+struct tick_device *tick_get_device(int cpu)
+{
+	return &per_cpu(tick_cpu_device, cpu);
+}
+
+/**
+ * tick_is_oneshot_available - check for a oneshot capable event device
+ */
+int tick_is_oneshot_available(void)
+{
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+
+	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+		return 0;
+	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+		return 1;
+	return tick_broadcast_oneshot_available();
+}
+
+/*
+ * Periodic tick
+ */
+static void tick_periodic(int cpu)
+{
+	if (tick_do_timer_cpu == cpu) {
+		raw_spin_lock(&jiffies_lock);
+		write_seqcount_begin(&jiffies_seq);
+
+		/* Keep track of the next tick event */
+		tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
+
+		do_timer(1);
+		write_seqcount_end(&jiffies_seq);
+		raw_spin_unlock(&jiffies_lock);
+		update_wall_time();
+	}
+
+	update_process_times(user_mode(get_irq_regs()));
+	profile_tick(CPU_PROFILING);
+}
+
+/*
+ * Event handler for periodic ticks
+ */
+void tick_handle_periodic(struct clock_event_device *dev)
+{
+	int cpu = smp_processor_id();
+	ktime_t next = dev->next_event;
+
+	tick_periodic(cpu);
+
+#if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
+	/*
+	 * The cpu might have transitioned to HIGHRES or NOHZ mode via
+	 * update_process_times() -> run_local_timers() ->
+	 * hrtimer_run_queues().
+	 */
+	if (dev->event_handler != tick_handle_periodic)
+		return;
+#endif
+
+	if (!clockevent_state_oneshot(dev))
+		return;
+	for (;;) {
+		/*
+		 * Setup the next period for devices, which do not have
+		 * periodic mode:
+		 */
+		next = ktime_add_ns(next, TICK_NSEC);
+
+		if (!clockevents_program_event(dev, next, false))
+			return;
+		/*
+		 * Have to be careful here. If we're in oneshot mode,
+		 * before we call tick_periodic() in a loop, we need
+		 * to be sure we're using a real hardware clocksource.
+		 * Otherwise we could get trapped in an infinite
+		 * loop, as the tick_periodic() increments jiffies,
+		 * which then will increment time, possibly causing
+		 * the loop to trigger again and again.
+		 */
+		if (timekeeping_valid_for_hres())
+			tick_periodic(cpu);
+	}
+}
+
+/*
+ * Setup the device for a periodic tick
+ */
+void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
+{
+	tick_set_periodic_handler(dev, broadcast);
+
+	/* Broadcast setup ? */
+	if (!tick_device_is_functional(dev))
+		return;
+
+	if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
+	    !tick_broadcast_oneshot_active()) {
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
+	} else {
+		unsigned int seq;
+		ktime_t next;
+
+		do {
+			seq = read_seqcount_begin(&jiffies_seq);
+			next = tick_next_period;
+		} while (read_seqcount_retry(&jiffies_seq, seq));
+
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
+
+		for (;;) {
+			if (!clockevents_program_event(dev, next, false))
+				return;
+			next = ktime_add_ns(next, TICK_NSEC);
+		}
+	}
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+static void giveup_do_timer(void *info)
+{
+	int cpu = *(unsigned int *)info;
+
+	WARN_ON(tick_do_timer_cpu != smp_processor_id());
+
+	tick_do_timer_cpu = cpu;
+}
+
+static void tick_take_do_timer_from_boot(void)
+{
+	int cpu = smp_processor_id();
+	int from = tick_do_timer_boot_cpu;
+
+	if (from >= 0 && from != cpu)
+		smp_call_function_single(from, giveup_do_timer, &cpu, 1);
+}
+#endif
+
+/*
+ * Setup the tick device
+ */
+static void tick_setup_device(struct tick_device *td,
+			      struct clock_event_device *newdev, int cpu,
+			      const struct cpumask *cpumask)
+{
+	void (*handler)(struct clock_event_device *) = NULL;
+	ktime_t next_event = 0;
+
+	/*
+	 * First device setup ?
+	 */
+	if (!td->evtdev) {
+		/*
+		 * If no cpu took the do_timer update, assign it to
+		 * this cpu:
+		 */
+		if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
+			tick_do_timer_cpu = cpu;
+			tick_next_period = ktime_get();
+#ifdef CONFIG_NO_HZ_FULL
+			/*
+			 * The boot CPU may be nohz_full, in which case set
+			 * tick_do_timer_boot_cpu so the first housekeeping
+			 * secondary that comes up will take do_timer from
+			 * us.
+			 */
+			if (tick_nohz_full_cpu(cpu))
+				tick_do_timer_boot_cpu = cpu;
+
+		} else if (tick_do_timer_boot_cpu != -1 &&
+						!tick_nohz_full_cpu(cpu)) {
+			tick_take_do_timer_from_boot();
+			tick_do_timer_boot_cpu = -1;
+			WARN_ON(tick_do_timer_cpu != cpu);
+#endif
+		}
+
+		/*
+		 * Startup in periodic mode first.
+		 */
+		td->mode = TICKDEV_MODE_PERIODIC;
+	} else {
+		handler = td->evtdev->event_handler;
+		next_event = td->evtdev->next_event;
+		td->evtdev->event_handler = clockevents_handle_noop;
+	}
+
+	td->evtdev = newdev;
+
+	/*
+	 * When the device is not per cpu, pin the interrupt to the
+	 * current cpu:
+	 */
+	if (!cpumask_equal(newdev->cpumask, cpumask))
+		irq_set_affinity(newdev->irq, cpumask);
+
+	/*
+	 * When global broadcasting is active, check if the current
+	 * device is registered as a placeholder for broadcast mode.
+	 * This allows us to handle this x86 misfeature in a generic
+	 * way. This function also returns !=0 when we keep the
+	 * current active broadcast state for this CPU.
+	 */
+	if (tick_device_uses_broadcast(newdev, cpu))
+		return;
+
+	if (td->mode == TICKDEV_MODE_PERIODIC)
+		tick_setup_periodic(newdev, 0);
+	else
+		tick_setup_oneshot(newdev, handler, next_event);
+}
+
+void tick_install_replacement(struct clock_event_device *newdev)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	int cpu = smp_processor_id();
+
+	clockevents_exchange_device(td->evtdev, newdev);
+	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
+	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
+		tick_oneshot_notify();
+}
+
+static bool tick_check_percpu(struct clock_event_device *curdev,
+			      struct clock_event_device *newdev, int cpu)
+{
+	if (!cpumask_test_cpu(cpu, newdev->cpumask))
+		return false;
+	if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
+		return true;
+	/* Check if irq affinity can be set */
+	if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
+		return false;
+	/* Prefer an existing cpu local device */
+	if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
+		return false;
+	return true;
+}
+
+static bool tick_check_preferred(struct clock_event_device *curdev,
+				 struct clock_event_device *newdev)
+{
+	/* Prefer oneshot capable device */
+	if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
+		if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
+			return false;
+		if (tick_oneshot_mode_active())
+			return false;
+	}
+
+	/*
+	 * Use the higher rated one, but prefer a CPU local device with a lower
+	 * rating than a non-CPU local device
+	 */
+	return !curdev ||
+		newdev->rating > curdev->rating ||
+	       !cpumask_equal(curdev->cpumask, newdev->cpumask);
+}
+
+/*
+ * Check whether the new device is a better fit than curdev. curdev
+ * can be NULL !
+ */
+bool tick_check_replacement(struct clock_event_device *curdev,
+			    struct clock_event_device *newdev)
+{
+	if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
+		return false;
+
+	return tick_check_preferred(curdev, newdev);
+}
+
+/*
+ * Check, if the new registered device should be used. Called with
+ * clockevents_lock held and interrupts disabled.
+ */
+void tick_check_new_device(struct clock_event_device *newdev)
+{
+	struct clock_event_device *curdev;
+	struct tick_device *td;
+	int cpu;
+
+	cpu = smp_processor_id();
+	td = &per_cpu(tick_cpu_device, cpu);
+	curdev = td->evtdev;
+
+	if (!tick_check_replacement(curdev, newdev))
+		goto out_bc;
+
+	if (!try_module_get(newdev->owner))
+		return;
+
+	/*
+	 * Replace the eventually existing device by the new
+	 * device. If the current device is the broadcast device, do
+	 * not give it back to the clockevents layer !
+	 */
+	if (tick_is_broadcast_device(curdev)) {
+		clockevents_shutdown(curdev);
+		curdev = NULL;
+	}
+	clockevents_exchange_device(curdev, newdev);
+	tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
+	if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
+		tick_oneshot_notify();
+	return;
+
+out_bc:
+	/*
+	 * Can the new device be used as a broadcast device ?
+	 */
+	tick_install_broadcast_device(newdev, cpu);
+}
+
+/**
+ * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
+ * @state:	The target state (enter/exit)
+ *
+ * The system enters/leaves a state, where affected devices might stop
+ * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
+ *
+ * Called with interrupts disabled, so clockevents_lock is not
+ * required here because the local clock event device cannot go away
+ * under us.
+ */
+int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+	if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
+		return 0;
+
+	return __tick_broadcast_oneshot_control(state);
+}
+EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
+
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Transfer the do_timer job away from a dying cpu.
+ *
+ * Called with interrupts disabled. No locking required. If
+ * tick_do_timer_cpu is owned by this cpu, nothing can change it.
+ */
+void tick_handover_do_timer(void)
+{
+	if (tick_do_timer_cpu == smp_processor_id())
+		tick_do_timer_cpu = cpumask_first(cpu_online_mask);
+}
+
+/*
+ * Shutdown an event device on a given cpu:
+ *
+ * This is called on a life CPU, when a CPU is dead. So we cannot
+ * access the hardware device itself.
+ * We just set the mode and remove it from the lists.
+ */
+void tick_shutdown(unsigned int cpu)
+{
+	struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
+	struct clock_event_device *dev = td->evtdev;
+
+	td->mode = TICKDEV_MODE_PERIODIC;
+	if (dev) {
+		/*
+		 * Prevent that the clock events layer tries to call
+		 * the set mode function!
+		 */
+		clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
+		clockevents_exchange_device(dev, NULL);
+		dev->event_handler = clockevents_handle_noop;
+		td->evtdev = NULL;
+	}
+}
+#endif
+
+/**
+ * tick_suspend_local - Suspend the local tick device
+ *
+ * Called from the local cpu for freeze with interrupts disabled.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_suspend_local(void)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+	clockevents_shutdown(td->evtdev);
+}
+
+/**
+ * tick_resume_local - Resume the local tick device
+ *
+ * Called from the local CPU for unfreeze or XEN resume magic.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_resume_local(void)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	bool broadcast = tick_resume_check_broadcast();
+
+	clockevents_tick_resume(td->evtdev);
+	if (!broadcast) {
+		if (td->mode == TICKDEV_MODE_PERIODIC)
+			tick_setup_periodic(td->evtdev, 0);
+		else
+			tick_resume_oneshot();
+	}
+
+	/*
+	 * Ensure that hrtimers are up to date and the clockevents device
+	 * is reprogrammed correctly when high resolution timers are
+	 * enabled.
+	 */
+	hrtimers_resume_local();
+}
+
+/**
+ * tick_suspend - Suspend the tick and the broadcast device
+ *
+ * Called from syscore_suspend() via timekeeping_suspend with only one
+ * CPU online and interrupts disabled or from tick_unfreeze() under
+ * tick_freeze_lock.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_suspend(void)
+{
+	tick_suspend_local();
+	tick_suspend_broadcast();
+}
+
+/**
+ * tick_resume - Resume the tick and the broadcast device
+ *
+ * Called from syscore_resume() via timekeeping_resume with only one
+ * CPU online and interrupts disabled.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_resume(void)
+{
+	tick_resume_broadcast();
+	tick_resume_local();
+}
+
+#ifdef CONFIG_SUSPEND
+static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
+static unsigned int tick_freeze_depth;
+
+/**
+ * tick_freeze - Suspend the local tick and (possibly) timekeeping.
+ *
+ * Check if this is the last online CPU executing the function and if so,
+ * suspend timekeeping.  Otherwise suspend the local tick.
+ *
+ * Call with interrupts disabled.  Must be balanced with %tick_unfreeze().
+ * Interrupts must not be enabled before the subsequent %tick_unfreeze().
+ */
+void tick_freeze(void)
+{
+	raw_spin_lock(&tick_freeze_lock);
+
+	tick_freeze_depth++;
+	if (tick_freeze_depth == num_online_cpus()) {
+		trace_suspend_resume(TPS("timekeeping_freeze"),
+				     smp_processor_id(), true);
+		system_state = SYSTEM_SUSPEND;
+		sched_clock_suspend();
+		timekeeping_suspend();
+	} else {
+		tick_suspend_local();
+	}
+
+	raw_spin_unlock(&tick_freeze_lock);
+}
+
+/**
+ * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
+ *
+ * Check if this is the first CPU executing the function and if so, resume
+ * timekeeping.  Otherwise resume the local tick.
+ *
+ * Call with interrupts disabled.  Must be balanced with %tick_freeze().
+ * Interrupts must not be enabled after the preceding %tick_freeze().
+ */
+void tick_unfreeze(void)
+{
+	raw_spin_lock(&tick_freeze_lock);
+
+	if (tick_freeze_depth == num_online_cpus()) {
+		timekeeping_resume();
+		sched_clock_resume();
+		system_state = SYSTEM_RUNNING;
+		trace_suspend_resume(TPS("timekeeping_freeze"),
+				     smp_processor_id(), false);
+	} else {
+		touch_softlockup_watchdog();
+		tick_resume_local();
+	}
+
+	tick_freeze_depth--;
+
+	raw_spin_unlock(&tick_freeze_lock);
+}
+#endif /* CONFIG_SUSPEND */
+
+/**
+ * tick_init - initialize the tick control
+ */
+void __init tick_init(void)
+{
+	tick_broadcast_init();
+	tick_nohz_init();
+}
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
new file mode 100644
index 0000000000..649f2b48e8
--- /dev/null
+++ b/kernel/time/tick-internal.h
@@ -0,0 +1,199 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * tick internal variable and functions used by low/high res code
+ */
+#include <linux/hrtimer.h>
+#include <linux/tick.h>
+
+#include "timekeeping.h"
+#include "tick-sched.h"
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+
+# define TICK_DO_TIMER_NONE	-1
+# define TICK_DO_TIMER_BOOT	-2
+
+DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
+extern ktime_t tick_next_period;
+extern int tick_do_timer_cpu __read_mostly;
+
+extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
+extern void tick_handle_periodic(struct clock_event_device *dev);
+extern void tick_check_new_device(struct clock_event_device *dev);
+extern void tick_shutdown(unsigned int cpu);
+extern void tick_suspend(void);
+extern void tick_resume(void);
+extern bool tick_check_replacement(struct clock_event_device *curdev,
+				   struct clock_event_device *newdev);
+extern void tick_install_replacement(struct clock_event_device *dev);
+extern int tick_is_oneshot_available(void);
+extern struct tick_device *tick_get_device(int cpu);
+
+extern int clockevents_tick_resume(struct clock_event_device *dev);
+/* Check, if the device is functional or a dummy for broadcast */
+static inline int tick_device_is_functional(struct clock_event_device *dev)
+{
+	return !(dev->features & CLOCK_EVT_FEAT_DUMMY);
+}
+
+static inline enum clock_event_state clockevent_get_state(struct clock_event_device *dev)
+{
+	return dev->state_use_accessors;
+}
+
+static inline void clockevent_set_state(struct clock_event_device *dev,
+					enum clock_event_state state)
+{
+	dev->state_use_accessors = state;
+}
+
+extern void clockevents_shutdown(struct clock_event_device *dev);
+extern void clockevents_exchange_device(struct clock_event_device *old,
+					struct clock_event_device *new);
+extern void clockevents_switch_state(struct clock_event_device *dev,
+				     enum clock_event_state state);
+extern int clockevents_program_event(struct clock_event_device *dev,
+				     ktime_t expires, bool force);
+extern void clockevents_handle_noop(struct clock_event_device *dev);
+extern int __clockevents_update_freq(struct clock_event_device *dev, u32 freq);
+extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
+
+/* Broadcasting support */
+# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu);
+extern void tick_install_broadcast_device(struct clock_event_device *dev, int cpu);
+extern int tick_is_broadcast_device(struct clock_event_device *dev);
+extern void tick_suspend_broadcast(void);
+extern void tick_resume_broadcast(void);
+extern bool tick_resume_check_broadcast(void);
+extern void tick_broadcast_init(void);
+extern void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
+extern int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq);
+extern struct tick_device *tick_get_broadcast_device(void);
+extern struct cpumask *tick_get_broadcast_mask(void);
+extern const struct clock_event_device *tick_get_wakeup_device(int cpu);
+# else /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST: */
+static inline void tick_install_broadcast_device(struct clock_event_device *dev, int cpu) { }
+static inline int tick_is_broadcast_device(struct clock_event_device *dev) { return 0; }
+static inline int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) { return 0; }
+static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
+static inline void tick_suspend_broadcast(void) { }
+static inline void tick_resume_broadcast(void) { }
+static inline bool tick_resume_check_broadcast(void) { return false; }
+static inline void tick_broadcast_init(void) { }
+static inline int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq) { return -ENODEV; }
+
+/* Set the periodic handler in non broadcast mode */
+static inline void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
+{
+	dev->event_handler = tick_handle_periodic;
+}
+# endif /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST */
+
+#else /* !GENERIC_CLOCKEVENTS: */
+static inline void tick_suspend(void) { }
+static inline void tick_resume(void) { }
+#endif /* !GENERIC_CLOCKEVENTS */
+
+/* Oneshot related functions */
+#ifdef CONFIG_TICK_ONESHOT
+extern void tick_setup_oneshot(struct clock_event_device *newdev,
+			       void (*handler)(struct clock_event_device *),
+			       ktime_t nextevt);
+extern int tick_program_event(ktime_t expires, int force);
+extern void tick_oneshot_notify(void);
+extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *));
+extern void tick_resume_oneshot(void);
+static inline bool tick_oneshot_possible(void) { return true; }
+extern int tick_oneshot_mode_active(void);
+extern void tick_clock_notify(void);
+extern int tick_check_oneshot_change(int allow_nohz);
+extern int tick_init_highres(void);
+#else /* !CONFIG_TICK_ONESHOT: */
+static inline
+void tick_setup_oneshot(struct clock_event_device *newdev,
+			void (*handler)(struct clock_event_device *),
+			ktime_t nextevt) { BUG(); }
+static inline void tick_resume_oneshot(void) { BUG(); }
+static inline int tick_program_event(ktime_t expires, int force) { return 0; }
+static inline void tick_oneshot_notify(void) { }
+static inline bool tick_oneshot_possible(void) { return false; }
+static inline int tick_oneshot_mode_active(void) { return 0; }
+static inline void tick_clock_notify(void) { }
+static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
+#endif /* !CONFIG_TICK_ONESHOT */
+
+/* Functions related to oneshot broadcasting */
+#if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT)
+extern void tick_broadcast_switch_to_oneshot(void);
+extern int tick_broadcast_oneshot_active(void);
+extern void tick_check_oneshot_broadcast_this_cpu(void);
+bool tick_broadcast_oneshot_available(void);
+extern struct cpumask *tick_get_broadcast_oneshot_mask(void);
+#else /* !(BROADCAST && ONESHOT): */
+static inline void tick_broadcast_switch_to_oneshot(void) { }
+static inline int tick_broadcast_oneshot_active(void) { return 0; }
+static inline void tick_check_oneshot_broadcast_this_cpu(void) { }
+static inline bool tick_broadcast_oneshot_available(void) { return tick_oneshot_possible(); }
+#endif /* !(BROADCAST && ONESHOT) */
+
+#if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_HOTPLUG_CPU)
+extern void tick_broadcast_offline(unsigned int cpu);
+#else
+static inline void tick_broadcast_offline(unsigned int cpu) { }
+#endif
+
+/* NO_HZ_FULL internal */
+#ifdef CONFIG_NO_HZ_FULL
+extern void tick_nohz_init(void);
+# else
+static inline void tick_nohz_init(void) { }
+#endif
+
+#ifdef CONFIG_NO_HZ_COMMON
+extern unsigned long tick_nohz_active;
+extern void timers_update_nohz(void);
+# ifdef CONFIG_SMP
+extern struct static_key_false timers_migration_enabled;
+# endif
+#else /* CONFIG_NO_HZ_COMMON */
+static inline void timers_update_nohz(void) { }
+#define tick_nohz_active (0)
+#endif
+
+DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
+
+extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem);
+void timer_clear_idle(void);
+
+#define CLOCK_SET_WALL							\
+	(BIT(HRTIMER_BASE_REALTIME) | BIT(HRTIMER_BASE_REALTIME_SOFT) |	\
+	 BIT(HRTIMER_BASE_TAI) | BIT(HRTIMER_BASE_TAI_SOFT))
+
+#define CLOCK_SET_BOOT							\
+	(BIT(HRTIMER_BASE_BOOTTIME) | BIT(HRTIMER_BASE_BOOTTIME_SOFT))
+
+void clock_was_set(unsigned int bases);
+void clock_was_set_delayed(void);
+
+void hrtimers_resume_local(void);
+
+/* Since jiffies uses a simple TICK_NSEC multiplier
+ * conversion, the .shift value could be zero. However
+ * this would make NTP adjustments impossible as they are
+ * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
+ * shift both the nominator and denominator the same
+ * amount, and give ntp adjustments in units of 1/2^8
+ *
+ * The value 8 is somewhat carefully chosen, as anything
+ * larger can result in overflows. TICK_NSEC grows as HZ
+ * shrinks, so values greater than 8 overflow 32bits when
+ * HZ=100.
+ */
+#if HZ < 34
+#define JIFFIES_SHIFT	6
+#elif HZ < 67
+#define JIFFIES_SHIFT	7
+#else
+#define JIFFIES_SHIFT	8
+#endif
diff --git a/kernel/time/tick-legacy.c b/kernel/time/tick-legacy.c
new file mode 100644
index 0000000000..af225b32f5
--- /dev/null
+++ b/kernel/time/tick-legacy.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Timer tick function for architectures that lack generic clockevents,
+ * consolidated here from m68k/ia64/parisc/arm.
+ */
+
+#include <linux/irq.h>
+#include <linux/profile.h>
+#include <linux/timekeeper_internal.h>
+
+#include "tick-internal.h"
+
+/**
+ * legacy_timer_tick() - advances the timekeeping infrastructure
+ * @ticks:	number of ticks, that have elapsed since the last call.
+ *
+ * This is used by platforms that have not been converted to
+ * generic clockevents.
+ *
+ * If 'ticks' is zero, the CPU is not handling timekeeping, so
+ * only perform process accounting and profiling.
+ *
+ * Must be called with interrupts disabled.
+ */
+void legacy_timer_tick(unsigned long ticks)
+{
+	if (ticks) {
+		raw_spin_lock(&jiffies_lock);
+		write_seqcount_begin(&jiffies_seq);
+		do_timer(ticks);
+		write_seqcount_end(&jiffies_seq);
+		raw_spin_unlock(&jiffies_lock);
+		update_wall_time();
+	}
+	update_process_times(user_mode(get_irq_regs()));
+	profile_tick(CPU_PROFILING);
+}
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
new file mode 100644
index 0000000000..5e2c2c26b3
--- /dev/null
+++ b/kernel/time/tick-oneshot.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file contains functions which manage high resolution tick
+ * related events.
+ *
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/profile.h>
+#include <linux/sched.h>
+
+#include "tick-internal.h"
+
+/**
+ * tick_program_event - program the CPU local timer device for the next event
+ */
+int tick_program_event(ktime_t expires, int force)
+{
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+
+	if (unlikely(expires == KTIME_MAX)) {
+		/*
+		 * We don't need the clock event device any more, stop it.
+		 */
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
+		dev->next_event = KTIME_MAX;
+		return 0;
+	}
+
+	if (unlikely(clockevent_state_oneshot_stopped(dev))) {
+		/*
+		 * We need the clock event again, configure it in ONESHOT mode
+		 * before using it.
+		 */
+		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
+	}
+
+	return clockevents_program_event(dev, expires, force);
+}
+
+/**
+ * tick_resume_oneshot - resume oneshot mode
+ */
+void tick_resume_oneshot(void)
+{
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+
+	clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
+	clockevents_program_event(dev, ktime_get(), true);
+}
+
+/**
+ * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
+ */
+void tick_setup_oneshot(struct clock_event_device *newdev,
+			void (*handler)(struct clock_event_device *),
+			ktime_t next_event)
+{
+	newdev->event_handler = handler;
+	clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
+	clockevents_program_event(newdev, next_event, true);
+}
+
+/**
+ * tick_switch_to_oneshot - switch to oneshot mode
+ */
+int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+	struct clock_event_device *dev = td->evtdev;
+
+	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
+		    !tick_device_is_functional(dev)) {
+
+		pr_info("Clockevents: could not switch to one-shot mode:");
+		if (!dev) {
+			pr_cont(" no tick device\n");
+		} else {
+			if (!tick_device_is_functional(dev))
+				pr_cont(" %s is not functional.\n", dev->name);
+			else
+				pr_cont(" %s does not support one-shot mode.\n",
+					dev->name);
+		}
+		return -EINVAL;
+	}
+
+	td->mode = TICKDEV_MODE_ONESHOT;
+	dev->event_handler = handler;
+	clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
+	tick_broadcast_switch_to_oneshot();
+	return 0;
+}
+
+/**
+ * tick_oneshot_mode_active - check whether the system is in oneshot mode
+ *
+ * returns 1 when either nohz or highres are enabled. otherwise 0.
+ */
+int tick_oneshot_mode_active(void)
+{
+	unsigned long flags;
+	int ret;
+
+	local_irq_save(flags);
+	ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+#ifdef CONFIG_HIGH_RES_TIMERS
+/**
+ * tick_init_highres - switch to high resolution mode
+ *
+ * Called with interrupts disabled.
+ */
+int tick_init_highres(void)
+{
+	return tick_switch_to_oneshot(hrtimer_interrupt);
+}
+#endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
new file mode 100644
index 0000000000..55cbc49f70
--- /dev/null
+++ b/kernel/time/tick-sched.c
@@ -0,0 +1,1617 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
+ *
+ *  No idle tick implementation for low and high resolution timers
+ *
+ *  Started by: Thomas Gleixner and Ingo Molnar
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/percpu.h>
+#include <linux/nmi.h>
+#include <linux/profile.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/stat.h>
+#include <linux/sched/nohz.h>
+#include <linux/sched/loadavg.h>
+#include <linux/module.h>
+#include <linux/irq_work.h>
+#include <linux/posix-timers.h>
+#include <linux/context_tracking.h>
+#include <linux/mm.h>
+
+#include <asm/irq_regs.h>
+
+#include "tick-internal.h"
+
+#include <trace/events/timer.h>
+
+/*
+ * Per-CPU nohz control structure
+ */
+static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
+
+struct tick_sched *tick_get_tick_sched(int cpu)
+{
+	return &per_cpu(tick_cpu_sched, cpu);
+}
+
+#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
+/*
+ * The time, when the last jiffy update happened. Write access must hold
+ * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a
+ * consistent view of jiffies and last_jiffies_update.
+ */
+static ktime_t last_jiffies_update;
+
+/*
+ * Must be called with interrupts disabled !
+ */
+static void tick_do_update_jiffies64(ktime_t now)
+{
+	unsigned long ticks = 1;
+	ktime_t delta, nextp;
+
+	/*
+	 * 64bit can do a quick check without holding jiffies lock and
+	 * without looking at the sequence count. The smp_load_acquire()
+	 * pairs with the update done later in this function.
+	 *
+	 * 32bit cannot do that because the store of tick_next_period
+	 * consists of two 32bit stores and the first store could move it
+	 * to a random point in the future.
+	 */
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		if (ktime_before(now, smp_load_acquire(&tick_next_period)))
+			return;
+	} else {
+		unsigned int seq;
+
+		/*
+		 * Avoid contention on jiffies_lock and protect the quick
+		 * check with the sequence count.
+		 */
+		do {
+			seq = read_seqcount_begin(&jiffies_seq);
+			nextp = tick_next_period;
+		} while (read_seqcount_retry(&jiffies_seq, seq));
+
+		if (ktime_before(now, nextp))
+			return;
+	}
+
+	/* Quick check failed, i.e. update is required. */
+	raw_spin_lock(&jiffies_lock);
+	/*
+	 * Reevaluate with the lock held. Another CPU might have done the
+	 * update already.
+	 */
+	if (ktime_before(now, tick_next_period)) {
+		raw_spin_unlock(&jiffies_lock);
+		return;
+	}
+
+	write_seqcount_begin(&jiffies_seq);
+
+	delta = ktime_sub(now, tick_next_period);
+	if (unlikely(delta >= TICK_NSEC)) {
+		/* Slow path for long idle sleep times */
+		s64 incr = TICK_NSEC;
+
+		ticks += ktime_divns(delta, incr);
+
+		last_jiffies_update = ktime_add_ns(last_jiffies_update,
+						   incr * ticks);
+	} else {
+		last_jiffies_update = ktime_add_ns(last_jiffies_update,
+						   TICK_NSEC);
+	}
+
+	/* Advance jiffies to complete the jiffies_seq protected job */
+	jiffies_64 += ticks;
+
+	/*
+	 * Keep the tick_next_period variable up to date.
+	 */
+	nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
+
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		/*
+		 * Pairs with smp_load_acquire() in the lockless quick
+		 * check above and ensures that the update to jiffies_64 is
+		 * not reordered vs. the store to tick_next_period, neither
+		 * by the compiler nor by the CPU.
+		 */
+		smp_store_release(&tick_next_period, nextp);
+	} else {
+		/*
+		 * A plain store is good enough on 32bit as the quick check
+		 * above is protected by the sequence count.
+		 */
+		tick_next_period = nextp;
+	}
+
+	/*
+	 * Release the sequence count. calc_global_load() below is not
+	 * protected by it, but jiffies_lock needs to be held to prevent
+	 * concurrent invocations.
+	 */
+	write_seqcount_end(&jiffies_seq);
+
+	calc_global_load();
+
+	raw_spin_unlock(&jiffies_lock);
+	update_wall_time();
+}
+
+/*
+ * Initialize and return retrieve the jiffies update.
+ */
+static ktime_t tick_init_jiffy_update(void)
+{
+	ktime_t period;
+
+	raw_spin_lock(&jiffies_lock);
+	write_seqcount_begin(&jiffies_seq);
+	/* Did we start the jiffies update yet ? */
+	if (last_jiffies_update == 0) {
+		u32 rem;
+
+		/*
+		 * Ensure that the tick is aligned to a multiple of
+		 * TICK_NSEC.
+		 */
+		div_u64_rem(tick_next_period, TICK_NSEC, &rem);
+		if (rem)
+			tick_next_period += TICK_NSEC - rem;
+
+		last_jiffies_update = tick_next_period;
+	}
+	period = last_jiffies_update;
+	write_seqcount_end(&jiffies_seq);
+	raw_spin_unlock(&jiffies_lock);
+	return period;
+}
+
+#define MAX_STALLED_JIFFIES 5
+
+static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
+{
+	int cpu = smp_processor_id();
+
+#ifdef CONFIG_NO_HZ_COMMON
+	/*
+	 * Check if the do_timer duty was dropped. We don't care about
+	 * concurrency: This happens only when the CPU in charge went
+	 * into a long sleep. If two CPUs happen to assign themselves to
+	 * this duty, then the jiffies update is still serialized by
+	 * jiffies_lock.
+	 *
+	 * If nohz_full is enabled, this should not happen because the
+	 * tick_do_timer_cpu never relinquishes.
+	 */
+	if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
+#ifdef CONFIG_NO_HZ_FULL
+		WARN_ON_ONCE(tick_nohz_full_running);
+#endif
+		tick_do_timer_cpu = cpu;
+	}
+#endif
+
+	/* Check, if the jiffies need an update */
+	if (tick_do_timer_cpu == cpu)
+		tick_do_update_jiffies64(now);
+
+	/*
+	 * If jiffies update stalled for too long (timekeeper in stop_machine()
+	 * or VMEXIT'ed for several msecs), force an update.
+	 */
+	if (ts->last_tick_jiffies != jiffies) {
+		ts->stalled_jiffies = 0;
+		ts->last_tick_jiffies = READ_ONCE(jiffies);
+	} else {
+		if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
+			tick_do_update_jiffies64(now);
+			ts->stalled_jiffies = 0;
+			ts->last_tick_jiffies = READ_ONCE(jiffies);
+		}
+	}
+
+	if (ts->inidle)
+		ts->got_idle_tick = 1;
+}
+
+static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+	/*
+	 * When we are idle and the tick is stopped, we have to touch
+	 * the watchdog as we might not schedule for a really long
+	 * time. This happens on complete idle SMP systems while
+	 * waiting on the login prompt. We also increment the "start of
+	 * idle" jiffy stamp so the idle accounting adjustment we do
+	 * when we go busy again does not account too much ticks.
+	 */
+	if (ts->tick_stopped) {
+		touch_softlockup_watchdog_sched();
+		if (is_idle_task(current))
+			ts->idle_jiffies++;
+		/*
+		 * In case the current tick fired too early past its expected
+		 * expiration, make sure we don't bypass the next clock reprogramming
+		 * to the same deadline.
+		 */
+		ts->next_tick = 0;
+	}
+#endif
+	update_process_times(user_mode(regs));
+	profile_tick(CPU_PROFILING);
+}
+#endif
+
+#ifdef CONFIG_NO_HZ_FULL
+cpumask_var_t tick_nohz_full_mask;
+EXPORT_SYMBOL_GPL(tick_nohz_full_mask);
+bool tick_nohz_full_running;
+EXPORT_SYMBOL_GPL(tick_nohz_full_running);
+static atomic_t tick_dep_mask;
+
+static bool check_tick_dependency(atomic_t *dep)
+{
+	int val = atomic_read(dep);
+
+	if (val & TICK_DEP_MASK_POSIX_TIMER) {
+		trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
+		return true;
+	}
+
+	if (val & TICK_DEP_MASK_PERF_EVENTS) {
+		trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
+		return true;
+	}
+
+	if (val & TICK_DEP_MASK_SCHED) {
+		trace_tick_stop(0, TICK_DEP_MASK_SCHED);
+		return true;
+	}
+
+	if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
+		trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
+		return true;
+	}
+
+	if (val & TICK_DEP_MASK_RCU) {
+		trace_tick_stop(0, TICK_DEP_MASK_RCU);
+		return true;
+	}
+
+	if (val & TICK_DEP_MASK_RCU_EXP) {
+		trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
+		return true;
+	}
+
+	return false;
+}
+
+static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
+{
+	lockdep_assert_irqs_disabled();
+
+	if (unlikely(!cpu_online(cpu)))
+		return false;
+
+	if (check_tick_dependency(&tick_dep_mask))
+		return false;
+
+	if (check_tick_dependency(&ts->tick_dep_mask))
+		return false;
+
+	if (check_tick_dependency(&current->tick_dep_mask))
+		return false;
+
+	if (check_tick_dependency(&current->signal->tick_dep_mask))
+		return false;
+
+	return true;
+}
+
+static void nohz_full_kick_func(struct irq_work *work)
+{
+	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
+}
+
+static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) =
+	IRQ_WORK_INIT_HARD(nohz_full_kick_func);
+
+/*
+ * Kick this CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
+ * is NMI safe.
+ */
+static void tick_nohz_full_kick(void)
+{
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		return;
+
+	irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
+}
+
+/*
+ * Kick the CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ */
+void tick_nohz_full_kick_cpu(int cpu)
+{
+	if (!tick_nohz_full_cpu(cpu))
+		return;
+
+	irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
+}
+
+static void tick_nohz_kick_task(struct task_struct *tsk)
+{
+	int cpu;
+
+	/*
+	 * If the task is not running, run_posix_cpu_timers()
+	 * has nothing to elapse, IPI can then be spared.
+	 *
+	 * activate_task()                      STORE p->tick_dep_mask
+	 *   STORE p->on_rq
+	 * __schedule() (switch to task 'p')    smp_mb() (atomic_fetch_or())
+	 *   LOCK rq->lock                      LOAD p->on_rq
+	 *   smp_mb__after_spin_lock()
+	 *   tick_nohz_task_switch()
+	 *     LOAD p->tick_dep_mask
+	 */
+	if (!sched_task_on_rq(tsk))
+		return;
+
+	/*
+	 * If the task concurrently migrates to another CPU,
+	 * we guarantee it sees the new tick dependency upon
+	 * schedule.
+	 *
+	 * set_task_cpu(p, cpu);
+	 *   STORE p->cpu = @cpu
+	 * __schedule() (switch to task 'p')
+	 *   LOCK rq->lock
+	 *   smp_mb__after_spin_lock()          STORE p->tick_dep_mask
+	 *   tick_nohz_task_switch()            smp_mb() (atomic_fetch_or())
+	 *      LOAD p->tick_dep_mask           LOAD p->cpu
+	 */
+	cpu = task_cpu(tsk);
+
+	preempt_disable();
+	if (cpu_online(cpu))
+		tick_nohz_full_kick_cpu(cpu);
+	preempt_enable();
+}
+
+/*
+ * Kick all full dynticks CPUs in order to force these to re-evaluate
+ * their dependency on the tick and restart it if necessary.
+ */
+static void tick_nohz_full_kick_all(void)
+{
+	int cpu;
+
+	if (!tick_nohz_full_running)
+		return;
+
+	preempt_disable();
+	for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
+		tick_nohz_full_kick_cpu(cpu);
+	preempt_enable();
+}
+
+static void tick_nohz_dep_set_all(atomic_t *dep,
+				  enum tick_dep_bits bit)
+{
+	int prev;
+
+	prev = atomic_fetch_or(BIT(bit), dep);
+	if (!prev)
+		tick_nohz_full_kick_all();
+}
+
+/*
+ * Set a global tick dependency. Used by perf events that rely on freq and
+ * by unstable clock.
+ */
+void tick_nohz_dep_set(enum tick_dep_bits bit)
+{
+	tick_nohz_dep_set_all(&tick_dep_mask, bit);
+}
+
+void tick_nohz_dep_clear(enum tick_dep_bits bit)
+{
+	atomic_andnot(BIT(bit), &tick_dep_mask);
+}
+
+/*
+ * Set per-CPU tick dependency. Used by scheduler and perf events in order to
+ * manage events throttling.
+ */
+void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
+{
+	int prev;
+	struct tick_sched *ts;
+
+	ts = per_cpu_ptr(&tick_cpu_sched, cpu);
+
+	prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
+	if (!prev) {
+		preempt_disable();
+		/* Perf needs local kick that is NMI safe */
+		if (cpu == smp_processor_id()) {
+			tick_nohz_full_kick();
+		} else {
+			/* Remote irq work not NMI-safe */
+			if (!WARN_ON_ONCE(in_nmi()))
+				tick_nohz_full_kick_cpu(cpu);
+		}
+		preempt_enable();
+	}
+}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
+
+void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
+{
+	struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
+
+	atomic_andnot(BIT(bit), &ts->tick_dep_mask);
+}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
+
+/*
+ * Set a per-task tick dependency. RCU need this. Also posix CPU timers
+ * in order to elapse per task timers.
+ */
+void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
+{
+	if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
+		tick_nohz_kick_task(tsk);
+}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
+
+void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
+{
+	atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
+}
+EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
+
+/*
+ * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
+ * per process timers.
+ */
+void tick_nohz_dep_set_signal(struct task_struct *tsk,
+			      enum tick_dep_bits bit)
+{
+	int prev;
+	struct signal_struct *sig = tsk->signal;
+
+	prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);
+	if (!prev) {
+		struct task_struct *t;
+
+		lockdep_assert_held(&tsk->sighand->siglock);
+		__for_each_thread(sig, t)
+			tick_nohz_kick_task(t);
+	}
+}
+
+void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
+{
+	atomic_andnot(BIT(bit), &sig->tick_dep_mask);
+}
+
+/*
+ * Re-evaluate the need for the tick as we switch the current task.
+ * It might need the tick due to per task/process properties:
+ * perf events, posix CPU timers, ...
+ */
+void __tick_nohz_task_switch(void)
+{
+	struct tick_sched *ts;
+
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		return;
+
+	ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (ts->tick_stopped) {
+		if (atomic_read(&current->tick_dep_mask) ||
+		    atomic_read(&current->signal->tick_dep_mask))
+			tick_nohz_full_kick();
+	}
+}
+
+/* Get the boot-time nohz CPU list from the kernel parameters. */
+void __init tick_nohz_full_setup(cpumask_var_t cpumask)
+{
+	alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
+	cpumask_copy(tick_nohz_full_mask, cpumask);
+	tick_nohz_full_running = true;
+}
+
+bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
+{
+	/*
+	 * The tick_do_timer_cpu CPU handles housekeeping duty (unbound
+	 * timers, workqueues, timekeeping, ...) on behalf of full dynticks
+	 * CPUs. It must remain online when nohz full is enabled.
+	 */
+	if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
+		return false;
+	return true;
+}
+
+static int tick_nohz_cpu_down(unsigned int cpu)
+{
+	return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
+}
+
+void __init tick_nohz_init(void)
+{
+	int cpu, ret;
+
+	if (!tick_nohz_full_running)
+		return;
+
+	/*
+	 * Full dynticks uses irq work to drive the tick rescheduling on safe
+	 * locking contexts. But then we need irq work to raise its own
+	 * interrupts to avoid circular dependency on the tick
+	 */
+	if (!arch_irq_work_has_interrupt()) {
+		pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
+		cpumask_clear(tick_nohz_full_mask);
+		tick_nohz_full_running = false;
+		return;
+	}
+
+	if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
+			!IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
+		cpu = smp_processor_id();
+
+		if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
+			pr_warn("NO_HZ: Clearing %d from nohz_full range "
+				"for timekeeping\n", cpu);
+			cpumask_clear_cpu(cpu, tick_nohz_full_mask);
+		}
+	}
+
+	for_each_cpu(cpu, tick_nohz_full_mask)
+		ct_cpu_track_user(cpu);
+
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					"kernel/nohz:predown", NULL,
+					tick_nohz_cpu_down);
+	WARN_ON(ret < 0);
+	pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
+		cpumask_pr_args(tick_nohz_full_mask));
+}
+#endif
+
+/*
+ * NOHZ - aka dynamic tick functionality
+ */
+#ifdef CONFIG_NO_HZ_COMMON
+/*
+ * NO HZ enabled ?
+ */
+bool tick_nohz_enabled __read_mostly  = true;
+unsigned long tick_nohz_active  __read_mostly;
+/*
+ * Enable / Disable tickless mode
+ */
+static int __init setup_tick_nohz(char *str)
+{
+	return (kstrtobool(str, &tick_nohz_enabled) == 0);
+}
+
+__setup("nohz=", setup_tick_nohz);
+
+bool tick_nohz_tick_stopped(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	return ts->tick_stopped;
+}
+
+bool tick_nohz_tick_stopped_cpu(int cpu)
+{
+	struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
+
+	return ts->tick_stopped;
+}
+
+/**
+ * tick_nohz_update_jiffies - update jiffies when idle was interrupted
+ *
+ * Called from interrupt entry when the CPU was idle
+ *
+ * In case the sched_tick was stopped on this CPU, we have to check if jiffies
+ * must be updated. Otherwise an interrupt handler could use a stale jiffy
+ * value. We do this unconditionally on any CPU, as we don't know whether the
+ * CPU, which has the update task assigned is in a long sleep.
+ */
+static void tick_nohz_update_jiffies(ktime_t now)
+{
+	unsigned long flags;
+
+	__this_cpu_write(tick_cpu_sched.idle_waketime, now);
+
+	local_irq_save(flags);
+	tick_do_update_jiffies64(now);
+	local_irq_restore(flags);
+
+	touch_softlockup_watchdog_sched();
+}
+
+static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
+{
+	ktime_t delta;
+
+	if (WARN_ON_ONCE(!ts->idle_active))
+		return;
+
+	delta = ktime_sub(now, ts->idle_entrytime);
+
+	write_seqcount_begin(&ts->idle_sleeptime_seq);
+	if (nr_iowait_cpu(smp_processor_id()) > 0)
+		ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
+	else
+		ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+
+	ts->idle_entrytime = now;
+	ts->idle_active = 0;
+	write_seqcount_end(&ts->idle_sleeptime_seq);
+
+	sched_clock_idle_wakeup_event();
+}
+
+static void tick_nohz_start_idle(struct tick_sched *ts)
+{
+	write_seqcount_begin(&ts->idle_sleeptime_seq);
+	ts->idle_entrytime = ktime_get();
+	ts->idle_active = 1;
+	write_seqcount_end(&ts->idle_sleeptime_seq);
+
+	sched_clock_idle_sleep_event();
+}
+
+static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
+				 bool compute_delta, u64 *last_update_time)
+{
+	ktime_t now, idle;
+	unsigned int seq;
+
+	if (!tick_nohz_active)
+		return -1;
+
+	now = ktime_get();
+	if (last_update_time)
+		*last_update_time = ktime_to_us(now);
+
+	do {
+		seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
+
+		if (ts->idle_active && compute_delta) {
+			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
+
+			idle = ktime_add(*sleeptime, delta);
+		} else {
+			idle = *sleeptime;
+		}
+	} while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq));
+
+	return ktime_to_us(idle);
+
+}
+
+/**
+ * get_cpu_idle_time_us - get the total idle time of a CPU
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in. Do not update
+ * counters if NULL.
+ *
+ * Return the cumulative idle time (since boot) for a given
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
+ */
+u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
+{
+	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+
+	return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime,
+				     !nr_iowait_cpu(cpu), last_update_time);
+}
+EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
+
+/**
+ * get_cpu_iowait_time_us - get the total iowait time of a CPU
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in. Do not update
+ * counters if NULL.
+ *
+ * Return the cumulative iowait time (since boot) for a given
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
+ */
+u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
+{
+	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+
+	return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime,
+				     nr_iowait_cpu(cpu), last_update_time);
+}
+EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
+
+static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
+{
+	hrtimer_cancel(&ts->sched_timer);
+	hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
+
+	/* Forward the time to expire in the future */
+	hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
+
+	if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
+		hrtimer_start_expires(&ts->sched_timer,
+				      HRTIMER_MODE_ABS_PINNED_HARD);
+	} else {
+		tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+	}
+
+	/*
+	 * Reset to make sure next tick stop doesn't get fooled by past
+	 * cached clock deadline.
+	 */
+	ts->next_tick = 0;
+}
+
+static inline bool local_timer_softirq_pending(void)
+{
+	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
+}
+
+static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
+{
+	u64 basemono, next_tick, delta, expires;
+	unsigned long basejiff;
+	unsigned int seq;
+
+	/* Read jiffies and the time when jiffies were updated last */
+	do {
+		seq = read_seqcount_begin(&jiffies_seq);
+		basemono = last_jiffies_update;
+		basejiff = jiffies;
+	} while (read_seqcount_retry(&jiffies_seq, seq));
+	ts->last_jiffies = basejiff;
+	ts->timer_expires_base = basemono;
+
+	/*
+	 * Keep the periodic tick, when RCU, architecture or irq_work
+	 * requests it.
+	 * Aside of that check whether the local timer softirq is
+	 * pending. If so its a bad idea to call get_next_timer_interrupt()
+	 * because there is an already expired timer, so it will request
+	 * immediate expiry, which rearms the hardware timer with a
+	 * minimal delta which brings us back to this place
+	 * immediately. Lather, rinse and repeat...
+	 */
+	if (rcu_needs_cpu() || arch_needs_cpu() ||
+	    irq_work_needs_cpu() || local_timer_softirq_pending()) {
+		next_tick = basemono + TICK_NSEC;
+	} else {
+		/*
+		 * Get the next pending timer. If high resolution
+		 * timers are enabled this only takes the timer wheel
+		 * timers into account. If high resolution timers are
+		 * disabled this also looks at the next expiring
+		 * hrtimer.
+		 */
+		next_tick = get_next_timer_interrupt(basejiff, basemono);
+		ts->next_timer = next_tick;
+	}
+
+	/*
+	 * If the tick is due in the next period, keep it ticking or
+	 * force prod the timer.
+	 */
+	delta = next_tick - basemono;
+	if (delta <= (u64)TICK_NSEC) {
+		/*
+		 * Tell the timer code that the base is not idle, i.e. undo
+		 * the effect of get_next_timer_interrupt():
+		 */
+		timer_clear_idle();
+		/*
+		 * We've not stopped the tick yet, and there's a timer in the
+		 * next period, so no point in stopping it either, bail.
+		 */
+		if (!ts->tick_stopped) {
+			ts->timer_expires = 0;
+			goto out;
+		}
+	}
+
+	/*
+	 * If this CPU is the one which had the do_timer() duty last, we limit
+	 * the sleep time to the timekeeping max_deferment value.
+	 * Otherwise we can sleep as long as we want.
+	 */
+	delta = timekeeping_max_deferment();
+	if (cpu != tick_do_timer_cpu &&
+	    (tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last))
+		delta = KTIME_MAX;
+
+	/* Calculate the next expiry time */
+	if (delta < (KTIME_MAX - basemono))
+		expires = basemono + delta;
+	else
+		expires = KTIME_MAX;
+
+	ts->timer_expires = min_t(u64, expires, next_tick);
+
+out:
+	return ts->timer_expires;
+}
+
+static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
+{
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+	u64 basemono = ts->timer_expires_base;
+	u64 expires = ts->timer_expires;
+	ktime_t tick = expires;
+
+	/* Make sure we won't be trying to stop it twice in a row. */
+	ts->timer_expires_base = 0;
+
+	/*
+	 * If this CPU is the one which updates jiffies, then give up
+	 * the assignment and let it be taken by the CPU which runs
+	 * the tick timer next, which might be this CPU as well. If we
+	 * don't drop this here the jiffies might be stale and
+	 * do_timer() never invoked. Keep track of the fact that it
+	 * was the one which had the do_timer() duty last.
+	 */
+	if (cpu == tick_do_timer_cpu) {
+		tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+		ts->do_timer_last = 1;
+	} else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
+		ts->do_timer_last = 0;
+	}
+
+	/* Skip reprogram of event if its not changed */
+	if (ts->tick_stopped && (expires == ts->next_tick)) {
+		/* Sanity check: make sure clockevent is actually programmed */
+		if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer))
+			return;
+
+		WARN_ON_ONCE(1);
+		printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n",
+			    basemono, ts->next_tick, dev->next_event,
+			    hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer));
+	}
+
+	/*
+	 * nohz_stop_sched_tick can be called several times before
+	 * the nohz_restart_sched_tick is called. This happens when
+	 * interrupts arrive which do not cause a reschedule. In the
+	 * first call we save the current tick time, so we can restart
+	 * the scheduler tick in nohz_restart_sched_tick.
+	 */
+	if (!ts->tick_stopped) {
+		calc_load_nohz_start();
+		quiet_vmstat();
+
+		ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
+		ts->tick_stopped = 1;
+		trace_tick_stop(1, TICK_DEP_MASK_NONE);
+	}
+
+	ts->next_tick = tick;
+
+	/*
+	 * If the expiration time == KTIME_MAX, then we simply stop
+	 * the tick timer.
+	 */
+	if (unlikely(expires == KTIME_MAX)) {
+		if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+			hrtimer_cancel(&ts->sched_timer);
+		else
+			tick_program_event(KTIME_MAX, 1);
+		return;
+	}
+
+	if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
+		hrtimer_start(&ts->sched_timer, tick,
+			      HRTIMER_MODE_ABS_PINNED_HARD);
+	} else {
+		hrtimer_set_expires(&ts->sched_timer, tick);
+		tick_program_event(tick, 1);
+	}
+}
+
+static void tick_nohz_retain_tick(struct tick_sched *ts)
+{
+	ts->timer_expires_base = 0;
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu)
+{
+	if (tick_nohz_next_event(ts, cpu))
+		tick_nohz_stop_tick(ts, cpu);
+	else
+		tick_nohz_retain_tick(ts);
+}
+#endif /* CONFIG_NO_HZ_FULL */
+
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
+{
+	/* Update jiffies first */
+	tick_do_update_jiffies64(now);
+
+	/*
+	 * Clear the timer idle flag, so we avoid IPIs on remote queueing and
+	 * the clock forward checks in the enqueue path:
+	 */
+	timer_clear_idle();
+
+	calc_load_nohz_stop();
+	touch_softlockup_watchdog_sched();
+	/*
+	 * Cancel the scheduled timer and restore the tick
+	 */
+	ts->tick_stopped  = 0;
+	tick_nohz_restart(ts, now);
+}
+
+static void __tick_nohz_full_update_tick(struct tick_sched *ts,
+					 ktime_t now)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	int cpu = smp_processor_id();
+
+	if (can_stop_full_tick(cpu, ts))
+		tick_nohz_stop_sched_tick(ts, cpu);
+	else if (ts->tick_stopped)
+		tick_nohz_restart_sched_tick(ts, now);
+#endif
+}
+
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
+{
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		return;
+
+	if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
+		return;
+
+	__tick_nohz_full_update_tick(ts, ktime_get());
+}
+
+/*
+ * A pending softirq outside an IRQ (or softirq disabled section) context
+ * should be waiting for ksoftirqd to handle it. Therefore we shouldn't
+ * reach here due to the need_resched() early check in can_stop_idle_tick().
+ *
+ * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the
+ * cpu_down() process, softirqs can still be raised while ksoftirqd is parked,
+ * triggering the below since wakep_softirqd() is ignored.
+ *
+ */
+static bool report_idle_softirq(void)
+{
+	static int ratelimit;
+	unsigned int pending = local_softirq_pending();
+
+	if (likely(!pending))
+		return false;
+
+	/* Some softirqs claim to be safe against hotplug and ksoftirqd parking */
+	if (!cpu_active(smp_processor_id())) {
+		pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK;
+		if (!pending)
+			return false;
+	}
+
+	if (ratelimit >= 10)
+		return false;
+
+	/* On RT, softirqs handling may be waiting on some lock */
+	if (local_bh_blocked())
+		return false;
+
+	pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n",
+		pending);
+	ratelimit++;
+
+	return true;
+}
+
+static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
+{
+	/*
+	 * If this CPU is offline and it is the one which updates
+	 * jiffies, then give up the assignment and let it be taken by
+	 * the CPU which runs the tick timer next. If we don't drop
+	 * this here the jiffies might be stale and do_timer() never
+	 * invoked.
+	 */
+	if (unlikely(!cpu_online(cpu))) {
+		if (cpu == tick_do_timer_cpu)
+			tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+		/*
+		 * Make sure the CPU doesn't get fooled by obsolete tick
+		 * deadline if it comes back online later.
+		 */
+		ts->next_tick = 0;
+		return false;
+	}
+
+	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
+		return false;
+
+	if (need_resched())
+		return false;
+
+	if (unlikely(report_idle_softirq()))
+		return false;
+
+	if (tick_nohz_full_enabled()) {
+		/*
+		 * Keep the tick alive to guarantee timekeeping progression
+		 * if there are full dynticks CPUs around
+		 */
+		if (tick_do_timer_cpu == cpu)
+			return false;
+
+		/* Should not happen for nohz-full */
+		if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
+			return false;
+	}
+
+	return true;
+}
+
+/**
+ * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
+ *
+ * When the next event is more than a tick into the future, stop the idle tick
+ */
+void tick_nohz_idle_stop_tick(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	int cpu = smp_processor_id();
+	ktime_t expires;
+
+	/*
+	 * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
+	 * tick timer expiration time is known already.
+	 */
+	if (ts->timer_expires_base)
+		expires = ts->timer_expires;
+	else if (can_stop_idle_tick(cpu, ts))
+		expires = tick_nohz_next_event(ts, cpu);
+	else
+		return;
+
+	ts->idle_calls++;
+
+	if (expires > 0LL) {
+		int was_stopped = ts->tick_stopped;
+
+		tick_nohz_stop_tick(ts, cpu);
+
+		ts->idle_sleeps++;
+		ts->idle_expires = expires;
+
+		if (!was_stopped && ts->tick_stopped) {
+			ts->idle_jiffies = ts->last_jiffies;
+			nohz_balance_enter_idle(cpu);
+		}
+	} else {
+		tick_nohz_retain_tick(ts);
+	}
+}
+
+void tick_nohz_idle_retain_tick(void)
+{
+	tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
+	/*
+	 * Undo the effect of get_next_timer_interrupt() called from
+	 * tick_nohz_next_event().
+	 */
+	timer_clear_idle();
+}
+
+/**
+ * tick_nohz_idle_enter - prepare for entering idle on the current CPU
+ *
+ * Called when we start the idle loop.
+ */
+void tick_nohz_idle_enter(void)
+{
+	struct tick_sched *ts;
+
+	lockdep_assert_irqs_enabled();
+
+	local_irq_disable();
+
+	ts = this_cpu_ptr(&tick_cpu_sched);
+
+	WARN_ON_ONCE(ts->timer_expires_base);
+
+	ts->inidle = 1;
+	tick_nohz_start_idle(ts);
+
+	local_irq_enable();
+}
+
+/**
+ * tick_nohz_irq_exit - update next tick event from interrupt exit
+ *
+ * When an interrupt fires while we are idle and it doesn't cause
+ * a reschedule, it may still add, modify or delete a timer, enqueue
+ * an RCU callback, etc...
+ * So we need to re-calculate and reprogram the next tick event.
+ */
+void tick_nohz_irq_exit(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (ts->inidle)
+		tick_nohz_start_idle(ts);
+	else
+		tick_nohz_full_update_tick(ts);
+}
+
+/**
+ * tick_nohz_idle_got_tick - Check whether or not the tick handler has run
+ */
+bool tick_nohz_idle_got_tick(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (ts->got_idle_tick) {
+		ts->got_idle_tick = 0;
+		return true;
+	}
+	return false;
+}
+
+/**
+ * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer
+ * or the tick, whatever that expires first. Note that, if the tick has been
+ * stopped, it returns the next hrtimer.
+ *
+ * Called from power state control code with interrupts disabled
+ */
+ktime_t tick_nohz_get_next_hrtimer(void)
+{
+	return __this_cpu_read(tick_cpu_device.evtdev)->next_event;
+}
+
+/**
+ * tick_nohz_get_sleep_length - return the expected length of the current sleep
+ * @delta_next: duration until the next event if the tick cannot be stopped
+ *
+ * Called from power state control code with interrupts disabled.
+ *
+ * The return value of this function and/or the value returned by it through the
+ * @delta_next pointer can be negative which must be taken into account by its
+ * callers.
+ */
+ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
+{
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	int cpu = smp_processor_id();
+	/*
+	 * The idle entry time is expected to be a sufficient approximation of
+	 * the current time at this point.
+	 */
+	ktime_t now = ts->idle_entrytime;
+	ktime_t next_event;
+
+	WARN_ON_ONCE(!ts->inidle);
+
+	*delta_next = ktime_sub(dev->next_event, now);
+
+	if (!can_stop_idle_tick(cpu, ts))
+		return *delta_next;
+
+	next_event = tick_nohz_next_event(ts, cpu);
+	if (!next_event)
+		return *delta_next;
+
+	/*
+	 * If the next highres timer to expire is earlier than next_event, the
+	 * idle governor needs to know that.
+	 */
+	next_event = min_t(u64, next_event,
+			   hrtimer_next_event_without(&ts->sched_timer));
+
+	return ktime_sub(next_event, now);
+}
+
+/**
+ * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
+ * for a particular CPU.
+ *
+ * Called from the schedutil frequency scaling governor in scheduler context.
+ */
+unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
+{
+	struct tick_sched *ts = tick_get_tick_sched(cpu);
+
+	return ts->idle_calls;
+}
+
+/**
+ * tick_nohz_get_idle_calls - return the current idle calls counter value
+ *
+ * Called from the schedutil frequency scaling governor in scheduler context.
+ */
+unsigned long tick_nohz_get_idle_calls(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	return ts->idle_calls;
+}
+
+static void tick_nohz_account_idle_time(struct tick_sched *ts,
+					ktime_t now)
+{
+	unsigned long ticks;
+
+	ts->idle_exittime = now;
+
+	if (vtime_accounting_enabled_this_cpu())
+		return;
+	/*
+	 * We stopped the tick in idle. Update process times would miss the
+	 * time we slept as update_process_times does only a 1 tick
+	 * accounting. Enforce that this is accounted to idle !
+	 */
+	ticks = jiffies - ts->idle_jiffies;
+	/*
+	 * We might be one off. Do not randomly account a huge number of ticks!
+	 */
+	if (ticks && ticks < LONG_MAX)
+		account_idle_ticks(ticks);
+}
+
+void tick_nohz_idle_restart_tick(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (ts->tick_stopped) {
+		ktime_t now = ktime_get();
+		tick_nohz_restart_sched_tick(ts, now);
+		tick_nohz_account_idle_time(ts, now);
+	}
+}
+
+static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
+{
+	if (tick_nohz_full_cpu(smp_processor_id()))
+		__tick_nohz_full_update_tick(ts, now);
+	else
+		tick_nohz_restart_sched_tick(ts, now);
+
+	tick_nohz_account_idle_time(ts, now);
+}
+
+/**
+ * tick_nohz_idle_exit - restart the idle tick from the idle task
+ *
+ * Restart the idle tick when the CPU is woken up from idle
+ * This also exit the RCU extended quiescent state. The CPU
+ * can use RCU again after this function is called.
+ */
+void tick_nohz_idle_exit(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	bool idle_active, tick_stopped;
+	ktime_t now;
+
+	local_irq_disable();
+
+	WARN_ON_ONCE(!ts->inidle);
+	WARN_ON_ONCE(ts->timer_expires_base);
+
+	ts->inidle = 0;
+	idle_active = ts->idle_active;
+	tick_stopped = ts->tick_stopped;
+
+	if (idle_active || tick_stopped)
+		now = ktime_get();
+
+	if (idle_active)
+		tick_nohz_stop_idle(ts, now);
+
+	if (tick_stopped)
+		tick_nohz_idle_update_tick(ts, now);
+
+	local_irq_enable();
+}
+
+/*
+ * The nohz low res interrupt handler
+ */
+static void tick_nohz_handler(struct clock_event_device *dev)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	struct pt_regs *regs = get_irq_regs();
+	ktime_t now = ktime_get();
+
+	dev->next_event = KTIME_MAX;
+
+	tick_sched_do_timer(ts, now);
+	tick_sched_handle(ts, regs);
+
+	if (unlikely(ts->tick_stopped)) {
+		/*
+		 * The clockevent device is not reprogrammed, so change the
+		 * clock event device to ONESHOT_STOPPED to avoid spurious
+		 * interrupts on devices which might not be truly one shot.
+		 */
+		tick_program_event(KTIME_MAX, 1);
+		return;
+	}
+
+	hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
+	tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+}
+
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
+{
+	if (!tick_nohz_enabled)
+		return;
+	ts->nohz_mode = mode;
+	/* One update is enough */
+	if (!test_and_set_bit(0, &tick_nohz_active))
+		timers_update_nohz();
+}
+
+/**
+ * tick_nohz_switch_to_nohz - switch to nohz mode
+ */
+static void tick_nohz_switch_to_nohz(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	ktime_t next;
+
+	if (!tick_nohz_enabled)
+		return;
+
+	if (tick_switch_to_oneshot(tick_nohz_handler))
+		return;
+
+	/*
+	 * Recycle the hrtimer in ts, so we can share the
+	 * hrtimer_forward with the highres code.
+	 */
+	hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
+	/* Get the next period */
+	next = tick_init_jiffy_update();
+
+	hrtimer_set_expires(&ts->sched_timer, next);
+	hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
+	tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+	tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
+}
+
+static inline void tick_nohz_irq_enter(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	ktime_t now;
+
+	if (!ts->idle_active && !ts->tick_stopped)
+		return;
+	now = ktime_get();
+	if (ts->idle_active)
+		tick_nohz_stop_idle(ts, now);
+	/*
+	 * If all CPUs are idle. We may need to update a stale jiffies value.
+	 * Note nohz_full is a special case: a timekeeper is guaranteed to stay
+	 * alive but it might be busy looping with interrupts disabled in some
+	 * rare case (typically stop machine). So we must make sure we have a
+	 * last resort.
+	 */
+	if (ts->tick_stopped)
+		tick_nohz_update_jiffies(now);
+}
+
+#else
+
+static inline void tick_nohz_switch_to_nohz(void) { }
+static inline void tick_nohz_irq_enter(void) { }
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
+
+#endif /* CONFIG_NO_HZ_COMMON */
+
+/*
+ * Called from irq_enter to notify about the possible interruption of idle()
+ */
+void tick_irq_enter(void)
+{
+	tick_check_oneshot_broadcast_this_cpu();
+	tick_nohz_irq_enter();
+}
+
+/*
+ * High resolution timer specific code
+ */
+#ifdef CONFIG_HIGH_RES_TIMERS
+/*
+ * We rearm the timer until we get disabled by the idle code.
+ * Called with interrupts disabled.
+ */
+static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
+{
+	struct tick_sched *ts =
+		container_of(timer, struct tick_sched, sched_timer);
+	struct pt_regs *regs = get_irq_regs();
+	ktime_t now = ktime_get();
+
+	tick_sched_do_timer(ts, now);
+
+	/*
+	 * Do not call, when we are not in irq context and have
+	 * no valid regs pointer
+	 */
+	if (regs)
+		tick_sched_handle(ts, regs);
+	else
+		ts->next_tick = 0;
+
+	/* No need to reprogram if we are in idle or full dynticks mode */
+	if (unlikely(ts->tick_stopped))
+		return HRTIMER_NORESTART;
+
+	hrtimer_forward(timer, now, TICK_NSEC);
+
+	return HRTIMER_RESTART;
+}
+
+static int sched_skew_tick;
+
+static int __init skew_tick(char *str)
+{
+	get_option(&str, &sched_skew_tick);
+
+	return 0;
+}
+early_param("skew_tick", skew_tick);
+
+/**
+ * tick_setup_sched_timer - setup the tick emulation timer
+ */
+void tick_setup_sched_timer(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	ktime_t now = ktime_get();
+
+	/*
+	 * Emulate tick processing via per-CPU hrtimers:
+	 */
+	hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
+	ts->sched_timer.function = tick_sched_timer;
+
+	/* Get the next period (per-CPU) */
+	hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
+
+	/* Offset the tick to avert jiffies_lock contention. */
+	if (sched_skew_tick) {
+		u64 offset = TICK_NSEC >> 1;
+		do_div(offset, num_possible_cpus());
+		offset *= smp_processor_id();
+		hrtimer_add_expires_ns(&ts->sched_timer, offset);
+	}
+
+	hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
+	hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
+	tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
+}
+#endif /* HIGH_RES_TIMERS */
+
+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
+void tick_cancel_sched_timer(int cpu)
+{
+	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	ktime_t idle_sleeptime, iowait_sleeptime;
+	unsigned long idle_calls, idle_sleeps;
+
+# ifdef CONFIG_HIGH_RES_TIMERS
+	if (ts->sched_timer.base)
+		hrtimer_cancel(&ts->sched_timer);
+# endif
+
+	idle_sleeptime = ts->idle_sleeptime;
+	iowait_sleeptime = ts->iowait_sleeptime;
+	idle_calls = ts->idle_calls;
+	idle_sleeps = ts->idle_sleeps;
+	memset(ts, 0, sizeof(*ts));
+	ts->idle_sleeptime = idle_sleeptime;
+	ts->iowait_sleeptime = iowait_sleeptime;
+	ts->idle_calls = idle_calls;
+	ts->idle_sleeps = idle_sleeps;
+}
+#endif
+
+/*
+ * Async notification about clocksource changes
+ */
+void tick_clock_notify(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
+}
+
+/*
+ * Async notification about clock event changes
+ */
+void tick_oneshot_notify(void)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	set_bit(0, &ts->check_clocks);
+}
+
+/*
+ * Check, if a change happened, which makes oneshot possible.
+ *
+ * Called cyclic from the hrtimer softirq (driven by the timer
+ * softirq) allow_nohz signals, that we can switch into low-res nohz
+ * mode, because high resolution timers are disabled (either compile
+ * or runtime). Called with interrupts disabled.
+ */
+int tick_check_oneshot_change(int allow_nohz)
+{
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (!test_and_clear_bit(0, &ts->check_clocks))
+		return 0;
+
+	if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
+		return 0;
+
+	if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
+		return 0;
+
+	if (!allow_nohz)
+		return 1;
+
+	tick_nohz_switch_to_nohz();
+	return 0;
+}
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
new file mode 100644
index 0000000000..5ed5a9d41d
--- /dev/null
+++ b/kernel/time/tick-sched.h
@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TICK_SCHED_H
+#define _TICK_SCHED_H
+
+#include <linux/hrtimer.h>
+
+enum tick_device_mode {
+	TICKDEV_MODE_PERIODIC,
+	TICKDEV_MODE_ONESHOT,
+};
+
+struct tick_device {
+	struct clock_event_device *evtdev;
+	enum tick_device_mode mode;
+};
+
+enum tick_nohz_mode {
+	NOHZ_MODE_INACTIVE,
+	NOHZ_MODE_LOWRES,
+	NOHZ_MODE_HIGHRES,
+};
+
+/**
+ * struct tick_sched - sched tick emulation and no idle tick control/stats
+ *
+ * @inidle:		Indicator that the CPU is in the tick idle mode
+ * @tick_stopped:	Indicator that the idle tick has been stopped
+ * @idle_active:	Indicator that the CPU is actively in the tick idle mode;
+ *			it is reset during irq handling phases.
+ * @do_timer_last:	CPU was the last one doing do_timer before going idle
+ * @got_idle_tick:	Tick timer function has run with @inidle set
+ * @stalled_jiffies:	Number of stalled jiffies detected across ticks
+ * @last_tick_jiffies:	Value of jiffies seen on last tick
+ * @sched_timer:	hrtimer to schedule the periodic tick in high
+ *			resolution mode
+ * @last_tick:		Store the last tick expiry time when the tick
+ *			timer is modified for nohz sleeps. This is necessary
+ *			to resume the tick timer operation in the timeline
+ *			when the CPU returns from nohz sleep.
+ * @next_tick:		Next tick to be fired when in dynticks mode.
+ * @idle_jiffies:	jiffies at the entry to idle for idle time accounting
+ * @idle_waketime:	Time when the idle was interrupted
+ * @idle_entrytime:	Time when the idle call was entered
+ * @nohz_mode:		Mode - one state of tick_nohz_mode
+ * @last_jiffies:	Base jiffies snapshot when next event was last computed
+ * @timer_expires_base:	Base time clock monotonic for @timer_expires
+ * @timer_expires:	Anticipated timer expiration time (in case sched tick is stopped)
+ * @next_timer:		Expiry time of next expiring timer for debugging purpose only
+ * @idle_expires:	Next tick in idle, for debugging purpose only
+ * @idle_calls:		Total number of idle calls
+ * @idle_sleeps:	Number of idle calls, where the sched tick was stopped
+ * @idle_exittime:	Time when the idle state was left
+ * @idle_sleeptime:	Sum of the time slept in idle with sched tick stopped
+ * @iowait_sleeptime:	Sum of the time slept in idle with sched tick stopped, with IO outstanding
+ * @tick_dep_mask:	Tick dependency mask - is set, if someone needs the tick
+ * @check_clocks:	Notification mechanism about clocksource changes
+ */
+struct tick_sched {
+	/* Common flags */
+	unsigned int			inidle		: 1;
+	unsigned int			tick_stopped	: 1;
+	unsigned int			idle_active	: 1;
+	unsigned int			do_timer_last	: 1;
+	unsigned int			got_idle_tick	: 1;
+
+	/* Tick handling: jiffies stall check */
+	unsigned int			stalled_jiffies;
+	unsigned long			last_tick_jiffies;
+
+	/* Tick handling */
+	struct hrtimer			sched_timer;
+	ktime_t				last_tick;
+	ktime_t				next_tick;
+	unsigned long			idle_jiffies;
+	ktime_t				idle_waketime;
+
+	/* Idle entry */
+	seqcount_t			idle_sleeptime_seq;
+	ktime_t				idle_entrytime;
+
+	/* Tick stop */
+	enum tick_nohz_mode		nohz_mode;
+	unsigned long			last_jiffies;
+	u64				timer_expires_base;
+	u64				timer_expires;
+	u64				next_timer;
+	ktime_t				idle_expires;
+	unsigned long			idle_calls;
+	unsigned long			idle_sleeps;
+
+	/* Idle exit */
+	ktime_t				idle_exittime;
+	ktime_t				idle_sleeptime;
+	ktime_t				iowait_sleeptime;
+
+	/* Full dynticks handling */
+	atomic_t			tick_dep_mask;
+
+	/* Clocksource changes */
+	unsigned long			check_clocks;
+};
+
+extern struct tick_sched *tick_get_tick_sched(int cpu);
+
+extern void tick_setup_sched_timer(void);
+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
+extern void tick_cancel_sched_timer(int cpu);
+#else
+static inline void tick_cancel_sched_timer(int cpu) { }
+#endif
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+extern int __tick_broadcast_oneshot_control(enum tick_broadcast_state state);
+#else
+static inline int
+__tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	return -EBUSY;
+}
+#endif
+
+#endif
diff --git a/kernel/time/time.c b/kernel/time/time.c
new file mode 100644
index 0000000000..642647f504
--- /dev/null
+++ b/kernel/time/time.c
@@ -0,0 +1,1056 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  This file contains the interface functions for the various time related
+ *  system calls: time, stime, gettimeofday, settimeofday, adjtime
+ *
+ * Modification history:
+ *
+ * 1993-09-02    Philip Gladstone
+ *      Created file with time related functions from sched/core.c and adjtimex()
+ * 1993-10-08    Torsten Duwe
+ *      adjtime interface update and CMOS clock write code
+ * 1995-08-13    Torsten Duwe
+ *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
+ * 1999-01-16    Ulrich Windl
+ *	Introduced error checking for many cases in adjtimex().
+ *	Updated NTP code according to technical memorandum Jan '96
+ *	"A Kernel Model for Precision Timekeeping" by Dave Mills
+ *	Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
+ *	(Even though the technical memorandum forbids it)
+ * 2004-07-14	 Christoph Lameter
+ *	Added getnstimeofday to allow the posix timer functions to return
+ *	with nanosecond accuracy
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/timex.h>
+#include <linux/capability.h>
+#include <linux/timekeeper_internal.h>
+#include <linux/errno.h>
+#include <linux/syscalls.h>
+#include <linux/security.h>
+#include <linux/fs.h>
+#include <linux/math64.h>
+#include <linux/ptrace.h>
+
+#include <linux/uaccess.h>
+#include <linux/compat.h>
+#include <asm/unistd.h>
+
+#include <generated/timeconst.h>
+#include "timekeeping.h"
+
+/*
+ * The timezone where the local system is located.  Used as a default by some
+ * programs who obtain this value by using gettimeofday.
+ */
+struct timezone sys_tz;
+
+EXPORT_SYMBOL(sys_tz);
+
+#ifdef __ARCH_WANT_SYS_TIME
+
+/*
+ * sys_time() can be implemented in user-level using
+ * sys_gettimeofday().  Is this for backwards compatibility?  If so,
+ * why not move it into the appropriate arch directory (for those
+ * architectures that need it).
+ */
+SYSCALL_DEFINE1(time, __kernel_old_time_t __user *, tloc)
+{
+	__kernel_old_time_t i = (__kernel_old_time_t)ktime_get_real_seconds();
+
+	if (tloc) {
+		if (put_user(i,tloc))
+			return -EFAULT;
+	}
+	force_successful_syscall_return();
+	return i;
+}
+
+/*
+ * sys_stime() can be implemented in user-level using
+ * sys_settimeofday().  Is this for backwards compatibility?  If so,
+ * why not move it into the appropriate arch directory (for those
+ * architectures that need it).
+ */
+
+SYSCALL_DEFINE1(stime, __kernel_old_time_t __user *, tptr)
+{
+	struct timespec64 tv;
+	int err;
+
+	if (get_user(tv.tv_sec, tptr))
+		return -EFAULT;
+
+	tv.tv_nsec = 0;
+
+	err = security_settime64(&tv, NULL);
+	if (err)
+		return err;
+
+	do_settimeofday64(&tv);
+	return 0;
+}
+
+#endif /* __ARCH_WANT_SYS_TIME */
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+#ifdef __ARCH_WANT_SYS_TIME32
+
+/* old_time32_t is a 32 bit "long" and needs to get converted. */
+SYSCALL_DEFINE1(time32, old_time32_t __user *, tloc)
+{
+	old_time32_t i;
+
+	i = (old_time32_t)ktime_get_real_seconds();
+
+	if (tloc) {
+		if (put_user(i,tloc))
+			return -EFAULT;
+	}
+	force_successful_syscall_return();
+	return i;
+}
+
+SYSCALL_DEFINE1(stime32, old_time32_t __user *, tptr)
+{
+	struct timespec64 tv;
+	int err;
+
+	if (get_user(tv.tv_sec, tptr))
+		return -EFAULT;
+
+	tv.tv_nsec = 0;
+
+	err = security_settime64(&tv, NULL);
+	if (err)
+		return err;
+
+	do_settimeofday64(&tv);
+	return 0;
+}
+
+#endif /* __ARCH_WANT_SYS_TIME32 */
+#endif
+
+SYSCALL_DEFINE2(gettimeofday, struct __kernel_old_timeval __user *, tv,
+		struct timezone __user *, tz)
+{
+	if (likely(tv != NULL)) {
+		struct timespec64 ts;
+
+		ktime_get_real_ts64(&ts);
+		if (put_user(ts.tv_sec, &tv->tv_sec) ||
+		    put_user(ts.tv_nsec / 1000, &tv->tv_usec))
+			return -EFAULT;
+	}
+	if (unlikely(tz != NULL)) {
+		if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
+			return -EFAULT;
+	}
+	return 0;
+}
+
+/*
+ * In case for some reason the CMOS clock has not already been running
+ * in UTC, but in some local time: The first time we set the timezone,
+ * we will warp the clock so that it is ticking UTC time instead of
+ * local time. Presumably, if someone is setting the timezone then we
+ * are running in an environment where the programs understand about
+ * timezones. This should be done at boot time in the /etc/rc script,
+ * as soon as possible, so that the clock can be set right. Otherwise,
+ * various programs will get confused when the clock gets warped.
+ */
+
+int do_sys_settimeofday64(const struct timespec64 *tv, const struct timezone *tz)
+{
+	static int firsttime = 1;
+	int error = 0;
+
+	if (tv && !timespec64_valid_settod(tv))
+		return -EINVAL;
+
+	error = security_settime64(tv, tz);
+	if (error)
+		return error;
+
+	if (tz) {
+		/* Verify we're within the +-15 hrs range */
+		if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
+			return -EINVAL;
+
+		sys_tz = *tz;
+		update_vsyscall_tz();
+		if (firsttime) {
+			firsttime = 0;
+			if (!tv)
+				timekeeping_warp_clock();
+		}
+	}
+	if (tv)
+		return do_settimeofday64(tv);
+	return 0;
+}
+
+SYSCALL_DEFINE2(settimeofday, struct __kernel_old_timeval __user *, tv,
+		struct timezone __user *, tz)
+{
+	struct timespec64 new_ts;
+	struct timezone new_tz;
+
+	if (tv) {
+		if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
+		    get_user(new_ts.tv_nsec, &tv->tv_usec))
+			return -EFAULT;
+
+		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
+			return -EINVAL;
+
+		new_ts.tv_nsec *= NSEC_PER_USEC;
+	}
+	if (tz) {
+		if (copy_from_user(&new_tz, tz, sizeof(*tz)))
+			return -EFAULT;
+	}
+
+	return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(gettimeofday, struct old_timeval32 __user *, tv,
+		       struct timezone __user *, tz)
+{
+	if (tv) {
+		struct timespec64 ts;
+
+		ktime_get_real_ts64(&ts);
+		if (put_user(ts.tv_sec, &tv->tv_sec) ||
+		    put_user(ts.tv_nsec / 1000, &tv->tv_usec))
+			return -EFAULT;
+	}
+	if (tz) {
+		if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
+		       struct timezone __user *, tz)
+{
+	struct timespec64 new_ts;
+	struct timezone new_tz;
+
+	if (tv) {
+		if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
+		    get_user(new_ts.tv_nsec, &tv->tv_usec))
+			return -EFAULT;
+
+		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
+			return -EINVAL;
+
+		new_ts.tv_nsec *= NSEC_PER_USEC;
+	}
+	if (tz) {
+		if (copy_from_user(&new_tz, tz, sizeof(*tz)))
+			return -EFAULT;
+	}
+
+	return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
+}
+#endif
+
+#ifdef CONFIG_64BIT
+SYSCALL_DEFINE1(adjtimex, struct __kernel_timex __user *, txc_p)
+{
+	struct __kernel_timex txc;		/* Local copy of parameter */
+	int ret;
+
+	/* Copy the user data space into the kernel copy
+	 * structure. But bear in mind that the structures
+	 * may change
+	 */
+	if (copy_from_user(&txc, txc_p, sizeof(struct __kernel_timex)))
+		return -EFAULT;
+	ret = do_adjtimex(&txc);
+	return copy_to_user(txc_p, &txc, sizeof(struct __kernel_timex)) ? -EFAULT : ret;
+}
+#endif
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+int get_old_timex32(struct __kernel_timex *txc, const struct old_timex32 __user *utp)
+{
+	struct old_timex32 tx32;
+
+	memset(txc, 0, sizeof(struct __kernel_timex));
+	if (copy_from_user(&tx32, utp, sizeof(struct old_timex32)))
+		return -EFAULT;
+
+	txc->modes = tx32.modes;
+	txc->offset = tx32.offset;
+	txc->freq = tx32.freq;
+	txc->maxerror = tx32.maxerror;
+	txc->esterror = tx32.esterror;
+	txc->status = tx32.status;
+	txc->constant = tx32.constant;
+	txc->precision = tx32.precision;
+	txc->tolerance = tx32.tolerance;
+	txc->time.tv_sec = tx32.time.tv_sec;
+	txc->time.tv_usec = tx32.time.tv_usec;
+	txc->tick = tx32.tick;
+	txc->ppsfreq = tx32.ppsfreq;
+	txc->jitter = tx32.jitter;
+	txc->shift = tx32.shift;
+	txc->stabil = tx32.stabil;
+	txc->jitcnt = tx32.jitcnt;
+	txc->calcnt = tx32.calcnt;
+	txc->errcnt = tx32.errcnt;
+	txc->stbcnt = tx32.stbcnt;
+
+	return 0;
+}
+
+int put_old_timex32(struct old_timex32 __user *utp, const struct __kernel_timex *txc)
+{
+	struct old_timex32 tx32;
+
+	memset(&tx32, 0, sizeof(struct old_timex32));
+	tx32.modes = txc->modes;
+	tx32.offset = txc->offset;
+	tx32.freq = txc->freq;
+	tx32.maxerror = txc->maxerror;
+	tx32.esterror = txc->esterror;
+	tx32.status = txc->status;
+	tx32.constant = txc->constant;
+	tx32.precision = txc->precision;
+	tx32.tolerance = txc->tolerance;
+	tx32.time.tv_sec = txc->time.tv_sec;
+	tx32.time.tv_usec = txc->time.tv_usec;
+	tx32.tick = txc->tick;
+	tx32.ppsfreq = txc->ppsfreq;
+	tx32.jitter = txc->jitter;
+	tx32.shift = txc->shift;
+	tx32.stabil = txc->stabil;
+	tx32.jitcnt = txc->jitcnt;
+	tx32.calcnt = txc->calcnt;
+	tx32.errcnt = txc->errcnt;
+	tx32.stbcnt = txc->stbcnt;
+	tx32.tai = txc->tai;
+	if (copy_to_user(utp, &tx32, sizeof(struct old_timex32)))
+		return -EFAULT;
+	return 0;
+}
+
+SYSCALL_DEFINE1(adjtimex_time32, struct old_timex32 __user *, utp)
+{
+	struct __kernel_timex txc;
+	int err, ret;
+
+	err = get_old_timex32(&txc, utp);
+	if (err)
+		return err;
+
+	ret = do_adjtimex(&txc);
+
+	err = put_old_timex32(utp, &txc);
+	if (err)
+		return err;
+
+	return ret;
+}
+#endif
+
+/**
+ * jiffies_to_msecs - Convert jiffies to milliseconds
+ * @j: jiffies value
+ *
+ * Avoid unnecessary multiplications/divisions in the
+ * two most common HZ cases.
+ *
+ * Return: milliseconds value
+ */
+unsigned int jiffies_to_msecs(const unsigned long j)
+{
+#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+	return (MSEC_PER_SEC / HZ) * j;
+#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
+	return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
+#else
+# if BITS_PER_LONG == 32
+	return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >>
+	       HZ_TO_MSEC_SHR32;
+# else
+	return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
+# endif
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_msecs);
+
+/**
+ * jiffies_to_usecs - Convert jiffies to microseconds
+ * @j: jiffies value
+ *
+ * Return: microseconds value
+ */
+unsigned int jiffies_to_usecs(const unsigned long j)
+{
+	/*
+	 * Hz usually doesn't go much further MSEC_PER_SEC.
+	 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
+	 */
+	BUILD_BUG_ON(HZ > USEC_PER_SEC);
+
+#if !(USEC_PER_SEC % HZ)
+	return (USEC_PER_SEC / HZ) * j;
+#else
+# if BITS_PER_LONG == 32
+	return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
+# else
+	return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
+# endif
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_usecs);
+
+/**
+ * mktime64 - Converts date to seconds.
+ * @year0: year to convert
+ * @mon0: month to convert
+ * @day: day to convert
+ * @hour: hour to convert
+ * @min: minute to convert
+ * @sec: second to convert
+ *
+ * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
+ * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
+ * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
+ *
+ * [For the Julian calendar (which was used in Russia before 1917,
+ * Britain & colonies before 1752, anywhere else before 1582,
+ * and is still in use by some communities) leave out the
+ * -year/100+year/400 terms, and add 10.]
+ *
+ * This algorithm was first published by Gauss (I think).
+ *
+ * A leap second can be indicated by calling this function with sec as
+ * 60 (allowable under ISO 8601).  The leap second is treated the same
+ * as the following second since they don't exist in UNIX time.
+ *
+ * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight
+ * tomorrow - (allowable under ISO 8601) is supported.
+ *
+ * Return: seconds since the epoch time for the given input date
+ */
+time64_t mktime64(const unsigned int year0, const unsigned int mon0,
+		const unsigned int day, const unsigned int hour,
+		const unsigned int min, const unsigned int sec)
+{
+	unsigned int mon = mon0, year = year0;
+
+	/* 1..12 -> 11,12,1..10 */
+	if (0 >= (int) (mon -= 2)) {
+		mon += 12;	/* Puts Feb last since it has leap day */
+		year -= 1;
+	}
+
+	return ((((time64_t)
+		  (year/4 - year/100 + year/400 + 367*mon/12 + day) +
+		  year*365 - 719499
+	    )*24 + hour /* now have hours - midnight tomorrow handled here */
+	  )*60 + min /* now have minutes */
+	)*60 + sec; /* finally seconds */
+}
+EXPORT_SYMBOL(mktime64);
+
+struct __kernel_old_timeval ns_to_kernel_old_timeval(s64 nsec)
+{
+	struct timespec64 ts = ns_to_timespec64(nsec);
+	struct __kernel_old_timeval tv;
+
+	tv.tv_sec = ts.tv_sec;
+	tv.tv_usec = (suseconds_t)ts.tv_nsec / 1000;
+
+	return tv;
+}
+EXPORT_SYMBOL(ns_to_kernel_old_timeval);
+
+/**
+ * set_normalized_timespec64 - set timespec sec and nsec parts and normalize
+ *
+ * @ts:		pointer to timespec variable to be set
+ * @sec:	seconds to set
+ * @nsec:	nanoseconds to set
+ *
+ * Set seconds and nanoseconds field of a timespec variable and
+ * normalize to the timespec storage format
+ *
+ * Note: The tv_nsec part is always in the range of 0 <= tv_nsec < NSEC_PER_SEC.
+ * For negative values only the tv_sec field is negative !
+ */
+void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
+{
+	while (nsec >= NSEC_PER_SEC) {
+		/*
+		 * The following asm() prevents the compiler from
+		 * optimising this loop into a modulo operation. See
+		 * also __iter_div_u64_rem() in include/linux/time.h
+		 */
+		asm("" : "+rm"(nsec));
+		nsec -= NSEC_PER_SEC;
+		++sec;
+	}
+	while (nsec < 0) {
+		asm("" : "+rm"(nsec));
+		nsec += NSEC_PER_SEC;
+		--sec;
+	}
+	ts->tv_sec = sec;
+	ts->tv_nsec = nsec;
+}
+EXPORT_SYMBOL(set_normalized_timespec64);
+
+/**
+ * ns_to_timespec64 - Convert nanoseconds to timespec64
+ * @nsec:       the nanoseconds value to be converted
+ *
+ * Return: the timespec64 representation of the nsec parameter.
+ */
+struct timespec64 ns_to_timespec64(s64 nsec)
+{
+	struct timespec64 ts = { 0, 0 };
+	s32 rem;
+
+	if (likely(nsec > 0)) {
+		ts.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
+		ts.tv_nsec = rem;
+	} else if (nsec < 0) {
+		/*
+		 * With negative times, tv_sec points to the earlier
+		 * second, and tv_nsec counts the nanoseconds since
+		 * then, so tv_nsec is always a positive number.
+		 */
+		ts.tv_sec = -div_u64_rem(-nsec - 1, NSEC_PER_SEC, &rem) - 1;
+		ts.tv_nsec = NSEC_PER_SEC - rem - 1;
+	}
+
+	return ts;
+}
+EXPORT_SYMBOL(ns_to_timespec64);
+
+/**
+ * __msecs_to_jiffies: - convert milliseconds to jiffies
+ * @m:	time in milliseconds
+ *
+ * conversion is done as follows:
+ *
+ * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
+ *
+ * - 'too large' values [that would result in larger than
+ *   MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
+ *
+ * - all other values are converted to jiffies by either multiplying
+ *   the input value by a factor or dividing it with a factor and
+ *   handling any 32-bit overflows.
+ *   for the details see __msecs_to_jiffies()
+ *
+ * __msecs_to_jiffies() checks for the passed in value being a constant
+ * via __builtin_constant_p() allowing gcc to eliminate most of the
+ * code, __msecs_to_jiffies() is called if the value passed does not
+ * allow constant folding and the actual conversion must be done at
+ * runtime.
+ * The _msecs_to_jiffies helpers are the HZ dependent conversion
+ * routines found in include/linux/jiffies.h
+ *
+ * Return: jiffies value
+ */
+unsigned long __msecs_to_jiffies(const unsigned int m)
+{
+	/*
+	 * Negative value, means infinite timeout:
+	 */
+	if ((int)m < 0)
+		return MAX_JIFFY_OFFSET;
+	return _msecs_to_jiffies(m);
+}
+EXPORT_SYMBOL(__msecs_to_jiffies);
+
+/**
+ * __usecs_to_jiffies: - convert microseconds to jiffies
+ * @u:	time in milliseconds
+ *
+ * Return: jiffies value
+ */
+unsigned long __usecs_to_jiffies(const unsigned int u)
+{
+	if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
+		return MAX_JIFFY_OFFSET;
+	return _usecs_to_jiffies(u);
+}
+EXPORT_SYMBOL(__usecs_to_jiffies);
+
+/**
+ * timespec64_to_jiffies - convert a timespec64 value to jiffies
+ * @value: pointer to &struct timespec64
+ *
+ * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
+ * that a remainder subtract here would not do the right thing as the
+ * resolution values don't fall on second boundaries.  I.e. the line:
+ * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
+ * Note that due to the small error in the multiplier here, this
+ * rounding is incorrect for sufficiently large values of tv_nsec, but
+ * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
+ * OK.
+ *
+ * Rather, we just shift the bits off the right.
+ *
+ * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
+ * value to a scaled second value.
+ *
+ * Return: jiffies value
+ */
+unsigned long
+timespec64_to_jiffies(const struct timespec64 *value)
+{
+	u64 sec = value->tv_sec;
+	long nsec = value->tv_nsec + TICK_NSEC - 1;
+
+	if (sec >= MAX_SEC_IN_JIFFIES){
+		sec = MAX_SEC_IN_JIFFIES;
+		nsec = 0;
+	}
+	return ((sec * SEC_CONVERSION) +
+		(((u64)nsec * NSEC_CONVERSION) >>
+		 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
+
+}
+EXPORT_SYMBOL(timespec64_to_jiffies);
+
+/**
+ * jiffies_to_timespec64 - convert jiffies value to &struct timespec64
+ * @jiffies: jiffies value
+ * @value: pointer to &struct timespec64
+ */
+void
+jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
+{
+	/*
+	 * Convert jiffies to nanoseconds and separate with
+	 * one divide.
+	 */
+	u32 rem;
+	value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
+				    NSEC_PER_SEC, &rem);
+	value->tv_nsec = rem;
+}
+EXPORT_SYMBOL(jiffies_to_timespec64);
+
+/*
+ * Convert jiffies/jiffies_64 to clock_t and back.
+ */
+
+/**
+ * jiffies_to_clock_t - Convert jiffies to clock_t
+ * @x: jiffies value
+ *
+ * Return: jiffies converted to clock_t (CLOCKS_PER_SEC)
+ */
+clock_t jiffies_to_clock_t(unsigned long x)
+{
+#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
+# if HZ < USER_HZ
+	return x * (USER_HZ / HZ);
+# else
+	return x / (HZ / USER_HZ);
+# endif
+#else
+	return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_clock_t);
+
+/**
+ * clock_t_to_jiffies - Convert clock_t to jiffies
+ * @x: clock_t value
+ *
+ * Return: clock_t value converted to jiffies
+ */
+unsigned long clock_t_to_jiffies(unsigned long x)
+{
+#if (HZ % USER_HZ)==0
+	if (x >= ~0UL / (HZ / USER_HZ))
+		return ~0UL;
+	return x * (HZ / USER_HZ);
+#else
+	/* Don't worry about loss of precision here .. */
+	if (x >= ~0UL / HZ * USER_HZ)
+		return ~0UL;
+
+	/* .. but do try to contain it here */
+	return div_u64((u64)x * HZ, USER_HZ);
+#endif
+}
+EXPORT_SYMBOL(clock_t_to_jiffies);
+
+/**
+ * jiffies_64_to_clock_t - Convert jiffies_64 to clock_t
+ * @x: jiffies_64 value
+ *
+ * Return: jiffies_64 value converted to 64-bit "clock_t" (CLOCKS_PER_SEC)
+ */
+u64 jiffies_64_to_clock_t(u64 x)
+{
+#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
+# if HZ < USER_HZ
+	x = div_u64(x * USER_HZ, HZ);
+# elif HZ > USER_HZ
+	x = div_u64(x, HZ / USER_HZ);
+# else
+	/* Nothing to do */
+# endif
+#else
+	/*
+	 * There are better ways that don't overflow early,
+	 * but even this doesn't overflow in hundreds of years
+	 * in 64 bits, so..
+	 */
+	x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
+#endif
+	return x;
+}
+EXPORT_SYMBOL(jiffies_64_to_clock_t);
+
+/**
+ * nsec_to_clock_t - Convert nsec value to clock_t
+ * @x: nsec value
+ *
+ * Return: nsec value converted to 64-bit "clock_t" (CLOCKS_PER_SEC)
+ */
+u64 nsec_to_clock_t(u64 x)
+{
+#if (NSEC_PER_SEC % USER_HZ) == 0
+	return div_u64(x, NSEC_PER_SEC / USER_HZ);
+#elif (USER_HZ % 512) == 0
+	return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
+#else
+	/*
+         * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
+         * overflow after 64.99 years.
+         * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
+         */
+	return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
+#endif
+}
+
+/**
+ * jiffies64_to_nsecs - Convert jiffies64 to nanoseconds
+ * @j: jiffies64 value
+ *
+ * Return: nanoseconds value
+ */
+u64 jiffies64_to_nsecs(u64 j)
+{
+#if !(NSEC_PER_SEC % HZ)
+	return (NSEC_PER_SEC / HZ) * j;
+# else
+	return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN);
+#endif
+}
+EXPORT_SYMBOL(jiffies64_to_nsecs);
+
+/**
+ * jiffies64_to_msecs - Convert jiffies64 to milliseconds
+ * @j: jiffies64 value
+ *
+ * Return: milliseconds value
+ */
+u64 jiffies64_to_msecs(const u64 j)
+{
+#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+	return (MSEC_PER_SEC / HZ) * j;
+#else
+	return div_u64(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
+#endif
+}
+EXPORT_SYMBOL(jiffies64_to_msecs);
+
+/**
+ * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
+ *
+ * @n:	nsecs in u64
+ *
+ * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
+ * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
+ * for scheduler, not for use in device drivers to calculate timeout value.
+ *
+ * note:
+ *   NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
+ *   ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
+ *
+ * Return: nsecs converted to jiffies64 value
+ */
+u64 nsecs_to_jiffies64(u64 n)
+{
+#if (NSEC_PER_SEC % HZ) == 0
+	/* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
+	return div_u64(n, NSEC_PER_SEC / HZ);
+#elif (HZ % 512) == 0
+	/* overflow after 292 years if HZ = 1024 */
+	return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
+#else
+	/*
+	 * Generic case - optimized for cases where HZ is a multiple of 3.
+	 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
+	 */
+	return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
+#endif
+}
+EXPORT_SYMBOL(nsecs_to_jiffies64);
+
+/**
+ * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
+ *
+ * @n:	nsecs in u64
+ *
+ * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
+ * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
+ * for scheduler, not for use in device drivers to calculate timeout value.
+ *
+ * note:
+ *   NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
+ *   ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
+ *
+ * Return: nsecs converted to jiffies value
+ */
+unsigned long nsecs_to_jiffies(u64 n)
+{
+	return (unsigned long)nsecs_to_jiffies64(n);
+}
+EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
+
+/**
+ * timespec64_add_safe - Add two timespec64 values and do a safety check
+ * for overflow.
+ * @lhs: first (left) timespec64 to add
+ * @rhs: second (right) timespec64 to add
+ *
+ * It's assumed that both values are valid (>= 0).
+ * And, each timespec64 is in normalized form.
+ *
+ * Return: sum of @lhs + @rhs
+ */
+struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
+				const struct timespec64 rhs)
+{
+	struct timespec64 res;
+
+	set_normalized_timespec64(&res, (timeu64_t) lhs.tv_sec + rhs.tv_sec,
+			lhs.tv_nsec + rhs.tv_nsec);
+
+	if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) {
+		res.tv_sec = TIME64_MAX;
+		res.tv_nsec = 0;
+	}
+
+	return res;
+}
+
+/**
+ * get_timespec64 - get user's time value into kernel space
+ * @ts: destination &struct timespec64
+ * @uts: user's time value as &struct __kernel_timespec
+ *
+ * Handles compat or 32-bit modes.
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int get_timespec64(struct timespec64 *ts,
+		   const struct __kernel_timespec __user *uts)
+{
+	struct __kernel_timespec kts;
+	int ret;
+
+	ret = copy_from_user(&kts, uts, sizeof(kts));
+	if (ret)
+		return -EFAULT;
+
+	ts->tv_sec = kts.tv_sec;
+
+	/* Zero out the padding in compat mode */
+	if (in_compat_syscall())
+		kts.tv_nsec &= 0xFFFFFFFFUL;
+
+	/* In 32-bit mode, this drops the padding */
+	ts->tv_nsec = kts.tv_nsec;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_timespec64);
+
+/**
+ * put_timespec64 - convert timespec64 value to __kernel_timespec format and
+ * 		    copy the latter to userspace
+ * @ts: input &struct timespec64
+ * @uts: user's &struct __kernel_timespec
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int put_timespec64(const struct timespec64 *ts,
+		   struct __kernel_timespec __user *uts)
+{
+	struct __kernel_timespec kts = {
+		.tv_sec = ts->tv_sec,
+		.tv_nsec = ts->tv_nsec
+	};
+
+	return copy_to_user(uts, &kts, sizeof(kts)) ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(put_timespec64);
+
+static int __get_old_timespec32(struct timespec64 *ts64,
+				   const struct old_timespec32 __user *cts)
+{
+	struct old_timespec32 ts;
+	int ret;
+
+	ret = copy_from_user(&ts, cts, sizeof(ts));
+	if (ret)
+		return -EFAULT;
+
+	ts64->tv_sec = ts.tv_sec;
+	ts64->tv_nsec = ts.tv_nsec;
+
+	return 0;
+}
+
+static int __put_old_timespec32(const struct timespec64 *ts64,
+				   struct old_timespec32 __user *cts)
+{
+	struct old_timespec32 ts = {
+		.tv_sec = ts64->tv_sec,
+		.tv_nsec = ts64->tv_nsec
+	};
+	return copy_to_user(cts, &ts, sizeof(ts)) ? -EFAULT : 0;
+}
+
+/**
+ * get_old_timespec32 - get user's old-format time value into kernel space
+ * @ts: destination &struct timespec64
+ * @uts: user's old-format time value (&struct old_timespec32)
+ *
+ * Handles X86_X32_ABI compatibility conversion.
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int get_old_timespec32(struct timespec64 *ts, const void __user *uts)
+{
+	if (COMPAT_USE_64BIT_TIME)
+		return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
+	else
+		return __get_old_timespec32(ts, uts);
+}
+EXPORT_SYMBOL_GPL(get_old_timespec32);
+
+/**
+ * put_old_timespec32 - convert timespec64 value to &struct old_timespec32 and
+ * 			copy the latter to userspace
+ * @ts: input &struct timespec64
+ * @uts: user's &struct old_timespec32
+ *
+ * Handles X86_X32_ABI compatibility conversion.
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int put_old_timespec32(const struct timespec64 *ts, void __user *uts)
+{
+	if (COMPAT_USE_64BIT_TIME)
+		return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
+	else
+		return __put_old_timespec32(ts, uts);
+}
+EXPORT_SYMBOL_GPL(put_old_timespec32);
+
+/**
+ * get_itimerspec64 - get user's &struct __kernel_itimerspec into kernel space
+ * @it: destination &struct itimerspec64
+ * @uit: user's &struct __kernel_itimerspec
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int get_itimerspec64(struct itimerspec64 *it,
+			const struct __kernel_itimerspec __user *uit)
+{
+	int ret;
+
+	ret = get_timespec64(&it->it_interval, &uit->it_interval);
+	if (ret)
+		return ret;
+
+	ret = get_timespec64(&it->it_value, &uit->it_value);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(get_itimerspec64);
+
+/**
+ * put_itimerspec64 - convert &struct itimerspec64 to __kernel_itimerspec format
+ * 		      and copy the latter to userspace
+ * @it: input &struct itimerspec64
+ * @uit: user's &struct __kernel_itimerspec
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int put_itimerspec64(const struct itimerspec64 *it,
+			struct __kernel_itimerspec __user *uit)
+{
+	int ret;
+
+	ret = put_timespec64(&it->it_interval, &uit->it_interval);
+	if (ret)
+		return ret;
+
+	ret = put_timespec64(&it->it_value, &uit->it_value);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(put_itimerspec64);
+
+/**
+ * get_old_itimerspec32 - get user's &struct old_itimerspec32 into kernel space
+ * @its: destination &struct itimerspec64
+ * @uits: user's &struct old_itimerspec32
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int get_old_itimerspec32(struct itimerspec64 *its,
+			const struct old_itimerspec32 __user *uits)
+{
+
+	if (__get_old_timespec32(&its->it_interval, &uits->it_interval) ||
+	    __get_old_timespec32(&its->it_value, &uits->it_value))
+		return -EFAULT;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_old_itimerspec32);
+
+/**
+ * put_old_itimerspec32 - convert &struct itimerspec64 to &struct
+ *			  old_itimerspec32 and copy the latter to userspace
+ * @its: input &struct itimerspec64
+ * @uits: user's &struct old_itimerspec32
+ *
+ * Return: %0 on success or negative errno on error
+ */
+int put_old_itimerspec32(const struct itimerspec64 *its,
+			struct old_itimerspec32 __user *uits)
+{
+	if (__put_old_timespec32(&its->it_interval, &uits->it_interval) ||
+	    __put_old_timespec32(&its->it_value, &uits->it_value))
+		return -EFAULT;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(put_old_itimerspec32);
diff --git a/kernel/time/time_test.c b/kernel/time/time_test.c
new file mode 100644
index 0000000000..ca058c8af6
--- /dev/null
+++ b/kernel/time/time_test.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: LGPL-2.1+
+
+#include <kunit/test.h>
+#include <linux/time.h>
+
+/*
+ * Traditional implementation of leap year evaluation.
+ */
+static bool is_leap(long year)
+{
+	return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+}
+
+/*
+ * Gets the last day of a month.
+ */
+static int last_day_of_month(long year, int month)
+{
+	if (month == 2)
+		return 28 + is_leap(year);
+	if (month == 4 || month == 6 || month == 9 || month == 11)
+		return 30;
+	return 31;
+}
+
+/*
+ * Advances a date by one day.
+ */
+static void advance_date(long *year, int *month, int *mday, int *yday)
+{
+	if (*mday != last_day_of_month(*year, *month)) {
+		++*mday;
+		++*yday;
+		return;
+	}
+
+	*mday = 1;
+	if (*month != 12) {
+		++*month;
+		++*yday;
+		return;
+	}
+
+	*month = 1;
+	*yday  = 0;
+	++*year;
+}
+
+/*
+ * Checks every day in a 160000 years interval centered at 1970-01-01
+ * against the expected result.
+ */
+static void time64_to_tm_test_date_range(struct kunit *test)
+{
+	/*
+	 * 80000 years	= (80000 / 400) * 400 years
+	 *		= (80000 / 400) * 146097 days
+	 *		= (80000 / 400) * 146097 * 86400 seconds
+	 */
+	time64_t total_secs = ((time64_t) 80000) / 400 * 146097 * 86400;
+	long year = 1970 - 80000;
+	int month = 1;
+	int mdday = 1;
+	int yday = 0;
+
+	struct tm result;
+	time64_t secs;
+	s64 days;
+
+	for (secs = -total_secs; secs <= total_secs; secs += 86400) {
+
+		time64_to_tm(secs, 0, &result);
+
+		days = div_s64(secs, 86400);
+
+		#define FAIL_MSG "%05ld/%02d/%02d (%2d) : %ld", \
+			year, month, mdday, yday, days
+
+		KUNIT_ASSERT_EQ_MSG(test, year - 1900, result.tm_year, FAIL_MSG);
+		KUNIT_ASSERT_EQ_MSG(test, month - 1, result.tm_mon, FAIL_MSG);
+		KUNIT_ASSERT_EQ_MSG(test, mdday, result.tm_mday, FAIL_MSG);
+		KUNIT_ASSERT_EQ_MSG(test, yday, result.tm_yday, FAIL_MSG);
+
+		advance_date(&year, &month, &mdday, &yday);
+	}
+}
+
+static struct kunit_case time_test_cases[] = {
+	KUNIT_CASE_SLOW(time64_to_tm_test_date_range),
+	{}
+};
+
+static struct kunit_suite time_test_suite = {
+	.name = "time_test_cases",
+	.test_cases = time_test_cases,
+};
+
+kunit_test_suite(time_test_suite);
+MODULE_LICENSE("GPL");
diff --git a/kernel/time/timeconst.bc b/kernel/time/timeconst.bc
new file mode 100644
index 0000000000..7ed0e0fb58
--- /dev/null
+++ b/kernel/time/timeconst.bc
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+scale=0
+
+define gcd(a,b) {
+	auto t;
+	while (b) {
+		t = b;
+		b = a % b;
+		a = t;
+	}
+	return a;
+}
+
+/* Division by reciprocal multiplication. */
+define fmul(b,n,d) {
+       return (2^b*n+d-1)/d;
+}
+
+/* Adjustment factor when a ceiling value is used.  Use as:
+   (imul * n) + (fmulxx * n + fadjxx) >> xx) */
+define fadj(b,n,d) {
+	auto v;
+	d = d/gcd(n,d);
+	v = 2^b*(d-1)/d;
+	return v;
+}
+
+/* Compute the appropriate mul/adj values as well as a shift count,
+   which brings the mul value into the range 2^b-1 <= x < 2^b.  Such
+   a shift value will be correct in the signed integer range and off
+   by at most one in the upper half of the unsigned range. */
+define fmuls(b,n,d) {
+	auto s, m;
+	for (s = 0; 1; s++) {
+		m = fmul(s,n,d);
+		if (m >= 2^(b-1))
+			return s;
+	}
+	return 0;
+}
+
+define timeconst(hz) {
+	print "/* Automatically generated by kernel/time/timeconst.bc */\n"
+	print "/* Time conversion constants for HZ == ", hz, " */\n"
+	print "\n"
+
+	print "#ifndef KERNEL_TIMECONST_H\n"
+	print "#define KERNEL_TIMECONST_H\n\n"
+
+	print "#include <linux/param.h>\n"
+	print "#include <linux/types.h>\n\n"
+
+	print "#if HZ != ", hz, "\n"
+	print "#error \qinclude/generated/timeconst.h has the wrong HZ value!\q\n"
+	print "#endif\n\n"
+
+	if (hz < 2) {
+		print "#error Totally bogus HZ value!\n"
+	} else {
+		s=fmuls(32,1000,hz)
+		obase=16
+		print "#define HZ_TO_MSEC_MUL32\tU64_C(0x", fmul(s,1000,hz), ")\n"
+		print "#define HZ_TO_MSEC_ADJ32\tU64_C(0x", fadj(s,1000,hz), ")\n"
+		obase=10
+		print "#define HZ_TO_MSEC_SHR32\t", s, "\n"
+
+		s=fmuls(32,hz,1000)
+		obase=16
+		print "#define MSEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000), ")\n"
+		print "#define MSEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000), ")\n"
+		obase=10
+		print "#define MSEC_TO_HZ_SHR32\t", s, "\n"
+
+		obase=10
+		cd=gcd(hz,1000)
+		print "#define HZ_TO_MSEC_NUM\t\t", 1000/cd, "\n"
+		print "#define HZ_TO_MSEC_DEN\t\t", hz/cd, "\n"
+		print "#define MSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
+		print "#define MSEC_TO_HZ_DEN\t\t", 1000/cd, "\n"
+		print "\n"
+
+		s=fmuls(32,1000000,hz)
+		obase=16
+		print "#define HZ_TO_USEC_MUL32\tU64_C(0x", fmul(s,1000000,hz), ")\n"
+		print "#define HZ_TO_USEC_ADJ32\tU64_C(0x", fadj(s,1000000,hz), ")\n"
+		obase=10
+		print "#define HZ_TO_USEC_SHR32\t", s, "\n"
+
+		s=fmuls(32,hz,1000000)
+		obase=16
+		print "#define USEC_TO_HZ_MUL32\tU64_C(0x", fmul(s,hz,1000000), ")\n"
+		print "#define USEC_TO_HZ_ADJ32\tU64_C(0x", fadj(s,hz,1000000), ")\n"
+		obase=10
+		print "#define USEC_TO_HZ_SHR32\t", s, "\n"
+
+		obase=10
+		cd=gcd(hz,1000000)
+		print "#define HZ_TO_USEC_NUM\t\t", 1000000/cd, "\n"
+		print "#define HZ_TO_USEC_DEN\t\t", hz/cd, "\n"
+		print "#define USEC_TO_HZ_NUM\t\t", hz/cd, "\n"
+		print "#define USEC_TO_HZ_DEN\t\t", 1000000/cd, "\n"
+
+		cd=gcd(hz,1000000000)
+		print "#define HZ_TO_NSEC_NUM\t\t", 1000000000/cd, "\n"
+		print "#define HZ_TO_NSEC_DEN\t\t", hz/cd, "\n"
+		print "#define NSEC_TO_HZ_NUM\t\t", hz/cd, "\n"
+		print "#define NSEC_TO_HZ_DEN\t\t", 1000000000/cd, "\n"
+		print "\n"
+
+		print "#endif /* KERNEL_TIMECONST_H */\n"
+	}
+	halt
+}
+
+hz = read();
+timeconst(hz)
diff --git a/kernel/time/timeconv.c b/kernel/time/timeconv.c
new file mode 100644
index 0000000000..59b922c826
--- /dev/null
+++ b/kernel/time/timeconv.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: LGPL-2.0+
+/*
+ * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
+ * This file is part of the GNU C Library.
+ * Contributed by Paul Eggert (eggert@twinsun.com).
+ *
+ * The GNU C Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The GNU C Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with the GNU C Library; see the file COPYING.LIB.  If not,
+ * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/*
+ * Converts the calendar time to broken-down time representation
+ *
+ * 2009-7-14:
+ *   Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
+ * 2021-06-02:
+ *   Reimplemented by Cassio Neri <cassio.neri@gmail.com>
+ */
+
+#include <linux/time.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+#define SECS_PER_HOUR	(60 * 60)
+#define SECS_PER_DAY	(SECS_PER_HOUR * 24)
+
+/**
+ * time64_to_tm - converts the calendar time to local broken-down time
+ *
+ * @totalsecs:	the number of seconds elapsed since 00:00:00 on January 1, 1970,
+ *		Coordinated Universal Time (UTC).
+ * @offset:	offset seconds adding to totalsecs.
+ * @result:	pointer to struct tm variable to receive broken-down time
+ */
+void time64_to_tm(time64_t totalsecs, int offset, struct tm *result)
+{
+	u32 u32tmp, day_of_century, year_of_century, day_of_year, month, day;
+	u64 u64tmp, udays, century, year;
+	bool is_Jan_or_Feb, is_leap_year;
+	long days, rem;
+	int remainder;
+
+	days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder);
+	rem = remainder;
+	rem += offset;
+	while (rem < 0) {
+		rem += SECS_PER_DAY;
+		--days;
+	}
+	while (rem >= SECS_PER_DAY) {
+		rem -= SECS_PER_DAY;
+		++days;
+	}
+
+	result->tm_hour = rem / SECS_PER_HOUR;
+	rem %= SECS_PER_HOUR;
+	result->tm_min = rem / 60;
+	result->tm_sec = rem % 60;
+
+	/* January 1, 1970 was a Thursday. */
+	result->tm_wday = (4 + days) % 7;
+	if (result->tm_wday < 0)
+		result->tm_wday += 7;
+
+	/*
+	 * The following algorithm is, basically, Proposition 6.3 of Neri
+	 * and Schneider [1]. In a few words: it works on the computational
+	 * (fictitious) calendar where the year starts in March, month = 2
+	 * (*), and finishes in February, month = 13. This calendar is
+	 * mathematically convenient because the day of the year does not
+	 * depend on whether the year is leap or not. For instance:
+	 *
+	 * March 1st		0-th day of the year;
+	 * ...
+	 * April 1st		31-st day of the year;
+	 * ...
+	 * January 1st		306-th day of the year; (Important!)
+	 * ...
+	 * February 28th	364-th day of the year;
+	 * February 29th	365-th day of the year (if it exists).
+	 *
+	 * After having worked out the date in the computational calendar
+	 * (using just arithmetics) it's easy to convert it to the
+	 * corresponding date in the Gregorian calendar.
+	 *
+	 * [1] "Euclidean Affine Functions and Applications to Calendar
+	 * Algorithms". https://arxiv.org/abs/2102.06959
+	 *
+	 * (*) The numbering of months follows tm more closely and thus,
+	 * is slightly different from [1].
+	 */
+
+	udays	= ((u64) days) + 2305843009213814918ULL;
+
+	u64tmp		= 4 * udays + 3;
+	century		= div64_u64_rem(u64tmp, 146097, &u64tmp);
+	day_of_century	= (u32) (u64tmp / 4);
+
+	u32tmp		= 4 * day_of_century + 3;
+	u64tmp		= 2939745ULL * u32tmp;
+	year_of_century	= upper_32_bits(u64tmp);
+	day_of_year	= lower_32_bits(u64tmp) / 2939745 / 4;
+
+	year		= 100 * century + year_of_century;
+	is_leap_year	= year_of_century ? !(year_of_century % 4) : !(century % 4);
+
+	u32tmp		= 2141 * day_of_year + 132377;
+	month		= u32tmp >> 16;
+	day		= ((u16) u32tmp) / 2141;
+
+	/*
+	 * Recall that January 1st is the 306-th day of the year in the
+	 * computational (not Gregorian) calendar.
+	 */
+	is_Jan_or_Feb	= day_of_year >= 306;
+
+	/* Convert to the Gregorian calendar and adjust to Unix time. */
+	year		= year + is_Jan_or_Feb - 6313183731940000ULL;
+	month		= is_Jan_or_Feb ? month - 12 : month;
+	day		= day + 1;
+	day_of_year	+= is_Jan_or_Feb ? -306 : 31 + 28 + is_leap_year;
+
+	/* Convert to tm's format. */
+	result->tm_year = (long) (year - 1900);
+	result->tm_mon  = (int) month;
+	result->tm_mday = (int) day;
+	result->tm_yday = (int) day_of_year;
+}
+EXPORT_SYMBOL(time64_to_tm);
diff --git a/kernel/time/timecounter.c b/kernel/time/timecounter.c
new file mode 100644
index 0000000000..e6285288d7
--- /dev/null
+++ b/kernel/time/timecounter.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Based on clocksource code. See commit 74d23cc704d1
+ */
+#include <linux/export.h>
+#include <linux/timecounter.h>
+
+void timecounter_init(struct timecounter *tc,
+		      const struct cyclecounter *cc,
+		      u64 start_tstamp)
+{
+	tc->cc = cc;
+	tc->cycle_last = cc->read(cc);
+	tc->nsec = start_tstamp;
+	tc->mask = (1ULL << cc->shift) - 1;
+	tc->frac = 0;
+}
+EXPORT_SYMBOL_GPL(timecounter_init);
+
+/**
+ * timecounter_read_delta - get nanoseconds since last call of this function
+ * @tc:         Pointer to time counter
+ *
+ * When the underlying cycle counter runs over, this will be handled
+ * correctly as long as it does not run over more than once between
+ * calls.
+ *
+ * The first call to this function for a new time counter initializes
+ * the time tracking and returns an undefined result.
+ */
+static u64 timecounter_read_delta(struct timecounter *tc)
+{
+	u64 cycle_now, cycle_delta;
+	u64 ns_offset;
+
+	/* read cycle counter: */
+	cycle_now = tc->cc->read(tc->cc);
+
+	/* calculate the delta since the last timecounter_read_delta(): */
+	cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
+
+	/* convert to nanoseconds: */
+	ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta,
+					tc->mask, &tc->frac);
+
+	/* update time stamp of timecounter_read_delta() call: */
+	tc->cycle_last = cycle_now;
+
+	return ns_offset;
+}
+
+u64 timecounter_read(struct timecounter *tc)
+{
+	u64 nsec;
+
+	/* increment time by nanoseconds since last call */
+	nsec = timecounter_read_delta(tc);
+	nsec += tc->nsec;
+	tc->nsec = nsec;
+
+	return nsec;
+}
+EXPORT_SYMBOL_GPL(timecounter_read);
+
+/*
+ * This is like cyclecounter_cyc2ns(), but it is used for computing a
+ * time previous to the time stored in the cycle counter.
+ */
+static u64 cc_cyc2ns_backwards(const struct cyclecounter *cc,
+			       u64 cycles, u64 mask, u64 frac)
+{
+	u64 ns = (u64) cycles;
+
+	ns = ((ns * cc->mult) - frac) >> cc->shift;
+
+	return ns;
+}
+
+u64 timecounter_cyc2time(const struct timecounter *tc,
+			 u64 cycle_tstamp)
+{
+	u64 delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
+	u64 nsec = tc->nsec, frac = tc->frac;
+
+	/*
+	 * Instead of always treating cycle_tstamp as more recent
+	 * than tc->cycle_last, detect when it is too far in the
+	 * future and treat it as old time stamp instead.
+	 */
+	if (delta > tc->cc->mask / 2) {
+		delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
+		nsec -= cc_cyc2ns_backwards(tc->cc, delta, tc->mask, frac);
+	} else {
+		nsec += cyclecounter_cyc2ns(tc->cc, delta, tc->mask, &frac);
+	}
+
+	return nsec;
+}
+EXPORT_SYMBOL_GPL(timecounter_cyc2time);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
new file mode 100644
index 0000000000..266d02809d
--- /dev/null
+++ b/kernel/time/timekeeping.c
@@ -0,0 +1,2503 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Kernel timekeeping code and accessor functions. Based on code from
+ *  timer.c, moved in commit 8524070b7982.
+ */
+#include <linux/timekeeper_internal.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/nmi.h>
+#include <linux/sched.h>
+#include <linux/sched/loadavg.h>
+#include <linux/sched/clock.h>
+#include <linux/syscore_ops.h>
+#include <linux/clocksource.h>
+#include <linux/jiffies.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/tick.h>
+#include <linux/stop_machine.h>
+#include <linux/pvclock_gtod.h>
+#include <linux/compiler.h>
+#include <linux/audit.h>
+#include <linux/random.h>
+
+#include "tick-internal.h"
+#include "ntp_internal.h"
+#include "timekeeping_internal.h"
+
+#define TK_CLEAR_NTP		(1 << 0)
+#define TK_MIRROR		(1 << 1)
+#define TK_CLOCK_WAS_SET	(1 << 2)
+
+enum timekeeping_adv_mode {
+	/* Update timekeeper when a tick has passed */
+	TK_ADV_TICK,
+
+	/* Update timekeeper on a direct frequency change */
+	TK_ADV_FREQ
+};
+
+DEFINE_RAW_SPINLOCK(timekeeper_lock);
+
+/*
+ * The most important data for readout fits into a single 64 byte
+ * cache line.
+ */
+static struct {
+	seqcount_raw_spinlock_t	seq;
+	struct timekeeper	timekeeper;
+} tk_core ____cacheline_aligned = {
+	.seq = SEQCNT_RAW_SPINLOCK_ZERO(tk_core.seq, &timekeeper_lock),
+};
+
+static struct timekeeper shadow_timekeeper;
+
+/* flag for if timekeeping is suspended */
+int __read_mostly timekeeping_suspended;
+
+/**
+ * struct tk_fast - NMI safe timekeeper
+ * @seq:	Sequence counter for protecting updates. The lowest bit
+ *		is the index for the tk_read_base array
+ * @base:	tk_read_base array. Access is indexed by the lowest bit of
+ *		@seq.
+ *
+ * See @update_fast_timekeeper() below.
+ */
+struct tk_fast {
+	seqcount_latch_t	seq;
+	struct tk_read_base	base[2];
+};
+
+/* Suspend-time cycles value for halted fast timekeeper. */
+static u64 cycles_at_suspend;
+
+static u64 dummy_clock_read(struct clocksource *cs)
+{
+	if (timekeeping_suspended)
+		return cycles_at_suspend;
+	return local_clock();
+}
+
+static struct clocksource dummy_clock = {
+	.read = dummy_clock_read,
+};
+
+/*
+ * Boot time initialization which allows local_clock() to be utilized
+ * during early boot when clocksources are not available. local_clock()
+ * returns nanoseconds already so no conversion is required, hence mult=1
+ * and shift=0. When the first proper clocksource is installed then
+ * the fast time keepers are updated with the correct values.
+ */
+#define FAST_TK_INIT						\
+	{							\
+		.clock		= &dummy_clock,			\
+		.mask		= CLOCKSOURCE_MASK(64),		\
+		.mult		= 1,				\
+		.shift		= 0,				\
+	}
+
+static struct tk_fast tk_fast_mono ____cacheline_aligned = {
+	.seq     = SEQCNT_LATCH_ZERO(tk_fast_mono.seq),
+	.base[0] = FAST_TK_INIT,
+	.base[1] = FAST_TK_INIT,
+};
+
+static struct tk_fast tk_fast_raw  ____cacheline_aligned = {
+	.seq     = SEQCNT_LATCH_ZERO(tk_fast_raw.seq),
+	.base[0] = FAST_TK_INIT,
+	.base[1] = FAST_TK_INIT,
+};
+
+static inline void tk_normalize_xtime(struct timekeeper *tk)
+{
+	while (tk->tkr_mono.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_mono.shift)) {
+		tk->tkr_mono.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
+		tk->xtime_sec++;
+	}
+	while (tk->tkr_raw.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_raw.shift)) {
+		tk->tkr_raw.xtime_nsec -= (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
+		tk->raw_sec++;
+	}
+}
+
+static inline struct timespec64 tk_xtime(const struct timekeeper *tk)
+{
+	struct timespec64 ts;
+
+	ts.tv_sec = tk->xtime_sec;
+	ts.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
+	return ts;
+}
+
+static void tk_set_xtime(struct timekeeper *tk, const struct timespec64 *ts)
+{
+	tk->xtime_sec = ts->tv_sec;
+	tk->tkr_mono.xtime_nsec = (u64)ts->tv_nsec << tk->tkr_mono.shift;
+}
+
+static void tk_xtime_add(struct timekeeper *tk, const struct timespec64 *ts)
+{
+	tk->xtime_sec += ts->tv_sec;
+	tk->tkr_mono.xtime_nsec += (u64)ts->tv_nsec << tk->tkr_mono.shift;
+	tk_normalize_xtime(tk);
+}
+
+static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
+{
+	struct timespec64 tmp;
+
+	/*
+	 * Verify consistency of: offset_real = -wall_to_monotonic
+	 * before modifying anything
+	 */
+	set_normalized_timespec64(&tmp, -tk->wall_to_monotonic.tv_sec,
+					-tk->wall_to_monotonic.tv_nsec);
+	WARN_ON_ONCE(tk->offs_real != timespec64_to_ktime(tmp));
+	tk->wall_to_monotonic = wtm;
+	set_normalized_timespec64(&tmp, -wtm.tv_sec, -wtm.tv_nsec);
+	tk->offs_real = timespec64_to_ktime(tmp);
+	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tk->tai_offset, 0));
+}
+
+static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta)
+{
+	tk->offs_boot = ktime_add(tk->offs_boot, delta);
+	/*
+	 * Timespec representation for VDSO update to avoid 64bit division
+	 * on every update.
+	 */
+	tk->monotonic_to_boot = ktime_to_timespec64(tk->offs_boot);
+}
+
+/*
+ * tk_clock_read - atomic clocksource read() helper
+ *
+ * This helper is necessary to use in the read paths because, while the
+ * seqcount ensures we don't return a bad value while structures are updated,
+ * it doesn't protect from potential crashes. There is the possibility that
+ * the tkr's clocksource may change between the read reference, and the
+ * clock reference passed to the read function.  This can cause crashes if
+ * the wrong clocksource is passed to the wrong read function.
+ * This isn't necessary to use when holding the timekeeper_lock or doing
+ * a read of the fast-timekeeper tkrs (which is protected by its own locking
+ * and update logic).
+ */
+static inline u64 tk_clock_read(const struct tk_read_base *tkr)
+{
+	struct clocksource *clock = READ_ONCE(tkr->clock);
+
+	return clock->read(clock);
+}
+
+#ifdef CONFIG_DEBUG_TIMEKEEPING
+#define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */
+
+static void timekeeping_check_update(struct timekeeper *tk, u64 offset)
+{
+
+	u64 max_cycles = tk->tkr_mono.clock->max_cycles;
+	const char *name = tk->tkr_mono.clock->name;
+
+	if (offset > max_cycles) {
+		printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow danger\n",
+				offset, name, max_cycles);
+		printk_deferred("         timekeeping: Your kernel is sick, but tries to cope by capping time updates\n");
+	} else {
+		if (offset > (max_cycles >> 1)) {
+			printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the '%s' clock's 50%% safety margin (%lld)\n",
+					offset, name, max_cycles >> 1);
+			printk_deferred("      timekeeping: Your kernel is still fine, but is feeling a bit nervous\n");
+		}
+	}
+
+	if (tk->underflow_seen) {
+		if (jiffies - tk->last_warning > WARNING_FREQ) {
+			printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);
+			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
+			printk_deferred("         Your kernel is probably still fine.\n");
+			tk->last_warning = jiffies;
+		}
+		tk->underflow_seen = 0;
+	}
+
+	if (tk->overflow_seen) {
+		if (jiffies - tk->last_warning > WARNING_FREQ) {
+			printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);
+			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
+			printk_deferred("         Your kernel is probably still fine.\n");
+			tk->last_warning = jiffies;
+		}
+		tk->overflow_seen = 0;
+	}
+}
+
+static inline u64 timekeeping_get_delta(const struct tk_read_base *tkr)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	u64 now, last, mask, max, delta;
+	unsigned int seq;
+
+	/*
+	 * Since we're called holding a seqcount, the data may shift
+	 * under us while we're doing the calculation. This can cause
+	 * false positives, since we'd note a problem but throw the
+	 * results away. So nest another seqcount here to atomically
+	 * grab the points we are checking with.
+	 */
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		now = tk_clock_read(tkr);
+		last = tkr->cycle_last;
+		mask = tkr->mask;
+		max = tkr->clock->max_cycles;
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	delta = clocksource_delta(now, last, mask);
+
+	/*
+	 * Try to catch underflows by checking if we are seeing small
+	 * mask-relative negative values.
+	 */
+	if (unlikely((~delta & mask) < (mask >> 3))) {
+		tk->underflow_seen = 1;
+		delta = 0;
+	}
+
+	/* Cap delta value to the max_cycles values to avoid mult overflows */
+	if (unlikely(delta > max)) {
+		tk->overflow_seen = 1;
+		delta = tkr->clock->max_cycles;
+	}
+
+	return delta;
+}
+#else
+static inline void timekeeping_check_update(struct timekeeper *tk, u64 offset)
+{
+}
+static inline u64 timekeeping_get_delta(const struct tk_read_base *tkr)
+{
+	u64 cycle_now, delta;
+
+	/* read clocksource */
+	cycle_now = tk_clock_read(tkr);
+
+	/* calculate the delta since the last update_wall_time */
+	delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);
+
+	return delta;
+}
+#endif
+
+/**
+ * tk_setup_internals - Set up internals to use clocksource clock.
+ *
+ * @tk:		The target timekeeper to setup.
+ * @clock:		Pointer to clocksource.
+ *
+ * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
+ * pair and interval request.
+ *
+ * Unless you're the timekeeping code, you should not be using this!
+ */
+static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
+{
+	u64 interval;
+	u64 tmp, ntpinterval;
+	struct clocksource *old_clock;
+
+	++tk->cs_was_changed_seq;
+	old_clock = tk->tkr_mono.clock;
+	tk->tkr_mono.clock = clock;
+	tk->tkr_mono.mask = clock->mask;
+	tk->tkr_mono.cycle_last = tk_clock_read(&tk->tkr_mono);
+
+	tk->tkr_raw.clock = clock;
+	tk->tkr_raw.mask = clock->mask;
+	tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
+
+	/* Do the ns -> cycle conversion first, using original mult */
+	tmp = NTP_INTERVAL_LENGTH;
+	tmp <<= clock->shift;
+	ntpinterval = tmp;
+	tmp += clock->mult/2;
+	do_div(tmp, clock->mult);
+	if (tmp == 0)
+		tmp = 1;
+
+	interval = (u64) tmp;
+	tk->cycle_interval = interval;
+
+	/* Go back from cycles -> shifted ns */
+	tk->xtime_interval = interval * clock->mult;
+	tk->xtime_remainder = ntpinterval - tk->xtime_interval;
+	tk->raw_interval = interval * clock->mult;
+
+	 /* if changing clocks, convert xtime_nsec shift units */
+	if (old_clock) {
+		int shift_change = clock->shift - old_clock->shift;
+		if (shift_change < 0) {
+			tk->tkr_mono.xtime_nsec >>= -shift_change;
+			tk->tkr_raw.xtime_nsec >>= -shift_change;
+		} else {
+			tk->tkr_mono.xtime_nsec <<= shift_change;
+			tk->tkr_raw.xtime_nsec <<= shift_change;
+		}
+	}
+
+	tk->tkr_mono.shift = clock->shift;
+	tk->tkr_raw.shift = clock->shift;
+
+	tk->ntp_error = 0;
+	tk->ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
+	tk->ntp_tick = ntpinterval << tk->ntp_error_shift;
+
+	/*
+	 * The timekeeper keeps its own mult values for the currently
+	 * active clocksource. These value will be adjusted via NTP
+	 * to counteract clock drifting.
+	 */
+	tk->tkr_mono.mult = clock->mult;
+	tk->tkr_raw.mult = clock->mult;
+	tk->ntp_err_mult = 0;
+	tk->skip_second_overflow = 0;
+}
+
+/* Timekeeper helper functions. */
+
+static inline u64 timekeeping_delta_to_ns(const struct tk_read_base *tkr, u64 delta)
+{
+	u64 nsec;
+
+	nsec = delta * tkr->mult + tkr->xtime_nsec;
+	nsec >>= tkr->shift;
+
+	return nsec;
+}
+
+static inline u64 timekeeping_get_ns(const struct tk_read_base *tkr)
+{
+	u64 delta;
+
+	delta = timekeeping_get_delta(tkr);
+	return timekeeping_delta_to_ns(tkr, delta);
+}
+
+static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles)
+{
+	u64 delta;
+
+	/* calculate the delta since the last update_wall_time */
+	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+	return timekeeping_delta_to_ns(tkr, delta);
+}
+
+/**
+ * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
+ * @tkr: Timekeeping readout base from which we take the update
+ * @tkf: Pointer to NMI safe timekeeper
+ *
+ * We want to use this from any context including NMI and tracing /
+ * instrumenting the timekeeping code itself.
+ *
+ * Employ the latch technique; see @raw_write_seqcount_latch.
+ *
+ * So if a NMI hits the update of base[0] then it will use base[1]
+ * which is still consistent. In the worst case this can result is a
+ * slightly wrong timestamp (a few nanoseconds). See
+ * @ktime_get_mono_fast_ns.
+ */
+static void update_fast_timekeeper(const struct tk_read_base *tkr,
+				   struct tk_fast *tkf)
+{
+	struct tk_read_base *base = tkf->base;
+
+	/* Force readers off to base[1] */
+	raw_write_seqcount_latch(&tkf->seq);
+
+	/* Update base[0] */
+	memcpy(base, tkr, sizeof(*base));
+
+	/* Force readers back to base[0] */
+	raw_write_seqcount_latch(&tkf->seq);
+
+	/* Update base[1] */
+	memcpy(base + 1, base, sizeof(*base));
+}
+
+static __always_inline u64 fast_tk_get_delta_ns(struct tk_read_base *tkr)
+{
+	u64 delta, cycles = tk_clock_read(tkr);
+
+	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+	return timekeeping_delta_to_ns(tkr, delta);
+}
+
+static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
+{
+	struct tk_read_base *tkr;
+	unsigned int seq;
+	u64 now;
+
+	do {
+		seq = raw_read_seqcount_latch(&tkf->seq);
+		tkr = tkf->base + (seq & 0x01);
+		now = ktime_to_ns(tkr->base);
+		now += fast_tk_get_delta_ns(tkr);
+	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
+
+	return now;
+}
+
+/**
+ * ktime_get_mono_fast_ns - Fast NMI safe access to clock monotonic
+ *
+ * This timestamp is not guaranteed to be monotonic across an update.
+ * The timestamp is calculated by:
+ *
+ *	now = base_mono + clock_delta * slope
+ *
+ * So if the update lowers the slope, readers who are forced to the
+ * not yet updated second array are still using the old steeper slope.
+ *
+ * tmono
+ * ^
+ * |    o  n
+ * |   o n
+ * |  u
+ * | o
+ * |o
+ * |12345678---> reader order
+ *
+ * o = old slope
+ * u = update
+ * n = new slope
+ *
+ * So reader 6 will observe time going backwards versus reader 5.
+ *
+ * While other CPUs are likely to be able to observe that, the only way
+ * for a CPU local observation is when an NMI hits in the middle of
+ * the update. Timestamps taken from that NMI context might be ahead
+ * of the following timestamps. Callers need to be aware of that and
+ * deal with it.
+ */
+u64 notrace ktime_get_mono_fast_ns(void)
+{
+	return __ktime_get_fast_ns(&tk_fast_mono);
+}
+EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);
+
+/**
+ * ktime_get_raw_fast_ns - Fast NMI safe access to clock monotonic raw
+ *
+ * Contrary to ktime_get_mono_fast_ns() this is always correct because the
+ * conversion factor is not affected by NTP/PTP correction.
+ */
+u64 notrace ktime_get_raw_fast_ns(void)
+{
+	return __ktime_get_fast_ns(&tk_fast_raw);
+}
+EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
+
+/**
+ * ktime_get_boot_fast_ns - NMI safe and fast access to boot clock.
+ *
+ * To keep it NMI safe since we're accessing from tracing, we're not using a
+ * separate timekeeper with updates to monotonic clock and boot offset
+ * protected with seqcounts. This has the following minor side effects:
+ *
+ * (1) Its possible that a timestamp be taken after the boot offset is updated
+ * but before the timekeeper is updated. If this happens, the new boot offset
+ * is added to the old timekeeping making the clock appear to update slightly
+ * earlier:
+ *    CPU 0                                        CPU 1
+ *    timekeeping_inject_sleeptime64()
+ *    __timekeeping_inject_sleeptime(tk, delta);
+ *                                                 timestamp();
+ *    timekeeping_update(tk, TK_CLEAR_NTP...);
+ *
+ * (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
+ * partially updated.  Since the tk->offs_boot update is a rare event, this
+ * should be a rare occurrence which postprocessing should be able to handle.
+ *
+ * The caveats vs. timestamp ordering as documented for ktime_get_mono_fast_ns()
+ * apply as well.
+ */
+u64 notrace ktime_get_boot_fast_ns(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_boot)));
+}
+EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);
+
+/**
+ * ktime_get_tai_fast_ns - NMI safe and fast access to tai clock.
+ *
+ * The same limitations as described for ktime_get_boot_fast_ns() apply. The
+ * mono time and the TAI offset are not read atomically which may yield wrong
+ * readouts. However, an update of the TAI offset is an rare event e.g., caused
+ * by settime or adjtimex with an offset. The user of this function has to deal
+ * with the possibility of wrong timestamps in post processing.
+ */
+u64 notrace ktime_get_tai_fast_ns(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	return (ktime_get_mono_fast_ns() + ktime_to_ns(data_race(tk->offs_tai)));
+}
+EXPORT_SYMBOL_GPL(ktime_get_tai_fast_ns);
+
+static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
+{
+	struct tk_read_base *tkr;
+	u64 basem, baser, delta;
+	unsigned int seq;
+
+	do {
+		seq = raw_read_seqcount_latch(&tkf->seq);
+		tkr = tkf->base + (seq & 0x01);
+		basem = ktime_to_ns(tkr->base);
+		baser = ktime_to_ns(tkr->base_real);
+		delta = fast_tk_get_delta_ns(tkr);
+	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
+
+	if (mono)
+		*mono = basem + delta;
+	return baser + delta;
+}
+
+/**
+ * ktime_get_real_fast_ns: - NMI safe and fast access to clock realtime.
+ *
+ * See ktime_get_mono_fast_ns() for documentation of the time stamp ordering.
+ */
+u64 ktime_get_real_fast_ns(void)
+{
+	return __ktime_get_real_fast(&tk_fast_mono, NULL);
+}
+EXPORT_SYMBOL_GPL(ktime_get_real_fast_ns);
+
+/**
+ * ktime_get_fast_timestamps: - NMI safe timestamps
+ * @snapshot:	Pointer to timestamp storage
+ *
+ * Stores clock monotonic, boottime and realtime timestamps.
+ *
+ * Boot time is a racy access on 32bit systems if the sleep time injection
+ * happens late during resume and not in timekeeping_resume(). That could
+ * be avoided by expanding struct tk_read_base with boot offset for 32bit
+ * and adding more overhead to the update. As this is a hard to observe
+ * once per resume event which can be filtered with reasonable effort using
+ * the accurate mono/real timestamps, it's probably not worth the trouble.
+ *
+ * Aside of that it might be possible on 32 and 64 bit to observe the
+ * following when the sleep time injection happens late:
+ *
+ * CPU 0				CPU 1
+ * timekeeping_resume()
+ * ktime_get_fast_timestamps()
+ *	mono, real = __ktime_get_real_fast()
+ *					inject_sleep_time()
+ *					   update boot offset
+ *	boot = mono + bootoffset;
+ *
+ * That means that boot time already has the sleep time adjustment, but
+ * real time does not. On the next readout both are in sync again.
+ *
+ * Preventing this for 64bit is not really feasible without destroying the
+ * careful cache layout of the timekeeper because the sequence count and
+ * struct tk_read_base would then need two cache lines instead of one.
+ *
+ * Access to the time keeper clock source is disabled across the innermost
+ * steps of suspend/resume. The accessors still work, but the timestamps
+ * are frozen until time keeping is resumed which happens very early.
+ *
+ * For regular suspend/resume there is no observable difference vs. sched
+ * clock, but it might affect some of the nasty low level debug printks.
+ *
+ * OTOH, access to sched clock is not guaranteed across suspend/resume on
+ * all systems either so it depends on the hardware in use.
+ *
+ * If that turns out to be a real problem then this could be mitigated by
+ * using sched clock in a similar way as during early boot. But it's not as
+ * trivial as on early boot because it needs some careful protection
+ * against the clock monotonic timestamp jumping backwards on resume.
+ */
+void ktime_get_fast_timestamps(struct ktime_timestamps *snapshot)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	snapshot->real = __ktime_get_real_fast(&tk_fast_mono, &snapshot->mono);
+	snapshot->boot = snapshot->mono + ktime_to_ns(data_race(tk->offs_boot));
+}
+
+/**
+ * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.
+ * @tk: Timekeeper to snapshot.
+ *
+ * It generally is unsafe to access the clocksource after timekeeping has been
+ * suspended, so take a snapshot of the readout base of @tk and use it as the
+ * fast timekeeper's readout base while suspended.  It will return the same
+ * number of cycles every time until timekeeping is resumed at which time the
+ * proper readout base for the fast timekeeper will be restored automatically.
+ */
+static void halt_fast_timekeeper(const struct timekeeper *tk)
+{
+	static struct tk_read_base tkr_dummy;
+	const struct tk_read_base *tkr = &tk->tkr_mono;
+
+	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
+	cycles_at_suspend = tk_clock_read(tkr);
+	tkr_dummy.clock = &dummy_clock;
+	tkr_dummy.base_real = tkr->base + tk->offs_real;
+	update_fast_timekeeper(&tkr_dummy, &tk_fast_mono);
+
+	tkr = &tk->tkr_raw;
+	memcpy(&tkr_dummy, tkr, sizeof(tkr_dummy));
+	tkr_dummy.clock = &dummy_clock;
+	update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
+}
+
+static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
+
+static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
+{
+	raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
+}
+
+/**
+ * pvclock_gtod_register_notifier - register a pvclock timedata update listener
+ * @nb: Pointer to the notifier block to register
+ */
+int pvclock_gtod_register_notifier(struct notifier_block *nb)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+	int ret;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
+	update_pvclock_gtod(tk, true);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
+
+/**
+ * pvclock_gtod_unregister_notifier - unregister a pvclock
+ * timedata update listener
+ * @nb: Pointer to the notifier block to unregister
+ */
+int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
+{
+	unsigned long flags;
+	int ret;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
+
+/*
+ * tk_update_leap_state - helper to update the next_leap_ktime
+ */
+static inline void tk_update_leap_state(struct timekeeper *tk)
+{
+	tk->next_leap_ktime = ntp_get_next_leap();
+	if (tk->next_leap_ktime != KTIME_MAX)
+		/* Convert to monotonic time */
+		tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
+}
+
+/*
+ * Update the ktime_t based scalar nsec members of the timekeeper
+ */
+static inline void tk_update_ktime_data(struct timekeeper *tk)
+{
+	u64 seconds;
+	u32 nsec;
+
+	/*
+	 * The xtime based monotonic readout is:
+	 *	nsec = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec + now();
+	 * The ktime based monotonic readout is:
+	 *	nsec = base_mono + now();
+	 * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec
+	 */
+	seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
+	nsec = (u32) tk->wall_to_monotonic.tv_nsec;
+	tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
+
+	/*
+	 * The sum of the nanoseconds portions of xtime and
+	 * wall_to_monotonic can be greater/equal one second. Take
+	 * this into account before updating tk->ktime_sec.
+	 */
+	nsec += (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
+	if (nsec >= NSEC_PER_SEC)
+		seconds++;
+	tk->ktime_sec = seconds;
+
+	/* Update the monotonic raw base */
+	tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
+}
+
+/* must hold timekeeper_lock */
+static void timekeeping_update(struct timekeeper *tk, unsigned int action)
+{
+	if (action & TK_CLEAR_NTP) {
+		tk->ntp_error = 0;
+		ntp_clear();
+	}
+
+	tk_update_leap_state(tk);
+	tk_update_ktime_data(tk);
+
+	update_vsyscall(tk);
+	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+
+	tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
+	update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
+	update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
+
+	if (action & TK_CLOCK_WAS_SET)
+		tk->clock_was_set_seq++;
+	/*
+	 * The mirroring of the data to the shadow-timekeeper needs
+	 * to happen last here to ensure we don't over-write the
+	 * timekeeper structure on the next update with stale data
+	 */
+	if (action & TK_MIRROR)
+		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
+		       sizeof(tk_core.timekeeper));
+}
+
+/**
+ * timekeeping_forward_now - update clock to the current time
+ * @tk:		Pointer to the timekeeper to update
+ *
+ * Forward the current clock to update its state since the last call to
+ * update_wall_time(). This is useful before significant clock changes,
+ * as it avoids having to deal with this time offset explicitly.
+ */
+static void timekeeping_forward_now(struct timekeeper *tk)
+{
+	u64 cycle_now, delta;
+
+	cycle_now = tk_clock_read(&tk->tkr_mono);
+	delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
+	tk->tkr_mono.cycle_last = cycle_now;
+	tk->tkr_raw.cycle_last  = cycle_now;
+
+	tk->tkr_mono.xtime_nsec += delta * tk->tkr_mono.mult;
+	tk->tkr_raw.xtime_nsec += delta * tk->tkr_raw.mult;
+
+	tk_normalize_xtime(tk);
+}
+
+/**
+ * ktime_get_real_ts64 - Returns the time of day in a timespec64.
+ * @ts:		pointer to the timespec to be set
+ *
+ * Returns the time of day in a timespec64 (WARN if suspended).
+ */
+void ktime_get_real_ts64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		ts->tv_sec = tk->xtime_sec;
+		nsecs = timekeeping_get_ns(&tk->tkr_mono);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	ts->tv_nsec = 0;
+	timespec64_add_ns(ts, nsecs);
+}
+EXPORT_SYMBOL(ktime_get_real_ts64);
+
+ktime_t ktime_get(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base;
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		base = tk->tkr_mono.base;
+		nsecs = timekeeping_get_ns(&tk->tkr_mono);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ktime_add_ns(base, nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get);
+
+u32 ktime_get_resolution_ns(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	u32 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		nsecs = tk->tkr_mono.mult >> tk->tkr_mono.shift;
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return nsecs;
+}
+EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
+
+static ktime_t *offsets[TK_OFFS_MAX] = {
+	[TK_OFFS_REAL]	= &tk_core.timekeeper.offs_real,
+	[TK_OFFS_BOOT]	= &tk_core.timekeeper.offs_boot,
+	[TK_OFFS_TAI]	= &tk_core.timekeeper.offs_tai,
+};
+
+ktime_t ktime_get_with_offset(enum tk_offsets offs)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base, *offset = offsets[offs];
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		base = ktime_add(tk->tkr_mono.base, *offset);
+		nsecs = timekeeping_get_ns(&tk->tkr_mono);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ktime_add_ns(base, nsecs);
+
+}
+EXPORT_SYMBOL_GPL(ktime_get_with_offset);
+
+ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base, *offset = offsets[offs];
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		base = ktime_add(tk->tkr_mono.base, *offset);
+		nsecs = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ktime_add_ns(base, nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get_coarse_with_offset);
+
+/**
+ * ktime_mono_to_any() - convert monotonic time to any other time
+ * @tmono:	time to convert.
+ * @offs:	which offset to use
+ */
+ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
+{
+	ktime_t *offset = offsets[offs];
+	unsigned int seq;
+	ktime_t tconv;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		tconv = ktime_add(tmono, *offset);
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return tconv;
+}
+EXPORT_SYMBOL_GPL(ktime_mono_to_any);
+
+/**
+ * ktime_get_raw - Returns the raw monotonic time in ktime_t format
+ */
+ktime_t ktime_get_raw(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base;
+	u64 nsecs;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		base = tk->tkr_raw.base;
+		nsecs = timekeeping_get_ns(&tk->tkr_raw);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ktime_add_ns(base, nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get_raw);
+
+/**
+ * ktime_get_ts64 - get the monotonic clock in timespec64 format
+ * @ts:		pointer to timespec variable
+ *
+ * The function calculates the monotonic clock from the realtime
+ * clock and the wall_to_monotonic offset and stores the result
+ * in normalized timespec64 format in the variable pointed to by @ts.
+ */
+void ktime_get_ts64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct timespec64 tomono;
+	unsigned int seq;
+	u64 nsec;
+
+	WARN_ON(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		ts->tv_sec = tk->xtime_sec;
+		nsec = timekeeping_get_ns(&tk->tkr_mono);
+		tomono = tk->wall_to_monotonic;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	ts->tv_sec += tomono.tv_sec;
+	ts->tv_nsec = 0;
+	timespec64_add_ns(ts, nsec + tomono.tv_nsec);
+}
+EXPORT_SYMBOL_GPL(ktime_get_ts64);
+
+/**
+ * ktime_get_seconds - Get the seconds portion of CLOCK_MONOTONIC
+ *
+ * Returns the seconds portion of CLOCK_MONOTONIC with a single non
+ * serialized read. tk->ktime_sec is of type 'unsigned long' so this
+ * works on both 32 and 64 bit systems. On 32 bit systems the readout
+ * covers ~136 years of uptime which should be enough to prevent
+ * premature wrap arounds.
+ */
+time64_t ktime_get_seconds(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	WARN_ON(timekeeping_suspended);
+	return tk->ktime_sec;
+}
+EXPORT_SYMBOL_GPL(ktime_get_seconds);
+
+/**
+ * ktime_get_real_seconds - Get the seconds portion of CLOCK_REALTIME
+ *
+ * Returns the wall clock seconds since 1970.
+ *
+ * For 64bit systems the fast access to tk->xtime_sec is preserved. On
+ * 32bit systems the access must be protected with the sequence
+ * counter to provide "atomic" access to the 64bit tk->xtime_sec
+ * value.
+ */
+time64_t ktime_get_real_seconds(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	time64_t seconds;
+	unsigned int seq;
+
+	if (IS_ENABLED(CONFIG_64BIT))
+		return tk->xtime_sec;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		seconds = tk->xtime_sec;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return seconds;
+}
+EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
+
+/**
+ * __ktime_get_real_seconds - The same as ktime_get_real_seconds
+ * but without the sequence counter protect. This internal function
+ * is called just when timekeeping lock is already held.
+ */
+noinstr time64_t __ktime_get_real_seconds(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	return tk->xtime_sec;
+}
+
+/**
+ * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
+ * @systime_snapshot:	pointer to struct receiving the system time snapshot
+ */
+void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base_raw;
+	ktime_t base_real;
+	u64 nsec_raw;
+	u64 nsec_real;
+	u64 now;
+
+	WARN_ON_ONCE(timekeeping_suspended);
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		now = tk_clock_read(&tk->tkr_mono);
+		systime_snapshot->cs_id = tk->tkr_mono.clock->id;
+		systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
+		systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
+		base_real = ktime_add(tk->tkr_mono.base,
+				      tk_core.timekeeper.offs_real);
+		base_raw = tk->tkr_raw.base;
+		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
+		nsec_raw  = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	systime_snapshot->cycles = now;
+	systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
+	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
+}
+EXPORT_SYMBOL_GPL(ktime_get_snapshot);
+
+/* Scale base by mult/div checking for overflow */
+static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
+{
+	u64 tmp, rem;
+
+	tmp = div64_u64_rem(*base, div, &rem);
+
+	if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
+	    ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
+		return -EOVERFLOW;
+	tmp *= mult;
+
+	rem = div64_u64(rem * mult, div);
+	*base = tmp + rem;
+	return 0;
+}
+
+/**
+ * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
+ * @history:			Snapshot representing start of history
+ * @partial_history_cycles:	Cycle offset into history (fractional part)
+ * @total_history_cycles:	Total history length in cycles
+ * @discontinuity:		True indicates clock was set on history period
+ * @ts:				Cross timestamp that should be adjusted using
+ *	partial/total ratio
+ *
+ * Helper function used by get_device_system_crosststamp() to correct the
+ * crosstimestamp corresponding to the start of the current interval to the
+ * system counter value (timestamp point) provided by the driver. The
+ * total_history_* quantities are the total history starting at the provided
+ * reference point and ending at the start of the current interval. The cycle
+ * count between the driver timestamp point and the start of the current
+ * interval is partial_history_cycles.
+ */
+static int adjust_historical_crosststamp(struct system_time_snapshot *history,
+					 u64 partial_history_cycles,
+					 u64 total_history_cycles,
+					 bool discontinuity,
+					 struct system_device_crosststamp *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	u64 corr_raw, corr_real;
+	bool interp_forward;
+	int ret;
+
+	if (total_history_cycles == 0 || partial_history_cycles == 0)
+		return 0;
+
+	/* Interpolate shortest distance from beginning or end of history */
+	interp_forward = partial_history_cycles > total_history_cycles / 2;
+	partial_history_cycles = interp_forward ?
+		total_history_cycles - partial_history_cycles :
+		partial_history_cycles;
+
+	/*
+	 * Scale the monotonic raw time delta by:
+	 *	partial_history_cycles / total_history_cycles
+	 */
+	corr_raw = (u64)ktime_to_ns(
+		ktime_sub(ts->sys_monoraw, history->raw));
+	ret = scale64_check_overflow(partial_history_cycles,
+				     total_history_cycles, &corr_raw);
+	if (ret)
+		return ret;
+
+	/*
+	 * If there is a discontinuity in the history, scale monotonic raw
+	 *	correction by:
+	 *	mult(real)/mult(raw) yielding the realtime correction
+	 * Otherwise, calculate the realtime correction similar to monotonic
+	 *	raw calculation
+	 */
+	if (discontinuity) {
+		corr_real = mul_u64_u32_div
+			(corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
+	} else {
+		corr_real = (u64)ktime_to_ns(
+			ktime_sub(ts->sys_realtime, history->real));
+		ret = scale64_check_overflow(partial_history_cycles,
+					     total_history_cycles, &corr_real);
+		if (ret)
+			return ret;
+	}
+
+	/* Fixup monotonic raw and real time time values */
+	if (interp_forward) {
+		ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
+		ts->sys_realtime = ktime_add_ns(history->real, corr_real);
+	} else {
+		ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
+		ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
+	}
+
+	return 0;
+}
+
+/*
+ * cycle_between - true if test occurs chronologically between before and after
+ */
+static bool cycle_between(u64 before, u64 test, u64 after)
+{
+	if (test > before && test < after)
+		return true;
+	if (test < before && before > after)
+		return true;
+	return false;
+}
+
+/**
+ * get_device_system_crosststamp - Synchronously capture system/device timestamp
+ * @get_time_fn:	Callback to get simultaneous device time and
+ *	system counter from the device driver
+ * @ctx:		Context passed to get_time_fn()
+ * @history_begin:	Historical reference point used to interpolate system
+ *	time when counter provided by the driver is before the current interval
+ * @xtstamp:		Receives simultaneously captured system and device time
+ *
+ * Reads a timestamp from a device and correlates it to system time
+ */
+int get_device_system_crosststamp(int (*get_time_fn)
+				  (ktime_t *device_time,
+				   struct system_counterval_t *sys_counterval,
+				   void *ctx),
+				  void *ctx,
+				  struct system_time_snapshot *history_begin,
+				  struct system_device_crosststamp *xtstamp)
+{
+	struct system_counterval_t system_counterval;
+	struct timekeeper *tk = &tk_core.timekeeper;
+	u64 cycles, now, interval_start;
+	unsigned int clock_was_set_seq = 0;
+	ktime_t base_real, base_raw;
+	u64 nsec_real, nsec_raw;
+	u8 cs_was_changed_seq;
+	unsigned int seq;
+	bool do_interp;
+	int ret;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		/*
+		 * Try to synchronously capture device time and a system
+		 * counter value calling back into the device driver
+		 */
+		ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
+		if (ret)
+			return ret;
+
+		/*
+		 * Verify that the clocksource associated with the captured
+		 * system counter value is the same as the currently installed
+		 * timekeeper clocksource
+		 */
+		if (tk->tkr_mono.clock != system_counterval.cs)
+			return -ENODEV;
+		cycles = system_counterval.cycles;
+
+		/*
+		 * Check whether the system counter value provided by the
+		 * device driver is on the current timekeeping interval.
+		 */
+		now = tk_clock_read(&tk->tkr_mono);
+		interval_start = tk->tkr_mono.cycle_last;
+		if (!cycle_between(interval_start, cycles, now)) {
+			clock_was_set_seq = tk->clock_was_set_seq;
+			cs_was_changed_seq = tk->cs_was_changed_seq;
+			cycles = interval_start;
+			do_interp = true;
+		} else {
+			do_interp = false;
+		}
+
+		base_real = ktime_add(tk->tkr_mono.base,
+				      tk_core.timekeeper.offs_real);
+		base_raw = tk->tkr_raw.base;
+
+		nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
+						     system_counterval.cycles);
+		nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
+						    system_counterval.cycles);
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
+	xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
+
+	/*
+	 * Interpolate if necessary, adjusting back from the start of the
+	 * current interval
+	 */
+	if (do_interp) {
+		u64 partial_history_cycles, total_history_cycles;
+		bool discontinuity;
+
+		/*
+		 * Check that the counter value occurs after the provided
+		 * history reference and that the history doesn't cross a
+		 * clocksource change
+		 */
+		if (!history_begin ||
+		    !cycle_between(history_begin->cycles,
+				   system_counterval.cycles, cycles) ||
+		    history_begin->cs_was_changed_seq != cs_was_changed_seq)
+			return -EINVAL;
+		partial_history_cycles = cycles - system_counterval.cycles;
+		total_history_cycles = cycles - history_begin->cycles;
+		discontinuity =
+			history_begin->clock_was_set_seq != clock_was_set_seq;
+
+		ret = adjust_historical_crosststamp(history_begin,
+						    partial_history_cycles,
+						    total_history_cycles,
+						    discontinuity, xtstamp);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
+
+/**
+ * do_settimeofday64 - Sets the time of day.
+ * @ts:     pointer to the timespec64 variable containing the new time
+ *
+ * Sets the time of day to the new time and update NTP and notify hrtimers
+ */
+int do_settimeofday64(const struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct timespec64 ts_delta, xt;
+	unsigned long flags;
+	int ret = 0;
+
+	if (!timespec64_valid_settod(ts))
+		return -EINVAL;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	timekeeping_forward_now(tk);
+
+	xt = tk_xtime(tk);
+	ts_delta = timespec64_sub(*ts, xt);
+
+	if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
+
+	tk_set_xtime(tk, ts);
+out:
+	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	/* Signal hrtimers about time change */
+	clock_was_set(CLOCK_SET_WALL);
+
+	if (!ret) {
+		audit_tk_injoffset(ts_delta);
+		add_device_randomness(ts, sizeof(*ts));
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(do_settimeofday64);
+
+/**
+ * timekeeping_inject_offset - Adds or subtracts from the current time.
+ * @ts:		Pointer to the timespec variable containing the offset
+ *
+ * Adds or subtracts an offset value from the current time.
+ */
+static int timekeeping_inject_offset(const struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+	struct timespec64 tmp;
+	int ret = 0;
+
+	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
+		return -EINVAL;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	timekeeping_forward_now(tk);
+
+	/* Make sure the proposed value is valid */
+	tmp = timespec64_add(tk_xtime(tk), *ts);
+	if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||
+	    !timespec64_valid_settod(&tmp)) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	tk_xtime_add(tk, ts);
+	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));
+
+error: /* even if we error out, we forwarded the time, so call update */
+	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	/* Signal hrtimers about time change */
+	clock_was_set(CLOCK_SET_WALL);
+
+	return ret;
+}
+
+/*
+ * Indicates if there is an offset between the system clock and the hardware
+ * clock/persistent clock/rtc.
+ */
+int persistent_clock_is_local;
+
+/*
+ * Adjust the time obtained from the CMOS to be UTC time instead of
+ * local time.
+ *
+ * This is ugly, but preferable to the alternatives.  Otherwise we
+ * would either need to write a program to do it in /etc/rc (and risk
+ * confusion if the program gets run more than once; it would also be
+ * hard to make the program warp the clock precisely n hours)  or
+ * compile in the timezone information into the kernel.  Bad, bad....
+ *
+ *						- TYT, 1992-01-01
+ *
+ * The best thing to do is to keep the CMOS clock in universal time (UTC)
+ * as real UNIX machines always do it. This avoids all headaches about
+ * daylight saving times and warping kernel clocks.
+ */
+void timekeeping_warp_clock(void)
+{
+	if (sys_tz.tz_minuteswest != 0) {
+		struct timespec64 adjust;
+
+		persistent_clock_is_local = 1;
+		adjust.tv_sec = sys_tz.tz_minuteswest * 60;
+		adjust.tv_nsec = 0;
+		timekeeping_inject_offset(&adjust);
+	}
+}
+
+/*
+ * __timekeeping_set_tai_offset - Sets the TAI offset from UTC and monotonic
+ */
+static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset)
+{
+	tk->tai_offset = tai_offset;
+	tk->offs_tai = ktime_add(tk->offs_real, ktime_set(tai_offset, 0));
+}
+
+/*
+ * change_clocksource - Swaps clocksources if a new one is available
+ *
+ * Accumulates current time interval and initializes new clocksource
+ */
+static int change_clocksource(void *data)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct clocksource *new, *old = NULL;
+	unsigned long flags;
+	bool change = false;
+
+	new = (struct clocksource *) data;
+
+	/*
+	 * If the cs is in module, get a module reference. Succeeds
+	 * for built-in code (owner == NULL) as well.
+	 */
+	if (try_module_get(new->owner)) {
+		if (!new->enable || new->enable(new) == 0)
+			change = true;
+		else
+			module_put(new->owner);
+	}
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	timekeeping_forward_now(tk);
+
+	if (change) {
+		old = tk->tkr_mono.clock;
+		tk_setup_internals(tk, new);
+	}
+
+	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	if (old) {
+		if (old->disable)
+			old->disable(old);
+
+		module_put(old->owner);
+	}
+
+	return 0;
+}
+
+/**
+ * timekeeping_notify - Install a new clock source
+ * @clock:		pointer to the clock source
+ *
+ * This function is called from clocksource.c after a new, better clock
+ * source has been registered. The caller holds the clocksource_mutex.
+ */
+int timekeeping_notify(struct clocksource *clock)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+
+	if (tk->tkr_mono.clock == clock)
+		return 0;
+	stop_machine(change_clocksource, clock, NULL);
+	tick_clock_notify();
+	return tk->tkr_mono.clock == clock ? 0 : -1;
+}
+
+/**
+ * ktime_get_raw_ts64 - Returns the raw monotonic time in a timespec
+ * @ts:		pointer to the timespec64 to be set
+ *
+ * Returns the raw monotonic time (completely un-modified by ntp)
+ */
+void ktime_get_raw_ts64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	u64 nsecs;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		ts->tv_sec = tk->raw_sec;
+		nsecs = timekeeping_get_ns(&tk->tkr_raw);
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	ts->tv_nsec = 0;
+	timespec64_add_ns(ts, nsecs);
+}
+EXPORT_SYMBOL(ktime_get_raw_ts64);
+
+
+/**
+ * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
+ */
+int timekeeping_valid_for_hres(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	int ret;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		ret = tk->tkr_mono.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ret;
+}
+
+/**
+ * timekeeping_max_deferment - Returns max time the clocksource can be deferred
+ */
+u64 timekeeping_max_deferment(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	u64 ret;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		ret = tk->tkr_mono.clock->max_idle_ns;
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return ret;
+}
+
+/**
+ * read_persistent_clock64 -  Return time from the persistent clock.
+ * @ts: Pointer to the storage for the readout value
+ *
+ * Weak dummy function for arches that do not yet support it.
+ * Reads the time from the battery backed persistent clock.
+ * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
+ *
+ *  XXX - Do be sure to remove it once all arches implement it.
+ */
+void __weak read_persistent_clock64(struct timespec64 *ts)
+{
+	ts->tv_sec = 0;
+	ts->tv_nsec = 0;
+}
+
+/**
+ * read_persistent_wall_and_boot_offset - Read persistent clock, and also offset
+ *                                        from the boot.
+ * @wall_time:	  current time as returned by persistent clock
+ * @boot_offset:  offset that is defined as wall_time - boot_time
+ *
+ * Weak dummy function for arches that do not yet support it.
+ *
+ * The default function calculates offset based on the current value of
+ * local_clock(). This way architectures that support sched_clock() but don't
+ * support dedicated boot time clock will provide the best estimate of the
+ * boot time.
+ */
+void __weak __init
+read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
+				     struct timespec64 *boot_offset)
+{
+	read_persistent_clock64(wall_time);
+	*boot_offset = ns_to_timespec64(local_clock());
+}
+
+/*
+ * Flag reflecting whether timekeeping_resume() has injected sleeptime.
+ *
+ * The flag starts of false and is only set when a suspend reaches
+ * timekeeping_suspend(), timekeeping_resume() sets it to false when the
+ * timekeeper clocksource is not stopping across suspend and has been
+ * used to update sleep time. If the timekeeper clocksource has stopped
+ * then the flag stays true and is used by the RTC resume code to decide
+ * whether sleeptime must be injected and if so the flag gets false then.
+ *
+ * If a suspend fails before reaching timekeeping_resume() then the flag
+ * stays false and prevents erroneous sleeptime injection.
+ */
+static bool suspend_timing_needed;
+
+/* Flag for if there is a persistent clock on this platform */
+static bool persistent_clock_exists;
+
+/*
+ * timekeeping_init - Initializes the clocksource and common timekeeping values
+ */
+void __init timekeeping_init(void)
+{
+	struct timespec64 wall_time, boot_offset, wall_to_mono;
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct clocksource *clock;
+	unsigned long flags;
+
+	read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
+	if (timespec64_valid_settod(&wall_time) &&
+	    timespec64_to_ns(&wall_time) > 0) {
+		persistent_clock_exists = true;
+	} else if (timespec64_to_ns(&wall_time) != 0) {
+		pr_warn("Persistent clock returned invalid value");
+		wall_time = (struct timespec64){0};
+	}
+
+	if (timespec64_compare(&wall_time, &boot_offset) < 0)
+		boot_offset = (struct timespec64){0};
+
+	/*
+	 * We want set wall_to_mono, so the following is true:
+	 * wall time + wall_to_mono = boot time
+	 */
+	wall_to_mono = timespec64_sub(boot_offset, wall_time);
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+	ntp_init();
+
+	clock = clocksource_default_clock();
+	if (clock->enable)
+		clock->enable(clock);
+	tk_setup_internals(tk, clock);
+
+	tk_set_xtime(tk, &wall_time);
+	tk->raw_sec = 0;
+
+	tk_set_wall_to_mono(tk, wall_to_mono);
+
+	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+}
+
+/* time in seconds when suspend began for persistent clock */
+static struct timespec64 timekeeping_suspend_time;
+
+/**
+ * __timekeeping_inject_sleeptime - Internal function to add sleep interval
+ * @tk:		Pointer to the timekeeper to be updated
+ * @delta:	Pointer to the delta value in timespec64 format
+ *
+ * Takes a timespec offset measuring a suspend interval and properly
+ * adds the sleep offset to the timekeeping variables.
+ */
+static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
+					   const struct timespec64 *delta)
+{
+	if (!timespec64_valid_strict(delta)) {
+		printk_deferred(KERN_WARNING
+				"__timekeeping_inject_sleeptime: Invalid "
+				"sleep delta value!\n");
+		return;
+	}
+	tk_xtime_add(tk, delta);
+	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
+	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
+	tk_debug_account_sleep_time(delta);
+}
+
+#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
+/*
+ * We have three kinds of time sources to use for sleep time
+ * injection, the preference order is:
+ * 1) non-stop clocksource
+ * 2) persistent clock (ie: RTC accessible when irqs are off)
+ * 3) RTC
+ *
+ * 1) and 2) are used by timekeeping, 3) by RTC subsystem.
+ * If system has neither 1) nor 2), 3) will be used finally.
+ *
+ *
+ * If timekeeping has injected sleeptime via either 1) or 2),
+ * 3) becomes needless, so in this case we don't need to call
+ * rtc_resume(), and this is what timekeeping_rtc_skipresume()
+ * means.
+ */
+bool timekeeping_rtc_skipresume(void)
+{
+	return !suspend_timing_needed;
+}
+
+/*
+ * 1) can be determined whether to use or not only when doing
+ * timekeeping_resume() which is invoked after rtc_suspend(),
+ * so we can't skip rtc_suspend() surely if system has 1).
+ *
+ * But if system has 2), 2) will definitely be used, so in this
+ * case we don't need to call rtc_suspend(), and this is what
+ * timekeeping_rtc_skipsuspend() means.
+ */
+bool timekeeping_rtc_skipsuspend(void)
+{
+	return persistent_clock_exists;
+}
+
+/**
+ * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
+ * @delta: pointer to a timespec64 delta value
+ *
+ * This hook is for architectures that cannot support read_persistent_clock64
+ * because their RTC/persistent clock is only accessible when irqs are enabled.
+ * and also don't have an effective nonstop clocksource.
+ *
+ * This function should only be called by rtc_resume(), and allows
+ * a suspend offset to be injected into the timekeeping values.
+ */
+void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	suspend_timing_needed = false;
+
+	timekeeping_forward_now(tk);
+
+	__timekeeping_inject_sleeptime(tk, delta);
+
+	timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	/* Signal hrtimers about time change */
+	clock_was_set(CLOCK_SET_WALL | CLOCK_SET_BOOT);
+}
+#endif
+
+/**
+ * timekeeping_resume - Resumes the generic timekeeping subsystem.
+ */
+void timekeeping_resume(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct clocksource *clock = tk->tkr_mono.clock;
+	unsigned long flags;
+	struct timespec64 ts_new, ts_delta;
+	u64 cycle_now, nsec;
+	bool inject_sleeptime = false;
+
+	read_persistent_clock64(&ts_new);
+
+	clockevents_resume();
+	clocksource_resume();
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	/*
+	 * After system resumes, we need to calculate the suspended time and
+	 * compensate it for the OS time. There are 3 sources that could be
+	 * used: Nonstop clocksource during suspend, persistent clock and rtc
+	 * device.
+	 *
+	 * One specific platform may have 1 or 2 or all of them, and the
+	 * preference will be:
+	 *	suspend-nonstop clocksource -> persistent clock -> rtc
+	 * The less preferred source will only be tried if there is no better
+	 * usable source. The rtc part is handled separately in rtc core code.
+	 */
+	cycle_now = tk_clock_read(&tk->tkr_mono);
+	nsec = clocksource_stop_suspend_timing(clock, cycle_now);
+	if (nsec > 0) {
+		ts_delta = ns_to_timespec64(nsec);
+		inject_sleeptime = true;
+	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
+		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
+		inject_sleeptime = true;
+	}
+
+	if (inject_sleeptime) {
+		suspend_timing_needed = false;
+		__timekeeping_inject_sleeptime(tk, &ts_delta);
+	}
+
+	/* Re-base the last cycle value */
+	tk->tkr_mono.cycle_last = cycle_now;
+	tk->tkr_raw.cycle_last  = cycle_now;
+
+	tk->ntp_error = 0;
+	timekeeping_suspended = 0;
+	timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	touch_softlockup_watchdog();
+
+	/* Resume the clockevent device(s) and hrtimers */
+	tick_resume();
+	/* Notify timerfd as resume is equivalent to clock_was_set() */
+	timerfd_resume();
+}
+
+int timekeeping_suspend(void)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+	struct timespec64		delta, delta_delta;
+	static struct timespec64	old_delta;
+	struct clocksource *curr_clock;
+	u64 cycle_now;
+
+	read_persistent_clock64(&timekeeping_suspend_time);
+
+	/*
+	 * On some systems the persistent_clock can not be detected at
+	 * timekeeping_init by its return value, so if we see a valid
+	 * value returned, update the persistent_clock_exists flag.
+	 */
+	if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
+		persistent_clock_exists = true;
+
+	suspend_timing_needed = true;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+	timekeeping_forward_now(tk);
+	timekeeping_suspended = 1;
+
+	/*
+	 * Since we've called forward_now, cycle_last stores the value
+	 * just read from the current clocksource. Save this to potentially
+	 * use in suspend timing.
+	 */
+	curr_clock = tk->tkr_mono.clock;
+	cycle_now = tk->tkr_mono.cycle_last;
+	clocksource_start_suspend_timing(curr_clock, cycle_now);
+
+	if (persistent_clock_exists) {
+		/*
+		 * To avoid drift caused by repeated suspend/resumes,
+		 * which each can add ~1 second drift error,
+		 * try to compensate so the difference in system time
+		 * and persistent_clock time stays close to constant.
+		 */
+		delta = timespec64_sub(tk_xtime(tk), timekeeping_suspend_time);
+		delta_delta = timespec64_sub(delta, old_delta);
+		if (abs(delta_delta.tv_sec) >= 2) {
+			/*
+			 * if delta_delta is too large, assume time correction
+			 * has occurred and set old_delta to the current delta.
+			 */
+			old_delta = delta;
+		} else {
+			/* Otherwise try to adjust old_system to compensate */
+			timekeeping_suspend_time =
+				timespec64_add(timekeeping_suspend_time, delta_delta);
+		}
+	}
+
+	timekeeping_update(tk, TK_MIRROR);
+	halt_fast_timekeeper(tk);
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	tick_suspend();
+	clocksource_suspend();
+	clockevents_suspend();
+
+	return 0;
+}
+
+/* sysfs resume/suspend bits for timekeeping */
+static struct syscore_ops timekeeping_syscore_ops = {
+	.resume		= timekeeping_resume,
+	.suspend	= timekeeping_suspend,
+};
+
+static int __init timekeeping_init_ops(void)
+{
+	register_syscore_ops(&timekeeping_syscore_ops);
+	return 0;
+}
+device_initcall(timekeeping_init_ops);
+
+/*
+ * Apply a multiplier adjustment to the timekeeper
+ */
+static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
+							 s64 offset,
+							 s32 mult_adj)
+{
+	s64 interval = tk->cycle_interval;
+
+	if (mult_adj == 0) {
+		return;
+	} else if (mult_adj == -1) {
+		interval = -interval;
+		offset = -offset;
+	} else if (mult_adj != 1) {
+		interval *= mult_adj;
+		offset *= mult_adj;
+	}
+
+	/*
+	 * So the following can be confusing.
+	 *
+	 * To keep things simple, lets assume mult_adj == 1 for now.
+	 *
+	 * When mult_adj != 1, remember that the interval and offset values
+	 * have been appropriately scaled so the math is the same.
+	 *
+	 * The basic idea here is that we're increasing the multiplier
+	 * by one, this causes the xtime_interval to be incremented by
+	 * one cycle_interval. This is because:
+	 *	xtime_interval = cycle_interval * mult
+	 * So if mult is being incremented by one:
+	 *	xtime_interval = cycle_interval * (mult + 1)
+	 * Its the same as:
+	 *	xtime_interval = (cycle_interval * mult) + cycle_interval
+	 * Which can be shortened to:
+	 *	xtime_interval += cycle_interval
+	 *
+	 * So offset stores the non-accumulated cycles. Thus the current
+	 * time (in shifted nanoseconds) is:
+	 *	now = (offset * adj) + xtime_nsec
+	 * Now, even though we're adjusting the clock frequency, we have
+	 * to keep time consistent. In other words, we can't jump back
+	 * in time, and we also want to avoid jumping forward in time.
+	 *
+	 * So given the same offset value, we need the time to be the same
+	 * both before and after the freq adjustment.
+	 *	now = (offset * adj_1) + xtime_nsec_1
+	 *	now = (offset * adj_2) + xtime_nsec_2
+	 * So:
+	 *	(offset * adj_1) + xtime_nsec_1 =
+	 *		(offset * adj_2) + xtime_nsec_2
+	 * And we know:
+	 *	adj_2 = adj_1 + 1
+	 * So:
+	 *	(offset * adj_1) + xtime_nsec_1 =
+	 *		(offset * (adj_1+1)) + xtime_nsec_2
+	 *	(offset * adj_1) + xtime_nsec_1 =
+	 *		(offset * adj_1) + offset + xtime_nsec_2
+	 * Canceling the sides:
+	 *	xtime_nsec_1 = offset + xtime_nsec_2
+	 * Which gives us:
+	 *	xtime_nsec_2 = xtime_nsec_1 - offset
+	 * Which simplifies to:
+	 *	xtime_nsec -= offset
+	 */
+	if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
+		/* NTP adjustment caused clocksource mult overflow */
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	tk->tkr_mono.mult += mult_adj;
+	tk->xtime_interval += interval;
+	tk->tkr_mono.xtime_nsec -= offset;
+}
+
+/*
+ * Adjust the timekeeper's multiplier to the correct frequency
+ * and also to reduce the accumulated error value.
+ */
+static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
+{
+	u32 mult;
+
+	/*
+	 * Determine the multiplier from the current NTP tick length.
+	 * Avoid expensive division when the tick length doesn't change.
+	 */
+	if (likely(tk->ntp_tick == ntp_tick_length())) {
+		mult = tk->tkr_mono.mult - tk->ntp_err_mult;
+	} else {
+		tk->ntp_tick = ntp_tick_length();
+		mult = div64_u64((tk->ntp_tick >> tk->ntp_error_shift) -
+				 tk->xtime_remainder, tk->cycle_interval);
+	}
+
+	/*
+	 * If the clock is behind the NTP time, increase the multiplier by 1
+	 * to catch up with it. If it's ahead and there was a remainder in the
+	 * tick division, the clock will slow down. Otherwise it will stay
+	 * ahead until the tick length changes to a non-divisible value.
+	 */
+	tk->ntp_err_mult = tk->ntp_error > 0 ? 1 : 0;
+	mult += tk->ntp_err_mult;
+
+	timekeeping_apply_adjustment(tk, offset, mult - tk->tkr_mono.mult);
+
+	if (unlikely(tk->tkr_mono.clock->maxadj &&
+		(abs(tk->tkr_mono.mult - tk->tkr_mono.clock->mult)
+			> tk->tkr_mono.clock->maxadj))) {
+		printk_once(KERN_WARNING
+			"Adjusting %s more than 11%% (%ld vs %ld)\n",
+			tk->tkr_mono.clock->name, (long)tk->tkr_mono.mult,
+			(long)tk->tkr_mono.clock->mult + tk->tkr_mono.clock->maxadj);
+	}
+
+	/*
+	 * It may be possible that when we entered this function, xtime_nsec
+	 * was very small.  Further, if we're slightly speeding the clocksource
+	 * in the code above, its possible the required corrective factor to
+	 * xtime_nsec could cause it to underflow.
+	 *
+	 * Now, since we have already accumulated the second and the NTP
+	 * subsystem has been notified via second_overflow(), we need to skip
+	 * the next update.
+	 */
+	if (unlikely((s64)tk->tkr_mono.xtime_nsec < 0)) {
+		tk->tkr_mono.xtime_nsec += (u64)NSEC_PER_SEC <<
+							tk->tkr_mono.shift;
+		tk->xtime_sec--;
+		tk->skip_second_overflow = 1;
+	}
+}
+
+/*
+ * accumulate_nsecs_to_secs - Accumulates nsecs into secs
+ *
+ * Helper function that accumulates the nsecs greater than a second
+ * from the xtime_nsec field to the xtime_secs field.
+ * It also calls into the NTP code to handle leapsecond processing.
+ */
+static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
+{
+	u64 nsecps = (u64)NSEC_PER_SEC << tk->tkr_mono.shift;
+	unsigned int clock_set = 0;
+
+	while (tk->tkr_mono.xtime_nsec >= nsecps) {
+		int leap;
+
+		tk->tkr_mono.xtime_nsec -= nsecps;
+		tk->xtime_sec++;
+
+		/*
+		 * Skip NTP update if this second was accumulated before,
+		 * i.e. xtime_nsec underflowed in timekeeping_adjust()
+		 */
+		if (unlikely(tk->skip_second_overflow)) {
+			tk->skip_second_overflow = 0;
+			continue;
+		}
+
+		/* Figure out if its a leap sec and apply if needed */
+		leap = second_overflow(tk->xtime_sec);
+		if (unlikely(leap)) {
+			struct timespec64 ts;
+
+			tk->xtime_sec += leap;
+
+			ts.tv_sec = leap;
+			ts.tv_nsec = 0;
+			tk_set_wall_to_mono(tk,
+				timespec64_sub(tk->wall_to_monotonic, ts));
+
+			__timekeeping_set_tai_offset(tk, tk->tai_offset - leap);
+
+			clock_set = TK_CLOCK_WAS_SET;
+		}
+	}
+	return clock_set;
+}
+
+/*
+ * logarithmic_accumulation - shifted accumulation of cycles
+ *
+ * This functions accumulates a shifted interval of cycles into
+ * a shifted interval nanoseconds. Allows for O(log) accumulation
+ * loop.
+ *
+ * Returns the unconsumed cycles.
+ */
+static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
+				    u32 shift, unsigned int *clock_set)
+{
+	u64 interval = tk->cycle_interval << shift;
+	u64 snsec_per_sec;
+
+	/* If the offset is smaller than a shifted interval, do nothing */
+	if (offset < interval)
+		return offset;
+
+	/* Accumulate one shifted interval */
+	offset -= interval;
+	tk->tkr_mono.cycle_last += interval;
+	tk->tkr_raw.cycle_last  += interval;
+
+	tk->tkr_mono.xtime_nsec += tk->xtime_interval << shift;
+	*clock_set |= accumulate_nsecs_to_secs(tk);
+
+	/* Accumulate raw time */
+	tk->tkr_raw.xtime_nsec += tk->raw_interval << shift;
+	snsec_per_sec = (u64)NSEC_PER_SEC << tk->tkr_raw.shift;
+	while (tk->tkr_raw.xtime_nsec >= snsec_per_sec) {
+		tk->tkr_raw.xtime_nsec -= snsec_per_sec;
+		tk->raw_sec++;
+	}
+
+	/* Accumulate error between NTP and clock interval */
+	tk->ntp_error += tk->ntp_tick << shift;
+	tk->ntp_error -= (tk->xtime_interval + tk->xtime_remainder) <<
+						(tk->ntp_error_shift + shift);
+
+	return offset;
+}
+
+/*
+ * timekeeping_advance - Updates the timekeeper to the current time and
+ * current NTP tick length
+ */
+static bool timekeeping_advance(enum timekeeping_adv_mode mode)
+{
+	struct timekeeper *real_tk = &tk_core.timekeeper;
+	struct timekeeper *tk = &shadow_timekeeper;
+	u64 offset;
+	int shift = 0, maxshift;
+	unsigned int clock_set = 0;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+
+	/* Make sure we're fully resumed: */
+	if (unlikely(timekeeping_suspended))
+		goto out;
+
+	offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
+				   tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
+
+	/* Check if there's really nothing to do */
+	if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK)
+		goto out;
+
+	/* Do some additional sanity checking */
+	timekeeping_check_update(tk, offset);
+
+	/*
+	 * With NO_HZ we may have to accumulate many cycle_intervals
+	 * (think "ticks") worth of time at once. To do this efficiently,
+	 * we calculate the largest doubling multiple of cycle_intervals
+	 * that is smaller than the offset.  We then accumulate that
+	 * chunk in one go, and then try to consume the next smaller
+	 * doubled multiple.
+	 */
+	shift = ilog2(offset) - ilog2(tk->cycle_interval);
+	shift = max(0, shift);
+	/* Bound shift to one less than what overflows tick_length */
+	maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
+	shift = min(shift, maxshift);
+	while (offset >= tk->cycle_interval) {
+		offset = logarithmic_accumulation(tk, offset, shift,
+							&clock_set);
+		if (offset < tk->cycle_interval<<shift)
+			shift--;
+	}
+
+	/* Adjust the multiplier to correct NTP error */
+	timekeeping_adjust(tk, offset);
+
+	/*
+	 * Finally, make sure that after the rounding
+	 * xtime_nsec isn't larger than NSEC_PER_SEC
+	 */
+	clock_set |= accumulate_nsecs_to_secs(tk);
+
+	write_seqcount_begin(&tk_core.seq);
+	/*
+	 * Update the real timekeeper.
+	 *
+	 * We could avoid this memcpy by switching pointers, but that
+	 * requires changes to all other timekeeper usage sites as
+	 * well, i.e. move the timekeeper pointer getter into the
+	 * spinlocked/seqcount protected sections. And we trade this
+	 * memcpy under the tk_core.seq against one before we start
+	 * updating.
+	 */
+	timekeeping_update(tk, clock_set);
+	memcpy(real_tk, tk, sizeof(*tk));
+	/* The memcpy must come last. Do not put anything here! */
+	write_seqcount_end(&tk_core.seq);
+out:
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	return !!clock_set;
+}
+
+/**
+ * update_wall_time - Uses the current clocksource to increment the wall time
+ *
+ */
+void update_wall_time(void)
+{
+	if (timekeeping_advance(TK_ADV_TICK))
+		clock_was_set_delayed();
+}
+
+/**
+ * getboottime64 - Return the real time of system boot.
+ * @ts:		pointer to the timespec64 to be set
+ *
+ * Returns the wall-time of boot in a timespec64.
+ *
+ * This is based on the wall_to_monotonic offset and the total suspend
+ * time. Calls to settimeofday will affect the value returned (which
+ * basically means that however wrong your real time clock is at boot time,
+ * you get the right time here).
+ */
+void getboottime64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	ktime_t t = ktime_sub(tk->offs_real, tk->offs_boot);
+
+	*ts = ktime_to_timespec64(t);
+}
+EXPORT_SYMBOL_GPL(getboottime64);
+
+void ktime_get_coarse_real_ts64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		*ts = tk_xtime(tk);
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+}
+EXPORT_SYMBOL(ktime_get_coarse_real_ts64);
+
+void ktime_get_coarse_ts64(struct timespec64 *ts)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct timespec64 now, mono;
+	unsigned int seq;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		now = tk_xtime(tk);
+		mono = tk->wall_to_monotonic;
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	set_normalized_timespec64(ts, now.tv_sec + mono.tv_sec,
+				now.tv_nsec + mono.tv_nsec);
+}
+EXPORT_SYMBOL(ktime_get_coarse_ts64);
+
+/*
+ * Must hold jiffies_lock
+ */
+void do_timer(unsigned long ticks)
+{
+	jiffies_64 += ticks;
+	calc_global_load();
+}
+
+/**
+ * ktime_get_update_offsets_now - hrtimer helper
+ * @cwsseq:	pointer to check and store the clock was set sequence number
+ * @offs_real:	pointer to storage for monotonic -> realtime offset
+ * @offs_boot:	pointer to storage for monotonic -> boottime offset
+ * @offs_tai:	pointer to storage for monotonic -> clock tai offset
+ *
+ * Returns current monotonic time and updates the offsets if the
+ * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
+ * different.
+ *
+ * Called from hrtimer_interrupt() or retrigger_next_event()
+ */
+ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
+				     ktime_t *offs_boot, ktime_t *offs_tai)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	ktime_t base;
+	u64 nsecs;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+
+		base = tk->tkr_mono.base;
+		nsecs = timekeeping_get_ns(&tk->tkr_mono);
+		base = ktime_add_ns(base, nsecs);
+
+		if (*cwsseq != tk->clock_was_set_seq) {
+			*cwsseq = tk->clock_was_set_seq;
+			*offs_real = tk->offs_real;
+			*offs_boot = tk->offs_boot;
+			*offs_tai = tk->offs_tai;
+		}
+
+		/* Handle leapsecond insertion adjustments */
+		if (unlikely(base >= tk->next_leap_ktime))
+			*offs_real = ktime_sub(tk->offs_real, ktime_set(1, 0));
+
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return base;
+}
+
+/*
+ * timekeeping_validate_timex - Ensures the timex is ok for use in do_adjtimex
+ */
+static int timekeeping_validate_timex(const struct __kernel_timex *txc)
+{
+	if (txc->modes & ADJ_ADJTIME) {
+		/* singleshot must not be used with any other mode bits */
+		if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
+			return -EINVAL;
+		if (!(txc->modes & ADJ_OFFSET_READONLY) &&
+		    !capable(CAP_SYS_TIME))
+			return -EPERM;
+	} else {
+		/* In order to modify anything, you gotta be super-user! */
+		if (txc->modes && !capable(CAP_SYS_TIME))
+			return -EPERM;
+		/*
+		 * if the quartz is off by more than 10% then
+		 * something is VERY wrong!
+		 */
+		if (txc->modes & ADJ_TICK &&
+		    (txc->tick <  900000/USER_HZ ||
+		     txc->tick > 1100000/USER_HZ))
+			return -EINVAL;
+	}
+
+	if (txc->modes & ADJ_SETOFFSET) {
+		/* In order to inject time, you gotta be super-user! */
+		if (!capable(CAP_SYS_TIME))
+			return -EPERM;
+
+		/*
+		 * Validate if a timespec/timeval used to inject a time
+		 * offset is valid.  Offsets can be positive or negative, so
+		 * we don't check tv_sec. The value of the timeval/timespec
+		 * is the sum of its fields,but *NOTE*:
+		 * The field tv_usec/tv_nsec must always be non-negative and
+		 * we can't have more nanoseconds/microseconds than a second.
+		 */
+		if (txc->time.tv_usec < 0)
+			return -EINVAL;
+
+		if (txc->modes & ADJ_NANO) {
+			if (txc->time.tv_usec >= NSEC_PER_SEC)
+				return -EINVAL;
+		} else {
+			if (txc->time.tv_usec >= USEC_PER_SEC)
+				return -EINVAL;
+		}
+	}
+
+	/*
+	 * Check for potential multiplication overflows that can
+	 * only happen on 64-bit systems:
+	 */
+	if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
+		if (LLONG_MIN / PPM_SCALE > txc->freq)
+			return -EINVAL;
+		if (LLONG_MAX / PPM_SCALE < txc->freq)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * random_get_entropy_fallback - Returns the raw clock source value,
+ * used by random.c for platforms with no valid random_get_entropy().
+ */
+unsigned long random_get_entropy_fallback(void)
+{
+	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
+	struct clocksource *clock = READ_ONCE(tkr->clock);
+
+	if (unlikely(timekeeping_suspended || !clock))
+		return 0;
+	return clock->read(clock);
+}
+EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
+
+/**
+ * do_adjtimex() - Accessor function to NTP __do_adjtimex function
+ */
+int do_adjtimex(struct __kernel_timex *txc)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	struct audit_ntp_data ad;
+	bool clock_set = false;
+	struct timespec64 ts;
+	unsigned long flags;
+	s32 orig_tai, tai;
+	int ret;
+
+	/* Validate the data before disabling interrupts */
+	ret = timekeeping_validate_timex(txc);
+	if (ret)
+		return ret;
+	add_device_randomness(txc, sizeof(*txc));
+
+	if (txc->modes & ADJ_SETOFFSET) {
+		struct timespec64 delta;
+		delta.tv_sec  = txc->time.tv_sec;
+		delta.tv_nsec = txc->time.tv_usec;
+		if (!(txc->modes & ADJ_NANO))
+			delta.tv_nsec *= 1000;
+		ret = timekeeping_inject_offset(&delta);
+		if (ret)
+			return ret;
+
+		audit_tk_injoffset(delta);
+	}
+
+	audit_ntp_init(&ad);
+
+	ktime_get_real_ts64(&ts);
+	add_device_randomness(&ts, sizeof(ts));
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	orig_tai = tai = tk->tai_offset;
+	ret = __do_adjtimex(txc, &ts, &tai, &ad);
+
+	if (tai != orig_tai) {
+		__timekeeping_set_tai_offset(tk, tai);
+		timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+		clock_set = true;
+	}
+	tk_update_leap_state(tk);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+	audit_ntp_log(&ad);
+
+	/* Update the multiplier immediately if frequency was set directly */
+	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
+		clock_set |= timekeeping_advance(TK_ADV_FREQ);
+
+	if (clock_set)
+		clock_was_set(CLOCK_REALTIME);
+
+	ntp_notify_cmos_timer();
+
+	return ret;
+}
+
+#ifdef CONFIG_NTP_PPS
+/**
+ * hardpps() - Accessor function to NTP __hardpps function
+ */
+void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	write_seqcount_begin(&tk_core.seq);
+
+	__hardpps(phase_ts, raw_ts);
+
+	write_seqcount_end(&tk_core.seq);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+}
+EXPORT_SYMBOL(hardpps);
+#endif /* CONFIG_NTP_PPS */
diff --git a/kernel/time/timekeeping.h b/kernel/time/timekeeping.h
new file mode 100644
index 0000000000..543beba096
--- /dev/null
+++ b/kernel/time/timekeeping.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KERNEL_TIME_TIMEKEEPING_H
+#define _KERNEL_TIME_TIMEKEEPING_H
+/*
+ * Internal interfaces for kernel/time/
+ */
+extern ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq,
+					    ktime_t *offs_real,
+					    ktime_t *offs_boot,
+					    ktime_t *offs_tai);
+
+extern int timekeeping_valid_for_hres(void);
+extern u64 timekeeping_max_deferment(void);
+extern void timekeeping_warp_clock(void);
+extern int timekeeping_suspend(void);
+extern void timekeeping_resume(void);
+#ifdef CONFIG_GENERIC_SCHED_CLOCK
+extern int sched_clock_suspend(void);
+extern void sched_clock_resume(void);
+#else
+static inline int sched_clock_suspend(void) { return 0; }
+static inline void sched_clock_resume(void) { }
+#endif
+
+extern void update_process_times(int user);
+extern void do_timer(unsigned long ticks);
+extern void update_wall_time(void);
+
+extern raw_spinlock_t jiffies_lock;
+extern seqcount_raw_spinlock_t jiffies_seq;
+
+#define CS_NAME_LEN	32
+
+#endif
diff --git a/kernel/time/timekeeping_debug.c b/kernel/time/timekeeping_debug.c
new file mode 100644
index 0000000000..b73e8850e5
--- /dev/null
+++ b/kernel/time/timekeeping_debug.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * debugfs file to track time spent in suspend
+ *
+ * Copyright (c) 2011, Google, Inc.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/seq_file.h>
+#include <linux/suspend.h>
+#include <linux/time.h>
+
+#include "timekeeping_internal.h"
+
+#define NUM_BINS 32
+
+static unsigned int sleep_time_bin[NUM_BINS] = {0};
+
+static int tk_debug_sleep_time_show(struct seq_file *s, void *data)
+{
+	unsigned int bin;
+	seq_puts(s, "      time (secs)        count\n");
+	seq_puts(s, "------------------------------\n");
+	for (bin = 0; bin < 32; bin++) {
+		if (sleep_time_bin[bin] == 0)
+			continue;
+		seq_printf(s, "%10u - %-10u %4u\n",
+			bin ? 1 << (bin - 1) : 0, 1 << bin,
+				sleep_time_bin[bin]);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(tk_debug_sleep_time);
+
+static int __init tk_debug_sleep_time_init(void)
+{
+	debugfs_create_file("sleep_time", 0444, NULL, NULL,
+			    &tk_debug_sleep_time_fops);
+	return 0;
+}
+late_initcall(tk_debug_sleep_time_init);
+
+void tk_debug_account_sleep_time(const struct timespec64 *t)
+{
+	/* Cap bin index so we don't overflow the array */
+	int bin = min(fls(t->tv_sec), NUM_BINS-1);
+
+	sleep_time_bin[bin]++;
+	pm_deferred_pr_dbg("Timekeeping suspended for %lld.%03lu seconds\n",
+			   (s64)t->tv_sec, t->tv_nsec / NSEC_PER_MSEC);
+}
+
diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h
new file mode 100644
index 0000000000..4ca2787d16
--- /dev/null
+++ b/kernel/time/timekeeping_internal.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TIMEKEEPING_INTERNAL_H
+#define _TIMEKEEPING_INTERNAL_H
+
+#include <linux/clocksource.h>
+#include <linux/spinlock.h>
+#include <linux/time.h>
+
+/*
+ * timekeeping debug functions
+ */
+#ifdef CONFIG_DEBUG_FS
+extern void tk_debug_account_sleep_time(const struct timespec64 *t);
+#else
+#define tk_debug_account_sleep_time(x)
+#endif
+
+#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE
+static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
+{
+	u64 ret = (now - last) & mask;
+
+	/*
+	 * Prevent time going backwards by checking the MSB of mask in
+	 * the result. If set, return 0.
+	 */
+	return ret & ~(mask >> 1) ? 0 : ret;
+}
+#else
+static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
+{
+	return (now - last) & mask;
+}
+#endif
+
+/* Semi public for serialization of non timekeeper VDSO updates. */
+extern raw_spinlock_t timekeeper_lock;
+
+#endif /* _TIMEKEEPING_INTERNAL_H */
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
new file mode 100644
index 0000000000..63a8ce7177
--- /dev/null
+++ b/kernel/time/timer.c
@@ -0,0 +1,2367 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Kernel internal timers
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
+ *
+ *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
+ *              "A Kernel Model for Precision Timekeeping" by Dave Mills
+ *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
+ *              serialize accesses to xtime/lost_ticks).
+ *                              Copyright (C) 1998  Andrea Arcangeli
+ *  1999-03-10  Improved NTP compatibility by Ulrich Windl
+ *  2002-05-31	Move sys_sysinfo here and make its locking sane, Robert Love
+ *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
+ *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
+ *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
+ */
+
+#include <linux/kernel_stat.h>
+#include <linux/export.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/pid_namespace.h>
+#include <linux/notifier.h>
+#include <linux/thread_info.h>
+#include <linux/time.h>
+#include <linux/jiffies.h>
+#include <linux/posix-timers.h>
+#include <linux/cpu.h>
+#include <linux/syscalls.h>
+#include <linux/delay.h>
+#include <linux/tick.h>
+#include <linux/kallsyms.h>
+#include <linux/irq_work.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/sysctl.h>
+#include <linux/sched/nohz.h>
+#include <linux/sched/debug.h>
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/random.h>
+#include <linux/sysctl.h>
+
+#include <linux/uaccess.h>
+#include <asm/unistd.h>
+#include <asm/div64.h>
+#include <asm/timex.h>
+#include <asm/io.h>
+
+#include "tick-internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/timer.h>
+
+__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
+
+EXPORT_SYMBOL(jiffies_64);
+
+/*
+ * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
+ * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
+ * level has a different granularity.
+ *
+ * The level granularity is:		LVL_CLK_DIV ^ lvl
+ * The level clock frequency is:	HZ / (LVL_CLK_DIV ^ level)
+ *
+ * The array level of a newly armed timer depends on the relative expiry
+ * time. The farther the expiry time is away the higher the array level and
+ * therefor the granularity becomes.
+ *
+ * Contrary to the original timer wheel implementation, which aims for 'exact'
+ * expiry of the timers, this implementation removes the need for recascading
+ * the timers into the lower array levels. The previous 'classic' timer wheel
+ * implementation of the kernel already violated the 'exact' expiry by adding
+ * slack to the expiry time to provide batched expiration. The granularity
+ * levels provide implicit batching.
+ *
+ * This is an optimization of the original timer wheel implementation for the
+ * majority of the timer wheel use cases: timeouts. The vast majority of
+ * timeout timers (networking, disk I/O ...) are canceled before expiry. If
+ * the timeout expires it indicates that normal operation is disturbed, so it
+ * does not matter much whether the timeout comes with a slight delay.
+ *
+ * The only exception to this are networking timers with a small expiry
+ * time. They rely on the granularity. Those fit into the first wheel level,
+ * which has HZ granularity.
+ *
+ * We don't have cascading anymore. timers with a expiry time above the
+ * capacity of the last wheel level are force expired at the maximum timeout
+ * value of the last wheel level. From data sampling we know that the maximum
+ * value observed is 5 days (network connection tracking), so this should not
+ * be an issue.
+ *
+ * The currently chosen array constants values are a good compromise between
+ * array size and granularity.
+ *
+ * This results in the following granularity and range levels:
+ *
+ * HZ 1000 steps
+ * Level Offset  Granularity            Range
+ *  0      0         1 ms                0 ms -         63 ms
+ *  1     64         8 ms               64 ms -        511 ms
+ *  2    128        64 ms              512 ms -       4095 ms (512ms - ~4s)
+ *  3    192       512 ms             4096 ms -      32767 ms (~4s - ~32s)
+ *  4    256      4096 ms (~4s)      32768 ms -     262143 ms (~32s - ~4m)
+ *  5    320     32768 ms (~32s)    262144 ms -    2097151 ms (~4m - ~34m)
+ *  6    384    262144 ms (~4m)    2097152 ms -   16777215 ms (~34m - ~4h)
+ *  7    448   2097152 ms (~34m)  16777216 ms -  134217727 ms (~4h - ~1d)
+ *  8    512  16777216 ms (~4h)  134217728 ms - 1073741822 ms (~1d - ~12d)
+ *
+ * HZ  300
+ * Level Offset  Granularity            Range
+ *  0	   0         3 ms                0 ms -        210 ms
+ *  1	  64        26 ms              213 ms -       1703 ms (213ms - ~1s)
+ *  2	 128       213 ms             1706 ms -      13650 ms (~1s - ~13s)
+ *  3	 192      1706 ms (~1s)      13653 ms -     109223 ms (~13s - ~1m)
+ *  4	 256     13653 ms (~13s)    109226 ms -     873810 ms (~1m - ~14m)
+ *  5	 320    109226 ms (~1m)     873813 ms -    6990503 ms (~14m - ~1h)
+ *  6	 384    873813 ms (~14m)   6990506 ms -   55924050 ms (~1h - ~15h)
+ *  7	 448   6990506 ms (~1h)   55924053 ms -  447392423 ms (~15h - ~5d)
+ *  8    512  55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
+ *
+ * HZ  250
+ * Level Offset  Granularity            Range
+ *  0	   0         4 ms                0 ms -        255 ms
+ *  1	  64        32 ms              256 ms -       2047 ms (256ms - ~2s)
+ *  2	 128       256 ms             2048 ms -      16383 ms (~2s - ~16s)
+ *  3	 192      2048 ms (~2s)      16384 ms -     131071 ms (~16s - ~2m)
+ *  4	 256     16384 ms (~16s)    131072 ms -    1048575 ms (~2m - ~17m)
+ *  5	 320    131072 ms (~2m)    1048576 ms -    8388607 ms (~17m - ~2h)
+ *  6	 384   1048576 ms (~17m)   8388608 ms -   67108863 ms (~2h - ~18h)
+ *  7	 448   8388608 ms (~2h)   67108864 ms -  536870911 ms (~18h - ~6d)
+ *  8    512  67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
+ *
+ * HZ  100
+ * Level Offset  Granularity            Range
+ *  0	   0         10 ms               0 ms -        630 ms
+ *  1	  64         80 ms             640 ms -       5110 ms (640ms - ~5s)
+ *  2	 128        640 ms            5120 ms -      40950 ms (~5s - ~40s)
+ *  3	 192       5120 ms (~5s)     40960 ms -     327670 ms (~40s - ~5m)
+ *  4	 256      40960 ms (~40s)   327680 ms -    2621430 ms (~5m - ~43m)
+ *  5	 320     327680 ms (~5m)   2621440 ms -   20971510 ms (~43m - ~5h)
+ *  6	 384    2621440 ms (~43m) 20971520 ms -  167772150 ms (~5h - ~1d)
+ *  7	 448   20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
+ */
+
+/* Clock divisor for the next level */
+#define LVL_CLK_SHIFT	3
+#define LVL_CLK_DIV	(1UL << LVL_CLK_SHIFT)
+#define LVL_CLK_MASK	(LVL_CLK_DIV - 1)
+#define LVL_SHIFT(n)	((n) * LVL_CLK_SHIFT)
+#define LVL_GRAN(n)	(1UL << LVL_SHIFT(n))
+
+/*
+ * The time start value for each level to select the bucket at enqueue
+ * time. We start from the last possible delta of the previous level
+ * so that we can later add an extra LVL_GRAN(n) to n (see calc_index()).
+ */
+#define LVL_START(n)	((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
+
+/* Size of each clock level */
+#define LVL_BITS	6
+#define LVL_SIZE	(1UL << LVL_BITS)
+#define LVL_MASK	(LVL_SIZE - 1)
+#define LVL_OFFS(n)	((n) * LVL_SIZE)
+
+/* Level depth */
+#if HZ > 100
+# define LVL_DEPTH	9
+# else
+# define LVL_DEPTH	8
+#endif
+
+/* The cutoff (max. capacity of the wheel) */
+#define WHEEL_TIMEOUT_CUTOFF	(LVL_START(LVL_DEPTH))
+#define WHEEL_TIMEOUT_MAX	(WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
+
+/*
+ * The resulting wheel size. If NOHZ is configured we allocate two
+ * wheels so we have a separate storage for the deferrable timers.
+ */
+#define WHEEL_SIZE	(LVL_SIZE * LVL_DEPTH)
+
+#ifdef CONFIG_NO_HZ_COMMON
+# define NR_BASES	2
+# define BASE_STD	0
+# define BASE_DEF	1
+#else
+# define NR_BASES	1
+# define BASE_STD	0
+# define BASE_DEF	0
+#endif
+
+struct timer_base {
+	raw_spinlock_t		lock;
+	struct timer_list	*running_timer;
+#ifdef CONFIG_PREEMPT_RT
+	spinlock_t		expiry_lock;
+	atomic_t		timer_waiters;
+#endif
+	unsigned long		clk;
+	unsigned long		next_expiry;
+	unsigned int		cpu;
+	bool			next_expiry_recalc;
+	bool			is_idle;
+	bool			timers_pending;
+	DECLARE_BITMAP(pending_map, WHEEL_SIZE);
+	struct hlist_head	vectors[WHEEL_SIZE];
+} ____cacheline_aligned;
+
+static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
+
+#ifdef CONFIG_NO_HZ_COMMON
+
+static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
+static DEFINE_MUTEX(timer_keys_mutex);
+
+static void timer_update_keys(struct work_struct *work);
+static DECLARE_WORK(timer_update_work, timer_update_keys);
+
+#ifdef CONFIG_SMP
+static unsigned int sysctl_timer_migration = 1;
+
+DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
+
+static void timers_update_migration(void)
+{
+	if (sysctl_timer_migration && tick_nohz_active)
+		static_branch_enable(&timers_migration_enabled);
+	else
+		static_branch_disable(&timers_migration_enabled);
+}
+
+#ifdef CONFIG_SYSCTL
+static int timer_migration_handler(struct ctl_table *table, int write,
+			    void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	mutex_lock(&timer_keys_mutex);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	if (!ret && write)
+		timers_update_migration();
+	mutex_unlock(&timer_keys_mutex);
+	return ret;
+}
+
+static struct ctl_table timer_sysctl[] = {
+	{
+		.procname	= "timer_migration",
+		.data		= &sysctl_timer_migration,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= timer_migration_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{}
+};
+
+static int __init timer_sysctl_init(void)
+{
+	register_sysctl("kernel", timer_sysctl);
+	return 0;
+}
+device_initcall(timer_sysctl_init);
+#endif /* CONFIG_SYSCTL */
+#else /* CONFIG_SMP */
+static inline void timers_update_migration(void) { }
+#endif /* !CONFIG_SMP */
+
+static void timer_update_keys(struct work_struct *work)
+{
+	mutex_lock(&timer_keys_mutex);
+	timers_update_migration();
+	static_branch_enable(&timers_nohz_active);
+	mutex_unlock(&timer_keys_mutex);
+}
+
+void timers_update_nohz(void)
+{
+	schedule_work(&timer_update_work);
+}
+
+static inline bool is_timers_nohz_active(void)
+{
+	return static_branch_unlikely(&timers_nohz_active);
+}
+#else
+static inline bool is_timers_nohz_active(void) { return false; }
+#endif /* NO_HZ_COMMON */
+
+static unsigned long round_jiffies_common(unsigned long j, int cpu,
+		bool force_up)
+{
+	int rem;
+	unsigned long original = j;
+
+	/*
+	 * We don't want all cpus firing their timers at once hitting the
+	 * same lock or cachelines, so we skew each extra cpu with an extra
+	 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
+	 * already did this.
+	 * The skew is done by adding 3*cpunr, then round, then subtract this
+	 * extra offset again.
+	 */
+	j += cpu * 3;
+
+	rem = j % HZ;
+
+	/*
+	 * If the target jiffie is just after a whole second (which can happen
+	 * due to delays of the timer irq, long irq off times etc etc) then
+	 * we should round down to the whole second, not up. Use 1/4th second
+	 * as cutoff for this rounding as an extreme upper bound for this.
+	 * But never round down if @force_up is set.
+	 */
+	if (rem < HZ/4 && !force_up) /* round down */
+		j = j - rem;
+	else /* round up */
+		j = j - rem + HZ;
+
+	/* now that we have rounded, subtract the extra skew again */
+	j -= cpu * 3;
+
+	/*
+	 * Make sure j is still in the future. Otherwise return the
+	 * unmodified value.
+	 */
+	return time_is_after_jiffies(j) ? j : original;
+}
+
+/**
+ * __round_jiffies - function to round jiffies to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ * @cpu: the processor number on which the timeout will happen
+ *
+ * __round_jiffies() rounds an absolute time in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The exact rounding is skewed for each processor to avoid all
+ * processors firing at the exact same time, which could lead
+ * to lock contention or spurious cache line bouncing.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+unsigned long __round_jiffies(unsigned long j, int cpu)
+{
+	return round_jiffies_common(j, cpu, false);
+}
+EXPORT_SYMBOL_GPL(__round_jiffies);
+
+/**
+ * __round_jiffies_relative - function to round jiffies to a full second
+ * @j: the time in (relative) jiffies that should be rounded
+ * @cpu: the processor number on which the timeout will happen
+ *
+ * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The exact rounding is skewed for each processor to avoid all
+ * processors firing at the exact same time, which could lead
+ * to lock contention or spurious cache line bouncing.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+unsigned long __round_jiffies_relative(unsigned long j, int cpu)
+{
+	unsigned long j0 = jiffies;
+
+	/* Use j0 because jiffies might change while we run */
+	return round_jiffies_common(j + j0, cpu, false) - j0;
+}
+EXPORT_SYMBOL_GPL(__round_jiffies_relative);
+
+/**
+ * round_jiffies - function to round jiffies to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ *
+ * round_jiffies() rounds an absolute time in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+unsigned long round_jiffies(unsigned long j)
+{
+	return round_jiffies_common(j, raw_smp_processor_id(), false);
+}
+EXPORT_SYMBOL_GPL(round_jiffies);
+
+/**
+ * round_jiffies_relative - function to round jiffies to a full second
+ * @j: the time in (relative) jiffies that should be rounded
+ *
+ * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
+ * up or down to (approximately) full seconds. This is useful for timers
+ * for which the exact time they fire does not matter too much, as long as
+ * they fire approximately every X seconds.
+ *
+ * By rounding these timers to whole seconds, all such timers will fire
+ * at the same time, rather than at various times spread out. The goal
+ * of this is to have the CPU wake up less, which saves power.
+ *
+ * The return value is the rounded version of the @j parameter.
+ */
+unsigned long round_jiffies_relative(unsigned long j)
+{
+	return __round_jiffies_relative(j, raw_smp_processor_id());
+}
+EXPORT_SYMBOL_GPL(round_jiffies_relative);
+
+/**
+ * __round_jiffies_up - function to round jiffies up to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ * @cpu: the processor number on which the timeout will happen
+ *
+ * This is the same as __round_jiffies() except that it will never
+ * round down.  This is useful for timeouts for which the exact time
+ * of firing does not matter too much, as long as they don't fire too
+ * early.
+ */
+unsigned long __round_jiffies_up(unsigned long j, int cpu)
+{
+	return round_jiffies_common(j, cpu, true);
+}
+EXPORT_SYMBOL_GPL(__round_jiffies_up);
+
+/**
+ * __round_jiffies_up_relative - function to round jiffies up to a full second
+ * @j: the time in (relative) jiffies that should be rounded
+ * @cpu: the processor number on which the timeout will happen
+ *
+ * This is the same as __round_jiffies_relative() except that it will never
+ * round down.  This is useful for timeouts for which the exact time
+ * of firing does not matter too much, as long as they don't fire too
+ * early.
+ */
+unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
+{
+	unsigned long j0 = jiffies;
+
+	/* Use j0 because jiffies might change while we run */
+	return round_jiffies_common(j + j0, cpu, true) - j0;
+}
+EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
+
+/**
+ * round_jiffies_up - function to round jiffies up to a full second
+ * @j: the time in (absolute) jiffies that should be rounded
+ *
+ * This is the same as round_jiffies() except that it will never
+ * round down.  This is useful for timeouts for which the exact time
+ * of firing does not matter too much, as long as they don't fire too
+ * early.
+ */
+unsigned long round_jiffies_up(unsigned long j)
+{
+	return round_jiffies_common(j, raw_smp_processor_id(), true);
+}
+EXPORT_SYMBOL_GPL(round_jiffies_up);
+
+/**
+ * round_jiffies_up_relative - function to round jiffies up to a full second
+ * @j: the time in (relative) jiffies that should be rounded
+ *
+ * This is the same as round_jiffies_relative() except that it will never
+ * round down.  This is useful for timeouts for which the exact time
+ * of firing does not matter too much, as long as they don't fire too
+ * early.
+ */
+unsigned long round_jiffies_up_relative(unsigned long j)
+{
+	return __round_jiffies_up_relative(j, raw_smp_processor_id());
+}
+EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
+
+
+static inline unsigned int timer_get_idx(struct timer_list *timer)
+{
+	return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
+}
+
+static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
+{
+	timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
+			idx << TIMER_ARRAYSHIFT;
+}
+
+/*
+ * Helper function to calculate the array index for a given expiry
+ * time.
+ */
+static inline unsigned calc_index(unsigned long expires, unsigned lvl,
+				  unsigned long *bucket_expiry)
+{
+
+	/*
+	 * The timer wheel has to guarantee that a timer does not fire
+	 * early. Early expiry can happen due to:
+	 * - Timer is armed at the edge of a tick
+	 * - Truncation of the expiry time in the outer wheel levels
+	 *
+	 * Round up with level granularity to prevent this.
+	 */
+	expires = (expires >> LVL_SHIFT(lvl)) + 1;
+	*bucket_expiry = expires << LVL_SHIFT(lvl);
+	return LVL_OFFS(lvl) + (expires & LVL_MASK);
+}
+
+static int calc_wheel_index(unsigned long expires, unsigned long clk,
+			    unsigned long *bucket_expiry)
+{
+	unsigned long delta = expires - clk;
+	unsigned int idx;
+
+	if (delta < LVL_START(1)) {
+		idx = calc_index(expires, 0, bucket_expiry);
+	} else if (delta < LVL_START(2)) {
+		idx = calc_index(expires, 1, bucket_expiry);
+	} else if (delta < LVL_START(3)) {
+		idx = calc_index(expires, 2, bucket_expiry);
+	} else if (delta < LVL_START(4)) {
+		idx = calc_index(expires, 3, bucket_expiry);
+	} else if (delta < LVL_START(5)) {
+		idx = calc_index(expires, 4, bucket_expiry);
+	} else if (delta < LVL_START(6)) {
+		idx = calc_index(expires, 5, bucket_expiry);
+	} else if (delta < LVL_START(7)) {
+		idx = calc_index(expires, 6, bucket_expiry);
+	} else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
+		idx = calc_index(expires, 7, bucket_expiry);
+	} else if ((long) delta < 0) {
+		idx = clk & LVL_MASK;
+		*bucket_expiry = clk;
+	} else {
+		/*
+		 * Force expire obscene large timeouts to expire at the
+		 * capacity limit of the wheel.
+		 */
+		if (delta >= WHEEL_TIMEOUT_CUTOFF)
+			expires = clk + WHEEL_TIMEOUT_MAX;
+
+		idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
+	}
+	return idx;
+}
+
+static void
+trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
+{
+	if (!is_timers_nohz_active())
+		return;
+
+	/*
+	 * TODO: This wants some optimizing similar to the code below, but we
+	 * will do that when we switch from push to pull for deferrable timers.
+	 */
+	if (timer->flags & TIMER_DEFERRABLE) {
+		if (tick_nohz_full_cpu(base->cpu))
+			wake_up_nohz_cpu(base->cpu);
+		return;
+	}
+
+	/*
+	 * We might have to IPI the remote CPU if the base is idle and the
+	 * timer is not deferrable. If the other CPU is on the way to idle
+	 * then it can't set base->is_idle as we hold the base lock:
+	 */
+	if (base->is_idle)
+		wake_up_nohz_cpu(base->cpu);
+}
+
+/*
+ * Enqueue the timer into the hash bucket, mark it pending in
+ * the bitmap, store the index in the timer flags then wake up
+ * the target CPU if needed.
+ */
+static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
+			  unsigned int idx, unsigned long bucket_expiry)
+{
+
+	hlist_add_head(&timer->entry, base->vectors + idx);
+	__set_bit(idx, base->pending_map);
+	timer_set_idx(timer, idx);
+
+	trace_timer_start(timer, timer->expires, timer->flags);
+
+	/*
+	 * Check whether this is the new first expiring timer. The
+	 * effective expiry time of the timer is required here
+	 * (bucket_expiry) instead of timer->expires.
+	 */
+	if (time_before(bucket_expiry, base->next_expiry)) {
+		/*
+		 * Set the next expiry time and kick the CPU so it
+		 * can reevaluate the wheel:
+		 */
+		base->next_expiry = bucket_expiry;
+		base->timers_pending = true;
+		base->next_expiry_recalc = false;
+		trigger_dyntick_cpu(base, timer);
+	}
+}
+
+static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
+{
+	unsigned long bucket_expiry;
+	unsigned int idx;
+
+	idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry);
+	enqueue_timer(base, timer, idx, bucket_expiry);
+}
+
+#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
+
+static const struct debug_obj_descr timer_debug_descr;
+
+struct timer_hint {
+	void	(*function)(struct timer_list *t);
+	long	offset;
+};
+
+#define TIMER_HINT(fn, container, timr, hintfn)			\
+	{							\
+		.function = fn,					\
+		.offset	  = offsetof(container, hintfn) -	\
+			    offsetof(container, timr)		\
+	}
+
+static const struct timer_hint timer_hints[] = {
+	TIMER_HINT(delayed_work_timer_fn,
+		   struct delayed_work, timer, work.func),
+	TIMER_HINT(kthread_delayed_work_timer_fn,
+		   struct kthread_delayed_work, timer, work.func),
+};
+
+static void *timer_debug_hint(void *addr)
+{
+	struct timer_list *timer = addr;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(timer_hints); i++) {
+		if (timer_hints[i].function == timer->function) {
+			void (**fn)(void) = addr + timer_hints[i].offset;
+
+			return *fn;
+		}
+	}
+
+	return timer->function;
+}
+
+static bool timer_is_static_object(void *addr)
+{
+	struct timer_list *timer = addr;
+
+	return (timer->entry.pprev == NULL &&
+		timer->entry.next == TIMER_ENTRY_STATIC);
+}
+
+/*
+ * fixup_init is called when:
+ * - an active object is initialized
+ */
+static bool timer_fixup_init(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		del_timer_sync(timer);
+		debug_object_init(timer, &timer_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/* Stub timer callback for improperly used timers. */
+static void stub_timer(struct timer_list *unused)
+{
+	WARN_ON(1);
+}
+
+/*
+ * fixup_activate is called when:
+ * - an active object is activated
+ * - an unknown non-static object is activated
+ */
+static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_NOTAVAILABLE:
+		timer_setup(timer, stub_timer, 0);
+		return true;
+
+	case ODEBUG_STATE_ACTIVE:
+		WARN_ON(1);
+		fallthrough;
+	default:
+		return false;
+	}
+}
+
+/*
+ * fixup_free is called when:
+ * - an active object is freed
+ */
+static bool timer_fixup_free(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		del_timer_sync(timer);
+		debug_object_free(timer, &timer_debug_descr);
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * fixup_assert_init is called when:
+ * - an untracked/uninit-ed object is found
+ */
+static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_NOTAVAILABLE:
+		timer_setup(timer, stub_timer, 0);
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct debug_obj_descr timer_debug_descr = {
+	.name			= "timer_list",
+	.debug_hint		= timer_debug_hint,
+	.is_static_object	= timer_is_static_object,
+	.fixup_init		= timer_fixup_init,
+	.fixup_activate		= timer_fixup_activate,
+	.fixup_free		= timer_fixup_free,
+	.fixup_assert_init	= timer_fixup_assert_init,
+};
+
+static inline void debug_timer_init(struct timer_list *timer)
+{
+	debug_object_init(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_activate(struct timer_list *timer)
+{
+	debug_object_activate(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_deactivate(struct timer_list *timer)
+{
+	debug_object_deactivate(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_assert_init(struct timer_list *timer)
+{
+	debug_object_assert_init(timer, &timer_debug_descr);
+}
+
+static void do_init_timer(struct timer_list *timer,
+			  void (*func)(struct timer_list *),
+			  unsigned int flags,
+			  const char *name, struct lock_class_key *key);
+
+void init_timer_on_stack_key(struct timer_list *timer,
+			     void (*func)(struct timer_list *),
+			     unsigned int flags,
+			     const char *name, struct lock_class_key *key)
+{
+	debug_object_init_on_stack(timer, &timer_debug_descr);
+	do_init_timer(timer, func, flags, name, key);
+}
+EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
+
+void destroy_timer_on_stack(struct timer_list *timer)
+{
+	debug_object_free(timer, &timer_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
+
+#else
+static inline void debug_timer_init(struct timer_list *timer) { }
+static inline void debug_timer_activate(struct timer_list *timer) { }
+static inline void debug_timer_deactivate(struct timer_list *timer) { }
+static inline void debug_timer_assert_init(struct timer_list *timer) { }
+#endif
+
+static inline void debug_init(struct timer_list *timer)
+{
+	debug_timer_init(timer);
+	trace_timer_init(timer);
+}
+
+static inline void debug_deactivate(struct timer_list *timer)
+{
+	debug_timer_deactivate(timer);
+	trace_timer_cancel(timer);
+}
+
+static inline void debug_assert_init(struct timer_list *timer)
+{
+	debug_timer_assert_init(timer);
+}
+
+static void do_init_timer(struct timer_list *timer,
+			  void (*func)(struct timer_list *),
+			  unsigned int flags,
+			  const char *name, struct lock_class_key *key)
+{
+	timer->entry.pprev = NULL;
+	timer->function = func;
+	if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
+		flags &= TIMER_INIT_FLAGS;
+	timer->flags = flags | raw_smp_processor_id();
+	lockdep_init_map(&timer->lockdep_map, name, key, 0);
+}
+
+/**
+ * init_timer_key - initialize a timer
+ * @timer: the timer to be initialized
+ * @func: timer callback function
+ * @flags: timer flags
+ * @name: name of the timer
+ * @key: lockdep class key of the fake lock used for tracking timer
+ *       sync lock dependencies
+ *
+ * init_timer_key() must be done to a timer prior calling *any* of the
+ * other timer functions.
+ */
+void init_timer_key(struct timer_list *timer,
+		    void (*func)(struct timer_list *), unsigned int flags,
+		    const char *name, struct lock_class_key *key)
+{
+	debug_init(timer);
+	do_init_timer(timer, func, flags, name, key);
+}
+EXPORT_SYMBOL(init_timer_key);
+
+static inline void detach_timer(struct timer_list *timer, bool clear_pending)
+{
+	struct hlist_node *entry = &timer->entry;
+
+	debug_deactivate(timer);
+
+	__hlist_del(entry);
+	if (clear_pending)
+		entry->pprev = NULL;
+	entry->next = LIST_POISON2;
+}
+
+static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
+			     bool clear_pending)
+{
+	unsigned idx = timer_get_idx(timer);
+
+	if (!timer_pending(timer))
+		return 0;
+
+	if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
+		__clear_bit(idx, base->pending_map);
+		base->next_expiry_recalc = true;
+	}
+
+	detach_timer(timer, clear_pending);
+	return 1;
+}
+
+static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
+{
+	struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
+
+	/*
+	 * If the timer is deferrable and NO_HZ_COMMON is set then we need
+	 * to use the deferrable base.
+	 */
+	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
+		base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
+	return base;
+}
+
+static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
+	/*
+	 * If the timer is deferrable and NO_HZ_COMMON is set then we need
+	 * to use the deferrable base.
+	 */
+	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
+		base = this_cpu_ptr(&timer_bases[BASE_DEF]);
+	return base;
+}
+
+static inline struct timer_base *get_timer_base(u32 tflags)
+{
+	return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
+}
+
+static inline struct timer_base *
+get_target_base(struct timer_base *base, unsigned tflags)
+{
+#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
+	if (static_branch_likely(&timers_migration_enabled) &&
+	    !(tflags & TIMER_PINNED))
+		return get_timer_cpu_base(tflags, get_nohz_timer_target());
+#endif
+	return get_timer_this_cpu_base(tflags);
+}
+
+static inline void forward_timer_base(struct timer_base *base)
+{
+	unsigned long jnow = READ_ONCE(jiffies);
+
+	/*
+	 * No need to forward if we are close enough below jiffies.
+	 * Also while executing timers, base->clk is 1 offset ahead
+	 * of jiffies to avoid endless requeuing to current jiffies.
+	 */
+	if ((long)(jnow - base->clk) < 1)
+		return;
+
+	/*
+	 * If the next expiry value is > jiffies, then we fast forward to
+	 * jiffies otherwise we forward to the next expiry value.
+	 */
+	if (time_after(base->next_expiry, jnow)) {
+		base->clk = jnow;
+	} else {
+		if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
+			return;
+		base->clk = base->next_expiry;
+	}
+}
+
+
+/*
+ * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
+ * that all timers which are tied to this base are locked, and the base itself
+ * is locked too.
+ *
+ * So __run_timers/migrate_timers can safely modify all timers which could
+ * be found in the base->vectors array.
+ *
+ * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
+ * to wait until the migration is done.
+ */
+static struct timer_base *lock_timer_base(struct timer_list *timer,
+					  unsigned long *flags)
+	__acquires(timer->base->lock)
+{
+	for (;;) {
+		struct timer_base *base;
+		u32 tf;
+
+		/*
+		 * We need to use READ_ONCE() here, otherwise the compiler
+		 * might re-read @tf between the check for TIMER_MIGRATING
+		 * and spin_lock().
+		 */
+		tf = READ_ONCE(timer->flags);
+
+		if (!(tf & TIMER_MIGRATING)) {
+			base = get_timer_base(tf);
+			raw_spin_lock_irqsave(&base->lock, *flags);
+			if (timer->flags == tf)
+				return base;
+			raw_spin_unlock_irqrestore(&base->lock, *flags);
+		}
+		cpu_relax();
+	}
+}
+
+#define MOD_TIMER_PENDING_ONLY		0x01
+#define MOD_TIMER_REDUCE		0x02
+#define MOD_TIMER_NOTPENDING		0x04
+
+static inline int
+__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
+{
+	unsigned long clk = 0, flags, bucket_expiry;
+	struct timer_base *base, *new_base;
+	unsigned int idx = UINT_MAX;
+	int ret = 0;
+
+	debug_assert_init(timer);
+
+	/*
+	 * This is a common optimization triggered by the networking code - if
+	 * the timer is re-modified to have the same timeout or ends up in the
+	 * same array bucket then just return:
+	 */
+	if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
+		/*
+		 * The downside of this optimization is that it can result in
+		 * larger granularity than you would get from adding a new
+		 * timer with this expiry.
+		 */
+		long diff = timer->expires - expires;
+
+		if (!diff)
+			return 1;
+		if (options & MOD_TIMER_REDUCE && diff <= 0)
+			return 1;
+
+		/*
+		 * We lock timer base and calculate the bucket index right
+		 * here. If the timer ends up in the same bucket, then we
+		 * just update the expiry time and avoid the whole
+		 * dequeue/enqueue dance.
+		 */
+		base = lock_timer_base(timer, &flags);
+		/*
+		 * Has @timer been shutdown? This needs to be evaluated
+		 * while holding base lock to prevent a race against the
+		 * shutdown code.
+		 */
+		if (!timer->function)
+			goto out_unlock;
+
+		forward_timer_base(base);
+
+		if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
+		    time_before_eq(timer->expires, expires)) {
+			ret = 1;
+			goto out_unlock;
+		}
+
+		clk = base->clk;
+		idx = calc_wheel_index(expires, clk, &bucket_expiry);
+
+		/*
+		 * Retrieve and compare the array index of the pending
+		 * timer. If it matches set the expiry to the new value so a
+		 * subsequent call will exit in the expires check above.
+		 */
+		if (idx == timer_get_idx(timer)) {
+			if (!(options & MOD_TIMER_REDUCE))
+				timer->expires = expires;
+			else if (time_after(timer->expires, expires))
+				timer->expires = expires;
+			ret = 1;
+			goto out_unlock;
+		}
+	} else {
+		base = lock_timer_base(timer, &flags);
+		/*
+		 * Has @timer been shutdown? This needs to be evaluated
+		 * while holding base lock to prevent a race against the
+		 * shutdown code.
+		 */
+		if (!timer->function)
+			goto out_unlock;
+
+		forward_timer_base(base);
+	}
+
+	ret = detach_if_pending(timer, base, false);
+	if (!ret && (options & MOD_TIMER_PENDING_ONLY))
+		goto out_unlock;
+
+	new_base = get_target_base(base, timer->flags);
+
+	if (base != new_base) {
+		/*
+		 * We are trying to schedule the timer on the new base.
+		 * However we can't change timer's base while it is running,
+		 * otherwise timer_delete_sync() can't detect that the timer's
+		 * handler yet has not finished. This also guarantees that the
+		 * timer is serialized wrt itself.
+		 */
+		if (likely(base->running_timer != timer)) {
+			/* See the comment in lock_timer_base() */
+			timer->flags |= TIMER_MIGRATING;
+
+			raw_spin_unlock(&base->lock);
+			base = new_base;
+			raw_spin_lock(&base->lock);
+			WRITE_ONCE(timer->flags,
+				   (timer->flags & ~TIMER_BASEMASK) | base->cpu);
+			forward_timer_base(base);
+		}
+	}
+
+	debug_timer_activate(timer);
+
+	timer->expires = expires;
+	/*
+	 * If 'idx' was calculated above and the base time did not advance
+	 * between calculating 'idx' and possibly switching the base, only
+	 * enqueue_timer() is required. Otherwise we need to (re)calculate
+	 * the wheel index via internal_add_timer().
+	 */
+	if (idx != UINT_MAX && clk == base->clk)
+		enqueue_timer(base, timer, idx, bucket_expiry);
+	else
+		internal_add_timer(base, timer);
+
+out_unlock:
+	raw_spin_unlock_irqrestore(&base->lock, flags);
+
+	return ret;
+}
+
+/**
+ * mod_timer_pending - Modify a pending timer's timeout
+ * @timer:	The pending timer to be modified
+ * @expires:	New absolute timeout in jiffies
+ *
+ * mod_timer_pending() is the same for pending timers as mod_timer(), but
+ * will not activate inactive timers.
+ *
+ * If @timer->function == NULL then the start operation is silently
+ * discarded.
+ *
+ * Return:
+ * * %0 - The timer was inactive and not modified or was in
+ *	  shutdown state and the operation was discarded
+ * * %1 - The timer was active and requeued to expire at @expires
+ */
+int mod_timer_pending(struct timer_list *timer, unsigned long expires)
+{
+	return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
+}
+EXPORT_SYMBOL(mod_timer_pending);
+
+/**
+ * mod_timer - Modify a timer's timeout
+ * @timer:	The timer to be modified
+ * @expires:	New absolute timeout in jiffies
+ *
+ * mod_timer(timer, expires) is equivalent to:
+ *
+ *     del_timer(timer); timer->expires = expires; add_timer(timer);
+ *
+ * mod_timer() is more efficient than the above open coded sequence. In
+ * case that the timer is inactive, the del_timer() part is a NOP. The
+ * timer is in any case activated with the new expiry time @expires.
+ *
+ * Note that if there are multiple unserialized concurrent users of the
+ * same timer, then mod_timer() is the only safe way to modify the timeout,
+ * since add_timer() cannot modify an already running timer.
+ *
+ * If @timer->function == NULL then the start operation is silently
+ * discarded. In this case the return value is 0 and meaningless.
+ *
+ * Return:
+ * * %0 - The timer was inactive and started or was in shutdown
+ *	  state and the operation was discarded
+ * * %1 - The timer was active and requeued to expire at @expires or
+ *	  the timer was active and not modified because @expires did
+ *	  not change the effective expiry time
+ */
+int mod_timer(struct timer_list *timer, unsigned long expires)
+{
+	return __mod_timer(timer, expires, 0);
+}
+EXPORT_SYMBOL(mod_timer);
+
+/**
+ * timer_reduce - Modify a timer's timeout if it would reduce the timeout
+ * @timer:	The timer to be modified
+ * @expires:	New absolute timeout in jiffies
+ *
+ * timer_reduce() is very similar to mod_timer(), except that it will only
+ * modify an enqueued timer if that would reduce the expiration time. If
+ * @timer is not enqueued it starts the timer.
+ *
+ * If @timer->function == NULL then the start operation is silently
+ * discarded.
+ *
+ * Return:
+ * * %0 - The timer was inactive and started or was in shutdown
+ *	  state and the operation was discarded
+ * * %1 - The timer was active and requeued to expire at @expires or
+ *	  the timer was active and not modified because @expires
+ *	  did not change the effective expiry time such that the
+ *	  timer would expire earlier than already scheduled
+ */
+int timer_reduce(struct timer_list *timer, unsigned long expires)
+{
+	return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
+}
+EXPORT_SYMBOL(timer_reduce);
+
+/**
+ * add_timer - Start a timer
+ * @timer:	The timer to be started
+ *
+ * Start @timer to expire at @timer->expires in the future. @timer->expires
+ * is the absolute expiry time measured in 'jiffies'. When the timer expires
+ * timer->function(timer) will be invoked from soft interrupt context.
+ *
+ * The @timer->expires and @timer->function fields must be set prior
+ * to calling this function.
+ *
+ * If @timer->function == NULL then the start operation is silently
+ * discarded.
+ *
+ * If @timer->expires is already in the past @timer will be queued to
+ * expire at the next timer tick.
+ *
+ * This can only operate on an inactive timer. Attempts to invoke this on
+ * an active timer are rejected with a warning.
+ */
+void add_timer(struct timer_list *timer)
+{
+	if (WARN_ON_ONCE(timer_pending(timer)))
+		return;
+	__mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
+}
+EXPORT_SYMBOL(add_timer);
+
+/**
+ * add_timer_on - Start a timer on a particular CPU
+ * @timer:	The timer to be started
+ * @cpu:	The CPU to start it on
+ *
+ * Same as add_timer() except that it starts the timer on the given CPU.
+ *
+ * See add_timer() for further details.
+ */
+void add_timer_on(struct timer_list *timer, int cpu)
+{
+	struct timer_base *new_base, *base;
+	unsigned long flags;
+
+	debug_assert_init(timer);
+
+	if (WARN_ON_ONCE(timer_pending(timer)))
+		return;
+
+	new_base = get_timer_cpu_base(timer->flags, cpu);
+
+	/*
+	 * If @timer was on a different CPU, it should be migrated with the
+	 * old base locked to prevent other operations proceeding with the
+	 * wrong base locked.  See lock_timer_base().
+	 */
+	base = lock_timer_base(timer, &flags);
+	/*
+	 * Has @timer been shutdown? This needs to be evaluated while
+	 * holding base lock to prevent a race against the shutdown code.
+	 */
+	if (!timer->function)
+		goto out_unlock;
+
+	if (base != new_base) {
+		timer->flags |= TIMER_MIGRATING;
+
+		raw_spin_unlock(&base->lock);
+		base = new_base;
+		raw_spin_lock(&base->lock);
+		WRITE_ONCE(timer->flags,
+			   (timer->flags & ~TIMER_BASEMASK) | cpu);
+	}
+	forward_timer_base(base);
+
+	debug_timer_activate(timer);
+	internal_add_timer(base, timer);
+out_unlock:
+	raw_spin_unlock_irqrestore(&base->lock, flags);
+}
+EXPORT_SYMBOL_GPL(add_timer_on);
+
+/**
+ * __timer_delete - Internal function: Deactivate a timer
+ * @timer:	The timer to be deactivated
+ * @shutdown:	If true, this indicates that the timer is about to be
+ *		shutdown permanently.
+ *
+ * If @shutdown is true then @timer->function is set to NULL under the
+ * timer base lock which prevents further rearming of the time. In that
+ * case any attempt to rearm @timer after this function returns will be
+ * silently ignored.
+ *
+ * Return:
+ * * %0 - The timer was not pending
+ * * %1 - The timer was pending and deactivated
+ */
+static int __timer_delete(struct timer_list *timer, bool shutdown)
+{
+	struct timer_base *base;
+	unsigned long flags;
+	int ret = 0;
+
+	debug_assert_init(timer);
+
+	/*
+	 * If @shutdown is set then the lock has to be taken whether the
+	 * timer is pending or not to protect against a concurrent rearm
+	 * which might hit between the lockless pending check and the lock
+	 * aquisition. By taking the lock it is ensured that such a newly
+	 * enqueued timer is dequeued and cannot end up with
+	 * timer->function == NULL in the expiry code.
+	 *
+	 * If timer->function is currently executed, then this makes sure
+	 * that the callback cannot requeue the timer.
+	 */
+	if (timer_pending(timer) || shutdown) {
+		base = lock_timer_base(timer, &flags);
+		ret = detach_if_pending(timer, base, true);
+		if (shutdown)
+			timer->function = NULL;
+		raw_spin_unlock_irqrestore(&base->lock, flags);
+	}
+
+	return ret;
+}
+
+/**
+ * timer_delete - Deactivate a timer
+ * @timer:	The timer to be deactivated
+ *
+ * The function only deactivates a pending timer, but contrary to
+ * timer_delete_sync() it does not take into account whether the timer's
+ * callback function is concurrently executed on a different CPU or not.
+ * It neither prevents rearming of the timer.  If @timer can be rearmed
+ * concurrently then the return value of this function is meaningless.
+ *
+ * Return:
+ * * %0 - The timer was not pending
+ * * %1 - The timer was pending and deactivated
+ */
+int timer_delete(struct timer_list *timer)
+{
+	return __timer_delete(timer, false);
+}
+EXPORT_SYMBOL(timer_delete);
+
+/**
+ * timer_shutdown - Deactivate a timer and prevent rearming
+ * @timer:	The timer to be deactivated
+ *
+ * The function does not wait for an eventually running timer callback on a
+ * different CPU but it prevents rearming of the timer. Any attempt to arm
+ * @timer after this function returns will be silently ignored.
+ *
+ * This function is useful for teardown code and should only be used when
+ * timer_shutdown_sync() cannot be invoked due to locking or context constraints.
+ *
+ * Return:
+ * * %0 - The timer was not pending
+ * * %1 - The timer was pending
+ */
+int timer_shutdown(struct timer_list *timer)
+{
+	return __timer_delete(timer, true);
+}
+EXPORT_SYMBOL_GPL(timer_shutdown);
+
+/**
+ * __try_to_del_timer_sync - Internal function: Try to deactivate a timer
+ * @timer:	Timer to deactivate
+ * @shutdown:	If true, this indicates that the timer is about to be
+ *		shutdown permanently.
+ *
+ * If @shutdown is true then @timer->function is set to NULL under the
+ * timer base lock which prevents further rearming of the timer. Any
+ * attempt to rearm @timer after this function returns will be silently
+ * ignored.
+ *
+ * This function cannot guarantee that the timer cannot be rearmed
+ * right after dropping the base lock if @shutdown is false. That
+ * needs to be prevented by the calling code if necessary.
+ *
+ * Return:
+ * * %0  - The timer was not pending
+ * * %1  - The timer was pending and deactivated
+ * * %-1 - The timer callback function is running on a different CPU
+ */
+static int __try_to_del_timer_sync(struct timer_list *timer, bool shutdown)
+{
+	struct timer_base *base;
+	unsigned long flags;
+	int ret = -1;
+
+	debug_assert_init(timer);
+
+	base = lock_timer_base(timer, &flags);
+
+	if (base->running_timer != timer)
+		ret = detach_if_pending(timer, base, true);
+	if (shutdown)
+		timer->function = NULL;
+
+	raw_spin_unlock_irqrestore(&base->lock, flags);
+
+	return ret;
+}
+
+/**
+ * try_to_del_timer_sync - Try to deactivate a timer
+ * @timer:	Timer to deactivate
+ *
+ * This function tries to deactivate a timer. On success the timer is not
+ * queued and the timer callback function is not running on any CPU.
+ *
+ * This function does not guarantee that the timer cannot be rearmed right
+ * after dropping the base lock. That needs to be prevented by the calling
+ * code if necessary.
+ *
+ * Return:
+ * * %0  - The timer was not pending
+ * * %1  - The timer was pending and deactivated
+ * * %-1 - The timer callback function is running on a different CPU
+ */
+int try_to_del_timer_sync(struct timer_list *timer)
+{
+	return __try_to_del_timer_sync(timer, false);
+}
+EXPORT_SYMBOL(try_to_del_timer_sync);
+
+#ifdef CONFIG_PREEMPT_RT
+static __init void timer_base_init_expiry_lock(struct timer_base *base)
+{
+	spin_lock_init(&base->expiry_lock);
+}
+
+static inline void timer_base_lock_expiry(struct timer_base *base)
+{
+	spin_lock(&base->expiry_lock);
+}
+
+static inline void timer_base_unlock_expiry(struct timer_base *base)
+{
+	spin_unlock(&base->expiry_lock);
+}
+
+/*
+ * The counterpart to del_timer_wait_running().
+ *
+ * If there is a waiter for base->expiry_lock, then it was waiting for the
+ * timer callback to finish. Drop expiry_lock and reacquire it. That allows
+ * the waiter to acquire the lock and make progress.
+ */
+static void timer_sync_wait_running(struct timer_base *base)
+{
+	if (atomic_read(&base->timer_waiters)) {
+		raw_spin_unlock_irq(&base->lock);
+		spin_unlock(&base->expiry_lock);
+		spin_lock(&base->expiry_lock);
+		raw_spin_lock_irq(&base->lock);
+	}
+}
+
+/*
+ * This function is called on PREEMPT_RT kernels when the fast path
+ * deletion of a timer failed because the timer callback function was
+ * running.
+ *
+ * This prevents priority inversion, if the softirq thread on a remote CPU
+ * got preempted, and it prevents a life lock when the task which tries to
+ * delete a timer preempted the softirq thread running the timer callback
+ * function.
+ */
+static void del_timer_wait_running(struct timer_list *timer)
+{
+	u32 tf;
+
+	tf = READ_ONCE(timer->flags);
+	if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) {
+		struct timer_base *base = get_timer_base(tf);
+
+		/*
+		 * Mark the base as contended and grab the expiry lock,
+		 * which is held by the softirq across the timer
+		 * callback. Drop the lock immediately so the softirq can
+		 * expire the next timer. In theory the timer could already
+		 * be running again, but that's more than unlikely and just
+		 * causes another wait loop.
+		 */
+		atomic_inc(&base->timer_waiters);
+		spin_lock_bh(&base->expiry_lock);
+		atomic_dec(&base->timer_waiters);
+		spin_unlock_bh(&base->expiry_lock);
+	}
+}
+#else
+static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
+static inline void timer_base_lock_expiry(struct timer_base *base) { }
+static inline void timer_base_unlock_expiry(struct timer_base *base) { }
+static inline void timer_sync_wait_running(struct timer_base *base) { }
+static inline void del_timer_wait_running(struct timer_list *timer) { }
+#endif
+
+/**
+ * __timer_delete_sync - Internal function: Deactivate a timer and wait
+ *			 for the handler to finish.
+ * @timer:	The timer to be deactivated
+ * @shutdown:	If true, @timer->function will be set to NULL under the
+ *		timer base lock which prevents rearming of @timer
+ *
+ * If @shutdown is not set the timer can be rearmed later. If the timer can
+ * be rearmed concurrently, i.e. after dropping the base lock then the
+ * return value is meaningless.
+ *
+ * If @shutdown is set then @timer->function is set to NULL under timer
+ * base lock which prevents rearming of the timer. Any attempt to rearm
+ * a shutdown timer is silently ignored.
+ *
+ * If the timer should be reused after shutdown it has to be initialized
+ * again.
+ *
+ * Return:
+ * * %0	- The timer was not pending
+ * * %1	- The timer was pending and deactivated
+ */
+static int __timer_delete_sync(struct timer_list *timer, bool shutdown)
+{
+	int ret;
+
+#ifdef CONFIG_LOCKDEP
+	unsigned long flags;
+
+	/*
+	 * If lockdep gives a backtrace here, please reference
+	 * the synchronization rules above.
+	 */
+	local_irq_save(flags);
+	lock_map_acquire(&timer->lockdep_map);
+	lock_map_release(&timer->lockdep_map);
+	local_irq_restore(flags);
+#endif
+	/*
+	 * don't use it in hardirq context, because it
+	 * could lead to deadlock.
+	 */
+	WARN_ON(in_hardirq() && !(timer->flags & TIMER_IRQSAFE));
+
+	/*
+	 * Must be able to sleep on PREEMPT_RT because of the slowpath in
+	 * del_timer_wait_running().
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
+		lockdep_assert_preemption_enabled();
+
+	do {
+		ret = __try_to_del_timer_sync(timer, shutdown);
+
+		if (unlikely(ret < 0)) {
+			del_timer_wait_running(timer);
+			cpu_relax();
+		}
+	} while (ret < 0);
+
+	return ret;
+}
+
+/**
+ * timer_delete_sync - Deactivate a timer and wait for the handler to finish.
+ * @timer:	The timer to be deactivated
+ *
+ * Synchronization rules: Callers must prevent restarting of the timer,
+ * otherwise this function is meaningless. It must not be called from
+ * interrupt contexts unless the timer is an irqsafe one. The caller must
+ * not hold locks which would prevent completion of the timer's callback
+ * function. The timer's handler must not call add_timer_on(). Upon exit
+ * the timer is not queued and the handler is not running on any CPU.
+ *
+ * For !irqsafe timers, the caller must not hold locks that are held in
+ * interrupt context. Even if the lock has nothing to do with the timer in
+ * question.  Here's why::
+ *
+ *    CPU0                             CPU1
+ *    ----                             ----
+ *                                     <SOFTIRQ>
+ *                                       call_timer_fn();
+ *                                       base->running_timer = mytimer;
+ *    spin_lock_irq(somelock);
+ *                                     <IRQ>
+ *                                        spin_lock(somelock);
+ *    timer_delete_sync(mytimer);
+ *    while (base->running_timer == mytimer);
+ *
+ * Now timer_delete_sync() will never return and never release somelock.
+ * The interrupt on the other CPU is waiting to grab somelock but it has
+ * interrupted the softirq that CPU0 is waiting to finish.
+ *
+ * This function cannot guarantee that the timer is not rearmed again by
+ * some concurrent or preempting code, right after it dropped the base
+ * lock. If there is the possibility of a concurrent rearm then the return
+ * value of the function is meaningless.
+ *
+ * If such a guarantee is needed, e.g. for teardown situations then use
+ * timer_shutdown_sync() instead.
+ *
+ * Return:
+ * * %0	- The timer was not pending
+ * * %1	- The timer was pending and deactivated
+ */
+int timer_delete_sync(struct timer_list *timer)
+{
+	return __timer_delete_sync(timer, false);
+}
+EXPORT_SYMBOL(timer_delete_sync);
+
+/**
+ * timer_shutdown_sync - Shutdown a timer and prevent rearming
+ * @timer: The timer to be shutdown
+ *
+ * When the function returns it is guaranteed that:
+ *   - @timer is not queued
+ *   - The callback function of @timer is not running
+ *   - @timer cannot be enqueued again. Any attempt to rearm
+ *     @timer is silently ignored.
+ *
+ * See timer_delete_sync() for synchronization rules.
+ *
+ * This function is useful for final teardown of an infrastructure where
+ * the timer is subject to a circular dependency problem.
+ *
+ * A common pattern for this is a timer and a workqueue where the timer can
+ * schedule work and work can arm the timer. On shutdown the workqueue must
+ * be destroyed and the timer must be prevented from rearming. Unless the
+ * code has conditionals like 'if (mything->in_shutdown)' to prevent that
+ * there is no way to get this correct with timer_delete_sync().
+ *
+ * timer_shutdown_sync() is solving the problem. The correct ordering of
+ * calls in this case is:
+ *
+ *	timer_shutdown_sync(&mything->timer);
+ *	workqueue_destroy(&mything->workqueue);
+ *
+ * After this 'mything' can be safely freed.
+ *
+ * This obviously implies that the timer is not required to be functional
+ * for the rest of the shutdown operation.
+ *
+ * Return:
+ * * %0 - The timer was not pending
+ * * %1 - The timer was pending
+ */
+int timer_shutdown_sync(struct timer_list *timer)
+{
+	return __timer_delete_sync(timer, true);
+}
+EXPORT_SYMBOL_GPL(timer_shutdown_sync);
+
+static void call_timer_fn(struct timer_list *timer,
+			  void (*fn)(struct timer_list *),
+			  unsigned long baseclk)
+{
+	int count = preempt_count();
+
+#ifdef CONFIG_LOCKDEP
+	/*
+	 * It is permissible to free the timer from inside the
+	 * function that is called from it, this we need to take into
+	 * account for lockdep too. To avoid bogus "held lock freed"
+	 * warnings as well as problems when looking into
+	 * timer->lockdep_map, make a copy and use that here.
+	 */
+	struct lockdep_map lockdep_map;
+
+	lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
+#endif
+	/*
+	 * Couple the lock chain with the lock chain at
+	 * timer_delete_sync() by acquiring the lock_map around the fn()
+	 * call here and in timer_delete_sync().
+	 */
+	lock_map_acquire(&lockdep_map);
+
+	trace_timer_expire_entry(timer, baseclk);
+	fn(timer);
+	trace_timer_expire_exit(timer);
+
+	lock_map_release(&lockdep_map);
+
+	if (count != preempt_count()) {
+		WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
+			  fn, count, preempt_count());
+		/*
+		 * Restore the preempt count. That gives us a decent
+		 * chance to survive and extract information. If the
+		 * callback kept a lock held, bad luck, but not worse
+		 * than the BUG() we had.
+		 */
+		preempt_count_set(count);
+	}
+}
+
+static void expire_timers(struct timer_base *base, struct hlist_head *head)
+{
+	/*
+	 * This value is required only for tracing. base->clk was
+	 * incremented directly before expire_timers was called. But expiry
+	 * is related to the old base->clk value.
+	 */
+	unsigned long baseclk = base->clk - 1;
+
+	while (!hlist_empty(head)) {
+		struct timer_list *timer;
+		void (*fn)(struct timer_list *);
+
+		timer = hlist_entry(head->first, struct timer_list, entry);
+
+		base->running_timer = timer;
+		detach_timer(timer, true);
+
+		fn = timer->function;
+
+		if (WARN_ON_ONCE(!fn)) {
+			/* Should never happen. Emphasis on should! */
+			base->running_timer = NULL;
+			continue;
+		}
+
+		if (timer->flags & TIMER_IRQSAFE) {
+			raw_spin_unlock(&base->lock);
+			call_timer_fn(timer, fn, baseclk);
+			raw_spin_lock(&base->lock);
+			base->running_timer = NULL;
+		} else {
+			raw_spin_unlock_irq(&base->lock);
+			call_timer_fn(timer, fn, baseclk);
+			raw_spin_lock_irq(&base->lock);
+			base->running_timer = NULL;
+			timer_sync_wait_running(base);
+		}
+	}
+}
+
+static int collect_expired_timers(struct timer_base *base,
+				  struct hlist_head *heads)
+{
+	unsigned long clk = base->clk = base->next_expiry;
+	struct hlist_head *vec;
+	int i, levels = 0;
+	unsigned int idx;
+
+	for (i = 0; i < LVL_DEPTH; i++) {
+		idx = (clk & LVL_MASK) + i * LVL_SIZE;
+
+		if (__test_and_clear_bit(idx, base->pending_map)) {
+			vec = base->vectors + idx;
+			hlist_move_list(vec, heads++);
+			levels++;
+		}
+		/* Is it time to look at the next level? */
+		if (clk & LVL_CLK_MASK)
+			break;
+		/* Shift clock for the next level granularity */
+		clk >>= LVL_CLK_SHIFT;
+	}
+	return levels;
+}
+
+/*
+ * Find the next pending bucket of a level. Search from level start (@offset)
+ * + @clk upwards and if nothing there, search from start of the level
+ * (@offset) up to @offset + clk.
+ */
+static int next_pending_bucket(struct timer_base *base, unsigned offset,
+			       unsigned clk)
+{
+	unsigned pos, start = offset + clk;
+	unsigned end = offset + LVL_SIZE;
+
+	pos = find_next_bit(base->pending_map, end, start);
+	if (pos < end)
+		return pos - start;
+
+	pos = find_next_bit(base->pending_map, start, offset);
+	return pos < start ? pos + LVL_SIZE - start : -1;
+}
+
+/*
+ * Search the first expiring timer in the various clock levels. Caller must
+ * hold base->lock.
+ */
+static unsigned long __next_timer_interrupt(struct timer_base *base)
+{
+	unsigned long clk, next, adj;
+	unsigned lvl, offset = 0;
+
+	next = base->clk + NEXT_TIMER_MAX_DELTA;
+	clk = base->clk;
+	for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
+		int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
+		unsigned long lvl_clk = clk & LVL_CLK_MASK;
+
+		if (pos >= 0) {
+			unsigned long tmp = clk + (unsigned long) pos;
+
+			tmp <<= LVL_SHIFT(lvl);
+			if (time_before(tmp, next))
+				next = tmp;
+
+			/*
+			 * If the next expiration happens before we reach
+			 * the next level, no need to check further.
+			 */
+			if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
+				break;
+		}
+		/*
+		 * Clock for the next level. If the current level clock lower
+		 * bits are zero, we look at the next level as is. If not we
+		 * need to advance it by one because that's going to be the
+		 * next expiring bucket in that level. base->clk is the next
+		 * expiring jiffie. So in case of:
+		 *
+		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+		 *  0    0    0    0    0    0
+		 *
+		 * we have to look at all levels @index 0. With
+		 *
+		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+		 *  0    0    0    0    0    2
+		 *
+		 * LVL0 has the next expiring bucket @index 2. The upper
+		 * levels have the next expiring bucket @index 1.
+		 *
+		 * In case that the propagation wraps the next level the same
+		 * rules apply:
+		 *
+		 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
+		 *  0    0    0    0    F    2
+		 *
+		 * So after looking at LVL0 we get:
+		 *
+		 * LVL5 LVL4 LVL3 LVL2 LVL1
+		 *  0    0    0    1    0
+		 *
+		 * So no propagation from LVL1 to LVL2 because that happened
+		 * with the add already, but then we need to propagate further
+		 * from LVL2 to LVL3.
+		 *
+		 * So the simple check whether the lower bits of the current
+		 * level are 0 or not is sufficient for all cases.
+		 */
+		adj = lvl_clk ? 1 : 0;
+		clk >>= LVL_CLK_SHIFT;
+		clk += adj;
+	}
+
+	base->next_expiry_recalc = false;
+	base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
+
+	return next;
+}
+
+#ifdef CONFIG_NO_HZ_COMMON
+/*
+ * Check, if the next hrtimer event is before the next timer wheel
+ * event:
+ */
+static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
+{
+	u64 nextevt = hrtimer_get_next_event();
+
+	/*
+	 * If high resolution timers are enabled
+	 * hrtimer_get_next_event() returns KTIME_MAX.
+	 */
+	if (expires <= nextevt)
+		return expires;
+
+	/*
+	 * If the next timer is already expired, return the tick base
+	 * time so the tick is fired immediately.
+	 */
+	if (nextevt <= basem)
+		return basem;
+
+	/*
+	 * Round up to the next jiffie. High resolution timers are
+	 * off, so the hrtimers are expired in the tick and we need to
+	 * make sure that this tick really expires the timer to avoid
+	 * a ping pong of the nohz stop code.
+	 *
+	 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
+	 */
+	return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
+}
+
+/**
+ * get_next_timer_interrupt - return the time (clock mono) of the next timer
+ * @basej:	base time jiffies
+ * @basem:	base time clock monotonic
+ *
+ * Returns the tick aligned clock monotonic time of the next pending
+ * timer or KTIME_MAX if no timer is pending.
+ */
+u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+	u64 expires = KTIME_MAX;
+	unsigned long nextevt;
+
+	/*
+	 * Pretend that there is no timer pending if the cpu is offline.
+	 * Possible pending timers will be migrated later to an active cpu.
+	 */
+	if (cpu_is_offline(smp_processor_id()))
+		return expires;
+
+	raw_spin_lock(&base->lock);
+	if (base->next_expiry_recalc)
+		base->next_expiry = __next_timer_interrupt(base);
+	nextevt = base->next_expiry;
+
+	/*
+	 * We have a fresh next event. Check whether we can forward the
+	 * base. We can only do that when @basej is past base->clk
+	 * otherwise we might rewind base->clk.
+	 */
+	if (time_after(basej, base->clk)) {
+		if (time_after(nextevt, basej))
+			base->clk = basej;
+		else if (time_after(nextevt, base->clk))
+			base->clk = nextevt;
+	}
+
+	if (time_before_eq(nextevt, basej)) {
+		expires = basem;
+		base->is_idle = false;
+	} else {
+		if (base->timers_pending)
+			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
+		/*
+		 * If we expect to sleep more than a tick, mark the base idle.
+		 * Also the tick is stopped so any added timer must forward
+		 * the base clk itself to keep granularity small. This idle
+		 * logic is only maintained for the BASE_STD base, deferrable
+		 * timers may still see large granularity skew (by design).
+		 */
+		if ((expires - basem) > TICK_NSEC)
+			base->is_idle = true;
+	}
+	raw_spin_unlock(&base->lock);
+
+	return cmp_next_hrtimer_event(basem, expires);
+}
+
+/**
+ * timer_clear_idle - Clear the idle state of the timer base
+ *
+ * Called with interrupts disabled
+ */
+void timer_clear_idle(void)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
+	/*
+	 * We do this unlocked. The worst outcome is a remote enqueue sending
+	 * a pointless IPI, but taking the lock would just make the window for
+	 * sending the IPI a few instructions smaller for the cost of taking
+	 * the lock in the exit from idle path.
+	 */
+	base->is_idle = false;
+}
+#endif
+
+/**
+ * __run_timers - run all expired timers (if any) on this CPU.
+ * @base: the timer vector to be processed.
+ */
+static inline void __run_timers(struct timer_base *base)
+{
+	struct hlist_head heads[LVL_DEPTH];
+	int levels;
+
+	if (time_before(jiffies, base->next_expiry))
+		return;
+
+	timer_base_lock_expiry(base);
+	raw_spin_lock_irq(&base->lock);
+
+	while (time_after_eq(jiffies, base->clk) &&
+	       time_after_eq(jiffies, base->next_expiry)) {
+		levels = collect_expired_timers(base, heads);
+		/*
+		 * The two possible reasons for not finding any expired
+		 * timer at this clk are that all matching timers have been
+		 * dequeued or no timer has been queued since
+		 * base::next_expiry was set to base::clk +
+		 * NEXT_TIMER_MAX_DELTA.
+		 */
+		WARN_ON_ONCE(!levels && !base->next_expiry_recalc
+			     && base->timers_pending);
+		base->clk++;
+		base->next_expiry = __next_timer_interrupt(base);
+
+		while (levels--)
+			expire_timers(base, heads + levels);
+	}
+	raw_spin_unlock_irq(&base->lock);
+	timer_base_unlock_expiry(base);
+}
+
+/*
+ * This function runs timers and the timer-tq in bottom half context.
+ */
+static __latent_entropy void run_timer_softirq(struct softirq_action *h)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
+	__run_timers(base);
+	if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
+		__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
+}
+
+/*
+ * Called by the local, per-CPU timer interrupt on SMP.
+ */
+static void run_local_timers(void)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
+
+	hrtimer_run_queues();
+	/* Raise the softirq only if required. */
+	if (time_before(jiffies, base->next_expiry)) {
+		if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
+			return;
+		/* CPU is awake, so check the deferrable base. */
+		base++;
+		if (time_before(jiffies, base->next_expiry))
+			return;
+	}
+	raise_softirq(TIMER_SOFTIRQ);
+}
+
+/*
+ * Called from the timer interrupt handler to charge one tick to the current
+ * process.  user_tick is 1 if the tick is user time, 0 for system.
+ */
+void update_process_times(int user_tick)
+{
+	struct task_struct *p = current;
+
+	/* Note: this timer irq context must be accounted for as well. */
+	account_process_tick(p, user_tick);
+	run_local_timers();
+	rcu_sched_clock_irq(user_tick);
+#ifdef CONFIG_IRQ_WORK
+	if (in_irq())
+		irq_work_tick();
+#endif
+	scheduler_tick();
+	if (IS_ENABLED(CONFIG_POSIX_TIMERS))
+		run_posix_cpu_timers();
+}
+
+/*
+ * Since schedule_timeout()'s timer is defined on the stack, it must store
+ * the target task on the stack as well.
+ */
+struct process_timer {
+	struct timer_list timer;
+	struct task_struct *task;
+};
+
+static void process_timeout(struct timer_list *t)
+{
+	struct process_timer *timeout = from_timer(timeout, t, timer);
+
+	wake_up_process(timeout->task);
+}
+
+/**
+ * schedule_timeout - sleep until timeout
+ * @timeout: timeout value in jiffies
+ *
+ * Make the current task sleep until @timeout jiffies have elapsed.
+ * The function behavior depends on the current task state
+ * (see also set_current_state() description):
+ *
+ * %TASK_RUNNING - the scheduler is called, but the task does not sleep
+ * at all. That happens because sched_submit_work() does nothing for
+ * tasks in %TASK_RUNNING state.
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process()).
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task or the current task is explicitly woken
+ * up.
+ *
+ * The current task state is guaranteed to be %TASK_RUNNING when this
+ * routine returns.
+ *
+ * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
+ * the CPU away without a bound on the timeout. In this case the return
+ * value will be %MAX_SCHEDULE_TIMEOUT.
+ *
+ * Returns 0 when the timer has expired otherwise the remaining time in
+ * jiffies will be returned. In all cases the return value is guaranteed
+ * to be non-negative.
+ */
+signed long __sched schedule_timeout(signed long timeout)
+{
+	struct process_timer timer;
+	unsigned long expire;
+
+	switch (timeout)
+	{
+	case MAX_SCHEDULE_TIMEOUT:
+		/*
+		 * These two special cases are useful to be comfortable
+		 * in the caller. Nothing more. We could take
+		 * MAX_SCHEDULE_TIMEOUT from one of the negative value
+		 * but I' d like to return a valid offset (>=0) to allow
+		 * the caller to do everything it want with the retval.
+		 */
+		schedule();
+		goto out;
+	default:
+		/*
+		 * Another bit of PARANOID. Note that the retval will be
+		 * 0 since no piece of kernel is supposed to do a check
+		 * for a negative retval of schedule_timeout() (since it
+		 * should never happens anyway). You just have the printk()
+		 * that will tell you if something is gone wrong and where.
+		 */
+		if (timeout < 0) {
+			printk(KERN_ERR "schedule_timeout: wrong timeout "
+				"value %lx\n", timeout);
+			dump_stack();
+			__set_current_state(TASK_RUNNING);
+			goto out;
+		}
+	}
+
+	expire = timeout + jiffies;
+
+	timer.task = current;
+	timer_setup_on_stack(&timer.timer, process_timeout, 0);
+	__mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
+	schedule();
+	del_timer_sync(&timer.timer);
+
+	/* Remove the timer from the object tracker */
+	destroy_timer_on_stack(&timer.timer);
+
+	timeout = expire - jiffies;
+
+ out:
+	return timeout < 0 ? 0 : timeout;
+}
+EXPORT_SYMBOL(schedule_timeout);
+
+/*
+ * We can use __set_current_state() here because schedule_timeout() calls
+ * schedule() unconditionally.
+ */
+signed long __sched schedule_timeout_interruptible(signed long timeout)
+{
+	__set_current_state(TASK_INTERRUPTIBLE);
+	return schedule_timeout(timeout);
+}
+EXPORT_SYMBOL(schedule_timeout_interruptible);
+
+signed long __sched schedule_timeout_killable(signed long timeout)
+{
+	__set_current_state(TASK_KILLABLE);
+	return schedule_timeout(timeout);
+}
+EXPORT_SYMBOL(schedule_timeout_killable);
+
+signed long __sched schedule_timeout_uninterruptible(signed long timeout)
+{
+	__set_current_state(TASK_UNINTERRUPTIBLE);
+	return schedule_timeout(timeout);
+}
+EXPORT_SYMBOL(schedule_timeout_uninterruptible);
+
+/*
+ * Like schedule_timeout_uninterruptible(), except this task will not contribute
+ * to load average.
+ */
+signed long __sched schedule_timeout_idle(signed long timeout)
+{
+	__set_current_state(TASK_IDLE);
+	return schedule_timeout(timeout);
+}
+EXPORT_SYMBOL(schedule_timeout_idle);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
+{
+	struct timer_list *timer;
+	int cpu = new_base->cpu;
+
+	while (!hlist_empty(head)) {
+		timer = hlist_entry(head->first, struct timer_list, entry);
+		detach_timer(timer, false);
+		timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
+		internal_add_timer(new_base, timer);
+	}
+}
+
+int timers_prepare_cpu(unsigned int cpu)
+{
+	struct timer_base *base;
+	int b;
+
+	for (b = 0; b < NR_BASES; b++) {
+		base = per_cpu_ptr(&timer_bases[b], cpu);
+		base->clk = jiffies;
+		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
+		base->next_expiry_recalc = false;
+		base->timers_pending = false;
+		base->is_idle = false;
+	}
+	return 0;
+}
+
+int timers_dead_cpu(unsigned int cpu)
+{
+	struct timer_base *old_base;
+	struct timer_base *new_base;
+	int b, i;
+
+	for (b = 0; b < NR_BASES; b++) {
+		old_base = per_cpu_ptr(&timer_bases[b], cpu);
+		new_base = get_cpu_ptr(&timer_bases[b]);
+		/*
+		 * The caller is globally serialized and nobody else
+		 * takes two locks at once, deadlock is not possible.
+		 */
+		raw_spin_lock_irq(&new_base->lock);
+		raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+
+		/*
+		 * The current CPUs base clock might be stale. Update it
+		 * before moving the timers over.
+		 */
+		forward_timer_base(new_base);
+
+		WARN_ON_ONCE(old_base->running_timer);
+		old_base->running_timer = NULL;
+
+		for (i = 0; i < WHEEL_SIZE; i++)
+			migrate_timer_list(new_base, old_base->vectors + i);
+
+		raw_spin_unlock(&old_base->lock);
+		raw_spin_unlock_irq(&new_base->lock);
+		put_cpu_ptr(&timer_bases);
+	}
+	return 0;
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static void __init init_timer_cpu(int cpu)
+{
+	struct timer_base *base;
+	int i;
+
+	for (i = 0; i < NR_BASES; i++) {
+		base = per_cpu_ptr(&timer_bases[i], cpu);
+		base->cpu = cpu;
+		raw_spin_lock_init(&base->lock);
+		base->clk = jiffies;
+		base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
+		timer_base_init_expiry_lock(base);
+	}
+}
+
+static void __init init_timer_cpus(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		init_timer_cpu(cpu);
+}
+
+void __init init_timers(void)
+{
+	init_timer_cpus();
+	posix_cputimers_init_work();
+	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
+}
+
+/**
+ * msleep - sleep safely even with waitqueue interruptions
+ * @msecs: Time in milliseconds to sleep for
+ */
+void msleep(unsigned int msecs)
+{
+	unsigned long timeout = msecs_to_jiffies(msecs) + 1;
+
+	while (timeout)
+		timeout = schedule_timeout_uninterruptible(timeout);
+}
+
+EXPORT_SYMBOL(msleep);
+
+/**
+ * msleep_interruptible - sleep waiting for signals
+ * @msecs: Time in milliseconds to sleep for
+ */
+unsigned long msleep_interruptible(unsigned int msecs)
+{
+	unsigned long timeout = msecs_to_jiffies(msecs) + 1;
+
+	while (timeout && !signal_pending(current))
+		timeout = schedule_timeout_interruptible(timeout);
+	return jiffies_to_msecs(timeout);
+}
+
+EXPORT_SYMBOL(msleep_interruptible);
+
+/**
+ * usleep_range_state - Sleep for an approximate time in a given state
+ * @min:	Minimum time in usecs to sleep
+ * @max:	Maximum time in usecs to sleep
+ * @state:	State of the current task that will be while sleeping
+ *
+ * In non-atomic context where the exact wakeup time is flexible, use
+ * usleep_range_state() instead of udelay().  The sleep improves responsiveness
+ * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
+ * power usage by allowing hrtimers to take advantage of an already-
+ * scheduled interrupt instead of scheduling a new one just for this sleep.
+ */
+void __sched usleep_range_state(unsigned long min, unsigned long max,
+				unsigned int state)
+{
+	ktime_t exp = ktime_add_us(ktime_get(), min);
+	u64 delta = (u64)(max - min) * NSEC_PER_USEC;
+
+	for (;;) {
+		__set_current_state(state);
+		/* Do not return before the requested sleep time has elapsed */
+		if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
+			break;
+	}
+}
+EXPORT_SYMBOL(usleep_range_state);
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
new file mode 100644
index 0000000000..ed7d6ad694
--- /dev/null
+++ b/kernel/time/timer_list.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * List pending timers
+ *
+ * Copyright(C) 2006, Red Hat, Inc., Ingo Molnar
+ */
+
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/kallsyms.h>
+#include <linux/nmi.h>
+
+#include <linux/uaccess.h>
+
+#include "tick-internal.h"
+
+struct timer_list_iter {
+	int cpu;
+	bool second_pass;
+	u64 now;
+};
+
+/*
+ * This allows printing both to /proc/timer_list and
+ * to the console (on SysRq-Q):
+ */
+__printf(2, 3)
+static void SEQ_printf(struct seq_file *m, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+
+	if (m)
+		seq_vprintf(m, fmt, args);
+	else
+		vprintk(fmt, args);
+
+	va_end(args);
+}
+
+static void
+print_timer(struct seq_file *m, struct hrtimer *taddr, struct hrtimer *timer,
+	    int idx, u64 now)
+{
+	SEQ_printf(m, " #%d: <%pK>, %ps", idx, taddr, timer->function);
+	SEQ_printf(m, ", S:%02x", timer->state);
+	SEQ_printf(m, "\n");
+	SEQ_printf(m, " # expires at %Lu-%Lu nsecs [in %Ld to %Ld nsecs]\n",
+		(unsigned long long)ktime_to_ns(hrtimer_get_softexpires(timer)),
+		(unsigned long long)ktime_to_ns(hrtimer_get_expires(timer)),
+		(long long)(ktime_to_ns(hrtimer_get_softexpires(timer)) - now),
+		(long long)(ktime_to_ns(hrtimer_get_expires(timer)) - now));
+}
+
+static void
+print_active_timers(struct seq_file *m, struct hrtimer_clock_base *base,
+		    u64 now)
+{
+	struct hrtimer *timer, tmp;
+	unsigned long next = 0, i;
+	struct timerqueue_node *curr;
+	unsigned long flags;
+
+next_one:
+	i = 0;
+
+	touch_nmi_watchdog();
+
+	raw_spin_lock_irqsave(&base->cpu_base->lock, flags);
+
+	curr = timerqueue_getnext(&base->active);
+	/*
+	 * Crude but we have to do this O(N*N) thing, because
+	 * we have to unlock the base when printing:
+	 */
+	while (curr && i < next) {
+		curr = timerqueue_iterate_next(curr);
+		i++;
+	}
+
+	if (curr) {
+
+		timer = container_of(curr, struct hrtimer, node);
+		tmp = *timer;
+		raw_spin_unlock_irqrestore(&base->cpu_base->lock, flags);
+
+		print_timer(m, timer, &tmp, i, now);
+		next++;
+		goto next_one;
+	}
+	raw_spin_unlock_irqrestore(&base->cpu_base->lock, flags);
+}
+
+static void
+print_base(struct seq_file *m, struct hrtimer_clock_base *base, u64 now)
+{
+	SEQ_printf(m, "  .base:       %pK\n", base);
+	SEQ_printf(m, "  .index:      %d\n", base->index);
+
+	SEQ_printf(m, "  .resolution: %u nsecs\n", hrtimer_resolution);
+
+	SEQ_printf(m,   "  .get_time:   %ps\n", base->get_time);
+#ifdef CONFIG_HIGH_RES_TIMERS
+	SEQ_printf(m, "  .offset:     %Lu nsecs\n",
+		   (unsigned long long) ktime_to_ns(base->offset));
+#endif
+	SEQ_printf(m,   "active timers:\n");
+	print_active_timers(m, base, now + ktime_to_ns(base->offset));
+}
+
+static void print_cpu(struct seq_file *m, int cpu, u64 now)
+{
+	struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
+	int i;
+
+	SEQ_printf(m, "cpu: %d\n", cpu);
+	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
+		SEQ_printf(m, " clock %d:\n", i);
+		print_base(m, cpu_base->clock_base + i, now);
+	}
+#define P(x) \
+	SEQ_printf(m, "  .%-15s: %Lu\n", #x, \
+		   (unsigned long long)(cpu_base->x))
+#define P_ns(x) \
+	SEQ_printf(m, "  .%-15s: %Lu nsecs\n", #x, \
+		   (unsigned long long)(ktime_to_ns(cpu_base->x)))
+
+#ifdef CONFIG_HIGH_RES_TIMERS
+	P_ns(expires_next);
+	P(hres_active);
+	P(nr_events);
+	P(nr_retries);
+	P(nr_hangs);
+	P(max_hang_time);
+#endif
+#undef P
+#undef P_ns
+
+#ifdef CONFIG_TICK_ONESHOT
+# define P(x) \
+	SEQ_printf(m, "  .%-15s: %Lu\n", #x, \
+		   (unsigned long long)(ts->x))
+# define P_ns(x) \
+	SEQ_printf(m, "  .%-15s: %Lu nsecs\n", #x, \
+		   (unsigned long long)(ktime_to_ns(ts->x)))
+	{
+		struct tick_sched *ts = tick_get_tick_sched(cpu);
+		P(nohz_mode);
+		P_ns(last_tick);
+		P(tick_stopped);
+		P(idle_jiffies);
+		P(idle_calls);
+		P(idle_sleeps);
+		P_ns(idle_entrytime);
+		P_ns(idle_waketime);
+		P_ns(idle_exittime);
+		P_ns(idle_sleeptime);
+		P_ns(iowait_sleeptime);
+		P(last_jiffies);
+		P(next_timer);
+		P_ns(idle_expires);
+		SEQ_printf(m, "jiffies: %Lu\n",
+			   (unsigned long long)jiffies);
+	}
+#endif
+
+#undef P
+#undef P_ns
+	SEQ_printf(m, "\n");
+}
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+static void
+print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
+{
+	struct clock_event_device *dev = td->evtdev;
+
+	touch_nmi_watchdog();
+
+	SEQ_printf(m, "Tick Device: mode:     %d\n", td->mode);
+	if (cpu < 0)
+		SEQ_printf(m, "Broadcast device\n");
+	else
+		SEQ_printf(m, "Per CPU device: %d\n", cpu);
+
+	SEQ_printf(m, "Clock Event Device: ");
+	if (!dev) {
+		SEQ_printf(m, "<NULL>\n");
+		return;
+	}
+	SEQ_printf(m, "%s\n", dev->name);
+	SEQ_printf(m, " max_delta_ns:   %llu\n",
+		   (unsigned long long) dev->max_delta_ns);
+	SEQ_printf(m, " min_delta_ns:   %llu\n",
+		   (unsigned long long) dev->min_delta_ns);
+	SEQ_printf(m, " mult:           %u\n", dev->mult);
+	SEQ_printf(m, " shift:          %u\n", dev->shift);
+	SEQ_printf(m, " mode:           %d\n", clockevent_get_state(dev));
+	SEQ_printf(m, " next_event:     %Ld nsecs\n",
+		   (unsigned long long) ktime_to_ns(dev->next_event));
+
+	SEQ_printf(m, " set_next_event: %ps\n", dev->set_next_event);
+
+	if (dev->set_state_shutdown)
+		SEQ_printf(m, " shutdown:       %ps\n",
+			dev->set_state_shutdown);
+
+	if (dev->set_state_periodic)
+		SEQ_printf(m, " periodic:       %ps\n",
+			dev->set_state_periodic);
+
+	if (dev->set_state_oneshot)
+		SEQ_printf(m, " oneshot:        %ps\n",
+			dev->set_state_oneshot);
+
+	if (dev->set_state_oneshot_stopped)
+		SEQ_printf(m, " oneshot stopped: %ps\n",
+			dev->set_state_oneshot_stopped);
+
+	if (dev->tick_resume)
+		SEQ_printf(m, " resume:         %ps\n",
+			dev->tick_resume);
+
+	SEQ_printf(m, " event_handler:  %ps\n", dev->event_handler);
+	SEQ_printf(m, "\n");
+	SEQ_printf(m, " retries:        %lu\n", dev->retries);
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+	if (cpu >= 0) {
+		const struct clock_event_device *wd = tick_get_wakeup_device(cpu);
+
+		SEQ_printf(m, "Wakeup Device: %s\n", wd ? wd->name : "<NULL>");
+	}
+#endif
+	SEQ_printf(m, "\n");
+}
+
+static void timer_list_show_tickdevices_header(struct seq_file *m)
+{
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+	print_tickdevice(m, tick_get_broadcast_device(), -1);
+	SEQ_printf(m, "tick_broadcast_mask: %*pb\n",
+		   cpumask_pr_args(tick_get_broadcast_mask()));
+#ifdef CONFIG_TICK_ONESHOT
+	SEQ_printf(m, "tick_broadcast_oneshot_mask: %*pb\n",
+		   cpumask_pr_args(tick_get_broadcast_oneshot_mask()));
+#endif
+	SEQ_printf(m, "\n");
+#endif
+}
+#endif
+
+static inline void timer_list_header(struct seq_file *m, u64 now)
+{
+	SEQ_printf(m, "Timer List Version: v0.9\n");
+	SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
+	SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
+	SEQ_printf(m, "\n");
+}
+
+void sysrq_timer_list_show(void)
+{
+	u64 now = ktime_to_ns(ktime_get());
+	int cpu;
+
+	timer_list_header(NULL, now);
+
+	for_each_online_cpu(cpu)
+		print_cpu(NULL, cpu, now);
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+	timer_list_show_tickdevices_header(NULL);
+	for_each_online_cpu(cpu)
+		print_tickdevice(NULL, tick_get_device(cpu), cpu);
+#endif
+	return;
+}
+
+#ifdef CONFIG_PROC_FS
+static int timer_list_show(struct seq_file *m, void *v)
+{
+	struct timer_list_iter *iter = v;
+
+	if (iter->cpu == -1 && !iter->second_pass)
+		timer_list_header(m, iter->now);
+	else if (!iter->second_pass)
+		print_cpu(m, iter->cpu, iter->now);
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+	else if (iter->cpu == -1 && iter->second_pass)
+		timer_list_show_tickdevices_header(m);
+	else
+		print_tickdevice(m, tick_get_device(iter->cpu), iter->cpu);
+#endif
+	return 0;
+}
+
+static void *move_iter(struct timer_list_iter *iter, loff_t offset)
+{
+	for (; offset; offset--) {
+		iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
+		if (iter->cpu >= nr_cpu_ids) {
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+			if (!iter->second_pass) {
+				iter->cpu = -1;
+				iter->second_pass = true;
+			} else
+				return NULL;
+#else
+			return NULL;
+#endif
+		}
+	}
+	return iter;
+}
+
+static void *timer_list_start(struct seq_file *file, loff_t *offset)
+{
+	struct timer_list_iter *iter = file->private;
+
+	if (!*offset)
+		iter->now = ktime_to_ns(ktime_get());
+	iter->cpu = -1;
+	iter->second_pass = false;
+	return move_iter(iter, *offset);
+}
+
+static void *timer_list_next(struct seq_file *file, void *v, loff_t *offset)
+{
+	struct timer_list_iter *iter = file->private;
+	++*offset;
+	return move_iter(iter, 1);
+}
+
+static void timer_list_stop(struct seq_file *seq, void *v)
+{
+}
+
+static const struct seq_operations timer_list_sops = {
+	.start = timer_list_start,
+	.next = timer_list_next,
+	.stop = timer_list_stop,
+	.show = timer_list_show,
+};
+
+static int __init init_timer_list_procfs(void)
+{
+	struct proc_dir_entry *pe;
+
+	pe = proc_create_seq_private("timer_list", 0400, NULL, &timer_list_sops,
+			sizeof(struct timer_list_iter), NULL);
+	if (!pe)
+		return -ENOMEM;
+	return 0;
+}
+__initcall(init_timer_list_procfs);
+#endif
diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
new file mode 100644
index 0000000000..f0d5062d9c
--- /dev/null
+++ b/kernel/time/vsyscall.c
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 ARM Ltd.
+ *
+ * Generic implementation of update_vsyscall and update_vsyscall_tz.
+ *
+ * Based on the x86 specific implementation.
+ */
+
+#include <linux/hrtimer.h>
+#include <linux/timekeeper_internal.h>
+#include <vdso/datapage.h>
+#include <vdso/helpers.h>
+#include <vdso/vsyscall.h>
+
+#include "timekeeping_internal.h"
+
+static inline void update_vdso_data(struct vdso_data *vdata,
+				    struct timekeeper *tk)
+{
+	struct vdso_timestamp *vdso_ts;
+	u64 nsec, sec;
+
+	vdata[CS_HRES_COARSE].cycle_last	= tk->tkr_mono.cycle_last;
+	vdata[CS_HRES_COARSE].mask		= tk->tkr_mono.mask;
+	vdata[CS_HRES_COARSE].mult		= tk->tkr_mono.mult;
+	vdata[CS_HRES_COARSE].shift		= tk->tkr_mono.shift;
+	vdata[CS_RAW].cycle_last		= tk->tkr_raw.cycle_last;
+	vdata[CS_RAW].mask			= tk->tkr_raw.mask;
+	vdata[CS_RAW].mult			= tk->tkr_raw.mult;
+	vdata[CS_RAW].shift			= tk->tkr_raw.shift;
+
+	/* CLOCK_MONOTONIC */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
+	vdso_ts->sec	= tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
+
+	nsec = tk->tkr_mono.xtime_nsec;
+	nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
+	while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
+		nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
+		vdso_ts->sec++;
+	}
+	vdso_ts->nsec	= nsec;
+
+	/* Copy MONOTONIC time for BOOTTIME */
+	sec	= vdso_ts->sec;
+	/* Add the boot offset */
+	sec	+= tk->monotonic_to_boot.tv_sec;
+	nsec	+= (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
+
+	/* CLOCK_BOOTTIME */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
+	vdso_ts->sec	= sec;
+
+	while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
+		nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
+		vdso_ts->sec++;
+	}
+	vdso_ts->nsec	= nsec;
+
+	/* CLOCK_MONOTONIC_RAW */
+	vdso_ts		= &vdata[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
+	vdso_ts->sec	= tk->raw_sec;
+	vdso_ts->nsec	= tk->tkr_raw.xtime_nsec;
+
+	/* CLOCK_TAI */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];
+	vdso_ts->sec	= tk->xtime_sec + (s64)tk->tai_offset;
+	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;
+}
+
+void update_vsyscall(struct timekeeper *tk)
+{
+	struct vdso_data *vdata = __arch_get_k_vdso_data();
+	struct vdso_timestamp *vdso_ts;
+	s32 clock_mode;
+	u64 nsec;
+
+	/* copy vsyscall data */
+	vdso_write_begin(vdata);
+
+	clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
+	vdata[CS_HRES_COARSE].clock_mode	= clock_mode;
+	vdata[CS_RAW].clock_mode		= clock_mode;
+
+	/* CLOCK_REALTIME also required for time() */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
+	vdso_ts->sec	= tk->xtime_sec;
+	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;
+
+	/* CLOCK_REALTIME_COARSE */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
+	vdso_ts->sec	= tk->xtime_sec;
+	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
+
+	/* CLOCK_MONOTONIC_COARSE */
+	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
+	vdso_ts->sec	= tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
+	nsec		= tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
+	nsec		= nsec + tk->wall_to_monotonic.tv_nsec;
+	vdso_ts->sec	+= __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
+
+	/*
+	 * Read without the seqlock held by clock_getres().
+	 * Note: No need to have a second copy.
+	 */
+	WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
+
+	/*
+	 * If the current clocksource is not VDSO capable, then spare the
+	 * update of the high resolution parts.
+	 */
+	if (clock_mode != VDSO_CLOCKMODE_NONE)
+		update_vdso_data(vdata, tk);
+
+	__arch_update_vsyscall(vdata, tk);
+
+	vdso_write_end(vdata);
+
+	__arch_sync_vdso_data(vdata);
+}
+
+void update_vsyscall_tz(void)
+{
+	struct vdso_data *vdata = __arch_get_k_vdso_data();
+
+	vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
+	vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
+
+	__arch_sync_vdso_data(vdata);
+}
+
+/**
+ * vdso_update_begin - Start of a VDSO update section
+ *
+ * Allows architecture code to safely update the architecture specific VDSO
+ * data. Disables interrupts, acquires timekeeper lock to serialize against
+ * concurrent updates from timekeeping and invalidates the VDSO data
+ * sequence counter to prevent concurrent readers from accessing
+ * inconsistent data.
+ *
+ * Returns: Saved interrupt flags which need to be handed in to
+ * vdso_update_end().
+ */
+unsigned long vdso_update_begin(void)
+{
+	struct vdso_data *vdata = __arch_get_k_vdso_data();
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	vdso_write_begin(vdata);
+	return flags;
+}
+
+/**
+ * vdso_update_end - End of a VDSO update section
+ * @flags:	Interrupt flags as returned from vdso_update_begin()
+ *
+ * Pairs with vdso_update_begin(). Marks vdso data consistent, invokes data
+ * synchronization if the architecture requires it, drops timekeeper lock
+ * and restores interrupt flags.
+ */
+void vdso_update_end(unsigned long flags)
+{
+	struct vdso_data *vdata = __arch_get_k_vdso_data();
+
+	vdso_write_end(vdata);
+	__arch_sync_vdso_data(vdata);
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+}