Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 784 insertions, 0 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
new file mode 100644
index 000000000..6d60701dc
--- /dev/null
+++ b/kernel/watchdog.c
@@ -0,0 +1,784 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Detect hard and soft lockups on a system
+ *
+ * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
+ *
+ * Note: Most of this code is borrowed heavily from the original softlockup
+ * detector, so thanks to Ingo for the initial implementation.
+ * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
+ * to those contributors as well.
+ */
+
+#define pr_fmt(fmt) "watchdog: " fmt
+
+#include <linux/mm.h>
+#include <linux/cpu.h>
+#include <linux/nmi.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sysctl.h>
+#include <linux/tick.h>
+#include <linux/sched/clock.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/isolation.h>
+#include <linux/stop_machine.h>
+
+#include <asm/irq_regs.h>
+#include <linux/kvm_para.h>
+
+static DEFINE_MUTEX(watchdog_mutex);
+
+#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
+# define WATCHDOG_DEFAULT	(SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
+# define NMI_WATCHDOG_DEFAULT	1
+#else
+# define WATCHDOG_DEFAULT	(SOFT_WATCHDOG_ENABLED)
+# define NMI_WATCHDOG_DEFAULT	0
+#endif
+
+unsigned long __read_mostly watchdog_enabled;
+int __read_mostly watchdog_user_enabled = 1;
+int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
+int __read_mostly soft_watchdog_user_enabled = 1;
+int __read_mostly watchdog_thresh = 10;
+int __read_mostly nmi_watchdog_available;
+
+struct cpumask watchdog_allowed_mask __read_mostly;
+
+struct cpumask watchdog_cpumask __read_mostly;
+unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
+
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
+/*
+ * Should we panic when a soft-lockup or hard-lockup occurs:
+ */
+unsigned int __read_mostly hardlockup_panic =
+			CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
+/*
+ * We may not want to enable hard lockup detection by default in all cases,
+ * for example when running the kernel as a guest on a hypervisor. In these
+ * cases this function can be called to disable hard lockup detection. This
+ * function should only be executed once by the boot processor before the
+ * kernel command line parameters are parsed, because otherwise it is not
+ * possible to override this in hardlockup_panic_setup().
+ */
+void __init hardlockup_detector_disable(void)
+{
+	nmi_watchdog_user_enabled = 0;
+}
+
+static int __init hardlockup_panic_setup(char *str)
+{
+	if (!strncmp(str, "panic", 5))
+		hardlockup_panic = 1;
+	else if (!strncmp(str, "nopanic", 7))
+		hardlockup_panic = 0;
+	else if (!strncmp(str, "0", 1))
+		nmi_watchdog_user_enabled = 0;
+	else if (!strncmp(str, "1", 1))
+		nmi_watchdog_user_enabled = 1;
+	return 1;
+}
+__setup("nmi_watchdog=", hardlockup_panic_setup);
+
+# ifdef CONFIG_SMP
+int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
+
+static int __init hardlockup_all_cpu_backtrace_setup(char *str)
+{
+	sysctl_hardlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
+	return 1;
+}
+__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
+# endif /* CONFIG_SMP */
+#endif /* CONFIG_HARDLOCKUP_DETECTOR */
+
+/*
+ * These functions can be overridden if an architecture implements its
+ * own hardlockup detector.
+ *
+ * watchdog_nmi_enable/disable can be implemented to start and stop when
+ * softlockup watchdog threads start and stop. The arch must select the
+ * SOFTLOCKUP_DETECTOR Kconfig.
+ */
+int __weak watchdog_nmi_enable(unsigned int cpu)
+{
+	hardlockup_detector_perf_enable();
+	return 0;
+}
+
+void __weak watchdog_nmi_disable(unsigned int cpu)
+{
+	hardlockup_detector_perf_disable();
+}
+
+/* Return 0, if a NMI watchdog is available. Error code otherwise */
+int __weak __init watchdog_nmi_probe(void)
+{
+	return hardlockup_detector_perf_init();
+}
+
+/**
+ * watchdog_nmi_stop - Stop the watchdog for reconfiguration
+ *
+ * The reconfiguration steps are:
+ * watchdog_nmi_stop();
+ * update_variables();
+ * watchdog_nmi_start();
+ */
+void __weak watchdog_nmi_stop(void) { }
+
+/**
+ * watchdog_nmi_start - Start the watchdog after reconfiguration
+ *
+ * Counterpart to watchdog_nmi_stop().
+ *
+ * The following variables have been updated in update_variables() and
+ * contain the currently valid configuration:
+ * - watchdog_enabled
+ * - watchdog_thresh
+ * - watchdog_cpumask
+ */
+void __weak watchdog_nmi_start(void) { }
+
+/**
+ * lockup_detector_update_enable - Update the sysctl enable bit
+ *
+ * Caller needs to make sure that the NMI/perf watchdogs are off, so this
+ * can't race with watchdog_nmi_disable().
+ */
+static void lockup_detector_update_enable(void)
+{
+	watchdog_enabled = 0;
+	if (!watchdog_user_enabled)
+		return;
+	if (nmi_watchdog_available && nmi_watchdog_user_enabled)
+		watchdog_enabled |= NMI_WATCHDOG_ENABLED;
+	if (soft_watchdog_user_enabled)
+		watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
+}
+
+#ifdef CONFIG_SOFTLOCKUP_DETECTOR
+
+#define SOFTLOCKUP_RESET	ULONG_MAX
+
+/* Global variables, exported for sysctl */
+unsigned int __read_mostly softlockup_panic =
+			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
+
+static bool softlockup_initialized __read_mostly;
+static u64 __read_mostly sample_period;
+
+static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
+static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
+static DEFINE_PER_CPU(bool, softlockup_touch_sync);
+static DEFINE_PER_CPU(bool, soft_watchdog_warn);
+static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
+static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
+static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
+static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
+static unsigned long soft_lockup_nmi_warn;
+
+static int __init softlockup_panic_setup(char *str)
+{
+	softlockup_panic = simple_strtoul(str, NULL, 0);
+	return 1;
+}
+__setup("softlockup_panic=", softlockup_panic_setup);
+
+static int __init nowatchdog_setup(char *str)
+{
+	watchdog_user_enabled = 0;
+	return 1;
+}
+__setup("nowatchdog", nowatchdog_setup);
+
+static int __init nosoftlockup_setup(char *str)
+{
+	soft_watchdog_user_enabled = 0;
+	return 1;
+}
+__setup("nosoftlockup", nosoftlockup_setup);
+
+#ifdef CONFIG_SMP
+int __read_mostly sysctl_softlockup_all_cpu_backtrace;
+
+static int __init softlockup_all_cpu_backtrace_setup(char *str)
+{
+	sysctl_softlockup_all_cpu_backtrace = !!simple_strtol(str, NULL, 0);
+	return 1;
+}
+__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
+#endif
+
+static void __lockup_detector_cleanup(void);
+
+/*
+ * Hard-lockup warnings should be triggered after just a few seconds. Soft-
+ * lockups can have false positives under extreme conditions. So we generally
+ * want a higher threshold for soft lockups than for hard lockups. So we couple
+ * the thresholds with a factor: we make the soft threshold twice the amount of
+ * time the hard threshold is.
+ */
+static int get_softlockup_thresh(void)
+{
+	return watchdog_thresh * 2;
+}
+
+/*
+ * Returns seconds, approximately.  We don't need nanosecond
+ * resolution, and we don't need to waste time with a big divide when
+ * 2^30ns == 1.074s.
+ */
+static unsigned long get_timestamp(void)
+{
+	return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
+}
+
+static void set_sample_period(void)
+{
+	/*
+	 * convert watchdog_thresh from seconds to ns
+	 * the divide by 5 is to give hrtimer several chances (two
+	 * or three with the current relation between the soft
+	 * and hard thresholds) to increment before the
+	 * hardlockup detector generates a warning
+	 */
+	sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
+	watchdog_update_hrtimer_threshold(sample_period);
+}
+
+/* Commands for resetting the watchdog */
+static void __touch_watchdog(void)
+{
+	__this_cpu_write(watchdog_touch_ts, get_timestamp());
+}
+
+/**
+ * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
+ *
+ * Call when the scheduler may have stalled for legitimate reasons
+ * preventing the watchdog task from executing - e.g. the scheduler
+ * entering idle state.  This should only be used for scheduler events.
+ * Use touch_softlockup_watchdog() for everything else.
+ */
+notrace void touch_softlockup_watchdog_sched(void)
+{
+	/*
+	 * Preemption can be enabled.  It doesn't matter which CPU's timestamp
+	 * gets zeroed here, so use the raw_ operation.
+	 */
+	raw_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
+}
+
+notrace void touch_softlockup_watchdog(void)
+{
+	touch_softlockup_watchdog_sched();
+	wq_watchdog_touch(raw_smp_processor_id());
+}
+EXPORT_SYMBOL(touch_softlockup_watchdog);
+
+void touch_all_softlockup_watchdogs(void)
+{
+	int cpu;
+
+	/*
+	 * watchdog_mutex cannpt be taken here, as this might be called
+	 * from (soft)interrupt context, so the access to
+	 * watchdog_allowed_cpumask might race with a concurrent update.
+	 *
+	 * The watchdog time stamp can race against a concurrent real
+	 * update as well, the only side effect might be a cycle delay for
+	 * the softlockup check.
+	 */
+	for_each_cpu(cpu, &watchdog_allowed_mask)
+		per_cpu(watchdog_touch_ts, cpu) = SOFTLOCKUP_RESET;
+	wq_watchdog_touch(-1);
+}
+
+void touch_softlockup_watchdog_sync(void)
+{
+	__this_cpu_write(softlockup_touch_sync, true);
+	__this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
+}
+
+static int is_softlockup(unsigned long touch_ts)
+{
+	unsigned long now = get_timestamp();
+
+	if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
+		/* Warn about unreasonable delays. */
+		if (time_after(now, touch_ts + get_softlockup_thresh()))
+			return now - touch_ts;
+	}
+	return 0;
+}
+
+/* watchdog detector functions */
+bool is_hardlockup(void)
+{
+	unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
+
+	if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
+		return true;
+
+	__this_cpu_write(hrtimer_interrupts_saved, hrint);
+	return false;
+}
+
+static void watchdog_interrupt_count(void)
+{
+	__this_cpu_inc(hrtimer_interrupts);
+}
+
+static DEFINE_PER_CPU(struct completion, softlockup_completion);
+static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
+
+/*
+ * The watchdog thread function - touches the timestamp.
+ *
+ * It only runs once every sample_period seconds (4 seconds by
+ * default) to reset the softlockup timestamp. If this gets delayed
+ * for more than 2*watchdog_thresh seconds then the debug-printout
+ * triggers in watchdog_timer_fn().
+ */
+static int softlockup_fn(void *data)
+{
+	__this_cpu_write(soft_lockup_hrtimer_cnt,
+			 __this_cpu_read(hrtimer_interrupts));
+	__touch_watchdog();
+	complete(this_cpu_ptr(&softlockup_completion));
+
+	return 0;
+}
+
+/* watchdog kicker functions */
+static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
+{
+	unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
+	struct pt_regs *regs = get_irq_regs();
+	int duration;
+	int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
+
+	if (!watchdog_enabled)
+		return HRTIMER_NORESTART;
+
+	/* kick the hardlockup detector */
+	watchdog_interrupt_count();
+
+	/* kick the softlockup detector */
+	if (completion_done(this_cpu_ptr(&softlockup_completion))) {
+		reinit_completion(this_cpu_ptr(&softlockup_completion));
+		stop_one_cpu_nowait(smp_processor_id(),
+				softlockup_fn, NULL,
+				this_cpu_ptr(&softlockup_stop_work));
+	}
+
+	/* .. and repeat */
+	hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
+
+	if (touch_ts == SOFTLOCKUP_RESET) {
+		if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
+			/*
+			 * If the time stamp was touched atomically
+			 * make sure the scheduler tick is up to date.
+			 */
+			__this_cpu_write(softlockup_touch_sync, false);
+			sched_clock_tick();
+		}
+
+		/* Clear the guest paused flag on watchdog reset */
+		kvm_check_and_clear_guest_paused();
+		__touch_watchdog();
+		return HRTIMER_RESTART;
+	}
+
+	/* check for a softlockup
+	 * This is done by making sure a high priority task is
+	 * being scheduled.  The task touches the watchdog to
+	 * indicate it is getting cpu time.  If it hasn't then
+	 * this is a good indication some task is hogging the cpu
+	 */
+	duration = is_softlockup(touch_ts);
+	if (unlikely(duration)) {
+		/*
+		 * If a virtual machine is stopped by the host it can look to
+		 * the watchdog like a soft lockup, check to see if the host
+		 * stopped the vm before we issue the warning
+		 */
+		if (kvm_check_and_clear_guest_paused())
+			return HRTIMER_RESTART;
+
+		/* only warn once */
+		if (__this_cpu_read(soft_watchdog_warn) == true) {
+			/*
+			 * When multiple processes are causing softlockups the
+			 * softlockup detector only warns on the first one
+			 * because the code relies on a full quiet cycle to
+			 * re-arm.  The second process prevents the quiet cycle
+			 * and never gets reported.  Use task pointers to detect
+			 * this.
+			 */
+			if (__this_cpu_read(softlockup_task_ptr_saved) !=
+			    current) {
+				__this_cpu_write(soft_watchdog_warn, false);
+				__touch_watchdog();
+			}
+			return HRTIMER_RESTART;
+		}
+
+		if (softlockup_all_cpu_backtrace) {
+			/* Prevent multiple soft-lockup reports if one cpu is already
+			 * engaged in dumping cpu back traces
+			 */
+			if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
+				/* Someone else will report us. Let's give up */
+				__this_cpu_write(soft_watchdog_warn, true);
+				return HRTIMER_RESTART;
+			}
+		}
+
+		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
+			smp_processor_id(), duration,
+			current->comm, task_pid_nr(current));
+		__this_cpu_write(softlockup_task_ptr_saved, current);
+		print_modules();
+		print_irqtrace_events(current);
+		if (regs)
+			show_regs(regs);
+		else
+			dump_stack();
+
+		if (softlockup_all_cpu_backtrace) {
+			/* Avoid generating two back traces for current
+			 * given that one is already made above
+			 */
+			trigger_allbutself_cpu_backtrace();
+
+			clear_bit(0, &soft_lockup_nmi_warn);
+			/* Barrier to sync with other cpus */
+			smp_mb__after_atomic();
+		}
+
+		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
+		if (softlockup_panic)
+			panic("softlockup: hung tasks");
+		__this_cpu_write(soft_watchdog_warn, true);
+	} else
+		__this_cpu_write(soft_watchdog_warn, false);
+
+	return HRTIMER_RESTART;
+}
+
+static void watchdog_enable(unsigned int cpu)
+{
+	struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
+	struct completion *done = this_cpu_ptr(&softlockup_completion);
+
+	WARN_ON_ONCE(cpu != smp_processor_id());
+
+	init_completion(done);
+	complete(done);
+
+	/*
+	 * Start the timer first to prevent the NMI watchdog triggering
+	 * before the timer has a chance to fire.
+	 */
+	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer->function = watchdog_timer_fn;
+	hrtimer_start(hrtimer, ns_to_ktime(sample_period),
+		      HRTIMER_MODE_REL_PINNED);
+
+	/* Initialize timestamp */
+	__touch_watchdog();
+	/* Enable the perf event */
+	if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
+		watchdog_nmi_enable(cpu);
+}
+
+static void watchdog_disable(unsigned int cpu)
+{
+	struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
+
+	WARN_ON_ONCE(cpu != smp_processor_id());
+
+	/*
+	 * Disable the perf event first. That prevents that a large delay
+	 * between disabling the timer and disabling the perf event causes
+	 * the perf NMI to detect a false positive.
+	 */
+	watchdog_nmi_disable(cpu);
+	hrtimer_cancel(hrtimer);
+	wait_for_completion(this_cpu_ptr(&softlockup_completion));
+}
+
+static int softlockup_stop_fn(void *data)
+{
+	watchdog_disable(smp_processor_id());
+	return 0;
+}
+
+static void softlockup_stop_all(void)
+{
+	int cpu;
+
+	if (!softlockup_initialized)
+		return;
+
+	for_each_cpu(cpu, &watchdog_allowed_mask)
+		smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
+
+	cpumask_clear(&watchdog_allowed_mask);
+}
+
+static int softlockup_start_fn(void *data)
+{
+	watchdog_enable(smp_processor_id());
+	return 0;
+}
+
+static void softlockup_start_all(void)
+{
+	int cpu;
+
+	cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
+	for_each_cpu(cpu, &watchdog_allowed_mask)
+		smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
+}
+
+int lockup_detector_online_cpu(unsigned int cpu)
+{
+	if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
+		watchdog_enable(cpu);
+	return 0;
+}
+
+int lockup_detector_offline_cpu(unsigned int cpu)
+{
+	if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
+		watchdog_disable(cpu);
+	return 0;
+}
+
+static void lockup_detector_reconfigure(void)
+{
+	cpus_read_lock();
+	watchdog_nmi_stop();
+
+	softlockup_stop_all();
+	set_sample_period();
+	lockup_detector_update_enable();
+	if (watchdog_enabled && watchdog_thresh)
+		softlockup_start_all();
+
+	watchdog_nmi_start();
+	cpus_read_unlock();
+	/*
+	 * Must be called outside the cpus locked section to prevent
+	 * recursive locking in the perf code.
+	 */
+	__lockup_detector_cleanup();
+}
+
+/*
+ * Create the watchdog thread infrastructure and configure the detector(s).
+ *
+ * The threads are not unparked as watchdog_allowed_mask is empty.  When
+ * the threads are sucessfully initialized, take the proper locks and
+ * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
+ */
+static __init void lockup_detector_setup(void)
+{
+	/*
+	 * If sysctl is off and watchdog got disabled on the command line,
+	 * nothing to do here.
+	 */
+	lockup_detector_update_enable();
+
+	if (!IS_ENABLED(CONFIG_SYSCTL) &&
+	    !(watchdog_enabled && watchdog_thresh))
+		return;
+
+	mutex_lock(&watchdog_mutex);
+	lockup_detector_reconfigure();
+	softlockup_initialized = true;
+	mutex_unlock(&watchdog_mutex);
+}
+
+#else /* CONFIG_SOFTLOCKUP_DETECTOR */
+static void lockup_detector_reconfigure(void)
+{
+	cpus_read_lock();
+	watchdog_nmi_stop();
+	lockup_detector_update_enable();
+	watchdog_nmi_start();
+	cpus_read_unlock();
+}
+static inline void lockup_detector_setup(void)
+{
+	lockup_detector_reconfigure();
+}
+#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
+
+static void __lockup_detector_cleanup(void)
+{
+	lockdep_assert_held(&watchdog_mutex);
+	hardlockup_detector_perf_cleanup();
+}
+
+/**
+ * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
+ *
+ * Caller must not hold the cpu hotplug rwsem.
+ */
+void lockup_detector_cleanup(void)
+{
+	mutex_lock(&watchdog_mutex);
+	__lockup_detector_cleanup();
+	mutex_unlock(&watchdog_mutex);
+}
+
+/**
+ * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
+ *
+ * Special interface for parisc. It prevents lockup detector warnings from
+ * the default pm_poweroff() function which busy loops forever.
+ */
+void lockup_detector_soft_poweroff(void)
+{
+	watchdog_enabled = 0;
+}
+
+#ifdef CONFIG_SYSCTL
+
+/* Propagate any changes to the watchdog threads */
+static void proc_watchdog_update(void)
+{
+	/* Remove impossible cpus to keep sysctl output clean. */
+	cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
+	lockup_detector_reconfigure();
+}
+
+/*
+ * common function for watchdog, nmi_watchdog and soft_watchdog parameter
+ *
+ * caller             | table->data points to      | 'which'
+ * -------------------|----------------------------|--------------------------
+ * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
+ *                    |                            | SOFT_WATCHDOG_ENABLED
+ * -------------------|----------------------------|--------------------------
+ * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
+ * -------------------|----------------------------|--------------------------
+ * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
+ */
+static int proc_watchdog_common(int which, struct ctl_table *table, int write,
+				void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int err, old, *param = table->data;
+
+	mutex_lock(&watchdog_mutex);
+
+	if (!write) {
+		/*
+		 * On read synchronize the userspace interface. This is a
+		 * racy snapshot.
+		 */
+		*param = (watchdog_enabled & which) != 0;
+		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	} else {
+		old = READ_ONCE(*param);
+		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+		if (!err && old != READ_ONCE(*param))
+			proc_watchdog_update();
+	}
+	mutex_unlock(&watchdog_mutex);
+	return err;
+}
+
+/*
+ * /proc/sys/kernel/watchdog
+ */
+int proc_watchdog(struct ctl_table *table, int write,
+		  void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
+				    table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/nmi_watchdog
+ */
+int proc_nmi_watchdog(struct ctl_table *table, int write,
+		      void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	if (!nmi_watchdog_available && write)
+		return -ENOTSUPP;
+	return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
+				    table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/soft_watchdog
+ */
+int proc_soft_watchdog(struct ctl_table *table, int write,
+			void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
+				    table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/watchdog_thresh
+ */
+int proc_watchdog_thresh(struct ctl_table *table, int write,
+			 void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int err, old;
+
+	mutex_lock(&watchdog_mutex);
+
+	old = READ_ONCE(watchdog_thresh);
+	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+	if (!err && write && old != READ_ONCE(watchdog_thresh))
+		proc_watchdog_update();
+
+	mutex_unlock(&watchdog_mutex);
+	return err;
+}
+
+/*
+ * The cpumask is the mask of possible cpus that the watchdog can run
+ * on, not the mask of cpus it is actually running on.  This allows the
+ * user to specify a mask that will include cpus that have not yet
+ * been brought online, if desired.
+ */
+int proc_watchdog_cpumask(struct ctl_table *table, int write,
+			  void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int err;
+
+	mutex_lock(&watchdog_mutex);
+
+	err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
+	if (!err && write)
+		proc_watchdog_update();
+
+	mutex_unlock(&watchdog_mutex);
+	return err;
+}
+#endif /* CONFIG_SYSCTL */
+
+void __init lockup_detector_init(void)
+{
+	if (tick_nohz_full_enabled())
+		pr_info("Disabling watchdog on nohz_full cores by default\n");
+
+	cpumask_copy(&watchdog_cpumask,
+		     housekeeping_cpumask(HK_FLAG_TIMER));
+
+	if (!watchdog_nmi_probe())
+		nmi_watchdog_available = true;
+	lockup_detector_setup();
+}