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Diffstat (limited to 'kernel/time/timer.c')
| -rw-r--r-- | kernel/time/timer.c | 2136 |
1 files changed, 2136 insertions, 0 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c new file mode 100644 index 000000000..717fcb9fb --- /dev/null +++ b/kernel/time/timer.c @@ -0,0 +1,2136 @@ +// 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; + + BUG_ON(!timer->function); + + /* + * 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); + 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); + 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 del_timer_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 timeout in jiffies + * + * mod_timer_pending() is the same for pending timers as mod_timer(), + * but will not re-activate and modify already deleted timers. + * + * It is useful for unserialized use of timers. + */ +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 timeout in jiffies + * + * mod_timer() is a more efficient way to update the expire field of an + * active timer (if the timer is inactive it will be activated) + * + * mod_timer(timer, expires) is equivalent to: + * + * del_timer(timer); timer->expires = expires; add_timer(timer); + * + * 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. + * + * The function returns whether it has modified a pending timer or not. + * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an + * active timer returns 1.) + */ +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 timeout in jiffies + * + * timer_reduce() is very similar to mod_timer(), except that it will only + * modify a running timer if that would reduce the expiration time (it will + * start a timer that isn't running). + */ +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 added + * + * The kernel will do a ->function(@timer) callback from the + * timer interrupt at the ->expires point in the future. The + * current time is 'jiffies'. + * + * The timer's ->expires, ->function fields must be set prior calling this + * function. + * + * Timers with an ->expires field in the past will be executed in the next + * timer tick. + */ +void add_timer(struct timer_list *timer) +{ + BUG_ON(timer_pending(timer)); + __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 added + * @cpu: the CPU to start it on + * + * This is not very scalable on SMP. Double adds are not possible. + */ +void add_timer_on(struct timer_list *timer, int cpu) +{ + struct timer_base *new_base, *base; + unsigned long flags; + + BUG_ON(timer_pending(timer) || !timer->function); + + 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); + 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); + raw_spin_unlock_irqrestore(&base->lock, flags); +} +EXPORT_SYMBOL_GPL(add_timer_on); + +/** + * del_timer - deactivate a timer. + * @timer: the timer to be deactivated + * + * del_timer() deactivates a timer - this works on both active and inactive + * timers. + * + * The function returns whether it has deactivated a pending timer or not. + * (ie. del_timer() of an inactive timer returns 0, del_timer() of an + * active timer returns 1.) + */ +int del_timer(struct timer_list *timer) +{ + struct timer_base *base; + unsigned long flags; + int ret = 0; + + debug_assert_init(timer); + + if (timer_pending(timer)) { + base = lock_timer_base(timer, &flags); + ret = detach_if_pending(timer, base, true); + raw_spin_unlock_irqrestore(&base->lock, flags); + } + + return ret; +} +EXPORT_SYMBOL(del_timer); + +/** + * try_to_del_timer_sync - Try to deactivate a timer + * @timer: timer to delete + * + * This function tries to deactivate a timer. Upon successful (ret >= 0) + * exit the timer is not queued and the handler is not running on any CPU. + */ +int try_to_del_timer_sync(struct timer_list *timer) +{ + 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); + + raw_spin_unlock_irqrestore(&base->lock, flags); + + return ret; +} +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 + +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) +/** + * del_timer_sync - deactivate a timer and wait for the handler to finish. + * @timer: the timer to be deactivated + * + * This function only differs from del_timer() on SMP: besides deactivating + * the timer it also makes sure the handler has finished executing on other + * CPUs. + * + * 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 + * handler. 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. + * + * Note: For !irqsafe timers, you must not hold locks that are held in + * interrupt context while calling this function. 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); + * del_timer_sync(mytimer); + * while (base->running_timer == mytimer); + * + * Now del_timer_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. + * + * The function returns whether it has deactivated a pending timer or not. + */ +int del_timer_sync(struct timer_list *timer) +{ + 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_irq() && !(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); + + if (unlikely(ret < 0)) { + del_timer_wait_running(timer); + cpu_relax(); + } + } while (ret < 0); + + return ret; +} +EXPORT_SYMBOL(del_timer_sync); +#endif + +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 + * del_timer_sync() by acquiring the lock_map around the fn() + * call here and in del_timer_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 (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_singleshot_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; + + BUG_ON(cpu_online(cpu)); + + 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); + + BUG_ON(old_base->running_timer); + + 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); |