1 // SPDX-License-Identifier: GPL-2.0
3 * Kernel internal timers
5 * Copyright (C) 1991, 1992 Linus Torvalds
7 * 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
9 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
10 * "A Kernel Model for Precision Timekeeping" by Dave Mills
11 * 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
12 * serialize accesses to xtime/lost_ticks).
13 * Copyright (C) 1998 Andrea Arcangeli
14 * 1999-03-10 Improved NTP compatibility by Ulrich Windl
15 * 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
16 * 2000-10-05 Implemented scalable SMP per-CPU timer handling.
17 * Copyright (C) 2000, 2001, 2002 Ingo Molnar
18 * Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
21 #include <linux/kernel_stat.h>
22 #include <linux/export.h>
23 #include <linux/interrupt.h>
24 #include <linux/percpu.h>
25 #include <linux/init.h>
27 #include <linux/swap.h>
28 #include <linux/pid_namespace.h>
29 #include <linux/notifier.h>
30 #include <linux/thread_info.h>
31 #include <linux/time.h>
32 #include <linux/jiffies.h>
33 #include <linux/posix-timers.h>
34 #include <linux/cpu.h>
35 #include <linux/syscalls.h>
36 #include <linux/delay.h>
37 #include <linux/tick.h>
38 #include <linux/kallsyms.h>
39 #include <linux/irq_work.h>
40 #include <linux/sched/signal.h>
41 #include <linux/sched/sysctl.h>
42 #include <linux/sched/nohz.h>
43 #include <linux/sched/debug.h>
44 #include <linux/slab.h>
45 #include <linux/compat.h>
47 #include <linux/uaccess.h>
48 #include <asm/unistd.h>
49 #include <asm/div64.h>
50 #include <asm/timex.h>
53 #include "tick-internal.h"
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/timer.h>
58 __visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
60 EXPORT_SYMBOL(jiffies_64);
63 * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
64 * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
65 * level has a different granularity.
67 * The level granularity is: LVL_CLK_DIV ^ lvl
68 * The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
70 * The array level of a newly armed timer depends on the relative expiry
71 * time. The farther the expiry time is away the higher the array level and
72 * therefor the granularity becomes.
74 * Contrary to the original timer wheel implementation, which aims for 'exact'
75 * expiry of the timers, this implementation removes the need for recascading
76 * the timers into the lower array levels. The previous 'classic' timer wheel
77 * implementation of the kernel already violated the 'exact' expiry by adding
78 * slack to the expiry time to provide batched expiration. The granularity
79 * levels provide implicit batching.
81 * This is an optimization of the original timer wheel implementation for the
82 * majority of the timer wheel use cases: timeouts. The vast majority of
83 * timeout timers (networking, disk I/O ...) are canceled before expiry. If
84 * the timeout expires it indicates that normal operation is disturbed, so it
85 * does not matter much whether the timeout comes with a slight delay.
87 * The only exception to this are networking timers with a small expiry
88 * time. They rely on the granularity. Those fit into the first wheel level,
89 * which has HZ granularity.
91 * We don't have cascading anymore. timers with a expiry time above the
92 * capacity of the last wheel level are force expired at the maximum timeout
93 * value of the last wheel level. From data sampling we know that the maximum
94 * value observed is 5 days (network connection tracking), so this should not
97 * The currently chosen array constants values are a good compromise between
98 * array size and granularity.
100 * This results in the following granularity and range levels:
103 * Level Offset Granularity Range
104 * 0 0 1 ms 0 ms - 63 ms
105 * 1 64 8 ms 64 ms - 511 ms
106 * 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
107 * 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
108 * 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
109 * 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
110 * 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
111 * 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
112 * 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
115 * Level Offset Granularity Range
116 * 0 0 3 ms 0 ms - 210 ms
117 * 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
118 * 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
119 * 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
120 * 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
121 * 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
122 * 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
123 * 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
124 * 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
127 * Level Offset Granularity Range
128 * 0 0 4 ms 0 ms - 255 ms
129 * 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
130 * 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
131 * 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
132 * 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
133 * 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
134 * 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
135 * 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
136 * 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
139 * Level Offset Granularity Range
140 * 0 0 10 ms 0 ms - 630 ms
141 * 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
142 * 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
143 * 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
144 * 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
145 * 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
146 * 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
147 * 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
150 /* Clock divisor for the next level */
151 #define LVL_CLK_SHIFT 3
152 #define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
153 #define LVL_CLK_MASK (LVL_CLK_DIV - 1)
154 #define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
155 #define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
158 * The time start value for each level to select the bucket at enqueue
161 #define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
163 /* Size of each clock level */
165 #define LVL_SIZE (1UL << LVL_BITS)
166 #define LVL_MASK (LVL_SIZE - 1)
167 #define LVL_OFFS(n) ((n) * LVL_SIZE)
176 /* The cutoff (max. capacity of the wheel) */
177 #define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
178 #define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
181 * The resulting wheel size. If NOHZ is configured we allocate two
182 * wheels so we have a separate storage for the deferrable timers.
184 #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
186 #ifdef CONFIG_NO_HZ_COMMON
198 struct timer_list *running_timer;
200 unsigned long next_expiry;
203 bool must_forward_clk;
204 DECLARE_BITMAP(pending_map, WHEEL_SIZE);
205 struct hlist_head vectors[WHEEL_SIZE];
206 } ____cacheline_aligned;
208 static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
210 #ifdef CONFIG_NO_HZ_COMMON
212 static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
213 static DEFINE_MUTEX(timer_keys_mutex);
215 static void timer_update_keys(struct work_struct *work);
216 static DECLARE_WORK(timer_update_work, timer_update_keys);
219 unsigned int sysctl_timer_migration = 1;
221 DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
223 static void timers_update_migration(void)
225 if (sysctl_timer_migration && tick_nohz_active)
226 static_branch_enable(&timers_migration_enabled);
228 static_branch_disable(&timers_migration_enabled);
231 static inline void timers_update_migration(void) { }
232 #endif /* !CONFIG_SMP */
234 static void timer_update_keys(struct work_struct *work)
236 mutex_lock(&timer_keys_mutex);
237 timers_update_migration();
238 static_branch_enable(&timers_nohz_active);
239 mutex_unlock(&timer_keys_mutex);
242 void timers_update_nohz(void)
244 schedule_work(&timer_update_work);
247 int timer_migration_handler(struct ctl_table *table, int write,
248 void __user *buffer, size_t *lenp,
253 mutex_lock(&timer_keys_mutex);
254 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
256 timers_update_migration();
257 mutex_unlock(&timer_keys_mutex);
261 static inline bool is_timers_nohz_active(void)
263 return static_branch_unlikely(&timers_nohz_active);
266 static inline bool is_timers_nohz_active(void) { return false; }
267 #endif /* NO_HZ_COMMON */
269 static unsigned long round_jiffies_common(unsigned long j, int cpu,
273 unsigned long original = j;
276 * We don't want all cpus firing their timers at once hitting the
277 * same lock or cachelines, so we skew each extra cpu with an extra
278 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
280 * The skew is done by adding 3*cpunr, then round, then subtract this
281 * extra offset again.
288 * If the target jiffie is just after a whole second (which can happen
289 * due to delays of the timer irq, long irq off times etc etc) then
290 * we should round down to the whole second, not up. Use 1/4th second
291 * as cutoff for this rounding as an extreme upper bound for this.
292 * But never round down if @force_up is set.
294 if (rem < HZ/4 && !force_up) /* round down */
299 /* now that we have rounded, subtract the extra skew again */
303 * Make sure j is still in the future. Otherwise return the
306 return time_is_after_jiffies(j) ? j : original;
310 * __round_jiffies - function to round jiffies to a full second
311 * @j: the time in (absolute) jiffies that should be rounded
312 * @cpu: the processor number on which the timeout will happen
314 * __round_jiffies() rounds an absolute time in the future (in jiffies)
315 * up or down to (approximately) full seconds. This is useful for timers
316 * for which the exact time they fire does not matter too much, as long as
317 * they fire approximately every X seconds.
319 * By rounding these timers to whole seconds, all such timers will fire
320 * at the same time, rather than at various times spread out. The goal
321 * of this is to have the CPU wake up less, which saves power.
323 * The exact rounding is skewed for each processor to avoid all
324 * processors firing at the exact same time, which could lead
325 * to lock contention or spurious cache line bouncing.
327 * The return value is the rounded version of the @j parameter.
329 unsigned long __round_jiffies(unsigned long j, int cpu)
331 return round_jiffies_common(j, cpu, false);
333 EXPORT_SYMBOL_GPL(__round_jiffies);
336 * __round_jiffies_relative - function to round jiffies to a full second
337 * @j: the time in (relative) jiffies that should be rounded
338 * @cpu: the processor number on which the timeout will happen
340 * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
341 * up or down to (approximately) full seconds. This is useful for timers
342 * for which the exact time they fire does not matter too much, as long as
343 * they fire approximately every X seconds.
345 * By rounding these timers to whole seconds, all such timers will fire
346 * at the same time, rather than at various times spread out. The goal
347 * of this is to have the CPU wake up less, which saves power.
349 * The exact rounding is skewed for each processor to avoid all
350 * processors firing at the exact same time, which could lead
351 * to lock contention or spurious cache line bouncing.
353 * The return value is the rounded version of the @j parameter.
355 unsigned long __round_jiffies_relative(unsigned long j, int cpu)
357 unsigned long j0 = jiffies;
359 /* Use j0 because jiffies might change while we run */
360 return round_jiffies_common(j + j0, cpu, false) - j0;
362 EXPORT_SYMBOL_GPL(__round_jiffies_relative);
365 * round_jiffies - function to round jiffies to a full second
366 * @j: the time in (absolute) jiffies that should be rounded
368 * round_jiffies() rounds an absolute time in the future (in jiffies)
369 * up or down to (approximately) full seconds. This is useful for timers
370 * for which the exact time they fire does not matter too much, as long as
371 * they fire approximately every X seconds.
373 * By rounding these timers to whole seconds, all such timers will fire
374 * at the same time, rather than at various times spread out. The goal
375 * of this is to have the CPU wake up less, which saves power.
377 * The return value is the rounded version of the @j parameter.
379 unsigned long round_jiffies(unsigned long j)
381 return round_jiffies_common(j, raw_smp_processor_id(), false);
383 EXPORT_SYMBOL_GPL(round_jiffies);
386 * round_jiffies_relative - function to round jiffies to a full second
387 * @j: the time in (relative) jiffies that should be rounded
389 * round_jiffies_relative() rounds a time delta in the future (in jiffies)
390 * up or down to (approximately) full seconds. This is useful for timers
391 * for which the exact time they fire does not matter too much, as long as
392 * they fire approximately every X seconds.
394 * By rounding these timers to whole seconds, all such timers will fire
395 * at the same time, rather than at various times spread out. The goal
396 * of this is to have the CPU wake up less, which saves power.
398 * The return value is the rounded version of the @j parameter.
400 unsigned long round_jiffies_relative(unsigned long j)
402 return __round_jiffies_relative(j, raw_smp_processor_id());
404 EXPORT_SYMBOL_GPL(round_jiffies_relative);
407 * __round_jiffies_up - function to round jiffies up to a full second
408 * @j: the time in (absolute) jiffies that should be rounded
409 * @cpu: the processor number on which the timeout will happen
411 * This is the same as __round_jiffies() except that it will never
412 * round down. This is useful for timeouts for which the exact time
413 * of firing does not matter too much, as long as they don't fire too
416 unsigned long __round_jiffies_up(unsigned long j, int cpu)
418 return round_jiffies_common(j, cpu, true);
420 EXPORT_SYMBOL_GPL(__round_jiffies_up);
423 * __round_jiffies_up_relative - function to round jiffies up to a full second
424 * @j: the time in (relative) jiffies that should be rounded
425 * @cpu: the processor number on which the timeout will happen
427 * This is the same as __round_jiffies_relative() except that it will never
428 * round down. This is useful for timeouts for which the exact time
429 * of firing does not matter too much, as long as they don't fire too
432 unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
434 unsigned long j0 = jiffies;
436 /* Use j0 because jiffies might change while we run */
437 return round_jiffies_common(j + j0, cpu, true) - j0;
439 EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
442 * round_jiffies_up - function to round jiffies up to a full second
443 * @j: the time in (absolute) jiffies that should be rounded
445 * This is the same as round_jiffies() except that it will never
446 * round down. This is useful for timeouts for which the exact time
447 * of firing does not matter too much, as long as they don't fire too
450 unsigned long round_jiffies_up(unsigned long j)
452 return round_jiffies_common(j, raw_smp_processor_id(), true);
454 EXPORT_SYMBOL_GPL(round_jiffies_up);
457 * round_jiffies_up_relative - function to round jiffies up to a full second
458 * @j: the time in (relative) jiffies that should be rounded
460 * This is the same as round_jiffies_relative() except that it will never
461 * round down. This is useful for timeouts for which the exact time
462 * of firing does not matter too much, as long as they don't fire too
465 unsigned long round_jiffies_up_relative(unsigned long j)
467 return __round_jiffies_up_relative(j, raw_smp_processor_id());
469 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
472 static inline unsigned int timer_get_idx(struct timer_list *timer)
474 return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
477 static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
479 timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
480 idx << TIMER_ARRAYSHIFT;
484 * Helper function to calculate the array index for a given expiry
487 static inline unsigned calc_index(unsigned expires, unsigned lvl)
489 expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
490 return LVL_OFFS(lvl) + (expires & LVL_MASK);
493 static int calc_wheel_index(unsigned long expires, unsigned long clk)
495 unsigned long delta = expires - clk;
498 if (delta < LVL_START(1)) {
499 idx = calc_index(expires, 0);
500 } else if (delta < LVL_START(2)) {
501 idx = calc_index(expires, 1);
502 } else if (delta < LVL_START(3)) {
503 idx = calc_index(expires, 2);
504 } else if (delta < LVL_START(4)) {
505 idx = calc_index(expires, 3);
506 } else if (delta < LVL_START(5)) {
507 idx = calc_index(expires, 4);
508 } else if (delta < LVL_START(6)) {
509 idx = calc_index(expires, 5);
510 } else if (delta < LVL_START(7)) {
511 idx = calc_index(expires, 6);
512 } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
513 idx = calc_index(expires, 7);
514 } else if ((long) delta < 0) {
515 idx = clk & LVL_MASK;
518 * Force expire obscene large timeouts to expire at the
519 * capacity limit of the wheel.
521 if (expires >= WHEEL_TIMEOUT_CUTOFF)
522 expires = WHEEL_TIMEOUT_MAX;
524 idx = calc_index(expires, LVL_DEPTH - 1);
530 * Enqueue the timer into the hash bucket, mark it pending in
531 * the bitmap and store the index in the timer flags.
533 static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
536 hlist_add_head(&timer->entry, base->vectors + idx);
537 __set_bit(idx, base->pending_map);
538 timer_set_idx(timer, idx);
540 trace_timer_start(timer, timer->expires, timer->flags);
544 __internal_add_timer(struct timer_base *base, struct timer_list *timer)
548 idx = calc_wheel_index(timer->expires, base->clk);
549 enqueue_timer(base, timer, idx);
553 trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
555 if (!is_timers_nohz_active())
559 * TODO: This wants some optimizing similar to the code below, but we
560 * will do that when we switch from push to pull for deferrable timers.
562 if (timer->flags & TIMER_DEFERRABLE) {
563 if (tick_nohz_full_cpu(base->cpu))
564 wake_up_nohz_cpu(base->cpu);
569 * We might have to IPI the remote CPU if the base is idle and the
570 * timer is not deferrable. If the other CPU is on the way to idle
571 * then it can't set base->is_idle as we hold the base lock:
576 /* Check whether this is the new first expiring timer: */
577 if (time_after_eq(timer->expires, base->next_expiry))
581 * Set the next expiry time and kick the CPU so it can reevaluate the
584 base->next_expiry = timer->expires;
585 wake_up_nohz_cpu(base->cpu);
589 internal_add_timer(struct timer_base *base, struct timer_list *timer)
591 __internal_add_timer(base, timer);
592 trigger_dyntick_cpu(base, timer);
595 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
597 static struct debug_obj_descr timer_debug_descr;
599 static void *timer_debug_hint(void *addr)
601 return ((struct timer_list *) addr)->function;
604 static bool timer_is_static_object(void *addr)
606 struct timer_list *timer = addr;
608 return (timer->entry.pprev == NULL &&
609 timer->entry.next == TIMER_ENTRY_STATIC);
613 * fixup_init is called when:
614 * - an active object is initialized
616 static bool timer_fixup_init(void *addr, enum debug_obj_state state)
618 struct timer_list *timer = addr;
621 case ODEBUG_STATE_ACTIVE:
622 del_timer_sync(timer);
623 debug_object_init(timer, &timer_debug_descr);
630 /* Stub timer callback for improperly used timers. */
631 static void stub_timer(struct timer_list *unused)
637 * fixup_activate is called when:
638 * - an active object is activated
639 * - an unknown non-static object is activated
641 static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
643 struct timer_list *timer = addr;
646 case ODEBUG_STATE_NOTAVAILABLE:
647 timer_setup(timer, stub_timer, 0);
650 case ODEBUG_STATE_ACTIVE:
659 * fixup_free is called when:
660 * - an active object is freed
662 static bool timer_fixup_free(void *addr, enum debug_obj_state state)
664 struct timer_list *timer = addr;
667 case ODEBUG_STATE_ACTIVE:
668 del_timer_sync(timer);
669 debug_object_free(timer, &timer_debug_descr);
677 * fixup_assert_init is called when:
678 * - an untracked/uninit-ed object is found
680 static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
682 struct timer_list *timer = addr;
685 case ODEBUG_STATE_NOTAVAILABLE:
686 timer_setup(timer, stub_timer, 0);
693 static struct debug_obj_descr timer_debug_descr = {
694 .name = "timer_list",
695 .debug_hint = timer_debug_hint,
696 .is_static_object = timer_is_static_object,
697 .fixup_init = timer_fixup_init,
698 .fixup_activate = timer_fixup_activate,
699 .fixup_free = timer_fixup_free,
700 .fixup_assert_init = timer_fixup_assert_init,
703 static inline void debug_timer_init(struct timer_list *timer)
705 debug_object_init(timer, &timer_debug_descr);
708 static inline void debug_timer_activate(struct timer_list *timer)
710 debug_object_activate(timer, &timer_debug_descr);
713 static inline void debug_timer_deactivate(struct timer_list *timer)
715 debug_object_deactivate(timer, &timer_debug_descr);
718 static inline void debug_timer_free(struct timer_list *timer)
720 debug_object_free(timer, &timer_debug_descr);
723 static inline void debug_timer_assert_init(struct timer_list *timer)
725 debug_object_assert_init(timer, &timer_debug_descr);
728 static void do_init_timer(struct timer_list *timer,
729 void (*func)(struct timer_list *),
731 const char *name, struct lock_class_key *key);
733 void init_timer_on_stack_key(struct timer_list *timer,
734 void (*func)(struct timer_list *),
736 const char *name, struct lock_class_key *key)
738 debug_object_init_on_stack(timer, &timer_debug_descr);
739 do_init_timer(timer, func, flags, name, key);
741 EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
743 void destroy_timer_on_stack(struct timer_list *timer)
745 debug_object_free(timer, &timer_debug_descr);
747 EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
750 static inline void debug_timer_init(struct timer_list *timer) { }
751 static inline void debug_timer_activate(struct timer_list *timer) { }
752 static inline void debug_timer_deactivate(struct timer_list *timer) { }
753 static inline void debug_timer_assert_init(struct timer_list *timer) { }
756 static inline void debug_init(struct timer_list *timer)
758 debug_timer_init(timer);
759 trace_timer_init(timer);
762 static inline void debug_deactivate(struct timer_list *timer)
764 debug_timer_deactivate(timer);
765 trace_timer_cancel(timer);
768 static inline void debug_assert_init(struct timer_list *timer)
770 debug_timer_assert_init(timer);
773 static void do_init_timer(struct timer_list *timer,
774 void (*func)(struct timer_list *),
776 const char *name, struct lock_class_key *key)
778 timer->entry.pprev = NULL;
779 timer->function = func;
780 timer->flags = flags | raw_smp_processor_id();
781 lockdep_init_map(&timer->lockdep_map, name, key, 0);
785 * init_timer_key - initialize a timer
786 * @timer: the timer to be initialized
787 * @func: timer callback function
788 * @flags: timer flags
789 * @name: name of the timer
790 * @key: lockdep class key of the fake lock used for tracking timer
791 * sync lock dependencies
793 * init_timer_key() must be done to a timer prior calling *any* of the
794 * other timer functions.
796 void init_timer_key(struct timer_list *timer,
797 void (*func)(struct timer_list *), unsigned int flags,
798 const char *name, struct lock_class_key *key)
801 do_init_timer(timer, func, flags, name, key);
803 EXPORT_SYMBOL(init_timer_key);
805 static inline void detach_timer(struct timer_list *timer, bool clear_pending)
807 struct hlist_node *entry = &timer->entry;
809 debug_deactivate(timer);
814 entry->next = LIST_POISON2;
817 static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
820 unsigned idx = timer_get_idx(timer);
822 if (!timer_pending(timer))
825 if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
826 __clear_bit(idx, base->pending_map);
828 detach_timer(timer, clear_pending);
832 static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
834 struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
837 * If the timer is deferrable and NO_HZ_COMMON is set then we need
838 * to use the deferrable base.
840 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
841 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
845 static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
847 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
850 * If the timer is deferrable and NO_HZ_COMMON is set then we need
851 * to use the deferrable base.
853 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
854 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
858 static inline struct timer_base *get_timer_base(u32 tflags)
860 return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
863 static inline struct timer_base *
864 get_target_base(struct timer_base *base, unsigned tflags)
866 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
867 if (static_branch_likely(&timers_migration_enabled) &&
868 !(tflags & TIMER_PINNED))
869 return get_timer_cpu_base(tflags, get_nohz_timer_target());
871 return get_timer_this_cpu_base(tflags);
874 static inline void forward_timer_base(struct timer_base *base)
876 #ifdef CONFIG_NO_HZ_COMMON
880 * We only forward the base when we are idle or have just come out of
881 * idle (must_forward_clk logic), and have a delta between base clock
882 * and jiffies. In the common case, run_timers will take care of it.
884 if (likely(!base->must_forward_clk))
887 jnow = READ_ONCE(jiffies);
888 base->must_forward_clk = base->is_idle;
889 if ((long)(jnow - base->clk) < 2)
893 * If the next expiry value is > jiffies, then we fast forward to
894 * jiffies otherwise we forward to the next expiry value.
896 if (time_after(base->next_expiry, jnow))
899 base->clk = base->next_expiry;
905 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
906 * that all timers which are tied to this base are locked, and the base itself
909 * So __run_timers/migrate_timers can safely modify all timers which could
910 * be found in the base->vectors array.
912 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
913 * to wait until the migration is done.
915 static struct timer_base *lock_timer_base(struct timer_list *timer,
916 unsigned long *flags)
917 __acquires(timer->base->lock)
920 struct timer_base *base;
924 * We need to use READ_ONCE() here, otherwise the compiler
925 * might re-read @tf between the check for TIMER_MIGRATING
928 tf = READ_ONCE(timer->flags);
930 if (!(tf & TIMER_MIGRATING)) {
931 base = get_timer_base(tf);
932 raw_spin_lock_irqsave(&base->lock, *flags);
933 if (timer->flags == tf)
935 raw_spin_unlock_irqrestore(&base->lock, *flags);
941 #define MOD_TIMER_PENDING_ONLY 0x01
942 #define MOD_TIMER_REDUCE 0x02
945 __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
947 struct timer_base *base, *new_base;
948 unsigned int idx = UINT_MAX;
949 unsigned long clk = 0, flags;
952 BUG_ON(!timer->function);
955 * This is a common optimization triggered by the networking code - if
956 * the timer is re-modified to have the same timeout or ends up in the
957 * same array bucket then just return:
959 if (timer_pending(timer)) {
961 * The downside of this optimization is that it can result in
962 * larger granularity than you would get from adding a new
963 * timer with this expiry.
965 long diff = timer->expires - expires;
969 if (options & MOD_TIMER_REDUCE && diff <= 0)
973 * We lock timer base and calculate the bucket index right
974 * here. If the timer ends up in the same bucket, then we
975 * just update the expiry time and avoid the whole
976 * dequeue/enqueue dance.
978 base = lock_timer_base(timer, &flags);
979 forward_timer_base(base);
981 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
982 time_before_eq(timer->expires, expires)) {
988 idx = calc_wheel_index(expires, clk);
991 * Retrieve and compare the array index of the pending
992 * timer. If it matches set the expiry to the new value so a
993 * subsequent call will exit in the expires check above.
995 if (idx == timer_get_idx(timer)) {
996 if (!(options & MOD_TIMER_REDUCE))
997 timer->expires = expires;
998 else if (time_after(timer->expires, expires))
999 timer->expires = expires;
1004 base = lock_timer_base(timer, &flags);
1005 forward_timer_base(base);
1008 ret = detach_if_pending(timer, base, false);
1009 if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1012 new_base = get_target_base(base, timer->flags);
1014 if (base != new_base) {
1016 * We are trying to schedule the timer on the new base.
1017 * However we can't change timer's base while it is running,
1018 * otherwise del_timer_sync() can't detect that the timer's
1019 * handler yet has not finished. This also guarantees that the
1020 * timer is serialized wrt itself.
1022 if (likely(base->running_timer != timer)) {
1023 /* See the comment in lock_timer_base() */
1024 timer->flags |= TIMER_MIGRATING;
1026 raw_spin_unlock(&base->lock);
1028 raw_spin_lock(&base->lock);
1029 WRITE_ONCE(timer->flags,
1030 (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1031 forward_timer_base(base);
1035 debug_timer_activate(timer);
1037 timer->expires = expires;
1039 * If 'idx' was calculated above and the base time did not advance
1040 * between calculating 'idx' and possibly switching the base, only
1041 * enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
1042 * we need to (re)calculate the wheel index via
1043 * internal_add_timer().
1045 if (idx != UINT_MAX && clk == base->clk) {
1046 enqueue_timer(base, timer, idx);
1047 trigger_dyntick_cpu(base, timer);
1049 internal_add_timer(base, timer);
1053 raw_spin_unlock_irqrestore(&base->lock, flags);
1059 * mod_timer_pending - modify a pending timer's timeout
1060 * @timer: the pending timer to be modified
1061 * @expires: new timeout in jiffies
1063 * mod_timer_pending() is the same for pending timers as mod_timer(),
1064 * but will not re-activate and modify already deleted timers.
1066 * It is useful for unserialized use of timers.
1068 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1070 return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1072 EXPORT_SYMBOL(mod_timer_pending);
1075 * mod_timer - modify a timer's timeout
1076 * @timer: the timer to be modified
1077 * @expires: new timeout in jiffies
1079 * mod_timer() is a more efficient way to update the expire field of an
1080 * active timer (if the timer is inactive it will be activated)
1082 * mod_timer(timer, expires) is equivalent to:
1084 * del_timer(timer); timer->expires = expires; add_timer(timer);
1086 * Note that if there are multiple unserialized concurrent users of the
1087 * same timer, then mod_timer() is the only safe way to modify the timeout,
1088 * since add_timer() cannot modify an already running timer.
1090 * The function returns whether it has modified a pending timer or not.
1091 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1092 * active timer returns 1.)
1094 int mod_timer(struct timer_list *timer, unsigned long expires)
1096 return __mod_timer(timer, expires, 0);
1098 EXPORT_SYMBOL(mod_timer);
1101 * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1102 * @timer: The timer to be modified
1103 * @expires: New timeout in jiffies
1105 * timer_reduce() is very similar to mod_timer(), except that it will only
1106 * modify a running timer if that would reduce the expiration time (it will
1107 * start a timer that isn't running).
1109 int timer_reduce(struct timer_list *timer, unsigned long expires)
1111 return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1113 EXPORT_SYMBOL(timer_reduce);
1116 * add_timer - start a timer
1117 * @timer: the timer to be added
1119 * The kernel will do a ->function(@timer) callback from the
1120 * timer interrupt at the ->expires point in the future. The
1121 * current time is 'jiffies'.
1123 * The timer's ->expires, ->function fields must be set prior calling this
1126 * Timers with an ->expires field in the past will be executed in the next
1129 void add_timer(struct timer_list *timer)
1131 BUG_ON(timer_pending(timer));
1132 mod_timer(timer, timer->expires);
1134 EXPORT_SYMBOL(add_timer);
1137 * add_timer_on - start a timer on a particular CPU
1138 * @timer: the timer to be added
1139 * @cpu: the CPU to start it on
1141 * This is not very scalable on SMP. Double adds are not possible.
1143 void add_timer_on(struct timer_list *timer, int cpu)
1145 struct timer_base *new_base, *base;
1146 unsigned long flags;
1148 BUG_ON(timer_pending(timer) || !timer->function);
1150 new_base = get_timer_cpu_base(timer->flags, cpu);
1153 * If @timer was on a different CPU, it should be migrated with the
1154 * old base locked to prevent other operations proceeding with the
1155 * wrong base locked. See lock_timer_base().
1157 base = lock_timer_base(timer, &flags);
1158 if (base != new_base) {
1159 timer->flags |= TIMER_MIGRATING;
1161 raw_spin_unlock(&base->lock);
1163 raw_spin_lock(&base->lock);
1164 WRITE_ONCE(timer->flags,
1165 (timer->flags & ~TIMER_BASEMASK) | cpu);
1167 forward_timer_base(base);
1169 debug_timer_activate(timer);
1170 internal_add_timer(base, timer);
1171 raw_spin_unlock_irqrestore(&base->lock, flags);
1173 EXPORT_SYMBOL_GPL(add_timer_on);
1176 * del_timer - deactivate a timer.
1177 * @timer: the timer to be deactivated
1179 * del_timer() deactivates a timer - this works on both active and inactive
1182 * The function returns whether it has deactivated a pending timer or not.
1183 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1184 * active timer returns 1.)
1186 int del_timer(struct timer_list *timer)
1188 struct timer_base *base;
1189 unsigned long flags;
1192 debug_assert_init(timer);
1194 if (timer_pending(timer)) {
1195 base = lock_timer_base(timer, &flags);
1196 ret = detach_if_pending(timer, base, true);
1197 raw_spin_unlock_irqrestore(&base->lock, flags);
1202 EXPORT_SYMBOL(del_timer);
1205 * try_to_del_timer_sync - Try to deactivate a timer
1206 * @timer: timer to delete
1208 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1209 * exit the timer is not queued and the handler is not running on any CPU.
1211 int try_to_del_timer_sync(struct timer_list *timer)
1213 struct timer_base *base;
1214 unsigned long flags;
1217 debug_assert_init(timer);
1219 base = lock_timer_base(timer, &flags);
1221 if (base->running_timer != timer)
1222 ret = detach_if_pending(timer, base, true);
1224 raw_spin_unlock_irqrestore(&base->lock, flags);
1228 EXPORT_SYMBOL(try_to_del_timer_sync);
1232 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1233 * @timer: the timer to be deactivated
1235 * This function only differs from del_timer() on SMP: besides deactivating
1236 * the timer it also makes sure the handler has finished executing on other
1239 * Synchronization rules: Callers must prevent restarting of the timer,
1240 * otherwise this function is meaningless. It must not be called from
1241 * interrupt contexts unless the timer is an irqsafe one. The caller must
1242 * not hold locks which would prevent completion of the timer's
1243 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1244 * timer is not queued and the handler is not running on any CPU.
1246 * Note: For !irqsafe timers, you must not hold locks that are held in
1247 * interrupt context while calling this function. Even if the lock has
1248 * nothing to do with the timer in question. Here's why::
1254 * base->running_timer = mytimer;
1255 * spin_lock_irq(somelock);
1257 * spin_lock(somelock);
1258 * del_timer_sync(mytimer);
1259 * while (base->running_timer == mytimer);
1261 * Now del_timer_sync() will never return and never release somelock.
1262 * The interrupt on the other CPU is waiting to grab somelock but
1263 * it has interrupted the softirq that CPU0 is waiting to finish.
1265 * The function returns whether it has deactivated a pending timer or not.
1267 int del_timer_sync(struct timer_list *timer)
1269 #ifdef CONFIG_LOCKDEP
1270 unsigned long flags;
1273 * If lockdep gives a backtrace here, please reference
1274 * the synchronization rules above.
1276 local_irq_save(flags);
1277 lock_map_acquire(&timer->lockdep_map);
1278 lock_map_release(&timer->lockdep_map);
1279 local_irq_restore(flags);
1282 * don't use it in hardirq context, because it
1283 * could lead to deadlock.
1285 WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1287 int ret = try_to_del_timer_sync(timer);
1293 EXPORT_SYMBOL(del_timer_sync);
1296 static void call_timer_fn(struct timer_list *timer,
1297 void (*fn)(struct timer_list *),
1298 unsigned long baseclk)
1300 int count = preempt_count();
1302 #ifdef CONFIG_LOCKDEP
1304 * It is permissible to free the timer from inside the
1305 * function that is called from it, this we need to take into
1306 * account for lockdep too. To avoid bogus "held lock freed"
1307 * warnings as well as problems when looking into
1308 * timer->lockdep_map, make a copy and use that here.
1310 struct lockdep_map lockdep_map;
1312 lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1315 * Couple the lock chain with the lock chain at
1316 * del_timer_sync() by acquiring the lock_map around the fn()
1317 * call here and in del_timer_sync().
1319 lock_map_acquire(&lockdep_map);
1321 trace_timer_expire_entry(timer, baseclk);
1323 trace_timer_expire_exit(timer);
1325 lock_map_release(&lockdep_map);
1327 if (count != preempt_count()) {
1328 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1329 fn, count, preempt_count());
1331 * Restore the preempt count. That gives us a decent
1332 * chance to survive and extract information. If the
1333 * callback kept a lock held, bad luck, but not worse
1334 * than the BUG() we had.
1336 preempt_count_set(count);
1340 static void expire_timers(struct timer_base *base, struct hlist_head *head)
1343 * This value is required only for tracing. base->clk was
1344 * incremented directly before expire_timers was called. But expiry
1345 * is related to the old base->clk value.
1347 unsigned long baseclk = base->clk - 1;
1349 while (!hlist_empty(head)) {
1350 struct timer_list *timer;
1351 void (*fn)(struct timer_list *);
1353 timer = hlist_entry(head->first, struct timer_list, entry);
1355 base->running_timer = timer;
1356 detach_timer(timer, true);
1358 fn = timer->function;
1360 if (timer->flags & TIMER_IRQSAFE) {
1361 raw_spin_unlock(&base->lock);
1362 call_timer_fn(timer, fn, baseclk);
1363 raw_spin_lock(&base->lock);
1365 raw_spin_unlock_irq(&base->lock);
1366 call_timer_fn(timer, fn, baseclk);
1367 raw_spin_lock_irq(&base->lock);
1372 static int __collect_expired_timers(struct timer_base *base,
1373 struct hlist_head *heads)
1375 unsigned long clk = base->clk;
1376 struct hlist_head *vec;
1380 for (i = 0; i < LVL_DEPTH; i++) {
1381 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1383 if (__test_and_clear_bit(idx, base->pending_map)) {
1384 vec = base->vectors + idx;
1385 hlist_move_list(vec, heads++);
1388 /* Is it time to look at the next level? */
1389 if (clk & LVL_CLK_MASK)
1391 /* Shift clock for the next level granularity */
1392 clk >>= LVL_CLK_SHIFT;
1397 #ifdef CONFIG_NO_HZ_COMMON
1399 * Find the next pending bucket of a level. Search from level start (@offset)
1400 * + @clk upwards and if nothing there, search from start of the level
1401 * (@offset) up to @offset + clk.
1403 static int next_pending_bucket(struct timer_base *base, unsigned offset,
1406 unsigned pos, start = offset + clk;
1407 unsigned end = offset + LVL_SIZE;
1409 pos = find_next_bit(base->pending_map, end, start);
1413 pos = find_next_bit(base->pending_map, start, offset);
1414 return pos < start ? pos + LVL_SIZE - start : -1;
1418 * Search the first expiring timer in the various clock levels. Caller must
1421 static unsigned long __next_timer_interrupt(struct timer_base *base)
1423 unsigned long clk, next, adj;
1424 unsigned lvl, offset = 0;
1426 next = base->clk + NEXT_TIMER_MAX_DELTA;
1428 for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1429 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1432 unsigned long tmp = clk + (unsigned long) pos;
1434 tmp <<= LVL_SHIFT(lvl);
1435 if (time_before(tmp, next))
1439 * Clock for the next level. If the current level clock lower
1440 * bits are zero, we look at the next level as is. If not we
1441 * need to advance it by one because that's going to be the
1442 * next expiring bucket in that level. base->clk is the next
1443 * expiring jiffie. So in case of:
1445 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1448 * we have to look at all levels @index 0. With
1450 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1453 * LVL0 has the next expiring bucket @index 2. The upper
1454 * levels have the next expiring bucket @index 1.
1456 * In case that the propagation wraps the next level the same
1459 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1462 * So after looking at LVL0 we get:
1464 * LVL5 LVL4 LVL3 LVL2 LVL1
1467 * So no propagation from LVL1 to LVL2 because that happened
1468 * with the add already, but then we need to propagate further
1469 * from LVL2 to LVL3.
1471 * So the simple check whether the lower bits of the current
1472 * level are 0 or not is sufficient for all cases.
1474 adj = clk & LVL_CLK_MASK ? 1 : 0;
1475 clk >>= LVL_CLK_SHIFT;
1482 * Check, if the next hrtimer event is before the next timer wheel
1485 static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1487 u64 nextevt = hrtimer_get_next_event();
1490 * If high resolution timers are enabled
1491 * hrtimer_get_next_event() returns KTIME_MAX.
1493 if (expires <= nextevt)
1497 * If the next timer is already expired, return the tick base
1498 * time so the tick is fired immediately.
1500 if (nextevt <= basem)
1504 * Round up to the next jiffie. High resolution timers are
1505 * off, so the hrtimers are expired in the tick and we need to
1506 * make sure that this tick really expires the timer to avoid
1507 * a ping pong of the nohz stop code.
1509 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1511 return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1515 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1516 * @basej: base time jiffies
1517 * @basem: base time clock monotonic
1519 * Returns the tick aligned clock monotonic time of the next pending
1520 * timer or KTIME_MAX if no timer is pending.
1522 u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1524 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1525 u64 expires = KTIME_MAX;
1526 unsigned long nextevt;
1530 * Pretend that there is no timer pending if the cpu is offline.
1531 * Possible pending timers will be migrated later to an active cpu.
1533 if (cpu_is_offline(smp_processor_id()))
1536 raw_spin_lock(&base->lock);
1537 nextevt = __next_timer_interrupt(base);
1538 is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
1539 base->next_expiry = nextevt;
1541 * We have a fresh next event. Check whether we can forward the
1542 * base. We can only do that when @basej is past base->clk
1543 * otherwise we might rewind base->clk.
1545 if (time_after(basej, base->clk)) {
1546 if (time_after(nextevt, basej))
1548 else if (time_after(nextevt, base->clk))
1549 base->clk = nextevt;
1552 if (time_before_eq(nextevt, basej)) {
1554 base->is_idle = false;
1557 expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1559 * If we expect to sleep more than a tick, mark the base idle.
1560 * Also the tick is stopped so any added timer must forward
1561 * the base clk itself to keep granularity small. This idle
1562 * logic is only maintained for the BASE_STD base, deferrable
1563 * timers may still see large granularity skew (by design).
1565 if ((expires - basem) > TICK_NSEC) {
1566 base->must_forward_clk = true;
1567 base->is_idle = true;
1570 raw_spin_unlock(&base->lock);
1572 return cmp_next_hrtimer_event(basem, expires);
1576 * timer_clear_idle - Clear the idle state of the timer base
1578 * Called with interrupts disabled
1580 void timer_clear_idle(void)
1582 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1585 * We do this unlocked. The worst outcome is a remote enqueue sending
1586 * a pointless IPI, but taking the lock would just make the window for
1587 * sending the IPI a few instructions smaller for the cost of taking
1588 * the lock in the exit from idle path.
1590 base->is_idle = false;
1593 static int collect_expired_timers(struct timer_base *base,
1594 struct hlist_head *heads)
1597 * NOHZ optimization. After a long idle sleep we need to forward the
1598 * base to current jiffies. Avoid a loop by searching the bitfield for
1599 * the next expiring timer.
1601 if ((long)(jiffies - base->clk) > 2) {
1602 unsigned long next = __next_timer_interrupt(base);
1605 * If the next timer is ahead of time forward to current
1606 * jiffies, otherwise forward to the next expiry time:
1608 if (time_after(next, jiffies)) {
1610 * The call site will increment base->clk and then
1611 * terminate the expiry loop immediately.
1613 base->clk = jiffies;
1618 return __collect_expired_timers(base, heads);
1621 static inline int collect_expired_timers(struct timer_base *base,
1622 struct hlist_head *heads)
1624 return __collect_expired_timers(base, heads);
1629 * Called from the timer interrupt handler to charge one tick to the current
1630 * process. user_tick is 1 if the tick is user time, 0 for system.
1632 void update_process_times(int user_tick)
1634 struct task_struct *p = current;
1636 /* Note: this timer irq context must be accounted for as well. */
1637 account_process_tick(p, user_tick);
1639 rcu_sched_clock_irq(user_tick);
1640 #ifdef CONFIG_IRQ_WORK
1645 if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1646 run_posix_cpu_timers(p);
1650 * __run_timers - run all expired timers (if any) on this CPU.
1651 * @base: the timer vector to be processed.
1653 static inline void __run_timers(struct timer_base *base)
1655 struct hlist_head heads[LVL_DEPTH];
1658 if (!time_after_eq(jiffies, base->clk))
1661 raw_spin_lock_irq(&base->lock);
1664 * timer_base::must_forward_clk must be cleared before running
1665 * timers so that any timer functions that call mod_timer() will
1666 * not try to forward the base. Idle tracking / clock forwarding
1667 * logic is only used with BASE_STD timers.
1669 * The must_forward_clk flag is cleared unconditionally also for
1670 * the deferrable base. The deferrable base is not affected by idle
1671 * tracking and never forwarded, so clearing the flag is a NOOP.
1673 * The fact that the deferrable base is never forwarded can cause
1674 * large variations in granularity for deferrable timers, but they
1675 * can be deferred for long periods due to idle anyway.
1677 base->must_forward_clk = false;
1679 while (time_after_eq(jiffies, base->clk)) {
1681 levels = collect_expired_timers(base, heads);
1685 expire_timers(base, heads + levels);
1687 base->running_timer = NULL;
1688 raw_spin_unlock_irq(&base->lock);
1692 * This function runs timers and the timer-tq in bottom half context.
1694 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1696 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1699 if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1700 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1704 * Called by the local, per-CPU timer interrupt on SMP.
1706 void run_local_timers(void)
1708 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1710 hrtimer_run_queues();
1711 /* Raise the softirq only if required. */
1712 if (time_before(jiffies, base->clk)) {
1713 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1715 /* CPU is awake, so check the deferrable base. */
1717 if (time_before(jiffies, base->clk))
1720 raise_softirq(TIMER_SOFTIRQ);
1724 * Since schedule_timeout()'s timer is defined on the stack, it must store
1725 * the target task on the stack as well.
1727 struct process_timer {
1728 struct timer_list timer;
1729 struct task_struct *task;
1732 static void process_timeout(struct timer_list *t)
1734 struct process_timer *timeout = from_timer(timeout, t, timer);
1736 wake_up_process(timeout->task);
1740 * schedule_timeout - sleep until timeout
1741 * @timeout: timeout value in jiffies
1743 * Make the current task sleep until @timeout jiffies have
1744 * elapsed. The routine will return immediately unless
1745 * the current task state has been set (see set_current_state()).
1747 * You can set the task state as follows -
1749 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1750 * pass before the routine returns unless the current task is explicitly
1751 * woken up, (e.g. by wake_up_process())".
1753 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1754 * delivered to the current task or the current task is explicitly woken
1757 * The current task state is guaranteed to be TASK_RUNNING when this
1760 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1761 * the CPU away without a bound on the timeout. In this case the return
1762 * value will be %MAX_SCHEDULE_TIMEOUT.
1764 * Returns 0 when the timer has expired otherwise the remaining time in
1765 * jiffies will be returned. In all cases the return value is guaranteed
1766 * to be non-negative.
1768 signed long __sched schedule_timeout(signed long timeout)
1770 struct process_timer timer;
1771 unsigned long expire;
1775 case MAX_SCHEDULE_TIMEOUT:
1777 * These two special cases are useful to be comfortable
1778 * in the caller. Nothing more. We could take
1779 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1780 * but I' d like to return a valid offset (>=0) to allow
1781 * the caller to do everything it want with the retval.
1787 * Another bit of PARANOID. Note that the retval will be
1788 * 0 since no piece of kernel is supposed to do a check
1789 * for a negative retval of schedule_timeout() (since it
1790 * should never happens anyway). You just have the printk()
1791 * that will tell you if something is gone wrong and where.
1794 printk(KERN_ERR "schedule_timeout: wrong timeout "
1795 "value %lx\n", timeout);
1797 current->state = TASK_RUNNING;
1802 expire = timeout + jiffies;
1804 timer.task = current;
1805 timer_setup_on_stack(&timer.timer, process_timeout, 0);
1806 __mod_timer(&timer.timer, expire, 0);
1808 del_singleshot_timer_sync(&timer.timer);
1810 /* Remove the timer from the object tracker */
1811 destroy_timer_on_stack(&timer.timer);
1813 timeout = expire - jiffies;
1816 return timeout < 0 ? 0 : timeout;
1818 EXPORT_SYMBOL(schedule_timeout);
1821 * We can use __set_current_state() here because schedule_timeout() calls
1822 * schedule() unconditionally.
1824 signed long __sched schedule_timeout_interruptible(signed long timeout)
1826 __set_current_state(TASK_INTERRUPTIBLE);
1827 return schedule_timeout(timeout);
1829 EXPORT_SYMBOL(schedule_timeout_interruptible);
1831 signed long __sched schedule_timeout_killable(signed long timeout)
1833 __set_current_state(TASK_KILLABLE);
1834 return schedule_timeout(timeout);
1836 EXPORT_SYMBOL(schedule_timeout_killable);
1838 signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1840 __set_current_state(TASK_UNINTERRUPTIBLE);
1841 return schedule_timeout(timeout);
1843 EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1846 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1849 signed long __sched schedule_timeout_idle(signed long timeout)
1851 __set_current_state(TASK_IDLE);
1852 return schedule_timeout(timeout);
1854 EXPORT_SYMBOL(schedule_timeout_idle);
1856 #ifdef CONFIG_HOTPLUG_CPU
1857 static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1859 struct timer_list *timer;
1860 int cpu = new_base->cpu;
1862 while (!hlist_empty(head)) {
1863 timer = hlist_entry(head->first, struct timer_list, entry);
1864 detach_timer(timer, false);
1865 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1866 internal_add_timer(new_base, timer);
1870 int timers_prepare_cpu(unsigned int cpu)
1872 struct timer_base *base;
1875 for (b = 0; b < NR_BASES; b++) {
1876 base = per_cpu_ptr(&timer_bases[b], cpu);
1877 base->clk = jiffies;
1878 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
1879 base->is_idle = false;
1880 base->must_forward_clk = true;
1885 int timers_dead_cpu(unsigned int cpu)
1887 struct timer_base *old_base;
1888 struct timer_base *new_base;
1891 BUG_ON(cpu_online(cpu));
1893 for (b = 0; b < NR_BASES; b++) {
1894 old_base = per_cpu_ptr(&timer_bases[b], cpu);
1895 new_base = get_cpu_ptr(&timer_bases[b]);
1897 * The caller is globally serialized and nobody else
1898 * takes two locks at once, deadlock is not possible.
1900 raw_spin_lock_irq(&new_base->lock);
1901 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1904 * The current CPUs base clock might be stale. Update it
1905 * before moving the timers over.
1907 forward_timer_base(new_base);
1909 BUG_ON(old_base->running_timer);
1911 for (i = 0; i < WHEEL_SIZE; i++)
1912 migrate_timer_list(new_base, old_base->vectors + i);
1914 raw_spin_unlock(&old_base->lock);
1915 raw_spin_unlock_irq(&new_base->lock);
1916 put_cpu_ptr(&timer_bases);
1921 #endif /* CONFIG_HOTPLUG_CPU */
1923 static void __init init_timer_cpu(int cpu)
1925 struct timer_base *base;
1928 for (i = 0; i < NR_BASES; i++) {
1929 base = per_cpu_ptr(&timer_bases[i], cpu);
1931 raw_spin_lock_init(&base->lock);
1932 base->clk = jiffies;
1936 static void __init init_timer_cpus(void)
1940 for_each_possible_cpu(cpu)
1941 init_timer_cpu(cpu);
1944 void __init init_timers(void)
1947 open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
1951 * msleep - sleep safely even with waitqueue interruptions
1952 * @msecs: Time in milliseconds to sleep for
1954 void msleep(unsigned int msecs)
1956 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1959 timeout = schedule_timeout_uninterruptible(timeout);
1962 EXPORT_SYMBOL(msleep);
1965 * msleep_interruptible - sleep waiting for signals
1966 * @msecs: Time in milliseconds to sleep for
1968 unsigned long msleep_interruptible(unsigned int msecs)
1970 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1972 while (timeout && !signal_pending(current))
1973 timeout = schedule_timeout_interruptible(timeout);
1974 return jiffies_to_msecs(timeout);
1977 EXPORT_SYMBOL(msleep_interruptible);
1980 * usleep_range - Sleep for an approximate time
1981 * @min: Minimum time in usecs to sleep
1982 * @max: Maximum time in usecs to sleep
1984 * In non-atomic context where the exact wakeup time is flexible, use
1985 * usleep_range() instead of udelay(). The sleep improves responsiveness
1986 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
1987 * power usage by allowing hrtimers to take advantage of an already-
1988 * scheduled interrupt instead of scheduling a new one just for this sleep.
1990 void __sched usleep_range(unsigned long min, unsigned long max)
1992 ktime_t exp = ktime_add_us(ktime_get(), min);
1993 u64 delta = (u64)(max - min) * NSEC_PER_USEC;
1996 __set_current_state(TASK_UNINTERRUPTIBLE);
1997 /* Do not return before the requested sleep time has elapsed */
1998 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2002 EXPORT_SYMBOL(usleep_range);