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
);
542 __internal_add_timer(struct timer_base
*base
, struct timer_list
*timer
)
546 idx
= calc_wheel_index(timer
->expires
, base
->clk
);
547 enqueue_timer(base
, timer
, idx
);
551 trigger_dyntick_cpu(struct timer_base
*base
, struct timer_list
*timer
)
553 if (!is_timers_nohz_active())
557 * TODO: This wants some optimizing similar to the code below, but we
558 * will do that when we switch from push to pull for deferrable timers.
560 if (timer
->flags
& TIMER_DEFERRABLE
) {
561 if (tick_nohz_full_cpu(base
->cpu
))
562 wake_up_nohz_cpu(base
->cpu
);
567 * We might have to IPI the remote CPU if the base is idle and the
568 * timer is not deferrable. If the other CPU is on the way to idle
569 * then it can't set base->is_idle as we hold the base lock:
574 /* Check whether this is the new first expiring timer: */
575 if (time_after_eq(timer
->expires
, base
->next_expiry
))
579 * Set the next expiry time and kick the CPU so it can reevaluate the
582 base
->next_expiry
= timer
->expires
;
583 wake_up_nohz_cpu(base
->cpu
);
587 internal_add_timer(struct timer_base
*base
, struct timer_list
*timer
)
589 __internal_add_timer(base
, timer
);
590 trigger_dyntick_cpu(base
, timer
);
593 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
595 static struct debug_obj_descr timer_debug_descr
;
597 static void *timer_debug_hint(void *addr
)
599 return ((struct timer_list
*) addr
)->function
;
602 static bool timer_is_static_object(void *addr
)
604 struct timer_list
*timer
= addr
;
606 return (timer
->entry
.pprev
== NULL
&&
607 timer
->entry
.next
== TIMER_ENTRY_STATIC
);
611 * fixup_init is called when:
612 * - an active object is initialized
614 static bool timer_fixup_init(void *addr
, enum debug_obj_state state
)
616 struct timer_list
*timer
= addr
;
619 case ODEBUG_STATE_ACTIVE
:
620 del_timer_sync(timer
);
621 debug_object_init(timer
, &timer_debug_descr
);
628 /* Stub timer callback for improperly used timers. */
629 static void stub_timer(struct timer_list
*unused
)
635 * fixup_activate is called when:
636 * - an active object is activated
637 * - an unknown non-static object is activated
639 static bool timer_fixup_activate(void *addr
, enum debug_obj_state state
)
641 struct timer_list
*timer
= addr
;
644 case ODEBUG_STATE_NOTAVAILABLE
:
645 timer_setup(timer
, stub_timer
, 0);
648 case ODEBUG_STATE_ACTIVE
:
657 * fixup_free is called when:
658 * - an active object is freed
660 static bool timer_fixup_free(void *addr
, enum debug_obj_state state
)
662 struct timer_list
*timer
= addr
;
665 case ODEBUG_STATE_ACTIVE
:
666 del_timer_sync(timer
);
667 debug_object_free(timer
, &timer_debug_descr
);
675 * fixup_assert_init is called when:
676 * - an untracked/uninit-ed object is found
678 static bool timer_fixup_assert_init(void *addr
, enum debug_obj_state state
)
680 struct timer_list
*timer
= addr
;
683 case ODEBUG_STATE_NOTAVAILABLE
:
684 timer_setup(timer
, stub_timer
, 0);
691 static struct debug_obj_descr timer_debug_descr
= {
692 .name
= "timer_list",
693 .debug_hint
= timer_debug_hint
,
694 .is_static_object
= timer_is_static_object
,
695 .fixup_init
= timer_fixup_init
,
696 .fixup_activate
= timer_fixup_activate
,
697 .fixup_free
= timer_fixup_free
,
698 .fixup_assert_init
= timer_fixup_assert_init
,
701 static inline void debug_timer_init(struct timer_list
*timer
)
703 debug_object_init(timer
, &timer_debug_descr
);
706 static inline void debug_timer_activate(struct timer_list
*timer
)
708 debug_object_activate(timer
, &timer_debug_descr
);
711 static inline void debug_timer_deactivate(struct timer_list
*timer
)
713 debug_object_deactivate(timer
, &timer_debug_descr
);
716 static inline void debug_timer_free(struct timer_list
*timer
)
718 debug_object_free(timer
, &timer_debug_descr
);
721 static inline void debug_timer_assert_init(struct timer_list
*timer
)
723 debug_object_assert_init(timer
, &timer_debug_descr
);
726 static void do_init_timer(struct timer_list
*timer
,
727 void (*func
)(struct timer_list
*),
729 const char *name
, struct lock_class_key
*key
);
731 void init_timer_on_stack_key(struct timer_list
*timer
,
732 void (*func
)(struct timer_list
*),
734 const char *name
, struct lock_class_key
*key
)
736 debug_object_init_on_stack(timer
, &timer_debug_descr
);
737 do_init_timer(timer
, func
, flags
, name
, key
);
739 EXPORT_SYMBOL_GPL(init_timer_on_stack_key
);
741 void destroy_timer_on_stack(struct timer_list
*timer
)
743 debug_object_free(timer
, &timer_debug_descr
);
745 EXPORT_SYMBOL_GPL(destroy_timer_on_stack
);
748 static inline void debug_timer_init(struct timer_list
*timer
) { }
749 static inline void debug_timer_activate(struct timer_list
*timer
) { }
750 static inline void debug_timer_deactivate(struct timer_list
*timer
) { }
751 static inline void debug_timer_assert_init(struct timer_list
*timer
) { }
754 static inline void debug_init(struct timer_list
*timer
)
756 debug_timer_init(timer
);
757 trace_timer_init(timer
);
761 debug_activate(struct timer_list
*timer
, unsigned long expires
)
763 debug_timer_activate(timer
);
764 trace_timer_start(timer
, expires
, timer
->flags
);
767 static inline void debug_deactivate(struct timer_list
*timer
)
769 debug_timer_deactivate(timer
);
770 trace_timer_cancel(timer
);
773 static inline void debug_assert_init(struct timer_list
*timer
)
775 debug_timer_assert_init(timer
);
778 static void do_init_timer(struct timer_list
*timer
,
779 void (*func
)(struct timer_list
*),
781 const char *name
, struct lock_class_key
*key
)
783 timer
->entry
.pprev
= NULL
;
784 timer
->function
= func
;
785 timer
->flags
= flags
| raw_smp_processor_id();
786 lockdep_init_map(&timer
->lockdep_map
, name
, key
, 0);
790 * init_timer_key - initialize a timer
791 * @timer: the timer to be initialized
792 * @func: timer callback function
793 * @flags: timer flags
794 * @name: name of the timer
795 * @key: lockdep class key of the fake lock used for tracking timer
796 * sync lock dependencies
798 * init_timer_key() must be done to a timer prior calling *any* of the
799 * other timer functions.
801 void init_timer_key(struct timer_list
*timer
,
802 void (*func
)(struct timer_list
*), unsigned int flags
,
803 const char *name
, struct lock_class_key
*key
)
806 do_init_timer(timer
, func
, flags
, name
, key
);
808 EXPORT_SYMBOL(init_timer_key
);
810 static inline void detach_timer(struct timer_list
*timer
, bool clear_pending
)
812 struct hlist_node
*entry
= &timer
->entry
;
814 debug_deactivate(timer
);
819 entry
->next
= LIST_POISON2
;
822 static int detach_if_pending(struct timer_list
*timer
, struct timer_base
*base
,
825 unsigned idx
= timer_get_idx(timer
);
827 if (!timer_pending(timer
))
830 if (hlist_is_singular_node(&timer
->entry
, base
->vectors
+ idx
))
831 __clear_bit(idx
, base
->pending_map
);
833 detach_timer(timer
, clear_pending
);
837 static inline struct timer_base
*get_timer_cpu_base(u32 tflags
, u32 cpu
)
839 struct timer_base
*base
= per_cpu_ptr(&timer_bases
[BASE_STD
], cpu
);
842 * If the timer is deferrable and NO_HZ_COMMON is set then we need
843 * to use the deferrable base.
845 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
) && (tflags
& TIMER_DEFERRABLE
))
846 base
= per_cpu_ptr(&timer_bases
[BASE_DEF
], cpu
);
850 static inline struct timer_base
*get_timer_this_cpu_base(u32 tflags
)
852 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
855 * If the timer is deferrable and NO_HZ_COMMON is set then we need
856 * to use the deferrable base.
858 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
) && (tflags
& TIMER_DEFERRABLE
))
859 base
= this_cpu_ptr(&timer_bases
[BASE_DEF
]);
863 static inline struct timer_base
*get_timer_base(u32 tflags
)
865 return get_timer_cpu_base(tflags
, tflags
& TIMER_CPUMASK
);
868 static inline struct timer_base
*
869 get_target_base(struct timer_base
*base
, unsigned tflags
)
871 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
872 if (static_branch_likely(&timers_migration_enabled
) &&
873 !(tflags
& TIMER_PINNED
))
874 return get_timer_cpu_base(tflags
, get_nohz_timer_target());
876 return get_timer_this_cpu_base(tflags
);
879 static inline void forward_timer_base(struct timer_base
*base
)
881 #ifdef CONFIG_NO_HZ_COMMON
885 * We only forward the base when we are idle or have just come out of
886 * idle (must_forward_clk logic), and have a delta between base clock
887 * and jiffies. In the common case, run_timers will take care of it.
889 if (likely(!base
->must_forward_clk
))
892 jnow
= READ_ONCE(jiffies
);
893 base
->must_forward_clk
= base
->is_idle
;
894 if ((long)(jnow
- base
->clk
) < 2)
898 * If the next expiry value is > jiffies, then we fast forward to
899 * jiffies otherwise we forward to the next expiry value.
901 if (time_after(base
->next_expiry
, jnow
))
904 base
->clk
= base
->next_expiry
;
910 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
911 * that all timers which are tied to this base are locked, and the base itself
914 * So __run_timers/migrate_timers can safely modify all timers which could
915 * be found in the base->vectors array.
917 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
918 * to wait until the migration is done.
920 static struct timer_base
*lock_timer_base(struct timer_list
*timer
,
921 unsigned long *flags
)
922 __acquires(timer
->base
->lock
)
925 struct timer_base
*base
;
929 * We need to use READ_ONCE() here, otherwise the compiler
930 * might re-read @tf between the check for TIMER_MIGRATING
933 tf
= READ_ONCE(timer
->flags
);
935 if (!(tf
& TIMER_MIGRATING
)) {
936 base
= get_timer_base(tf
);
937 raw_spin_lock_irqsave(&base
->lock
, *flags
);
938 if (timer
->flags
== tf
)
940 raw_spin_unlock_irqrestore(&base
->lock
, *flags
);
946 #define MOD_TIMER_PENDING_ONLY 0x01
947 #define MOD_TIMER_REDUCE 0x02
950 __mod_timer(struct timer_list
*timer
, unsigned long expires
, unsigned int options
)
952 struct timer_base
*base
, *new_base
;
953 unsigned int idx
= UINT_MAX
;
954 unsigned long clk
= 0, flags
;
957 BUG_ON(!timer
->function
);
960 * This is a common optimization triggered by the networking code - if
961 * the timer is re-modified to have the same timeout or ends up in the
962 * same array bucket then just return:
964 if (timer_pending(timer
)) {
966 * The downside of this optimization is that it can result in
967 * larger granularity than you would get from adding a new
968 * timer with this expiry.
970 long diff
= timer
->expires
- expires
;
974 if (options
& MOD_TIMER_REDUCE
&& diff
<= 0)
978 * We lock timer base and calculate the bucket index right
979 * here. If the timer ends up in the same bucket, then we
980 * just update the expiry time and avoid the whole
981 * dequeue/enqueue dance.
983 base
= lock_timer_base(timer
, &flags
);
984 forward_timer_base(base
);
986 if (timer_pending(timer
) && (options
& MOD_TIMER_REDUCE
) &&
987 time_before_eq(timer
->expires
, expires
)) {
993 idx
= calc_wheel_index(expires
, clk
);
996 * Retrieve and compare the array index of the pending
997 * timer. If it matches set the expiry to the new value so a
998 * subsequent call will exit in the expires check above.
1000 if (idx
== timer_get_idx(timer
)) {
1001 if (!(options
& MOD_TIMER_REDUCE
))
1002 timer
->expires
= expires
;
1003 else if (time_after(timer
->expires
, expires
))
1004 timer
->expires
= expires
;
1009 base
= lock_timer_base(timer
, &flags
);
1010 forward_timer_base(base
);
1013 ret
= detach_if_pending(timer
, base
, false);
1014 if (!ret
&& (options
& MOD_TIMER_PENDING_ONLY
))
1017 new_base
= get_target_base(base
, timer
->flags
);
1019 if (base
!= new_base
) {
1021 * We are trying to schedule the timer on the new base.
1022 * However we can't change timer's base while it is running,
1023 * otherwise del_timer_sync() can't detect that the timer's
1024 * handler yet has not finished. This also guarantees that the
1025 * timer is serialized wrt itself.
1027 if (likely(base
->running_timer
!= timer
)) {
1028 /* See the comment in lock_timer_base() */
1029 timer
->flags
|= TIMER_MIGRATING
;
1031 raw_spin_unlock(&base
->lock
);
1033 raw_spin_lock(&base
->lock
);
1034 WRITE_ONCE(timer
->flags
,
1035 (timer
->flags
& ~TIMER_BASEMASK
) | base
->cpu
);
1036 forward_timer_base(base
);
1040 debug_activate(timer
, expires
);
1042 timer
->expires
= expires
;
1044 * If 'idx' was calculated above and the base time did not advance
1045 * between calculating 'idx' and possibly switching the base, only
1046 * enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
1047 * we need to (re)calculate the wheel index via
1048 * internal_add_timer().
1050 if (idx
!= UINT_MAX
&& clk
== base
->clk
) {
1051 enqueue_timer(base
, timer
, idx
);
1052 trigger_dyntick_cpu(base
, timer
);
1054 internal_add_timer(base
, timer
);
1058 raw_spin_unlock_irqrestore(&base
->lock
, flags
);
1064 * mod_timer_pending - modify a pending timer's timeout
1065 * @timer: the pending timer to be modified
1066 * @expires: new timeout in jiffies
1068 * mod_timer_pending() is the same for pending timers as mod_timer(),
1069 * but will not re-activate and modify already deleted timers.
1071 * It is useful for unserialized use of timers.
1073 int mod_timer_pending(struct timer_list
*timer
, unsigned long expires
)
1075 return __mod_timer(timer
, expires
, MOD_TIMER_PENDING_ONLY
);
1077 EXPORT_SYMBOL(mod_timer_pending
);
1080 * mod_timer - modify a timer's timeout
1081 * @timer: the timer to be modified
1082 * @expires: new timeout in jiffies
1084 * mod_timer() is a more efficient way to update the expire field of an
1085 * active timer (if the timer is inactive it will be activated)
1087 * mod_timer(timer, expires) is equivalent to:
1089 * del_timer(timer); timer->expires = expires; add_timer(timer);
1091 * Note that if there are multiple unserialized concurrent users of the
1092 * same timer, then mod_timer() is the only safe way to modify the timeout,
1093 * since add_timer() cannot modify an already running timer.
1095 * The function returns whether it has modified a pending timer or not.
1096 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1097 * active timer returns 1.)
1099 int mod_timer(struct timer_list
*timer
, unsigned long expires
)
1101 return __mod_timer(timer
, expires
, 0);
1103 EXPORT_SYMBOL(mod_timer
);
1106 * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1107 * @timer: The timer to be modified
1108 * @expires: New timeout in jiffies
1110 * timer_reduce() is very similar to mod_timer(), except that it will only
1111 * modify a running timer if that would reduce the expiration time (it will
1112 * start a timer that isn't running).
1114 int timer_reduce(struct timer_list
*timer
, unsigned long expires
)
1116 return __mod_timer(timer
, expires
, MOD_TIMER_REDUCE
);
1118 EXPORT_SYMBOL(timer_reduce
);
1121 * add_timer - start a timer
1122 * @timer: the timer to be added
1124 * The kernel will do a ->function(@timer) callback from the
1125 * timer interrupt at the ->expires point in the future. The
1126 * current time is 'jiffies'.
1128 * The timer's ->expires, ->function fields must be set prior calling this
1131 * Timers with an ->expires field in the past will be executed in the next
1134 void add_timer(struct timer_list
*timer
)
1136 BUG_ON(timer_pending(timer
));
1137 mod_timer(timer
, timer
->expires
);
1139 EXPORT_SYMBOL(add_timer
);
1142 * add_timer_on - start a timer on a particular CPU
1143 * @timer: the timer to be added
1144 * @cpu: the CPU to start it on
1146 * This is not very scalable on SMP. Double adds are not possible.
1148 void add_timer_on(struct timer_list
*timer
, int cpu
)
1150 struct timer_base
*new_base
, *base
;
1151 unsigned long flags
;
1153 BUG_ON(timer_pending(timer
) || !timer
->function
);
1155 new_base
= get_timer_cpu_base(timer
->flags
, cpu
);
1158 * If @timer was on a different CPU, it should be migrated with the
1159 * old base locked to prevent other operations proceeding with the
1160 * wrong base locked. See lock_timer_base().
1162 base
= lock_timer_base(timer
, &flags
);
1163 if (base
!= new_base
) {
1164 timer
->flags
|= TIMER_MIGRATING
;
1166 raw_spin_unlock(&base
->lock
);
1168 raw_spin_lock(&base
->lock
);
1169 WRITE_ONCE(timer
->flags
,
1170 (timer
->flags
& ~TIMER_BASEMASK
) | cpu
);
1172 forward_timer_base(base
);
1174 debug_activate(timer
, timer
->expires
);
1175 internal_add_timer(base
, timer
);
1176 raw_spin_unlock_irqrestore(&base
->lock
, flags
);
1178 EXPORT_SYMBOL_GPL(add_timer_on
);
1181 * del_timer - deactivate a timer.
1182 * @timer: the timer to be deactivated
1184 * del_timer() deactivates a timer - this works on both active and inactive
1187 * The function returns whether it has deactivated a pending timer or not.
1188 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1189 * active timer returns 1.)
1191 int del_timer(struct timer_list
*timer
)
1193 struct timer_base
*base
;
1194 unsigned long flags
;
1197 debug_assert_init(timer
);
1199 if (timer_pending(timer
)) {
1200 base
= lock_timer_base(timer
, &flags
);
1201 ret
= detach_if_pending(timer
, base
, true);
1202 raw_spin_unlock_irqrestore(&base
->lock
, flags
);
1207 EXPORT_SYMBOL(del_timer
);
1210 * try_to_del_timer_sync - Try to deactivate a timer
1211 * @timer: timer to delete
1213 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1214 * exit the timer is not queued and the handler is not running on any CPU.
1216 int try_to_del_timer_sync(struct timer_list
*timer
)
1218 struct timer_base
*base
;
1219 unsigned long flags
;
1222 debug_assert_init(timer
);
1224 base
= lock_timer_base(timer
, &flags
);
1226 if (base
->running_timer
!= timer
)
1227 ret
= detach_if_pending(timer
, base
, true);
1229 raw_spin_unlock_irqrestore(&base
->lock
, flags
);
1233 EXPORT_SYMBOL(try_to_del_timer_sync
);
1237 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1238 * @timer: the timer to be deactivated
1240 * This function only differs from del_timer() on SMP: besides deactivating
1241 * the timer it also makes sure the handler has finished executing on other
1244 * Synchronization rules: Callers must prevent restarting of the timer,
1245 * otherwise this function is meaningless. It must not be called from
1246 * interrupt contexts unless the timer is an irqsafe one. The caller must
1247 * not hold locks which would prevent completion of the timer's
1248 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1249 * timer is not queued and the handler is not running on any CPU.
1251 * Note: For !irqsafe timers, you must not hold locks that are held in
1252 * interrupt context while calling this function. Even if the lock has
1253 * nothing to do with the timer in question. Here's why::
1259 * base->running_timer = mytimer;
1260 * spin_lock_irq(somelock);
1262 * spin_lock(somelock);
1263 * del_timer_sync(mytimer);
1264 * while (base->running_timer == mytimer);
1266 * Now del_timer_sync() will never return and never release somelock.
1267 * The interrupt on the other CPU is waiting to grab somelock but
1268 * it has interrupted the softirq that CPU0 is waiting to finish.
1270 * The function returns whether it has deactivated a pending timer or not.
1272 int del_timer_sync(struct timer_list
*timer
)
1274 #ifdef CONFIG_LOCKDEP
1275 unsigned long flags
;
1278 * If lockdep gives a backtrace here, please reference
1279 * the synchronization rules above.
1281 local_irq_save(flags
);
1282 lock_map_acquire(&timer
->lockdep_map
);
1283 lock_map_release(&timer
->lockdep_map
);
1284 local_irq_restore(flags
);
1287 * don't use it in hardirq context, because it
1288 * could lead to deadlock.
1290 WARN_ON(in_irq() && !(timer
->flags
& TIMER_IRQSAFE
));
1292 int ret
= try_to_del_timer_sync(timer
);
1298 EXPORT_SYMBOL(del_timer_sync
);
1301 static void call_timer_fn(struct timer_list
*timer
, void (*fn
)(struct timer_list
*))
1303 int count
= preempt_count();
1305 #ifdef CONFIG_LOCKDEP
1307 * It is permissible to free the timer from inside the
1308 * function that is called from it, this we need to take into
1309 * account for lockdep too. To avoid bogus "held lock freed"
1310 * warnings as well as problems when looking into
1311 * timer->lockdep_map, make a copy and use that here.
1313 struct lockdep_map lockdep_map
;
1315 lockdep_copy_map(&lockdep_map
, &timer
->lockdep_map
);
1318 * Couple the lock chain with the lock chain at
1319 * del_timer_sync() by acquiring the lock_map around the fn()
1320 * call here and in del_timer_sync().
1322 lock_map_acquire(&lockdep_map
);
1324 trace_timer_expire_entry(timer
);
1326 trace_timer_expire_exit(timer
);
1328 lock_map_release(&lockdep_map
);
1330 if (count
!= preempt_count()) {
1331 WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1332 fn
, count
, preempt_count());
1334 * Restore the preempt count. That gives us a decent
1335 * chance to survive and extract information. If the
1336 * callback kept a lock held, bad luck, but not worse
1337 * than the BUG() we had.
1339 preempt_count_set(count
);
1343 static void expire_timers(struct timer_base
*base
, struct hlist_head
*head
)
1345 while (!hlist_empty(head
)) {
1346 struct timer_list
*timer
;
1347 void (*fn
)(struct timer_list
*);
1349 timer
= hlist_entry(head
->first
, struct timer_list
, entry
);
1351 base
->running_timer
= timer
;
1352 detach_timer(timer
, true);
1354 fn
= timer
->function
;
1356 if (timer
->flags
& TIMER_IRQSAFE
) {
1357 raw_spin_unlock(&base
->lock
);
1358 call_timer_fn(timer
, fn
);
1359 raw_spin_lock(&base
->lock
);
1361 raw_spin_unlock_irq(&base
->lock
);
1362 call_timer_fn(timer
, fn
);
1363 raw_spin_lock_irq(&base
->lock
);
1368 static int __collect_expired_timers(struct timer_base
*base
,
1369 struct hlist_head
*heads
)
1371 unsigned long clk
= base
->clk
;
1372 struct hlist_head
*vec
;
1376 for (i
= 0; i
< LVL_DEPTH
; i
++) {
1377 idx
= (clk
& LVL_MASK
) + i
* LVL_SIZE
;
1379 if (__test_and_clear_bit(idx
, base
->pending_map
)) {
1380 vec
= base
->vectors
+ idx
;
1381 hlist_move_list(vec
, heads
++);
1384 /* Is it time to look at the next level? */
1385 if (clk
& LVL_CLK_MASK
)
1387 /* Shift clock for the next level granularity */
1388 clk
>>= LVL_CLK_SHIFT
;
1393 #ifdef CONFIG_NO_HZ_COMMON
1395 * Find the next pending bucket of a level. Search from level start (@offset)
1396 * + @clk upwards and if nothing there, search from start of the level
1397 * (@offset) up to @offset + clk.
1399 static int next_pending_bucket(struct timer_base
*base
, unsigned offset
,
1402 unsigned pos
, start
= offset
+ clk
;
1403 unsigned end
= offset
+ LVL_SIZE
;
1405 pos
= find_next_bit(base
->pending_map
, end
, start
);
1409 pos
= find_next_bit(base
->pending_map
, start
, offset
);
1410 return pos
< start
? pos
+ LVL_SIZE
- start
: -1;
1414 * Search the first expiring timer in the various clock levels. Caller must
1417 static unsigned long __next_timer_interrupt(struct timer_base
*base
)
1419 unsigned long clk
, next
, adj
;
1420 unsigned lvl
, offset
= 0;
1422 next
= base
->clk
+ NEXT_TIMER_MAX_DELTA
;
1424 for (lvl
= 0; lvl
< LVL_DEPTH
; lvl
++, offset
+= LVL_SIZE
) {
1425 int pos
= next_pending_bucket(base
, offset
, clk
& LVL_MASK
);
1428 unsigned long tmp
= clk
+ (unsigned long) pos
;
1430 tmp
<<= LVL_SHIFT(lvl
);
1431 if (time_before(tmp
, next
))
1435 * Clock for the next level. If the current level clock lower
1436 * bits are zero, we look at the next level as is. If not we
1437 * need to advance it by one because that's going to be the
1438 * next expiring bucket in that level. base->clk is the next
1439 * expiring jiffie. So in case of:
1441 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1444 * we have to look at all levels @index 0. With
1446 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1449 * LVL0 has the next expiring bucket @index 2. The upper
1450 * levels have the next expiring bucket @index 1.
1452 * In case that the propagation wraps the next level the same
1455 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1458 * So after looking at LVL0 we get:
1460 * LVL5 LVL4 LVL3 LVL2 LVL1
1463 * So no propagation from LVL1 to LVL2 because that happened
1464 * with the add already, but then we need to propagate further
1465 * from LVL2 to LVL3.
1467 * So the simple check whether the lower bits of the current
1468 * level are 0 or not is sufficient for all cases.
1470 adj
= clk
& LVL_CLK_MASK
? 1 : 0;
1471 clk
>>= LVL_CLK_SHIFT
;
1478 * Check, if the next hrtimer event is before the next timer wheel
1481 static u64
cmp_next_hrtimer_event(u64 basem
, u64 expires
)
1483 u64 nextevt
= hrtimer_get_next_event();
1486 * If high resolution timers are enabled
1487 * hrtimer_get_next_event() returns KTIME_MAX.
1489 if (expires
<= nextevt
)
1493 * If the next timer is already expired, return the tick base
1494 * time so the tick is fired immediately.
1496 if (nextevt
<= basem
)
1500 * Round up to the next jiffie. High resolution timers are
1501 * off, so the hrtimers are expired in the tick and we need to
1502 * make sure that this tick really expires the timer to avoid
1503 * a ping pong of the nohz stop code.
1505 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1507 return DIV_ROUND_UP_ULL(nextevt
, TICK_NSEC
) * TICK_NSEC
;
1511 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1512 * @basej: base time jiffies
1513 * @basem: base time clock monotonic
1515 * Returns the tick aligned clock monotonic time of the next pending
1516 * timer or KTIME_MAX if no timer is pending.
1518 u64
get_next_timer_interrupt(unsigned long basej
, u64 basem
)
1520 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1521 u64 expires
= KTIME_MAX
;
1522 unsigned long nextevt
;
1526 * Pretend that there is no timer pending if the cpu is offline.
1527 * Possible pending timers will be migrated later to an active cpu.
1529 if (cpu_is_offline(smp_processor_id()))
1532 raw_spin_lock(&base
->lock
);
1533 nextevt
= __next_timer_interrupt(base
);
1534 is_max_delta
= (nextevt
== base
->clk
+ NEXT_TIMER_MAX_DELTA
);
1535 base
->next_expiry
= nextevt
;
1537 * We have a fresh next event. Check whether we can forward the
1538 * base. We can only do that when @basej is past base->clk
1539 * otherwise we might rewind base->clk.
1541 if (time_after(basej
, base
->clk
)) {
1542 if (time_after(nextevt
, basej
))
1544 else if (time_after(nextevt
, base
->clk
))
1545 base
->clk
= nextevt
;
1548 if (time_before_eq(nextevt
, basej
)) {
1550 base
->is_idle
= false;
1553 expires
= basem
+ (u64
)(nextevt
- basej
) * TICK_NSEC
;
1555 * If we expect to sleep more than a tick, mark the base idle.
1556 * Also the tick is stopped so any added timer must forward
1557 * the base clk itself to keep granularity small. This idle
1558 * logic is only maintained for the BASE_STD base, deferrable
1559 * timers may still see large granularity skew (by design).
1561 if ((expires
- basem
) > TICK_NSEC
) {
1562 base
->must_forward_clk
= true;
1563 base
->is_idle
= true;
1566 raw_spin_unlock(&base
->lock
);
1568 return cmp_next_hrtimer_event(basem
, expires
);
1572 * timer_clear_idle - Clear the idle state of the timer base
1574 * Called with interrupts disabled
1576 void timer_clear_idle(void)
1578 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1581 * We do this unlocked. The worst outcome is a remote enqueue sending
1582 * a pointless IPI, but taking the lock would just make the window for
1583 * sending the IPI a few instructions smaller for the cost of taking
1584 * the lock in the exit from idle path.
1586 base
->is_idle
= false;
1589 static int collect_expired_timers(struct timer_base
*base
,
1590 struct hlist_head
*heads
)
1593 * NOHZ optimization. After a long idle sleep we need to forward the
1594 * base to current jiffies. Avoid a loop by searching the bitfield for
1595 * the next expiring timer.
1597 if ((long)(jiffies
- base
->clk
) > 2) {
1598 unsigned long next
= __next_timer_interrupt(base
);
1601 * If the next timer is ahead of time forward to current
1602 * jiffies, otherwise forward to the next expiry time:
1604 if (time_after(next
, jiffies
)) {
1606 * The call site will increment base->clk and then
1607 * terminate the expiry loop immediately.
1609 base
->clk
= jiffies
;
1614 return __collect_expired_timers(base
, heads
);
1617 static inline int collect_expired_timers(struct timer_base
*base
,
1618 struct hlist_head
*heads
)
1620 return __collect_expired_timers(base
, heads
);
1625 * Called from the timer interrupt handler to charge one tick to the current
1626 * process. user_tick is 1 if the tick is user time, 0 for system.
1628 void update_process_times(int user_tick
)
1630 struct task_struct
*p
= current
;
1632 /* Note: this timer irq context must be accounted for as well. */
1633 account_process_tick(p
, user_tick
);
1635 rcu_check_callbacks(user_tick
);
1636 #ifdef CONFIG_IRQ_WORK
1641 if (IS_ENABLED(CONFIG_POSIX_TIMERS
))
1642 run_posix_cpu_timers(p
);
1646 * __run_timers - run all expired timers (if any) on this CPU.
1647 * @base: the timer vector to be processed.
1649 static inline void __run_timers(struct timer_base
*base
)
1651 struct hlist_head heads
[LVL_DEPTH
];
1654 if (!time_after_eq(jiffies
, base
->clk
))
1657 raw_spin_lock_irq(&base
->lock
);
1660 * timer_base::must_forward_clk must be cleared before running
1661 * timers so that any timer functions that call mod_timer() will
1662 * not try to forward the base. Idle tracking / clock forwarding
1663 * logic is only used with BASE_STD timers.
1665 * The must_forward_clk flag is cleared unconditionally also for
1666 * the deferrable base. The deferrable base is not affected by idle
1667 * tracking and never forwarded, so clearing the flag is a NOOP.
1669 * The fact that the deferrable base is never forwarded can cause
1670 * large variations in granularity for deferrable timers, but they
1671 * can be deferred for long periods due to idle anyway.
1673 base
->must_forward_clk
= false;
1675 while (time_after_eq(jiffies
, base
->clk
)) {
1677 levels
= collect_expired_timers(base
, heads
);
1681 expire_timers(base
, heads
+ levels
);
1683 base
->running_timer
= NULL
;
1684 raw_spin_unlock_irq(&base
->lock
);
1688 * This function runs timers and the timer-tq in bottom half context.
1690 static __latent_entropy
void run_timer_softirq(struct softirq_action
*h
)
1692 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1695 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
))
1696 __run_timers(this_cpu_ptr(&timer_bases
[BASE_DEF
]));
1700 * Called by the local, per-CPU timer interrupt on SMP.
1702 void run_local_timers(void)
1704 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1706 hrtimer_run_queues();
1707 /* Raise the softirq only if required. */
1708 if (time_before(jiffies
, base
->clk
)) {
1709 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON
))
1711 /* CPU is awake, so check the deferrable base. */
1713 if (time_before(jiffies
, base
->clk
))
1716 raise_softirq(TIMER_SOFTIRQ
);
1720 * Since schedule_timeout()'s timer is defined on the stack, it must store
1721 * the target task on the stack as well.
1723 struct process_timer
{
1724 struct timer_list timer
;
1725 struct task_struct
*task
;
1728 static void process_timeout(struct timer_list
*t
)
1730 struct process_timer
*timeout
= from_timer(timeout
, t
, timer
);
1732 wake_up_process(timeout
->task
);
1736 * schedule_timeout - sleep until timeout
1737 * @timeout: timeout value in jiffies
1739 * Make the current task sleep until @timeout jiffies have
1740 * elapsed. The routine will return immediately unless
1741 * the current task state has been set (see set_current_state()).
1743 * You can set the task state as follows -
1745 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1746 * pass before the routine returns unless the current task is explicitly
1747 * woken up, (e.g. by wake_up_process())".
1749 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1750 * delivered to the current task or the current task is explicitly woken
1753 * The current task state is guaranteed to be TASK_RUNNING when this
1756 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1757 * the CPU away without a bound on the timeout. In this case the return
1758 * value will be %MAX_SCHEDULE_TIMEOUT.
1760 * Returns 0 when the timer has expired otherwise the remaining time in
1761 * jiffies will be returned. In all cases the return value is guaranteed
1762 * to be non-negative.
1764 signed long __sched
schedule_timeout(signed long timeout
)
1766 struct process_timer timer
;
1767 unsigned long expire
;
1771 case MAX_SCHEDULE_TIMEOUT
:
1773 * These two special cases are useful to be comfortable
1774 * in the caller. Nothing more. We could take
1775 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1776 * but I' d like to return a valid offset (>=0) to allow
1777 * the caller to do everything it want with the retval.
1783 * Another bit of PARANOID. Note that the retval will be
1784 * 0 since no piece of kernel is supposed to do a check
1785 * for a negative retval of schedule_timeout() (since it
1786 * should never happens anyway). You just have the printk()
1787 * that will tell you if something is gone wrong and where.
1790 printk(KERN_ERR
"schedule_timeout: wrong timeout "
1791 "value %lx\n", timeout
);
1793 current
->state
= TASK_RUNNING
;
1798 expire
= timeout
+ jiffies
;
1800 timer
.task
= current
;
1801 timer_setup_on_stack(&timer
.timer
, process_timeout
, 0);
1802 __mod_timer(&timer
.timer
, expire
, 0);
1804 del_singleshot_timer_sync(&timer
.timer
);
1806 /* Remove the timer from the object tracker */
1807 destroy_timer_on_stack(&timer
.timer
);
1809 timeout
= expire
- jiffies
;
1812 return timeout
< 0 ? 0 : timeout
;
1814 EXPORT_SYMBOL(schedule_timeout
);
1817 * We can use __set_current_state() here because schedule_timeout() calls
1818 * schedule() unconditionally.
1820 signed long __sched
schedule_timeout_interruptible(signed long timeout
)
1822 __set_current_state(TASK_INTERRUPTIBLE
);
1823 return schedule_timeout(timeout
);
1825 EXPORT_SYMBOL(schedule_timeout_interruptible
);
1827 signed long __sched
schedule_timeout_killable(signed long timeout
)
1829 __set_current_state(TASK_KILLABLE
);
1830 return schedule_timeout(timeout
);
1832 EXPORT_SYMBOL(schedule_timeout_killable
);
1834 signed long __sched
schedule_timeout_uninterruptible(signed long timeout
)
1836 __set_current_state(TASK_UNINTERRUPTIBLE
);
1837 return schedule_timeout(timeout
);
1839 EXPORT_SYMBOL(schedule_timeout_uninterruptible
);
1842 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1845 signed long __sched
schedule_timeout_idle(signed long timeout
)
1847 __set_current_state(TASK_IDLE
);
1848 return schedule_timeout(timeout
);
1850 EXPORT_SYMBOL(schedule_timeout_idle
);
1852 #ifdef CONFIG_HOTPLUG_CPU
1853 static void migrate_timer_list(struct timer_base
*new_base
, struct hlist_head
*head
)
1855 struct timer_list
*timer
;
1856 int cpu
= new_base
->cpu
;
1858 while (!hlist_empty(head
)) {
1859 timer
= hlist_entry(head
->first
, struct timer_list
, entry
);
1860 detach_timer(timer
, false);
1861 timer
->flags
= (timer
->flags
& ~TIMER_BASEMASK
) | cpu
;
1862 internal_add_timer(new_base
, timer
);
1866 int timers_prepare_cpu(unsigned int cpu
)
1868 struct timer_base
*base
;
1871 for (b
= 0; b
< NR_BASES
; b
++) {
1872 base
= per_cpu_ptr(&timer_bases
[b
], cpu
);
1873 base
->clk
= jiffies
;
1874 base
->next_expiry
= base
->clk
+ NEXT_TIMER_MAX_DELTA
;
1875 base
->is_idle
= false;
1876 base
->must_forward_clk
= true;
1881 int timers_dead_cpu(unsigned int cpu
)
1883 struct timer_base
*old_base
;
1884 struct timer_base
*new_base
;
1887 BUG_ON(cpu_online(cpu
));
1889 for (b
= 0; b
< NR_BASES
; b
++) {
1890 old_base
= per_cpu_ptr(&timer_bases
[b
], cpu
);
1891 new_base
= get_cpu_ptr(&timer_bases
[b
]);
1893 * The caller is globally serialized and nobody else
1894 * takes two locks at once, deadlock is not possible.
1896 raw_spin_lock_irq(&new_base
->lock
);
1897 raw_spin_lock_nested(&old_base
->lock
, SINGLE_DEPTH_NESTING
);
1900 * The current CPUs base clock might be stale. Update it
1901 * before moving the timers over.
1903 forward_timer_base(new_base
);
1905 BUG_ON(old_base
->running_timer
);
1907 for (i
= 0; i
< WHEEL_SIZE
; i
++)
1908 migrate_timer_list(new_base
, old_base
->vectors
+ i
);
1910 raw_spin_unlock(&old_base
->lock
);
1911 raw_spin_unlock_irq(&new_base
->lock
);
1912 put_cpu_ptr(&timer_bases
);
1917 #endif /* CONFIG_HOTPLUG_CPU */
1919 static void __init
init_timer_cpu(int cpu
)
1921 struct timer_base
*base
;
1924 for (i
= 0; i
< NR_BASES
; i
++) {
1925 base
= per_cpu_ptr(&timer_bases
[i
], cpu
);
1927 raw_spin_lock_init(&base
->lock
);
1928 base
->clk
= jiffies
;
1932 static void __init
init_timer_cpus(void)
1936 for_each_possible_cpu(cpu
)
1937 init_timer_cpu(cpu
);
1940 void __init
init_timers(void)
1943 open_softirq(TIMER_SOFTIRQ
, run_timer_softirq
);
1947 * msleep - sleep safely even with waitqueue interruptions
1948 * @msecs: Time in milliseconds to sleep for
1950 void msleep(unsigned int msecs
)
1952 unsigned long timeout
= msecs_to_jiffies(msecs
) + 1;
1955 timeout
= schedule_timeout_uninterruptible(timeout
);
1958 EXPORT_SYMBOL(msleep
);
1961 * msleep_interruptible - sleep waiting for signals
1962 * @msecs: Time in milliseconds to sleep for
1964 unsigned long msleep_interruptible(unsigned int msecs
)
1966 unsigned long timeout
= msecs_to_jiffies(msecs
) + 1;
1968 while (timeout
&& !signal_pending(current
))
1969 timeout
= schedule_timeout_interruptible(timeout
);
1970 return jiffies_to_msecs(timeout
);
1973 EXPORT_SYMBOL(msleep_interruptible
);
1976 * usleep_range - Sleep for an approximate time
1977 * @min: Minimum time in usecs to sleep
1978 * @max: Maximum time in usecs to sleep
1980 * In non-atomic context where the exact wakeup time is flexible, use
1981 * usleep_range() instead of udelay(). The sleep improves responsiveness
1982 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
1983 * power usage by allowing hrtimers to take advantage of an already-
1984 * scheduled interrupt instead of scheduling a new one just for this sleep.
1986 void __sched
usleep_range(unsigned long min
, unsigned long max
)
1988 ktime_t exp
= ktime_add_us(ktime_get(), min
);
1989 u64 delta
= (u64
)(max
- min
) * NSEC_PER_USEC
;
1992 __set_current_state(TASK_UNINTERRUPTIBLE
);
1993 /* Do not return before the requested sleep time has elapsed */
1994 if (!schedule_hrtimeout_range(&exp
, delta
, HRTIMER_MODE_ABS
))
1998 EXPORT_SYMBOL(usleep_range
);