4 * Kernel internal timers
6 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
10 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
11 * "A Kernel Model for Precision Timekeeping" by Dave Mills
12 * 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
13 * serialize accesses to xtime/lost_ticks).
14 * Copyright (C) 1998 Andrea Arcangeli
15 * 1999-03-10 Improved NTP compatibility by Ulrich Windl
16 * 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
17 * 2000-10-05 Implemented scalable SMP per-CPU timer handling.
18 * Copyright (C) 2000, 2001, 2002 Ingo Molnar
19 * Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
22 #include <linux/kernel_stat.h>
23 #include <linux/export.h>
24 #include <linux/interrupt.h>
25 #include <linux/percpu.h>
26 #include <linux/init.h>
28 #include <linux/swap.h>
29 #include <linux/pid_namespace.h>
30 #include <linux/notifier.h>
31 #include <linux/thread_info.h>
32 #include <linux/time.h>
33 #include <linux/jiffies.h>
34 #include <linux/posix-timers.h>
35 #include <linux/cpu.h>
36 #include <linux/syscalls.h>
37 #include <linux/delay.h>
38 #include <linux/tick.h>
39 #include <linux/kallsyms.h>
40 #include <linux/irq_work.h>
41 #include <linux/sched.h>
42 #include <linux/sched/sysctl.h>
43 #include <linux/slab.h>
44 #include <linux/compat.h>
46 #include <asm/uaccess.h>
47 #include <asm/unistd.h>
48 #include <asm/div64.h>
49 #include <asm/timex.h>
52 #include "tick-internal.h"
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/timer.h>
57 __visible u64 jiffies_64 __cacheline_aligned_in_smp
= INITIAL_JIFFIES
;
59 EXPORT_SYMBOL(jiffies_64
);
62 * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
63 * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
64 * level has a different granularity.
66 * The level granularity is: LVL_CLK_DIV ^ lvl
67 * The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
69 * The array level of a newly armed timer depends on the relative expiry
70 * time. The farther the expiry time is away the higher the array level and
71 * therefor the granularity becomes.
73 * Contrary to the original timer wheel implementation, which aims for 'exact'
74 * expiry of the timers, this implementation removes the need for recascading
75 * the timers into the lower array levels. The previous 'classic' timer wheel
76 * implementation of the kernel already violated the 'exact' expiry by adding
77 * slack to the expiry time to provide batched expiration. The granularity
78 * levels provide implicit batching.
80 * This is an optimization of the original timer wheel implementation for the
81 * majority of the timer wheel use cases: timeouts. The vast majority of
82 * timeout timers (networking, disk I/O ...) are canceled before expiry. If
83 * the timeout expires it indicates that normal operation is disturbed, so it
84 * does not matter much whether the timeout comes with a slight delay.
86 * The only exception to this are networking timers with a small expiry
87 * time. They rely on the granularity. Those fit into the first wheel level,
88 * which has HZ granularity.
90 * We don't have cascading anymore. timers with a expiry time above the
91 * capacity of the last wheel level are force expired at the maximum timeout
92 * value of the last wheel level. From data sampling we know that the maximum
93 * value observed is 5 days (network connection tracking), so this should not
96 * The currently chosen array constants values are a good compromise between
97 * array size and granularity.
99 * This results in the following granularity and range levels:
102 * Level Offset Granularity Range
103 * 0 0 1 ms 0 ms - 63 ms
104 * 1 64 8 ms 64 ms - 511 ms
105 * 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
106 * 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
107 * 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
108 * 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
109 * 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
110 * 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
111 * 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
114 * Level Offset Granularity Range
115 * 0 0 3 ms 0 ms - 210 ms
116 * 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
117 * 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
118 * 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
119 * 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
120 * 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
121 * 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
122 * 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
123 * 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
126 * Level Offset Granularity Range
127 * 0 0 4 ms 0 ms - 255 ms
128 * 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
129 * 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
130 * 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
131 * 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
132 * 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
133 * 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
134 * 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
135 * 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
138 * Level Offset Granularity Range
139 * 0 0 10 ms 0 ms - 630 ms
140 * 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
141 * 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
142 * 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
143 * 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
144 * 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
145 * 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
146 * 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
149 /* Clock divisor for the next level */
150 #define LVL_CLK_SHIFT 3
151 #define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
152 #define LVL_CLK_MASK (LVL_CLK_DIV - 1)
153 #define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
154 #define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
157 * The time start value for each level to select the bucket at enqueue
160 #define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
162 /* Size of each clock level */
164 #define LVL_SIZE (1UL << LVL_BITS)
165 #define LVL_MASK (LVL_SIZE - 1)
166 #define LVL_OFFS(n) ((n) * LVL_SIZE)
175 /* The cutoff (max. capacity of the wheel) */
176 #define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
177 #define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
180 * The resulting wheel size. If NOHZ is configured we allocate two
181 * wheels so we have a separate storage for the deferrable timers.
183 #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
185 #ifdef CONFIG_NO_HZ_COMMON
197 struct timer_list
*running_timer
;
199 unsigned long next_expiry
;
201 bool migration_enabled
;
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 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
211 unsigned int sysctl_timer_migration
= 1;
213 void timers_update_migration(bool update_nohz
)
215 bool on
= sysctl_timer_migration
&& tick_nohz_active
;
218 /* Avoid the loop, if nothing to update */
219 if (this_cpu_read(timer_bases
[BASE_STD
].migration_enabled
) == on
)
222 for_each_possible_cpu(cpu
) {
223 per_cpu(timer_bases
[BASE_STD
].migration_enabled
, cpu
) = on
;
224 per_cpu(timer_bases
[BASE_DEF
].migration_enabled
, cpu
) = on
;
225 per_cpu(hrtimer_bases
.migration_enabled
, cpu
) = on
;
228 per_cpu(timer_bases
[BASE_STD
].nohz_active
, cpu
) = true;
229 per_cpu(timer_bases
[BASE_DEF
].nohz_active
, cpu
) = true;
230 per_cpu(hrtimer_bases
.nohz_active
, cpu
) = true;
234 int timer_migration_handler(struct ctl_table
*table
, int write
,
235 void __user
*buffer
, size_t *lenp
,
238 static DEFINE_MUTEX(mutex
);
242 ret
= proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
244 timers_update_migration(false);
245 mutex_unlock(&mutex
);
250 static unsigned long round_jiffies_common(unsigned long j
, int cpu
,
254 unsigned long original
= j
;
257 * We don't want all cpus firing their timers at once hitting the
258 * same lock or cachelines, so we skew each extra cpu with an extra
259 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
261 * The skew is done by adding 3*cpunr, then round, then subtract this
262 * extra offset again.
269 * If the target jiffie is just after a whole second (which can happen
270 * due to delays of the timer irq, long irq off times etc etc) then
271 * we should round down to the whole second, not up. Use 1/4th second
272 * as cutoff for this rounding as an extreme upper bound for this.
273 * But never round down if @force_up is set.
275 if (rem
< HZ
/4 && !force_up
) /* round down */
280 /* now that we have rounded, subtract the extra skew again */
284 * Make sure j is still in the future. Otherwise return the
287 return time_is_after_jiffies(j
) ? j
: original
;
291 * __round_jiffies - function to round jiffies to a full second
292 * @j: the time in (absolute) jiffies that should be rounded
293 * @cpu: the processor number on which the timeout will happen
295 * __round_jiffies() rounds an absolute time in the future (in jiffies)
296 * up or down to (approximately) full seconds. This is useful for timers
297 * for which the exact time they fire does not matter too much, as long as
298 * they fire approximately every X seconds.
300 * By rounding these timers to whole seconds, all such timers will fire
301 * at the same time, rather than at various times spread out. The goal
302 * of this is to have the CPU wake up less, which saves power.
304 * The exact rounding is skewed for each processor to avoid all
305 * processors firing at the exact same time, which could lead
306 * to lock contention or spurious cache line bouncing.
308 * The return value is the rounded version of the @j parameter.
310 unsigned long __round_jiffies(unsigned long j
, int cpu
)
312 return round_jiffies_common(j
, cpu
, false);
314 EXPORT_SYMBOL_GPL(__round_jiffies
);
317 * __round_jiffies_relative - function to round jiffies to a full second
318 * @j: the time in (relative) jiffies that should be rounded
319 * @cpu: the processor number on which the timeout will happen
321 * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
322 * up or down to (approximately) full seconds. This is useful for timers
323 * for which the exact time they fire does not matter too much, as long as
324 * they fire approximately every X seconds.
326 * By rounding these timers to whole seconds, all such timers will fire
327 * at the same time, rather than at various times spread out. The goal
328 * of this is to have the CPU wake up less, which saves power.
330 * The exact rounding is skewed for each processor to avoid all
331 * processors firing at the exact same time, which could lead
332 * to lock contention or spurious cache line bouncing.
334 * The return value is the rounded version of the @j parameter.
336 unsigned long __round_jiffies_relative(unsigned long j
, int cpu
)
338 unsigned long j0
= jiffies
;
340 /* Use j0 because jiffies might change while we run */
341 return round_jiffies_common(j
+ j0
, cpu
, false) - j0
;
343 EXPORT_SYMBOL_GPL(__round_jiffies_relative
);
346 * round_jiffies - function to round jiffies to a full second
347 * @j: the time in (absolute) jiffies that should be rounded
349 * round_jiffies() rounds an absolute time in the future (in jiffies)
350 * up or down to (approximately) full seconds. This is useful for timers
351 * for which the exact time they fire does not matter too much, as long as
352 * they fire approximately every X seconds.
354 * By rounding these timers to whole seconds, all such timers will fire
355 * at the same time, rather than at various times spread out. The goal
356 * of this is to have the CPU wake up less, which saves power.
358 * The return value is the rounded version of the @j parameter.
360 unsigned long round_jiffies(unsigned long j
)
362 return round_jiffies_common(j
, raw_smp_processor_id(), false);
364 EXPORT_SYMBOL_GPL(round_jiffies
);
367 * round_jiffies_relative - function to round jiffies to a full second
368 * @j: the time in (relative) jiffies that should be rounded
370 * round_jiffies_relative() rounds a time delta in the future (in jiffies)
371 * up or down to (approximately) full seconds. This is useful for timers
372 * for which the exact time they fire does not matter too much, as long as
373 * they fire approximately every X seconds.
375 * By rounding these timers to whole seconds, all such timers will fire
376 * at the same time, rather than at various times spread out. The goal
377 * of this is to have the CPU wake up less, which saves power.
379 * The return value is the rounded version of the @j parameter.
381 unsigned long round_jiffies_relative(unsigned long j
)
383 return __round_jiffies_relative(j
, raw_smp_processor_id());
385 EXPORT_SYMBOL_GPL(round_jiffies_relative
);
388 * __round_jiffies_up - function to round jiffies up to a full second
389 * @j: the time in (absolute) jiffies that should be rounded
390 * @cpu: the processor number on which the timeout will happen
392 * This is the same as __round_jiffies() except that it will never
393 * round down. This is useful for timeouts for which the exact time
394 * of firing does not matter too much, as long as they don't fire too
397 unsigned long __round_jiffies_up(unsigned long j
, int cpu
)
399 return round_jiffies_common(j
, cpu
, true);
401 EXPORT_SYMBOL_GPL(__round_jiffies_up
);
404 * __round_jiffies_up_relative - function to round jiffies up to a full second
405 * @j: the time in (relative) jiffies that should be rounded
406 * @cpu: the processor number on which the timeout will happen
408 * This is the same as __round_jiffies_relative() except that it will never
409 * round down. This is useful for timeouts for which the exact time
410 * of firing does not matter too much, as long as they don't fire too
413 unsigned long __round_jiffies_up_relative(unsigned long j
, int cpu
)
415 unsigned long j0
= jiffies
;
417 /* Use j0 because jiffies might change while we run */
418 return round_jiffies_common(j
+ j0
, cpu
, true) - j0
;
420 EXPORT_SYMBOL_GPL(__round_jiffies_up_relative
);
423 * round_jiffies_up - function to round jiffies up to a full second
424 * @j: the time in (absolute) jiffies that should be rounded
426 * This is the same as round_jiffies() except that it will never
427 * round down. This is useful for timeouts for which the exact time
428 * of firing does not matter too much, as long as they don't fire too
431 unsigned long round_jiffies_up(unsigned long j
)
433 return round_jiffies_common(j
, raw_smp_processor_id(), true);
435 EXPORT_SYMBOL_GPL(round_jiffies_up
);
438 * round_jiffies_up_relative - function to round jiffies up to a full second
439 * @j: the time in (relative) jiffies that should be rounded
441 * This is the same as round_jiffies_relative() except that it will never
442 * round down. This is useful for timeouts for which the exact time
443 * of firing does not matter too much, as long as they don't fire too
446 unsigned long round_jiffies_up_relative(unsigned long j
)
448 return __round_jiffies_up_relative(j
, raw_smp_processor_id());
450 EXPORT_SYMBOL_GPL(round_jiffies_up_relative
);
453 static inline unsigned int timer_get_idx(struct timer_list
*timer
)
455 return (timer
->flags
& TIMER_ARRAYMASK
) >> TIMER_ARRAYSHIFT
;
458 static inline void timer_set_idx(struct timer_list
*timer
, unsigned int idx
)
460 timer
->flags
= (timer
->flags
& ~TIMER_ARRAYMASK
) |
461 idx
<< TIMER_ARRAYSHIFT
;
465 * Helper function to calculate the array index for a given expiry
468 static inline unsigned calc_index(unsigned expires
, unsigned lvl
)
470 expires
= (expires
+ LVL_GRAN(lvl
)) >> LVL_SHIFT(lvl
);
471 return LVL_OFFS(lvl
) + (expires
& LVL_MASK
);
474 static int calc_wheel_index(unsigned long expires
, unsigned long clk
)
476 unsigned long delta
= expires
- clk
;
479 if (delta
< LVL_START(1)) {
480 idx
= calc_index(expires
, 0);
481 } else if (delta
< LVL_START(2)) {
482 idx
= calc_index(expires
, 1);
483 } else if (delta
< LVL_START(3)) {
484 idx
= calc_index(expires
, 2);
485 } else if (delta
< LVL_START(4)) {
486 idx
= calc_index(expires
, 3);
487 } else if (delta
< LVL_START(5)) {
488 idx
= calc_index(expires
, 4);
489 } else if (delta
< LVL_START(6)) {
490 idx
= calc_index(expires
, 5);
491 } else if (delta
< LVL_START(7)) {
492 idx
= calc_index(expires
, 6);
493 } else if (LVL_DEPTH
> 8 && delta
< LVL_START(8)) {
494 idx
= calc_index(expires
, 7);
495 } else if ((long) delta
< 0) {
496 idx
= clk
& LVL_MASK
;
499 * Force expire obscene large timeouts to expire at the
500 * capacity limit of the wheel.
502 if (expires
>= WHEEL_TIMEOUT_CUTOFF
)
503 expires
= WHEEL_TIMEOUT_MAX
;
505 idx
= calc_index(expires
, LVL_DEPTH
- 1);
511 * Enqueue the timer into the hash bucket, mark it pending in
512 * the bitmap and store the index in the timer flags.
514 static void enqueue_timer(struct timer_base
*base
, struct timer_list
*timer
,
517 hlist_add_head(&timer
->entry
, base
->vectors
+ idx
);
518 __set_bit(idx
, base
->pending_map
);
519 timer_set_idx(timer
, idx
);
523 __internal_add_timer(struct timer_base
*base
, struct timer_list
*timer
)
527 idx
= calc_wheel_index(timer
->expires
, base
->clk
);
528 enqueue_timer(base
, timer
, idx
);
532 trigger_dyntick_cpu(struct timer_base
*base
, struct timer_list
*timer
)
534 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON
) || !base
->nohz_active
)
538 * TODO: This wants some optimizing similar to the code below, but we
539 * will do that when we switch from push to pull for deferrable timers.
541 if (timer
->flags
& TIMER_DEFERRABLE
) {
542 if (tick_nohz_full_cpu(base
->cpu
))
543 wake_up_nohz_cpu(base
->cpu
);
548 * We might have to IPI the remote CPU if the base is idle and the
549 * timer is not deferrable. If the other CPU is on the way to idle
550 * then it can't set base->is_idle as we hold the base lock:
555 /* Check whether this is the new first expiring timer: */
556 if (time_after_eq(timer
->expires
, base
->next_expiry
))
560 * Set the next expiry time and kick the CPU so it can reevaluate the
563 base
->next_expiry
= timer
->expires
;
564 wake_up_nohz_cpu(base
->cpu
);
568 internal_add_timer(struct timer_base
*base
, struct timer_list
*timer
)
570 __internal_add_timer(base
, timer
);
571 trigger_dyntick_cpu(base
, timer
);
574 #ifdef CONFIG_TIMER_STATS
575 void __timer_stats_timer_set_start_info(struct timer_list
*timer
, void *addr
)
577 if (timer
->start_site
)
580 timer
->start_site
= addr
;
581 memcpy(timer
->start_comm
, current
->comm
, TASK_COMM_LEN
);
582 timer
->start_pid
= current
->pid
;
585 static void timer_stats_account_timer(struct timer_list
*timer
)
590 * start_site can be concurrently reset by
591 * timer_stats_timer_clear_start_info()
593 site
= READ_ONCE(timer
->start_site
);
597 timer_stats_update_stats(timer
, timer
->start_pid
, site
,
598 timer
->function
, timer
->start_comm
,
603 static void timer_stats_account_timer(struct timer_list
*timer
) {}
606 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
608 static struct debug_obj_descr timer_debug_descr
;
610 static void *timer_debug_hint(void *addr
)
612 return ((struct timer_list
*) addr
)->function
;
615 static bool timer_is_static_object(void *addr
)
617 struct timer_list
*timer
= addr
;
619 return (timer
->entry
.pprev
== NULL
&&
620 timer
->entry
.next
== TIMER_ENTRY_STATIC
);
624 * fixup_init is called when:
625 * - an active object is initialized
627 static bool timer_fixup_init(void *addr
, enum debug_obj_state state
)
629 struct timer_list
*timer
= addr
;
632 case ODEBUG_STATE_ACTIVE
:
633 del_timer_sync(timer
);
634 debug_object_init(timer
, &timer_debug_descr
);
641 /* Stub timer callback for improperly used timers. */
642 static void stub_timer(unsigned long data
)
648 * fixup_activate is called when:
649 * - an active object is activated
650 * - an unknown non-static object is activated
652 static bool timer_fixup_activate(void *addr
, enum debug_obj_state state
)
654 struct timer_list
*timer
= addr
;
657 case ODEBUG_STATE_NOTAVAILABLE
:
658 setup_timer(timer
, stub_timer
, 0);
661 case ODEBUG_STATE_ACTIVE
:
670 * fixup_free is called when:
671 * - an active object is freed
673 static bool timer_fixup_free(void *addr
, enum debug_obj_state state
)
675 struct timer_list
*timer
= addr
;
678 case ODEBUG_STATE_ACTIVE
:
679 del_timer_sync(timer
);
680 debug_object_free(timer
, &timer_debug_descr
);
688 * fixup_assert_init is called when:
689 * - an untracked/uninit-ed object is found
691 static bool timer_fixup_assert_init(void *addr
, enum debug_obj_state state
)
693 struct timer_list
*timer
= addr
;
696 case ODEBUG_STATE_NOTAVAILABLE
:
697 setup_timer(timer
, stub_timer
, 0);
704 static struct debug_obj_descr timer_debug_descr
= {
705 .name
= "timer_list",
706 .debug_hint
= timer_debug_hint
,
707 .is_static_object
= timer_is_static_object
,
708 .fixup_init
= timer_fixup_init
,
709 .fixup_activate
= timer_fixup_activate
,
710 .fixup_free
= timer_fixup_free
,
711 .fixup_assert_init
= timer_fixup_assert_init
,
714 static inline void debug_timer_init(struct timer_list
*timer
)
716 debug_object_init(timer
, &timer_debug_descr
);
719 static inline void debug_timer_activate(struct timer_list
*timer
)
721 debug_object_activate(timer
, &timer_debug_descr
);
724 static inline void debug_timer_deactivate(struct timer_list
*timer
)
726 debug_object_deactivate(timer
, &timer_debug_descr
);
729 static inline void debug_timer_free(struct timer_list
*timer
)
731 debug_object_free(timer
, &timer_debug_descr
);
734 static inline void debug_timer_assert_init(struct timer_list
*timer
)
736 debug_object_assert_init(timer
, &timer_debug_descr
);
739 static void do_init_timer(struct timer_list
*timer
, unsigned int flags
,
740 const char *name
, struct lock_class_key
*key
);
742 void init_timer_on_stack_key(struct timer_list
*timer
, unsigned int flags
,
743 const char *name
, struct lock_class_key
*key
)
745 debug_object_init_on_stack(timer
, &timer_debug_descr
);
746 do_init_timer(timer
, flags
, name
, key
);
748 EXPORT_SYMBOL_GPL(init_timer_on_stack_key
);
750 void destroy_timer_on_stack(struct timer_list
*timer
)
752 debug_object_free(timer
, &timer_debug_descr
);
754 EXPORT_SYMBOL_GPL(destroy_timer_on_stack
);
757 static inline void debug_timer_init(struct timer_list
*timer
) { }
758 static inline void debug_timer_activate(struct timer_list
*timer
) { }
759 static inline void debug_timer_deactivate(struct timer_list
*timer
) { }
760 static inline void debug_timer_assert_init(struct timer_list
*timer
) { }
763 static inline void debug_init(struct timer_list
*timer
)
765 debug_timer_init(timer
);
766 trace_timer_init(timer
);
770 debug_activate(struct timer_list
*timer
, unsigned long expires
)
772 debug_timer_activate(timer
);
773 trace_timer_start(timer
, expires
, timer
->flags
);
776 static inline void debug_deactivate(struct timer_list
*timer
)
778 debug_timer_deactivate(timer
);
779 trace_timer_cancel(timer
);
782 static inline void debug_assert_init(struct timer_list
*timer
)
784 debug_timer_assert_init(timer
);
787 static void do_init_timer(struct timer_list
*timer
, unsigned int flags
,
788 const char *name
, struct lock_class_key
*key
)
790 timer
->entry
.pprev
= NULL
;
791 timer
->flags
= flags
| raw_smp_processor_id();
792 #ifdef CONFIG_TIMER_STATS
793 timer
->start_site
= NULL
;
794 timer
->start_pid
= -1;
795 memset(timer
->start_comm
, 0, TASK_COMM_LEN
);
797 lockdep_init_map(&timer
->lockdep_map
, name
, key
, 0);
801 * init_timer_key - initialize a timer
802 * @timer: the timer to be initialized
803 * @flags: timer flags
804 * @name: name of the timer
805 * @key: lockdep class key of the fake lock used for tracking timer
806 * sync lock dependencies
808 * init_timer_key() must be done to a timer prior calling *any* of the
809 * other timer functions.
811 void init_timer_key(struct timer_list
*timer
, unsigned int flags
,
812 const char *name
, struct lock_class_key
*key
)
815 do_init_timer(timer
, flags
, name
, key
);
817 EXPORT_SYMBOL(init_timer_key
);
819 static inline void detach_timer(struct timer_list
*timer
, bool clear_pending
)
821 struct hlist_node
*entry
= &timer
->entry
;
823 debug_deactivate(timer
);
828 entry
->next
= LIST_POISON2
;
831 static int detach_if_pending(struct timer_list
*timer
, struct timer_base
*base
,
834 unsigned idx
= timer_get_idx(timer
);
836 if (!timer_pending(timer
))
839 if (hlist_is_singular_node(&timer
->entry
, base
->vectors
+ idx
))
840 __clear_bit(idx
, base
->pending_map
);
842 detach_timer(timer
, clear_pending
);
846 static inline struct timer_base
*get_timer_cpu_base(u32 tflags
, u32 cpu
)
848 struct timer_base
*base
= per_cpu_ptr(&timer_bases
[BASE_STD
], cpu
);
851 * If the timer is deferrable and nohz is active then we need to use
852 * the deferrable base.
854 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
) && base
->nohz_active
&&
855 (tflags
& TIMER_DEFERRABLE
))
856 base
= per_cpu_ptr(&timer_bases
[BASE_DEF
], cpu
);
860 static inline struct timer_base
*get_timer_this_cpu_base(u32 tflags
)
862 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
865 * If the timer is deferrable and nohz is active then we need to use
866 * the deferrable base.
868 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
) && base
->nohz_active
&&
869 (tflags
& TIMER_DEFERRABLE
))
870 base
= this_cpu_ptr(&timer_bases
[BASE_DEF
]);
874 static inline struct timer_base
*get_timer_base(u32 tflags
)
876 return get_timer_cpu_base(tflags
, tflags
& TIMER_CPUMASK
);
879 #ifdef CONFIG_NO_HZ_COMMON
880 static inline struct timer_base
*
881 __get_target_base(struct timer_base
*base
, unsigned tflags
)
884 if ((tflags
& TIMER_PINNED
) || !base
->migration_enabled
)
885 return get_timer_this_cpu_base(tflags
);
886 return get_timer_cpu_base(tflags
, get_nohz_timer_target());
888 return get_timer_this_cpu_base(tflags
);
892 static inline void forward_timer_base(struct timer_base
*base
)
895 * We only forward the base when it's idle and we have a delta between
896 * base clock and jiffies.
898 if (!base
->is_idle
|| (long) (jiffies
- base
->clk
) < 2)
902 * If the next expiry value is > jiffies, then we fast forward to
903 * jiffies otherwise we forward to the next expiry value.
905 if (time_after(base
->next_expiry
, jiffies
))
908 base
->clk
= base
->next_expiry
;
911 static inline struct timer_base
*
912 __get_target_base(struct timer_base
*base
, unsigned tflags
)
914 return get_timer_this_cpu_base(tflags
);
917 static inline void forward_timer_base(struct timer_base
*base
) { }
920 static inline struct timer_base
*
921 get_target_base(struct timer_base
*base
, unsigned tflags
)
923 struct timer_base
*target
= __get_target_base(base
, tflags
);
925 forward_timer_base(target
);
930 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
931 * that all timers which are tied to this base are locked, and the base itself
934 * So __run_timers/migrate_timers can safely modify all timers which could
935 * be found in the base->vectors array.
937 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
938 * to wait until the migration is done.
940 static struct timer_base
*lock_timer_base(struct timer_list
*timer
,
941 unsigned long *flags
)
942 __acquires(timer
->base
->lock
)
945 struct timer_base
*base
;
946 u32 tf
= timer
->flags
;
948 if (!(tf
& TIMER_MIGRATING
)) {
949 base
= get_timer_base(tf
);
950 spin_lock_irqsave(&base
->lock
, *flags
);
951 if (timer
->flags
== tf
)
953 spin_unlock_irqrestore(&base
->lock
, *flags
);
960 __mod_timer(struct timer_list
*timer
, unsigned long expires
, bool pending_only
)
962 struct timer_base
*base
, *new_base
;
963 unsigned int idx
= UINT_MAX
;
964 unsigned long clk
= 0, flags
;
968 * This is a common optimization triggered by the networking code - if
969 * the timer is re-modified to have the same timeout or ends up in the
970 * same array bucket then just return:
972 if (timer_pending(timer
)) {
973 if (timer
->expires
== expires
)
976 * Take the current timer_jiffies of base, but without holding
979 base
= get_timer_base(timer
->flags
);
982 idx
= calc_wheel_index(expires
, clk
);
985 * Retrieve and compare the array index of the pending
986 * timer. If it matches set the expiry to the new value so a
987 * subsequent call will exit in the expires check above.
989 if (idx
== timer_get_idx(timer
)) {
990 timer
->expires
= expires
;
995 timer_stats_timer_set_start_info(timer
);
996 BUG_ON(!timer
->function
);
998 base
= lock_timer_base(timer
, &flags
);
1000 ret
= detach_if_pending(timer
, base
, false);
1001 if (!ret
&& pending_only
)
1004 debug_activate(timer
, expires
);
1006 new_base
= get_target_base(base
, timer
->flags
);
1008 if (base
!= new_base
) {
1010 * We are trying to schedule the timer on the new base.
1011 * However we can't change timer's base while it is running,
1012 * otherwise del_timer_sync() can't detect that the timer's
1013 * handler yet has not finished. This also guarantees that the
1014 * timer is serialized wrt itself.
1016 if (likely(base
->running_timer
!= timer
)) {
1017 /* See the comment in lock_timer_base() */
1018 timer
->flags
|= TIMER_MIGRATING
;
1020 spin_unlock(&base
->lock
);
1022 spin_lock(&base
->lock
);
1023 WRITE_ONCE(timer
->flags
,
1024 (timer
->flags
& ~TIMER_BASEMASK
) | base
->cpu
);
1028 timer
->expires
= expires
;
1030 * If 'idx' was calculated above and the base time did not advance
1031 * between calculating 'idx' and taking the lock, only enqueue_timer()
1032 * and trigger_dyntick_cpu() is required. Otherwise we need to
1033 * (re)calculate the wheel index via internal_add_timer().
1035 if (idx
!= UINT_MAX
&& clk
== base
->clk
) {
1036 enqueue_timer(base
, timer
, idx
);
1037 trigger_dyntick_cpu(base
, timer
);
1039 internal_add_timer(base
, timer
);
1043 spin_unlock_irqrestore(&base
->lock
, flags
);
1049 * mod_timer_pending - modify a pending timer's timeout
1050 * @timer: the pending timer to be modified
1051 * @expires: new timeout in jiffies
1053 * mod_timer_pending() is the same for pending timers as mod_timer(),
1054 * but will not re-activate and modify already deleted timers.
1056 * It is useful for unserialized use of timers.
1058 int mod_timer_pending(struct timer_list
*timer
, unsigned long expires
)
1060 return __mod_timer(timer
, expires
, true);
1062 EXPORT_SYMBOL(mod_timer_pending
);
1065 * mod_timer - modify a timer's timeout
1066 * @timer: the timer to be modified
1067 * @expires: new timeout in jiffies
1069 * mod_timer() is a more efficient way to update the expire field of an
1070 * active timer (if the timer is inactive it will be activated)
1072 * mod_timer(timer, expires) is equivalent to:
1074 * del_timer(timer); timer->expires = expires; add_timer(timer);
1076 * Note that if there are multiple unserialized concurrent users of the
1077 * same timer, then mod_timer() is the only safe way to modify the timeout,
1078 * since add_timer() cannot modify an already running timer.
1080 * The function returns whether it has modified a pending timer or not.
1081 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1082 * active timer returns 1.)
1084 int mod_timer(struct timer_list
*timer
, unsigned long expires
)
1086 return __mod_timer(timer
, expires
, false);
1088 EXPORT_SYMBOL(mod_timer
);
1091 * add_timer - start a timer
1092 * @timer: the timer to be added
1094 * The kernel will do a ->function(->data) callback from the
1095 * timer interrupt at the ->expires point in the future. The
1096 * current time is 'jiffies'.
1098 * The timer's ->expires, ->function (and if the handler uses it, ->data)
1099 * fields must be set prior calling this function.
1101 * Timers with an ->expires field in the past will be executed in the next
1104 void add_timer(struct timer_list
*timer
)
1106 BUG_ON(timer_pending(timer
));
1107 mod_timer(timer
, timer
->expires
);
1109 EXPORT_SYMBOL(add_timer
);
1112 * add_timer_on - start a timer on a particular CPU
1113 * @timer: the timer to be added
1114 * @cpu: the CPU to start it on
1116 * This is not very scalable on SMP. Double adds are not possible.
1118 void add_timer_on(struct timer_list
*timer
, int cpu
)
1120 struct timer_base
*new_base
, *base
;
1121 unsigned long flags
;
1123 timer_stats_timer_set_start_info(timer
);
1124 BUG_ON(timer_pending(timer
) || !timer
->function
);
1126 new_base
= get_timer_cpu_base(timer
->flags
, cpu
);
1129 * If @timer was on a different CPU, it should be migrated with the
1130 * old base locked to prevent other operations proceeding with the
1131 * wrong base locked. See lock_timer_base().
1133 base
= lock_timer_base(timer
, &flags
);
1134 if (base
!= new_base
) {
1135 timer
->flags
|= TIMER_MIGRATING
;
1137 spin_unlock(&base
->lock
);
1139 spin_lock(&base
->lock
);
1140 WRITE_ONCE(timer
->flags
,
1141 (timer
->flags
& ~TIMER_BASEMASK
) | cpu
);
1144 debug_activate(timer
, timer
->expires
);
1145 internal_add_timer(base
, timer
);
1146 spin_unlock_irqrestore(&base
->lock
, flags
);
1148 EXPORT_SYMBOL_GPL(add_timer_on
);
1151 * del_timer - deactive a timer.
1152 * @timer: the timer to be deactivated
1154 * del_timer() deactivates a timer - this works on both active and inactive
1157 * The function returns whether it has deactivated a pending timer or not.
1158 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1159 * active timer returns 1.)
1161 int del_timer(struct timer_list
*timer
)
1163 struct timer_base
*base
;
1164 unsigned long flags
;
1167 debug_assert_init(timer
);
1169 timer_stats_timer_clear_start_info(timer
);
1170 if (timer_pending(timer
)) {
1171 base
= lock_timer_base(timer
, &flags
);
1172 ret
= detach_if_pending(timer
, base
, true);
1173 spin_unlock_irqrestore(&base
->lock
, flags
);
1178 EXPORT_SYMBOL(del_timer
);
1181 * try_to_del_timer_sync - Try to deactivate a timer
1182 * @timer: timer do del
1184 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1185 * exit the timer is not queued and the handler is not running on any CPU.
1187 int try_to_del_timer_sync(struct timer_list
*timer
)
1189 struct timer_base
*base
;
1190 unsigned long flags
;
1193 debug_assert_init(timer
);
1195 base
= lock_timer_base(timer
, &flags
);
1197 if (base
->running_timer
!= timer
) {
1198 timer_stats_timer_clear_start_info(timer
);
1199 ret
= detach_if_pending(timer
, base
, true);
1201 spin_unlock_irqrestore(&base
->lock
, flags
);
1205 EXPORT_SYMBOL(try_to_del_timer_sync
);
1209 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1210 * @timer: the timer to be deactivated
1212 * This function only differs from del_timer() on SMP: besides deactivating
1213 * the timer it also makes sure the handler has finished executing on other
1216 * Synchronization rules: Callers must prevent restarting of the timer,
1217 * otherwise this function is meaningless. It must not be called from
1218 * interrupt contexts unless the timer is an irqsafe one. The caller must
1219 * not hold locks which would prevent completion of the timer's
1220 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1221 * timer is not queued and the handler is not running on any CPU.
1223 * Note: For !irqsafe timers, you must not hold locks that are held in
1224 * interrupt context while calling this function. Even if the lock has
1225 * nothing to do with the timer in question. Here's why:
1231 * base->running_timer = mytimer;
1232 * spin_lock_irq(somelock);
1234 * spin_lock(somelock);
1235 * del_timer_sync(mytimer);
1236 * while (base->running_timer == mytimer);
1238 * Now del_timer_sync() will never return and never release somelock.
1239 * The interrupt on the other CPU is waiting to grab somelock but
1240 * it has interrupted the softirq that CPU0 is waiting to finish.
1242 * The function returns whether it has deactivated a pending timer or not.
1244 int del_timer_sync(struct timer_list
*timer
)
1246 #ifdef CONFIG_LOCKDEP
1247 unsigned long flags
;
1250 * If lockdep gives a backtrace here, please reference
1251 * the synchronization rules above.
1253 local_irq_save(flags
);
1254 lock_map_acquire(&timer
->lockdep_map
);
1255 lock_map_release(&timer
->lockdep_map
);
1256 local_irq_restore(flags
);
1259 * don't use it in hardirq context, because it
1260 * could lead to deadlock.
1262 WARN_ON(in_irq() && !(timer
->flags
& TIMER_IRQSAFE
));
1264 int ret
= try_to_del_timer_sync(timer
);
1270 EXPORT_SYMBOL(del_timer_sync
);
1273 static void call_timer_fn(struct timer_list
*timer
, void (*fn
)(unsigned long),
1276 int count
= preempt_count();
1278 #ifdef CONFIG_LOCKDEP
1280 * It is permissible to free the timer from inside the
1281 * function that is called from it, this we need to take into
1282 * account for lockdep too. To avoid bogus "held lock freed"
1283 * warnings as well as problems when looking into
1284 * timer->lockdep_map, make a copy and use that here.
1286 struct lockdep_map lockdep_map
;
1288 lockdep_copy_map(&lockdep_map
, &timer
->lockdep_map
);
1291 * Couple the lock chain with the lock chain at
1292 * del_timer_sync() by acquiring the lock_map around the fn()
1293 * call here and in del_timer_sync().
1295 lock_map_acquire(&lockdep_map
);
1297 trace_timer_expire_entry(timer
);
1299 trace_timer_expire_exit(timer
);
1301 lock_map_release(&lockdep_map
);
1303 if (count
!= preempt_count()) {
1304 WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1305 fn
, count
, preempt_count());
1307 * Restore the preempt count. That gives us a decent
1308 * chance to survive and extract information. If the
1309 * callback kept a lock held, bad luck, but not worse
1310 * than the BUG() we had.
1312 preempt_count_set(count
);
1316 static void expire_timers(struct timer_base
*base
, struct hlist_head
*head
)
1318 while (!hlist_empty(head
)) {
1319 struct timer_list
*timer
;
1320 void (*fn
)(unsigned long);
1323 timer
= hlist_entry(head
->first
, struct timer_list
, entry
);
1324 timer_stats_account_timer(timer
);
1326 base
->running_timer
= timer
;
1327 detach_timer(timer
, true);
1329 fn
= timer
->function
;
1332 if (timer
->flags
& TIMER_IRQSAFE
) {
1333 spin_unlock(&base
->lock
);
1334 call_timer_fn(timer
, fn
, data
);
1335 spin_lock(&base
->lock
);
1337 spin_unlock_irq(&base
->lock
);
1338 call_timer_fn(timer
, fn
, data
);
1339 spin_lock_irq(&base
->lock
);
1344 static int __collect_expired_timers(struct timer_base
*base
,
1345 struct hlist_head
*heads
)
1347 unsigned long clk
= base
->clk
;
1348 struct hlist_head
*vec
;
1352 for (i
= 0; i
< LVL_DEPTH
; i
++) {
1353 idx
= (clk
& LVL_MASK
) + i
* LVL_SIZE
;
1355 if (__test_and_clear_bit(idx
, base
->pending_map
)) {
1356 vec
= base
->vectors
+ idx
;
1357 hlist_move_list(vec
, heads
++);
1360 /* Is it time to look at the next level? */
1361 if (clk
& LVL_CLK_MASK
)
1363 /* Shift clock for the next level granularity */
1364 clk
>>= LVL_CLK_SHIFT
;
1369 #ifdef CONFIG_NO_HZ_COMMON
1371 * Find the next pending bucket of a level. Search from level start (@offset)
1372 * + @clk upwards and if nothing there, search from start of the level
1373 * (@offset) up to @offset + clk.
1375 static int next_pending_bucket(struct timer_base
*base
, unsigned offset
,
1378 unsigned pos
, start
= offset
+ clk
;
1379 unsigned end
= offset
+ LVL_SIZE
;
1381 pos
= find_next_bit(base
->pending_map
, end
, start
);
1385 pos
= find_next_bit(base
->pending_map
, start
, offset
);
1386 return pos
< start
? pos
+ LVL_SIZE
- start
: -1;
1390 * Search the first expiring timer in the various clock levels. Caller must
1393 static unsigned long __next_timer_interrupt(struct timer_base
*base
)
1395 unsigned long clk
, next
, adj
;
1396 unsigned lvl
, offset
= 0;
1398 next
= base
->clk
+ NEXT_TIMER_MAX_DELTA
;
1400 for (lvl
= 0; lvl
< LVL_DEPTH
; lvl
++, offset
+= LVL_SIZE
) {
1401 int pos
= next_pending_bucket(base
, offset
, clk
& LVL_MASK
);
1404 unsigned long tmp
= clk
+ (unsigned long) pos
;
1406 tmp
<<= LVL_SHIFT(lvl
);
1407 if (time_before(tmp
, next
))
1411 * Clock for the next level. If the current level clock lower
1412 * bits are zero, we look at the next level as is. If not we
1413 * need to advance it by one because that's going to be the
1414 * next expiring bucket in that level. base->clk is the next
1415 * expiring jiffie. So in case of:
1417 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1420 * we have to look at all levels @index 0. With
1422 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1425 * LVL0 has the next expiring bucket @index 2. The upper
1426 * levels have the next expiring bucket @index 1.
1428 * In case that the propagation wraps the next level the same
1431 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1434 * So after looking at LVL0 we get:
1436 * LVL5 LVL4 LVL3 LVL2 LVL1
1439 * So no propagation from LVL1 to LVL2 because that happened
1440 * with the add already, but then we need to propagate further
1441 * from LVL2 to LVL3.
1443 * So the simple check whether the lower bits of the current
1444 * level are 0 or not is sufficient for all cases.
1446 adj
= clk
& LVL_CLK_MASK
? 1 : 0;
1447 clk
>>= LVL_CLK_SHIFT
;
1454 * Check, if the next hrtimer event is before the next timer wheel
1457 static u64
cmp_next_hrtimer_event(u64 basem
, u64 expires
)
1459 u64 nextevt
= hrtimer_get_next_event();
1462 * If high resolution timers are enabled
1463 * hrtimer_get_next_event() returns KTIME_MAX.
1465 if (expires
<= nextevt
)
1469 * If the next timer is already expired, return the tick base
1470 * time so the tick is fired immediately.
1472 if (nextevt
<= basem
)
1476 * Round up to the next jiffie. High resolution timers are
1477 * off, so the hrtimers are expired in the tick and we need to
1478 * make sure that this tick really expires the timer to avoid
1479 * a ping pong of the nohz stop code.
1481 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1483 return DIV_ROUND_UP_ULL(nextevt
, TICK_NSEC
) * TICK_NSEC
;
1487 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1488 * @basej: base time jiffies
1489 * @basem: base time clock monotonic
1491 * Returns the tick aligned clock monotonic time of the next pending
1492 * timer or KTIME_MAX if no timer is pending.
1494 u64
get_next_timer_interrupt(unsigned long basej
, u64 basem
)
1496 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1497 u64 expires
= KTIME_MAX
;
1498 unsigned long nextevt
;
1502 * Pretend that there is no timer pending if the cpu is offline.
1503 * Possible pending timers will be migrated later to an active cpu.
1505 if (cpu_is_offline(smp_processor_id()))
1508 spin_lock(&base
->lock
);
1509 nextevt
= __next_timer_interrupt(base
);
1510 is_max_delta
= (nextevt
== base
->clk
+ NEXT_TIMER_MAX_DELTA
);
1511 base
->next_expiry
= nextevt
;
1513 * We have a fresh next event. Check whether we can forward the base:
1515 if (time_after(nextevt
, jiffies
))
1516 base
->clk
= jiffies
;
1517 else if (time_after(nextevt
, base
->clk
))
1518 base
->clk
= nextevt
;
1520 if (time_before_eq(nextevt
, basej
)) {
1522 base
->is_idle
= false;
1525 expires
= basem
+ (nextevt
- basej
) * TICK_NSEC
;
1527 * If we expect to sleep more than a tick, mark the base idle:
1529 if ((expires
- basem
) > TICK_NSEC
)
1530 base
->is_idle
= true;
1532 spin_unlock(&base
->lock
);
1534 return cmp_next_hrtimer_event(basem
, expires
);
1538 * timer_clear_idle - Clear the idle state of the timer base
1540 * Called with interrupts disabled
1542 void timer_clear_idle(void)
1544 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1547 * We do this unlocked. The worst outcome is a remote enqueue sending
1548 * a pointless IPI, but taking the lock would just make the window for
1549 * sending the IPI a few instructions smaller for the cost of taking
1550 * the lock in the exit from idle path.
1552 base
->is_idle
= false;
1555 static int collect_expired_timers(struct timer_base
*base
,
1556 struct hlist_head
*heads
)
1559 * NOHZ optimization. After a long idle sleep we need to forward the
1560 * base to current jiffies. Avoid a loop by searching the bitfield for
1561 * the next expiring timer.
1563 if ((long)(jiffies
- base
->clk
) > 2) {
1564 unsigned long next
= __next_timer_interrupt(base
);
1567 * If the next timer is ahead of time forward to current
1568 * jiffies, otherwise forward to the next expiry time:
1570 if (time_after(next
, jiffies
)) {
1571 /* The call site will increment clock! */
1572 base
->clk
= jiffies
- 1;
1577 return __collect_expired_timers(base
, heads
);
1580 static inline int collect_expired_timers(struct timer_base
*base
,
1581 struct hlist_head
*heads
)
1583 return __collect_expired_timers(base
, heads
);
1588 * Called from the timer interrupt handler to charge one tick to the current
1589 * process. user_tick is 1 if the tick is user time, 0 for system.
1591 void update_process_times(int user_tick
)
1593 struct task_struct
*p
= current
;
1595 /* Note: this timer irq context must be accounted for as well. */
1596 account_process_tick(p
, user_tick
);
1598 rcu_check_callbacks(user_tick
);
1599 #ifdef CONFIG_IRQ_WORK
1604 run_posix_cpu_timers(p
);
1608 * __run_timers - run all expired timers (if any) on this CPU.
1609 * @base: the timer vector to be processed.
1611 static inline void __run_timers(struct timer_base
*base
)
1613 struct hlist_head heads
[LVL_DEPTH
];
1616 if (!time_after_eq(jiffies
, base
->clk
))
1619 spin_lock_irq(&base
->lock
);
1621 while (time_after_eq(jiffies
, base
->clk
)) {
1623 levels
= collect_expired_timers(base
, heads
);
1627 expire_timers(base
, heads
+ levels
);
1629 base
->running_timer
= NULL
;
1630 spin_unlock_irq(&base
->lock
);
1634 * This function runs timers and the timer-tq in bottom half context.
1636 static __latent_entropy
void run_timer_softirq(struct softirq_action
*h
)
1638 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1641 if (IS_ENABLED(CONFIG_NO_HZ_COMMON
) && base
->nohz_active
)
1642 __run_timers(this_cpu_ptr(&timer_bases
[BASE_DEF
]));
1646 * Called by the local, per-CPU timer interrupt on SMP.
1648 void run_local_timers(void)
1650 struct timer_base
*base
= this_cpu_ptr(&timer_bases
[BASE_STD
]);
1652 hrtimer_run_queues();
1653 /* Raise the softirq only if required. */
1654 if (time_before(jiffies
, base
->clk
)) {
1655 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON
) || !base
->nohz_active
)
1657 /* CPU is awake, so check the deferrable base. */
1659 if (time_before(jiffies
, base
->clk
))
1662 raise_softirq(TIMER_SOFTIRQ
);
1665 #ifdef __ARCH_WANT_SYS_ALARM
1668 * For backwards compatibility? This can be done in libc so Alpha
1669 * and all newer ports shouldn't need it.
1671 SYSCALL_DEFINE1(alarm
, unsigned int, seconds
)
1673 return alarm_setitimer(seconds
);
1678 static void process_timeout(unsigned long __data
)
1680 wake_up_process((struct task_struct
*)__data
);
1684 * schedule_timeout - sleep until timeout
1685 * @timeout: timeout value in jiffies
1687 * Make the current task sleep until @timeout jiffies have
1688 * elapsed. The routine will return immediately unless
1689 * the current task state has been set (see set_current_state()).
1691 * You can set the task state as follows -
1693 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1694 * pass before the routine returns. The routine will return 0
1696 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1697 * delivered to the current task. In this case the remaining time
1698 * in jiffies will be returned, or 0 if the timer expired in time
1700 * The current task state is guaranteed to be TASK_RUNNING when this
1703 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1704 * the CPU away without a bound on the timeout. In this case the return
1705 * value will be %MAX_SCHEDULE_TIMEOUT.
1707 * In all cases the return value is guaranteed to be non-negative.
1709 signed long __sched
schedule_timeout(signed long timeout
)
1711 struct timer_list timer
;
1712 unsigned long expire
;
1716 case MAX_SCHEDULE_TIMEOUT
:
1718 * These two special cases are useful to be comfortable
1719 * in the caller. Nothing more. We could take
1720 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1721 * but I' d like to return a valid offset (>=0) to allow
1722 * the caller to do everything it want with the retval.
1728 * Another bit of PARANOID. Note that the retval will be
1729 * 0 since no piece of kernel is supposed to do a check
1730 * for a negative retval of schedule_timeout() (since it
1731 * should never happens anyway). You just have the printk()
1732 * that will tell you if something is gone wrong and where.
1735 printk(KERN_ERR
"schedule_timeout: wrong timeout "
1736 "value %lx\n", timeout
);
1738 current
->state
= TASK_RUNNING
;
1743 expire
= timeout
+ jiffies
;
1745 setup_timer_on_stack(&timer
, process_timeout
, (unsigned long)current
);
1746 __mod_timer(&timer
, expire
, false);
1748 del_singleshot_timer_sync(&timer
);
1750 /* Remove the timer from the object tracker */
1751 destroy_timer_on_stack(&timer
);
1753 timeout
= expire
- jiffies
;
1756 return timeout
< 0 ? 0 : timeout
;
1758 EXPORT_SYMBOL(schedule_timeout
);
1761 * We can use __set_current_state() here because schedule_timeout() calls
1762 * schedule() unconditionally.
1764 signed long __sched
schedule_timeout_interruptible(signed long timeout
)
1766 __set_current_state(TASK_INTERRUPTIBLE
);
1767 return schedule_timeout(timeout
);
1769 EXPORT_SYMBOL(schedule_timeout_interruptible
);
1771 signed long __sched
schedule_timeout_killable(signed long timeout
)
1773 __set_current_state(TASK_KILLABLE
);
1774 return schedule_timeout(timeout
);
1776 EXPORT_SYMBOL(schedule_timeout_killable
);
1778 signed long __sched
schedule_timeout_uninterruptible(signed long timeout
)
1780 __set_current_state(TASK_UNINTERRUPTIBLE
);
1781 return schedule_timeout(timeout
);
1783 EXPORT_SYMBOL(schedule_timeout_uninterruptible
);
1786 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1789 signed long __sched
schedule_timeout_idle(signed long timeout
)
1791 __set_current_state(TASK_IDLE
);
1792 return schedule_timeout(timeout
);
1794 EXPORT_SYMBOL(schedule_timeout_idle
);
1796 #ifdef CONFIG_HOTPLUG_CPU
1797 static void migrate_timer_list(struct timer_base
*new_base
, struct hlist_head
*head
)
1799 struct timer_list
*timer
;
1800 int cpu
= new_base
->cpu
;
1802 while (!hlist_empty(head
)) {
1803 timer
= hlist_entry(head
->first
, struct timer_list
, entry
);
1804 detach_timer(timer
, false);
1805 timer
->flags
= (timer
->flags
& ~TIMER_BASEMASK
) | cpu
;
1806 internal_add_timer(new_base
, timer
);
1810 int timers_dead_cpu(unsigned int cpu
)
1812 struct timer_base
*old_base
;
1813 struct timer_base
*new_base
;
1816 BUG_ON(cpu_online(cpu
));
1818 for (b
= 0; b
< NR_BASES
; b
++) {
1819 old_base
= per_cpu_ptr(&timer_bases
[b
], cpu
);
1820 new_base
= get_cpu_ptr(&timer_bases
[b
]);
1822 * The caller is globally serialized and nobody else
1823 * takes two locks at once, deadlock is not possible.
1825 spin_lock_irq(&new_base
->lock
);
1826 spin_lock_nested(&old_base
->lock
, SINGLE_DEPTH_NESTING
);
1828 BUG_ON(old_base
->running_timer
);
1830 for (i
= 0; i
< WHEEL_SIZE
; i
++)
1831 migrate_timer_list(new_base
, old_base
->vectors
+ i
);
1833 spin_unlock(&old_base
->lock
);
1834 spin_unlock_irq(&new_base
->lock
);
1835 put_cpu_ptr(&timer_bases
);
1840 #endif /* CONFIG_HOTPLUG_CPU */
1842 static void __init
init_timer_cpu(int cpu
)
1844 struct timer_base
*base
;
1847 for (i
= 0; i
< NR_BASES
; i
++) {
1848 base
= per_cpu_ptr(&timer_bases
[i
], cpu
);
1850 spin_lock_init(&base
->lock
);
1851 base
->clk
= jiffies
;
1855 static void __init
init_timer_cpus(void)
1859 for_each_possible_cpu(cpu
)
1860 init_timer_cpu(cpu
);
1863 void __init
init_timers(void)
1867 open_softirq(TIMER_SOFTIRQ
, run_timer_softirq
);
1871 * msleep - sleep safely even with waitqueue interruptions
1872 * @msecs: Time in milliseconds to sleep for
1874 void msleep(unsigned int msecs
)
1876 unsigned long timeout
= msecs_to_jiffies(msecs
) + 1;
1879 timeout
= schedule_timeout_uninterruptible(timeout
);
1882 EXPORT_SYMBOL(msleep
);
1885 * msleep_interruptible - sleep waiting for signals
1886 * @msecs: Time in milliseconds to sleep for
1888 unsigned long msleep_interruptible(unsigned int msecs
)
1890 unsigned long timeout
= msecs_to_jiffies(msecs
) + 1;
1892 while (timeout
&& !signal_pending(current
))
1893 timeout
= schedule_timeout_interruptible(timeout
);
1894 return jiffies_to_msecs(timeout
);
1897 EXPORT_SYMBOL(msleep_interruptible
);
1899 static void __sched
do_usleep_range(unsigned long min
, unsigned long max
)
1904 kmin
= ktime_set(0, min
* NSEC_PER_USEC
);
1905 delta
= (u64
)(max
- min
) * NSEC_PER_USEC
;
1906 schedule_hrtimeout_range(&kmin
, delta
, HRTIMER_MODE_REL
);
1910 * usleep_range - Sleep for an approximate time
1911 * @min: Minimum time in usecs to sleep
1912 * @max: Maximum time in usecs to sleep
1914 * In non-atomic context where the exact wakeup time is flexible, use
1915 * usleep_range() instead of udelay(). The sleep improves responsiveness
1916 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
1917 * power usage by allowing hrtimers to take advantage of an already-
1918 * scheduled interrupt instead of scheduling a new one just for this sleep.
1920 void __sched
usleep_range(unsigned long min
, unsigned long max
)
1922 __set_current_state(TASK_UNINTERRUPTIBLE
);
1923 do_usleep_range(min
, max
);
1925 EXPORT_SYMBOL(usleep_range
);