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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Kernel internal timers
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
8 *
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
19 */
20
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>
26#include <linux/mm.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>
46
47#include <linux/uaccess.h>
48#include <asm/unistd.h>
49#include <asm/div64.h>
50#include <asm/timex.h>
51#include <asm/io.h>
52
53#include "tick-internal.h"
54
55#define CREATE_TRACE_POINTS
56#include <trace/events/timer.h>
57
58__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
59
60EXPORT_SYMBOL(jiffies_64);
61
62/*
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.
66 *
67 * The level granularity is: LVL_CLK_DIV ^ lvl
68 * The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
69 *
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.
73 *
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.
80 *
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.
86 *
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.
90 *
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
95 * be an issue.
96 *
97 * The currently chosen array constants values are a good compromise between
98 * array size and granularity.
99 *
100 * This results in the following granularity and range levels:
101 *
102 * HZ 1000 steps
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)
113 *
114 * HZ 300
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)
125 *
126 * HZ 250
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)
137 *
138 * HZ 100
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)
148 */
149
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))
156
157/*
158 * The time start value for each level to select the bucket at enqueue
159 * time.
160 */
161#define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
162
163/* Size of each clock level */
164#define LVL_BITS 6
165#define LVL_SIZE (1UL << LVL_BITS)
166#define LVL_MASK (LVL_SIZE - 1)
167#define LVL_OFFS(n) ((n) * LVL_SIZE)
168
169/* Level depth */
170#if HZ > 100
171# define LVL_DEPTH 9
172# else
173# define LVL_DEPTH 8
174#endif
175
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))
179
180/*
181 * The resulting wheel size. If NOHZ is configured we allocate two
182 * wheels so we have a separate storage for the deferrable timers.
183 */
184#define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
185
186#ifdef CONFIG_NO_HZ_COMMON
187# define NR_BASES 2
188# define BASE_STD 0
189# define BASE_DEF 1
190#else
191# define NR_BASES 1
192# define BASE_STD 0
193# define BASE_DEF 0
194#endif
195
196struct timer_base {
197 raw_spinlock_t lock;
198 struct timer_list *running_timer;
199#ifdef CONFIG_PREEMPT_RT
200 spinlock_t expiry_lock;
201 atomic_t timer_waiters;
202#endif
203 unsigned long clk;
204 unsigned long next_expiry;
205 unsigned int cpu;
206 bool is_idle;
207 bool must_forward_clk;
208 DECLARE_BITMAP(pending_map, WHEEL_SIZE);
209 struct hlist_head vectors[WHEEL_SIZE];
210} ____cacheline_aligned;
211
212static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
213
214#ifdef CONFIG_NO_HZ_COMMON
215
216static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
217static DEFINE_MUTEX(timer_keys_mutex);
218
219static void timer_update_keys(struct work_struct *work);
220static DECLARE_WORK(timer_update_work, timer_update_keys);
221
222#ifdef CONFIG_SMP
223unsigned int sysctl_timer_migration = 1;
224
225DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
226
227static void timers_update_migration(void)
228{
229 if (sysctl_timer_migration && tick_nohz_active)
230 static_branch_enable(&timers_migration_enabled);
231 else
232 static_branch_disable(&timers_migration_enabled);
233}
234#else
235static inline void timers_update_migration(void) { }
236#endif /* !CONFIG_SMP */
237
238static void timer_update_keys(struct work_struct *work)
239{
240 mutex_lock(&timer_keys_mutex);
241 timers_update_migration();
242 static_branch_enable(&timers_nohz_active);
243 mutex_unlock(&timer_keys_mutex);
244}
245
246void timers_update_nohz(void)
247{
248 schedule_work(&timer_update_work);
249}
250
251int timer_migration_handler(struct ctl_table *table, int write,
252 void __user *buffer, size_t *lenp,
253 loff_t *ppos)
254{
255 int ret;
256
257 mutex_lock(&timer_keys_mutex);
258 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
259 if (!ret && write)
260 timers_update_migration();
261 mutex_unlock(&timer_keys_mutex);
262 return ret;
263}
264
265static inline bool is_timers_nohz_active(void)
266{
267 return static_branch_unlikely(&timers_nohz_active);
268}
269#else
270static inline bool is_timers_nohz_active(void) { return false; }
271#endif /* NO_HZ_COMMON */
272
273static unsigned long round_jiffies_common(unsigned long j, int cpu,
274 bool force_up)
275{
276 int rem;
277 unsigned long original = j;
278
279 /*
280 * We don't want all cpus firing their timers at once hitting the
281 * same lock or cachelines, so we skew each extra cpu with an extra
282 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
283 * already did this.
284 * The skew is done by adding 3*cpunr, then round, then subtract this
285 * extra offset again.
286 */
287 j += cpu * 3;
288
289 rem = j % HZ;
290
291 /*
292 * If the target jiffie is just after a whole second (which can happen
293 * due to delays of the timer irq, long irq off times etc etc) then
294 * we should round down to the whole second, not up. Use 1/4th second
295 * as cutoff for this rounding as an extreme upper bound for this.
296 * But never round down if @force_up is set.
297 */
298 if (rem < HZ/4 && !force_up) /* round down */
299 j = j - rem;
300 else /* round up */
301 j = j - rem + HZ;
302
303 /* now that we have rounded, subtract the extra skew again */
304 j -= cpu * 3;
305
306 /*
307 * Make sure j is still in the future. Otherwise return the
308 * unmodified value.
309 */
310 return time_is_after_jiffies(j) ? j : original;
311}
312
313/**
314 * __round_jiffies - function to round jiffies to a full second
315 * @j: the time in (absolute) jiffies that should be rounded
316 * @cpu: the processor number on which the timeout will happen
317 *
318 * __round_jiffies() rounds an absolute time in the future (in jiffies)
319 * up or down to (approximately) full seconds. This is useful for timers
320 * for which the exact time they fire does not matter too much, as long as
321 * they fire approximately every X seconds.
322 *
323 * By rounding these timers to whole seconds, all such timers will fire
324 * at the same time, rather than at various times spread out. The goal
325 * of this is to have the CPU wake up less, which saves power.
326 *
327 * The exact rounding is skewed for each processor to avoid all
328 * processors firing at the exact same time, which could lead
329 * to lock contention or spurious cache line bouncing.
330 *
331 * The return value is the rounded version of the @j parameter.
332 */
333unsigned long __round_jiffies(unsigned long j, int cpu)
334{
335 return round_jiffies_common(j, cpu, false);
336}
337EXPORT_SYMBOL_GPL(__round_jiffies);
338
339/**
340 * __round_jiffies_relative - function to round jiffies to a full second
341 * @j: the time in (relative) jiffies that should be rounded
342 * @cpu: the processor number on which the timeout will happen
343 *
344 * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
345 * up or down to (approximately) full seconds. This is useful for timers
346 * for which the exact time they fire does not matter too much, as long as
347 * they fire approximately every X seconds.
348 *
349 * By rounding these timers to whole seconds, all such timers will fire
350 * at the same time, rather than at various times spread out. The goal
351 * of this is to have the CPU wake up less, which saves power.
352 *
353 * The exact rounding is skewed for each processor to avoid all
354 * processors firing at the exact same time, which could lead
355 * to lock contention or spurious cache line bouncing.
356 *
357 * The return value is the rounded version of the @j parameter.
358 */
359unsigned long __round_jiffies_relative(unsigned long j, int cpu)
360{
361 unsigned long j0 = jiffies;
362
363 /* Use j0 because jiffies might change while we run */
364 return round_jiffies_common(j + j0, cpu, false) - j0;
365}
366EXPORT_SYMBOL_GPL(__round_jiffies_relative);
367
368/**
369 * round_jiffies - function to round jiffies to a full second
370 * @j: the time in (absolute) jiffies that should be rounded
371 *
372 * round_jiffies() rounds an absolute time in the future (in jiffies)
373 * up or down to (approximately) full seconds. This is useful for timers
374 * for which the exact time they fire does not matter too much, as long as
375 * they fire approximately every X seconds.
376 *
377 * By rounding these timers to whole seconds, all such timers will fire
378 * at the same time, rather than at various times spread out. The goal
379 * of this is to have the CPU wake up less, which saves power.
380 *
381 * The return value is the rounded version of the @j parameter.
382 */
383unsigned long round_jiffies(unsigned long j)
384{
385 return round_jiffies_common(j, raw_smp_processor_id(), false);
386}
387EXPORT_SYMBOL_GPL(round_jiffies);
388
389/**
390 * round_jiffies_relative - function to round jiffies to a full second
391 * @j: the time in (relative) jiffies that should be rounded
392 *
393 * round_jiffies_relative() rounds a time delta in the future (in jiffies)
394 * up or down to (approximately) full seconds. This is useful for timers
395 * for which the exact time they fire does not matter too much, as long as
396 * they fire approximately every X seconds.
397 *
398 * By rounding these timers to whole seconds, all such timers will fire
399 * at the same time, rather than at various times spread out. The goal
400 * of this is to have the CPU wake up less, which saves power.
401 *
402 * The return value is the rounded version of the @j parameter.
403 */
404unsigned long round_jiffies_relative(unsigned long j)
405{
406 return __round_jiffies_relative(j, raw_smp_processor_id());
407}
408EXPORT_SYMBOL_GPL(round_jiffies_relative);
409
410/**
411 * __round_jiffies_up - function to round jiffies up to a full second
412 * @j: the time in (absolute) jiffies that should be rounded
413 * @cpu: the processor number on which the timeout will happen
414 *
415 * This is the same as __round_jiffies() except that it will never
416 * round down. This is useful for timeouts for which the exact time
417 * of firing does not matter too much, as long as they don't fire too
418 * early.
419 */
420unsigned long __round_jiffies_up(unsigned long j, int cpu)
421{
422 return round_jiffies_common(j, cpu, true);
423}
424EXPORT_SYMBOL_GPL(__round_jiffies_up);
425
426/**
427 * __round_jiffies_up_relative - function to round jiffies up to a full second
428 * @j: the time in (relative) jiffies that should be rounded
429 * @cpu: the processor number on which the timeout will happen
430 *
431 * This is the same as __round_jiffies_relative() except that it will never
432 * round down. This is useful for timeouts for which the exact time
433 * of firing does not matter too much, as long as they don't fire too
434 * early.
435 */
436unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
437{
438 unsigned long j0 = jiffies;
439
440 /* Use j0 because jiffies might change while we run */
441 return round_jiffies_common(j + j0, cpu, true) - j0;
442}
443EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
444
445/**
446 * round_jiffies_up - function to round jiffies up to a full second
447 * @j: the time in (absolute) jiffies that should be rounded
448 *
449 * This is the same as round_jiffies() except that it will never
450 * round down. This is useful for timeouts for which the exact time
451 * of firing does not matter too much, as long as they don't fire too
452 * early.
453 */
454unsigned long round_jiffies_up(unsigned long j)
455{
456 return round_jiffies_common(j, raw_smp_processor_id(), true);
457}
458EXPORT_SYMBOL_GPL(round_jiffies_up);
459
460/**
461 * round_jiffies_up_relative - function to round jiffies up to a full second
462 * @j: the time in (relative) jiffies that should be rounded
463 *
464 * This is the same as round_jiffies_relative() except that it will never
465 * round down. This is useful for timeouts for which the exact time
466 * of firing does not matter too much, as long as they don't fire too
467 * early.
468 */
469unsigned long round_jiffies_up_relative(unsigned long j)
470{
471 return __round_jiffies_up_relative(j, raw_smp_processor_id());
472}
473EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
474
475
476static inline unsigned int timer_get_idx(struct timer_list *timer)
477{
478 return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
479}
480
481static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
482{
483 timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
484 idx << TIMER_ARRAYSHIFT;
485}
486
487/*
488 * Helper function to calculate the array index for a given expiry
489 * time.
490 */
491static inline unsigned calc_index(unsigned expires, unsigned lvl)
492{
493 expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
494 return LVL_OFFS(lvl) + (expires & LVL_MASK);
495}
496
497static int calc_wheel_index(unsigned long expires, unsigned long clk)
498{
499 unsigned long delta = expires - clk;
500 unsigned int idx;
501
502 if (delta < LVL_START(1)) {
503 idx = calc_index(expires, 0);
504 } else if (delta < LVL_START(2)) {
505 idx = calc_index(expires, 1);
506 } else if (delta < LVL_START(3)) {
507 idx = calc_index(expires, 2);
508 } else if (delta < LVL_START(4)) {
509 idx = calc_index(expires, 3);
510 } else if (delta < LVL_START(5)) {
511 idx = calc_index(expires, 4);
512 } else if (delta < LVL_START(6)) {
513 idx = calc_index(expires, 5);
514 } else if (delta < LVL_START(7)) {
515 idx = calc_index(expires, 6);
516 } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
517 idx = calc_index(expires, 7);
518 } else if ((long) delta < 0) {
519 idx = clk & LVL_MASK;
520 } else {
521 /*
522 * Force expire obscene large timeouts to expire at the
523 * capacity limit of the wheel.
524 */
525 if (expires >= WHEEL_TIMEOUT_CUTOFF)
526 expires = WHEEL_TIMEOUT_MAX;
527
528 idx = calc_index(expires, LVL_DEPTH - 1);
529 }
530 return idx;
531}
532
533/*
534 * Enqueue the timer into the hash bucket, mark it pending in
535 * the bitmap and store the index in the timer flags.
536 */
537static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
538 unsigned int idx)
539{
540 hlist_add_head(&timer->entry, base->vectors + idx);
541 __set_bit(idx, base->pending_map);
542 timer_set_idx(timer, idx);
543
544 trace_timer_start(timer, timer->expires, timer->flags);
545}
546
547static void
548__internal_add_timer(struct timer_base *base, struct timer_list *timer)
549{
550 unsigned int idx;
551
552 idx = calc_wheel_index(timer->expires, base->clk);
553 enqueue_timer(base, timer, idx);
554}
555
556static void
557trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
558{
559 if (!is_timers_nohz_active())
560 return;
561
562 /*
563 * TODO: This wants some optimizing similar to the code below, but we
564 * will do that when we switch from push to pull for deferrable timers.
565 */
566 if (timer->flags & TIMER_DEFERRABLE) {
567 if (tick_nohz_full_cpu(base->cpu))
568 wake_up_nohz_cpu(base->cpu);
569 return;
570 }
571
572 /*
573 * We might have to IPI the remote CPU if the base is idle and the
574 * timer is not deferrable. If the other CPU is on the way to idle
575 * then it can't set base->is_idle as we hold the base lock:
576 */
577 if (!base->is_idle)
578 return;
579
580 /* Check whether this is the new first expiring timer: */
581 if (time_after_eq(timer->expires, base->next_expiry))
582 return;
583
584 /*
585 * Set the next expiry time and kick the CPU so it can reevaluate the
586 * wheel:
587 */
588 base->next_expiry = timer->expires;
589 wake_up_nohz_cpu(base->cpu);
590}
591
592static void
593internal_add_timer(struct timer_base *base, struct timer_list *timer)
594{
595 __internal_add_timer(base, timer);
596 trigger_dyntick_cpu(base, timer);
597}
598
599#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
600
601static struct debug_obj_descr timer_debug_descr;
602
603static void *timer_debug_hint(void *addr)
604{
605 return ((struct timer_list *) addr)->function;
606}
607
608static bool timer_is_static_object(void *addr)
609{
610 struct timer_list *timer = addr;
611
612 return (timer->entry.pprev == NULL &&
613 timer->entry.next == TIMER_ENTRY_STATIC);
614}
615
616/*
617 * fixup_init is called when:
618 * - an active object is initialized
619 */
620static bool timer_fixup_init(void *addr, enum debug_obj_state state)
621{
622 struct timer_list *timer = addr;
623
624 switch (state) {
625 case ODEBUG_STATE_ACTIVE:
626 del_timer_sync(timer);
627 debug_object_init(timer, &timer_debug_descr);
628 return true;
629 default:
630 return false;
631 }
632}
633
634/* Stub timer callback for improperly used timers. */
635static void stub_timer(struct timer_list *unused)
636{
637 WARN_ON(1);
638}
639
640/*
641 * fixup_activate is called when:
642 * - an active object is activated
643 * - an unknown non-static object is activated
644 */
645static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
646{
647 struct timer_list *timer = addr;
648
649 switch (state) {
650 case ODEBUG_STATE_NOTAVAILABLE:
651 timer_setup(timer, stub_timer, 0);
652 return true;
653
654 case ODEBUG_STATE_ACTIVE:
655 WARN_ON(1);
656 /* fall through */
657 default:
658 return false;
659 }
660}
661
662/*
663 * fixup_free is called when:
664 * - an active object is freed
665 */
666static bool timer_fixup_free(void *addr, enum debug_obj_state state)
667{
668 struct timer_list *timer = addr;
669
670 switch (state) {
671 case ODEBUG_STATE_ACTIVE:
672 del_timer_sync(timer);
673 debug_object_free(timer, &timer_debug_descr);
674 return true;
675 default:
676 return false;
677 }
678}
679
680/*
681 * fixup_assert_init is called when:
682 * - an untracked/uninit-ed object is found
683 */
684static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
685{
686 struct timer_list *timer = addr;
687
688 switch (state) {
689 case ODEBUG_STATE_NOTAVAILABLE:
690 timer_setup(timer, stub_timer, 0);
691 return true;
692 default:
693 return false;
694 }
695}
696
697static struct debug_obj_descr timer_debug_descr = {
698 .name = "timer_list",
699 .debug_hint = timer_debug_hint,
700 .is_static_object = timer_is_static_object,
701 .fixup_init = timer_fixup_init,
702 .fixup_activate = timer_fixup_activate,
703 .fixup_free = timer_fixup_free,
704 .fixup_assert_init = timer_fixup_assert_init,
705};
706
707static inline void debug_timer_init(struct timer_list *timer)
708{
709 debug_object_init(timer, &timer_debug_descr);
710}
711
712static inline void debug_timer_activate(struct timer_list *timer)
713{
714 debug_object_activate(timer, &timer_debug_descr);
715}
716
717static inline void debug_timer_deactivate(struct timer_list *timer)
718{
719 debug_object_deactivate(timer, &timer_debug_descr);
720}
721
722static inline void debug_timer_free(struct timer_list *timer)
723{
724 debug_object_free(timer, &timer_debug_descr);
725}
726
727static inline void debug_timer_assert_init(struct timer_list *timer)
728{
729 debug_object_assert_init(timer, &timer_debug_descr);
730}
731
732static void do_init_timer(struct timer_list *timer,
733 void (*func)(struct timer_list *),
734 unsigned int flags,
735 const char *name, struct lock_class_key *key);
736
737void init_timer_on_stack_key(struct timer_list *timer,
738 void (*func)(struct timer_list *),
739 unsigned int flags,
740 const char *name, struct lock_class_key *key)
741{
742 debug_object_init_on_stack(timer, &timer_debug_descr);
743 do_init_timer(timer, func, flags, name, key);
744}
745EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
746
747void destroy_timer_on_stack(struct timer_list *timer)
748{
749 debug_object_free(timer, &timer_debug_descr);
750}
751EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
752
753#else
754static inline void debug_timer_init(struct timer_list *timer) { }
755static inline void debug_timer_activate(struct timer_list *timer) { }
756static inline void debug_timer_deactivate(struct timer_list *timer) { }
757static inline void debug_timer_assert_init(struct timer_list *timer) { }
758#endif
759
760static inline void debug_init(struct timer_list *timer)
761{
762 debug_timer_init(timer);
763 trace_timer_init(timer);
764}
765
766static inline void debug_deactivate(struct timer_list *timer)
767{
768 debug_timer_deactivate(timer);
769 trace_timer_cancel(timer);
770}
771
772static inline void debug_assert_init(struct timer_list *timer)
773{
774 debug_timer_assert_init(timer);
775}
776
777static void do_init_timer(struct timer_list *timer,
778 void (*func)(struct timer_list *),
779 unsigned int flags,
780 const char *name, struct lock_class_key *key)
781{
782 timer->entry.pprev = NULL;
783 timer->function = func;
784 timer->flags = flags | raw_smp_processor_id();
785 lockdep_init_map(&timer->lockdep_map, name, key, 0);
786}
787
788/**
789 * init_timer_key - initialize a timer
790 * @timer: the timer to be initialized
791 * @func: timer callback function
792 * @flags: timer flags
793 * @name: name of the timer
794 * @key: lockdep class key of the fake lock used for tracking timer
795 * sync lock dependencies
796 *
797 * init_timer_key() must be done to a timer prior calling *any* of the
798 * other timer functions.
799 */
800void init_timer_key(struct timer_list *timer,
801 void (*func)(struct timer_list *), unsigned int flags,
802 const char *name, struct lock_class_key *key)
803{
804 debug_init(timer);
805 do_init_timer(timer, func, flags, name, key);
806}
807EXPORT_SYMBOL(init_timer_key);
808
809static inline void detach_timer(struct timer_list *timer, bool clear_pending)
810{
811 struct hlist_node *entry = &timer->entry;
812
813 debug_deactivate(timer);
814
815 __hlist_del(entry);
816 if (clear_pending)
817 entry->pprev = NULL;
818 entry->next = LIST_POISON2;
819}
820
821static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
822 bool clear_pending)
823{
824 unsigned idx = timer_get_idx(timer);
825
826 if (!timer_pending(timer))
827 return 0;
828
829 if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
830 __clear_bit(idx, base->pending_map);
831
832 detach_timer(timer, clear_pending);
833 return 1;
834}
835
836static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
837{
838 struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
839
840 /*
841 * If the timer is deferrable and NO_HZ_COMMON is set then we need
842 * to use the deferrable base.
843 */
844 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
845 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
846 return base;
847}
848
849static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
850{
851 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
852
853 /*
854 * If the timer is deferrable and NO_HZ_COMMON is set then we need
855 * to use the deferrable base.
856 */
857 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
858 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
859 return base;
860}
861
862static inline struct timer_base *get_timer_base(u32 tflags)
863{
864 return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
865}
866
867static inline struct timer_base *
868get_target_base(struct timer_base *base, unsigned tflags)
869{
870#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
871 if (static_branch_likely(&timers_migration_enabled) &&
872 !(tflags & TIMER_PINNED))
873 return get_timer_cpu_base(tflags, get_nohz_timer_target());
874#endif
875 return get_timer_this_cpu_base(tflags);
876}
877
878static inline void forward_timer_base(struct timer_base *base)
879{
880#ifdef CONFIG_NO_HZ_COMMON
881 unsigned long jnow;
882
883 /*
884 * We only forward the base when we are idle or have just come out of
885 * idle (must_forward_clk logic), and have a delta between base clock
886 * and jiffies. In the common case, run_timers will take care of it.
887 */
888 if (likely(!base->must_forward_clk))
889 return;
890
891 jnow = READ_ONCE(jiffies);
892 base->must_forward_clk = base->is_idle;
893 if ((long)(jnow - base->clk) < 2)
894 return;
895
896 /*
897 * If the next expiry value is > jiffies, then we fast forward to
898 * jiffies otherwise we forward to the next expiry value.
899 */
900 if (time_after(base->next_expiry, jnow))
901 base->clk = jnow;
902 else
903 base->clk = base->next_expiry;
904#endif
905}
906
907
908/*
909 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
910 * that all timers which are tied to this base are locked, and the base itself
911 * is locked too.
912 *
913 * So __run_timers/migrate_timers can safely modify all timers which could
914 * be found in the base->vectors array.
915 *
916 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
917 * to wait until the migration is done.
918 */
919static struct timer_base *lock_timer_base(struct timer_list *timer,
920 unsigned long *flags)
921 __acquires(timer->base->lock)
922{
923 for (;;) {
924 struct timer_base *base;
925 u32 tf;
926
927 /*
928 * We need to use READ_ONCE() here, otherwise the compiler
929 * might re-read @tf between the check for TIMER_MIGRATING
930 * and spin_lock().
931 */
932 tf = READ_ONCE(timer->flags);
933
934 if (!(tf & TIMER_MIGRATING)) {
935 base = get_timer_base(tf);
936 raw_spin_lock_irqsave(&base->lock, *flags);
937 if (timer->flags == tf)
938 return base;
939 raw_spin_unlock_irqrestore(&base->lock, *flags);
940 }
941 cpu_relax();
942 }
943}
944
945#define MOD_TIMER_PENDING_ONLY 0x01
946#define MOD_TIMER_REDUCE 0x02
947#define MOD_TIMER_NOTPENDING 0x04
948
949static inline int
950__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
951{
952 struct timer_base *base, *new_base;
953 unsigned int idx = UINT_MAX;
954 unsigned long clk = 0, flags;
955 int ret = 0;
956
957 BUG_ON(!timer->function);
958
959 /*
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:
963 */
964 if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
965 /*
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.
969 */
970 long diff = timer->expires - expires;
971
972 if (!diff)
973 return 1;
974 if (options & MOD_TIMER_REDUCE && diff <= 0)
975 return 1;
976
977 /*
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.
982 */
983 base = lock_timer_base(timer, &flags);
984 forward_timer_base(base);
985
986 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
987 time_before_eq(timer->expires, expires)) {
988 ret = 1;
989 goto out_unlock;
990 }
991
992 clk = base->clk;
993 idx = calc_wheel_index(expires, clk);
994
995 /*
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.
999 */
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;
1005 ret = 1;
1006 goto out_unlock;
1007 }
1008 } else {
1009 base = lock_timer_base(timer, &flags);
1010 forward_timer_base(base);
1011 }
1012
1013 ret = detach_if_pending(timer, base, false);
1014 if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1015 goto out_unlock;
1016
1017 new_base = get_target_base(base, timer->flags);
1018
1019 if (base != new_base) {
1020 /*
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.
1026 */
1027 if (likely(base->running_timer != timer)) {
1028 /* See the comment in lock_timer_base() */
1029 timer->flags |= TIMER_MIGRATING;
1030
1031 raw_spin_unlock(&base->lock);
1032 base = new_base;
1033 raw_spin_lock(&base->lock);
1034 WRITE_ONCE(timer->flags,
1035 (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1036 forward_timer_base(base);
1037 }
1038 }
1039
1040 debug_timer_activate(timer);
1041
1042 timer->expires = expires;
1043 /*
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().
1049 */
1050 if (idx != UINT_MAX && clk == base->clk) {
1051 enqueue_timer(base, timer, idx);
1052 trigger_dyntick_cpu(base, timer);
1053 } else {
1054 internal_add_timer(base, timer);
1055 }
1056
1057out_unlock:
1058 raw_spin_unlock_irqrestore(&base->lock, flags);
1059
1060 return ret;
1061}
1062
1063/**
1064 * mod_timer_pending - modify a pending timer's timeout
1065 * @timer: the pending timer to be modified
1066 * @expires: new timeout in jiffies
1067 *
1068 * mod_timer_pending() is the same for pending timers as mod_timer(),
1069 * but will not re-activate and modify already deleted timers.
1070 *
1071 * It is useful for unserialized use of timers.
1072 */
1073int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1074{
1075 return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1076}
1077EXPORT_SYMBOL(mod_timer_pending);
1078
1079/**
1080 * mod_timer - modify a timer's timeout
1081 * @timer: the timer to be modified
1082 * @expires: new timeout in jiffies
1083 *
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)
1086 *
1087 * mod_timer(timer, expires) is equivalent to:
1088 *
1089 * del_timer(timer); timer->expires = expires; add_timer(timer);
1090 *
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.
1094 *
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.)
1098 */
1099int mod_timer(struct timer_list *timer, unsigned long expires)
1100{
1101 return __mod_timer(timer, expires, 0);
1102}
1103EXPORT_SYMBOL(mod_timer);
1104
1105/**
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
1109 *
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).
1113 */
1114int timer_reduce(struct timer_list *timer, unsigned long expires)
1115{
1116 return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1117}
1118EXPORT_SYMBOL(timer_reduce);
1119
1120/**
1121 * add_timer - start a timer
1122 * @timer: the timer to be added
1123 *
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'.
1127 *
1128 * The timer's ->expires, ->function fields must be set prior calling this
1129 * function.
1130 *
1131 * Timers with an ->expires field in the past will be executed in the next
1132 * timer tick.
1133 */
1134void add_timer(struct timer_list *timer)
1135{
1136 BUG_ON(timer_pending(timer));
1137 __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1138}
1139EXPORT_SYMBOL(add_timer);
1140
1141/**
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
1145 *
1146 * This is not very scalable on SMP. Double adds are not possible.
1147 */
1148void add_timer_on(struct timer_list *timer, int cpu)
1149{
1150 struct timer_base *new_base, *base;
1151 unsigned long flags;
1152
1153 BUG_ON(timer_pending(timer) || !timer->function);
1154
1155 new_base = get_timer_cpu_base(timer->flags, cpu);
1156
1157 /*
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().
1161 */
1162 base = lock_timer_base(timer, &flags);
1163 if (base != new_base) {
1164 timer->flags |= TIMER_MIGRATING;
1165
1166 raw_spin_unlock(&base->lock);
1167 base = new_base;
1168 raw_spin_lock(&base->lock);
1169 WRITE_ONCE(timer->flags,
1170 (timer->flags & ~TIMER_BASEMASK) | cpu);
1171 }
1172 forward_timer_base(base);
1173
1174 debug_timer_activate(timer);
1175 internal_add_timer(base, timer);
1176 raw_spin_unlock_irqrestore(&base->lock, flags);
1177}
1178EXPORT_SYMBOL_GPL(add_timer_on);
1179
1180/**
1181 * del_timer - deactivate a timer.
1182 * @timer: the timer to be deactivated
1183 *
1184 * del_timer() deactivates a timer - this works on both active and inactive
1185 * timers.
1186 *
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.)
1190 */
1191int del_timer(struct timer_list *timer)
1192{
1193 struct timer_base *base;
1194 unsigned long flags;
1195 int ret = 0;
1196
1197 debug_assert_init(timer);
1198
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);
1203 }
1204
1205 return ret;
1206}
1207EXPORT_SYMBOL(del_timer);
1208
1209/**
1210 * try_to_del_timer_sync - Try to deactivate a timer
1211 * @timer: timer to delete
1212 *
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.
1215 */
1216int try_to_del_timer_sync(struct timer_list *timer)
1217{
1218 struct timer_base *base;
1219 unsigned long flags;
1220 int ret = -1;
1221
1222 debug_assert_init(timer);
1223
1224 base = lock_timer_base(timer, &flags);
1225
1226 if (base->running_timer != timer)
1227 ret = detach_if_pending(timer, base, true);
1228
1229 raw_spin_unlock_irqrestore(&base->lock, flags);
1230
1231 return ret;
1232}
1233EXPORT_SYMBOL(try_to_del_timer_sync);
1234
1235#ifdef CONFIG_PREEMPT_RT
1236static __init void timer_base_init_expiry_lock(struct timer_base *base)
1237{
1238 spin_lock_init(&base->expiry_lock);
1239}
1240
1241static inline void timer_base_lock_expiry(struct timer_base *base)
1242{
1243 spin_lock(&base->expiry_lock);
1244}
1245
1246static inline void timer_base_unlock_expiry(struct timer_base *base)
1247{
1248 spin_unlock(&base->expiry_lock);
1249}
1250
1251/*
1252 * The counterpart to del_timer_wait_running().
1253 *
1254 * If there is a waiter for base->expiry_lock, then it was waiting for the
1255 * timer callback to finish. Drop expiry_lock and reaquire it. That allows
1256 * the waiter to acquire the lock and make progress.
1257 */
1258static void timer_sync_wait_running(struct timer_base *base)
1259{
1260 if (atomic_read(&base->timer_waiters)) {
1261 spin_unlock(&base->expiry_lock);
1262 spin_lock(&base->expiry_lock);
1263 }
1264}
1265
1266/*
1267 * This function is called on PREEMPT_RT kernels when the fast path
1268 * deletion of a timer failed because the timer callback function was
1269 * running.
1270 *
1271 * This prevents priority inversion, if the softirq thread on a remote CPU
1272 * got preempted, and it prevents a life lock when the task which tries to
1273 * delete a timer preempted the softirq thread running the timer callback
1274 * function.
1275 */
1276static void del_timer_wait_running(struct timer_list *timer)
1277{
1278 u32 tf;
1279
1280 tf = READ_ONCE(timer->flags);
1281 if (!(tf & TIMER_MIGRATING)) {
1282 struct timer_base *base = get_timer_base(tf);
1283
1284 /*
1285 * Mark the base as contended and grab the expiry lock,
1286 * which is held by the softirq across the timer
1287 * callback. Drop the lock immediately so the softirq can
1288 * expire the next timer. In theory the timer could already
1289 * be running again, but that's more than unlikely and just
1290 * causes another wait loop.
1291 */
1292 atomic_inc(&base->timer_waiters);
1293 spin_lock_bh(&base->expiry_lock);
1294 atomic_dec(&base->timer_waiters);
1295 spin_unlock_bh(&base->expiry_lock);
1296 }
1297}
1298#else
1299static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
1300static inline void timer_base_lock_expiry(struct timer_base *base) { }
1301static inline void timer_base_unlock_expiry(struct timer_base *base) { }
1302static inline void timer_sync_wait_running(struct timer_base *base) { }
1303static inline void del_timer_wait_running(struct timer_list *timer) { }
1304#endif
1305
1306#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
1307/**
1308 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1309 * @timer: the timer to be deactivated
1310 *
1311 * This function only differs from del_timer() on SMP: besides deactivating
1312 * the timer it also makes sure the handler has finished executing on other
1313 * CPUs.
1314 *
1315 * Synchronization rules: Callers must prevent restarting of the timer,
1316 * otherwise this function is meaningless. It must not be called from
1317 * interrupt contexts unless the timer is an irqsafe one. The caller must
1318 * not hold locks which would prevent completion of the timer's
1319 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1320 * timer is not queued and the handler is not running on any CPU.
1321 *
1322 * Note: For !irqsafe timers, you must not hold locks that are held in
1323 * interrupt context while calling this function. Even if the lock has
1324 * nothing to do with the timer in question. Here's why::
1325 *
1326 * CPU0 CPU1
1327 * ---- ----
1328 * <SOFTIRQ>
1329 * call_timer_fn();
1330 * base->running_timer = mytimer;
1331 * spin_lock_irq(somelock);
1332 * <IRQ>
1333 * spin_lock(somelock);
1334 * del_timer_sync(mytimer);
1335 * while (base->running_timer == mytimer);
1336 *
1337 * Now del_timer_sync() will never return and never release somelock.
1338 * The interrupt on the other CPU is waiting to grab somelock but
1339 * it has interrupted the softirq that CPU0 is waiting to finish.
1340 *
1341 * The function returns whether it has deactivated a pending timer or not.
1342 */
1343int del_timer_sync(struct timer_list *timer)
1344{
1345 int ret;
1346
1347#ifdef CONFIG_LOCKDEP
1348 unsigned long flags;
1349
1350 /*
1351 * If lockdep gives a backtrace here, please reference
1352 * the synchronization rules above.
1353 */
1354 local_irq_save(flags);
1355 lock_map_acquire(&timer->lockdep_map);
1356 lock_map_release(&timer->lockdep_map);
1357 local_irq_restore(flags);
1358#endif
1359 /*
1360 * don't use it in hardirq context, because it
1361 * could lead to deadlock.
1362 */
1363 WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1364
1365 do {
1366 ret = try_to_del_timer_sync(timer);
1367
1368 if (unlikely(ret < 0)) {
1369 del_timer_wait_running(timer);
1370 cpu_relax();
1371 }
1372 } while (ret < 0);
1373
1374 return ret;
1375}
1376EXPORT_SYMBOL(del_timer_sync);
1377#endif
1378
1379static void call_timer_fn(struct timer_list *timer,
1380 void (*fn)(struct timer_list *),
1381 unsigned long baseclk)
1382{
1383 int count = preempt_count();
1384
1385#ifdef CONFIG_LOCKDEP
1386 /*
1387 * It is permissible to free the timer from inside the
1388 * function that is called from it, this we need to take into
1389 * account for lockdep too. To avoid bogus "held lock freed"
1390 * warnings as well as problems when looking into
1391 * timer->lockdep_map, make a copy and use that here.
1392 */
1393 struct lockdep_map lockdep_map;
1394
1395 lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1396#endif
1397 /*
1398 * Couple the lock chain with the lock chain at
1399 * del_timer_sync() by acquiring the lock_map around the fn()
1400 * call here and in del_timer_sync().
1401 */
1402 lock_map_acquire(&lockdep_map);
1403
1404 trace_timer_expire_entry(timer, baseclk);
1405 fn(timer);
1406 trace_timer_expire_exit(timer);
1407
1408 lock_map_release(&lockdep_map);
1409
1410 if (count != preempt_count()) {
1411 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1412 fn, count, preempt_count());
1413 /*
1414 * Restore the preempt count. That gives us a decent
1415 * chance to survive and extract information. If the
1416 * callback kept a lock held, bad luck, but not worse
1417 * than the BUG() we had.
1418 */
1419 preempt_count_set(count);
1420 }
1421}
1422
1423static void expire_timers(struct timer_base *base, struct hlist_head *head)
1424{
1425 /*
1426 * This value is required only for tracing. base->clk was
1427 * incremented directly before expire_timers was called. But expiry
1428 * is related to the old base->clk value.
1429 */
1430 unsigned long baseclk = base->clk - 1;
1431
1432 while (!hlist_empty(head)) {
1433 struct timer_list *timer;
1434 void (*fn)(struct timer_list *);
1435
1436 timer = hlist_entry(head->first, struct timer_list, entry);
1437
1438 base->running_timer = timer;
1439 detach_timer(timer, true);
1440
1441 fn = timer->function;
1442
1443 if (timer->flags & TIMER_IRQSAFE) {
1444 raw_spin_unlock(&base->lock);
1445 call_timer_fn(timer, fn, baseclk);
1446 base->running_timer = NULL;
1447 raw_spin_lock(&base->lock);
1448 } else {
1449 raw_spin_unlock_irq(&base->lock);
1450 call_timer_fn(timer, fn, baseclk);
1451 base->running_timer = NULL;
1452 timer_sync_wait_running(base);
1453 raw_spin_lock_irq(&base->lock);
1454 }
1455 }
1456}
1457
1458static int __collect_expired_timers(struct timer_base *base,
1459 struct hlist_head *heads)
1460{
1461 unsigned long clk = base->clk;
1462 struct hlist_head *vec;
1463 int i, levels = 0;
1464 unsigned int idx;
1465
1466 for (i = 0; i < LVL_DEPTH; i++) {
1467 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1468
1469 if (__test_and_clear_bit(idx, base->pending_map)) {
1470 vec = base->vectors + idx;
1471 hlist_move_list(vec, heads++);
1472 levels++;
1473 }
1474 /* Is it time to look at the next level? */
1475 if (clk & LVL_CLK_MASK)
1476 break;
1477 /* Shift clock for the next level granularity */
1478 clk >>= LVL_CLK_SHIFT;
1479 }
1480 return levels;
1481}
1482
1483#ifdef CONFIG_NO_HZ_COMMON
1484/*
1485 * Find the next pending bucket of a level. Search from level start (@offset)
1486 * + @clk upwards and if nothing there, search from start of the level
1487 * (@offset) up to @offset + clk.
1488 */
1489static int next_pending_bucket(struct timer_base *base, unsigned offset,
1490 unsigned clk)
1491{
1492 unsigned pos, start = offset + clk;
1493 unsigned end = offset + LVL_SIZE;
1494
1495 pos = find_next_bit(base->pending_map, end, start);
1496 if (pos < end)
1497 return pos - start;
1498
1499 pos = find_next_bit(base->pending_map, start, offset);
1500 return pos < start ? pos + LVL_SIZE - start : -1;
1501}
1502
1503/*
1504 * Search the first expiring timer in the various clock levels. Caller must
1505 * hold base->lock.
1506 */
1507static unsigned long __next_timer_interrupt(struct timer_base *base)
1508{
1509 unsigned long clk, next, adj;
1510 unsigned lvl, offset = 0;
1511
1512 next = base->clk + NEXT_TIMER_MAX_DELTA;
1513 clk = base->clk;
1514 for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1515 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1516
1517 if (pos >= 0) {
1518 unsigned long tmp = clk + (unsigned long) pos;
1519
1520 tmp <<= LVL_SHIFT(lvl);
1521 if (time_before(tmp, next))
1522 next = tmp;
1523 }
1524 /*
1525 * Clock for the next level. If the current level clock lower
1526 * bits are zero, we look at the next level as is. If not we
1527 * need to advance it by one because that's going to be the
1528 * next expiring bucket in that level. base->clk is the next
1529 * expiring jiffie. So in case of:
1530 *
1531 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1532 * 0 0 0 0 0 0
1533 *
1534 * we have to look at all levels @index 0. With
1535 *
1536 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1537 * 0 0 0 0 0 2
1538 *
1539 * LVL0 has the next expiring bucket @index 2. The upper
1540 * levels have the next expiring bucket @index 1.
1541 *
1542 * In case that the propagation wraps the next level the same
1543 * rules apply:
1544 *
1545 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1546 * 0 0 0 0 F 2
1547 *
1548 * So after looking at LVL0 we get:
1549 *
1550 * LVL5 LVL4 LVL3 LVL2 LVL1
1551 * 0 0 0 1 0
1552 *
1553 * So no propagation from LVL1 to LVL2 because that happened
1554 * with the add already, but then we need to propagate further
1555 * from LVL2 to LVL3.
1556 *
1557 * So the simple check whether the lower bits of the current
1558 * level are 0 or not is sufficient for all cases.
1559 */
1560 adj = clk & LVL_CLK_MASK ? 1 : 0;
1561 clk >>= LVL_CLK_SHIFT;
1562 clk += adj;
1563 }
1564 return next;
1565}
1566
1567/*
1568 * Check, if the next hrtimer event is before the next timer wheel
1569 * event:
1570 */
1571static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1572{
1573 u64 nextevt = hrtimer_get_next_event();
1574
1575 /*
1576 * If high resolution timers are enabled
1577 * hrtimer_get_next_event() returns KTIME_MAX.
1578 */
1579 if (expires <= nextevt)
1580 return expires;
1581
1582 /*
1583 * If the next timer is already expired, return the tick base
1584 * time so the tick is fired immediately.
1585 */
1586 if (nextevt <= basem)
1587 return basem;
1588
1589 /*
1590 * Round up to the next jiffie. High resolution timers are
1591 * off, so the hrtimers are expired in the tick and we need to
1592 * make sure that this tick really expires the timer to avoid
1593 * a ping pong of the nohz stop code.
1594 *
1595 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1596 */
1597 return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1598}
1599
1600/**
1601 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1602 * @basej: base time jiffies
1603 * @basem: base time clock monotonic
1604 *
1605 * Returns the tick aligned clock monotonic time of the next pending
1606 * timer or KTIME_MAX if no timer is pending.
1607 */
1608u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1609{
1610 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1611 u64 expires = KTIME_MAX;
1612 unsigned long nextevt;
1613 bool is_max_delta;
1614
1615 /*
1616 * Pretend that there is no timer pending if the cpu is offline.
1617 * Possible pending timers will be migrated later to an active cpu.
1618 */
1619 if (cpu_is_offline(smp_processor_id()))
1620 return expires;
1621
1622 raw_spin_lock(&base->lock);
1623 nextevt = __next_timer_interrupt(base);
1624 is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
1625 base->next_expiry = nextevt;
1626 /*
1627 * We have a fresh next event. Check whether we can forward the
1628 * base. We can only do that when @basej is past base->clk
1629 * otherwise we might rewind base->clk.
1630 */
1631 if (time_after(basej, base->clk)) {
1632 if (time_after(nextevt, basej))
1633 base->clk = basej;
1634 else if (time_after(nextevt, base->clk))
1635 base->clk = nextevt;
1636 }
1637
1638 if (time_before_eq(nextevt, basej)) {
1639 expires = basem;
1640 base->is_idle = false;
1641 } else {
1642 if (!is_max_delta)
1643 expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1644 /*
1645 * If we expect to sleep more than a tick, mark the base idle.
1646 * Also the tick is stopped so any added timer must forward
1647 * the base clk itself to keep granularity small. This idle
1648 * logic is only maintained for the BASE_STD base, deferrable
1649 * timers may still see large granularity skew (by design).
1650 */
1651 if ((expires - basem) > TICK_NSEC) {
1652 base->must_forward_clk = true;
1653 base->is_idle = true;
1654 }
1655 }
1656 raw_spin_unlock(&base->lock);
1657
1658 return cmp_next_hrtimer_event(basem, expires);
1659}
1660
1661/**
1662 * timer_clear_idle - Clear the idle state of the timer base
1663 *
1664 * Called with interrupts disabled
1665 */
1666void timer_clear_idle(void)
1667{
1668 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1669
1670 /*
1671 * We do this unlocked. The worst outcome is a remote enqueue sending
1672 * a pointless IPI, but taking the lock would just make the window for
1673 * sending the IPI a few instructions smaller for the cost of taking
1674 * the lock in the exit from idle path.
1675 */
1676 base->is_idle = false;
1677}
1678
1679static int collect_expired_timers(struct timer_base *base,
1680 struct hlist_head *heads)
1681{
1682 unsigned long now = READ_ONCE(jiffies);
1683
1684 /*
1685 * NOHZ optimization. After a long idle sleep we need to forward the
1686 * base to current jiffies. Avoid a loop by searching the bitfield for
1687 * the next expiring timer.
1688 */
1689 if ((long)(now - base->clk) > 2) {
1690 unsigned long next = __next_timer_interrupt(base);
1691
1692 /*
1693 * If the next timer is ahead of time forward to current
1694 * jiffies, otherwise forward to the next expiry time:
1695 */
1696 if (time_after(next, now)) {
1697 /*
1698 * The call site will increment base->clk and then
1699 * terminate the expiry loop immediately.
1700 */
1701 base->clk = now;
1702 return 0;
1703 }
1704 base->clk = next;
1705 }
1706 return __collect_expired_timers(base, heads);
1707}
1708#else
1709static inline int collect_expired_timers(struct timer_base *base,
1710 struct hlist_head *heads)
1711{
1712 return __collect_expired_timers(base, heads);
1713}
1714#endif
1715
1716/*
1717 * Called from the timer interrupt handler to charge one tick to the current
1718 * process. user_tick is 1 if the tick is user time, 0 for system.
1719 */
1720void update_process_times(int user_tick)
1721{
1722 struct task_struct *p = current;
1723
1724 /* Note: this timer irq context must be accounted for as well. */
1725 account_process_tick(p, user_tick);
1726 run_local_timers();
1727 rcu_sched_clock_irq(user_tick);
1728#ifdef CONFIG_IRQ_WORK
1729 if (in_irq())
1730 irq_work_tick();
1731#endif
1732 scheduler_tick();
1733 if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1734 run_posix_cpu_timers();
1735}
1736
1737/**
1738 * __run_timers - run all expired timers (if any) on this CPU.
1739 * @base: the timer vector to be processed.
1740 */
1741static inline void __run_timers(struct timer_base *base)
1742{
1743 struct hlist_head heads[LVL_DEPTH];
1744 int levels;
1745
1746 if (!time_after_eq(jiffies, base->clk))
1747 return;
1748
1749 timer_base_lock_expiry(base);
1750 raw_spin_lock_irq(&base->lock);
1751
1752 /*
1753 * timer_base::must_forward_clk must be cleared before running
1754 * timers so that any timer functions that call mod_timer() will
1755 * not try to forward the base. Idle tracking / clock forwarding
1756 * logic is only used with BASE_STD timers.
1757 *
1758 * The must_forward_clk flag is cleared unconditionally also for
1759 * the deferrable base. The deferrable base is not affected by idle
1760 * tracking and never forwarded, so clearing the flag is a NOOP.
1761 *
1762 * The fact that the deferrable base is never forwarded can cause
1763 * large variations in granularity for deferrable timers, but they
1764 * can be deferred for long periods due to idle anyway.
1765 */
1766 base->must_forward_clk = false;
1767
1768 while (time_after_eq(jiffies, base->clk)) {
1769
1770 levels = collect_expired_timers(base, heads);
1771 base->clk++;
1772
1773 while (levels--)
1774 expire_timers(base, heads + levels);
1775 }
1776 raw_spin_unlock_irq(&base->lock);
1777 timer_base_unlock_expiry(base);
1778}
1779
1780/*
1781 * This function runs timers and the timer-tq in bottom half context.
1782 */
1783static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1784{
1785 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1786
1787 __run_timers(base);
1788 if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1789 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1790}
1791
1792/*
1793 * Called by the local, per-CPU timer interrupt on SMP.
1794 */
1795void run_local_timers(void)
1796{
1797 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1798
1799 hrtimer_run_queues();
1800 /* Raise the softirq only if required. */
1801 if (time_before(jiffies, base->clk)) {
1802 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1803 return;
1804 /* CPU is awake, so check the deferrable base. */
1805 base++;
1806 if (time_before(jiffies, base->clk))
1807 return;
1808 }
1809 raise_softirq(TIMER_SOFTIRQ);
1810}
1811
1812/*
1813 * Since schedule_timeout()'s timer is defined on the stack, it must store
1814 * the target task on the stack as well.
1815 */
1816struct process_timer {
1817 struct timer_list timer;
1818 struct task_struct *task;
1819};
1820
1821static void process_timeout(struct timer_list *t)
1822{
1823 struct process_timer *timeout = from_timer(timeout, t, timer);
1824
1825 wake_up_process(timeout->task);
1826}
1827
1828/**
1829 * schedule_timeout - sleep until timeout
1830 * @timeout: timeout value in jiffies
1831 *
1832 * Make the current task sleep until @timeout jiffies have elapsed.
1833 * The function behavior depends on the current task state
1834 * (see also set_current_state() description):
1835 *
1836 * %TASK_RUNNING - the scheduler is called, but the task does not sleep
1837 * at all. That happens because sched_submit_work() does nothing for
1838 * tasks in %TASK_RUNNING state.
1839 *
1840 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1841 * pass before the routine returns unless the current task is explicitly
1842 * woken up, (e.g. by wake_up_process()).
1843 *
1844 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1845 * delivered to the current task or the current task is explicitly woken
1846 * up.
1847 *
1848 * The current task state is guaranteed to be %TASK_RUNNING when this
1849 * routine returns.
1850 *
1851 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1852 * the CPU away without a bound on the timeout. In this case the return
1853 * value will be %MAX_SCHEDULE_TIMEOUT.
1854 *
1855 * Returns 0 when the timer has expired otherwise the remaining time in
1856 * jiffies will be returned. In all cases the return value is guaranteed
1857 * to be non-negative.
1858 */
1859signed long __sched schedule_timeout(signed long timeout)
1860{
1861 struct process_timer timer;
1862 unsigned long expire;
1863
1864 switch (timeout)
1865 {
1866 case MAX_SCHEDULE_TIMEOUT:
1867 /*
1868 * These two special cases are useful to be comfortable
1869 * in the caller. Nothing more. We could take
1870 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1871 * but I' d like to return a valid offset (>=0) to allow
1872 * the caller to do everything it want with the retval.
1873 */
1874 schedule();
1875 goto out;
1876 default:
1877 /*
1878 * Another bit of PARANOID. Note that the retval will be
1879 * 0 since no piece of kernel is supposed to do a check
1880 * for a negative retval of schedule_timeout() (since it
1881 * should never happens anyway). You just have the printk()
1882 * that will tell you if something is gone wrong and where.
1883 */
1884 if (timeout < 0) {
1885 printk(KERN_ERR "schedule_timeout: wrong timeout "
1886 "value %lx\n", timeout);
1887 dump_stack();
1888 current->state = TASK_RUNNING;
1889 goto out;
1890 }
1891 }
1892
1893 expire = timeout + jiffies;
1894
1895 timer.task = current;
1896 timer_setup_on_stack(&timer.timer, process_timeout, 0);
1897 __mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
1898 schedule();
1899 del_singleshot_timer_sync(&timer.timer);
1900
1901 /* Remove the timer from the object tracker */
1902 destroy_timer_on_stack(&timer.timer);
1903
1904 timeout = expire - jiffies;
1905
1906 out:
1907 return timeout < 0 ? 0 : timeout;
1908}
1909EXPORT_SYMBOL(schedule_timeout);
1910
1911/*
1912 * We can use __set_current_state() here because schedule_timeout() calls
1913 * schedule() unconditionally.
1914 */
1915signed long __sched schedule_timeout_interruptible(signed long timeout)
1916{
1917 __set_current_state(TASK_INTERRUPTIBLE);
1918 return schedule_timeout(timeout);
1919}
1920EXPORT_SYMBOL(schedule_timeout_interruptible);
1921
1922signed long __sched schedule_timeout_killable(signed long timeout)
1923{
1924 __set_current_state(TASK_KILLABLE);
1925 return schedule_timeout(timeout);
1926}
1927EXPORT_SYMBOL(schedule_timeout_killable);
1928
1929signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1930{
1931 __set_current_state(TASK_UNINTERRUPTIBLE);
1932 return schedule_timeout(timeout);
1933}
1934EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1935
1936/*
1937 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1938 * to load average.
1939 */
1940signed long __sched schedule_timeout_idle(signed long timeout)
1941{
1942 __set_current_state(TASK_IDLE);
1943 return schedule_timeout(timeout);
1944}
1945EXPORT_SYMBOL(schedule_timeout_idle);
1946
1947#ifdef CONFIG_HOTPLUG_CPU
1948static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1949{
1950 struct timer_list *timer;
1951 int cpu = new_base->cpu;
1952
1953 while (!hlist_empty(head)) {
1954 timer = hlist_entry(head->first, struct timer_list, entry);
1955 detach_timer(timer, false);
1956 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1957 internal_add_timer(new_base, timer);
1958 }
1959}
1960
1961int timers_prepare_cpu(unsigned int cpu)
1962{
1963 struct timer_base *base;
1964 int b;
1965
1966 for (b = 0; b < NR_BASES; b++) {
1967 base = per_cpu_ptr(&timer_bases[b], cpu);
1968 base->clk = jiffies;
1969 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
1970 base->is_idle = false;
1971 base->must_forward_clk = true;
1972 }
1973 return 0;
1974}
1975
1976int timers_dead_cpu(unsigned int cpu)
1977{
1978 struct timer_base *old_base;
1979 struct timer_base *new_base;
1980 int b, i;
1981
1982 BUG_ON(cpu_online(cpu));
1983
1984 for (b = 0; b < NR_BASES; b++) {
1985 old_base = per_cpu_ptr(&timer_bases[b], cpu);
1986 new_base = get_cpu_ptr(&timer_bases[b]);
1987 /*
1988 * The caller is globally serialized and nobody else
1989 * takes two locks at once, deadlock is not possible.
1990 */
1991 raw_spin_lock_irq(&new_base->lock);
1992 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1993
1994 /*
1995 * The current CPUs base clock might be stale. Update it
1996 * before moving the timers over.
1997 */
1998 forward_timer_base(new_base);
1999
2000 BUG_ON(old_base->running_timer);
2001
2002 for (i = 0; i < WHEEL_SIZE; i++)
2003 migrate_timer_list(new_base, old_base->vectors + i);
2004
2005 raw_spin_unlock(&old_base->lock);
2006 raw_spin_unlock_irq(&new_base->lock);
2007 put_cpu_ptr(&timer_bases);
2008 }
2009 return 0;
2010}
2011
2012#endif /* CONFIG_HOTPLUG_CPU */
2013
2014static void __init init_timer_cpu(int cpu)
2015{
2016 struct timer_base *base;
2017 int i;
2018
2019 for (i = 0; i < NR_BASES; i++) {
2020 base = per_cpu_ptr(&timer_bases[i], cpu);
2021 base->cpu = cpu;
2022 raw_spin_lock_init(&base->lock);
2023 base->clk = jiffies;
2024 timer_base_init_expiry_lock(base);
2025 }
2026}
2027
2028static void __init init_timer_cpus(void)
2029{
2030 int cpu;
2031
2032 for_each_possible_cpu(cpu)
2033 init_timer_cpu(cpu);
2034}
2035
2036void __init init_timers(void)
2037{
2038 init_timer_cpus();
2039 open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2040}
2041
2042/**
2043 * msleep - sleep safely even with waitqueue interruptions
2044 * @msecs: Time in milliseconds to sleep for
2045 */
2046void msleep(unsigned int msecs)
2047{
2048 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2049
2050 while (timeout)
2051 timeout = schedule_timeout_uninterruptible(timeout);
2052}
2053
2054EXPORT_SYMBOL(msleep);
2055
2056/**
2057 * msleep_interruptible - sleep waiting for signals
2058 * @msecs: Time in milliseconds to sleep for
2059 */
2060unsigned long msleep_interruptible(unsigned int msecs)
2061{
2062 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2063
2064 while (timeout && !signal_pending(current))
2065 timeout = schedule_timeout_interruptible(timeout);
2066 return jiffies_to_msecs(timeout);
2067}
2068
2069EXPORT_SYMBOL(msleep_interruptible);
2070
2071/**
2072 * usleep_range - Sleep for an approximate time
2073 * @min: Minimum time in usecs to sleep
2074 * @max: Maximum time in usecs to sleep
2075 *
2076 * In non-atomic context where the exact wakeup time is flexible, use
2077 * usleep_range() instead of udelay(). The sleep improves responsiveness
2078 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2079 * power usage by allowing hrtimers to take advantage of an already-
2080 * scheduled interrupt instead of scheduling a new one just for this sleep.
2081 */
2082void __sched usleep_range(unsigned long min, unsigned long max)
2083{
2084 ktime_t exp = ktime_add_us(ktime_get(), min);
2085 u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2086
2087 for (;;) {
2088 __set_current_state(TASK_UNINTERRUPTIBLE);
2089 /* Do not return before the requested sleep time has elapsed */
2090 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2091 break;
2092 }
2093}
2094EXPORT_SYMBOL(usleep_range);