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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
948static inline int
949__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
950{
951 struct timer_base *base, *new_base;
952 unsigned int idx = UINT_MAX;
953 unsigned long clk = 0, flags;
954 int ret = 0;
955
956 BUG_ON(!timer->function);
957
958 /*
959 * This is a common optimization triggered by the networking code - if
960 * the timer is re-modified to have the same timeout or ends up in the
961 * same array bucket then just return:
962 */
963 if (timer_pending(timer)) {
964 /*
965 * The downside of this optimization is that it can result in
966 * larger granularity than you would get from adding a new
967 * timer with this expiry.
968 */
969 long diff = timer->expires - expires;
970
971 if (!diff)
972 return 1;
973 if (options & MOD_TIMER_REDUCE && diff <= 0)
974 return 1;
975
976 /*
977 * We lock timer base and calculate the bucket index right
978 * here. If the timer ends up in the same bucket, then we
979 * just update the expiry time and avoid the whole
980 * dequeue/enqueue dance.
981 */
982 base = lock_timer_base(timer, &flags);
983 forward_timer_base(base);
984
985 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
986 time_before_eq(timer->expires, expires)) {
987 ret = 1;
988 goto out_unlock;
989 }
990
991 clk = base->clk;
992 idx = calc_wheel_index(expires, clk);
993
994 /*
995 * Retrieve and compare the array index of the pending
996 * timer. If it matches set the expiry to the new value so a
997 * subsequent call will exit in the expires check above.
998 */
999 if (idx == timer_get_idx(timer)) {
1000 if (!(options & MOD_TIMER_REDUCE))
1001 timer->expires = expires;
1002 else if (time_after(timer->expires, expires))
1003 timer->expires = expires;
1004 ret = 1;
1005 goto out_unlock;
1006 }
1007 } else {
1008 base = lock_timer_base(timer, &flags);
1009 forward_timer_base(base);
1010 }
1011
1012 ret = detach_if_pending(timer, base, false);
1013 if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1014 goto out_unlock;
1015
1016 new_base = get_target_base(base, timer->flags);
1017
1018 if (base != new_base) {
1019 /*
1020 * We are trying to schedule the timer on the new base.
1021 * However we can't change timer's base while it is running,
1022 * otherwise del_timer_sync() can't detect that the timer's
1023 * handler yet has not finished. This also guarantees that the
1024 * timer is serialized wrt itself.
1025 */
1026 if (likely(base->running_timer != timer)) {
1027 /* See the comment in lock_timer_base() */
1028 timer->flags |= TIMER_MIGRATING;
1029
1030 raw_spin_unlock(&base->lock);
1031 base = new_base;
1032 raw_spin_lock(&base->lock);
1033 WRITE_ONCE(timer->flags,
1034 (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1035 forward_timer_base(base);
1036 }
1037 }
1038
1039 debug_timer_activate(timer);
1040
1041 timer->expires = expires;
1042 /*
1043 * If 'idx' was calculated above and the base time did not advance
1044 * between calculating 'idx' and possibly switching the base, only
1045 * enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
1046 * we need to (re)calculate the wheel index via
1047 * internal_add_timer().
1048 */
1049 if (idx != UINT_MAX && clk == base->clk) {
1050 enqueue_timer(base, timer, idx);
1051 trigger_dyntick_cpu(base, timer);
1052 } else {
1053 internal_add_timer(base, timer);
1054 }
1055
1056out_unlock:
1057 raw_spin_unlock_irqrestore(&base->lock, flags);
1058
1059 return ret;
1060}
1061
1062/**
1063 * mod_timer_pending - modify a pending timer's timeout
1064 * @timer: the pending timer to be modified
1065 * @expires: new timeout in jiffies
1066 *
1067 * mod_timer_pending() is the same for pending timers as mod_timer(),
1068 * but will not re-activate and modify already deleted timers.
1069 *
1070 * It is useful for unserialized use of timers.
1071 */
1072int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1073{
1074 return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1075}
1076EXPORT_SYMBOL(mod_timer_pending);
1077
1078/**
1079 * mod_timer - modify a timer's timeout
1080 * @timer: the timer to be modified
1081 * @expires: new timeout in jiffies
1082 *
1083 * mod_timer() is a more efficient way to update the expire field of an
1084 * active timer (if the timer is inactive it will be activated)
1085 *
1086 * mod_timer(timer, expires) is equivalent to:
1087 *
1088 * del_timer(timer); timer->expires = expires; add_timer(timer);
1089 *
1090 * Note that if there are multiple unserialized concurrent users of the
1091 * same timer, then mod_timer() is the only safe way to modify the timeout,
1092 * since add_timer() cannot modify an already running timer.
1093 *
1094 * The function returns whether it has modified a pending timer or not.
1095 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1096 * active timer returns 1.)
1097 */
1098int mod_timer(struct timer_list *timer, unsigned long expires)
1099{
1100 return __mod_timer(timer, expires, 0);
1101}
1102EXPORT_SYMBOL(mod_timer);
1103
1104/**
1105 * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1106 * @timer: The timer to be modified
1107 * @expires: New timeout in jiffies
1108 *
1109 * timer_reduce() is very similar to mod_timer(), except that it will only
1110 * modify a running timer if that would reduce the expiration time (it will
1111 * start a timer that isn't running).
1112 */
1113int timer_reduce(struct timer_list *timer, unsigned long expires)
1114{
1115 return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1116}
1117EXPORT_SYMBOL(timer_reduce);
1118
1119/**
1120 * add_timer - start a timer
1121 * @timer: the timer to be added
1122 *
1123 * The kernel will do a ->function(@timer) callback from the
1124 * timer interrupt at the ->expires point in the future. The
1125 * current time is 'jiffies'.
1126 *
1127 * The timer's ->expires, ->function fields must be set prior calling this
1128 * function.
1129 *
1130 * Timers with an ->expires field in the past will be executed in the next
1131 * timer tick.
1132 */
1133void add_timer(struct timer_list *timer)
1134{
1135 BUG_ON(timer_pending(timer));
1136 mod_timer(timer, timer->expires);
1137}
1138EXPORT_SYMBOL(add_timer);
1139
1140/**
1141 * add_timer_on - start a timer on a particular CPU
1142 * @timer: the timer to be added
1143 * @cpu: the CPU to start it on
1144 *
1145 * This is not very scalable on SMP. Double adds are not possible.
1146 */
1147void add_timer_on(struct timer_list *timer, int cpu)
1148{
1149 struct timer_base *new_base, *base;
1150 unsigned long flags;
1151
1152 BUG_ON(timer_pending(timer) || !timer->function);
1153
1154 new_base = get_timer_cpu_base(timer->flags, cpu);
1155
1156 /*
1157 * If @timer was on a different CPU, it should be migrated with the
1158 * old base locked to prevent other operations proceeding with the
1159 * wrong base locked. See lock_timer_base().
1160 */
1161 base = lock_timer_base(timer, &flags);
1162 if (base != new_base) {
1163 timer->flags |= TIMER_MIGRATING;
1164
1165 raw_spin_unlock(&base->lock);
1166 base = new_base;
1167 raw_spin_lock(&base->lock);
1168 WRITE_ONCE(timer->flags,
1169 (timer->flags & ~TIMER_BASEMASK) | cpu);
1170 }
1171 forward_timer_base(base);
1172
1173 debug_timer_activate(timer);
1174 internal_add_timer(base, timer);
1175 raw_spin_unlock_irqrestore(&base->lock, flags);
1176}
1177EXPORT_SYMBOL_GPL(add_timer_on);
1178
1179/**
1180 * del_timer - deactivate a timer.
1181 * @timer: the timer to be deactivated
1182 *
1183 * del_timer() deactivates a timer - this works on both active and inactive
1184 * timers.
1185 *
1186 * The function returns whether it has deactivated a pending timer or not.
1187 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1188 * active timer returns 1.)
1189 */
1190int del_timer(struct timer_list *timer)
1191{
1192 struct timer_base *base;
1193 unsigned long flags;
1194 int ret = 0;
1195
1196 debug_assert_init(timer);
1197
1198 if (timer_pending(timer)) {
1199 base = lock_timer_base(timer, &flags);
1200 ret = detach_if_pending(timer, base, true);
1201 raw_spin_unlock_irqrestore(&base->lock, flags);
1202 }
1203
1204 return ret;
1205}
1206EXPORT_SYMBOL(del_timer);
1207
1208/**
1209 * try_to_del_timer_sync - Try to deactivate a timer
1210 * @timer: timer to delete
1211 *
1212 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1213 * exit the timer is not queued and the handler is not running on any CPU.
1214 */
1215int try_to_del_timer_sync(struct timer_list *timer)
1216{
1217 struct timer_base *base;
1218 unsigned long flags;
1219 int ret = -1;
1220
1221 debug_assert_init(timer);
1222
1223 base = lock_timer_base(timer, &flags);
1224
1225 if (base->running_timer != timer)
1226 ret = detach_if_pending(timer, base, true);
1227
1228 raw_spin_unlock_irqrestore(&base->lock, flags);
1229
1230 return ret;
1231}
1232EXPORT_SYMBOL(try_to_del_timer_sync);
1233
1234#ifdef CONFIG_PREEMPT_RT
1235static __init void timer_base_init_expiry_lock(struct timer_base *base)
1236{
1237 spin_lock_init(&base->expiry_lock);
1238}
1239
1240static inline void timer_base_lock_expiry(struct timer_base *base)
1241{
1242 spin_lock(&base->expiry_lock);
1243}
1244
1245static inline void timer_base_unlock_expiry(struct timer_base *base)
1246{
1247 spin_unlock(&base->expiry_lock);
1248}
1249
1250/*
1251 * The counterpart to del_timer_wait_running().
1252 *
1253 * If there is a waiter for base->expiry_lock, then it was waiting for the
1254 * timer callback to finish. Drop expiry_lock and reaquire it. That allows
1255 * the waiter to acquire the lock and make progress.
1256 */
1257static void timer_sync_wait_running(struct timer_base *base)
1258{
1259 if (atomic_read(&base->timer_waiters)) {
1260 spin_unlock(&base->expiry_lock);
1261 spin_lock(&base->expiry_lock);
1262 }
1263}
1264
1265/*
1266 * This function is called on PREEMPT_RT kernels when the fast path
1267 * deletion of a timer failed because the timer callback function was
1268 * running.
1269 *
1270 * This prevents priority inversion, if the softirq thread on a remote CPU
1271 * got preempted, and it prevents a life lock when the task which tries to
1272 * delete a timer preempted the softirq thread running the timer callback
1273 * function.
1274 */
1275static void del_timer_wait_running(struct timer_list *timer)
1276{
1277 u32 tf;
1278
1279 tf = READ_ONCE(timer->flags);
1280 if (!(tf & TIMER_MIGRATING)) {
1281 struct timer_base *base = get_timer_base(tf);
1282
1283 /*
1284 * Mark the base as contended and grab the expiry lock,
1285 * which is held by the softirq across the timer
1286 * callback. Drop the lock immediately so the softirq can
1287 * expire the next timer. In theory the timer could already
1288 * be running again, but that's more than unlikely and just
1289 * causes another wait loop.
1290 */
1291 atomic_inc(&base->timer_waiters);
1292 spin_lock_bh(&base->expiry_lock);
1293 atomic_dec(&base->timer_waiters);
1294 spin_unlock_bh(&base->expiry_lock);
1295 }
1296}
1297#else
1298static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
1299static inline void timer_base_lock_expiry(struct timer_base *base) { }
1300static inline void timer_base_unlock_expiry(struct timer_base *base) { }
1301static inline void timer_sync_wait_running(struct timer_base *base) { }
1302static inline void del_timer_wait_running(struct timer_list *timer) { }
1303#endif
1304
1305#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
1306/**
1307 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1308 * @timer: the timer to be deactivated
1309 *
1310 * This function only differs from del_timer() on SMP: besides deactivating
1311 * the timer it also makes sure the handler has finished executing on other
1312 * CPUs.
1313 *
1314 * Synchronization rules: Callers must prevent restarting of the timer,
1315 * otherwise this function is meaningless. It must not be called from
1316 * interrupt contexts unless the timer is an irqsafe one. The caller must
1317 * not hold locks which would prevent completion of the timer's
1318 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1319 * timer is not queued and the handler is not running on any CPU.
1320 *
1321 * Note: For !irqsafe timers, you must not hold locks that are held in
1322 * interrupt context while calling this function. Even if the lock has
1323 * nothing to do with the timer in question. Here's why::
1324 *
1325 * CPU0 CPU1
1326 * ---- ----
1327 * <SOFTIRQ>
1328 * call_timer_fn();
1329 * base->running_timer = mytimer;
1330 * spin_lock_irq(somelock);
1331 * <IRQ>
1332 * spin_lock(somelock);
1333 * del_timer_sync(mytimer);
1334 * while (base->running_timer == mytimer);
1335 *
1336 * Now del_timer_sync() will never return and never release somelock.
1337 * The interrupt on the other CPU is waiting to grab somelock but
1338 * it has interrupted the softirq that CPU0 is waiting to finish.
1339 *
1340 * The function returns whether it has deactivated a pending timer or not.
1341 */
1342int del_timer_sync(struct timer_list *timer)
1343{
1344 int ret;
1345
1346#ifdef CONFIG_LOCKDEP
1347 unsigned long flags;
1348
1349 /*
1350 * If lockdep gives a backtrace here, please reference
1351 * the synchronization rules above.
1352 */
1353 local_irq_save(flags);
1354 lock_map_acquire(&timer->lockdep_map);
1355 lock_map_release(&timer->lockdep_map);
1356 local_irq_restore(flags);
1357#endif
1358 /*
1359 * don't use it in hardirq context, because it
1360 * could lead to deadlock.
1361 */
1362 WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1363
1364 do {
1365 ret = try_to_del_timer_sync(timer);
1366
1367 if (unlikely(ret < 0)) {
1368 del_timer_wait_running(timer);
1369 cpu_relax();
1370 }
1371 } while (ret < 0);
1372
1373 return ret;
1374}
1375EXPORT_SYMBOL(del_timer_sync);
1376#endif
1377
1378static void call_timer_fn(struct timer_list *timer,
1379 void (*fn)(struct timer_list *),
1380 unsigned long baseclk)
1381{
1382 int count = preempt_count();
1383
1384#ifdef CONFIG_LOCKDEP
1385 /*
1386 * It is permissible to free the timer from inside the
1387 * function that is called from it, this we need to take into
1388 * account for lockdep too. To avoid bogus "held lock freed"
1389 * warnings as well as problems when looking into
1390 * timer->lockdep_map, make a copy and use that here.
1391 */
1392 struct lockdep_map lockdep_map;
1393
1394 lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1395#endif
1396 /*
1397 * Couple the lock chain with the lock chain at
1398 * del_timer_sync() by acquiring the lock_map around the fn()
1399 * call here and in del_timer_sync().
1400 */
1401 lock_map_acquire(&lockdep_map);
1402
1403 trace_timer_expire_entry(timer, baseclk);
1404 fn(timer);
1405 trace_timer_expire_exit(timer);
1406
1407 lock_map_release(&lockdep_map);
1408
1409 if (count != preempt_count()) {
1410 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1411 fn, count, preempt_count());
1412 /*
1413 * Restore the preempt count. That gives us a decent
1414 * chance to survive and extract information. If the
1415 * callback kept a lock held, bad luck, but not worse
1416 * than the BUG() we had.
1417 */
1418 preempt_count_set(count);
1419 }
1420}
1421
1422static void expire_timers(struct timer_base *base, struct hlist_head *head)
1423{
1424 /*
1425 * This value is required only for tracing. base->clk was
1426 * incremented directly before expire_timers was called. But expiry
1427 * is related to the old base->clk value.
1428 */
1429 unsigned long baseclk = base->clk - 1;
1430
1431 while (!hlist_empty(head)) {
1432 struct timer_list *timer;
1433 void (*fn)(struct timer_list *);
1434
1435 timer = hlist_entry(head->first, struct timer_list, entry);
1436
1437 base->running_timer = timer;
1438 detach_timer(timer, true);
1439
1440 fn = timer->function;
1441
1442 if (timer->flags & TIMER_IRQSAFE) {
1443 raw_spin_unlock(&base->lock);
1444 call_timer_fn(timer, fn, baseclk);
1445 base->running_timer = NULL;
1446 raw_spin_lock(&base->lock);
1447 } else {
1448 raw_spin_unlock_irq(&base->lock);
1449 call_timer_fn(timer, fn, baseclk);
1450 base->running_timer = NULL;
1451 timer_sync_wait_running(base);
1452 raw_spin_lock_irq(&base->lock);
1453 }
1454 }
1455}
1456
1457static int __collect_expired_timers(struct timer_base *base,
1458 struct hlist_head *heads)
1459{
1460 unsigned long clk = base->clk;
1461 struct hlist_head *vec;
1462 int i, levels = 0;
1463 unsigned int idx;
1464
1465 for (i = 0; i < LVL_DEPTH; i++) {
1466 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1467
1468 if (__test_and_clear_bit(idx, base->pending_map)) {
1469 vec = base->vectors + idx;
1470 hlist_move_list(vec, heads++);
1471 levels++;
1472 }
1473 /* Is it time to look at the next level? */
1474 if (clk & LVL_CLK_MASK)
1475 break;
1476 /* Shift clock for the next level granularity */
1477 clk >>= LVL_CLK_SHIFT;
1478 }
1479 return levels;
1480}
1481
1482#ifdef CONFIG_NO_HZ_COMMON
1483/*
1484 * Find the next pending bucket of a level. Search from level start (@offset)
1485 * + @clk upwards and if nothing there, search from start of the level
1486 * (@offset) up to @offset + clk.
1487 */
1488static int next_pending_bucket(struct timer_base *base, unsigned offset,
1489 unsigned clk)
1490{
1491 unsigned pos, start = offset + clk;
1492 unsigned end = offset + LVL_SIZE;
1493
1494 pos = find_next_bit(base->pending_map, end, start);
1495 if (pos < end)
1496 return pos - start;
1497
1498 pos = find_next_bit(base->pending_map, start, offset);
1499 return pos < start ? pos + LVL_SIZE - start : -1;
1500}
1501
1502/*
1503 * Search the first expiring timer in the various clock levels. Caller must
1504 * hold base->lock.
1505 */
1506static unsigned long __next_timer_interrupt(struct timer_base *base)
1507{
1508 unsigned long clk, next, adj;
1509 unsigned lvl, offset = 0;
1510
1511 next = base->clk + NEXT_TIMER_MAX_DELTA;
1512 clk = base->clk;
1513 for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1514 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1515
1516 if (pos >= 0) {
1517 unsigned long tmp = clk + (unsigned long) pos;
1518
1519 tmp <<= LVL_SHIFT(lvl);
1520 if (time_before(tmp, next))
1521 next = tmp;
1522 }
1523 /*
1524 * Clock for the next level. If the current level clock lower
1525 * bits are zero, we look at the next level as is. If not we
1526 * need to advance it by one because that's going to be the
1527 * next expiring bucket in that level. base->clk is the next
1528 * expiring jiffie. So in case of:
1529 *
1530 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1531 * 0 0 0 0 0 0
1532 *
1533 * we have to look at all levels @index 0. With
1534 *
1535 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1536 * 0 0 0 0 0 2
1537 *
1538 * LVL0 has the next expiring bucket @index 2. The upper
1539 * levels have the next expiring bucket @index 1.
1540 *
1541 * In case that the propagation wraps the next level the same
1542 * rules apply:
1543 *
1544 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1545 * 0 0 0 0 F 2
1546 *
1547 * So after looking at LVL0 we get:
1548 *
1549 * LVL5 LVL4 LVL3 LVL2 LVL1
1550 * 0 0 0 1 0
1551 *
1552 * So no propagation from LVL1 to LVL2 because that happened
1553 * with the add already, but then we need to propagate further
1554 * from LVL2 to LVL3.
1555 *
1556 * So the simple check whether the lower bits of the current
1557 * level are 0 or not is sufficient for all cases.
1558 */
1559 adj = clk & LVL_CLK_MASK ? 1 : 0;
1560 clk >>= LVL_CLK_SHIFT;
1561 clk += adj;
1562 }
1563 return next;
1564}
1565
1566/*
1567 * Check, if the next hrtimer event is before the next timer wheel
1568 * event:
1569 */
1570static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1571{
1572 u64 nextevt = hrtimer_get_next_event();
1573
1574 /*
1575 * If high resolution timers are enabled
1576 * hrtimer_get_next_event() returns KTIME_MAX.
1577 */
1578 if (expires <= nextevt)
1579 return expires;
1580
1581 /*
1582 * If the next timer is already expired, return the tick base
1583 * time so the tick is fired immediately.
1584 */
1585 if (nextevt <= basem)
1586 return basem;
1587
1588 /*
1589 * Round up to the next jiffie. High resolution timers are
1590 * off, so the hrtimers are expired in the tick and we need to
1591 * make sure that this tick really expires the timer to avoid
1592 * a ping pong of the nohz stop code.
1593 *
1594 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1595 */
1596 return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1597}
1598
1599/**
1600 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1601 * @basej: base time jiffies
1602 * @basem: base time clock monotonic
1603 *
1604 * Returns the tick aligned clock monotonic time of the next pending
1605 * timer or KTIME_MAX if no timer is pending.
1606 */
1607u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1608{
1609 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1610 u64 expires = KTIME_MAX;
1611 unsigned long nextevt;
1612 bool is_max_delta;
1613
1614 /*
1615 * Pretend that there is no timer pending if the cpu is offline.
1616 * Possible pending timers will be migrated later to an active cpu.
1617 */
1618 if (cpu_is_offline(smp_processor_id()))
1619 return expires;
1620
1621 raw_spin_lock(&base->lock);
1622 nextevt = __next_timer_interrupt(base);
1623 is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
1624 base->next_expiry = nextevt;
1625 /*
1626 * We have a fresh next event. Check whether we can forward the
1627 * base. We can only do that when @basej is past base->clk
1628 * otherwise we might rewind base->clk.
1629 */
1630 if (time_after(basej, base->clk)) {
1631 if (time_after(nextevt, basej))
1632 base->clk = basej;
1633 else if (time_after(nextevt, base->clk))
1634 base->clk = nextevt;
1635 }
1636
1637 if (time_before_eq(nextevt, basej)) {
1638 expires = basem;
1639 base->is_idle = false;
1640 } else {
1641 if (!is_max_delta)
1642 expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1643 /*
1644 * If we expect to sleep more than a tick, mark the base idle.
1645 * Also the tick is stopped so any added timer must forward
1646 * the base clk itself to keep granularity small. This idle
1647 * logic is only maintained for the BASE_STD base, deferrable
1648 * timers may still see large granularity skew (by design).
1649 */
1650 if ((expires - basem) > TICK_NSEC) {
1651 base->must_forward_clk = true;
1652 base->is_idle = true;
1653 }
1654 }
1655 raw_spin_unlock(&base->lock);
1656
1657 return cmp_next_hrtimer_event(basem, expires);
1658}
1659
1660/**
1661 * timer_clear_idle - Clear the idle state of the timer base
1662 *
1663 * Called with interrupts disabled
1664 */
1665void timer_clear_idle(void)
1666{
1667 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1668
1669 /*
1670 * We do this unlocked. The worst outcome is a remote enqueue sending
1671 * a pointless IPI, but taking the lock would just make the window for
1672 * sending the IPI a few instructions smaller for the cost of taking
1673 * the lock in the exit from idle path.
1674 */
1675 base->is_idle = false;
1676}
1677
1678static int collect_expired_timers(struct timer_base *base,
1679 struct hlist_head *heads)
1680{
1681 unsigned long now = READ_ONCE(jiffies);
1682
1683 /*
1684 * NOHZ optimization. After a long idle sleep we need to forward the
1685 * base to current jiffies. Avoid a loop by searching the bitfield for
1686 * the next expiring timer.
1687 */
1688 if ((long)(now - base->clk) > 2) {
1689 unsigned long next = __next_timer_interrupt(base);
1690
1691 /*
1692 * If the next timer is ahead of time forward to current
1693 * jiffies, otherwise forward to the next expiry time:
1694 */
1695 if (time_after(next, now)) {
1696 /*
1697 * The call site will increment base->clk and then
1698 * terminate the expiry loop immediately.
1699 */
1700 base->clk = now;
1701 return 0;
1702 }
1703 base->clk = next;
1704 }
1705 return __collect_expired_timers(base, heads);
1706}
1707#else
1708static inline int collect_expired_timers(struct timer_base *base,
1709 struct hlist_head *heads)
1710{
1711 return __collect_expired_timers(base, heads);
1712}
1713#endif
1714
1715/*
1716 * Called from the timer interrupt handler to charge one tick to the current
1717 * process. user_tick is 1 if the tick is user time, 0 for system.
1718 */
1719void update_process_times(int user_tick)
1720{
1721 struct task_struct *p = current;
1722
1723 /* Note: this timer irq context must be accounted for as well. */
1724 account_process_tick(p, user_tick);
1725 run_local_timers();
1726 rcu_sched_clock_irq(user_tick);
1727#ifdef CONFIG_IRQ_WORK
1728 if (in_irq())
1729 irq_work_tick();
1730#endif
1731 scheduler_tick();
1732 if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1733 run_posix_cpu_timers();
1734}
1735
1736/**
1737 * __run_timers - run all expired timers (if any) on this CPU.
1738 * @base: the timer vector to be processed.
1739 */
1740static inline void __run_timers(struct timer_base *base)
1741{
1742 struct hlist_head heads[LVL_DEPTH];
1743 int levels;
1744
1745 if (!time_after_eq(jiffies, base->clk))
1746 return;
1747
1748 timer_base_lock_expiry(base);
1749 raw_spin_lock_irq(&base->lock);
1750
1751 /*
1752 * timer_base::must_forward_clk must be cleared before running
1753 * timers so that any timer functions that call mod_timer() will
1754 * not try to forward the base. Idle tracking / clock forwarding
1755 * logic is only used with BASE_STD timers.
1756 *
1757 * The must_forward_clk flag is cleared unconditionally also for
1758 * the deferrable base. The deferrable base is not affected by idle
1759 * tracking and never forwarded, so clearing the flag is a NOOP.
1760 *
1761 * The fact that the deferrable base is never forwarded can cause
1762 * large variations in granularity for deferrable timers, but they
1763 * can be deferred for long periods due to idle anyway.
1764 */
1765 base->must_forward_clk = false;
1766
1767 while (time_after_eq(jiffies, base->clk)) {
1768
1769 levels = collect_expired_timers(base, heads);
1770 base->clk++;
1771
1772 while (levels--)
1773 expire_timers(base, heads + levels);
1774 }
1775 raw_spin_unlock_irq(&base->lock);
1776 timer_base_unlock_expiry(base);
1777}
1778
1779/*
1780 * This function runs timers and the timer-tq in bottom half context.
1781 */
1782static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1783{
1784 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1785
1786 __run_timers(base);
1787 if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1788 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1789}
1790
1791/*
1792 * Called by the local, per-CPU timer interrupt on SMP.
1793 */
1794void run_local_timers(void)
1795{
1796 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1797
1798 hrtimer_run_queues();
1799 /* Raise the softirq only if required. */
1800 if (time_before(jiffies, base->clk)) {
1801 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1802 return;
1803 /* CPU is awake, so check the deferrable base. */
1804 base++;
1805 if (time_before(jiffies, base->clk))
1806 return;
1807 }
1808 raise_softirq(TIMER_SOFTIRQ);
1809}
1810
1811/*
1812 * Since schedule_timeout()'s timer is defined on the stack, it must store
1813 * the target task on the stack as well.
1814 */
1815struct process_timer {
1816 struct timer_list timer;
1817 struct task_struct *task;
1818};
1819
1820static void process_timeout(struct timer_list *t)
1821{
1822 struct process_timer *timeout = from_timer(timeout, t, timer);
1823
1824 wake_up_process(timeout->task);
1825}
1826
1827/**
1828 * schedule_timeout - sleep until timeout
1829 * @timeout: timeout value in jiffies
1830 *
1831 * Make the current task sleep until @timeout jiffies have
1832 * elapsed. The routine will return immediately unless
1833 * the current task state has been set (see set_current_state()).
1834 *
1835 * You can set the task state as follows -
1836 *
1837 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1838 * pass before the routine returns unless the current task is explicitly
1839 * woken up, (e.g. by wake_up_process())".
1840 *
1841 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1842 * delivered to the current task or the current task is explicitly woken
1843 * up.
1844 *
1845 * The current task state is guaranteed to be TASK_RUNNING when this
1846 * routine returns.
1847 *
1848 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1849 * the CPU away without a bound on the timeout. In this case the return
1850 * value will be %MAX_SCHEDULE_TIMEOUT.
1851 *
1852 * Returns 0 when the timer has expired otherwise the remaining time in
1853 * jiffies will be returned. In all cases the return value is guaranteed
1854 * to be non-negative.
1855 */
1856signed long __sched schedule_timeout(signed long timeout)
1857{
1858 struct process_timer timer;
1859 unsigned long expire;
1860
1861 switch (timeout)
1862 {
1863 case MAX_SCHEDULE_TIMEOUT:
1864 /*
1865 * These two special cases are useful to be comfortable
1866 * in the caller. Nothing more. We could take
1867 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1868 * but I' d like to return a valid offset (>=0) to allow
1869 * the caller to do everything it want with the retval.
1870 */
1871 schedule();
1872 goto out;
1873 default:
1874 /*
1875 * Another bit of PARANOID. Note that the retval will be
1876 * 0 since no piece of kernel is supposed to do a check
1877 * for a negative retval of schedule_timeout() (since it
1878 * should never happens anyway). You just have the printk()
1879 * that will tell you if something is gone wrong and where.
1880 */
1881 if (timeout < 0) {
1882 printk(KERN_ERR "schedule_timeout: wrong timeout "
1883 "value %lx\n", timeout);
1884 dump_stack();
1885 current->state = TASK_RUNNING;
1886 goto out;
1887 }
1888 }
1889
1890 expire = timeout + jiffies;
1891
1892 timer.task = current;
1893 timer_setup_on_stack(&timer.timer, process_timeout, 0);
1894 __mod_timer(&timer.timer, expire, 0);
1895 schedule();
1896 del_singleshot_timer_sync(&timer.timer);
1897
1898 /* Remove the timer from the object tracker */
1899 destroy_timer_on_stack(&timer.timer);
1900
1901 timeout = expire - jiffies;
1902
1903 out:
1904 return timeout < 0 ? 0 : timeout;
1905}
1906EXPORT_SYMBOL(schedule_timeout);
1907
1908/*
1909 * We can use __set_current_state() here because schedule_timeout() calls
1910 * schedule() unconditionally.
1911 */
1912signed long __sched schedule_timeout_interruptible(signed long timeout)
1913{
1914 __set_current_state(TASK_INTERRUPTIBLE);
1915 return schedule_timeout(timeout);
1916}
1917EXPORT_SYMBOL(schedule_timeout_interruptible);
1918
1919signed long __sched schedule_timeout_killable(signed long timeout)
1920{
1921 __set_current_state(TASK_KILLABLE);
1922 return schedule_timeout(timeout);
1923}
1924EXPORT_SYMBOL(schedule_timeout_killable);
1925
1926signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1927{
1928 __set_current_state(TASK_UNINTERRUPTIBLE);
1929 return schedule_timeout(timeout);
1930}
1931EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1932
1933/*
1934 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1935 * to load average.
1936 */
1937signed long __sched schedule_timeout_idle(signed long timeout)
1938{
1939 __set_current_state(TASK_IDLE);
1940 return schedule_timeout(timeout);
1941}
1942EXPORT_SYMBOL(schedule_timeout_idle);
1943
1944#ifdef CONFIG_HOTPLUG_CPU
1945static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1946{
1947 struct timer_list *timer;
1948 int cpu = new_base->cpu;
1949
1950 while (!hlist_empty(head)) {
1951 timer = hlist_entry(head->first, struct timer_list, entry);
1952 detach_timer(timer, false);
1953 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1954 internal_add_timer(new_base, timer);
1955 }
1956}
1957
1958int timers_prepare_cpu(unsigned int cpu)
1959{
1960 struct timer_base *base;
1961 int b;
1962
1963 for (b = 0; b < NR_BASES; b++) {
1964 base = per_cpu_ptr(&timer_bases[b], cpu);
1965 base->clk = jiffies;
1966 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
1967 base->is_idle = false;
1968 base->must_forward_clk = true;
1969 }
1970 return 0;
1971}
1972
1973int timers_dead_cpu(unsigned int cpu)
1974{
1975 struct timer_base *old_base;
1976 struct timer_base *new_base;
1977 int b, i;
1978
1979 BUG_ON(cpu_online(cpu));
1980
1981 for (b = 0; b < NR_BASES; b++) {
1982 old_base = per_cpu_ptr(&timer_bases[b], cpu);
1983 new_base = get_cpu_ptr(&timer_bases[b]);
1984 /*
1985 * The caller is globally serialized and nobody else
1986 * takes two locks at once, deadlock is not possible.
1987 */
1988 raw_spin_lock_irq(&new_base->lock);
1989 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1990
1991 /*
1992 * The current CPUs base clock might be stale. Update it
1993 * before moving the timers over.
1994 */
1995 forward_timer_base(new_base);
1996
1997 BUG_ON(old_base->running_timer);
1998
1999 for (i = 0; i < WHEEL_SIZE; i++)
2000 migrate_timer_list(new_base, old_base->vectors + i);
2001
2002 raw_spin_unlock(&old_base->lock);
2003 raw_spin_unlock_irq(&new_base->lock);
2004 put_cpu_ptr(&timer_bases);
2005 }
2006 return 0;
2007}
2008
2009#endif /* CONFIG_HOTPLUG_CPU */
2010
2011static void __init init_timer_cpu(int cpu)
2012{
2013 struct timer_base *base;
2014 int i;
2015
2016 for (i = 0; i < NR_BASES; i++) {
2017 base = per_cpu_ptr(&timer_bases[i], cpu);
2018 base->cpu = cpu;
2019 raw_spin_lock_init(&base->lock);
2020 base->clk = jiffies;
2021 timer_base_init_expiry_lock(base);
2022 }
2023}
2024
2025static void __init init_timer_cpus(void)
2026{
2027 int cpu;
2028
2029 for_each_possible_cpu(cpu)
2030 init_timer_cpu(cpu);
2031}
2032
2033void __init init_timers(void)
2034{
2035 init_timer_cpus();
2036 open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2037}
2038
2039/**
2040 * msleep - sleep safely even with waitqueue interruptions
2041 * @msecs: Time in milliseconds to sleep for
2042 */
2043void msleep(unsigned int msecs)
2044{
2045 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2046
2047 while (timeout)
2048 timeout = schedule_timeout_uninterruptible(timeout);
2049}
2050
2051EXPORT_SYMBOL(msleep);
2052
2053/**
2054 * msleep_interruptible - sleep waiting for signals
2055 * @msecs: Time in milliseconds to sleep for
2056 */
2057unsigned long msleep_interruptible(unsigned int msecs)
2058{
2059 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2060
2061 while (timeout && !signal_pending(current))
2062 timeout = schedule_timeout_interruptible(timeout);
2063 return jiffies_to_msecs(timeout);
2064}
2065
2066EXPORT_SYMBOL(msleep_interruptible);
2067
2068/**
2069 * usleep_range - Sleep for an approximate time
2070 * @min: Minimum time in usecs to sleep
2071 * @max: Maximum time in usecs to sleep
2072 *
2073 * In non-atomic context where the exact wakeup time is flexible, use
2074 * usleep_range() instead of udelay(). The sleep improves responsiveness
2075 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2076 * power usage by allowing hrtimers to take advantage of an already-
2077 * scheduled interrupt instead of scheduling a new one just for this sleep.
2078 */
2079void __sched usleep_range(unsigned long min, unsigned long max)
2080{
2081 ktime_t exp = ktime_add_us(ktime_get(), min);
2082 u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2083
2084 for (;;) {
2085 __set_current_state(TASK_UNINTERRUPTIBLE);
2086 /* Do not return before the requested sleep time has elapsed */
2087 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2088 break;
2089 }
2090}
2091EXPORT_SYMBOL(usleep_range);