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TOMOYO Linux Cross Reference
Linux/kernel/time/timer.c

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

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