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Linux/kernel/time/timer.c

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  1 /*
  2  *  linux/kernel/timer.c
  3  *
  4  *  Kernel internal timers
  5  *
  6  *  Copyright (C) 1991, 1992  Linus Torvalds
  7  *
  8  *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
  9  *
 10  *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
 11  *              "A Kernel Model for Precision Timekeeping" by Dave Mills
 12  *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
 13  *              serialize accesses to xtime/lost_ticks).
 14  *                              Copyright (C) 1998  Andrea Arcangeli
 15  *  1999-03-10  Improved NTP compatibility by Ulrich Windl
 16  *  2002-05-31  Move sys_sysinfo here and make its locking sane, Robert Love
 17  *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
 18  *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
 19  *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
 20  */
 21 
 22 #include <linux/kernel_stat.h>
 23 #include <linux/export.h>
 24 #include <linux/interrupt.h>
 25 #include <linux/percpu.h>
 26 #include <linux/init.h>
 27 #include <linux/mm.h>
 28 #include <linux/swap.h>
 29 #include <linux/pid_namespace.h>
 30 #include <linux/notifier.h>
 31 #include <linux/thread_info.h>
 32 #include <linux/time.h>
 33 #include <linux/jiffies.h>
 34 #include <linux/posix-timers.h>
 35 #include <linux/cpu.h>
 36 #include <linux/syscalls.h>
 37 #include <linux/delay.h>
 38 #include <linux/tick.h>
 39 #include <linux/kallsyms.h>
 40 #include <linux/irq_work.h>
 41 #include <linux/sched/signal.h>
 42 #include <linux/sched/sysctl.h>
 43 #include <linux/sched/nohz.h>
 44 #include <linux/sched/debug.h>
 45 #include <linux/slab.h>
 46 #include <linux/compat.h>
 47 
 48 #include <linux/uaccess.h>
 49 #include <asm/unistd.h>
 50 #include <asm/div64.h>
 51 #include <asm/timex.h>
 52 #include <asm/io.h>
 53 
 54 #include "tick-internal.h"
 55 
 56 #define CREATE_TRACE_POINTS
 57 #include <trace/events/timer.h>
 58 
 59 __visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
 60 
 61 EXPORT_SYMBOL(jiffies_64);
 62 
 63 /*
 64  * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
 65  * LVL_SIZE buckets. Each level is driven by its own clock and therefor each
 66  * level has a different granularity.
 67  *
 68  * The level granularity is:            LVL_CLK_DIV ^ lvl
 69  * The level clock frequency is:        HZ / (LVL_CLK_DIV ^ level)
 70  *
 71  * The array level of a newly armed timer depends on the relative expiry
 72  * time. The farther the expiry time is away the higher the array level and
 73  * therefor the granularity becomes.
 74  *
 75  * Contrary to the original timer wheel implementation, which aims for 'exact'
 76  * expiry of the timers, this implementation removes the need for recascading
 77  * the timers into the lower array levels. The previous 'classic' timer wheel
 78  * implementation of the kernel already violated the 'exact' expiry by adding
 79  * slack to the expiry time to provide batched expiration. The granularity
 80  * levels provide implicit batching.
 81  *
 82  * This is an optimization of the original timer wheel implementation for the
 83  * majority of the timer wheel use cases: timeouts. The vast majority of
 84  * timeout timers (networking, disk I/O ...) are canceled before expiry. If
 85  * the timeout expires it indicates that normal operation is disturbed, so it
 86  * does not matter much whether the timeout comes with a slight delay.
 87  *
 88  * The only exception to this are networking timers with a small expiry
 89  * time. They rely on the granularity. Those fit into the first wheel level,
 90  * which has HZ granularity.
 91  *
 92  * We don't have cascading anymore. timers with a expiry time above the
 93  * capacity of the last wheel level are force expired at the maximum timeout
 94  * value of the last wheel level. From data sampling we know that the maximum
 95  * value observed is 5 days (network connection tracking), so this should not
 96  * be an issue.
 97  *
 98  * The currently chosen array constants values are a good compromise between
 99  * array size and granularity.
100  *
101  * This results in the following granularity and range levels:
102  *
103  * HZ 1000 steps
104  * Level Offset  Granularity            Range
105  *  0      0         1 ms                0 ms -         63 ms
106  *  1     64         8 ms               64 ms -        511 ms
107  *  2    128        64 ms              512 ms -       4095 ms (512ms - ~4s)
108  *  3    192       512 ms             4096 ms -      32767 ms (~4s - ~32s)
109  *  4    256      4096 ms (~4s)      32768 ms -     262143 ms (~32s - ~4m)
110  *  5    320     32768 ms (~32s)    262144 ms -    2097151 ms (~4m - ~34m)
111  *  6    384    262144 ms (~4m)    2097152 ms -   16777215 ms (~34m - ~4h)
112  *  7    448   2097152 ms (~34m)  16777216 ms -  134217727 ms (~4h - ~1d)
113  *  8    512  16777216 ms (~4h)  134217728 ms - 1073741822 ms (~1d - ~12d)
114  *
115  * HZ  300
116  * Level Offset  Granularity            Range
117  *  0      0         3 ms                0 ms -        210 ms
118  *  1     64        26 ms              213 ms -       1703 ms (213ms - ~1s)
119  *  2    128       213 ms             1706 ms -      13650 ms (~1s - ~13s)
120  *  3    192      1706 ms (~1s)      13653 ms -     109223 ms (~13s - ~1m)
121  *  4    256     13653 ms (~13s)    109226 ms -     873810 ms (~1m - ~14m)
122  *  5    320    109226 ms (~1m)     873813 ms -    6990503 ms (~14m - ~1h)
123  *  6    384    873813 ms (~14m)   6990506 ms -   55924050 ms (~1h - ~15h)
124  *  7    448   6990506 ms (~1h)   55924053 ms -  447392423 ms (~15h - ~5d)
125  *  8    512  55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
126  *
127  * HZ  250
128  * Level Offset  Granularity            Range
129  *  0      0         4 ms                0 ms -        255 ms
130  *  1     64        32 ms              256 ms -       2047 ms (256ms - ~2s)
131  *  2    128       256 ms             2048 ms -      16383 ms (~2s - ~16s)
132  *  3    192      2048 ms (~2s)      16384 ms -     131071 ms (~16s - ~2m)
133  *  4    256     16384 ms (~16s)    131072 ms -    1048575 ms (~2m - ~17m)
134  *  5    320    131072 ms (~2m)    1048576 ms -    8388607 ms (~17m - ~2h)
135  *  6    384   1048576 ms (~17m)   8388608 ms -   67108863 ms (~2h - ~18h)
136  *  7    448   8388608 ms (~2h)   67108864 ms -  536870911 ms (~18h - ~6d)
137  *  8    512  67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
138  *
139  * HZ  100
140  * Level Offset  Granularity            Range
141  *  0      0         10 ms               0 ms -        630 ms
142  *  1     64         80 ms             640 ms -       5110 ms (640ms - ~5s)
143  *  2    128        640 ms            5120 ms -      40950 ms (~5s - ~40s)
144  *  3    192       5120 ms (~5s)     40960 ms -     327670 ms (~40s - ~5m)
145  *  4    256      40960 ms (~40s)   327680 ms -    2621430 ms (~5m - ~43m)
146  *  5    320     327680 ms (~5m)   2621440 ms -   20971510 ms (~43m - ~5h)
147  *  6    384    2621440 ms (~43m) 20971520 ms -  167772150 ms (~5h - ~1d)
148  *  7    448   20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
149  */
150 
151 /* Clock divisor for the next level */
152 #define LVL_CLK_SHIFT   3
153 #define LVL_CLK_DIV     (1UL << LVL_CLK_SHIFT)
154 #define LVL_CLK_MASK    (LVL_CLK_DIV - 1)
155 #define LVL_SHIFT(n)    ((n) * LVL_CLK_SHIFT)
156 #define LVL_GRAN(n)     (1UL << LVL_SHIFT(n))
157 
158 /*
159  * The time start value for each level to select the bucket at enqueue
160  * time.
161  */
162 #define LVL_START(n)    ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
163 
164 /* Size of each clock level */
165 #define LVL_BITS        6
166 #define LVL_SIZE        (1UL << LVL_BITS)
167 #define LVL_MASK        (LVL_SIZE - 1)
168 #define LVL_OFFS(n)     ((n) * LVL_SIZE)
169 
170 /* Level depth */
171 #if HZ > 100
172 # define LVL_DEPTH      9
173 # else
174 # define LVL_DEPTH      8
175 #endif
176 
177 /* The cutoff (max. capacity of the wheel) */
178 #define WHEEL_TIMEOUT_CUTOFF    (LVL_START(LVL_DEPTH))
179 #define WHEEL_TIMEOUT_MAX       (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
180 
181 /*
182  * The resulting wheel size. If NOHZ is configured we allocate two
183  * wheels so we have a separate storage for the deferrable timers.
184  */
185 #define WHEEL_SIZE      (LVL_SIZE * LVL_DEPTH)
186 
187 #ifdef CONFIG_NO_HZ_COMMON
188 # define NR_BASES       2
189 # define BASE_STD       0
190 # define BASE_DEF       1
191 #else
192 # define NR_BASES       1
193 # define BASE_STD       0
194 # define BASE_DEF       0
195 #endif
196 
197 struct timer_base {
198         raw_spinlock_t          lock;
199         struct timer_list       *running_timer;
200         unsigned long           clk;
201         unsigned long           next_expiry;
202         unsigned int            cpu;
203         bool                    is_idle;
204         bool                    must_forward_clk;
205         DECLARE_BITMAP(pending_map, WHEEL_SIZE);
206         struct hlist_head       vectors[WHEEL_SIZE];
207 } ____cacheline_aligned;
208 
209 static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
210 
211 #ifdef CONFIG_NO_HZ_COMMON
212 
213 static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
214 static DEFINE_MUTEX(timer_keys_mutex);
215 
216 static void timer_update_keys(struct work_struct *work);
217 static DECLARE_WORK(timer_update_work, timer_update_keys);
218 
219 #ifdef CONFIG_SMP
220 unsigned int sysctl_timer_migration = 1;
221 
222 DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
223 
224 static void timers_update_migration(void)
225 {
226         if (sysctl_timer_migration && tick_nohz_active)
227                 static_branch_enable(&timers_migration_enabled);
228         else
229                 static_branch_disable(&timers_migration_enabled);
230 }
231 #else
232 static inline void timers_update_migration(void) { }
233 #endif /* !CONFIG_SMP */
234 
235 static void timer_update_keys(struct work_struct *work)
236 {
237         mutex_lock(&timer_keys_mutex);
238         timers_update_migration();
239         static_branch_enable(&timers_nohz_active);
240         mutex_unlock(&timer_keys_mutex);
241 }
242 
243 void timers_update_nohz(void)
244 {
245         schedule_work(&timer_update_work);
246 }
247 
248 int timer_migration_handler(struct ctl_table *table, int write,
249                             void __user *buffer, size_t *lenp,
250                             loff_t *ppos)
251 {
252         int ret;
253 
254         mutex_lock(&timer_keys_mutex);
255         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
256         if (!ret && write)
257                 timers_update_migration();
258         mutex_unlock(&timer_keys_mutex);
259         return ret;
260 }
261 
262 static inline bool is_timers_nohz_active(void)
263 {
264         return static_branch_unlikely(&timers_nohz_active);
265 }
266 #else
267 static inline bool is_timers_nohz_active(void) { return false; }
268 #endif /* NO_HZ_COMMON */
269 
270 static unsigned long round_jiffies_common(unsigned long j, int cpu,
271                 bool force_up)
272 {
273         int rem;
274         unsigned long original = j;
275 
276         /*
277          * We don't want all cpus firing their timers at once hitting the
278          * same lock or cachelines, so we skew each extra cpu with an extra
279          * 3 jiffies. This 3 jiffies came originally from the mm/ code which
280          * already did this.
281          * The skew is done by adding 3*cpunr, then round, then subtract this
282          * extra offset again.
283          */
284         j += cpu * 3;
285 
286         rem = j % HZ;
287 
288         /*
289          * If the target jiffie is just after a whole second (which can happen
290          * due to delays of the timer irq, long irq off times etc etc) then
291          * we should round down to the whole second, not up. Use 1/4th second
292          * as cutoff for this rounding as an extreme upper bound for this.
293          * But never round down if @force_up is set.
294          */
295         if (rem < HZ/4 && !force_up) /* round down */
296                 j = j - rem;
297         else /* round up */
298                 j = j - rem + HZ;
299 
300         /* now that we have rounded, subtract the extra skew again */
301         j -= cpu * 3;
302 
303         /*
304          * Make sure j is still in the future. Otherwise return the
305          * unmodified value.
306          */
307         return time_is_after_jiffies(j) ? j : original;
308 }
309 
310 /**
311  * __round_jiffies - function to round jiffies to a full second
312  * @j: the time in (absolute) jiffies that should be rounded
313  * @cpu: the processor number on which the timeout will happen
314  *
315  * __round_jiffies() rounds an absolute time in the future (in jiffies)
316  * up or down to (approximately) full seconds. This is useful for timers
317  * for which the exact time they fire does not matter too much, as long as
318  * they fire approximately every X seconds.
319  *
320  * By rounding these timers to whole seconds, all such timers will fire
321  * at the same time, rather than at various times spread out. The goal
322  * of this is to have the CPU wake up less, which saves power.
323  *
324  * The exact rounding is skewed for each processor to avoid all
325  * processors firing at the exact same time, which could lead
326  * to lock contention or spurious cache line bouncing.
327  *
328  * The return value is the rounded version of the @j parameter.
329  */
330 unsigned long __round_jiffies(unsigned long j, int cpu)
331 {
332         return round_jiffies_common(j, cpu, false);
333 }
334 EXPORT_SYMBOL_GPL(__round_jiffies);
335 
336 /**
337  * __round_jiffies_relative - function to round jiffies to a full second
338  * @j: the time in (relative) jiffies that should be rounded
339  * @cpu: the processor number on which the timeout will happen
340  *
341  * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
342  * up or down to (approximately) full seconds. This is useful for timers
343  * for which the exact time they fire does not matter too much, as long as
344  * they fire approximately every X seconds.
345  *
346  * By rounding these timers to whole seconds, all such timers will fire
347  * at the same time, rather than at various times spread out. The goal
348  * of this is to have the CPU wake up less, which saves power.
349  *
350  * The exact rounding is skewed for each processor to avoid all
351  * processors firing at the exact same time, which could lead
352  * to lock contention or spurious cache line bouncing.
353  *
354  * The return value is the rounded version of the @j parameter.
355  */
356 unsigned long __round_jiffies_relative(unsigned long j, int cpu)
357 {
358         unsigned long j0 = jiffies;
359 
360         /* Use j0 because jiffies might change while we run */
361         return round_jiffies_common(j + j0, cpu, false) - j0;
362 }
363 EXPORT_SYMBOL_GPL(__round_jiffies_relative);
364 
365 /**
366  * round_jiffies - function to round jiffies to a full second
367  * @j: the time in (absolute) jiffies that should be rounded
368  *
369  * round_jiffies() rounds an absolute time in the future (in jiffies)
370  * up or down to (approximately) full seconds. This is useful for timers
371  * for which the exact time they fire does not matter too much, as long as
372  * they fire approximately every X seconds.
373  *
374  * By rounding these timers to whole seconds, all such timers will fire
375  * at the same time, rather than at various times spread out. The goal
376  * of this is to have the CPU wake up less, which saves power.
377  *
378  * The return value is the rounded version of the @j parameter.
379  */
380 unsigned long round_jiffies(unsigned long j)
381 {
382         return round_jiffies_common(j, raw_smp_processor_id(), false);
383 }
384 EXPORT_SYMBOL_GPL(round_jiffies);
385 
386 /**
387  * round_jiffies_relative - function to round jiffies to a full second
388  * @j: the time in (relative) jiffies that should be rounded
389  *
390  * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
391  * up or down to (approximately) full seconds. This is useful for timers
392  * for which the exact time they fire does not matter too much, as long as
393  * they fire approximately every X seconds.
394  *
395  * By rounding these timers to whole seconds, all such timers will fire
396  * at the same time, rather than at various times spread out. The goal
397  * of this is to have the CPU wake up less, which saves power.
398  *
399  * The return value is the rounded version of the @j parameter.
400  */
401 unsigned long round_jiffies_relative(unsigned long j)
402 {
403         return __round_jiffies_relative(j, raw_smp_processor_id());
404 }
405 EXPORT_SYMBOL_GPL(round_jiffies_relative);
406 
407 /**
408  * __round_jiffies_up - function to round jiffies up to a full second
409  * @j: the time in (absolute) jiffies that should be rounded
410  * @cpu: the processor number on which the timeout will happen
411  *
412  * This is the same as __round_jiffies() except that it will never
413  * round down.  This is useful for timeouts for which the exact time
414  * of firing does not matter too much, as long as they don't fire too
415  * early.
416  */
417 unsigned long __round_jiffies_up(unsigned long j, int cpu)
418 {
419         return round_jiffies_common(j, cpu, true);
420 }
421 EXPORT_SYMBOL_GPL(__round_jiffies_up);
422 
423 /**
424  * __round_jiffies_up_relative - function to round jiffies up to a full second
425  * @j: the time in (relative) jiffies that should be rounded
426  * @cpu: the processor number on which the timeout will happen
427  *
428  * This is the same as __round_jiffies_relative() except that it will never
429  * round down.  This is useful for timeouts for which the exact time
430  * of firing does not matter too much, as long as they don't fire too
431  * early.
432  */
433 unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
434 {
435         unsigned long j0 = jiffies;
436 
437         /* Use j0 because jiffies might change while we run */
438         return round_jiffies_common(j + j0, cpu, true) - j0;
439 }
440 EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
441 
442 /**
443  * round_jiffies_up - function to round jiffies up to a full second
444  * @j: the time in (absolute) jiffies that should be rounded
445  *
446  * This is the same as round_jiffies() except that it will never
447  * round down.  This is useful for timeouts for which the exact time
448  * of firing does not matter too much, as long as they don't fire too
449  * early.
450  */
451 unsigned long round_jiffies_up(unsigned long j)
452 {
453         return round_jiffies_common(j, raw_smp_processor_id(), true);
454 }
455 EXPORT_SYMBOL_GPL(round_jiffies_up);
456 
457 /**
458  * round_jiffies_up_relative - function to round jiffies up to a full second
459  * @j: the time in (relative) jiffies that should be rounded
460  *
461  * This is the same as round_jiffies_relative() except that it will never
462  * round down.  This is useful for timeouts for which the exact time
463  * of firing does not matter too much, as long as they don't fire too
464  * early.
465  */
466 unsigned long round_jiffies_up_relative(unsigned long j)
467 {
468         return __round_jiffies_up_relative(j, raw_smp_processor_id());
469 }
470 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
471 
472 
473 static inline unsigned int timer_get_idx(struct timer_list *timer)
474 {
475         return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
476 }
477 
478 static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
479 {
480         timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
481                         idx << TIMER_ARRAYSHIFT;
482 }
483 
484 /*
485  * Helper function to calculate the array index for a given expiry
486  * time.
487  */
488 static inline unsigned calc_index(unsigned expires, unsigned lvl)
489 {
490         expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
491         return LVL_OFFS(lvl) + (expires & LVL_MASK);
492 }
493 
494 static int calc_wheel_index(unsigned long expires, unsigned long clk)
495 {
496         unsigned long delta = expires - clk;
497         unsigned int idx;
498 
499         if (delta < LVL_START(1)) {
500                 idx = calc_index(expires, 0);
501         } else if (delta < LVL_START(2)) {
502                 idx = calc_index(expires, 1);
503         } else if (delta < LVL_START(3)) {
504                 idx = calc_index(expires, 2);
505         } else if (delta < LVL_START(4)) {
506                 idx = calc_index(expires, 3);
507         } else if (delta < LVL_START(5)) {
508                 idx = calc_index(expires, 4);
509         } else if (delta < LVL_START(6)) {
510                 idx = calc_index(expires, 5);
511         } else if (delta < LVL_START(7)) {
512                 idx = calc_index(expires, 6);
513         } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
514                 idx = calc_index(expires, 7);
515         } else if ((long) delta < 0) {
516                 idx = clk & LVL_MASK;
517         } else {
518                 /*
519                  * Force expire obscene large timeouts to expire at the
520                  * capacity limit of the wheel.
521                  */
522                 if (expires >= WHEEL_TIMEOUT_CUTOFF)
523                         expires = WHEEL_TIMEOUT_MAX;
524 
525                 idx = calc_index(expires, LVL_DEPTH - 1);
526         }
527         return idx;
528 }
529 
530 /*
531  * Enqueue the timer into the hash bucket, mark it pending in
532  * the bitmap and store the index in the timer flags.
533  */
534 static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
535                           unsigned int idx)
536 {
537         hlist_add_head(&timer->entry, base->vectors + idx);
538         __set_bit(idx, base->pending_map);
539         timer_set_idx(timer, idx);
540 }
541 
542 static void
543 __internal_add_timer(struct timer_base *base, struct timer_list *timer)
544 {
545         unsigned int idx;
546 
547         idx = calc_wheel_index(timer->expires, base->clk);
548         enqueue_timer(base, timer, idx);
549 }
550 
551 static void
552 trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
553 {
554         if (!is_timers_nohz_active())
555                 return;
556 
557         /*
558          * TODO: This wants some optimizing similar to the code below, but we
559          * will do that when we switch from push to pull for deferrable timers.
560          */
561         if (timer->flags & TIMER_DEFERRABLE) {
562                 if (tick_nohz_full_cpu(base->cpu))
563                         wake_up_nohz_cpu(base->cpu);
564                 return;
565         }
566 
567         /*
568          * We might have to IPI the remote CPU if the base is idle and the
569          * timer is not deferrable. If the other CPU is on the way to idle
570          * then it can't set base->is_idle as we hold the base lock:
571          */
572         if (!base->is_idle)
573                 return;
574 
575         /* Check whether this is the new first expiring timer: */
576         if (time_after_eq(timer->expires, base->next_expiry))
577                 return;
578 
579         /*
580          * Set the next expiry time and kick the CPU so it can reevaluate the
581          * wheel:
582          */
583         base->next_expiry = timer->expires;
584                 wake_up_nohz_cpu(base->cpu);
585 }
586 
587 static void
588 internal_add_timer(struct timer_base *base, struct timer_list *timer)
589 {
590         __internal_add_timer(base, timer);
591         trigger_dyntick_cpu(base, timer);
592 }
593 
594 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
595 
596 static struct debug_obj_descr timer_debug_descr;
597 
598 static void *timer_debug_hint(void *addr)
599 {
600         return ((struct timer_list *) addr)->function;
601 }
602 
603 static bool timer_is_static_object(void *addr)
604 {
605         struct timer_list *timer = addr;
606 
607         return (timer->entry.pprev == NULL &&
608                 timer->entry.next == TIMER_ENTRY_STATIC);
609 }
610 
611 /*
612  * fixup_init is called when:
613  * - an active object is initialized
614  */
615 static bool timer_fixup_init(void *addr, enum debug_obj_state state)
616 {
617         struct timer_list *timer = addr;
618 
619         switch (state) {
620         case ODEBUG_STATE_ACTIVE:
621                 del_timer_sync(timer);
622                 debug_object_init(timer, &timer_debug_descr);
623                 return true;
624         default:
625                 return false;
626         }
627 }
628 
629 /* Stub timer callback for improperly used timers. */
630 static void stub_timer(struct timer_list *unused)
631 {
632         WARN_ON(1);
633 }
634 
635 /*
636  * fixup_activate is called when:
637  * - an active object is activated
638  * - an unknown non-static object is activated
639  */
640 static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
641 {
642         struct timer_list *timer = addr;
643 
644         switch (state) {
645         case ODEBUG_STATE_NOTAVAILABLE:
646                 timer_setup(timer, stub_timer, 0);
647                 return true;
648 
649         case ODEBUG_STATE_ACTIVE:
650                 WARN_ON(1);
651 
652         default:
653                 return false;
654         }
655 }
656 
657 /*
658  * fixup_free is called when:
659  * - an active object is freed
660  */
661 static bool timer_fixup_free(void *addr, enum debug_obj_state state)
662 {
663         struct timer_list *timer = addr;
664 
665         switch (state) {
666         case ODEBUG_STATE_ACTIVE:
667                 del_timer_sync(timer);
668                 debug_object_free(timer, &timer_debug_descr);
669                 return true;
670         default:
671                 return false;
672         }
673 }
674 
675 /*
676  * fixup_assert_init is called when:
677  * - an untracked/uninit-ed object is found
678  */
679 static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
680 {
681         struct timer_list *timer = addr;
682 
683         switch (state) {
684         case ODEBUG_STATE_NOTAVAILABLE:
685                 timer_setup(timer, stub_timer, 0);
686                 return true;
687         default:
688                 return false;
689         }
690 }
691 
692 static struct debug_obj_descr timer_debug_descr = {
693         .name                   = "timer_list",
694         .debug_hint             = timer_debug_hint,
695         .is_static_object       = timer_is_static_object,
696         .fixup_init             = timer_fixup_init,
697         .fixup_activate         = timer_fixup_activate,
698         .fixup_free             = timer_fixup_free,
699         .fixup_assert_init      = timer_fixup_assert_init,
700 };
701 
702 static inline void debug_timer_init(struct timer_list *timer)
703 {
704         debug_object_init(timer, &timer_debug_descr);
705 }
706 
707 static inline void debug_timer_activate(struct timer_list *timer)
708 {
709         debug_object_activate(timer, &timer_debug_descr);
710 }
711 
712 static inline void debug_timer_deactivate(struct timer_list *timer)
713 {
714         debug_object_deactivate(timer, &timer_debug_descr);
715 }
716 
717 static inline void debug_timer_free(struct timer_list *timer)
718 {
719         debug_object_free(timer, &timer_debug_descr);
720 }
721 
722 static inline void debug_timer_assert_init(struct timer_list *timer)
723 {
724         debug_object_assert_init(timer, &timer_debug_descr);
725 }
726 
727 static void do_init_timer(struct timer_list *timer,
728                           void (*func)(struct timer_list *),
729                           unsigned int flags,
730                           const char *name, struct lock_class_key *key);
731 
732 void init_timer_on_stack_key(struct timer_list *timer,
733                              void (*func)(struct timer_list *),
734                              unsigned int flags,
735                              const char *name, struct lock_class_key *key)
736 {
737         debug_object_init_on_stack(timer, &timer_debug_descr);
738         do_init_timer(timer, func, flags, name, key);
739 }
740 EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
741 
742 void destroy_timer_on_stack(struct timer_list *timer)
743 {
744         debug_object_free(timer, &timer_debug_descr);
745 }
746 EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
747 
748 #else
749 static inline void debug_timer_init(struct timer_list *timer) { }
750 static inline void debug_timer_activate(struct timer_list *timer) { }
751 static inline void debug_timer_deactivate(struct timer_list *timer) { }
752 static inline void debug_timer_assert_init(struct timer_list *timer) { }
753 #endif
754 
755 static inline void debug_init(struct timer_list *timer)
756 {
757         debug_timer_init(timer);
758         trace_timer_init(timer);
759 }
760 
761 static inline void
762 debug_activate(struct timer_list *timer, unsigned long expires)
763 {
764         debug_timer_activate(timer);
765         trace_timer_start(timer, expires, timer->flags);
766 }
767 
768 static inline void debug_deactivate(struct timer_list *timer)
769 {
770         debug_timer_deactivate(timer);
771         trace_timer_cancel(timer);
772 }
773 
774 static inline void debug_assert_init(struct timer_list *timer)
775 {
776         debug_timer_assert_init(timer);
777 }
778 
779 static void do_init_timer(struct timer_list *timer,
780                           void (*func)(struct timer_list *),
781                           unsigned int flags,
782                           const char *name, struct lock_class_key *key)
783 {
784         timer->entry.pprev = NULL;
785         timer->function = func;
786         timer->flags = flags | raw_smp_processor_id();
787         lockdep_init_map(&timer->lockdep_map, name, key, 0);
788 }
789 
790 /**
791  * init_timer_key - initialize a timer
792  * @timer: the timer to be initialized
793  * @func: timer callback function
794  * @flags: timer flags
795  * @name: name of the timer
796  * @key: lockdep class key of the fake lock used for tracking timer
797  *       sync lock dependencies
798  *
799  * init_timer_key() must be done to a timer prior calling *any* of the
800  * other timer functions.
801  */
802 void init_timer_key(struct timer_list *timer,
803                     void (*func)(struct timer_list *), unsigned int flags,
804                     const char *name, struct lock_class_key *key)
805 {
806         debug_init(timer);
807         do_init_timer(timer, func, flags, name, key);
808 }
809 EXPORT_SYMBOL(init_timer_key);
810 
811 static inline void detach_timer(struct timer_list *timer, bool clear_pending)
812 {
813         struct hlist_node *entry = &timer->entry;
814 
815         debug_deactivate(timer);
816 
817         __hlist_del(entry);
818         if (clear_pending)
819                 entry->pprev = NULL;
820         entry->next = LIST_POISON2;
821 }
822 
823 static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
824                              bool clear_pending)
825 {
826         unsigned idx = timer_get_idx(timer);
827 
828         if (!timer_pending(timer))
829                 return 0;
830 
831         if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
832                 __clear_bit(idx, base->pending_map);
833 
834         detach_timer(timer, clear_pending);
835         return 1;
836 }
837 
838 static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
839 {
840         struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
841 
842         /*
843          * If the timer is deferrable and NO_HZ_COMMON is set then we need
844          * to use the deferrable base.
845          */
846         if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
847                 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
848         return base;
849 }
850 
851 static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
852 {
853         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
854 
855         /*
856          * If the timer is deferrable and NO_HZ_COMMON is set then we need
857          * to use the deferrable base.
858          */
859         if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
860                 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
861         return base;
862 }
863 
864 static inline struct timer_base *get_timer_base(u32 tflags)
865 {
866         return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
867 }
868 
869 static inline struct timer_base *
870 get_target_base(struct timer_base *base, unsigned tflags)
871 {
872 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
873         if (static_branch_likely(&timers_migration_enabled) &&
874             !(tflags & TIMER_PINNED))
875                 return get_timer_cpu_base(tflags, get_nohz_timer_target());
876 #endif
877         return get_timer_this_cpu_base(tflags);
878 }
879 
880 static inline void forward_timer_base(struct timer_base *base)
881 {
882 #ifdef CONFIG_NO_HZ_COMMON
883         unsigned long jnow;
884 
885         /*
886          * We only forward the base when we are idle or have just come out of
887          * idle (must_forward_clk logic), and have a delta between base clock
888          * and jiffies. In the common case, run_timers will take care of it.
889          */
890         if (likely(!base->must_forward_clk))
891                 return;
892 
893         jnow = READ_ONCE(jiffies);
894         base->must_forward_clk = base->is_idle;
895         if ((long)(jnow - base->clk) < 2)
896                 return;
897 
898         /*
899          * If the next expiry value is > jiffies, then we fast forward to
900          * jiffies otherwise we forward to the next expiry value.
901          */
902         if (time_after(base->next_expiry, jnow))
903                 base->clk = jnow;
904         else
905                 base->clk = base->next_expiry;
906 #endif
907 }
908 
909 
910 /*
911  * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
912  * that all timers which are tied to this base are locked, and the base itself
913  * is locked too.
914  *
915  * So __run_timers/migrate_timers can safely modify all timers which could
916  * be found in the base->vectors array.
917  *
918  * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
919  * to wait until the migration is done.
920  */
921 static struct timer_base *lock_timer_base(struct timer_list *timer,
922                                           unsigned long *flags)
923         __acquires(timer->base->lock)
924 {
925         for (;;) {
926                 struct timer_base *base;
927                 u32 tf;
928 
929                 /*
930                  * We need to use READ_ONCE() here, otherwise the compiler
931                  * might re-read @tf between the check for TIMER_MIGRATING
932                  * and spin_lock().
933                  */
934                 tf = READ_ONCE(timer->flags);
935 
936                 if (!(tf & TIMER_MIGRATING)) {
937                         base = get_timer_base(tf);
938                         raw_spin_lock_irqsave(&base->lock, *flags);
939                         if (timer->flags == tf)
940                                 return base;
941                         raw_spin_unlock_irqrestore(&base->lock, *flags);
942                 }
943                 cpu_relax();
944         }
945 }
946 
947 #define MOD_TIMER_PENDING_ONLY          0x01
948 #define MOD_TIMER_REDUCE                0x02
949 
950 static inline int
951 __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
952 {
953         struct timer_base *base, *new_base;
954         unsigned int idx = UINT_MAX;
955         unsigned long clk = 0, flags;
956         int ret = 0;
957 
958         BUG_ON(!timer->function);
959 
960         /*
961          * This is a common optimization triggered by the networking code - if
962          * the timer is re-modified to have the same timeout or ends up in the
963          * same array bucket then just return:
964          */
965         if (timer_pending(timer)) {
966                 /*
967                  * The downside of this optimization is that it can result in
968                  * larger granularity than you would get from adding a new
969                  * timer with this expiry.
970                  */
971                 long diff = timer->expires - expires;
972 
973                 if (!diff)
974                         return 1;
975                 if (options & MOD_TIMER_REDUCE && diff <= 0)
976                         return 1;
977 
978                 /*
979                  * We lock timer base and calculate the bucket index right
980                  * here. If the timer ends up in the same bucket, then we
981                  * just update the expiry time and avoid the whole
982                  * dequeue/enqueue dance.
983                  */
984                 base = lock_timer_base(timer, &flags);
985                 forward_timer_base(base);
986 
987                 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
988                     time_before_eq(timer->expires, expires)) {
989                         ret = 1;
990                         goto out_unlock;
991                 }
992 
993                 clk = base->clk;
994                 idx = calc_wheel_index(expires, clk);
995 
996                 /*
997                  * Retrieve and compare the array index of the pending
998                  * timer. If it matches set the expiry to the new value so a
999                  * subsequent call will exit in the expires check above.
1000                  */
1001                 if (idx == timer_get_idx(timer)) {
1002                         if (!(options & MOD_TIMER_REDUCE))
1003                                 timer->expires = expires;
1004                         else if (time_after(timer->expires, expires))
1005                                 timer->expires = expires;
1006                         ret = 1;
1007                         goto out_unlock;
1008                 }
1009         } else {
1010                 base = lock_timer_base(timer, &flags);
1011                 forward_timer_base(base);
1012         }
1013 
1014         ret = detach_if_pending(timer, base, false);
1015         if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1016                 goto out_unlock;
1017 
1018         new_base = get_target_base(base, timer->flags);
1019 
1020         if (base != new_base) {
1021                 /*
1022                  * We are trying to schedule the timer on the new base.
1023                  * However we can't change timer's base while it is running,
1024                  * otherwise del_timer_sync() can't detect that the timer's
1025                  * handler yet has not finished. This also guarantees that the
1026                  * timer is serialized wrt itself.
1027                  */
1028                 if (likely(base->running_timer != timer)) {
1029                         /* See the comment in lock_timer_base() */
1030                         timer->flags |= TIMER_MIGRATING;
1031 
1032                         raw_spin_unlock(&base->lock);
1033                         base = new_base;
1034                         raw_spin_lock(&base->lock);
1035                         WRITE_ONCE(timer->flags,
1036                                    (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1037                         forward_timer_base(base);
1038                 }
1039         }
1040 
1041         debug_activate(timer, expires);
1042 
1043         timer->expires = expires;
1044         /*
1045          * If 'idx' was calculated above and the base time did not advance
1046          * between calculating 'idx' and possibly switching the base, only
1047          * enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
1048          * we need to (re)calculate the wheel index via
1049          * internal_add_timer().
1050          */
1051         if (idx != UINT_MAX && clk == base->clk) {
1052                 enqueue_timer(base, timer, idx);
1053                 trigger_dyntick_cpu(base, timer);
1054         } else {
1055                 internal_add_timer(base, timer);
1056         }
1057 
1058 out_unlock:
1059         raw_spin_unlock_irqrestore(&base->lock, flags);
1060 
1061         return ret;
1062 }
1063 
1064 /**
1065  * mod_timer_pending - modify a pending timer's timeout
1066  * @timer: the pending timer to be modified
1067  * @expires: new timeout in jiffies
1068  *
1069  * mod_timer_pending() is the same for pending timers as mod_timer(),
1070  * but will not re-activate and modify already deleted timers.
1071  *
1072  * It is useful for unserialized use of timers.
1073  */
1074 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1075 {
1076         return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1077 }
1078 EXPORT_SYMBOL(mod_timer_pending);
1079 
1080 /**
1081  * mod_timer - modify a timer's timeout
1082  * @timer: the timer to be modified
1083  * @expires: new timeout in jiffies
1084  *
1085  * mod_timer() is a more efficient way to update the expire field of an
1086  * active timer (if the timer is inactive it will be activated)
1087  *
1088  * mod_timer(timer, expires) is equivalent to:
1089  *
1090  *     del_timer(timer); timer->expires = expires; add_timer(timer);
1091  *
1092  * Note that if there are multiple unserialized concurrent users of the
1093  * same timer, then mod_timer() is the only safe way to modify the timeout,
1094  * since add_timer() cannot modify an already running timer.
1095  *
1096  * The function returns whether it has modified a pending timer or not.
1097  * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1098  * active timer returns 1.)
1099  */
1100 int mod_timer(struct timer_list *timer, unsigned long expires)
1101 {
1102         return __mod_timer(timer, expires, 0);
1103 }
1104 EXPORT_SYMBOL(mod_timer);
1105 
1106 /**
1107  * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1108  * @timer:      The timer to be modified
1109  * @expires:    New timeout in jiffies
1110  *
1111  * timer_reduce() is very similar to mod_timer(), except that it will only
1112  * modify a running timer if that would reduce the expiration time (it will
1113  * start a timer that isn't running).
1114  */
1115 int timer_reduce(struct timer_list *timer, unsigned long expires)
1116 {
1117         return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1118 }
1119 EXPORT_SYMBOL(timer_reduce);
1120 
1121 /**
1122  * add_timer - start a timer
1123  * @timer: the timer to be added
1124  *
1125  * The kernel will do a ->function(@timer) callback from the
1126  * timer interrupt at the ->expires point in the future. The
1127  * current time is 'jiffies'.
1128  *
1129  * The timer's ->expires, ->function fields must be set prior calling this
1130  * function.
1131  *
1132  * Timers with an ->expires field in the past will be executed in the next
1133  * timer tick.
1134  */
1135 void add_timer(struct timer_list *timer)
1136 {
1137         BUG_ON(timer_pending(timer));
1138         mod_timer(timer, timer->expires);
1139 }
1140 EXPORT_SYMBOL(add_timer);
1141 
1142 /**
1143  * add_timer_on - start a timer on a particular CPU
1144  * @timer: the timer to be added
1145  * @cpu: the CPU to start it on
1146  *
1147  * This is not very scalable on SMP. Double adds are not possible.
1148  */
1149 void add_timer_on(struct timer_list *timer, int cpu)
1150 {
1151         struct timer_base *new_base, *base;
1152         unsigned long flags;
1153 
1154         BUG_ON(timer_pending(timer) || !timer->function);
1155 
1156         new_base = get_timer_cpu_base(timer->flags, cpu);
1157 
1158         /*
1159          * If @timer was on a different CPU, it should be migrated with the
1160          * old base locked to prevent other operations proceeding with the
1161          * wrong base locked.  See lock_timer_base().
1162          */
1163         base = lock_timer_base(timer, &flags);
1164         if (base != new_base) {
1165                 timer->flags |= TIMER_MIGRATING;
1166 
1167                 raw_spin_unlock(&base->lock);
1168                 base = new_base;
1169                 raw_spin_lock(&base->lock);
1170                 WRITE_ONCE(timer->flags,
1171                            (timer->flags & ~TIMER_BASEMASK) | cpu);
1172         }
1173         forward_timer_base(base);
1174 
1175         debug_activate(timer, timer->expires);
1176         internal_add_timer(base, timer);
1177         raw_spin_unlock_irqrestore(&base->lock, flags);
1178 }
1179 EXPORT_SYMBOL_GPL(add_timer_on);
1180 
1181 /**
1182  * del_timer - deactivate a timer.
1183  * @timer: the timer to be deactivated
1184  *
1185  * del_timer() deactivates a timer - this works on both active and inactive
1186  * timers.
1187  *
1188  * The function returns whether it has deactivated a pending timer or not.
1189  * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1190  * active timer returns 1.)
1191  */
1192 int del_timer(struct timer_list *timer)
1193 {
1194         struct timer_base *base;
1195         unsigned long flags;
1196         int ret = 0;
1197 
1198         debug_assert_init(timer);
1199 
1200         if (timer_pending(timer)) {
1201                 base = lock_timer_base(timer, &flags);
1202                 ret = detach_if_pending(timer, base, true);
1203                 raw_spin_unlock_irqrestore(&base->lock, flags);
1204         }
1205 
1206         return ret;
1207 }
1208 EXPORT_SYMBOL(del_timer);
1209 
1210 /**
1211  * try_to_del_timer_sync - Try to deactivate a timer
1212  * @timer: timer to delete
1213  *
1214  * This function tries to deactivate a timer. Upon successful (ret >= 0)
1215  * exit the timer is not queued and the handler is not running on any CPU.
1216  */
1217 int try_to_del_timer_sync(struct timer_list *timer)
1218 {
1219         struct timer_base *base;
1220         unsigned long flags;
1221         int ret = -1;
1222 
1223         debug_assert_init(timer);
1224 
1225         base = lock_timer_base(timer, &flags);
1226 
1227         if (base->running_timer != timer)
1228                 ret = detach_if_pending(timer, base, true);
1229 
1230         raw_spin_unlock_irqrestore(&base->lock, flags);
1231 
1232         return ret;
1233 }
1234 EXPORT_SYMBOL(try_to_del_timer_sync);
1235 
1236 #ifdef CONFIG_SMP
1237 /**
1238  * del_timer_sync - deactivate a timer and wait for the handler to finish.
1239  * @timer: the timer to be deactivated
1240  *
1241  * This function only differs from del_timer() on SMP: besides deactivating
1242  * the timer it also makes sure the handler has finished executing on other
1243  * CPUs.
1244  *
1245  * Synchronization rules: Callers must prevent restarting of the timer,
1246  * otherwise this function is meaningless. It must not be called from
1247  * interrupt contexts unless the timer is an irqsafe one. The caller must
1248  * not hold locks which would prevent completion of the timer's
1249  * handler. The timer's handler must not call add_timer_on(). Upon exit the
1250  * timer is not queued and the handler is not running on any CPU.
1251  *
1252  * Note: For !irqsafe timers, you must not hold locks that are held in
1253  *   interrupt context while calling this function. Even if the lock has
1254  *   nothing to do with the timer in question.  Here's why:
1255  *
1256  *    CPU0                             CPU1
1257  *    ----                             ----
1258  *                                   <SOFTIRQ>
1259  *                                   call_timer_fn();
1260  *                                     base->running_timer = mytimer;
1261  *  spin_lock_irq(somelock);
1262  *                                     <IRQ>
1263  *                                        spin_lock(somelock);
1264  *  del_timer_sync(mytimer);
1265  *   while (base->running_timer == mytimer);
1266  *
1267  * Now del_timer_sync() will never return and never release somelock.
1268  * The interrupt on the other CPU is waiting to grab somelock but
1269  * it has interrupted the softirq that CPU0 is waiting to finish.
1270  *
1271  * The function returns whether it has deactivated a pending timer or not.
1272  */
1273 int del_timer_sync(struct timer_list *timer)
1274 {
1275 #ifdef CONFIG_LOCKDEP
1276         unsigned long flags;
1277 
1278         /*
1279          * If lockdep gives a backtrace here, please reference
1280          * the synchronization rules above.
1281          */
1282         local_irq_save(flags);
1283         lock_map_acquire(&timer->lockdep_map);
1284         lock_map_release(&timer->lockdep_map);
1285         local_irq_restore(flags);
1286 #endif
1287         /*
1288          * don't use it in hardirq context, because it
1289          * could lead to deadlock.
1290          */
1291         WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1292         for (;;) {
1293                 int ret = try_to_del_timer_sync(timer);
1294                 if (ret >= 0)
1295                         return ret;
1296                 cpu_relax();
1297         }
1298 }
1299 EXPORT_SYMBOL(del_timer_sync);
1300 #endif
1301 
1302 static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list *))
1303 {
1304         int count = preempt_count();
1305 
1306 #ifdef CONFIG_LOCKDEP
1307         /*
1308          * It is permissible to free the timer from inside the
1309          * function that is called from it, this we need to take into
1310          * account for lockdep too. To avoid bogus "held lock freed"
1311          * warnings as well as problems when looking into
1312          * timer->lockdep_map, make a copy and use that here.
1313          */
1314         struct lockdep_map lockdep_map;
1315 
1316         lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1317 #endif
1318         /*
1319          * Couple the lock chain with the lock chain at
1320          * del_timer_sync() by acquiring the lock_map around the fn()
1321          * call here and in del_timer_sync().
1322          */
1323         lock_map_acquire(&lockdep_map);
1324 
1325         trace_timer_expire_entry(timer);
1326         fn(timer);
1327         trace_timer_expire_exit(timer);
1328 
1329         lock_map_release(&lockdep_map);
1330 
1331         if (count != preempt_count()) {
1332                 WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1333                           fn, count, preempt_count());
1334                 /*
1335                  * Restore the preempt count. That gives us a decent
1336                  * chance to survive and extract information. If the
1337                  * callback kept a lock held, bad luck, but not worse
1338                  * than the BUG() we had.
1339                  */
1340                 preempt_count_set(count);
1341         }
1342 }
1343 
1344 static void expire_timers(struct timer_base *base, struct hlist_head *head)
1345 {
1346         while (!hlist_empty(head)) {
1347                 struct timer_list *timer;
1348                 void (*fn)(struct timer_list *);
1349 
1350                 timer = hlist_entry(head->first, struct timer_list, entry);
1351 
1352                 base->running_timer = timer;
1353                 detach_timer(timer, true);
1354 
1355                 fn = timer->function;
1356 
1357                 if (timer->flags & TIMER_IRQSAFE) {
1358                         raw_spin_unlock(&base->lock);
1359                         call_timer_fn(timer, fn);
1360                         raw_spin_lock(&base->lock);
1361                 } else {
1362                         raw_spin_unlock_irq(&base->lock);
1363                         call_timer_fn(timer, fn);
1364                         raw_spin_lock_irq(&base->lock);
1365                 }
1366         }
1367 }
1368 
1369 static int __collect_expired_timers(struct timer_base *base,
1370                                     struct hlist_head *heads)
1371 {
1372         unsigned long clk = base->clk;
1373         struct hlist_head *vec;
1374         int i, levels = 0;
1375         unsigned int idx;
1376 
1377         for (i = 0; i < LVL_DEPTH; i++) {
1378                 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1379 
1380                 if (__test_and_clear_bit(idx, base->pending_map)) {
1381                         vec = base->vectors + idx;
1382                         hlist_move_list(vec, heads++);
1383                         levels++;
1384                 }
1385                 /* Is it time to look at the next level? */
1386                 if (clk & LVL_CLK_MASK)
1387                         break;
1388                 /* Shift clock for the next level granularity */
1389                 clk >>= LVL_CLK_SHIFT;
1390         }
1391         return levels;
1392 }
1393 
1394 #ifdef CONFIG_NO_HZ_COMMON
1395 /*
1396  * Find the next pending bucket of a level. Search from level start (@offset)
1397  * + @clk upwards and if nothing there, search from start of the level
1398  * (@offset) up to @offset + clk.
1399  */
1400 static int next_pending_bucket(struct timer_base *base, unsigned offset,
1401                                unsigned clk)
1402 {
1403         unsigned pos, start = offset + clk;
1404         unsigned end = offset + LVL_SIZE;
1405 
1406         pos = find_next_bit(base->pending_map, end, start);
1407         if (pos < end)
1408                 return pos - start;
1409 
1410         pos = find_next_bit(base->pending_map, start, offset);
1411         return pos < start ? pos + LVL_SIZE - start : -1;
1412 }
1413 
1414 /*
1415  * Search the first expiring timer in the various clock levels. Caller must
1416  * hold base->lock.
1417  */
1418 static unsigned long __next_timer_interrupt(struct timer_base *base)
1419 {
1420         unsigned long clk, next, adj;
1421         unsigned lvl, offset = 0;
1422 
1423         next = base->clk + NEXT_TIMER_MAX_DELTA;
1424         clk = base->clk;
1425         for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1426                 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1427 
1428                 if (pos >= 0) {
1429                         unsigned long tmp = clk + (unsigned long) pos;
1430 
1431                         tmp <<= LVL_SHIFT(lvl);
1432                         if (time_before(tmp, next))
1433                                 next = tmp;
1434                 }
1435                 /*
1436                  * Clock for the next level. If the current level clock lower
1437                  * bits are zero, we look at the next level as is. If not we
1438                  * need to advance it by one because that's going to be the
1439                  * next expiring bucket in that level. base->clk is the next
1440                  * expiring jiffie. So in case of:
1441                  *
1442                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1443                  *  0    0    0    0    0    0
1444                  *
1445                  * we have to look at all levels @index 0. With
1446                  *
1447                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1448                  *  0    0    0    0    0    2
1449                  *
1450                  * LVL0 has the next expiring bucket @index 2. The upper
1451                  * levels have the next expiring bucket @index 1.
1452                  *
1453                  * In case that the propagation wraps the next level the same
1454                  * rules apply:
1455                  *
1456                  * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1457                  *  0    0    0    0    F    2
1458                  *
1459                  * So after looking at LVL0 we get:
1460                  *
1461                  * LVL5 LVL4 LVL3 LVL2 LVL1
1462                  *  0    0    0    1    0
1463                  *
1464                  * So no propagation from LVL1 to LVL2 because that happened
1465                  * with the add already, but then we need to propagate further
1466                  * from LVL2 to LVL3.
1467                  *
1468                  * So the simple check whether the lower bits of the current
1469                  * level are 0 or not is sufficient for all cases.
1470                  */
1471                 adj = clk & LVL_CLK_MASK ? 1 : 0;
1472                 clk >>= LVL_CLK_SHIFT;
1473                 clk += adj;
1474         }
1475         return next;
1476 }
1477 
1478 /*
1479  * Check, if the next hrtimer event is before the next timer wheel
1480  * event:
1481  */
1482 static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1483 {
1484         u64 nextevt = hrtimer_get_next_event();
1485 
1486         /*
1487          * If high resolution timers are enabled
1488          * hrtimer_get_next_event() returns KTIME_MAX.
1489          */
1490         if (expires <= nextevt)
1491                 return expires;
1492 
1493         /*
1494          * If the next timer is already expired, return the tick base
1495          * time so the tick is fired immediately.
1496          */
1497         if (nextevt <= basem)
1498                 return basem;
1499 
1500         /*
1501          * Round up to the next jiffie. High resolution timers are
1502          * off, so the hrtimers are expired in the tick and we need to
1503          * make sure that this tick really expires the timer to avoid
1504          * a ping pong of the nohz stop code.
1505          *
1506          * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1507          */
1508         return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1509 }
1510 
1511 /**
1512  * get_next_timer_interrupt - return the time (clock mono) of the next timer
1513  * @basej:      base time jiffies
1514  * @basem:      base time clock monotonic
1515  *
1516  * Returns the tick aligned clock monotonic time of the next pending
1517  * timer or KTIME_MAX if no timer is pending.
1518  */
1519 u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1520 {
1521         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1522         u64 expires = KTIME_MAX;
1523         unsigned long nextevt;
1524         bool is_max_delta;
1525 
1526         /*
1527          * Pretend that there is no timer pending if the cpu is offline.
1528          * Possible pending timers will be migrated later to an active cpu.
1529          */
1530         if (cpu_is_offline(smp_processor_id()))
1531                 return expires;
1532 
1533         raw_spin_lock(&base->lock);
1534         nextevt = __next_timer_interrupt(base);
1535         is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
1536         base->next_expiry = nextevt;
1537         /*
1538          * We have a fresh next event. Check whether we can forward the
1539          * base. We can only do that when @basej is past base->clk
1540          * otherwise we might rewind base->clk.
1541          */
1542         if (time_after(basej, base->clk)) {
1543                 if (time_after(nextevt, basej))
1544                         base->clk = basej;
1545                 else if (time_after(nextevt, base->clk))
1546                         base->clk = nextevt;
1547         }
1548 
1549         if (time_before_eq(nextevt, basej)) {
1550                 expires = basem;
1551                 base->is_idle = false;
1552         } else {
1553                 if (!is_max_delta)
1554                         expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1555                 /*
1556                  * If we expect to sleep more than a tick, mark the base idle.
1557                  * Also the tick is stopped so any added timer must forward
1558                  * the base clk itself to keep granularity small. This idle
1559                  * logic is only maintained for the BASE_STD base, deferrable
1560                  * timers may still see large granularity skew (by design).
1561                  */
1562                 if ((expires - basem) > TICK_NSEC) {
1563                         base->must_forward_clk = true;
1564                         base->is_idle = true;
1565                 }
1566         }
1567         raw_spin_unlock(&base->lock);
1568 
1569         return cmp_next_hrtimer_event(basem, expires);
1570 }
1571 
1572 /**
1573  * timer_clear_idle - Clear the idle state of the timer base
1574  *
1575  * Called with interrupts disabled
1576  */
1577 void timer_clear_idle(void)
1578 {
1579         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1580 
1581         /*
1582          * We do this unlocked. The worst outcome is a remote enqueue sending
1583          * a pointless IPI, but taking the lock would just make the window for
1584          * sending the IPI a few instructions smaller for the cost of taking
1585          * the lock in the exit from idle path.
1586          */
1587         base->is_idle = false;
1588 }
1589 
1590 static int collect_expired_timers(struct timer_base *base,
1591                                   struct hlist_head *heads)
1592 {
1593         /*
1594          * NOHZ optimization. After a long idle sleep we need to forward the
1595          * base to current jiffies. Avoid a loop by searching the bitfield for
1596          * the next expiring timer.
1597          */
1598         if ((long)(jiffies - base->clk) > 2) {
1599                 unsigned long next = __next_timer_interrupt(base);
1600 
1601                 /*
1602                  * If the next timer is ahead of time forward to current
1603                  * jiffies, otherwise forward to the next expiry time:
1604                  */
1605                 if (time_after(next, jiffies)) {
1606                         /*
1607                          * The call site will increment base->clk and then
1608                          * terminate the expiry loop immediately.
1609                          */
1610                         base->clk = jiffies;
1611                         return 0;
1612                 }
1613                 base->clk = next;
1614         }
1615         return __collect_expired_timers(base, heads);
1616 }
1617 #else
1618 static inline int collect_expired_timers(struct timer_base *base,
1619                                          struct hlist_head *heads)
1620 {
1621         return __collect_expired_timers(base, heads);
1622 }
1623 #endif
1624 
1625 /*
1626  * Called from the timer interrupt handler to charge one tick to the current
1627  * process.  user_tick is 1 if the tick is user time, 0 for system.
1628  */
1629 void update_process_times(int user_tick)
1630 {
1631         struct task_struct *p = current;
1632 
1633         /* Note: this timer irq context must be accounted for as well. */
1634         account_process_tick(p, user_tick);
1635         run_local_timers();
1636         rcu_check_callbacks(user_tick);
1637 #ifdef CONFIG_IRQ_WORK
1638         if (in_irq())
1639                 irq_work_tick();
1640 #endif
1641         scheduler_tick();
1642         if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1643                 run_posix_cpu_timers(p);
1644 }
1645 
1646 /**
1647  * __run_timers - run all expired timers (if any) on this CPU.
1648  * @base: the timer vector to be processed.
1649  */
1650 static inline void __run_timers(struct timer_base *base)
1651 {
1652         struct hlist_head heads[LVL_DEPTH];
1653         int levels;
1654 
1655         if (!time_after_eq(jiffies, base->clk))
1656                 return;
1657 
1658         raw_spin_lock_irq(&base->lock);
1659 
1660         while (time_after_eq(jiffies, base->clk)) {
1661 
1662                 levels = collect_expired_timers(base, heads);
1663                 base->clk++;
1664 
1665                 while (levels--)
1666                         expire_timers(base, heads + levels);
1667         }
1668         base->running_timer = NULL;
1669         raw_spin_unlock_irq(&base->lock);
1670 }
1671 
1672 /*
1673  * This function runs timers and the timer-tq in bottom half context.
1674  */
1675 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1676 {
1677         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1678 
1679         /*
1680          * must_forward_clk must be cleared before running timers so that any
1681          * timer functions that call mod_timer will not try to forward the
1682          * base. idle trcking / clock forwarding logic is only used with
1683          * BASE_STD timers.
1684          *
1685          * The deferrable base does not do idle tracking at all, so we do
1686          * not forward it. This can result in very large variations in
1687          * granularity for deferrable timers, but they can be deferred for
1688          * long periods due to idle.
1689          */
1690         base->must_forward_clk = false;
1691 
1692         __run_timers(base);
1693         if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1694                 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1695 }
1696 
1697 /*
1698  * Called by the local, per-CPU timer interrupt on SMP.
1699  */
1700 void run_local_timers(void)
1701 {
1702         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1703 
1704         hrtimer_run_queues();
1705         /* Raise the softirq only if required. */
1706         if (time_before(jiffies, base->clk)) {
1707                 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1708                         return;
1709                 /* CPU is awake, so check the deferrable base. */
1710                 base++;
1711                 if (time_before(jiffies, base->clk))
1712                         return;
1713         }
1714         raise_softirq(TIMER_SOFTIRQ);
1715 }
1716 
1717 /*
1718  * Since schedule_timeout()'s timer is defined on the stack, it must store
1719  * the target task on the stack as well.
1720  */
1721 struct process_timer {
1722         struct timer_list timer;
1723         struct task_struct *task;
1724 };
1725 
1726 static void process_timeout(struct timer_list *t)
1727 {
1728         struct process_timer *timeout = from_timer(timeout, t, timer);
1729 
1730         wake_up_process(timeout->task);
1731 }
1732 
1733 /**
1734  * schedule_timeout - sleep until timeout
1735  * @timeout: timeout value in jiffies
1736  *
1737  * Make the current task sleep until @timeout jiffies have
1738  * elapsed. The routine will return immediately unless
1739  * the current task state has been set (see set_current_state()).
1740  *
1741  * You can set the task state as follows -
1742  *
1743  * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1744  * pass before the routine returns unless the current task is explicitly
1745  * woken up, (e.g. by wake_up_process())".
1746  *
1747  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1748  * delivered to the current task or the current task is explicitly woken
1749  * up.
1750  *
1751  * The current task state is guaranteed to be TASK_RUNNING when this
1752  * routine returns.
1753  *
1754  * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1755  * the CPU away without a bound on the timeout. In this case the return
1756  * value will be %MAX_SCHEDULE_TIMEOUT.
1757  *
1758  * Returns 0 when the timer has expired otherwise the remaining time in
1759  * jiffies will be returned.  In all cases the return value is guaranteed
1760  * to be non-negative.
1761  */
1762 signed long __sched schedule_timeout(signed long timeout)
1763 {
1764         struct process_timer timer;
1765         unsigned long expire;
1766 
1767         switch (timeout)
1768         {
1769         case MAX_SCHEDULE_TIMEOUT:
1770                 /*
1771                  * These two special cases are useful to be comfortable
1772                  * in the caller. Nothing more. We could take
1773                  * MAX_SCHEDULE_TIMEOUT from one of the negative value
1774                  * but I' d like to return a valid offset (>=0) to allow
1775                  * the caller to do everything it want with the retval.
1776                  */
1777                 schedule();
1778                 goto out;
1779         default:
1780                 /*
1781                  * Another bit of PARANOID. Note that the retval will be
1782                  * 0 since no piece of kernel is supposed to do a check
1783                  * for a negative retval of schedule_timeout() (since it
1784                  * should never happens anyway). You just have the printk()
1785                  * that will tell you if something is gone wrong and where.
1786                  */
1787                 if (timeout < 0) {
1788                         printk(KERN_ERR "schedule_timeout: wrong timeout "
1789                                 "value %lx\n", timeout);
1790                         dump_stack();
1791                         current->state = TASK_RUNNING;
1792                         goto out;
1793                 }
1794         }
1795 
1796         expire = timeout + jiffies;
1797 
1798         timer.task = current;
1799         timer_setup_on_stack(&timer.timer, process_timeout, 0);
1800         __mod_timer(&timer.timer, expire, 0);
1801         schedule();
1802         del_singleshot_timer_sync(&timer.timer);
1803 
1804         /* Remove the timer from the object tracker */
1805         destroy_timer_on_stack(&timer.timer);
1806 
1807         timeout = expire - jiffies;
1808 
1809  out:
1810         return timeout < 0 ? 0 : timeout;
1811 }
1812 EXPORT_SYMBOL(schedule_timeout);
1813 
1814 /*
1815  * We can use __set_current_state() here because schedule_timeout() calls
1816  * schedule() unconditionally.
1817  */
1818 signed long __sched schedule_timeout_interruptible(signed long timeout)
1819 {
1820         __set_current_state(TASK_INTERRUPTIBLE);
1821         return schedule_timeout(timeout);
1822 }
1823 EXPORT_SYMBOL(schedule_timeout_interruptible);
1824 
1825 signed long __sched schedule_timeout_killable(signed long timeout)
1826 {
1827         __set_current_state(TASK_KILLABLE);
1828         return schedule_timeout(timeout);
1829 }
1830 EXPORT_SYMBOL(schedule_timeout_killable);
1831 
1832 signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1833 {
1834         __set_current_state(TASK_UNINTERRUPTIBLE);
1835         return schedule_timeout(timeout);
1836 }
1837 EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1838 
1839 /*
1840  * Like schedule_timeout_uninterruptible(), except this task will not contribute
1841  * to load average.
1842  */
1843 signed long __sched schedule_timeout_idle(signed long timeout)
1844 {
1845         __set_current_state(TASK_IDLE);
1846         return schedule_timeout(timeout);
1847 }
1848 EXPORT_SYMBOL(schedule_timeout_idle);
1849 
1850 #ifdef CONFIG_HOTPLUG_CPU
1851 static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1852 {
1853         struct timer_list *timer;
1854         int cpu = new_base->cpu;
1855 
1856         while (!hlist_empty(head)) {
1857                 timer = hlist_entry(head->first, struct timer_list, entry);
1858                 detach_timer(timer, false);
1859                 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1860                 internal_add_timer(new_base, timer);
1861         }
1862 }
1863 
1864 int timers_prepare_cpu(unsigned int cpu)
1865 {
1866         struct timer_base *base;
1867         int b;
1868 
1869         for (b = 0; b < NR_BASES; b++) {
1870                 base = per_cpu_ptr(&timer_bases[b], cpu);
1871                 base->clk = jiffies;
1872                 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
1873                 base->is_idle = false;
1874                 base->must_forward_clk = true;
1875         }
1876         return 0;
1877 }
1878 
1879 int timers_dead_cpu(unsigned int cpu)
1880 {
1881         struct timer_base *old_base;
1882         struct timer_base *new_base;
1883         int b, i;
1884 
1885         BUG_ON(cpu_online(cpu));
1886 
1887         for (b = 0; b < NR_BASES; b++) {
1888                 old_base = per_cpu_ptr(&timer_bases[b], cpu);
1889                 new_base = get_cpu_ptr(&timer_bases[b]);
1890                 /*
1891                  * The caller is globally serialized and nobody else
1892                  * takes two locks at once, deadlock is not possible.
1893                  */
1894                 raw_spin_lock_irq(&new_base->lock);
1895                 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1896 
1897                 /*
1898                  * The current CPUs base clock might be stale. Update it
1899                  * before moving the timers over.
1900                  */
1901                 forward_timer_base(new_base);
1902 
1903                 BUG_ON(old_base->running_timer);
1904 
1905                 for (i = 0; i < WHEEL_SIZE; i++)
1906                         migrate_timer_list(new_base, old_base->vectors + i);
1907 
1908                 raw_spin_unlock(&old_base->lock);
1909                 raw_spin_unlock_irq(&new_base->lock);
1910                 put_cpu_ptr(&timer_bases);
1911         }
1912         return 0;
1913 }
1914 
1915 #endif /* CONFIG_HOTPLUG_CPU */
1916 
1917 static void __init init_timer_cpu(int cpu)
1918 {
1919         struct timer_base *base;
1920         int i;
1921 
1922         for (i = 0; i < NR_BASES; i++) {
1923                 base = per_cpu_ptr(&timer_bases[i], cpu);
1924                 base->cpu = cpu;
1925                 raw_spin_lock_init(&base->lock);
1926                 base->clk = jiffies;
1927         }
1928 }
1929 
1930 static void __init init_timer_cpus(void)
1931 {
1932         int cpu;
1933 
1934         for_each_possible_cpu(cpu)
1935                 init_timer_cpu(cpu);
1936 }
1937 
1938 void __init init_timers(void)
1939 {
1940         init_timer_cpus();
1941         open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
1942 }
1943 
1944 /**
1945  * msleep - sleep safely even with waitqueue interruptions
1946  * @msecs: Time in milliseconds to sleep for
1947  */
1948 void msleep(unsigned int msecs)
1949 {
1950         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1951 
1952         while (timeout)
1953                 timeout = schedule_timeout_uninterruptible(timeout);
1954 }
1955 
1956 EXPORT_SYMBOL(msleep);
1957 
1958 /**
1959  * msleep_interruptible - sleep waiting for signals
1960  * @msecs: Time in milliseconds to sleep for
1961  */
1962 unsigned long msleep_interruptible(unsigned int msecs)
1963 {
1964         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1965 
1966         while (timeout && !signal_pending(current))
1967                 timeout = schedule_timeout_interruptible(timeout);
1968         return jiffies_to_msecs(timeout);
1969 }
1970 
1971 EXPORT_SYMBOL(msleep_interruptible);
1972 
1973 /**
1974  * usleep_range - Sleep for an approximate time
1975  * @min: Minimum time in usecs to sleep
1976  * @max: Maximum time in usecs to sleep
1977  *
1978  * In non-atomic context where the exact wakeup time is flexible, use
1979  * usleep_range() instead of udelay().  The sleep improves responsiveness
1980  * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
1981  * power usage by allowing hrtimers to take advantage of an already-
1982  * scheduled interrupt instead of scheduling a new one just for this sleep.
1983  */
1984 void __sched usleep_range(unsigned long min, unsigned long max)
1985 {
1986         ktime_t exp = ktime_add_us(ktime_get(), min);
1987         u64 delta = (u64)(max - min) * NSEC_PER_USEC;
1988 
1989         for (;;) {
1990                 __set_current_state(TASK_UNINTERRUPTIBLE);
1991                 /* Do not return before the requested sleep time has elapsed */
1992                 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
1993                         break;
1994         }
1995 }
1996 EXPORT_SYMBOL(usleep_range);
1997 

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