Line data Source code
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 : #include <linux/random.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. We start from the last possible delta of the previous level
161 : * so that we can later add an extra LVL_GRAN(n) to n (see calc_index()).
162 : */
163 : #define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
164 :
165 : /* Size of each clock level */
166 : #define LVL_BITS 6
167 : #define LVL_SIZE (1UL << LVL_BITS)
168 : #define LVL_MASK (LVL_SIZE - 1)
169 : #define LVL_OFFS(n) ((n) * LVL_SIZE)
170 :
171 : /* Level depth */
172 : #if HZ > 100
173 : # define LVL_DEPTH 9
174 : # else
175 : # define LVL_DEPTH 8
176 : #endif
177 :
178 : /* The cutoff (max. capacity of the wheel) */
179 : #define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
180 : #define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
181 :
182 : /*
183 : * The resulting wheel size. If NOHZ is configured we allocate two
184 : * wheels so we have a separate storage for the deferrable timers.
185 : */
186 : #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
187 :
188 : #ifdef CONFIG_NO_HZ_COMMON
189 : # define NR_BASES 2
190 : # define BASE_STD 0
191 : # define BASE_DEF 1
192 : #else
193 : # define NR_BASES 1
194 : # define BASE_STD 0
195 : # define BASE_DEF 0
196 : #endif
197 :
198 : struct timer_base {
199 : raw_spinlock_t lock;
200 : struct timer_list *running_timer;
201 : #ifdef CONFIG_PREEMPT_RT
202 : spinlock_t expiry_lock;
203 : atomic_t timer_waiters;
204 : #endif
205 : unsigned long clk;
206 : unsigned long next_expiry;
207 : unsigned int cpu;
208 : bool next_expiry_recalc;
209 : bool is_idle;
210 : bool timers_pending;
211 : DECLARE_BITMAP(pending_map, WHEEL_SIZE);
212 : struct hlist_head vectors[WHEEL_SIZE];
213 : } ____cacheline_aligned;
214 :
215 : static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
216 :
217 : #ifdef CONFIG_NO_HZ_COMMON
218 :
219 : static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
220 : static DEFINE_MUTEX(timer_keys_mutex);
221 :
222 : static void timer_update_keys(struct work_struct *work);
223 : static DECLARE_WORK(timer_update_work, timer_update_keys);
224 :
225 : #ifdef CONFIG_SMP
226 : unsigned int sysctl_timer_migration = 1;
227 :
228 : DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
229 :
230 : static void timers_update_migration(void)
231 : {
232 : if (sysctl_timer_migration && tick_nohz_active)
233 : static_branch_enable(&timers_migration_enabled);
234 : else
235 : static_branch_disable(&timers_migration_enabled);
236 : }
237 : #else
238 : static inline void timers_update_migration(void) { }
239 : #endif /* !CONFIG_SMP */
240 :
241 : static void timer_update_keys(struct work_struct *work)
242 : {
243 : mutex_lock(&timer_keys_mutex);
244 : timers_update_migration();
245 : static_branch_enable(&timers_nohz_active);
246 : mutex_unlock(&timer_keys_mutex);
247 : }
248 :
249 : void timers_update_nohz(void)
250 : {
251 : schedule_work(&timer_update_work);
252 : }
253 :
254 : int timer_migration_handler(struct ctl_table *table, int write,
255 : void *buffer, size_t *lenp, loff_t *ppos)
256 : {
257 : int ret;
258 :
259 : mutex_lock(&timer_keys_mutex);
260 : ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
261 : if (!ret && write)
262 : timers_update_migration();
263 : mutex_unlock(&timer_keys_mutex);
264 : return ret;
265 : }
266 :
267 : static inline bool is_timers_nohz_active(void)
268 : {
269 : return static_branch_unlikely(&timers_nohz_active);
270 : }
271 : #else
272 : static inline bool is_timers_nohz_active(void) { return false; }
273 : #endif /* NO_HZ_COMMON */
274 :
275 : static unsigned long round_jiffies_common(unsigned long j, int cpu,
276 : bool force_up)
277 : {
278 : int rem;
279 0 : unsigned long original = j;
280 :
281 : /*
282 : * We don't want all cpus firing their timers at once hitting the
283 : * same lock or cachelines, so we skew each extra cpu with an extra
284 : * 3 jiffies. This 3 jiffies came originally from the mm/ code which
285 : * already did this.
286 : * The skew is done by adding 3*cpunr, then round, then subtract this
287 : * extra offset again.
288 : */
289 0 : j += cpu * 3;
290 :
291 0 : rem = j % HZ;
292 :
293 : /*
294 : * If the target jiffie is just after a whole second (which can happen
295 : * due to delays of the timer irq, long irq off times etc etc) then
296 : * we should round down to the whole second, not up. Use 1/4th second
297 : * as cutoff for this rounding as an extreme upper bound for this.
298 : * But never round down if @force_up is set.
299 : */
300 0 : if (rem < HZ/4 && !force_up) /* round down */
301 0 : j = j - rem;
302 : else /* round up */
303 0 : j = j - rem + HZ;
304 :
305 : /* now that we have rounded, subtract the extra skew again */
306 0 : j -= cpu * 3;
307 :
308 : /*
309 : * Make sure j is still in the future. Otherwise return the
310 : * unmodified value.
311 : */
312 0 : return time_is_after_jiffies(j) ? j : original;
313 : }
314 :
315 : /**
316 : * __round_jiffies - function to round jiffies to a full second
317 : * @j: the time in (absolute) jiffies that should be rounded
318 : * @cpu: the processor number on which the timeout will happen
319 : *
320 : * __round_jiffies() rounds an absolute time in the future (in jiffies)
321 : * up or down to (approximately) full seconds. This is useful for timers
322 : * for which the exact time they fire does not matter too much, as long as
323 : * they fire approximately every X seconds.
324 : *
325 : * By rounding these timers to whole seconds, all such timers will fire
326 : * at the same time, rather than at various times spread out. The goal
327 : * of this is to have the CPU wake up less, which saves power.
328 : *
329 : * The exact rounding is skewed for each processor to avoid all
330 : * processors firing at the exact same time, which could lead
331 : * to lock contention or spurious cache line bouncing.
332 : *
333 : * The return value is the rounded version of the @j parameter.
334 : */
335 0 : unsigned long __round_jiffies(unsigned long j, int cpu)
336 : {
337 0 : return round_jiffies_common(j, cpu, false);
338 : }
339 : EXPORT_SYMBOL_GPL(__round_jiffies);
340 :
341 : /**
342 : * __round_jiffies_relative - function to round jiffies to a full second
343 : * @j: the time in (relative) jiffies that should be rounded
344 : * @cpu: the processor number on which the timeout will happen
345 : *
346 : * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
347 : * up or down to (approximately) full seconds. This is useful for timers
348 : * for which the exact time they fire does not matter too much, as long as
349 : * they fire approximately every X seconds.
350 : *
351 : * By rounding these timers to whole seconds, all such timers will fire
352 : * at the same time, rather than at various times spread out. The goal
353 : * of this is to have the CPU wake up less, which saves power.
354 : *
355 : * The exact rounding is skewed for each processor to avoid all
356 : * processors firing at the exact same time, which could lead
357 : * to lock contention or spurious cache line bouncing.
358 : *
359 : * The return value is the rounded version of the @j parameter.
360 : */
361 0 : unsigned long __round_jiffies_relative(unsigned long j, int cpu)
362 : {
363 0 : unsigned long j0 = jiffies;
364 :
365 : /* Use j0 because jiffies might change while we run */
366 0 : return round_jiffies_common(j + j0, cpu, false) - j0;
367 : }
368 : EXPORT_SYMBOL_GPL(__round_jiffies_relative);
369 :
370 : /**
371 : * round_jiffies - function to round jiffies to a full second
372 : * @j: the time in (absolute) jiffies that should be rounded
373 : *
374 : * round_jiffies() rounds an absolute time in the future (in jiffies)
375 : * up or down to (approximately) full seconds. This is useful for timers
376 : * for which the exact time they fire does not matter too much, as long as
377 : * they fire approximately every X seconds.
378 : *
379 : * By rounding these timers to whole seconds, all such timers will fire
380 : * at the same time, rather than at various times spread out. The goal
381 : * of this is to have the CPU wake up less, which saves power.
382 : *
383 : * The return value is the rounded version of the @j parameter.
384 : */
385 0 : unsigned long round_jiffies(unsigned long j)
386 : {
387 0 : return round_jiffies_common(j, raw_smp_processor_id(), false);
388 : }
389 : EXPORT_SYMBOL_GPL(round_jiffies);
390 :
391 : /**
392 : * round_jiffies_relative - function to round jiffies to a full second
393 : * @j: the time in (relative) jiffies that should be rounded
394 : *
395 : * round_jiffies_relative() rounds a time delta in the future (in jiffies)
396 : * up or down to (approximately) full seconds. This is useful for timers
397 : * for which the exact time they fire does not matter too much, as long as
398 : * they fire approximately every X seconds.
399 : *
400 : * By rounding these timers to whole seconds, all such timers will fire
401 : * at the same time, rather than at various times spread out. The goal
402 : * of this is to have the CPU wake up less, which saves power.
403 : *
404 : * The return value is the rounded version of the @j parameter.
405 : */
406 0 : unsigned long round_jiffies_relative(unsigned long j)
407 : {
408 0 : return __round_jiffies_relative(j, raw_smp_processor_id());
409 : }
410 : EXPORT_SYMBOL_GPL(round_jiffies_relative);
411 :
412 : /**
413 : * __round_jiffies_up - function to round jiffies up to a full second
414 : * @j: the time in (absolute) jiffies that should be rounded
415 : * @cpu: the processor number on which the timeout will happen
416 : *
417 : * This is the same as __round_jiffies() except that it will never
418 : * round down. This is useful for timeouts for which the exact time
419 : * of firing does not matter too much, as long as they don't fire too
420 : * early.
421 : */
422 0 : unsigned long __round_jiffies_up(unsigned long j, int cpu)
423 : {
424 0 : return round_jiffies_common(j, cpu, true);
425 : }
426 : EXPORT_SYMBOL_GPL(__round_jiffies_up);
427 :
428 : /**
429 : * __round_jiffies_up_relative - function to round jiffies up to a full second
430 : * @j: the time in (relative) jiffies that should be rounded
431 : * @cpu: the processor number on which the timeout will happen
432 : *
433 : * This is the same as __round_jiffies_relative() except that it will never
434 : * round down. This is useful for timeouts for which the exact time
435 : * of firing does not matter too much, as long as they don't fire too
436 : * early.
437 : */
438 0 : unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
439 : {
440 0 : unsigned long j0 = jiffies;
441 :
442 : /* Use j0 because jiffies might change while we run */
443 0 : return round_jiffies_common(j + j0, cpu, true) - j0;
444 : }
445 : EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
446 :
447 : /**
448 : * round_jiffies_up - function to round jiffies up to a full second
449 : * @j: the time in (absolute) jiffies that should be rounded
450 : *
451 : * This is the same as round_jiffies() except that it will never
452 : * round down. This is useful for timeouts for which the exact time
453 : * of firing does not matter too much, as long as they don't fire too
454 : * early.
455 : */
456 0 : unsigned long round_jiffies_up(unsigned long j)
457 : {
458 0 : return round_jiffies_common(j, raw_smp_processor_id(), true);
459 : }
460 : EXPORT_SYMBOL_GPL(round_jiffies_up);
461 :
462 : /**
463 : * round_jiffies_up_relative - function to round jiffies up to a full second
464 : * @j: the time in (relative) jiffies that should be rounded
465 : *
466 : * This is the same as round_jiffies_relative() except that it will never
467 : * round down. This is useful for timeouts for which the exact time
468 : * of firing does not matter too much, as long as they don't fire too
469 : * early.
470 : */
471 0 : unsigned long round_jiffies_up_relative(unsigned long j)
472 : {
473 0 : return __round_jiffies_up_relative(j, raw_smp_processor_id());
474 : }
475 : EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
476 :
477 :
478 : static inline unsigned int timer_get_idx(struct timer_list *timer)
479 : {
480 193 : return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
481 : }
482 :
483 : static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
484 : {
485 196 : timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
486 98 : idx << TIMER_ARRAYSHIFT;
487 : }
488 :
489 : /*
490 : * Helper function to calculate the array index for a given expiry
491 : * time.
492 : */
493 : static inline unsigned calc_index(unsigned long expires, unsigned lvl,
494 : unsigned long *bucket_expiry)
495 : {
496 :
497 : /*
498 : * The timer wheel has to guarantee that a timer does not fire
499 : * early. Early expiry can happen due to:
500 : * - Timer is armed at the edge of a tick
501 : * - Truncation of the expiry time in the outer wheel levels
502 : *
503 : * Round up with level granularity to prevent this.
504 : */
505 98 : expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
506 98 : *bucket_expiry = expires << LVL_SHIFT(lvl);
507 98 : return LVL_OFFS(lvl) + (expires & LVL_MASK);
508 : }
509 :
510 98 : static int calc_wheel_index(unsigned long expires, unsigned long clk,
511 : unsigned long *bucket_expiry)
512 : {
513 98 : unsigned long delta = expires - clk;
514 : unsigned int idx;
515 :
516 98 : if (delta < LVL_START(1)) {
517 4 : idx = calc_index(expires, 0, bucket_expiry);
518 94 : } else if (delta < LVL_START(2)) {
519 0 : idx = calc_index(expires, 1, bucket_expiry);
520 94 : } else if (delta < LVL_START(3)) {
521 0 : idx = calc_index(expires, 2, bucket_expiry);
522 94 : } else if (delta < LVL_START(4)) {
523 93 : idx = calc_index(expires, 3, bucket_expiry);
524 1 : } else if (delta < LVL_START(5)) {
525 0 : idx = calc_index(expires, 4, bucket_expiry);
526 1 : } else if (delta < LVL_START(6)) {
527 0 : idx = calc_index(expires, 5, bucket_expiry);
528 1 : } else if (delta < LVL_START(7)) {
529 1 : idx = calc_index(expires, 6, bucket_expiry);
530 : } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
531 : idx = calc_index(expires, 7, bucket_expiry);
532 0 : } else if ((long) delta < 0) {
533 0 : idx = clk & LVL_MASK;
534 0 : *bucket_expiry = clk;
535 : } else {
536 : /*
537 : * Force expire obscene large timeouts to expire at the
538 : * capacity limit of the wheel.
539 : */
540 0 : if (delta >= WHEEL_TIMEOUT_CUTOFF)
541 0 : expires = clk + WHEEL_TIMEOUT_MAX;
542 :
543 0 : idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
544 : }
545 98 : return idx;
546 : }
547 :
548 : static void
549 : trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
550 : {
551 : if (!is_timers_nohz_active())
552 : return;
553 :
554 : /*
555 : * TODO: This wants some optimizing similar to the code below, but we
556 : * will do that when we switch from push to pull for deferrable timers.
557 : */
558 : if (timer->flags & TIMER_DEFERRABLE) {
559 : if (tick_nohz_full_cpu(base->cpu))
560 : wake_up_nohz_cpu(base->cpu);
561 : return;
562 : }
563 :
564 : /*
565 : * We might have to IPI the remote CPU if the base is idle and the
566 : * timer is not deferrable. If the other CPU is on the way to idle
567 : * then it can't set base->is_idle as we hold the base lock:
568 : */
569 : if (base->is_idle)
570 : wake_up_nohz_cpu(base->cpu);
571 : }
572 :
573 : /*
574 : * Enqueue the timer into the hash bucket, mark it pending in
575 : * the bitmap, store the index in the timer flags then wake up
576 : * the target CPU if needed.
577 : */
578 : static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
579 : unsigned int idx, unsigned long bucket_expiry)
580 : {
581 :
582 196 : hlist_add_head(&timer->entry, base->vectors + idx);
583 196 : __set_bit(idx, base->pending_map);
584 196 : timer_set_idx(timer, idx);
585 :
586 98 : trace_timer_start(timer, timer->expires, timer->flags);
587 :
588 : /*
589 : * Check whether this is the new first expiring timer. The
590 : * effective expiry time of the timer is required here
591 : * (bucket_expiry) instead of timer->expires.
592 : */
593 98 : if (time_before(bucket_expiry, base->next_expiry)) {
594 : /*
595 : * Set the next expiry time and kick the CPU so it
596 : * can reevaluate the wheel:
597 : */
598 2 : base->next_expiry = bucket_expiry;
599 2 : base->timers_pending = true;
600 2 : base->next_expiry_recalc = false;
601 2 : trigger_dyntick_cpu(base, timer);
602 : }
603 : }
604 :
605 98 : static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
606 : {
607 : unsigned long bucket_expiry;
608 : unsigned int idx;
609 :
610 98 : idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry);
611 196 : enqueue_timer(base, timer, idx, bucket_expiry);
612 98 : }
613 :
614 : #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
615 :
616 : static const struct debug_obj_descr timer_debug_descr;
617 :
618 : static void *timer_debug_hint(void *addr)
619 : {
620 : return ((struct timer_list *) addr)->function;
621 : }
622 :
623 : static bool timer_is_static_object(void *addr)
624 : {
625 : struct timer_list *timer = addr;
626 :
627 : return (timer->entry.pprev == NULL &&
628 : timer->entry.next == TIMER_ENTRY_STATIC);
629 : }
630 :
631 : /*
632 : * fixup_init is called when:
633 : * - an active object is initialized
634 : */
635 : static bool timer_fixup_init(void *addr, enum debug_obj_state state)
636 : {
637 : struct timer_list *timer = addr;
638 :
639 : switch (state) {
640 : case ODEBUG_STATE_ACTIVE:
641 : del_timer_sync(timer);
642 : debug_object_init(timer, &timer_debug_descr);
643 : return true;
644 : default:
645 : return false;
646 : }
647 : }
648 :
649 : /* Stub timer callback for improperly used timers. */
650 : static void stub_timer(struct timer_list *unused)
651 : {
652 : WARN_ON(1);
653 : }
654 :
655 : /*
656 : * fixup_activate is called when:
657 : * - an active object is activated
658 : * - an unknown non-static object is activated
659 : */
660 : static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
661 : {
662 : struct timer_list *timer = addr;
663 :
664 : switch (state) {
665 : case ODEBUG_STATE_NOTAVAILABLE:
666 : timer_setup(timer, stub_timer, 0);
667 : return true;
668 :
669 : case ODEBUG_STATE_ACTIVE:
670 : WARN_ON(1);
671 : fallthrough;
672 : default:
673 : return false;
674 : }
675 : }
676 :
677 : /*
678 : * fixup_free is called when:
679 : * - an active object is freed
680 : */
681 : static bool timer_fixup_free(void *addr, enum debug_obj_state state)
682 : {
683 : struct timer_list *timer = addr;
684 :
685 : switch (state) {
686 : case ODEBUG_STATE_ACTIVE:
687 : del_timer_sync(timer);
688 : debug_object_free(timer, &timer_debug_descr);
689 : return true;
690 : default:
691 : return false;
692 : }
693 : }
694 :
695 : /*
696 : * fixup_assert_init is called when:
697 : * - an untracked/uninit-ed object is found
698 : */
699 : static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
700 : {
701 : struct timer_list *timer = addr;
702 :
703 : switch (state) {
704 : case ODEBUG_STATE_NOTAVAILABLE:
705 : timer_setup(timer, stub_timer, 0);
706 : return true;
707 : default:
708 : return false;
709 : }
710 : }
711 :
712 : static const struct debug_obj_descr timer_debug_descr = {
713 : .name = "timer_list",
714 : .debug_hint = timer_debug_hint,
715 : .is_static_object = timer_is_static_object,
716 : .fixup_init = timer_fixup_init,
717 : .fixup_activate = timer_fixup_activate,
718 : .fixup_free = timer_fixup_free,
719 : .fixup_assert_init = timer_fixup_assert_init,
720 : };
721 :
722 : static inline void debug_timer_init(struct timer_list *timer)
723 : {
724 : debug_object_init(timer, &timer_debug_descr);
725 : }
726 :
727 : static inline void debug_timer_activate(struct timer_list *timer)
728 : {
729 : debug_object_activate(timer, &timer_debug_descr);
730 : }
731 :
732 : static inline void debug_timer_deactivate(struct timer_list *timer)
733 : {
734 : debug_object_deactivate(timer, &timer_debug_descr);
735 : }
736 :
737 : static inline void debug_timer_assert_init(struct timer_list *timer)
738 : {
739 : debug_object_assert_init(timer, &timer_debug_descr);
740 : }
741 :
742 : static void do_init_timer(struct timer_list *timer,
743 : void (*func)(struct timer_list *),
744 : unsigned int flags,
745 : const char *name, struct lock_class_key *key);
746 :
747 : void init_timer_on_stack_key(struct timer_list *timer,
748 : void (*func)(struct timer_list *),
749 : unsigned int flags,
750 : const char *name, struct lock_class_key *key)
751 : {
752 : debug_object_init_on_stack(timer, &timer_debug_descr);
753 : do_init_timer(timer, func, flags, name, key);
754 : }
755 : EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
756 :
757 : void destroy_timer_on_stack(struct timer_list *timer)
758 : {
759 : debug_object_free(timer, &timer_debug_descr);
760 : }
761 : EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
762 :
763 : #else
764 : static inline void debug_timer_init(struct timer_list *timer) { }
765 : static inline void debug_timer_activate(struct timer_list *timer) { }
766 : static inline void debug_timer_deactivate(struct timer_list *timer) { }
767 : static inline void debug_timer_assert_init(struct timer_list *timer) { }
768 : #endif
769 :
770 : static inline void debug_init(struct timer_list *timer)
771 : {
772 105 : debug_timer_init(timer);
773 105 : trace_timer_init(timer);
774 : }
775 :
776 : static inline void debug_deactivate(struct timer_list *timer)
777 : {
778 95 : debug_timer_deactivate(timer);
779 95 : trace_timer_cancel(timer);
780 : }
781 :
782 : static inline void debug_assert_init(struct timer_list *timer)
783 : {
784 95 : debug_timer_assert_init(timer);
785 : }
786 :
787 105 : static void do_init_timer(struct timer_list *timer,
788 : void (*func)(struct timer_list *),
789 : unsigned int flags,
790 : const char *name, struct lock_class_key *key)
791 : {
792 105 : timer->entry.pprev = NULL;
793 105 : timer->function = func;
794 105 : if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
795 0 : flags &= TIMER_INIT_FLAGS;
796 105 : timer->flags = flags | raw_smp_processor_id();
797 : lockdep_init_map(&timer->lockdep_map, name, key, 0);
798 105 : }
799 :
800 : /**
801 : * init_timer_key - initialize a timer
802 : * @timer: the timer to be initialized
803 : * @func: timer callback function
804 : * @flags: timer flags
805 : * @name: name of the timer
806 : * @key: lockdep class key of the fake lock used for tracking timer
807 : * sync lock dependencies
808 : *
809 : * init_timer_key() must be done to a timer prior calling *any* of the
810 : * other timer functions.
811 : */
812 10 : void init_timer_key(struct timer_list *timer,
813 : void (*func)(struct timer_list *), unsigned int flags,
814 : const char *name, struct lock_class_key *key)
815 : {
816 105 : debug_init(timer);
817 105 : do_init_timer(timer, func, flags, name, key);
818 10 : }
819 : EXPORT_SYMBOL(init_timer_key);
820 :
821 : static inline void detach_timer(struct timer_list *timer, bool clear_pending)
822 : {
823 95 : struct hlist_node *entry = &timer->entry;
824 :
825 190 : debug_deactivate(timer);
826 :
827 95 : __hlist_del(entry);
828 95 : if (clear_pending)
829 95 : entry->pprev = NULL;
830 95 : entry->next = LIST_POISON2;
831 : }
832 :
833 193 : static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
834 : bool clear_pending)
835 : {
836 386 : unsigned idx = timer_get_idx(timer);
837 :
838 193 : if (!timer_pending(timer))
839 : return 0;
840 :
841 190 : if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
842 190 : __clear_bit(idx, base->pending_map);
843 95 : base->next_expiry_recalc = true;
844 : }
845 :
846 190 : detach_timer(timer, clear_pending);
847 95 : return 1;
848 : }
849 :
850 : static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
851 : {
852 193 : struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
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 = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
860 : return base;
861 : }
862 :
863 : static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
864 : {
865 98 : struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
866 :
867 : /*
868 : * If the timer is deferrable and NO_HZ_COMMON is set then we need
869 : * to use the deferrable base.
870 : */
871 : if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
872 : base = this_cpu_ptr(&timer_bases[BASE_DEF]);
873 : return base;
874 : }
875 :
876 : static inline struct timer_base *get_timer_base(u32 tflags)
877 : {
878 193 : return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
879 : }
880 :
881 : static inline struct timer_base *
882 : get_target_base(struct timer_base *base, unsigned tflags)
883 : {
884 : #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
885 : if (static_branch_likely(&timers_migration_enabled) &&
886 : !(tflags & TIMER_PINNED))
887 : return get_timer_cpu_base(tflags, get_nohz_timer_target());
888 : #endif
889 98 : return get_timer_this_cpu_base(tflags);
890 : }
891 :
892 98 : static inline void forward_timer_base(struct timer_base *base)
893 : {
894 98 : unsigned long jnow = READ_ONCE(jiffies);
895 :
896 : /*
897 : * No need to forward if we are close enough below jiffies.
898 : * Also while executing timers, base->clk is 1 offset ahead
899 : * of jiffies to avoid endless requeuing to current jiffies.
900 : */
901 98 : if ((long)(jnow - base->clk) < 1)
902 : return;
903 :
904 : /*
905 : * If the next expiry value is > jiffies, then we fast forward to
906 : * jiffies otherwise we forward to the next expiry value.
907 : */
908 2 : if (time_after(base->next_expiry, jnow)) {
909 2 : base->clk = jnow;
910 : } else {
911 0 : if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
912 : return;
913 0 : base->clk = base->next_expiry;
914 : }
915 : }
916 :
917 :
918 : /*
919 : * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
920 : * that all timers which are tied to this base are locked, and the base itself
921 : * is locked too.
922 : *
923 : * So __run_timers/migrate_timers can safely modify all timers which could
924 : * be found in the base->vectors array.
925 : *
926 : * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
927 : * to wait until the migration is done.
928 : */
929 193 : static struct timer_base *lock_timer_base(struct timer_list *timer,
930 : unsigned long *flags)
931 : __acquires(timer->base->lock)
932 : {
933 : for (;;) {
934 : struct timer_base *base;
935 : u32 tf;
936 :
937 : /*
938 : * We need to use READ_ONCE() here, otherwise the compiler
939 : * might re-read @tf between the check for TIMER_MIGRATING
940 : * and spin_lock().
941 : */
942 193 : tf = READ_ONCE(timer->flags);
943 :
944 193 : if (!(tf & TIMER_MIGRATING)) {
945 386 : base = get_timer_base(tf);
946 193 : raw_spin_lock_irqsave(&base->lock, *flags);
947 193 : if (timer->flags == tf)
948 193 : return base;
949 0 : raw_spin_unlock_irqrestore(&base->lock, *flags);
950 : }
951 : cpu_relax();
952 : }
953 : }
954 :
955 : #define MOD_TIMER_PENDING_ONLY 0x01
956 : #define MOD_TIMER_REDUCE 0x02
957 : #define MOD_TIMER_NOTPENDING 0x04
958 :
959 : static inline int
960 98 : __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
961 : {
962 98 : unsigned long clk = 0, flags, bucket_expiry;
963 : struct timer_base *base, *new_base;
964 98 : unsigned int idx = UINT_MAX;
965 98 : int ret = 0;
966 :
967 98 : BUG_ON(!timer->function);
968 :
969 : /*
970 : * This is a common optimization triggered by the networking code - if
971 : * the timer is re-modified to have the same timeout or ends up in the
972 : * same array bucket then just return:
973 : */
974 100 : if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
975 : /*
976 : * The downside of this optimization is that it can result in
977 : * larger granularity than you would get from adding a new
978 : * timer with this expiry.
979 : */
980 0 : long diff = timer->expires - expires;
981 :
982 0 : if (!diff)
983 : return 1;
984 0 : if (options & MOD_TIMER_REDUCE && diff <= 0)
985 : return 1;
986 :
987 : /*
988 : * We lock timer base and calculate the bucket index right
989 : * here. If the timer ends up in the same bucket, then we
990 : * just update the expiry time and avoid the whole
991 : * dequeue/enqueue dance.
992 : */
993 0 : base = lock_timer_base(timer, &flags);
994 0 : forward_timer_base(base);
995 :
996 0 : if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
997 0 : time_before_eq(timer->expires, expires)) {
998 : ret = 1;
999 : goto out_unlock;
1000 : }
1001 :
1002 0 : clk = base->clk;
1003 0 : idx = calc_wheel_index(expires, clk, &bucket_expiry);
1004 :
1005 : /*
1006 : * Retrieve and compare the array index of the pending
1007 : * timer. If it matches set the expiry to the new value so a
1008 : * subsequent call will exit in the expires check above.
1009 : */
1010 0 : if (idx == timer_get_idx(timer)) {
1011 0 : if (!(options & MOD_TIMER_REDUCE))
1012 0 : timer->expires = expires;
1013 0 : else if (time_after(timer->expires, expires))
1014 0 : timer->expires = expires;
1015 : ret = 1;
1016 : goto out_unlock;
1017 : }
1018 : } else {
1019 98 : base = lock_timer_base(timer, &flags);
1020 98 : forward_timer_base(base);
1021 : }
1022 :
1023 98 : ret = detach_if_pending(timer, base, false);
1024 98 : if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1025 : goto out_unlock;
1026 :
1027 196 : new_base = get_target_base(base, timer->flags);
1028 :
1029 98 : if (base != new_base) {
1030 : /*
1031 : * We are trying to schedule the timer on the new base.
1032 : * However we can't change timer's base while it is running,
1033 : * otherwise del_timer_sync() can't detect that the timer's
1034 : * handler yet has not finished. This also guarantees that the
1035 : * timer is serialized wrt itself.
1036 : */
1037 0 : if (likely(base->running_timer != timer)) {
1038 : /* See the comment in lock_timer_base() */
1039 0 : timer->flags |= TIMER_MIGRATING;
1040 :
1041 0 : raw_spin_unlock(&base->lock);
1042 0 : base = new_base;
1043 0 : raw_spin_lock(&base->lock);
1044 0 : WRITE_ONCE(timer->flags,
1045 : (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1046 0 : forward_timer_base(base);
1047 : }
1048 : }
1049 :
1050 98 : debug_timer_activate(timer);
1051 :
1052 98 : timer->expires = expires;
1053 : /*
1054 : * If 'idx' was calculated above and the base time did not advance
1055 : * between calculating 'idx' and possibly switching the base, only
1056 : * enqueue_timer() is required. Otherwise we need to (re)calculate
1057 : * the wheel index via internal_add_timer().
1058 : */
1059 98 : if (idx != UINT_MAX && clk == base->clk)
1060 0 : enqueue_timer(base, timer, idx, bucket_expiry);
1061 : else
1062 98 : internal_add_timer(base, timer);
1063 :
1064 : out_unlock:
1065 196 : raw_spin_unlock_irqrestore(&base->lock, flags);
1066 :
1067 98 : return ret;
1068 : }
1069 :
1070 : /**
1071 : * mod_timer_pending - modify a pending timer's timeout
1072 : * @timer: the pending timer to be modified
1073 : * @expires: new timeout in jiffies
1074 : *
1075 : * mod_timer_pending() is the same for pending timers as mod_timer(),
1076 : * but will not re-activate and modify already deleted timers.
1077 : *
1078 : * It is useful for unserialized use of timers.
1079 : */
1080 0 : int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1081 : {
1082 0 : return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1083 : }
1084 : EXPORT_SYMBOL(mod_timer_pending);
1085 :
1086 : /**
1087 : * mod_timer - modify a timer's timeout
1088 : * @timer: the timer to be modified
1089 : * @expires: new timeout in jiffies
1090 : *
1091 : * mod_timer() is a more efficient way to update the expire field of an
1092 : * active timer (if the timer is inactive it will be activated)
1093 : *
1094 : * mod_timer(timer, expires) is equivalent to:
1095 : *
1096 : * del_timer(timer); timer->expires = expires; add_timer(timer);
1097 : *
1098 : * Note that if there are multiple unserialized concurrent users of the
1099 : * same timer, then mod_timer() is the only safe way to modify the timeout,
1100 : * since add_timer() cannot modify an already running timer.
1101 : *
1102 : * The function returns whether it has modified a pending timer or not.
1103 : * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
1104 : * active timer returns 1.)
1105 : */
1106 2 : int mod_timer(struct timer_list *timer, unsigned long expires)
1107 : {
1108 2 : return __mod_timer(timer, expires, 0);
1109 : }
1110 : EXPORT_SYMBOL(mod_timer);
1111 :
1112 : /**
1113 : * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1114 : * @timer: The timer to be modified
1115 : * @expires: New timeout in jiffies
1116 : *
1117 : * timer_reduce() is very similar to mod_timer(), except that it will only
1118 : * modify a running timer if that would reduce the expiration time (it will
1119 : * start a timer that isn't running).
1120 : */
1121 0 : int timer_reduce(struct timer_list *timer, unsigned long expires)
1122 : {
1123 0 : return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1124 : }
1125 : EXPORT_SYMBOL(timer_reduce);
1126 :
1127 : /**
1128 : * add_timer - start a timer
1129 : * @timer: the timer to be added
1130 : *
1131 : * The kernel will do a ->function(@timer) callback from the
1132 : * timer interrupt at the ->expires point in the future. The
1133 : * current time is 'jiffies'.
1134 : *
1135 : * The timer's ->expires, ->function fields must be set prior calling this
1136 : * function.
1137 : *
1138 : * Timers with an ->expires field in the past will be executed in the next
1139 : * timer tick.
1140 : */
1141 1 : void add_timer(struct timer_list *timer)
1142 : {
1143 1 : BUG_ON(timer_pending(timer));
1144 1 : __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1145 1 : }
1146 : EXPORT_SYMBOL(add_timer);
1147 :
1148 : /**
1149 : * add_timer_on - start a timer on a particular CPU
1150 : * @timer: the timer to be added
1151 : * @cpu: the CPU to start it on
1152 : *
1153 : * This is not very scalable on SMP. Double adds are not possible.
1154 : */
1155 0 : void add_timer_on(struct timer_list *timer, int cpu)
1156 : {
1157 : struct timer_base *new_base, *base;
1158 : unsigned long flags;
1159 :
1160 0 : BUG_ON(timer_pending(timer) || !timer->function);
1161 :
1162 0 : new_base = get_timer_cpu_base(timer->flags, cpu);
1163 :
1164 : /*
1165 : * If @timer was on a different CPU, it should be migrated with the
1166 : * old base locked to prevent other operations proceeding with the
1167 : * wrong base locked. See lock_timer_base().
1168 : */
1169 0 : base = lock_timer_base(timer, &flags);
1170 0 : if (base != new_base) {
1171 0 : timer->flags |= TIMER_MIGRATING;
1172 :
1173 0 : raw_spin_unlock(&base->lock);
1174 0 : base = new_base;
1175 0 : raw_spin_lock(&base->lock);
1176 0 : WRITE_ONCE(timer->flags,
1177 : (timer->flags & ~TIMER_BASEMASK) | cpu);
1178 : }
1179 0 : forward_timer_base(base);
1180 :
1181 0 : debug_timer_activate(timer);
1182 0 : internal_add_timer(base, timer);
1183 0 : raw_spin_unlock_irqrestore(&base->lock, flags);
1184 0 : }
1185 : EXPORT_SYMBOL_GPL(add_timer_on);
1186 :
1187 : /**
1188 : * del_timer - deactivate a timer.
1189 : * @timer: the timer to be deactivated
1190 : *
1191 : * del_timer() deactivates a timer - this works on both active and inactive
1192 : * timers.
1193 : *
1194 : * The function returns whether it has deactivated a pending timer or not.
1195 : * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
1196 : * active timer returns 1.)
1197 : */
1198 95 : int del_timer(struct timer_list *timer)
1199 : {
1200 : struct timer_base *base;
1201 : unsigned long flags;
1202 95 : int ret = 0;
1203 :
1204 190 : debug_assert_init(timer);
1205 :
1206 95 : if (timer_pending(timer)) {
1207 95 : base = lock_timer_base(timer, &flags);
1208 95 : ret = detach_if_pending(timer, base, true);
1209 190 : raw_spin_unlock_irqrestore(&base->lock, flags);
1210 : }
1211 :
1212 95 : return ret;
1213 : }
1214 : EXPORT_SYMBOL(del_timer);
1215 :
1216 : /**
1217 : * try_to_del_timer_sync - Try to deactivate a timer
1218 : * @timer: timer to delete
1219 : *
1220 : * This function tries to deactivate a timer. Upon successful (ret >= 0)
1221 : * exit the timer is not queued and the handler is not running on any CPU.
1222 : */
1223 0 : int try_to_del_timer_sync(struct timer_list *timer)
1224 : {
1225 : struct timer_base *base;
1226 : unsigned long flags;
1227 0 : int ret = -1;
1228 :
1229 0 : debug_assert_init(timer);
1230 :
1231 0 : base = lock_timer_base(timer, &flags);
1232 :
1233 0 : if (base->running_timer != timer)
1234 0 : ret = detach_if_pending(timer, base, true);
1235 :
1236 0 : raw_spin_unlock_irqrestore(&base->lock, flags);
1237 :
1238 0 : return ret;
1239 : }
1240 : EXPORT_SYMBOL(try_to_del_timer_sync);
1241 :
1242 : #ifdef CONFIG_PREEMPT_RT
1243 : static __init void timer_base_init_expiry_lock(struct timer_base *base)
1244 : {
1245 : spin_lock_init(&base->expiry_lock);
1246 : }
1247 :
1248 : static inline void timer_base_lock_expiry(struct timer_base *base)
1249 : {
1250 : spin_lock(&base->expiry_lock);
1251 : }
1252 :
1253 : static inline void timer_base_unlock_expiry(struct timer_base *base)
1254 : {
1255 : spin_unlock(&base->expiry_lock);
1256 : }
1257 :
1258 : /*
1259 : * The counterpart to del_timer_wait_running().
1260 : *
1261 : * If there is a waiter for base->expiry_lock, then it was waiting for the
1262 : * timer callback to finish. Drop expiry_lock and reacquire it. That allows
1263 : * the waiter to acquire the lock and make progress.
1264 : */
1265 : static void timer_sync_wait_running(struct timer_base *base)
1266 : {
1267 : if (atomic_read(&base->timer_waiters)) {
1268 : raw_spin_unlock_irq(&base->lock);
1269 : spin_unlock(&base->expiry_lock);
1270 : spin_lock(&base->expiry_lock);
1271 : raw_spin_lock_irq(&base->lock);
1272 : }
1273 : }
1274 :
1275 : /*
1276 : * This function is called on PREEMPT_RT kernels when the fast path
1277 : * deletion of a timer failed because the timer callback function was
1278 : * running.
1279 : *
1280 : * This prevents priority inversion, if the softirq thread on a remote CPU
1281 : * got preempted, and it prevents a life lock when the task which tries to
1282 : * delete a timer preempted the softirq thread running the timer callback
1283 : * function.
1284 : */
1285 : static void del_timer_wait_running(struct timer_list *timer)
1286 : {
1287 : u32 tf;
1288 :
1289 : tf = READ_ONCE(timer->flags);
1290 : if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) {
1291 : struct timer_base *base = get_timer_base(tf);
1292 :
1293 : /*
1294 : * Mark the base as contended and grab the expiry lock,
1295 : * which is held by the softirq across the timer
1296 : * callback. Drop the lock immediately so the softirq can
1297 : * expire the next timer. In theory the timer could already
1298 : * be running again, but that's more than unlikely and just
1299 : * causes another wait loop.
1300 : */
1301 : atomic_inc(&base->timer_waiters);
1302 : spin_lock_bh(&base->expiry_lock);
1303 : atomic_dec(&base->timer_waiters);
1304 : spin_unlock_bh(&base->expiry_lock);
1305 : }
1306 : }
1307 : #else
1308 : static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
1309 : static inline void timer_base_lock_expiry(struct timer_base *base) { }
1310 : static inline void timer_base_unlock_expiry(struct timer_base *base) { }
1311 : static inline void timer_sync_wait_running(struct timer_base *base) { }
1312 : static inline void del_timer_wait_running(struct timer_list *timer) { }
1313 : #endif
1314 :
1315 : #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
1316 : /**
1317 : * del_timer_sync - deactivate a timer and wait for the handler to finish.
1318 : * @timer: the timer to be deactivated
1319 : *
1320 : * This function only differs from del_timer() on SMP: besides deactivating
1321 : * the timer it also makes sure the handler has finished executing on other
1322 : * CPUs.
1323 : *
1324 : * Synchronization rules: Callers must prevent restarting of the timer,
1325 : * otherwise this function is meaningless. It must not be called from
1326 : * interrupt contexts unless the timer is an irqsafe one. The caller must
1327 : * not hold locks which would prevent completion of the timer's
1328 : * handler. The timer's handler must not call add_timer_on(). Upon exit the
1329 : * timer is not queued and the handler is not running on any CPU.
1330 : *
1331 : * Note: For !irqsafe timers, you must not hold locks that are held in
1332 : * interrupt context while calling this function. Even if the lock has
1333 : * nothing to do with the timer in question. Here's why::
1334 : *
1335 : * CPU0 CPU1
1336 : * ---- ----
1337 : * <SOFTIRQ>
1338 : * call_timer_fn();
1339 : * base->running_timer = mytimer;
1340 : * spin_lock_irq(somelock);
1341 : * <IRQ>
1342 : * spin_lock(somelock);
1343 : * del_timer_sync(mytimer);
1344 : * while (base->running_timer == mytimer);
1345 : *
1346 : * Now del_timer_sync() will never return and never release somelock.
1347 : * The interrupt on the other CPU is waiting to grab somelock but
1348 : * it has interrupted the softirq that CPU0 is waiting to finish.
1349 : *
1350 : * The function returns whether it has deactivated a pending timer or not.
1351 : */
1352 : int del_timer_sync(struct timer_list *timer)
1353 : {
1354 : int ret;
1355 :
1356 : #ifdef CONFIG_LOCKDEP
1357 : unsigned long flags;
1358 :
1359 : /*
1360 : * If lockdep gives a backtrace here, please reference
1361 : * the synchronization rules above.
1362 : */
1363 : local_irq_save(flags);
1364 : lock_map_acquire(&timer->lockdep_map);
1365 : lock_map_release(&timer->lockdep_map);
1366 : local_irq_restore(flags);
1367 : #endif
1368 : /*
1369 : * don't use it in hardirq context, because it
1370 : * could lead to deadlock.
1371 : */
1372 : WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
1373 :
1374 : /*
1375 : * Must be able to sleep on PREEMPT_RT because of the slowpath in
1376 : * del_timer_wait_running().
1377 : */
1378 : if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
1379 : lockdep_assert_preemption_enabled();
1380 :
1381 : do {
1382 : ret = try_to_del_timer_sync(timer);
1383 :
1384 : if (unlikely(ret < 0)) {
1385 : del_timer_wait_running(timer);
1386 : cpu_relax();
1387 : }
1388 : } while (ret < 0);
1389 :
1390 : return ret;
1391 : }
1392 : EXPORT_SYMBOL(del_timer_sync);
1393 : #endif
1394 :
1395 0 : static void call_timer_fn(struct timer_list *timer,
1396 : void (*fn)(struct timer_list *),
1397 : unsigned long baseclk)
1398 : {
1399 0 : int count = preempt_count();
1400 :
1401 : #ifdef CONFIG_LOCKDEP
1402 : /*
1403 : * It is permissible to free the timer from inside the
1404 : * function that is called from it, this we need to take into
1405 : * account for lockdep too. To avoid bogus "held lock freed"
1406 : * warnings as well as problems when looking into
1407 : * timer->lockdep_map, make a copy and use that here.
1408 : */
1409 : struct lockdep_map lockdep_map;
1410 :
1411 : lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1412 : #endif
1413 : /*
1414 : * Couple the lock chain with the lock chain at
1415 : * del_timer_sync() by acquiring the lock_map around the fn()
1416 : * call here and in del_timer_sync().
1417 : */
1418 : lock_map_acquire(&lockdep_map);
1419 :
1420 0 : trace_timer_expire_entry(timer, baseclk);
1421 0 : fn(timer);
1422 0 : trace_timer_expire_exit(timer);
1423 :
1424 : lock_map_release(&lockdep_map);
1425 :
1426 0 : if (count != preempt_count()) {
1427 0 : WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1428 : fn, count, preempt_count());
1429 : /*
1430 : * Restore the preempt count. That gives us a decent
1431 : * chance to survive and extract information. If the
1432 : * callback kept a lock held, bad luck, but not worse
1433 : * than the BUG() we had.
1434 : */
1435 : preempt_count_set(count);
1436 : }
1437 0 : }
1438 :
1439 0 : static void expire_timers(struct timer_base *base, struct hlist_head *head)
1440 : {
1441 : /*
1442 : * This value is required only for tracing. base->clk was
1443 : * incremented directly before expire_timers was called. But expiry
1444 : * is related to the old base->clk value.
1445 : */
1446 0 : unsigned long baseclk = base->clk - 1;
1447 :
1448 0 : while (!hlist_empty(head)) {
1449 : struct timer_list *timer;
1450 : void (*fn)(struct timer_list *);
1451 :
1452 0 : timer = hlist_entry(head->first, struct timer_list, entry);
1453 :
1454 0 : base->running_timer = timer;
1455 0 : detach_timer(timer, true);
1456 :
1457 0 : fn = timer->function;
1458 :
1459 0 : if (timer->flags & TIMER_IRQSAFE) {
1460 0 : raw_spin_unlock(&base->lock);
1461 0 : call_timer_fn(timer, fn, baseclk);
1462 0 : raw_spin_lock(&base->lock);
1463 0 : base->running_timer = NULL;
1464 : } else {
1465 0 : raw_spin_unlock_irq(&base->lock);
1466 0 : call_timer_fn(timer, fn, baseclk);
1467 0 : raw_spin_lock_irq(&base->lock);
1468 0 : base->running_timer = NULL;
1469 0 : timer_sync_wait_running(base);
1470 : }
1471 : }
1472 0 : }
1473 :
1474 0 : static int collect_expired_timers(struct timer_base *base,
1475 : struct hlist_head *heads)
1476 : {
1477 0 : unsigned long clk = base->clk = base->next_expiry;
1478 : struct hlist_head *vec;
1479 0 : int i, levels = 0;
1480 : unsigned int idx;
1481 :
1482 0 : for (i = 0; i < LVL_DEPTH; i++) {
1483 0 : idx = (clk & LVL_MASK) + i * LVL_SIZE;
1484 :
1485 0 : if (__test_and_clear_bit(idx, base->pending_map)) {
1486 0 : vec = base->vectors + idx;
1487 0 : hlist_move_list(vec, heads++);
1488 0 : levels++;
1489 : }
1490 : /* Is it time to look at the next level? */
1491 0 : if (clk & LVL_CLK_MASK)
1492 : break;
1493 : /* Shift clock for the next level granularity */
1494 0 : clk >>= LVL_CLK_SHIFT;
1495 : }
1496 0 : return levels;
1497 : }
1498 :
1499 : /*
1500 : * Find the next pending bucket of a level. Search from level start (@offset)
1501 : * + @clk upwards and if nothing there, search from start of the level
1502 : * (@offset) up to @offset + clk.
1503 : */
1504 0 : static int next_pending_bucket(struct timer_base *base, unsigned offset,
1505 : unsigned clk)
1506 : {
1507 0 : unsigned pos, start = offset + clk;
1508 0 : unsigned end = offset + LVL_SIZE;
1509 :
1510 0 : pos = find_next_bit(base->pending_map, end, start);
1511 0 : if (pos < end)
1512 0 : return pos - start;
1513 :
1514 0 : pos = find_next_bit(base->pending_map, start, offset);
1515 0 : return pos < start ? pos + LVL_SIZE - start : -1;
1516 : }
1517 :
1518 : /*
1519 : * Search the first expiring timer in the various clock levels. Caller must
1520 : * hold base->lock.
1521 : */
1522 0 : static unsigned long __next_timer_interrupt(struct timer_base *base)
1523 : {
1524 : unsigned long clk, next, adj;
1525 0 : unsigned lvl, offset = 0;
1526 :
1527 0 : next = base->clk + NEXT_TIMER_MAX_DELTA;
1528 0 : clk = base->clk;
1529 0 : for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1530 0 : int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1531 0 : unsigned long lvl_clk = clk & LVL_CLK_MASK;
1532 :
1533 0 : if (pos >= 0) {
1534 0 : unsigned long tmp = clk + (unsigned long) pos;
1535 :
1536 0 : tmp <<= LVL_SHIFT(lvl);
1537 0 : if (time_before(tmp, next))
1538 0 : next = tmp;
1539 :
1540 : /*
1541 : * If the next expiration happens before we reach
1542 : * the next level, no need to check further.
1543 : */
1544 0 : if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
1545 : break;
1546 : }
1547 : /*
1548 : * Clock for the next level. If the current level clock lower
1549 : * bits are zero, we look at the next level as is. If not we
1550 : * need to advance it by one because that's going to be the
1551 : * next expiring bucket in that level. base->clk is the next
1552 : * expiring jiffie. So in case of:
1553 : *
1554 : * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1555 : * 0 0 0 0 0 0
1556 : *
1557 : * we have to look at all levels @index 0. With
1558 : *
1559 : * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1560 : * 0 0 0 0 0 2
1561 : *
1562 : * LVL0 has the next expiring bucket @index 2. The upper
1563 : * levels have the next expiring bucket @index 1.
1564 : *
1565 : * In case that the propagation wraps the next level the same
1566 : * rules apply:
1567 : *
1568 : * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1569 : * 0 0 0 0 F 2
1570 : *
1571 : * So after looking at LVL0 we get:
1572 : *
1573 : * LVL5 LVL4 LVL3 LVL2 LVL1
1574 : * 0 0 0 1 0
1575 : *
1576 : * So no propagation from LVL1 to LVL2 because that happened
1577 : * with the add already, but then we need to propagate further
1578 : * from LVL2 to LVL3.
1579 : *
1580 : * So the simple check whether the lower bits of the current
1581 : * level are 0 or not is sufficient for all cases.
1582 : */
1583 0 : adj = lvl_clk ? 1 : 0;
1584 0 : clk >>= LVL_CLK_SHIFT;
1585 0 : clk += adj;
1586 : }
1587 :
1588 0 : base->next_expiry_recalc = false;
1589 0 : base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
1590 :
1591 0 : return next;
1592 : }
1593 :
1594 : #ifdef CONFIG_NO_HZ_COMMON
1595 : /*
1596 : * Check, if the next hrtimer event is before the next timer wheel
1597 : * event:
1598 : */
1599 : static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1600 : {
1601 : u64 nextevt = hrtimer_get_next_event();
1602 :
1603 : /*
1604 : * If high resolution timers are enabled
1605 : * hrtimer_get_next_event() returns KTIME_MAX.
1606 : */
1607 : if (expires <= nextevt)
1608 : return expires;
1609 :
1610 : /*
1611 : * If the next timer is already expired, return the tick base
1612 : * time so the tick is fired immediately.
1613 : */
1614 : if (nextevt <= basem)
1615 : return basem;
1616 :
1617 : /*
1618 : * Round up to the next jiffie. High resolution timers are
1619 : * off, so the hrtimers are expired in the tick and we need to
1620 : * make sure that this tick really expires the timer to avoid
1621 : * a ping pong of the nohz stop code.
1622 : *
1623 : * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1624 : */
1625 : return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1626 : }
1627 :
1628 : /**
1629 : * get_next_timer_interrupt - return the time (clock mono) of the next timer
1630 : * @basej: base time jiffies
1631 : * @basem: base time clock monotonic
1632 : *
1633 : * Returns the tick aligned clock monotonic time of the next pending
1634 : * timer or KTIME_MAX if no timer is pending.
1635 : */
1636 : u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1637 : {
1638 : struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1639 : u64 expires = KTIME_MAX;
1640 : unsigned long nextevt;
1641 :
1642 : /*
1643 : * Pretend that there is no timer pending if the cpu is offline.
1644 : * Possible pending timers will be migrated later to an active cpu.
1645 : */
1646 : if (cpu_is_offline(smp_processor_id()))
1647 : return expires;
1648 :
1649 : raw_spin_lock(&base->lock);
1650 : if (base->next_expiry_recalc)
1651 : base->next_expiry = __next_timer_interrupt(base);
1652 : nextevt = base->next_expiry;
1653 :
1654 : /*
1655 : * We have a fresh next event. Check whether we can forward the
1656 : * base. We can only do that when @basej is past base->clk
1657 : * otherwise we might rewind base->clk.
1658 : */
1659 : if (time_after(basej, base->clk)) {
1660 : if (time_after(nextevt, basej))
1661 : base->clk = basej;
1662 : else if (time_after(nextevt, base->clk))
1663 : base->clk = nextevt;
1664 : }
1665 :
1666 : if (time_before_eq(nextevt, basej)) {
1667 : expires = basem;
1668 : base->is_idle = false;
1669 : } else {
1670 : if (base->timers_pending)
1671 : expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1672 : /*
1673 : * If we expect to sleep more than a tick, mark the base idle.
1674 : * Also the tick is stopped so any added timer must forward
1675 : * the base clk itself to keep granularity small. This idle
1676 : * logic is only maintained for the BASE_STD base, deferrable
1677 : * timers may still see large granularity skew (by design).
1678 : */
1679 : if ((expires - basem) > TICK_NSEC)
1680 : base->is_idle = true;
1681 : }
1682 : raw_spin_unlock(&base->lock);
1683 :
1684 : return cmp_next_hrtimer_event(basem, expires);
1685 : }
1686 :
1687 : /**
1688 : * timer_clear_idle - Clear the idle state of the timer base
1689 : *
1690 : * Called with interrupts disabled
1691 : */
1692 : void timer_clear_idle(void)
1693 : {
1694 : struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1695 :
1696 : /*
1697 : * We do this unlocked. The worst outcome is a remote enqueue sending
1698 : * a pointless IPI, but taking the lock would just make the window for
1699 : * sending the IPI a few instructions smaller for the cost of taking
1700 : * the lock in the exit from idle path.
1701 : */
1702 : base->is_idle = false;
1703 : }
1704 : #endif
1705 :
1706 : /**
1707 : * __run_timers - run all expired timers (if any) on this CPU.
1708 : * @base: the timer vector to be processed.
1709 : */
1710 0 : static inline void __run_timers(struct timer_base *base)
1711 : {
1712 : struct hlist_head heads[LVL_DEPTH];
1713 : int levels;
1714 :
1715 0 : if (time_before(jiffies, base->next_expiry))
1716 0 : return;
1717 :
1718 0 : timer_base_lock_expiry(base);
1719 0 : raw_spin_lock_irq(&base->lock);
1720 :
1721 0 : while (time_after_eq(jiffies, base->clk) &&
1722 0 : time_after_eq(jiffies, base->next_expiry)) {
1723 0 : levels = collect_expired_timers(base, heads);
1724 : /*
1725 : * The two possible reasons for not finding any expired
1726 : * timer at this clk are that all matching timers have been
1727 : * dequeued or no timer has been queued since
1728 : * base::next_expiry was set to base::clk +
1729 : * NEXT_TIMER_MAX_DELTA.
1730 : */
1731 0 : WARN_ON_ONCE(!levels && !base->next_expiry_recalc
1732 : && base->timers_pending);
1733 0 : base->clk++;
1734 0 : base->next_expiry = __next_timer_interrupt(base);
1735 :
1736 0 : while (levels--)
1737 0 : expire_timers(base, heads + levels);
1738 : }
1739 0 : raw_spin_unlock_irq(&base->lock);
1740 0 : timer_base_unlock_expiry(base);
1741 : }
1742 :
1743 : /*
1744 : * This function runs timers and the timer-tq in bottom half context.
1745 : */
1746 0 : static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1747 : {
1748 0 : struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1749 :
1750 0 : __run_timers(base);
1751 : if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1752 : __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1753 0 : }
1754 :
1755 : /*
1756 : * Called by the local, per-CPU timer interrupt on SMP.
1757 : */
1758 13 : static void run_local_timers(void)
1759 : {
1760 13 : struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1761 :
1762 13 : hrtimer_run_queues();
1763 : /* Raise the softirq only if required. */
1764 13 : if (time_before(jiffies, base->next_expiry)) {
1765 : if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1766 : return;
1767 : /* CPU is awake, so check the deferrable base. */
1768 : base++;
1769 : if (time_before(jiffies, base->next_expiry))
1770 : return;
1771 : }
1772 0 : raise_softirq(TIMER_SOFTIRQ);
1773 : }
1774 :
1775 : /*
1776 : * Called from the timer interrupt handler to charge one tick to the current
1777 : * process. user_tick is 1 if the tick is user time, 0 for system.
1778 : */
1779 13 : void update_process_times(int user_tick)
1780 : {
1781 13 : struct task_struct *p = current;
1782 :
1783 26 : PRANDOM_ADD_NOISE(jiffies, user_tick, p, 0);
1784 :
1785 : /* Note: this timer irq context must be accounted for as well. */
1786 13 : account_process_tick(p, user_tick);
1787 13 : run_local_timers();
1788 13 : rcu_sched_clock_irq(user_tick);
1789 : #ifdef CONFIG_IRQ_WORK
1790 13 : if (in_irq())
1791 13 : irq_work_tick();
1792 : #endif
1793 13 : scheduler_tick();
1794 : if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1795 13 : run_posix_cpu_timers();
1796 13 : }
1797 :
1798 : /*
1799 : * Since schedule_timeout()'s timer is defined on the stack, it must store
1800 : * the target task on the stack as well.
1801 : */
1802 : struct process_timer {
1803 : struct timer_list timer;
1804 : struct task_struct *task;
1805 : };
1806 :
1807 0 : static void process_timeout(struct timer_list *t)
1808 : {
1809 0 : struct process_timer *timeout = from_timer(timeout, t, timer);
1810 :
1811 0 : wake_up_process(timeout->task);
1812 0 : }
1813 :
1814 : /**
1815 : * schedule_timeout - sleep until timeout
1816 : * @timeout: timeout value in jiffies
1817 : *
1818 : * Make the current task sleep until @timeout jiffies have elapsed.
1819 : * The function behavior depends on the current task state
1820 : * (see also set_current_state() description):
1821 : *
1822 : * %TASK_RUNNING - the scheduler is called, but the task does not sleep
1823 : * at all. That happens because sched_submit_work() does nothing for
1824 : * tasks in %TASK_RUNNING state.
1825 : *
1826 : * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1827 : * pass before the routine returns unless the current task is explicitly
1828 : * woken up, (e.g. by wake_up_process()).
1829 : *
1830 : * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1831 : * delivered to the current task or the current task is explicitly woken
1832 : * up.
1833 : *
1834 : * The current task state is guaranteed to be %TASK_RUNNING when this
1835 : * routine returns.
1836 : *
1837 : * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1838 : * the CPU away without a bound on the timeout. In this case the return
1839 : * value will be %MAX_SCHEDULE_TIMEOUT.
1840 : *
1841 : * Returns 0 when the timer has expired otherwise the remaining time in
1842 : * jiffies will be returned. In all cases the return value is guaranteed
1843 : * to be non-negative.
1844 : */
1845 204 : signed long __sched schedule_timeout(signed long timeout)
1846 : {
1847 : struct process_timer timer;
1848 : unsigned long expire;
1849 :
1850 204 : switch (timeout)
1851 : {
1852 : case MAX_SCHEDULE_TIMEOUT:
1853 : /*
1854 : * These two special cases are useful to be comfortable
1855 : * in the caller. Nothing more. We could take
1856 : * MAX_SCHEDULE_TIMEOUT from one of the negative value
1857 : * but I' d like to return a valid offset (>=0) to allow
1858 : * the caller to do everything it want with the retval.
1859 : */
1860 109 : schedule();
1861 109 : goto out;
1862 : default:
1863 : /*
1864 : * Another bit of PARANOID. Note that the retval will be
1865 : * 0 since no piece of kernel is supposed to do a check
1866 : * for a negative retval of schedule_timeout() (since it
1867 : * should never happens anyway). You just have the printk()
1868 : * that will tell you if something is gone wrong and where.
1869 : */
1870 95 : if (timeout < 0) {
1871 0 : printk(KERN_ERR "schedule_timeout: wrong timeout "
1872 : "value %lx\n", timeout);
1873 0 : dump_stack();
1874 0 : __set_current_state(TASK_RUNNING);
1875 0 : goto out;
1876 : }
1877 : }
1878 :
1879 95 : expire = timeout + jiffies;
1880 :
1881 95 : timer.task = current;
1882 190 : timer_setup_on_stack(&timer.timer, process_timeout, 0);
1883 95 : __mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
1884 95 : schedule();
1885 93 : del_singleshot_timer_sync(&timer.timer);
1886 :
1887 : /* Remove the timer from the object tracker */
1888 93 : destroy_timer_on_stack(&timer.timer);
1889 :
1890 93 : timeout = expire - jiffies;
1891 :
1892 : out:
1893 202 : return timeout < 0 ? 0 : timeout;
1894 : }
1895 : EXPORT_SYMBOL(schedule_timeout);
1896 :
1897 : /*
1898 : * We can use __set_current_state() here because schedule_timeout() calls
1899 : * schedule() unconditionally.
1900 : */
1901 0 : signed long __sched schedule_timeout_interruptible(signed long timeout)
1902 : {
1903 0 : __set_current_state(TASK_INTERRUPTIBLE);
1904 0 : return schedule_timeout(timeout);
1905 : }
1906 : EXPORT_SYMBOL(schedule_timeout_interruptible);
1907 :
1908 0 : signed long __sched schedule_timeout_killable(signed long timeout)
1909 : {
1910 0 : __set_current_state(TASK_KILLABLE);
1911 0 : return schedule_timeout(timeout);
1912 : }
1913 : EXPORT_SYMBOL(schedule_timeout_killable);
1914 :
1915 0 : signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1916 : {
1917 0 : __set_current_state(TASK_UNINTERRUPTIBLE);
1918 0 : return schedule_timeout(timeout);
1919 : }
1920 : EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1921 :
1922 : /*
1923 : * Like schedule_timeout_uninterruptible(), except this task will not contribute
1924 : * to load average.
1925 : */
1926 0 : signed long __sched schedule_timeout_idle(signed long timeout)
1927 : {
1928 0 : __set_current_state(TASK_IDLE);
1929 0 : return schedule_timeout(timeout);
1930 : }
1931 : EXPORT_SYMBOL(schedule_timeout_idle);
1932 :
1933 : #ifdef CONFIG_HOTPLUG_CPU
1934 : static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1935 : {
1936 : struct timer_list *timer;
1937 : int cpu = new_base->cpu;
1938 :
1939 : while (!hlist_empty(head)) {
1940 : timer = hlist_entry(head->first, struct timer_list, entry);
1941 : detach_timer(timer, false);
1942 : timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1943 : internal_add_timer(new_base, timer);
1944 : }
1945 : }
1946 :
1947 : int timers_prepare_cpu(unsigned int cpu)
1948 : {
1949 : struct timer_base *base;
1950 : int b;
1951 :
1952 : for (b = 0; b < NR_BASES; b++) {
1953 : base = per_cpu_ptr(&timer_bases[b], cpu);
1954 : base->clk = jiffies;
1955 : base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
1956 : base->timers_pending = false;
1957 : base->is_idle = false;
1958 : }
1959 : return 0;
1960 : }
1961 :
1962 : int timers_dead_cpu(unsigned int cpu)
1963 : {
1964 : struct timer_base *old_base;
1965 : struct timer_base *new_base;
1966 : int b, i;
1967 :
1968 : BUG_ON(cpu_online(cpu));
1969 :
1970 : for (b = 0; b < NR_BASES; b++) {
1971 : old_base = per_cpu_ptr(&timer_bases[b], cpu);
1972 : new_base = get_cpu_ptr(&timer_bases[b]);
1973 : /*
1974 : * The caller is globally serialized and nobody else
1975 : * takes two locks at once, deadlock is not possible.
1976 : */
1977 : raw_spin_lock_irq(&new_base->lock);
1978 : raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1979 :
1980 : /*
1981 : * The current CPUs base clock might be stale. Update it
1982 : * before moving the timers over.
1983 : */
1984 : forward_timer_base(new_base);
1985 :
1986 : BUG_ON(old_base->running_timer);
1987 :
1988 : for (i = 0; i < WHEEL_SIZE; i++)
1989 : migrate_timer_list(new_base, old_base->vectors + i);
1990 :
1991 : raw_spin_unlock(&old_base->lock);
1992 : raw_spin_unlock_irq(&new_base->lock);
1993 : put_cpu_ptr(&timer_bases);
1994 : }
1995 : return 0;
1996 : }
1997 :
1998 : #endif /* CONFIG_HOTPLUG_CPU */
1999 :
2000 1 : static void __init init_timer_cpu(int cpu)
2001 : {
2002 : struct timer_base *base;
2003 : int i;
2004 :
2005 2 : for (i = 0; i < NR_BASES; i++) {
2006 1 : base = per_cpu_ptr(&timer_bases[i], cpu);
2007 1 : base->cpu = cpu;
2008 : raw_spin_lock_init(&base->lock);
2009 1 : base->clk = jiffies;
2010 1 : base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2011 1 : timer_base_init_expiry_lock(base);
2012 : }
2013 1 : }
2014 :
2015 1 : static void __init init_timer_cpus(void)
2016 : {
2017 : int cpu;
2018 :
2019 2 : for_each_possible_cpu(cpu)
2020 1 : init_timer_cpu(cpu);
2021 1 : }
2022 :
2023 1 : void __init init_timers(void)
2024 : {
2025 1 : init_timer_cpus();
2026 : posix_cputimers_init_work();
2027 1 : open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2028 1 : }
2029 :
2030 : /**
2031 : * msleep - sleep safely even with waitqueue interruptions
2032 : * @msecs: Time in milliseconds to sleep for
2033 : */
2034 0 : void msleep(unsigned int msecs)
2035 : {
2036 0 : unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2037 :
2038 0 : while (timeout)
2039 0 : timeout = schedule_timeout_uninterruptible(timeout);
2040 0 : }
2041 :
2042 : EXPORT_SYMBOL(msleep);
2043 :
2044 : /**
2045 : * msleep_interruptible - sleep waiting for signals
2046 : * @msecs: Time in milliseconds to sleep for
2047 : */
2048 0 : unsigned long msleep_interruptible(unsigned int msecs)
2049 : {
2050 0 : unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2051 :
2052 0 : while (timeout && !signal_pending(current))
2053 0 : timeout = schedule_timeout_interruptible(timeout);
2054 0 : return jiffies_to_msecs(timeout);
2055 : }
2056 :
2057 : EXPORT_SYMBOL(msleep_interruptible);
2058 :
2059 : /**
2060 : * usleep_range_state - Sleep for an approximate time in a given state
2061 : * @min: Minimum time in usecs to sleep
2062 : * @max: Maximum time in usecs to sleep
2063 : * @state: State of the current task that will be while sleeping
2064 : *
2065 : * In non-atomic context where the exact wakeup time is flexible, use
2066 : * usleep_range_state() instead of udelay(). The sleep improves responsiveness
2067 : * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2068 : * power usage by allowing hrtimers to take advantage of an already-
2069 : * scheduled interrupt instead of scheduling a new one just for this sleep.
2070 : */
2071 0 : void __sched usleep_range_state(unsigned long min, unsigned long max,
2072 : unsigned int state)
2073 : {
2074 0 : ktime_t exp = ktime_add_us(ktime_get(), min);
2075 0 : u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2076 :
2077 : for (;;) {
2078 0 : __set_current_state(state);
2079 : /* Do not return before the requested sleep time has elapsed */
2080 0 : if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2081 : break;
2082 : }
2083 0 : }
2084 : EXPORT_SYMBOL(usleep_range_state);
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