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
timers_update_migration(void)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
timers_update_migration(void)238 static inline void timers_update_migration(void) { }
239 #endif /* !CONFIG_SMP */
240
timer_update_keys(struct work_struct * work)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
timers_update_nohz(void)249 void timers_update_nohz(void)
250 {
251 schedule_work(&timer_update_work);
252 }
253
timer_migration_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)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
is_timers_nohz_active(void)267 static inline bool is_timers_nohz_active(void)
268 {
269 return static_branch_unlikely(&timers_nohz_active);
270 }
271 #else
is_timers_nohz_active(void)272 static inline bool is_timers_nohz_active(void) { return false; }
273 #endif /* NO_HZ_COMMON */
274
round_jiffies_common(unsigned long j,int cpu,bool force_up)275 static unsigned long round_jiffies_common(unsigned long j, int cpu,
276 bool force_up)
277 {
278 int rem;
279 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 j += cpu * 3;
290
291 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 if (rem < HZ/4 && !force_up) /* round down */
301 j = j - rem;
302 else /* round up */
303 j = j - rem + HZ;
304
305 /* now that we have rounded, subtract the extra skew again */
306 j -= cpu * 3;
307
308 /*
309 * Make sure j is still in the future. Otherwise return the
310 * unmodified value.
311 */
312 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 */
__round_jiffies(unsigned long j,int cpu)335 unsigned long __round_jiffies(unsigned long j, int cpu)
336 {
337 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 */
__round_jiffies_relative(unsigned long j,int cpu)361 unsigned long __round_jiffies_relative(unsigned long j, int cpu)
362 {
363 unsigned long j0 = jiffies;
364
365 /* Use j0 because jiffies might change while we run */
366 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 */
round_jiffies(unsigned long j)385 unsigned long round_jiffies(unsigned long j)
386 {
387 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 */
round_jiffies_relative(unsigned long j)406 unsigned long round_jiffies_relative(unsigned long j)
407 {
408 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 */
__round_jiffies_up(unsigned long j,int cpu)422 unsigned long __round_jiffies_up(unsigned long j, int cpu)
423 {
424 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 */
__round_jiffies_up_relative(unsigned long j,int cpu)438 unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
439 {
440 unsigned long j0 = jiffies;
441
442 /* Use j0 because jiffies might change while we run */
443 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 */
round_jiffies_up(unsigned long j)456 unsigned long round_jiffies_up(unsigned long j)
457 {
458 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 */
round_jiffies_up_relative(unsigned long j)471 unsigned long round_jiffies_up_relative(unsigned long j)
472 {
473 return __round_jiffies_up_relative(j, raw_smp_processor_id());
474 }
475 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
476
477
timer_get_idx(struct timer_list * timer)478 static inline unsigned int timer_get_idx(struct timer_list *timer)
479 {
480 return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
481 }
482
timer_set_idx(struct timer_list * timer,unsigned int idx)483 static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
484 {
485 timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
486 idx << TIMER_ARRAYSHIFT;
487 }
488
489 /*
490 * Helper function to calculate the array index for a given expiry
491 * time.
492 */
calc_index(unsigned long expires,unsigned lvl,unsigned long * bucket_expiry)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 expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
506 *bucket_expiry = expires << LVL_SHIFT(lvl);
507 return LVL_OFFS(lvl) + (expires & LVL_MASK);
508 }
509
calc_wheel_index(unsigned long expires,unsigned long clk,unsigned long * bucket_expiry)510 static int calc_wheel_index(unsigned long expires, unsigned long clk,
511 unsigned long *bucket_expiry)
512 {
513 unsigned long delta = expires - clk;
514 unsigned int idx;
515
516 if (delta < LVL_START(1)) {
517 idx = calc_index(expires, 0, bucket_expiry);
518 } else if (delta < LVL_START(2)) {
519 idx = calc_index(expires, 1, bucket_expiry);
520 } else if (delta < LVL_START(3)) {
521 idx = calc_index(expires, 2, bucket_expiry);
522 } else if (delta < LVL_START(4)) {
523 idx = calc_index(expires, 3, bucket_expiry);
524 } else if (delta < LVL_START(5)) {
525 idx = calc_index(expires, 4, bucket_expiry);
526 } else if (delta < LVL_START(6)) {
527 idx = calc_index(expires, 5, bucket_expiry);
528 } else if (delta < LVL_START(7)) {
529 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 } else if ((long) delta < 0) {
533 idx = clk & LVL_MASK;
534 *bucket_expiry = clk;
535 } else {
536 /*
537 * Force expire obscene large timeouts to expire at the
538 * capacity limit of the wheel.
539 */
540 if (delta >= WHEEL_TIMEOUT_CUTOFF)
541 expires = clk + WHEEL_TIMEOUT_MAX;
542
543 idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
544 }
545 return idx;
546 }
547
548 static void
trigger_dyntick_cpu(struct timer_base * base,struct timer_list * timer)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 */
enqueue_timer(struct timer_base * base,struct timer_list * timer,unsigned int idx,unsigned long bucket_expiry)578 static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
579 unsigned int idx, unsigned long bucket_expiry)
580 {
581
582 hlist_add_head(&timer->entry, base->vectors + idx);
583 __set_bit(idx, base->pending_map);
584 timer_set_idx(timer, idx);
585
586 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 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 base->next_expiry = bucket_expiry;
599 base->timers_pending = true;
600 base->next_expiry_recalc = false;
601 trigger_dyntick_cpu(base, timer);
602 }
603 }
604
internal_add_timer(struct timer_base * base,struct timer_list * timer)605 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 idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry);
611 enqueue_timer(base, timer, idx, bucket_expiry);
612 }
613
614 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
615
616 static const struct debug_obj_descr timer_debug_descr;
617
timer_debug_hint(void * addr)618 static void *timer_debug_hint(void *addr)
619 {
620 return ((struct timer_list *) addr)->function;
621 }
622
timer_is_static_object(void * addr)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 */
timer_fixup_init(void * addr,enum debug_obj_state state)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. */
stub_timer(struct timer_list * unused)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 */
timer_fixup_activate(void * addr,enum debug_obj_state state)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 */
timer_fixup_free(void * addr,enum debug_obj_state state)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 */
timer_fixup_assert_init(void * addr,enum debug_obj_state state)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
debug_timer_init(struct timer_list * timer)722 static inline void debug_timer_init(struct timer_list *timer)
723 {
724 debug_object_init(timer, &timer_debug_descr);
725 }
726
debug_timer_activate(struct timer_list * timer)727 static inline void debug_timer_activate(struct timer_list *timer)
728 {
729 debug_object_activate(timer, &timer_debug_descr);
730 }
731
debug_timer_deactivate(struct timer_list * timer)732 static inline void debug_timer_deactivate(struct timer_list *timer)
733 {
734 debug_object_deactivate(timer, &timer_debug_descr);
735 }
736
debug_timer_assert_init(struct timer_list * timer)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
init_timer_on_stack_key(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)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
destroy_timer_on_stack(struct timer_list * timer)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
debug_timer_init(struct timer_list * timer)764 static inline void debug_timer_init(struct timer_list *timer) { }
debug_timer_activate(struct timer_list * timer)765 static inline void debug_timer_activate(struct timer_list *timer) { }
debug_timer_deactivate(struct timer_list * timer)766 static inline void debug_timer_deactivate(struct timer_list *timer) { }
debug_timer_assert_init(struct timer_list * timer)767 static inline void debug_timer_assert_init(struct timer_list *timer) { }
768 #endif
769
debug_init(struct timer_list * timer)770 static inline void debug_init(struct timer_list *timer)
771 {
772 debug_timer_init(timer);
773 trace_timer_init(timer);
774 }
775
debug_deactivate(struct timer_list * timer)776 static inline void debug_deactivate(struct timer_list *timer)
777 {
778 debug_timer_deactivate(timer);
779 trace_timer_cancel(timer);
780 }
781
debug_assert_init(struct timer_list * timer)782 static inline void debug_assert_init(struct timer_list *timer)
783 {
784 debug_timer_assert_init(timer);
785 }
786
do_init_timer(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)787 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 timer->entry.pprev = NULL;
793 timer->function = func;
794 if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
795 flags &= TIMER_INIT_FLAGS;
796 timer->flags = flags | raw_smp_processor_id();
797 lockdep_init_map(&timer->lockdep_map, name, key, 0);
798 }
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 */
init_timer_key(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)812 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 debug_init(timer);
817 do_init_timer(timer, func, flags, name, key);
818 }
819 EXPORT_SYMBOL(init_timer_key);
820
detach_timer(struct timer_list * timer,bool clear_pending)821 static inline void detach_timer(struct timer_list *timer, bool clear_pending)
822 {
823 struct hlist_node *entry = &timer->entry;
824
825 debug_deactivate(timer);
826
827 __hlist_del(entry);
828 if (clear_pending)
829 entry->pprev = NULL;
830 entry->next = LIST_POISON2;
831 }
832
detach_if_pending(struct timer_list * timer,struct timer_base * base,bool clear_pending)833 static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
834 bool clear_pending)
835 {
836 unsigned idx = timer_get_idx(timer);
837
838 if (!timer_pending(timer))
839 return 0;
840
841 if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
842 __clear_bit(idx, base->pending_map);
843 base->next_expiry_recalc = true;
844 }
845
846 detach_timer(timer, clear_pending);
847 return 1;
848 }
849
get_timer_cpu_base(u32 tflags,u32 cpu)850 static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
851 {
852 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
get_timer_this_cpu_base(u32 tflags)863 static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
864 {
865 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
get_timer_base(u32 tflags)876 static inline struct timer_base *get_timer_base(u32 tflags)
877 {
878 return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
879 }
880
881 static inline struct timer_base *
get_target_base(struct timer_base * base,unsigned tflags)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 return get_timer_this_cpu_base(tflags);
890 }
891
forward_timer_base(struct timer_base * base)892 static inline void forward_timer_base(struct timer_base *base)
893 {
894 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 jffies.
900 */
901 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 if (time_after(base->next_expiry, jnow)) {
909 base->clk = jnow;
910 } else {
911 if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
912 return;
913 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 */
lock_timer_base(struct timer_list * timer,unsigned long * flags)929 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 tf = READ_ONCE(timer->flags);
943
944 if (!(tf & TIMER_MIGRATING)) {
945 base = get_timer_base(tf);
946 raw_spin_lock_irqsave(&base->lock, *flags);
947 if (timer->flags == tf)
948 return base;
949 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
__mod_timer(struct timer_list * timer,unsigned long expires,unsigned int options)960 __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
961 {
962 unsigned long clk = 0, flags, bucket_expiry;
963 struct timer_base *base, *new_base;
964 unsigned int idx = UINT_MAX;
965 int ret = 0;
966
967 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 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 long diff = timer->expires - expires;
981
982 if (!diff)
983 return 1;
984 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 base = lock_timer_base(timer, &flags);
994 forward_timer_base(base);
995
996 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
997 time_before_eq(timer->expires, expires)) {
998 ret = 1;
999 goto out_unlock;
1000 }
1001
1002 clk = base->clk;
1003 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 if (idx == timer_get_idx(timer)) {
1011 if (!(options & MOD_TIMER_REDUCE))
1012 timer->expires = expires;
1013 else if (time_after(timer->expires, expires))
1014 timer->expires = expires;
1015 ret = 1;
1016 goto out_unlock;
1017 }
1018 } else {
1019 base = lock_timer_base(timer, &flags);
1020 forward_timer_base(base);
1021 }
1022
1023 ret = detach_if_pending(timer, base, false);
1024 if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1025 goto out_unlock;
1026
1027 new_base = get_target_base(base, timer->flags);
1028
1029 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 if (likely(base->running_timer != timer)) {
1038 /* See the comment in lock_timer_base() */
1039 timer->flags |= TIMER_MIGRATING;
1040
1041 raw_spin_unlock(&base->lock);
1042 base = new_base;
1043 raw_spin_lock(&base->lock);
1044 WRITE_ONCE(timer->flags,
1045 (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1046 forward_timer_base(base);
1047 }
1048 }
1049
1050 debug_timer_activate(timer);
1051
1052 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 if (idx != UINT_MAX && clk == base->clk)
1060 enqueue_timer(base, timer, idx, bucket_expiry);
1061 else
1062 internal_add_timer(base, timer);
1063
1064 out_unlock:
1065 raw_spin_unlock_irqrestore(&base->lock, flags);
1066
1067 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 */
mod_timer_pending(struct timer_list * timer,unsigned long expires)1080 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1081 {
1082 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 */
mod_timer(struct timer_list * timer,unsigned long expires)1106 int mod_timer(struct timer_list *timer, unsigned long expires)
1107 {
1108 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 */
timer_reduce(struct timer_list * timer,unsigned long expires)1121 int timer_reduce(struct timer_list *timer, unsigned long expires)
1122 {
1123 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 */
add_timer(struct timer_list * timer)1141 void add_timer(struct timer_list *timer)
1142 {
1143 BUG_ON(timer_pending(timer));
1144 __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1145 }
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 */
add_timer_on(struct timer_list * timer,int cpu)1155 void add_timer_on(struct timer_list *timer, int cpu)
1156 {
1157 struct timer_base *new_base, *base;
1158 unsigned long flags;
1159
1160 BUG_ON(timer_pending(timer) || !timer->function);
1161
1162 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 base = lock_timer_base(timer, &flags);
1170 if (base != new_base) {
1171 timer->flags |= TIMER_MIGRATING;
1172
1173 raw_spin_unlock(&base->lock);
1174 base = new_base;
1175 raw_spin_lock(&base->lock);
1176 WRITE_ONCE(timer->flags,
1177 (timer->flags & ~TIMER_BASEMASK) | cpu);
1178 }
1179 forward_timer_base(base);
1180
1181 debug_timer_activate(timer);
1182 internal_add_timer(base, timer);
1183 raw_spin_unlock_irqrestore(&base->lock, flags);
1184 }
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 */
del_timer(struct timer_list * timer)1198 int del_timer(struct timer_list *timer)
1199 {
1200 struct timer_base *base;
1201 unsigned long flags;
1202 int ret = 0;
1203
1204 debug_assert_init(timer);
1205
1206 if (timer_pending(timer)) {
1207 base = lock_timer_base(timer, &flags);
1208 ret = detach_if_pending(timer, base, true);
1209 raw_spin_unlock_irqrestore(&base->lock, flags);
1210 }
1211
1212 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 */
try_to_del_timer_sync(struct timer_list * timer)1223 int try_to_del_timer_sync(struct timer_list *timer)
1224 {
1225 struct timer_base *base;
1226 unsigned long flags;
1227 int ret = -1;
1228
1229 debug_assert_init(timer);
1230
1231 base = lock_timer_base(timer, &flags);
1232
1233 if (base->running_timer != timer)
1234 ret = detach_if_pending(timer, base, true);
1235
1236 raw_spin_unlock_irqrestore(&base->lock, flags);
1237
1238 return ret;
1239 }
1240 EXPORT_SYMBOL(try_to_del_timer_sync);
1241
1242 #ifdef CONFIG_PREEMPT_RT
timer_base_init_expiry_lock(struct timer_base * base)1243 static __init void timer_base_init_expiry_lock(struct timer_base *base)
1244 {
1245 spin_lock_init(&base->expiry_lock);
1246 }
1247
timer_base_lock_expiry(struct timer_base * base)1248 static inline void timer_base_lock_expiry(struct timer_base *base)
1249 {
1250 spin_lock(&base->expiry_lock);
1251 }
1252
timer_base_unlock_expiry(struct timer_base * base)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 reaquire it. That allows
1263 * the waiter to acquire the lock and make progress.
1264 */
timer_sync_wait_running(struct timer_base * base)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 */
del_timer_wait_running(struct timer_list * timer)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)) {
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
timer_base_init_expiry_lock(struct timer_base * base)1308 static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
timer_base_lock_expiry(struct timer_base * base)1309 static inline void timer_base_lock_expiry(struct timer_base *base) { }
timer_base_unlock_expiry(struct timer_base * base)1310 static inline void timer_base_unlock_expiry(struct timer_base *base) { }
timer_sync_wait_running(struct timer_base * base)1311 static inline void timer_sync_wait_running(struct timer_base *base) { }
del_timer_wait_running(struct timer_list * timer)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 */
del_timer_sync(struct timer_list * timer)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 do {
1375 ret = try_to_del_timer_sync(timer);
1376
1377 if (unlikely(ret < 0)) {
1378 del_timer_wait_running(timer);
1379 cpu_relax();
1380 }
1381 } while (ret < 0);
1382
1383 return ret;
1384 }
1385 EXPORT_SYMBOL(del_timer_sync);
1386 #endif
1387
call_timer_fn(struct timer_list * timer,void (* fn)(struct timer_list *),unsigned long baseclk)1388 static void call_timer_fn(struct timer_list *timer,
1389 void (*fn)(struct timer_list *),
1390 unsigned long baseclk)
1391 {
1392 int count = preempt_count();
1393
1394 #ifdef CONFIG_LOCKDEP
1395 /*
1396 * It is permissible to free the timer from inside the
1397 * function that is called from it, this we need to take into
1398 * account for lockdep too. To avoid bogus "held lock freed"
1399 * warnings as well as problems when looking into
1400 * timer->lockdep_map, make a copy and use that here.
1401 */
1402 struct lockdep_map lockdep_map;
1403
1404 lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1405 #endif
1406 /*
1407 * Couple the lock chain with the lock chain at
1408 * del_timer_sync() by acquiring the lock_map around the fn()
1409 * call here and in del_timer_sync().
1410 */
1411 lock_map_acquire(&lockdep_map);
1412
1413 trace_timer_expire_entry(timer, baseclk);
1414 fn(timer);
1415 trace_timer_expire_exit(timer);
1416
1417 lock_map_release(&lockdep_map);
1418
1419 if (count != preempt_count()) {
1420 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1421 fn, count, preempt_count());
1422 /*
1423 * Restore the preempt count. That gives us a decent
1424 * chance to survive and extract information. If the
1425 * callback kept a lock held, bad luck, but not worse
1426 * than the BUG() we had.
1427 */
1428 preempt_count_set(count);
1429 }
1430 }
1431
expire_timers(struct timer_base * base,struct hlist_head * head)1432 static void expire_timers(struct timer_base *base, struct hlist_head *head)
1433 {
1434 /*
1435 * This value is required only for tracing. base->clk was
1436 * incremented directly before expire_timers was called. But expiry
1437 * is related to the old base->clk value.
1438 */
1439 unsigned long baseclk = base->clk - 1;
1440
1441 while (!hlist_empty(head)) {
1442 struct timer_list *timer;
1443 void (*fn)(struct timer_list *);
1444
1445 timer = hlist_entry(head->first, struct timer_list, entry);
1446
1447 base->running_timer = timer;
1448 detach_timer(timer, true);
1449
1450 fn = timer->function;
1451
1452 if (timer->flags & TIMER_IRQSAFE) {
1453 raw_spin_unlock(&base->lock);
1454 call_timer_fn(timer, fn, baseclk);
1455 raw_spin_lock(&base->lock);
1456 base->running_timer = NULL;
1457 } else {
1458 raw_spin_unlock_irq(&base->lock);
1459 call_timer_fn(timer, fn, baseclk);
1460 raw_spin_lock_irq(&base->lock);
1461 base->running_timer = NULL;
1462 timer_sync_wait_running(base);
1463 }
1464 }
1465 }
1466
collect_expired_timers(struct timer_base * base,struct hlist_head * heads)1467 static int collect_expired_timers(struct timer_base *base,
1468 struct hlist_head *heads)
1469 {
1470 unsigned long clk = base->clk = base->next_expiry;
1471 struct hlist_head *vec;
1472 int i, levels = 0;
1473 unsigned int idx;
1474
1475 for (i = 0; i < LVL_DEPTH; i++) {
1476 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1477
1478 if (__test_and_clear_bit(idx, base->pending_map)) {
1479 vec = base->vectors + idx;
1480 hlist_move_list(vec, heads++);
1481 levels++;
1482 }
1483 /* Is it time to look at the next level? */
1484 if (clk & LVL_CLK_MASK)
1485 break;
1486 /* Shift clock for the next level granularity */
1487 clk >>= LVL_CLK_SHIFT;
1488 }
1489 return levels;
1490 }
1491
1492 /*
1493 * Find the next pending bucket of a level. Search from level start (@offset)
1494 * + @clk upwards and if nothing there, search from start of the level
1495 * (@offset) up to @offset + clk.
1496 */
next_pending_bucket(struct timer_base * base,unsigned offset,unsigned clk)1497 static int next_pending_bucket(struct timer_base *base, unsigned offset,
1498 unsigned clk)
1499 {
1500 unsigned pos, start = offset + clk;
1501 unsigned end = offset + LVL_SIZE;
1502
1503 pos = find_next_bit(base->pending_map, end, start);
1504 if (pos < end)
1505 return pos - start;
1506
1507 pos = find_next_bit(base->pending_map, start, offset);
1508 return pos < start ? pos + LVL_SIZE - start : -1;
1509 }
1510
1511 /*
1512 * Search the first expiring timer in the various clock levels. Caller must
1513 * hold base->lock.
1514 */
__next_timer_interrupt(struct timer_base * base)1515 static unsigned long __next_timer_interrupt(struct timer_base *base)
1516 {
1517 unsigned long clk, next, adj;
1518 unsigned lvl, offset = 0;
1519
1520 next = base->clk + NEXT_TIMER_MAX_DELTA;
1521 clk = base->clk;
1522 for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1523 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1524 unsigned long lvl_clk = clk & LVL_CLK_MASK;
1525
1526 if (pos >= 0) {
1527 unsigned long tmp = clk + (unsigned long) pos;
1528
1529 tmp <<= LVL_SHIFT(lvl);
1530 if (time_before(tmp, next))
1531 next = tmp;
1532
1533 /*
1534 * If the next expiration happens before we reach
1535 * the next level, no need to check further.
1536 */
1537 if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
1538 break;
1539 }
1540 /*
1541 * Clock for the next level. If the current level clock lower
1542 * bits are zero, we look at the next level as is. If not we
1543 * need to advance it by one because that's going to be the
1544 * next expiring bucket in that level. base->clk is the next
1545 * expiring jiffie. So in case of:
1546 *
1547 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1548 * 0 0 0 0 0 0
1549 *
1550 * we have to look at all levels @index 0. With
1551 *
1552 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1553 * 0 0 0 0 0 2
1554 *
1555 * LVL0 has the next expiring bucket @index 2. The upper
1556 * levels have the next expiring bucket @index 1.
1557 *
1558 * In case that the propagation wraps the next level the same
1559 * rules apply:
1560 *
1561 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1562 * 0 0 0 0 F 2
1563 *
1564 * So after looking at LVL0 we get:
1565 *
1566 * LVL5 LVL4 LVL3 LVL2 LVL1
1567 * 0 0 0 1 0
1568 *
1569 * So no propagation from LVL1 to LVL2 because that happened
1570 * with the add already, but then we need to propagate further
1571 * from LVL2 to LVL3.
1572 *
1573 * So the simple check whether the lower bits of the current
1574 * level are 0 or not is sufficient for all cases.
1575 */
1576 adj = lvl_clk ? 1 : 0;
1577 clk >>= LVL_CLK_SHIFT;
1578 clk += adj;
1579 }
1580
1581 base->next_expiry_recalc = false;
1582 base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
1583
1584 return next;
1585 }
1586
1587 #ifdef CONFIG_NO_HZ_COMMON
1588 /*
1589 * Check, if the next hrtimer event is before the next timer wheel
1590 * event:
1591 */
cmp_next_hrtimer_event(u64 basem,u64 expires)1592 static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1593 {
1594 u64 nextevt = hrtimer_get_next_event();
1595
1596 /*
1597 * If high resolution timers are enabled
1598 * hrtimer_get_next_event() returns KTIME_MAX.
1599 */
1600 if (expires <= nextevt)
1601 return expires;
1602
1603 /*
1604 * If the next timer is already expired, return the tick base
1605 * time so the tick is fired immediately.
1606 */
1607 if (nextevt <= basem)
1608 return basem;
1609
1610 /*
1611 * Round up to the next jiffie. High resolution timers are
1612 * off, so the hrtimers are expired in the tick and we need to
1613 * make sure that this tick really expires the timer to avoid
1614 * a ping pong of the nohz stop code.
1615 *
1616 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1617 */
1618 return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1619 }
1620
1621 /**
1622 * get_next_timer_interrupt - return the time (clock mono) of the next timer
1623 * @basej: base time jiffies
1624 * @basem: base time clock monotonic
1625 *
1626 * Returns the tick aligned clock monotonic time of the next pending
1627 * timer or KTIME_MAX if no timer is pending.
1628 */
get_next_timer_interrupt(unsigned long basej,u64 basem)1629 u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1630 {
1631 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1632 u64 expires = KTIME_MAX;
1633 unsigned long nextevt;
1634
1635 /*
1636 * Pretend that there is no timer pending if the cpu is offline.
1637 * Possible pending timers will be migrated later to an active cpu.
1638 */
1639 if (cpu_is_offline(smp_processor_id()))
1640 return expires;
1641
1642 raw_spin_lock(&base->lock);
1643 if (base->next_expiry_recalc)
1644 base->next_expiry = __next_timer_interrupt(base);
1645 nextevt = base->next_expiry;
1646
1647 /*
1648 * We have a fresh next event. Check whether we can forward the
1649 * base. We can only do that when @basej is past base->clk
1650 * otherwise we might rewind base->clk.
1651 */
1652 if (time_after(basej, base->clk)) {
1653 if (time_after(nextevt, basej))
1654 base->clk = basej;
1655 else if (time_after(nextevt, base->clk))
1656 base->clk = nextevt;
1657 }
1658
1659 if (time_before_eq(nextevt, basej)) {
1660 expires = basem;
1661 base->is_idle = false;
1662 } else {
1663 if (base->timers_pending)
1664 expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1665 /*
1666 * If we expect to sleep more than a tick, mark the base idle.
1667 * Also the tick is stopped so any added timer must forward
1668 * the base clk itself to keep granularity small. This idle
1669 * logic is only maintained for the BASE_STD base, deferrable
1670 * timers may still see large granularity skew (by design).
1671 */
1672 if ((expires - basem) > TICK_NSEC)
1673 base->is_idle = true;
1674 }
1675 raw_spin_unlock(&base->lock);
1676
1677 return cmp_next_hrtimer_event(basem, expires);
1678 }
1679
1680 /**
1681 * timer_clear_idle - Clear the idle state of the timer base
1682 *
1683 * Called with interrupts disabled
1684 */
timer_clear_idle(void)1685 void timer_clear_idle(void)
1686 {
1687 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1688
1689 /*
1690 * We do this unlocked. The worst outcome is a remote enqueue sending
1691 * a pointless IPI, but taking the lock would just make the window for
1692 * sending the IPI a few instructions smaller for the cost of taking
1693 * the lock in the exit from idle path.
1694 */
1695 base->is_idle = false;
1696 }
1697 #endif
1698
1699 /*
1700 * Called from the timer interrupt handler to charge one tick to the current
1701 * process. user_tick is 1 if the tick is user time, 0 for system.
1702 */
update_process_times(int user_tick)1703 void update_process_times(int user_tick)
1704 {
1705 struct task_struct *p = current;
1706
1707 PRANDOM_ADD_NOISE(jiffies, user_tick, p, 0);
1708
1709 /* Note: this timer irq context must be accounted for as well. */
1710 account_process_tick(p, user_tick);
1711 run_local_timers();
1712 rcu_sched_clock_irq(user_tick);
1713 #ifdef CONFIG_IRQ_WORK
1714 if (in_irq())
1715 irq_work_tick();
1716 #endif
1717 scheduler_tick();
1718 if (IS_ENABLED(CONFIG_POSIX_TIMERS))
1719 run_posix_cpu_timers();
1720 }
1721
1722 /**
1723 * __run_timers - run all expired timers (if any) on this CPU.
1724 * @base: the timer vector to be processed.
1725 */
__run_timers(struct timer_base * base)1726 static inline void __run_timers(struct timer_base *base)
1727 {
1728 struct hlist_head heads[LVL_DEPTH];
1729 int levels;
1730
1731 if (time_before(jiffies, base->next_expiry))
1732 return;
1733
1734 timer_base_lock_expiry(base);
1735 raw_spin_lock_irq(&base->lock);
1736
1737 while (time_after_eq(jiffies, base->clk) &&
1738 time_after_eq(jiffies, base->next_expiry)) {
1739 levels = collect_expired_timers(base, heads);
1740 /*
1741 * The two possible reasons for not finding any expired
1742 * timer at this clk are that all matching timers have been
1743 * dequeued or no timer has been queued since
1744 * base::next_expiry was set to base::clk +
1745 * NEXT_TIMER_MAX_DELTA.
1746 */
1747 WARN_ON_ONCE(!levels && !base->next_expiry_recalc
1748 && base->timers_pending);
1749 base->clk++;
1750 base->next_expiry = __next_timer_interrupt(base);
1751
1752 while (levels--)
1753 expire_timers(base, heads + levels);
1754 }
1755 raw_spin_unlock_irq(&base->lock);
1756 timer_base_unlock_expiry(base);
1757 }
1758
1759 /*
1760 * This function runs timers and the timer-tq in bottom half context.
1761 */
run_timer_softirq(struct softirq_action * h)1762 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1763 {
1764 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1765
1766 __run_timers(base);
1767 if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
1768 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
1769 }
1770
1771 /*
1772 * Called by the local, per-CPU timer interrupt on SMP.
1773 */
run_local_timers(void)1774 void run_local_timers(void)
1775 {
1776 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1777
1778 hrtimer_run_queues();
1779 /* Raise the softirq only if required. */
1780 if (time_before(jiffies, base->next_expiry)) {
1781 if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
1782 return;
1783 /* CPU is awake, so check the deferrable base. */
1784 base++;
1785 if (time_before(jiffies, base->next_expiry))
1786 return;
1787 }
1788 raise_softirq(TIMER_SOFTIRQ);
1789 }
1790
1791 /*
1792 * Since schedule_timeout()'s timer is defined on the stack, it must store
1793 * the target task on the stack as well.
1794 */
1795 struct process_timer {
1796 struct timer_list timer;
1797 struct task_struct *task;
1798 };
1799
process_timeout(struct timer_list * t)1800 static void process_timeout(struct timer_list *t)
1801 {
1802 struct process_timer *timeout = from_timer(timeout, t, timer);
1803
1804 wake_up_process(timeout->task);
1805 }
1806
1807 /**
1808 * schedule_timeout - sleep until timeout
1809 * @timeout: timeout value in jiffies
1810 *
1811 * Make the current task sleep until @timeout jiffies have elapsed.
1812 * The function behavior depends on the current task state
1813 * (see also set_current_state() description):
1814 *
1815 * %TASK_RUNNING - the scheduler is called, but the task does not sleep
1816 * at all. That happens because sched_submit_work() does nothing for
1817 * tasks in %TASK_RUNNING state.
1818 *
1819 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1820 * pass before the routine returns unless the current task is explicitly
1821 * woken up, (e.g. by wake_up_process()).
1822 *
1823 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1824 * delivered to the current task or the current task is explicitly woken
1825 * up.
1826 *
1827 * The current task state is guaranteed to be %TASK_RUNNING when this
1828 * routine returns.
1829 *
1830 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1831 * the CPU away without a bound on the timeout. In this case the return
1832 * value will be %MAX_SCHEDULE_TIMEOUT.
1833 *
1834 * Returns 0 when the timer has expired otherwise the remaining time in
1835 * jiffies will be returned. In all cases the return value is guaranteed
1836 * to be non-negative.
1837 */
schedule_timeout(signed long timeout)1838 signed long __sched schedule_timeout(signed long timeout)
1839 {
1840 struct process_timer timer;
1841 unsigned long expire;
1842
1843 switch (timeout)
1844 {
1845 case MAX_SCHEDULE_TIMEOUT:
1846 /*
1847 * These two special cases are useful to be comfortable
1848 * in the caller. Nothing more. We could take
1849 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1850 * but I' d like to return a valid offset (>=0) to allow
1851 * the caller to do everything it want with the retval.
1852 */
1853 schedule();
1854 goto out;
1855 default:
1856 /*
1857 * Another bit of PARANOID. Note that the retval will be
1858 * 0 since no piece of kernel is supposed to do a check
1859 * for a negative retval of schedule_timeout() (since it
1860 * should never happens anyway). You just have the printk()
1861 * that will tell you if something is gone wrong and where.
1862 */
1863 if (timeout < 0) {
1864 printk(KERN_ERR "schedule_timeout: wrong timeout "
1865 "value %lx\n", timeout);
1866 dump_stack();
1867 current->state = TASK_RUNNING;
1868 goto out;
1869 }
1870 }
1871
1872 expire = timeout + jiffies;
1873
1874 timer.task = current;
1875 timer_setup_on_stack(&timer.timer, process_timeout, 0);
1876 __mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
1877 schedule();
1878 del_singleshot_timer_sync(&timer.timer);
1879
1880 /* Remove the timer from the object tracker */
1881 destroy_timer_on_stack(&timer.timer);
1882
1883 timeout = expire - jiffies;
1884
1885 out:
1886 return timeout < 0 ? 0 : timeout;
1887 }
1888 EXPORT_SYMBOL(schedule_timeout);
1889
1890 /*
1891 * We can use __set_current_state() here because schedule_timeout() calls
1892 * schedule() unconditionally.
1893 */
schedule_timeout_interruptible(signed long timeout)1894 signed long __sched schedule_timeout_interruptible(signed long timeout)
1895 {
1896 __set_current_state(TASK_INTERRUPTIBLE);
1897 return schedule_timeout(timeout);
1898 }
1899 EXPORT_SYMBOL(schedule_timeout_interruptible);
1900
schedule_timeout_killable(signed long timeout)1901 signed long __sched schedule_timeout_killable(signed long timeout)
1902 {
1903 __set_current_state(TASK_KILLABLE);
1904 return schedule_timeout(timeout);
1905 }
1906 EXPORT_SYMBOL(schedule_timeout_killable);
1907
schedule_timeout_uninterruptible(signed long timeout)1908 signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1909 {
1910 __set_current_state(TASK_UNINTERRUPTIBLE);
1911 return schedule_timeout(timeout);
1912 }
1913 EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1914
1915 /*
1916 * Like schedule_timeout_uninterruptible(), except this task will not contribute
1917 * to load average.
1918 */
schedule_timeout_idle(signed long timeout)1919 signed long __sched schedule_timeout_idle(signed long timeout)
1920 {
1921 __set_current_state(TASK_IDLE);
1922 return schedule_timeout(timeout);
1923 }
1924 EXPORT_SYMBOL(schedule_timeout_idle);
1925
1926 #ifdef CONFIG_HOTPLUG_CPU
1927
1928 #ifdef CONFIG_CPU_ISOLATION_OPT
migrate_timer_list(struct timer_base * new_base,struct hlist_head * head,bool remove_pinned)1929 static void migrate_timer_list(struct timer_base *new_base,
1930 struct hlist_head *head, bool remove_pinned)
1931 {
1932 struct timer_list *timer;
1933 int cpu = new_base->cpu;
1934 struct hlist_node *n;
1935 int is_pinned;
1936
1937 hlist_for_each_entry_safe(timer, n, head, entry) {
1938 is_pinned = timer->flags & TIMER_PINNED;
1939 if (!remove_pinned && is_pinned)
1940 continue;
1941
1942 detach_if_pending(timer, get_timer_base(timer->flags), false);
1943 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1944 internal_add_timer(new_base, timer);
1945 }
1946 }
1947
__migrate_timers(unsigned int cpu,bool remove_pinned)1948 static void __migrate_timers(unsigned int cpu, bool remove_pinned)
1949 {
1950 struct timer_base *old_base;
1951 struct timer_base *new_base;
1952 unsigned long flags;
1953 int b, i;
1954
1955 for (b = 0; b < NR_BASES; b++) {
1956 old_base = per_cpu_ptr(&timer_bases[b], cpu);
1957 new_base = get_cpu_ptr(&timer_bases[b]);
1958 /*
1959 * The caller is globally serialized and nobody else
1960 * takes two locks at once, deadlock is not possible.
1961 */
1962 raw_spin_lock_irqsave(&new_base->lock, flags);
1963 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1964
1965 /*
1966 * The current CPUs base clock might be stale. Update it
1967 * before moving the timers over.
1968 */
1969 forward_timer_base(new_base);
1970
1971 if (!cpu_online(cpu))
1972 BUG_ON(old_base->running_timer);
1973
1974 for (i = 0; i < WHEEL_SIZE; i++)
1975 migrate_timer_list(new_base, old_base->vectors + i,
1976 remove_pinned);
1977
1978 raw_spin_unlock(&old_base->lock);
1979 raw_spin_unlock_irqrestore(&new_base->lock, flags);
1980 put_cpu_ptr(&timer_bases);
1981 }
1982 }
1983
1984 #else
1985
migrate_timer_list(struct timer_base * new_base,struct hlist_head * head)1986 static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
1987 {
1988 struct timer_list *timer;
1989 int cpu = new_base->cpu;
1990
1991 while (!hlist_empty(head)) {
1992 timer = hlist_entry(head->first, struct timer_list, entry);
1993 detach_timer(timer, false);
1994 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
1995 internal_add_timer(new_base, timer);
1996 }
1997 }
1998
1999 #endif /* CONFIG_CPU_ISOLATION_OPT */
2000
timers_prepare_cpu(unsigned int cpu)2001 int timers_prepare_cpu(unsigned int cpu)
2002 {
2003 struct timer_base *base;
2004 int b;
2005
2006 for (b = 0; b < NR_BASES; b++) {
2007 base = per_cpu_ptr(&timer_bases[b], cpu);
2008 base->clk = jiffies;
2009 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2010 base->timers_pending = false;
2011 base->is_idle = false;
2012 }
2013 return 0;
2014 }
2015
2016 #ifdef CONFIG_CPU_ISOLATION_OPT
timers_dead_cpu(unsigned int cpu)2017 int timers_dead_cpu(unsigned int cpu)
2018 {
2019 BUG_ON(cpu_online(cpu));
2020 __migrate_timers(cpu, true);
2021 return 0;
2022 }
2023
timer_quiesce_cpu(void * cpup)2024 void timer_quiesce_cpu(void *cpup)
2025 {
2026 __migrate_timers(*(unsigned int *)cpup, false);
2027 }
2028
2029 #else
2030
timers_dead_cpu(unsigned int cpu)2031 int timers_dead_cpu(unsigned int cpu)
2032 {
2033 struct timer_base *old_base;
2034 struct timer_base *new_base;
2035 int b, i;
2036
2037 BUG_ON(cpu_online(cpu));
2038
2039 for (b = 0; b < NR_BASES; b++) {
2040 old_base = per_cpu_ptr(&timer_bases[b], cpu);
2041 new_base = get_cpu_ptr(&timer_bases[b]);
2042 /*
2043 * The caller is globally serialized and nobody else
2044 * takes two locks at once, deadlock is not possible.
2045 */
2046 raw_spin_lock_irq(&new_base->lock);
2047 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
2048
2049 /*
2050 * The current CPUs base clock might be stale. Update it
2051 * before moving the timers over.
2052 */
2053 forward_timer_base(new_base);
2054
2055 BUG_ON(old_base->running_timer);
2056
2057 for (i = 0; i < WHEEL_SIZE; i++)
2058 migrate_timer_list(new_base, old_base->vectors + i);
2059
2060 raw_spin_unlock(&old_base->lock);
2061 raw_spin_unlock_irq(&new_base->lock);
2062 put_cpu_ptr(&timer_bases);
2063 }
2064 return 0;
2065 }
2066
2067 #endif /* CONFIG_CPU_ISOLATION_OPT */
2068
2069 #endif /* CONFIG_HOTPLUG_CPU */
2070
init_timer_cpu(int cpu)2071 static void __init init_timer_cpu(int cpu)
2072 {
2073 struct timer_base *base;
2074 int i;
2075
2076 for (i = 0; i < NR_BASES; i++) {
2077 base = per_cpu_ptr(&timer_bases[i], cpu);
2078 base->cpu = cpu;
2079 raw_spin_lock_init(&base->lock);
2080 base->clk = jiffies;
2081 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2082 timer_base_init_expiry_lock(base);
2083 }
2084 }
2085
init_timer_cpus(void)2086 static void __init init_timer_cpus(void)
2087 {
2088 int cpu;
2089
2090 for_each_possible_cpu(cpu)
2091 init_timer_cpu(cpu);
2092 }
2093
init_timers(void)2094 void __init init_timers(void)
2095 {
2096 init_timer_cpus();
2097 posix_cputimers_init_work();
2098 open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2099 }
2100
2101 /**
2102 * msleep - sleep safely even with waitqueue interruptions
2103 * @msecs: Time in milliseconds to sleep for
2104 */
msleep(unsigned int msecs)2105 void msleep(unsigned int msecs)
2106 {
2107 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2108
2109 while (timeout)
2110 timeout = schedule_timeout_uninterruptible(timeout);
2111 }
2112
2113 EXPORT_SYMBOL(msleep);
2114
2115 /**
2116 * msleep_interruptible - sleep waiting for signals
2117 * @msecs: Time in milliseconds to sleep for
2118 */
msleep_interruptible(unsigned int msecs)2119 unsigned long msleep_interruptible(unsigned int msecs)
2120 {
2121 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2122
2123 while (timeout && !signal_pending(current))
2124 timeout = schedule_timeout_interruptible(timeout);
2125 return jiffies_to_msecs(timeout);
2126 }
2127
2128 EXPORT_SYMBOL(msleep_interruptible);
2129
2130 /**
2131 * usleep_range - Sleep for an approximate time
2132 * @min: Minimum time in usecs to sleep
2133 * @max: Maximum time in usecs to sleep
2134 *
2135 * In non-atomic context where the exact wakeup time is flexible, use
2136 * usleep_range() instead of udelay(). The sleep improves responsiveness
2137 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2138 * power usage by allowing hrtimers to take advantage of an already-
2139 * scheduled interrupt instead of scheduling a new one just for this sleep.
2140 */
usleep_range(unsigned long min,unsigned long max)2141 void __sched usleep_range(unsigned long min, unsigned long max)
2142 {
2143 ktime_t exp = ktime_add_us(ktime_get(), min);
2144 u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2145
2146 for (;;) {
2147 __set_current_state(TASK_UNINTERRUPTIBLE);
2148 /* Do not return before the requested sleep time has elapsed */
2149 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2150 break;
2151 }
2152 }
2153 EXPORT_SYMBOL(usleep_range);
2154