projects/linux·blob v6.19 · refs

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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright(C) 2005-2006, Linutronix GmbH, Thomas Gleixner <[email protected]>
4 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
5 * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
6 *
7 * High-resolution kernel timers
8 *
9 * In contrast to the low-resolution timeout API, aka timer wheel,
10 * hrtimers provide finer resolution and accuracy depending on system
11 * configuration and capabilities.
12 *
13 * Started by: Thomas Gleixner and Ingo Molnar
14 *
15 * Credits:
16 * Based on the original timer wheel code
17 *
18 * Help, testing, suggestions, bugfixes, improvements were
19 * provided by:
20 *
21 * George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
22 * et. al.
23 */
24
25#include <linux/cpu.h>
26#include <linux/export.h>
27#include <linux/percpu.h>
28#include <linux/hrtimer.h>
29#include <linux/notifier.h>
30#include <linux/syscalls.h>
31#include <linux/interrupt.h>
32#include <linux/tick.h>
33#include <linux/err.h>
34#include <linux/debugobjects.h>
35#include <linux/sched/signal.h>
36#include <linux/sched/sysctl.h>
37#include <linux/sched/rt.h>
38#include <linux/sched/deadline.h>
39#include <linux/sched/nohz.h>
40#include <linux/sched/debug.h>
41#include <linux/sched/isolation.h>
42#include <linux/timer.h>
43#include <linux/freezer.h>
44#include <linux/compat.h>
45
46#include <linux/uaccess.h>
47
48#include <trace/events/timer.h>
49
50#include "tick-internal.h"
51
52/*
53 * Masks for selecting the soft and hard context timers from
54 * cpu_base->active
55 */
56#define MASK_SHIFT (HRTIMER_BASE_MONOTONIC_SOFT)
57#define HRTIMER_ACTIVE_HARD ((1U << MASK_SHIFT) - 1)
58#define HRTIMER_ACTIVE_SOFT (HRTIMER_ACTIVE_HARD << MASK_SHIFT)
59#define HRTIMER_ACTIVE_ALL (HRTIMER_ACTIVE_SOFT | HRTIMER_ACTIVE_HARD)
60
61static void retrigger_next_event(void *arg);
62static ktime_t __hrtimer_cb_get_time(clockid_t clock_id);
63
64/*
65 * The timer bases:
66 *
67 * There are more clockids than hrtimer bases. Thus, we index
68 * into the timer bases by the hrtimer_base_type enum. When trying
69 * to reach a base using a clockid, hrtimer_clockid_to_base()
70 * is used to convert from clockid to the proper hrtimer_base_type.
71 */
72DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
73{
74 .lock = __RAW_SPIN_LOCK_UNLOCKED(hrtimer_bases.lock),
75 .clock_base =
76 {
77 {
78 .index = HRTIMER_BASE_MONOTONIC,
79 .clockid = CLOCK_MONOTONIC,
80 },
81 {
82 .index = HRTIMER_BASE_REALTIME,
83 .clockid = CLOCK_REALTIME,
84 },
85 {
86 .index = HRTIMER_BASE_BOOTTIME,
87 .clockid = CLOCK_BOOTTIME,
88 },
89 {
90 .index = HRTIMER_BASE_TAI,
91 .clockid = CLOCK_TAI,
92 },
93 {
94 .index = HRTIMER_BASE_MONOTONIC_SOFT,
95 .clockid = CLOCK_MONOTONIC,
96 },
97 {
98 .index = HRTIMER_BASE_REALTIME_SOFT,
99 .clockid = CLOCK_REALTIME,
100 },
101 {
102 .index = HRTIMER_BASE_BOOTTIME_SOFT,
103 .clockid = CLOCK_BOOTTIME,
104 },
105 {
106 .index = HRTIMER_BASE_TAI_SOFT,
107 .clockid = CLOCK_TAI,
108 },
109 },
110 .csd = CSD_INIT(retrigger_next_event, NULL)
111};
112
113static inline bool hrtimer_base_is_online(struct hrtimer_cpu_base *base)
114{
115 if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
116 return true;
117 else
118 return likely(base->online);
119}
120
121/*
122 * Functions and macros which are different for UP/SMP systems are kept in a
123 * single place
124 */
125#ifdef CONFIG_SMP
126
127/*
128 * We require the migration_base for lock_hrtimer_base()/switch_hrtimer_base()
129 * such that hrtimer_callback_running() can unconditionally dereference
130 * timer->base->cpu_base
131 */
132static struct hrtimer_cpu_base migration_cpu_base = {
133 .clock_base = { {
134 .cpu_base = &migration_cpu_base,
135 .seq = SEQCNT_RAW_SPINLOCK_ZERO(migration_cpu_base.seq,
136 &migration_cpu_base.lock),
137 }, },
138};
139
140#define migration_base migration_cpu_base.clock_base[0]
141
142/*
143 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
144 * means that all timers which are tied to this base via timer->base are
145 * locked, and the base itself is locked too.
146 *
147 * So __run_timers/migrate_timers can safely modify all timers which could
148 * be found on the lists/queues.
149 *
150 * When the timer's base is locked, and the timer removed from list, it is
151 * possible to set timer->base = &migration_base and drop the lock: the timer
152 * remains locked.
153 */
154static
155struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
156 unsigned long *flags)
157 __acquires(&timer->base->lock)
158{
159 struct hrtimer_clock_base *base;
160
161 for (;;) {
162 base = READ_ONCE(timer->base);
163 if (likely(base != &migration_base)) {
164 raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
165 if (likely(base == timer->base))
166 return base;
167 /* The timer has migrated to another CPU: */
168 raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
169 }
170 cpu_relax();
171 }
172}
173
174/*
175 * Check if the elected target is suitable considering its next
176 * event and the hotplug state of the current CPU.
177 *
178 * If the elected target is remote and its next event is after the timer
179 * to queue, then a remote reprogram is necessary. However there is no
180 * guarantee the IPI handling the operation would arrive in time to meet
181 * the high resolution deadline. In this case the local CPU becomes a
182 * preferred target, unless it is offline.
183 *
184 * High and low resolution modes are handled the same way for simplicity.
185 *
186 * Called with cpu_base->lock of target cpu held.
187 */
188static bool hrtimer_suitable_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base,
189 struct hrtimer_cpu_base *new_cpu_base,
190 struct hrtimer_cpu_base *this_cpu_base)
191{
192 ktime_t expires;
193
194 /*
195 * The local CPU clockevent can be reprogrammed. Also get_target_base()
196 * guarantees it is online.
197 */
198 if (new_cpu_base == this_cpu_base)
199 return true;
200
201 /*
202 * The offline local CPU can't be the default target if the
203 * next remote target event is after this timer. Keep the
204 * elected new base. An IPI will be issued to reprogram
205 * it as a last resort.
206 */
207 if (!hrtimer_base_is_online(this_cpu_base))
208 return true;
209
210 expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset);
211
212 return expires >= new_base->cpu_base->expires_next;
213}
214
215static inline struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base, int pinned)
216{
217 if (!hrtimer_base_is_online(base)) {
218 int cpu = cpumask_any_and(cpu_online_mask, housekeeping_cpumask(HK_TYPE_TIMER));
219
220 return &per_cpu(hrtimer_bases, cpu);
221 }
222
223#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
224 if (static_branch_likely(&timers_migration_enabled) && !pinned)
225 return &per_cpu(hrtimer_bases, get_nohz_timer_target());
226#endif
227 return base;
228}
229
230/*
231 * We switch the timer base to a power-optimized selected CPU target,
232 * if:
233 * - NO_HZ_COMMON is enabled
234 * - timer migration is enabled
235 * - the timer callback is not running
236 * - the timer is not the first expiring timer on the new target
237 *
238 * If one of the above requirements is not fulfilled we move the timer
239 * to the current CPU or leave it on the previously assigned CPU if
240 * the timer callback is currently running.
241 */
242static inline struct hrtimer_clock_base *
243switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
244 int pinned)
245{
246 struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
247 struct hrtimer_clock_base *new_base;
248 int basenum = base->index;
249
250 this_cpu_base = this_cpu_ptr(&hrtimer_bases);
251 new_cpu_base = get_target_base(this_cpu_base, pinned);
252again:
253 new_base = &new_cpu_base->clock_base[basenum];
254
255 if (base != new_base) {
256 /*
257 * We are trying to move timer to new_base.
258 * However we can't change timer's base while it is running,
259 * so we keep it on the same CPU. No hassle vs. reprogramming
260 * the event source in the high resolution case. The softirq
261 * code will take care of this when the timer function has
262 * completed. There is no conflict as we hold the lock until
263 * the timer is enqueued.
264 */
265 if (unlikely(hrtimer_callback_running(timer)))
266 return base;
267
268 /* See the comment in lock_hrtimer_base() */
269 WRITE_ONCE(timer->base, &migration_base);
270 raw_spin_unlock(&base->cpu_base->lock);
271 raw_spin_lock(&new_base->cpu_base->lock);
272
273 if (!hrtimer_suitable_target(timer, new_base, new_cpu_base,
274 this_cpu_base)) {
275 raw_spin_unlock(&new_base->cpu_base->lock);
276 raw_spin_lock(&base->cpu_base->lock);
277 new_cpu_base = this_cpu_base;
278 WRITE_ONCE(timer->base, base);
279 goto again;
280 }
281 WRITE_ONCE(timer->base, new_base);
282 } else {
283 if (!hrtimer_suitable_target(timer, new_base, new_cpu_base, this_cpu_base)) {
284 new_cpu_base = this_cpu_base;
285 goto again;
286 }
287 }
288 return new_base;
289}
290
291#else /* CONFIG_SMP */
292
293static inline struct hrtimer_clock_base *
294lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
295 __acquires(&timer->base->cpu_base->lock)
296{
297 struct hrtimer_clock_base *base = timer->base;
298
299 raw_spin_lock_irqsave(&base->cpu_base->lock, *flags);
300
301 return base;
302}
303
304# define switch_hrtimer_base(t, b, p) (b)
305
306#endif /* !CONFIG_SMP */
307
308/*
309 * Functions for the union type storage format of ktime_t which are
310 * too large for inlining:
311 */
312#if BITS_PER_LONG < 64
313/*
314 * Divide a ktime value by a nanosecond value
315 */
316s64 __ktime_divns(const ktime_t kt, s64 div)
317{
318 int sft = 0;
319 s64 dclc;
320 u64 tmp;
321
322 dclc = ktime_to_ns(kt);
323 tmp = dclc < 0 ? -dclc : dclc;
324
325 /* Make sure the divisor is less than 2^32: */
326 while (div >> 32) {
327 sft++;
328 div >>= 1;
329 }
330 tmp >>= sft;
331 do_div(tmp, (u32) div);
332 return dclc < 0 ? -tmp : tmp;
333}
334EXPORT_SYMBOL_GPL(__ktime_divns);
335#endif /* BITS_PER_LONG >= 64 */
336
337/*
338 * Add two ktime values and do a safety check for overflow:
339 */
340ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
341{
342 ktime_t res = ktime_add_unsafe(lhs, rhs);
343
344 /*
345 * We use KTIME_SEC_MAX here, the maximum timeout which we can
346 * return to user space in a timespec:
347 */
348 if (res < 0 || res < lhs || res < rhs)
349 res = ktime_set(KTIME_SEC_MAX, 0);
350
351 return res;
352}
353
354EXPORT_SYMBOL_GPL(ktime_add_safe);
355
356#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
357
358static const struct debug_obj_descr hrtimer_debug_descr;
359
360static void *hrtimer_debug_hint(void *addr)
361{
362 return ACCESS_PRIVATE((struct hrtimer *)addr, function);
363}
364
365/*
366 * fixup_init is called when:
367 * - an active object is initialized
368 */
369static bool hrtimer_fixup_init(void *addr, enum debug_obj_state state)
370{
371 struct hrtimer *timer = addr;
372
373 switch (state) {
374 case ODEBUG_STATE_ACTIVE:
375 hrtimer_cancel(timer);
376 debug_object_init(timer, &hrtimer_debug_descr);
377 return true;
378 default:
379 return false;
380 }
381}
382
383/*
384 * fixup_activate is called when:
385 * - an active object is activated
386 * - an unknown non-static object is activated
387 */
388static bool hrtimer_fixup_activate(void *addr, enum debug_obj_state state)
389{
390 switch (state) {
391 case ODEBUG_STATE_ACTIVE:
392 WARN_ON(1);
393 fallthrough;
394 default:
395 return false;
396 }
397}
398
399/*
400 * fixup_free is called when:
401 * - an active object is freed
402 */
403static bool hrtimer_fixup_free(void *addr, enum debug_obj_state state)
404{
405 struct hrtimer *timer = addr;
406
407 switch (state) {
408 case ODEBUG_STATE_ACTIVE:
409 hrtimer_cancel(timer);
410 debug_object_free(timer, &hrtimer_debug_descr);
411 return true;
412 default:
413 return false;
414 }
415}
416
417static const struct debug_obj_descr hrtimer_debug_descr = {
418 .name = "hrtimer",
419 .debug_hint = hrtimer_debug_hint,
420 .fixup_init = hrtimer_fixup_init,
421 .fixup_activate = hrtimer_fixup_activate,
422 .fixup_free = hrtimer_fixup_free,
423};
424
425static inline void debug_hrtimer_init(struct hrtimer *timer)
426{
427 debug_object_init(timer, &hrtimer_debug_descr);
428}
429
430static inline void debug_hrtimer_init_on_stack(struct hrtimer *timer)
431{
432 debug_object_init_on_stack(timer, &hrtimer_debug_descr);
433}
434
435static inline void debug_hrtimer_activate(struct hrtimer *timer,
436 enum hrtimer_mode mode)
437{
438 debug_object_activate(timer, &hrtimer_debug_descr);
439}
440
441static inline void debug_hrtimer_deactivate(struct hrtimer *timer)
442{
443 debug_object_deactivate(timer, &hrtimer_debug_descr);
444}
445
446void destroy_hrtimer_on_stack(struct hrtimer *timer)
447{
448 debug_object_free(timer, &hrtimer_debug_descr);
449}
450EXPORT_SYMBOL_GPL(destroy_hrtimer_on_stack);
451
452#else
453
454static inline void debug_hrtimer_init(struct hrtimer *timer) { }
455static inline void debug_hrtimer_init_on_stack(struct hrtimer *timer) { }
456static inline void debug_hrtimer_activate(struct hrtimer *timer,
457 enum hrtimer_mode mode) { }
458static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
459#endif
460
461static inline void debug_setup(struct hrtimer *timer, clockid_t clockid, enum hrtimer_mode mode)
462{
463 debug_hrtimer_init(timer);
464 trace_hrtimer_setup(timer, clockid, mode);
465}
466
467static inline void debug_setup_on_stack(struct hrtimer *timer, clockid_t clockid,
468 enum hrtimer_mode mode)
469{
470 debug_hrtimer_init_on_stack(timer);
471 trace_hrtimer_setup(timer, clockid, mode);
472}
473
474static inline void debug_activate(struct hrtimer *timer,
475 enum hrtimer_mode mode)
476{
477 debug_hrtimer_activate(timer, mode);
478 trace_hrtimer_start(timer, mode);
479}
480
481static inline void debug_deactivate(struct hrtimer *timer)
482{
483 debug_hrtimer_deactivate(timer);
484 trace_hrtimer_cancel(timer);
485}
486
487static struct hrtimer_clock_base *
488__next_base(struct hrtimer_cpu_base *cpu_base, unsigned int *active)
489{
490 unsigned int idx;
491
492 if (!*active)
493 return NULL;
494
495 idx = __ffs(*active);
496 *active &= ~(1U << idx);
497
498 return &cpu_base->clock_base[idx];
499}
500
501#define for_each_active_base(base, cpu_base, active) \
502 while ((base = __next_base((cpu_base), &(active))))
503
504static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
505 const struct hrtimer *exclude,
506 unsigned int active,
507 ktime_t expires_next)
508{
509 struct hrtimer_clock_base *base;
510 ktime_t expires;
511
512 for_each_active_base(base, cpu_base, active) {
513 struct timerqueue_node *next;
514 struct hrtimer *timer;
515
516 next = timerqueue_getnext(&base->active);
517 timer = container_of(next, struct hrtimer, node);
518 if (timer == exclude) {
519 /* Get to the next timer in the queue. */
520 next = timerqueue_iterate_next(next);
521 if (!next)
522 continue;
523
524 timer = container_of(next, struct hrtimer, node);
525 }
526 expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
527 if (expires < expires_next) {
528 expires_next = expires;
529
530 /* Skip cpu_base update if a timer is being excluded. */
531 if (exclude)
532 continue;
533
534 if (timer->is_soft)
535 cpu_base->softirq_next_timer = timer;
536 else
537 cpu_base->next_timer = timer;
538 }
539 }
540 /*
541 * clock_was_set() might have changed base->offset of any of
542 * the clock bases so the result might be negative. Fix it up
543 * to prevent a false positive in clockevents_program_event().
544 */
545 if (expires_next < 0)
546 expires_next = 0;
547 return expires_next;
548}
549
550/*
551 * Recomputes cpu_base::*next_timer and returns the earliest expires_next
552 * but does not set cpu_base::*expires_next, that is done by
553 * hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
554 * cpu_base::*expires_next right away, reprogramming logic would no longer
555 * work.
556 *
557 * When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
558 * those timers will get run whenever the softirq gets handled, at the end of
559 * hrtimer_run_softirq(), hrtimer_update_softirq_timer() will re-add these bases.
560 *
561 * Therefore softirq values are those from the HRTIMER_ACTIVE_SOFT clock bases.
562 * The !softirq values are the minima across HRTIMER_ACTIVE_ALL, unless an actual
563 * softirq is pending, in which case they're the minima of HRTIMER_ACTIVE_HARD.
564 *
565 * @active_mask must be one of:
566 * - HRTIMER_ACTIVE_ALL,
567 * - HRTIMER_ACTIVE_SOFT, or
568 * - HRTIMER_ACTIVE_HARD.
569 */
570static ktime_t
571__hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_mask)
572{
573 unsigned int active;
574 struct hrtimer *next_timer = NULL;
575 ktime_t expires_next = KTIME_MAX;
576
577 if (!cpu_base->softirq_activated && (active_mask & HRTIMER_ACTIVE_SOFT)) {
578 active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
579 cpu_base->softirq_next_timer = NULL;
580 expires_next = __hrtimer_next_event_base(cpu_base, NULL,
581 active, KTIME_MAX);
582
583 next_timer = cpu_base->softirq_next_timer;
584 }
585
586 if (active_mask & HRTIMER_ACTIVE_HARD) {
587 active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
588 cpu_base->next_timer = next_timer;
589 expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
590 expires_next);
591 }
592
593 return expires_next;
594}
595
596static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
597{
598 ktime_t expires_next, soft = KTIME_MAX;
599
600 /*
601 * If the soft interrupt has already been activated, ignore the
602 * soft bases. They will be handled in the already raised soft
603 * interrupt.
604 */
605 if (!cpu_base->softirq_activated) {
606 soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
607 /*
608 * Update the soft expiry time. clock_settime() might have
609 * affected it.
610 */
611 cpu_base->softirq_expires_next = soft;
612 }
613
614 expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
615 /*
616 * If a softirq timer is expiring first, update cpu_base->next_timer
617 * and program the hardware with the soft expiry time.
618 */
619 if (expires_next > soft) {
620 cpu_base->next_timer = cpu_base->softirq_next_timer;
621 expires_next = soft;
622 }
623
624 return expires_next;
625}
626
627static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
628{
629 ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
630 ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
631 ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
632
633 ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
634 offs_real, offs_boot, offs_tai);
635
636 base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
637 base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
638 base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
639
640 return now;
641}
642
643/*
644 * Is the high resolution mode active ?
645 */
646static inline int hrtimer_hres_active(struct hrtimer_cpu_base *cpu_base)
647{
648 return IS_ENABLED(CONFIG_HIGH_RES_TIMERS) ?
649 cpu_base->hres_active : 0;
650}
651
652static void __hrtimer_reprogram(struct hrtimer_cpu_base *cpu_base,
653 struct hrtimer *next_timer,
654 ktime_t expires_next)
655{
656 cpu_base->expires_next = expires_next;
657
658 /*
659 * If hres is not active, hardware does not have to be
660 * reprogrammed yet.
661 *
662 * If a hang was detected in the last timer interrupt then we
663 * leave the hang delay active in the hardware. We want the
664 * system to make progress. That also prevents the following
665 * scenario:
666 * T1 expires 50ms from now
667 * T2 expires 5s from now
668 *
669 * T1 is removed, so this code is called and would reprogram
670 * the hardware to 5s from now. Any hrtimer_start after that
671 * will not reprogram the hardware due to hang_detected being
672 * set. So we'd effectively block all timers until the T2 event
673 * fires.
674 */
675 if (!hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
676 return;
677
678 tick_program_event(expires_next, 1);
679}
680
681/*
682 * Reprogram the event source with checking both queues for the
683 * next event
684 * Called with interrupts disabled and base->lock held
685 */
686static void
687hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
688{
689 ktime_t expires_next;
690
691 expires_next = hrtimer_update_next_event(cpu_base);
692
693 if (skip_equal && expires_next == cpu_base->expires_next)
694 return;
695
696 __hrtimer_reprogram(cpu_base, cpu_base->next_timer, expires_next);
697}
698
699/* High resolution timer related functions */
700#ifdef CONFIG_HIGH_RES_TIMERS
701
702/*
703 * High resolution timer enabled ?
704 */
705static bool hrtimer_hres_enabled __read_mostly = true;
706unsigned int hrtimer_resolution __read_mostly = LOW_RES_NSEC;
707EXPORT_SYMBOL_GPL(hrtimer_resolution);
708
709/*
710 * Enable / Disable high resolution mode
711 */
712static int __init setup_hrtimer_hres(char *str)
713{
714 return (kstrtobool(str, &hrtimer_hres_enabled) == 0);
715}
716
717__setup("highres=", setup_hrtimer_hres);
718
719/*
720 * hrtimer_high_res_enabled - query, if the highres mode is enabled
721 */
722static inline int hrtimer_is_hres_enabled(void)
723{
724 return hrtimer_hres_enabled;
725}
726
727/*
728 * Switch to high resolution mode
729 */
730static void hrtimer_switch_to_hres(void)
731{
732 struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
733
734 if (tick_init_highres()) {
735 pr_warn("Could not switch to high resolution mode on CPU %u\n",
736 base->cpu);
737 return;
738 }
739 base->hres_active = 1;
740 hrtimer_resolution = HIGH_RES_NSEC;
741
742 tick_setup_sched_timer(true);
743 /* "Retrigger" the interrupt to get things going */
744 retrigger_next_event(NULL);
745}
746
747#else
748
749static inline int hrtimer_is_hres_enabled(void) { return 0; }
750static inline void hrtimer_switch_to_hres(void) { }
751
752#endif /* CONFIG_HIGH_RES_TIMERS */
753/*
754 * Retrigger next event is called after clock was set with interrupts
755 * disabled through an SMP function call or directly from low level
756 * resume code.
757 *
758 * This is only invoked when:
759 * - CONFIG_HIGH_RES_TIMERS is enabled.
760 * - CONFIG_NOHZ_COMMON is enabled
761 *
762 * For the other cases this function is empty and because the call sites
763 * are optimized out it vanishes as well, i.e. no need for lots of
764 * #ifdeffery.
765 */
766static void retrigger_next_event(void *arg)
767{
768 struct hrtimer_cpu_base *base = this_cpu_ptr(&hrtimer_bases);
769
770 /*
771 * When high resolution mode or nohz is active, then the offsets of
772 * CLOCK_REALTIME/TAI/BOOTTIME have to be updated. Otherwise the
773 * next tick will take care of that.
774 *
775 * If high resolution mode is active then the next expiring timer
776 * must be reevaluated and the clock event device reprogrammed if
777 * necessary.
778 *
779 * In the NOHZ case the update of the offset and the reevaluation
780 * of the next expiring timer is enough. The return from the SMP
781 * function call will take care of the reprogramming in case the
782 * CPU was in a NOHZ idle sleep.
783 *
784 * In periodic low resolution mode, the next softirq expiration
785 * must also be updated.
786 */
787 raw_spin_lock(&base->lock);
788 hrtimer_update_base(base);
789 if (hrtimer_hres_active(base))
790 hrtimer_force_reprogram(base, 0);
791 else
792 hrtimer_update_next_event(base);
793 raw_spin_unlock(&base->lock);
794}
795
796/*
797 * When a timer is enqueued and expires earlier than the already enqueued
798 * timers, we have to check, whether it expires earlier than the timer for
799 * which the clock event device was armed.
800 *
801 * Called with interrupts disabled and base->cpu_base.lock held
802 */
803static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
804{
805 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
806 struct hrtimer_clock_base *base = timer->base;
807 ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
808
809 WARN_ON_ONCE(hrtimer_get_expires_tv64(timer) < 0);
810
811 /*
812 * CLOCK_REALTIME timer might be requested with an absolute
813 * expiry time which is less than base->offset. Set it to 0.
814 */
815 if (expires < 0)
816 expires = 0;
817
818 if (timer->is_soft) {
819 /*
820 * soft hrtimer could be started on a remote CPU. In this
821 * case softirq_expires_next needs to be updated on the
822 * remote CPU. The soft hrtimer will not expire before the
823 * first hard hrtimer on the remote CPU -
824 * hrtimer_check_target() prevents this case.
825 */
826 struct hrtimer_cpu_base *timer_cpu_base = base->cpu_base;
827
828 if (timer_cpu_base->softirq_activated)
829 return;
830
831 if (!ktime_before(expires, timer_cpu_base->softirq_expires_next))
832 return;
833
834 timer_cpu_base->softirq_next_timer = timer;
835 timer_cpu_base->softirq_expires_next = expires;
836
837 if (!ktime_before(expires, timer_cpu_base->expires_next) ||
838 !reprogram)
839 return;
840 }
841
842 /*
843 * If the timer is not on the current cpu, we cannot reprogram
844 * the other cpus clock event device.
845 */
846 if (base->cpu_base != cpu_base)
847 return;
848
849 if (expires >= cpu_base->expires_next)
850 return;
851
852 /*
853 * If the hrtimer interrupt is running, then it will reevaluate the
854 * clock bases and reprogram the clock event device.
855 */
856 if (cpu_base->in_hrtirq)
857 return;
858
859 cpu_base->next_timer = timer;
860
861 __hrtimer_reprogram(cpu_base, timer, expires);
862}
863
864static bool update_needs_ipi(struct hrtimer_cpu_base *cpu_base,
865 unsigned int active)
866{
867 struct hrtimer_clock_base *base;
868 unsigned int seq;
869 ktime_t expires;
870
871 /*
872 * Update the base offsets unconditionally so the following
873 * checks whether the SMP function call is required works.
874 *
875 * The update is safe even when the remote CPU is in the hrtimer
876 * interrupt or the hrtimer soft interrupt and expiring affected
877 * bases. Either it will see the update before handling a base or
878 * it will see it when it finishes the processing and reevaluates
879 * the next expiring timer.
880 */
881 seq = cpu_base->clock_was_set_seq;
882 hrtimer_update_base(cpu_base);
883
884 /*
885 * If the sequence did not change over the update then the
886 * remote CPU already handled it.
887 */
888 if (seq == cpu_base->clock_was_set_seq)
889 return false;
890
891 /*
892 * If the remote CPU is currently handling an hrtimer interrupt, it
893 * will reevaluate the first expiring timer of all clock bases
894 * before reprogramming. Nothing to do here.
895 */
896 if (cpu_base->in_hrtirq)
897 return false;
898
899 /*
900 * Walk the affected clock bases and check whether the first expiring
901 * timer in a clock base is moving ahead of the first expiring timer of
902 * @cpu_base. If so, the IPI must be invoked because per CPU clock
903 * event devices cannot be remotely reprogrammed.
904 */
905 active &= cpu_base->active_bases;
906
907 for_each_active_base(base, cpu_base, active) {
908 struct timerqueue_node *next;
909
910 next = timerqueue_getnext(&base->active);
911 expires = ktime_sub(next->expires, base->offset);
912 if (expires < cpu_base->expires_next)
913 return true;
914
915 /* Extra check for softirq clock bases */
916 if (base->index < HRTIMER_BASE_MONOTONIC_SOFT)
917 continue;
918 if (cpu_base->softirq_activated)
919 continue;
920 if (expires < cpu_base->softirq_expires_next)
921 return true;
922 }
923 return false;
924}
925
926/*
927 * Clock was set. This might affect CLOCK_REALTIME, CLOCK_TAI and
928 * CLOCK_BOOTTIME (for late sleep time injection).
929 *
930 * This requires to update the offsets for these clocks
931 * vs. CLOCK_MONOTONIC. When high resolution timers are enabled, then this
932 * also requires to eventually reprogram the per CPU clock event devices
933 * when the change moves an affected timer ahead of the first expiring
934 * timer on that CPU. Obviously remote per CPU clock event devices cannot
935 * be reprogrammed. The other reason why an IPI has to be sent is when the
936 * system is in !HIGH_RES and NOHZ mode. The NOHZ mode updates the offsets
937 * in the tick, which obviously might be stopped, so this has to bring out
938 * the remote CPU which might sleep in idle to get this sorted.
939 */
940void clock_was_set(unsigned int bases)
941{
942 struct hrtimer_cpu_base *cpu_base = raw_cpu_ptr(&hrtimer_bases);
943 cpumask_var_t mask;
944 int cpu;
945
946 if (!hrtimer_hres_active(cpu_base) && !tick_nohz_active)
947 goto out_timerfd;
948
949 if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
950 on_each_cpu(retrigger_next_event, NULL, 1);
951 goto out_timerfd;
952 }
953
954 /* Avoid interrupting CPUs if possible */
955 cpus_read_lock();
956 for_each_online_cpu(cpu) {
957 unsigned long flags;
958
959 cpu_base = &per_cpu(hrtimer_bases, cpu);
960 raw_spin_lock_irqsave(&cpu_base->lock, flags);
961
962 if (update_needs_ipi(cpu_base, bases))
963 cpumask_set_cpu(cpu, mask);
964
965 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
966 }
967
968 preempt_disable();
969 smp_call_function_many(mask, retrigger_next_event, NULL, 1);
970 preempt_enable();
971 cpus_read_unlock();
972 free_cpumask_var(mask);
973
974out_timerfd:
975 timerfd_clock_was_set();
976}
977
978static void clock_was_set_work(struct work_struct *work)
979{
980 clock_was_set(CLOCK_SET_WALL);
981}
982
983static DECLARE_WORK(hrtimer_work, clock_was_set_work);
984
985/*
986 * Called from timekeeping code to reprogram the hrtimer interrupt device
987 * on all cpus and to notify timerfd.
988 */
989void clock_was_set_delayed(void)
990{
991 schedule_work(&hrtimer_work);
992}
993
994/*
995 * Called during resume either directly from via timekeeping_resume()
996 * or in the case of s2idle from tick_unfreeze() to ensure that the
997 * hrtimers are up to date.
998 */
999void hrtimers_resume_local(void)
1000{
1001 lockdep_assert_irqs_disabled();
1002 /* Retrigger on the local CPU */
1003 retrigger_next_event(NULL);
1004}
1005
1006/*
1007 * Counterpart to lock_hrtimer_base above:
1008 */
1009static inline
1010void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
1011 __releases(&timer->base->cpu_base->lock)
1012{
1013 raw_spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
1014}
1015
1016/**
1017 * hrtimer_forward() - forward the timer expiry
1018 * @timer: hrtimer to forward
1019 * @now: forward past this time
1020 * @interval: the interval to forward
1021 *
1022 * Forward the timer expiry so it will expire in the future.
1023 *
1024 * .. note::
1025 * This only updates the timer expiry value and does not requeue the timer.
1026 *
1027 * There is also a variant of the function hrtimer_forward_now().
1028 *
1029 * Context: Can be safely called from the callback function of @timer. If called
1030 * from other contexts @timer must neither be enqueued nor running the
1031 * callback and the caller needs to take care of serialization.
1032 *
1033 * Return: The number of overruns are returned.
1034 */
1035u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
1036{
1037 u64 orun = 1;
1038 ktime_t delta;
1039
1040 delta = ktime_sub(now, hrtimer_get_expires(timer));
1041
1042 if (delta < 0)
1043 return 0;
1044
1045 if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
1046 return 0;
1047
1048 if (interval < hrtimer_resolution)
1049 interval = hrtimer_resolution;
1050
1051 if (unlikely(delta >= interval)) {
1052 s64 incr = ktime_to_ns(interval);
1053
1054 orun = ktime_divns(delta, incr);
1055 hrtimer_add_expires_ns(timer, incr * orun);
1056 if (hrtimer_get_expires_tv64(timer) > now)
1057 return orun;
1058 /*
1059 * This (and the ktime_add() below) is the
1060 * correction for exact:
1061 */
1062 orun++;
1063 }
1064 hrtimer_add_expires(timer, interval);
1065
1066 return orun;
1067}
1068EXPORT_SYMBOL_GPL(hrtimer_forward);
1069
1070/*
1071 * enqueue_hrtimer - internal function to (re)start a timer
1072 *
1073 * The timer is inserted in expiry order. Insertion into the
1074 * red black tree is O(log(n)). Must hold the base lock.
1075 *
1076 * Returns true when the new timer is the leftmost timer in the tree.
1077 */
1078static bool enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
1079 enum hrtimer_mode mode)
1080{
1081 debug_activate(timer, mode);
1082 WARN_ON_ONCE(!base->cpu_base->online);
1083
1084 base->cpu_base->active_bases |= 1 << base->index;
1085
1086 /* Pairs with the lockless read in hrtimer_is_queued() */
1087 WRITE_ONCE(timer->state, HRTIMER_STATE_ENQUEUED);
1088
1089 return timerqueue_add(&base->active, &timer->node);
1090}
1091
1092/*
1093 * __remove_hrtimer - internal function to remove a timer
1094 *
1095 * Caller must hold the base lock.
1096 *
1097 * High resolution timer mode reprograms the clock event device when the
1098 * timer is the one which expires next. The caller can disable this by setting
1099 * reprogram to zero. This is useful, when the context does a reprogramming
1100 * anyway (e.g. timer interrupt)
1101 */
1102static void __remove_hrtimer(struct hrtimer *timer,
1103 struct hrtimer_clock_base *base,
1104 u8 newstate, int reprogram)
1105{
1106 struct hrtimer_cpu_base *cpu_base = base->cpu_base;
1107 u8 state = timer->state;
1108
1109 /* Pairs with the lockless read in hrtimer_is_queued() */
1110 WRITE_ONCE(timer->state, newstate);
1111 if (!(state & HRTIMER_STATE_ENQUEUED))
1112 return;
1113
1114 if (!timerqueue_del(&base->active, &timer->node))
1115 cpu_base->active_bases &= ~(1 << base->index);
1116
1117 /*
1118 * Note: If reprogram is false we do not update
1119 * cpu_base->next_timer. This happens when we remove the first
1120 * timer on a remote cpu. No harm as we never dereference
1121 * cpu_base->next_timer. So the worst thing what can happen is
1122 * an superfluous call to hrtimer_force_reprogram() on the
1123 * remote cpu later on if the same timer gets enqueued again.
1124 */
1125 if (reprogram && timer == cpu_base->next_timer)
1126 hrtimer_force_reprogram(cpu_base, 1);
1127}
1128
1129/*
1130 * remove hrtimer, called with base lock held
1131 */
1132static inline int
1133remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
1134 bool restart, bool keep_local)
1135{
1136 u8 state = timer->state;
1137
1138 if (state & HRTIMER_STATE_ENQUEUED) {
1139 bool reprogram;
1140
1141 /*
1142 * Remove the timer and force reprogramming when high
1143 * resolution mode is active and the timer is on the current
1144 * CPU. If we remove a timer on another CPU, reprogramming is
1145 * skipped. The interrupt event on this CPU is fired and
1146 * reprogramming happens in the interrupt handler. This is a
1147 * rare case and less expensive than a smp call.
1148 */
1149 debug_deactivate(timer);
1150 reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);
1151
1152 /*
1153 * If the timer is not restarted then reprogramming is
1154 * required if the timer is local. If it is local and about
1155 * to be restarted, avoid programming it twice (on removal
1156 * and a moment later when it's requeued).
1157 */
1158 if (!restart)
1159 state = HRTIMER_STATE_INACTIVE;
1160 else
1161 reprogram &= !keep_local;
1162
1163 __remove_hrtimer(timer, base, state, reprogram);
1164 return 1;
1165 }
1166 return 0;
1167}
1168
1169static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim,
1170 const enum hrtimer_mode mode)
1171{
1172#ifdef CONFIG_TIME_LOW_RES
1173 /*
1174 * CONFIG_TIME_LOW_RES indicates that the system has no way to return
1175 * granular time values. For relative timers we add hrtimer_resolution
1176 * (i.e. one jiffy) to prevent short timeouts.
1177 */
1178 timer->is_rel = mode & HRTIMER_MODE_REL;
1179 if (timer->is_rel)
1180 tim = ktime_add_safe(tim, hrtimer_resolution);
1181#endif
1182 return tim;
1183}
1184
1185static void
1186hrtimer_update_softirq_timer(struct hrtimer_cpu_base *cpu_base, bool reprogram)
1187{
1188 ktime_t expires;
1189
1190 /*
1191 * Find the next SOFT expiration.
1192 */
1193 expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
1194
1195 /*
1196 * reprogramming needs to be triggered, even if the next soft
1197 * hrtimer expires at the same time than the next hard
1198 * hrtimer. cpu_base->softirq_expires_next needs to be updated!
1199 */
1200 if (expires == KTIME_MAX)
1201 return;
1202
1203 /*
1204 * cpu_base->*next_timer is recomputed by __hrtimer_get_next_event()
1205 * cpu_base->*expires_next is only set by hrtimer_reprogram()
1206 */
1207 hrtimer_reprogram(cpu_base->softirq_next_timer, reprogram);
1208}
1209
1210static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
1211 u64 delta_ns, const enum hrtimer_mode mode,
1212 struct hrtimer_clock_base *base)
1213{
1214 struct hrtimer_cpu_base *this_cpu_base = this_cpu_ptr(&hrtimer_bases);
1215 struct hrtimer_clock_base *new_base;
1216 bool force_local, first;
1217
1218 /*
1219 * If the timer is on the local cpu base and is the first expiring
1220 * timer then this might end up reprogramming the hardware twice
1221 * (on removal and on enqueue). To avoid that by prevent the
1222 * reprogram on removal, keep the timer local to the current CPU
1223 * and enforce reprogramming after it is queued no matter whether
1224 * it is the new first expiring timer again or not.
1225 */
1226 force_local = base->cpu_base == this_cpu_base;
1227 force_local &= base->cpu_base->next_timer == timer;
1228
1229 /*
1230 * Don't force local queuing if this enqueue happens on a unplugged
1231 * CPU after hrtimer_cpu_dying() has been invoked.
1232 */
1233 force_local &= this_cpu_base->online;
1234
1235 /*
1236 * Remove an active timer from the queue. In case it is not queued
1237 * on the current CPU, make sure that remove_hrtimer() updates the
1238 * remote data correctly.
1239 *
1240 * If it's on the current CPU and the first expiring timer, then
1241 * skip reprogramming, keep the timer local and enforce
1242 * reprogramming later if it was the first expiring timer. This
1243 * avoids programming the underlying clock event twice (once at
1244 * removal and once after enqueue).
1245 */
1246 remove_hrtimer(timer, base, true, force_local);
1247
1248 if (mode & HRTIMER_MODE_REL)
1249 tim = ktime_add_safe(tim, __hrtimer_cb_get_time(base->clockid));
1250
1251 tim = hrtimer_update_lowres(timer, tim, mode);
1252
1253 hrtimer_set_expires_range_ns(timer, tim, delta_ns);
1254
1255 /* Switch the timer base, if necessary: */
1256 if (!force_local) {
1257 new_base = switch_hrtimer_base(timer, base,
1258 mode & HRTIMER_MODE_PINNED);
1259 } else {
1260 new_base = base;
1261 }
1262
1263 first = enqueue_hrtimer(timer, new_base, mode);
1264 if (!force_local) {
1265 /*
1266 * If the current CPU base is online, then the timer is
1267 * never queued on a remote CPU if it would be the first
1268 * expiring timer there.
1269 */
1270 if (hrtimer_base_is_online(this_cpu_base))
1271 return first;
1272
1273 /*
1274 * Timer was enqueued remote because the current base is
1275 * already offline. If the timer is the first to expire,
1276 * kick the remote CPU to reprogram the clock event.
1277 */
1278 if (first) {
1279 struct hrtimer_cpu_base *new_cpu_base = new_base->cpu_base;
1280
1281 smp_call_function_single_async(new_cpu_base->cpu, &new_cpu_base->csd);
1282 }
1283 return 0;
1284 }
1285
1286 /*
1287 * Timer was forced to stay on the current CPU to avoid
1288 * reprogramming on removal and enqueue. Force reprogram the
1289 * hardware by evaluating the new first expiring timer.
1290 */
1291 hrtimer_force_reprogram(new_base->cpu_base, 1);
1292 return 0;
1293}
1294
1295/**
1296 * hrtimer_start_range_ns - (re)start an hrtimer
1297 * @timer: the timer to be added
1298 * @tim: expiry time
1299 * @delta_ns: "slack" range for the timer
1300 * @mode: timer mode: absolute (HRTIMER_MODE_ABS) or
1301 * relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
1302 * softirq based mode is considered for debug purpose only!
1303 */
1304void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
1305 u64 delta_ns, const enum hrtimer_mode mode)
1306{
1307 struct hrtimer_clock_base *base;
1308 unsigned long flags;
1309
1310 /*
1311 * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
1312 * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
1313 * expiry mode because unmarked timers are moved to softirq expiry.
1314 */
1315 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
1316 WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
1317 else
1318 WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
1319
1320 base = lock_hrtimer_base(timer, &flags);
1321
1322 if (__hrtimer_start_range_ns(timer, tim, delta_ns, mode, base))
1323 hrtimer_reprogram(timer, true);
1324
1325 unlock_hrtimer_base(timer, &flags);
1326}
1327EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
1328
1329/**
1330 * hrtimer_try_to_cancel - try to deactivate a timer
1331 * @timer: hrtimer to stop
1332 *
1333 * Returns:
1334 *
1335 * * 0 when the timer was not active
1336 * * 1 when the timer was active
1337 * * -1 when the timer is currently executing the callback function and
1338 * cannot be stopped
1339 */
1340int hrtimer_try_to_cancel(struct hrtimer *timer)
1341{
1342 struct hrtimer_clock_base *base;
1343 unsigned long flags;
1344 int ret = -1;
1345
1346 /*
1347 * Check lockless first. If the timer is not active (neither
1348 * enqueued nor running the callback, nothing to do here. The
1349 * base lock does not serialize against a concurrent enqueue,
1350 * so we can avoid taking it.
1351 */
1352 if (!hrtimer_active(timer))
1353 return 0;
1354
1355 base = lock_hrtimer_base(timer, &flags);
1356
1357 if (!hrtimer_callback_running(timer))
1358 ret = remove_hrtimer(timer, base, false, false);
1359
1360 unlock_hrtimer_base(timer, &flags);
1361
1362 return ret;
1363
1364}
1365EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
1366
1367#ifdef CONFIG_PREEMPT_RT
1368static void hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base)
1369{
1370 spin_lock_init(&base->softirq_expiry_lock);
1371}
1372
1373static void hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base)
1374 __acquires(&base->softirq_expiry_lock)
1375{
1376 spin_lock(&base->softirq_expiry_lock);
1377}
1378
1379static void hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base)
1380 __releases(&base->softirq_expiry_lock)
1381{
1382 spin_unlock(&base->softirq_expiry_lock);
1383}
1384
1385/*
1386 * The counterpart to hrtimer_cancel_wait_running().
1387 *
1388 * If there is a waiter for cpu_base->expiry_lock, then it was waiting for
1389 * the timer callback to finish. Drop expiry_lock and reacquire it. That
1390 * allows the waiter to acquire the lock and make progress.
1391 */
1392static void hrtimer_sync_wait_running(struct hrtimer_cpu_base *cpu_base,
1393 unsigned long flags)
1394{
1395 if (atomic_read(&cpu_base->timer_waiters)) {
1396 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1397 spin_unlock(&cpu_base->softirq_expiry_lock);
1398 spin_lock(&cpu_base->softirq_expiry_lock);
1399 raw_spin_lock_irq(&cpu_base->lock);
1400 }
1401}
1402
1403#ifdef CONFIG_SMP
1404static __always_inline bool is_migration_base(struct hrtimer_clock_base *base)
1405{
1406 return base == &migration_base;
1407}
1408#else
1409static __always_inline bool is_migration_base(struct hrtimer_clock_base *base)
1410{
1411 return false;
1412}
1413#endif
1414
1415/*
1416 * This function is called on PREEMPT_RT kernels when the fast path
1417 * deletion of a timer failed because the timer callback function was
1418 * running.
1419 *
1420 * This prevents priority inversion: if the soft irq thread is preempted
1421 * in the middle of a timer callback, then calling hrtimer_cancel() can
1422 * lead to two issues:
1423 *
1424 * - If the caller is on a remote CPU then it has to spin wait for the timer
1425 * handler to complete. This can result in unbound priority inversion.
1426 *
1427 * - If the caller originates from the task which preempted the timer
1428 * handler on the same CPU, then spin waiting for the timer handler to
1429 * complete is never going to end.
1430 */
1431void hrtimer_cancel_wait_running(const struct hrtimer *timer)
1432{
1433 /* Lockless read. Prevent the compiler from reloading it below */
1434 struct hrtimer_clock_base *base = READ_ONCE(timer->base);
1435
1436 /*
1437 * Just relax if the timer expires in hard interrupt context or if
1438 * it is currently on the migration base.
1439 */
1440 if (!timer->is_soft || is_migration_base(base)) {
1441 cpu_relax();
1442 return;
1443 }
1444
1445 /*
1446 * Mark the base as contended and grab the expiry lock, which is
1447 * held by the softirq across the timer callback. Drop the lock
1448 * immediately so the softirq can expire the next timer. In theory
1449 * the timer could already be running again, but that's more than
1450 * unlikely and just causes another wait loop.
1451 */
1452 atomic_inc(&base->cpu_base->timer_waiters);
1453 spin_lock_bh(&base->cpu_base->softirq_expiry_lock);
1454 atomic_dec(&base->cpu_base->timer_waiters);
1455 spin_unlock_bh(&base->cpu_base->softirq_expiry_lock);
1456}
1457#else
1458static inline void
1459hrtimer_cpu_base_init_expiry_lock(struct hrtimer_cpu_base *base) { }
1460static inline void
1461hrtimer_cpu_base_lock_expiry(struct hrtimer_cpu_base *base) { }
1462static inline void
1463hrtimer_cpu_base_unlock_expiry(struct hrtimer_cpu_base *base) { }
1464static inline void hrtimer_sync_wait_running(struct hrtimer_cpu_base *base,
1465 unsigned long flags) { }
1466#endif
1467
1468/**
1469 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
1470 * @timer: the timer to be cancelled
1471 *
1472 * Returns:
1473 * 0 when the timer was not active
1474 * 1 when the timer was active
1475 */
1476int hrtimer_cancel(struct hrtimer *timer)
1477{
1478 int ret;
1479
1480 do {
1481 ret = hrtimer_try_to_cancel(timer);
1482
1483 if (ret < 0)
1484 hrtimer_cancel_wait_running(timer);
1485 } while (ret < 0);
1486 return ret;
1487}
1488EXPORT_SYMBOL_GPL(hrtimer_cancel);
1489
1490/**
1491 * __hrtimer_get_remaining - get remaining time for the timer
1492 * @timer: the timer to read
1493 * @adjust: adjust relative timers when CONFIG_TIME_LOW_RES=y
1494 */
1495ktime_t __hrtimer_get_remaining(const struct hrtimer *timer, bool adjust)
1496{
1497 unsigned long flags;
1498 ktime_t rem;
1499
1500 lock_hrtimer_base(timer, &flags);
1501 if (IS_ENABLED(CONFIG_TIME_LOW_RES) && adjust)
1502 rem = hrtimer_expires_remaining_adjusted(timer);
1503 else
1504 rem = hrtimer_expires_remaining(timer);
1505 unlock_hrtimer_base(timer, &flags);
1506
1507 return rem;
1508}
1509EXPORT_SYMBOL_GPL(__hrtimer_get_remaining);
1510
1511#ifdef CONFIG_NO_HZ_COMMON
1512/**
1513 * hrtimer_get_next_event - get the time until next expiry event
1514 *
1515 * Returns the next expiry time or KTIME_MAX if no timer is pending.
1516 */
1517u64 hrtimer_get_next_event(void)
1518{
1519 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
1520 u64 expires = KTIME_MAX;
1521 unsigned long flags;
1522
1523 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1524
1525 if (!hrtimer_hres_active(cpu_base))
1526 expires = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
1527
1528 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1529
1530 return expires;
1531}
1532
1533/**
1534 * hrtimer_next_event_without - time until next expiry event w/o one timer
1535 * @exclude: timer to exclude
1536 *
1537 * Returns the next expiry time over all timers except for the @exclude one or
1538 * KTIME_MAX if none of them is pending.
1539 */
1540u64 hrtimer_next_event_without(const struct hrtimer *exclude)
1541{
1542 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
1543 u64 expires = KTIME_MAX;
1544 unsigned long flags;
1545
1546 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1547
1548 if (hrtimer_hres_active(cpu_base)) {
1549 unsigned int active;
1550
1551 if (!cpu_base->softirq_activated) {
1552 active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
1553 expires = __hrtimer_next_event_base(cpu_base, exclude,
1554 active, KTIME_MAX);
1555 }
1556 active = cpu_base->active_bases & HRTIMER_ACTIVE_HARD;
1557 expires = __hrtimer_next_event_base(cpu_base, exclude, active,
1558 expires);
1559 }
1560
1561 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1562
1563 return expires;
1564}
1565#endif
1566
1567static inline int hrtimer_clockid_to_base(clockid_t clock_id)
1568{
1569 switch (clock_id) {
1570 case CLOCK_MONOTONIC:
1571 return HRTIMER_BASE_MONOTONIC;
1572 case CLOCK_REALTIME:
1573 return HRTIMER_BASE_REALTIME;
1574 case CLOCK_BOOTTIME:
1575 return HRTIMER_BASE_BOOTTIME;
1576 case CLOCK_TAI:
1577 return HRTIMER_BASE_TAI;
1578 default:
1579 WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
1580 return HRTIMER_BASE_MONOTONIC;
1581 }
1582}
1583
1584static ktime_t __hrtimer_cb_get_time(clockid_t clock_id)
1585{
1586 switch (clock_id) {
1587 case CLOCK_MONOTONIC:
1588 return ktime_get();
1589 case CLOCK_REALTIME:
1590 return ktime_get_real();
1591 case CLOCK_BOOTTIME:
1592 return ktime_get_boottime();
1593 case CLOCK_TAI:
1594 return ktime_get_clocktai();
1595 default:
1596 WARN(1, "Invalid clockid %d. Using MONOTONIC\n", clock_id);
1597 return ktime_get();
1598 }
1599}
1600
1601ktime_t hrtimer_cb_get_time(const struct hrtimer *timer)
1602{
1603 return __hrtimer_cb_get_time(timer->base->clockid);
1604}
1605EXPORT_SYMBOL_GPL(hrtimer_cb_get_time);
1606
1607static void __hrtimer_setup(struct hrtimer *timer,
1608 enum hrtimer_restart (*function)(struct hrtimer *),
1609 clockid_t clock_id, enum hrtimer_mode mode)
1610{
1611 bool softtimer = !!(mode & HRTIMER_MODE_SOFT);
1612 struct hrtimer_cpu_base *cpu_base;
1613 int base;
1614
1615 /*
1616 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
1617 * marked for hard interrupt expiry mode are moved into soft
1618 * interrupt context for latency reasons and because the callbacks
1619 * can invoke functions which might sleep on RT, e.g. spin_lock().
1620 */
1621 if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(mode & HRTIMER_MODE_HARD))
1622 softtimer = true;
1623
1624 memset(timer, 0, sizeof(struct hrtimer));
1625
1626 cpu_base = raw_cpu_ptr(&hrtimer_bases);
1627
1628 /*
1629 * POSIX magic: Relative CLOCK_REALTIME timers are not affected by
1630 * clock modifications, so they needs to become CLOCK_MONOTONIC to
1631 * ensure POSIX compliance.
1632 */
1633 if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
1634 clock_id = CLOCK_MONOTONIC;
1635
1636 base = softtimer ? HRTIMER_MAX_CLOCK_BASES / 2 : 0;
1637 base += hrtimer_clockid_to_base(clock_id);
1638 timer->is_soft = softtimer;
1639 timer->is_hard = !!(mode & HRTIMER_MODE_HARD);
1640 timer->base = &cpu_base->clock_base[base];
1641 timerqueue_init(&timer->node);
1642
1643 if (WARN_ON_ONCE(!function))
1644 ACCESS_PRIVATE(timer, function) = hrtimer_dummy_timeout;
1645 else
1646 ACCESS_PRIVATE(timer, function) = function;
1647}
1648
1649/**
1650 * hrtimer_setup - initialize a timer to the given clock
1651 * @timer: the timer to be initialized
1652 * @function: the callback function
1653 * @clock_id: the clock to be used
1654 * @mode: The modes which are relevant for initialization:
1655 * HRTIMER_MODE_ABS, HRTIMER_MODE_REL, HRTIMER_MODE_ABS_SOFT,
1656 * HRTIMER_MODE_REL_SOFT
1657 *
1658 * The PINNED variants of the above can be handed in,
1659 * but the PINNED bit is ignored as pinning happens
1660 * when the hrtimer is started
1661 */
1662void hrtimer_setup(struct hrtimer *timer, enum hrtimer_restart (*function)(struct hrtimer *),
1663 clockid_t clock_id, enum hrtimer_mode mode)
1664{
1665 debug_setup(timer, clock_id, mode);
1666 __hrtimer_setup(timer, function, clock_id, mode);
1667}
1668EXPORT_SYMBOL_GPL(hrtimer_setup);
1669
1670/**
1671 * hrtimer_setup_on_stack - initialize a timer on stack memory
1672 * @timer: The timer to be initialized
1673 * @function: the callback function
1674 * @clock_id: The clock to be used
1675 * @mode: The timer mode
1676 *
1677 * Similar to hrtimer_setup(), except that this one must be used if struct hrtimer is in stack
1678 * memory.
1679 */
1680void hrtimer_setup_on_stack(struct hrtimer *timer,
1681 enum hrtimer_restart (*function)(struct hrtimer *),
1682 clockid_t clock_id, enum hrtimer_mode mode)
1683{
1684 debug_setup_on_stack(timer, clock_id, mode);
1685 __hrtimer_setup(timer, function, clock_id, mode);
1686}
1687EXPORT_SYMBOL_GPL(hrtimer_setup_on_stack);
1688
1689/*
1690 * A timer is active, when it is enqueued into the rbtree or the
1691 * callback function is running or it's in the state of being migrated
1692 * to another cpu.
1693 *
1694 * It is important for this function to not return a false negative.
1695 */
1696bool hrtimer_active(const struct hrtimer *timer)
1697{
1698 struct hrtimer_clock_base *base;
1699 unsigned int seq;
1700
1701 do {
1702 base = READ_ONCE(timer->base);
1703 seq = raw_read_seqcount_begin(&base->seq);
1704
1705 if (timer->state != HRTIMER_STATE_INACTIVE ||
1706 base->running == timer)
1707 return true;
1708
1709 } while (read_seqcount_retry(&base->seq, seq) ||
1710 base != READ_ONCE(timer->base));
1711
1712 return false;
1713}
1714EXPORT_SYMBOL_GPL(hrtimer_active);
1715
1716/*
1717 * The write_seqcount_barrier()s in __run_hrtimer() split the thing into 3
1718 * distinct sections:
1719 *
1720 * - queued: the timer is queued
1721 * - callback: the timer is being ran
1722 * - post: the timer is inactive or (re)queued
1723 *
1724 * On the read side we ensure we observe timer->state and cpu_base->running
1725 * from the same section, if anything changed while we looked at it, we retry.
1726 * This includes timer->base changing because sequence numbers alone are
1727 * insufficient for that.
1728 *
1729 * The sequence numbers are required because otherwise we could still observe
1730 * a false negative if the read side got smeared over multiple consecutive
1731 * __run_hrtimer() invocations.
1732 */
1733
1734static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
1735 struct hrtimer_clock_base *base,
1736 struct hrtimer *timer, ktime_t *now,
1737 unsigned long flags) __must_hold(&cpu_base->lock)
1738{
1739 enum hrtimer_restart (*fn)(struct hrtimer *);
1740 bool expires_in_hardirq;
1741 int restart;
1742
1743 lockdep_assert_held(&cpu_base->lock);
1744
1745 debug_deactivate(timer);
1746 base->running = timer;
1747
1748 /*
1749 * Separate the ->running assignment from the ->state assignment.
1750 *
1751 * As with a regular write barrier, this ensures the read side in
1752 * hrtimer_active() cannot observe base->running == NULL &&
1753 * timer->state == INACTIVE.
1754 */
1755 raw_write_seqcount_barrier(&base->seq);
1756
1757 __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
1758 fn = ACCESS_PRIVATE(timer, function);
1759
1760 /*
1761 * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
1762 * timer is restarted with a period then it becomes an absolute
1763 * timer. If its not restarted it does not matter.
1764 */
1765 if (IS_ENABLED(CONFIG_TIME_LOW_RES))
1766 timer->is_rel = false;
1767
1768 /*
1769 * The timer is marked as running in the CPU base, so it is
1770 * protected against migration to a different CPU even if the lock
1771 * is dropped.
1772 */
1773 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1774 trace_hrtimer_expire_entry(timer, now);
1775 expires_in_hardirq = lockdep_hrtimer_enter(timer);
1776
1777 restart = fn(timer);
1778
1779 lockdep_hrtimer_exit(expires_in_hardirq);
1780 trace_hrtimer_expire_exit(timer);
1781 raw_spin_lock_irq(&cpu_base->lock);
1782
1783 /*
1784 * Note: We clear the running state after enqueue_hrtimer and
1785 * we do not reprogram the event hardware. Happens either in
1786 * hrtimer_start_range_ns() or in hrtimer_interrupt()
1787 *
1788 * Note: Because we dropped the cpu_base->lock above,
1789 * hrtimer_start_range_ns() can have popped in and enqueued the timer
1790 * for us already.
1791 */
1792 if (restart != HRTIMER_NORESTART &&
1793 !(timer->state & HRTIMER_STATE_ENQUEUED))
1794 enqueue_hrtimer(timer, base, HRTIMER_MODE_ABS);
1795
1796 /*
1797 * Separate the ->running assignment from the ->state assignment.
1798 *
1799 * As with a regular write barrier, this ensures the read side in
1800 * hrtimer_active() cannot observe base->running.timer == NULL &&
1801 * timer->state == INACTIVE.
1802 */
1803 raw_write_seqcount_barrier(&base->seq);
1804
1805 WARN_ON_ONCE(base->running != timer);
1806 base->running = NULL;
1807}
1808
1809static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
1810 unsigned long flags, unsigned int active_mask)
1811{
1812 struct hrtimer_clock_base *base;
1813 unsigned int active = cpu_base->active_bases & active_mask;
1814
1815 for_each_active_base(base, cpu_base, active) {
1816 struct timerqueue_node *node;
1817 ktime_t basenow;
1818
1819 basenow = ktime_add(now, base->offset);
1820
1821 while ((node = timerqueue_getnext(&base->active))) {
1822 struct hrtimer *timer;
1823
1824 timer = container_of(node, struct hrtimer, node);
1825
1826 /*
1827 * The immediate goal for using the softexpires is
1828 * minimizing wakeups, not running timers at the
1829 * earliest interrupt after their soft expiration.
1830 * This allows us to avoid using a Priority Search
1831 * Tree, which can answer a stabbing query for
1832 * overlapping intervals and instead use the simple
1833 * BST we already have.
1834 * We don't add extra wakeups by delaying timers that
1835 * are right-of a not yet expired timer, because that
1836 * timer will have to trigger a wakeup anyway.
1837 */
1838 if (basenow < hrtimer_get_softexpires_tv64(timer))
1839 break;
1840
1841 __run_hrtimer(cpu_base, base, timer, &basenow, flags);
1842 if (active_mask == HRTIMER_ACTIVE_SOFT)
1843 hrtimer_sync_wait_running(cpu_base, flags);
1844 }
1845 }
1846}
1847
1848static __latent_entropy void hrtimer_run_softirq(void)
1849{
1850 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
1851 unsigned long flags;
1852 ktime_t now;
1853
1854 hrtimer_cpu_base_lock_expiry(cpu_base);
1855 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1856
1857 now = hrtimer_update_base(cpu_base);
1858 __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_SOFT);
1859
1860 cpu_base->softirq_activated = 0;
1861 hrtimer_update_softirq_timer(cpu_base, true);
1862
1863 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1864 hrtimer_cpu_base_unlock_expiry(cpu_base);
1865}
1866
1867#ifdef CONFIG_HIGH_RES_TIMERS
1868
1869/*
1870 * High resolution timer interrupt
1871 * Called with interrupts disabled
1872 */
1873void hrtimer_interrupt(struct clock_event_device *dev)
1874{
1875 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
1876 ktime_t expires_next, now, entry_time, delta;
1877 unsigned long flags;
1878 int retries = 0;
1879
1880 BUG_ON(!cpu_base->hres_active);
1881 cpu_base->nr_events++;
1882 dev->next_event = KTIME_MAX;
1883
1884 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1885 entry_time = now = hrtimer_update_base(cpu_base);
1886retry:
1887 cpu_base->in_hrtirq = 1;
1888 /*
1889 * We set expires_next to KTIME_MAX here with cpu_base->lock
1890 * held to prevent that a timer is enqueued in our queue via
1891 * the migration code. This does not affect enqueueing of
1892 * timers which run their callback and need to be requeued on
1893 * this CPU.
1894 */
1895 cpu_base->expires_next = KTIME_MAX;
1896
1897 if (!ktime_before(now, cpu_base->softirq_expires_next)) {
1898 cpu_base->softirq_expires_next = KTIME_MAX;
1899 cpu_base->softirq_activated = 1;
1900 raise_timer_softirq(HRTIMER_SOFTIRQ);
1901 }
1902
1903 __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
1904
1905 /* Reevaluate the clock bases for the [soft] next expiry */
1906 expires_next = hrtimer_update_next_event(cpu_base);
1907 /*
1908 * Store the new expiry value so the migration code can verify
1909 * against it.
1910 */
1911 cpu_base->expires_next = expires_next;
1912 cpu_base->in_hrtirq = 0;
1913 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1914
1915 /* Reprogramming necessary ? */
1916 if (!tick_program_event(expires_next, 0)) {
1917 cpu_base->hang_detected = 0;
1918 return;
1919 }
1920
1921 /*
1922 * The next timer was already expired due to:
1923 * - tracing
1924 * - long lasting callbacks
1925 * - being scheduled away when running in a VM
1926 *
1927 * We need to prevent that we loop forever in the hrtimer
1928 * interrupt routine. We give it 3 attempts to avoid
1929 * overreacting on some spurious event.
1930 *
1931 * Acquire base lock for updating the offsets and retrieving
1932 * the current time.
1933 */
1934 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1935 now = hrtimer_update_base(cpu_base);
1936 cpu_base->nr_retries++;
1937 if (++retries < 3)
1938 goto retry;
1939 /*
1940 * Give the system a chance to do something else than looping
1941 * here. We stored the entry time, so we know exactly how long
1942 * we spent here. We schedule the next event this amount of
1943 * time away.
1944 */
1945 cpu_base->nr_hangs++;
1946 cpu_base->hang_detected = 1;
1947 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
1948
1949 delta = ktime_sub(now, entry_time);
1950 if ((unsigned int)delta > cpu_base->max_hang_time)
1951 cpu_base->max_hang_time = (unsigned int) delta;
1952 /*
1953 * Limit it to a sensible value as we enforce a longer
1954 * delay. Give the CPU at least 100ms to catch up.
1955 */
1956 if (delta > 100 * NSEC_PER_MSEC)
1957 expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
1958 else
1959 expires_next = ktime_add(now, delta);
1960 tick_program_event(expires_next, 1);
1961 pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
1962}
1963#endif /* !CONFIG_HIGH_RES_TIMERS */
1964
1965/*
1966 * Called from run_local_timers in hardirq context every jiffy
1967 */
1968void hrtimer_run_queues(void)
1969{
1970 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
1971 unsigned long flags;
1972 ktime_t now;
1973
1974 if (hrtimer_hres_active(cpu_base))
1975 return;
1976
1977 /*
1978 * This _is_ ugly: We have to check periodically, whether we
1979 * can switch to highres and / or nohz mode. The clocksource
1980 * switch happens with xtime_lock held. Notification from
1981 * there only sets the check bit in the tick_oneshot code,
1982 * otherwise we might deadlock vs. xtime_lock.
1983 */
1984 if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) {
1985 hrtimer_switch_to_hres();
1986 return;
1987 }
1988
1989 raw_spin_lock_irqsave(&cpu_base->lock, flags);
1990 now = hrtimer_update_base(cpu_base);
1991
1992 if (!ktime_before(now, cpu_base->softirq_expires_next)) {
1993 cpu_base->softirq_expires_next = KTIME_MAX;
1994 cpu_base->softirq_activated = 1;
1995 raise_timer_softirq(HRTIMER_SOFTIRQ);
1996 }
1997
1998 __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
1999 raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
2000}
2001
2002/*
2003 * Sleep related functions:
2004 */
2005static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
2006{
2007 struct hrtimer_sleeper *t =
2008 container_of(timer, struct hrtimer_sleeper, timer);
2009 struct task_struct *task = t->task;
2010
2011 t->task = NULL;
2012 if (task)
2013 wake_up_process(task);
2014
2015 return HRTIMER_NORESTART;
2016}
2017
2018/**
2019 * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
2020 * @sl: sleeper to be started
2021 * @mode: timer mode abs/rel
2022 *
2023 * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
2024 * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
2025 */
2026void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
2027 enum hrtimer_mode mode)
2028{
2029 /*
2030 * Make the enqueue delivery mode check work on RT. If the sleeper
2031 * was initialized for hard interrupt delivery, force the mode bit.
2032 * This is a special case for hrtimer_sleepers because
2033 * __hrtimer_setup_sleeper() determines the delivery mode on RT so the
2034 * fiddling with this decision is avoided at the call sites.
2035 */
2036 if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard)
2037 mode |= HRTIMER_MODE_HARD;
2038
2039 hrtimer_start_expires(&sl->timer, mode);
2040}
2041EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
2042
2043static void __hrtimer_setup_sleeper(struct hrtimer_sleeper *sl,
2044 clockid_t clock_id, enum hrtimer_mode mode)
2045{
2046 /*
2047 * On PREEMPT_RT enabled kernels hrtimers which are not explicitly
2048 * marked for hard interrupt expiry mode are moved into soft
2049 * interrupt context either for latency reasons or because the
2050 * hrtimer callback takes regular spinlocks or invokes other
2051 * functions which are not suitable for hard interrupt context on
2052 * PREEMPT_RT.
2053 *
2054 * The hrtimer_sleeper callback is RT compatible in hard interrupt
2055 * context, but there is a latency concern: Untrusted userspace can
2056 * spawn many threads which arm timers for the same expiry time on
2057 * the same CPU. That causes a latency spike due to the wakeup of
2058 * a gazillion threads.
2059 *
2060 * OTOH, privileged real-time user space applications rely on the
2061 * low latency of hard interrupt wakeups. If the current task is in
2062 * a real-time scheduling class, mark the mode for hard interrupt
2063 * expiry.
2064 */
2065 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
2066 if (rt_or_dl_task_policy(current) && !(mode & HRTIMER_MODE_SOFT))
2067 mode |= HRTIMER_MODE_HARD;
2068 }
2069
2070 __hrtimer_setup(&sl->timer, hrtimer_wakeup, clock_id, mode);
2071 sl->task = current;
2072}
2073
2074/**
2075 * hrtimer_setup_sleeper_on_stack - initialize a sleeper in stack memory
2076 * @sl: sleeper to be initialized
2077 * @clock_id: the clock to be used
2078 * @mode: timer mode abs/rel
2079 */
2080void hrtimer_setup_sleeper_on_stack(struct hrtimer_sleeper *sl,
2081 clockid_t clock_id, enum hrtimer_mode mode)
2082{
2083 debug_setup_on_stack(&sl->timer, clock_id, mode);
2084 __hrtimer_setup_sleeper(sl, clock_id, mode);
2085}
2086EXPORT_SYMBOL_GPL(hrtimer_setup_sleeper_on_stack);
2087
2088int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
2089{
2090 switch(restart->nanosleep.type) {
2091#ifdef CONFIG_COMPAT_32BIT_TIME
2092 case TT_COMPAT:
2093 if (put_old_timespec32(ts, restart->nanosleep.compat_rmtp))
2094 return -EFAULT;
2095 break;
2096#endif
2097 case TT_NATIVE:
2098 if (put_timespec64(ts, restart->nanosleep.rmtp))
2099 return -EFAULT;
2100 break;
2101 default:
2102 BUG();
2103 }
2104 return -ERESTART_RESTARTBLOCK;
2105}
2106
2107static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
2108{
2109 struct restart_block *restart;
2110
2111 do {
2112 set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
2113 hrtimer_sleeper_start_expires(t, mode);
2114
2115 if (likely(t->task))
2116 schedule();
2117
2118 hrtimer_cancel(&t->timer);
2119 mode = HRTIMER_MODE_ABS;
2120
2121 } while (t->task && !signal_pending(current));
2122
2123 __set_current_state(TASK_RUNNING);
2124
2125 if (!t->task)
2126 return 0;
2127
2128 restart = &current->restart_block;
2129 if (restart->nanosleep.type != TT_NONE) {
2130 ktime_t rem = hrtimer_expires_remaining(&t->timer);
2131 struct timespec64 rmt;
2132
2133 if (rem <= 0)
2134 return 0;
2135 rmt = ktime_to_timespec64(rem);
2136
2137 return nanosleep_copyout(restart, &rmt);
2138 }
2139 return -ERESTART_RESTARTBLOCK;
2140}
2141
2142static long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
2143{
2144 struct hrtimer_sleeper t;
2145 int ret;
2146
2147 hrtimer_setup_sleeper_on_stack(&t, restart->nanosleep.clockid, HRTIMER_MODE_ABS);
2148 hrtimer_set_expires(&t.timer, restart->nanosleep.expires);
2149 ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
2150 destroy_hrtimer_on_stack(&t.timer);
2151 return ret;
2152}
2153
2154long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode,
2155 const clockid_t clockid)
2156{
2157 struct restart_block *restart;
2158 struct hrtimer_sleeper t;
2159 int ret = 0;
2160
2161 hrtimer_setup_sleeper_on_stack(&t, clockid, mode);
2162 hrtimer_set_expires_range_ns(&t.timer, rqtp, current->timer_slack_ns);
2163 ret = do_nanosleep(&t, mode);
2164 if (ret != -ERESTART_RESTARTBLOCK)
2165 goto out;
2166
2167 /* Absolute timers do not update the rmtp value and restart: */
2168 if (mode == HRTIMER_MODE_ABS) {
2169 ret = -ERESTARTNOHAND;
2170 goto out;
2171 }
2172
2173 restart = &current->restart_block;
2174 restart->nanosleep.clockid = t.timer.base->clockid;
2175 restart->nanosleep.expires = hrtimer_get_expires(&t.timer);
2176 set_restart_fn(restart, hrtimer_nanosleep_restart);
2177out:
2178 destroy_hrtimer_on_stack(&t.timer);
2179 return ret;
2180}
2181
2182#ifdef CONFIG_64BIT
2183
2184SYSCALL_DEFINE2(nanosleep, struct __kernel_timespec __user *, rqtp,
2185 struct __kernel_timespec __user *, rmtp)
2186{
2187 struct timespec64 tu;
2188
2189 if (get_timespec64(&tu, rqtp))
2190 return -EFAULT;
2191
2192 if (!timespec64_valid(&tu))
2193 return -EINVAL;
2194
2195 current->restart_block.fn = do_no_restart_syscall;
2196 current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
2197 current->restart_block.nanosleep.rmtp = rmtp;
2198 return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
2199 CLOCK_MONOTONIC);
2200}
2201
2202#endif
2203
2204#ifdef CONFIG_COMPAT_32BIT_TIME
2205
2206SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp,
2207 struct old_timespec32 __user *, rmtp)
2208{
2209 struct timespec64 tu;
2210
2211 if (get_old_timespec32(&tu, rqtp))
2212 return -EFAULT;
2213
2214 if (!timespec64_valid(&tu))
2215 return -EINVAL;
2216
2217 current->restart_block.fn = do_no_restart_syscall;
2218 current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
2219 current->restart_block.nanosleep.compat_rmtp = rmtp;
2220 return hrtimer_nanosleep(timespec64_to_ktime(tu), HRTIMER_MODE_REL,
2221 CLOCK_MONOTONIC);
2222}
2223#endif
2224
2225/*
2226 * Functions related to boot-time initialization:
2227 */
2228int hrtimers_prepare_cpu(unsigned int cpu)
2229{
2230 struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
2231 int i;
2232
2233 for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
2234 struct hrtimer_clock_base *clock_b = &cpu_base->clock_base[i];
2235
2236 clock_b->cpu_base = cpu_base;
2237 seqcount_raw_spinlock_init(&clock_b->seq, &cpu_base->lock);
2238 timerqueue_init_head(&clock_b->active);
2239 }
2240
2241 cpu_base->cpu = cpu;
2242 hrtimer_cpu_base_init_expiry_lock(cpu_base);
2243 return 0;
2244}
2245
2246int hrtimers_cpu_starting(unsigned int cpu)
2247{
2248 struct hrtimer_cpu_base *cpu_base = this_cpu_ptr(&hrtimer_bases);
2249
2250 /* Clear out any left over state from a CPU down operation */
2251 cpu_base->active_bases = 0;
2252 cpu_base->hres_active = 0;
2253 cpu_base->hang_detected = 0;
2254 cpu_base->next_timer = NULL;
2255 cpu_base->softirq_next_timer = NULL;
2256 cpu_base->expires_next = KTIME_MAX;
2257 cpu_base->softirq_expires_next = KTIME_MAX;
2258 cpu_base->online = 1;
2259 return 0;
2260}
2261
2262#ifdef CONFIG_HOTPLUG_CPU
2263
2264static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
2265 struct hrtimer_clock_base *new_base)
2266{
2267 struct hrtimer *timer;
2268 struct timerqueue_node *node;
2269
2270 while ((node = timerqueue_getnext(&old_base->active))) {
2271 timer = container_of(node, struct hrtimer, node);
2272 BUG_ON(hrtimer_callback_running(timer));
2273 debug_deactivate(timer);
2274
2275 /*
2276 * Mark it as ENQUEUED not INACTIVE otherwise the
2277 * timer could be seen as !active and just vanish away
2278 * under us on another CPU
2279 */
2280 __remove_hrtimer(timer, old_base, HRTIMER_STATE_ENQUEUED, 0);
2281 timer->base = new_base;
2282 /*
2283 * Enqueue the timers on the new cpu. This does not
2284 * reprogram the event device in case the timer
2285 * expires before the earliest on this CPU, but we run
2286 * hrtimer_interrupt after we migrated everything to
2287 * sort out already expired timers and reprogram the
2288 * event device.
2289 */
2290 enqueue_hrtimer(timer, new_base, HRTIMER_MODE_ABS);
2291 }
2292}
2293
2294int hrtimers_cpu_dying(unsigned int dying_cpu)
2295{
2296 int i, ncpu = cpumask_any_and(cpu_active_mask, housekeeping_cpumask(HK_TYPE_TIMER));
2297 struct hrtimer_cpu_base *old_base, *new_base;
2298
2299 old_base = this_cpu_ptr(&hrtimer_bases);
2300 new_base = &per_cpu(hrtimer_bases, ncpu);
2301
2302 /*
2303 * The caller is globally serialized and nobody else
2304 * takes two locks at once, deadlock is not possible.
2305 */
2306 raw_spin_lock(&old_base->lock);
2307 raw_spin_lock_nested(&new_base->lock, SINGLE_DEPTH_NESTING);
2308
2309 for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
2310 migrate_hrtimer_list(&old_base->clock_base[i],
2311 &new_base->clock_base[i]);
2312 }
2313
2314 /* Tell the other CPU to retrigger the next event */
2315 smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);
2316
2317 raw_spin_unlock(&new_base->lock);
2318 old_base->online = 0;
2319 raw_spin_unlock(&old_base->lock);
2320
2321 return 0;
2322}
2323
2324#endif /* CONFIG_HOTPLUG_CPU */
2325
2326void __init hrtimers_init(void)
2327{
2328 hrtimers_prepare_cpu(smp_processor_id());
2329 hrtimers_cpu_starting(smp_processor_id());
2330 open_softirq(HRTIMER_SOFTIRQ, hrtimer_run_softirq);
2331}