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14#include <linux/cpu.h>
15#include <linux/err.h>
16#include <linux/hrtimer.h>
17#include <linux/interrupt.h>
18#include <linux/kernel_stat.h>
19#include <linux/percpu.h>
20#include <linux/profile.h>
21#include <linux/sched.h>
22#include <linux/module.h>
23#include <linux/irq_work.h>
24#include <linux/posix-timers.h>
25#include <linux/perf_event.h>
26
27#include <asm/irq_regs.h>
28
29#include "tick-internal.h"
30
31#include <trace/events/timer.h>
32
33
34
35
36DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
37
38
39
40
41static ktime_t last_jiffies_update;
42
43struct tick_sched *tick_get_tick_sched(int cpu)
44{
45 return &per_cpu(tick_cpu_sched, cpu);
46}
47
48
49
50
51static void tick_do_update_jiffies64(ktime_t now)
52{
53 unsigned long ticks = 0;
54 ktime_t delta;
55
56
57
58
59 delta = ktime_sub(now, last_jiffies_update);
60 if (delta.tv64 < tick_period.tv64)
61 return;
62
63
64 write_seqlock(&jiffies_lock);
65
66 delta = ktime_sub(now, last_jiffies_update);
67 if (delta.tv64 >= tick_period.tv64) {
68
69 delta = ktime_sub(delta, tick_period);
70 last_jiffies_update = ktime_add(last_jiffies_update,
71 tick_period);
72
73
74 if (unlikely(delta.tv64 >= tick_period.tv64)) {
75 s64 incr = ktime_to_ns(tick_period);
76
77 ticks = ktime_divns(delta, incr);
78
79 last_jiffies_update = ktime_add_ns(last_jiffies_update,
80 incr * ticks);
81 }
82 do_timer(++ticks);
83
84
85 tick_next_period = ktime_add(last_jiffies_update, tick_period);
86 }
87 write_sequnlock(&jiffies_lock);
88}
89
90
91
92
93static ktime_t tick_init_jiffy_update(void)
94{
95 ktime_t period;
96
97 write_seqlock(&jiffies_lock);
98
99 if (last_jiffies_update.tv64 == 0)
100 last_jiffies_update = tick_next_period;
101 period = last_jiffies_update;
102 write_sequnlock(&jiffies_lock);
103 return period;
104}
105
106
107static void tick_sched_do_timer(ktime_t now)
108{
109 int cpu = smp_processor_id();
110
111#ifdef CONFIG_NO_HZ_COMMON
112
113
114
115
116
117
118
119 if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)
120 && !tick_nohz_full_cpu(cpu))
121 tick_do_timer_cpu = cpu;
122#endif
123
124
125 if (tick_do_timer_cpu == cpu)
126 tick_do_update_jiffies64(now);
127}
128
129static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
130{
131#ifdef CONFIG_NO_HZ_COMMON
132
133
134
135
136
137
138
139
140 if (ts->tick_stopped) {
141 touch_softlockup_watchdog();
142 if (is_idle_task(current))
143 ts->idle_jiffies++;
144 }
145#endif
146 update_process_times(user_mode(regs));
147 profile_tick(CPU_PROFILING);
148}
149
150#ifdef CONFIG_NO_HZ_FULL
151static cpumask_var_t nohz_full_mask;
152bool have_nohz_full_mask;
153
154static bool can_stop_full_tick(void)
155{
156 WARN_ON_ONCE(!irqs_disabled());
157
158 if (!sched_can_stop_tick()) {
159 trace_tick_stop(0, "more than 1 task in runqueue\n");
160 return false;
161 }
162
163 if (!posix_cpu_timers_can_stop_tick(current)) {
164 trace_tick_stop(0, "posix timers running\n");
165 return false;
166 }
167
168 if (!perf_event_can_stop_tick()) {
169 trace_tick_stop(0, "perf events running\n");
170 return false;
171 }
172
173
174#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
175
176
177
178
179 if (!sched_clock_stable) {
180 trace_tick_stop(0, "unstable sched clock\n");
181
182
183
184
185 WARN_ONCE(have_nohz_full_mask,
186 "NO_HZ FULL will not work with unstable sched clock");
187 return false;
188 }
189#endif
190
191 return true;
192}
193
194static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
195
196
197
198
199
200void tick_nohz_full_check(void)
201{
202 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
203
204 if (tick_nohz_full_cpu(smp_processor_id())) {
205 if (ts->tick_stopped && !is_idle_task(current)) {
206 if (!can_stop_full_tick())
207 tick_nohz_restart_sched_tick(ts, ktime_get());
208 }
209 }
210}
211
212static void nohz_full_kick_work_func(struct irq_work *work)
213{
214 tick_nohz_full_check();
215}
216
217static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
218 .func = nohz_full_kick_work_func,
219};
220
221
222
223
224
225void tick_nohz_full_kick(void)
226{
227 if (tick_nohz_full_cpu(smp_processor_id()))
228 irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
229}
230
231static void nohz_full_kick_ipi(void *info)
232{
233 tick_nohz_full_check();
234}
235
236
237
238
239
240void tick_nohz_full_kick_all(void)
241{
242 if (!have_nohz_full_mask)
243 return;
244
245 preempt_disable();
246 smp_call_function_many(nohz_full_mask,
247 nohz_full_kick_ipi, NULL, false);
248 preempt_enable();
249}
250
251
252
253
254
255
256void tick_nohz_task_switch(struct task_struct *tsk)
257{
258 unsigned long flags;
259
260 local_irq_save(flags);
261
262 if (!tick_nohz_full_cpu(smp_processor_id()))
263 goto out;
264
265 if (tick_nohz_tick_stopped() && !can_stop_full_tick())
266 tick_nohz_full_kick();
267
268out:
269 local_irq_restore(flags);
270}
271
272int tick_nohz_full_cpu(int cpu)
273{
274 if (!have_nohz_full_mask)
275 return 0;
276
277 return cpumask_test_cpu(cpu, nohz_full_mask);
278}
279
280
281static int __init tick_nohz_full_setup(char *str)
282{
283 int cpu;
284
285 alloc_bootmem_cpumask_var(&nohz_full_mask);
286 if (cpulist_parse(str, nohz_full_mask) < 0) {
287 pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
288 return 1;
289 }
290
291 cpu = smp_processor_id();
292 if (cpumask_test_cpu(cpu, nohz_full_mask)) {
293 pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
294 cpumask_clear_cpu(cpu, nohz_full_mask);
295 }
296 have_nohz_full_mask = true;
297
298 return 1;
299}
300__setup("nohz_full=", tick_nohz_full_setup);
301
302static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
303 unsigned long action,
304 void *hcpu)
305{
306 unsigned int cpu = (unsigned long)hcpu;
307
308 switch (action & ~CPU_TASKS_FROZEN) {
309 case CPU_DOWN_PREPARE:
310
311
312
313
314 if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
315 return NOTIFY_BAD;
316 break;
317 }
318 return NOTIFY_OK;
319}
320
321
322
323
324
325
326static char __initdata nohz_full_buf[NR_CPUS + 1];
327
328static int tick_nohz_init_all(void)
329{
330 int err = -1;
331
332#ifdef CONFIG_NO_HZ_FULL_ALL
333 if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) {
334 pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
335 return err;
336 }
337 err = 0;
338 cpumask_setall(nohz_full_mask);
339 cpumask_clear_cpu(smp_processor_id(), nohz_full_mask);
340 have_nohz_full_mask = true;
341#endif
342 return err;
343}
344
345void __init tick_nohz_init(void)
346{
347 if (!have_nohz_full_mask) {
348 if (tick_nohz_init_all() < 0)
349 return;
350 }
351
352 cpu_notifier(tick_nohz_cpu_down_callback, 0);
353 cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask);
354 pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
355}
356#else
357#define have_nohz_full_mask (0)
358#endif
359
360
361
362
363#ifdef CONFIG_NO_HZ_COMMON
364
365
366
367int tick_nohz_enabled __read_mostly = 1;
368
369
370
371
372static int __init setup_tick_nohz(char *str)
373{
374 if (!strcmp(str, "off"))
375 tick_nohz_enabled = 0;
376 else if (!strcmp(str, "on"))
377 tick_nohz_enabled = 1;
378 else
379 return 0;
380 return 1;
381}
382
383__setup("nohz=", setup_tick_nohz);
384
385
386
387
388
389
390
391
392
393
394
395static void tick_nohz_update_jiffies(ktime_t now)
396{
397 int cpu = smp_processor_id();
398 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
399 unsigned long flags;
400
401 ts->idle_waketime = now;
402
403 local_irq_save(flags);
404 tick_do_update_jiffies64(now);
405 local_irq_restore(flags);
406
407 touch_softlockup_watchdog();
408}
409
410
411
412
413static void
414update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
415{
416 ktime_t delta;
417
418 if (ts->idle_active) {
419 delta = ktime_sub(now, ts->idle_entrytime);
420 if (nr_iowait_cpu(cpu) > 0)
421 ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
422 else
423 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
424 ts->idle_entrytime = now;
425 }
426
427 if (last_update_time)
428 *last_update_time = ktime_to_us(now);
429
430}
431
432static void tick_nohz_stop_idle(int cpu, ktime_t now)
433{
434 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
435
436 update_ts_time_stats(cpu, ts, now, NULL);
437 ts->idle_active = 0;
438
439 sched_clock_idle_wakeup_event(0);
440}
441
442static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
443{
444 ktime_t now = ktime_get();
445
446 ts->idle_entrytime = now;
447 ts->idle_active = 1;
448 sched_clock_idle_sleep_event();
449 return now;
450}
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
467{
468 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
469 ktime_t now, idle;
470
471 if (!tick_nohz_enabled)
472 return -1;
473
474 now = ktime_get();
475 if (last_update_time) {
476 update_ts_time_stats(cpu, ts, now, last_update_time);
477 idle = ts->idle_sleeptime;
478 } else {
479 if (ts->idle_active && !nr_iowait_cpu(cpu)) {
480 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
481
482 idle = ktime_add(ts->idle_sleeptime, delta);
483 } else {
484 idle = ts->idle_sleeptime;
485 }
486 }
487
488 return ktime_to_us(idle);
489
490}
491EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
508{
509 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
510 ktime_t now, iowait;
511
512 if (!tick_nohz_enabled)
513 return -1;
514
515 now = ktime_get();
516 if (last_update_time) {
517 update_ts_time_stats(cpu, ts, now, last_update_time);
518 iowait = ts->iowait_sleeptime;
519 } else {
520 if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
521 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
522
523 iowait = ktime_add(ts->iowait_sleeptime, delta);
524 } else {
525 iowait = ts->iowait_sleeptime;
526 }
527 }
528
529 return ktime_to_us(iowait);
530}
531EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
532
533static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
534 ktime_t now, int cpu)
535{
536 unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
537 ktime_t last_update, expires, ret = { .tv64 = 0 };
538 unsigned long rcu_delta_jiffies;
539 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
540 u64 time_delta;
541
542
543 do {
544 seq = read_seqbegin(&jiffies_lock);
545 last_update = last_jiffies_update;
546 last_jiffies = jiffies;
547 time_delta = timekeeping_max_deferment();
548 } while (read_seqretry(&jiffies_lock, seq));
549
550 if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
551 arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
552 next_jiffies = last_jiffies + 1;
553 delta_jiffies = 1;
554 } else {
555
556 next_jiffies = get_next_timer_interrupt(last_jiffies);
557 delta_jiffies = next_jiffies - last_jiffies;
558 if (rcu_delta_jiffies < delta_jiffies) {
559 next_jiffies = last_jiffies + rcu_delta_jiffies;
560 delta_jiffies = rcu_delta_jiffies;
561 }
562 }
563
564
565
566
567
568 if (!ts->tick_stopped && delta_jiffies <= 1)
569 goto out;
570
571
572 if ((long)delta_jiffies >= 1) {
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587 if (cpu == tick_do_timer_cpu) {
588 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
589 ts->do_timer_last = 1;
590 } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
591 time_delta = KTIME_MAX;
592 ts->do_timer_last = 0;
593 } else if (!ts->do_timer_last) {
594 time_delta = KTIME_MAX;
595 }
596
597#ifdef CONFIG_NO_HZ_FULL
598 if (!ts->inidle) {
599 time_delta = min(time_delta,
600 scheduler_tick_max_deferment());
601 }
602#endif
603
604
605
606
607
608
609
610
611 if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
612
613
614
615
616
617
618
619 time_delta = min_t(u64, time_delta,
620 tick_period.tv64 * delta_jiffies);
621 }
622
623 if (time_delta < KTIME_MAX)
624 expires = ktime_add_ns(last_update, time_delta);
625 else
626 expires.tv64 = KTIME_MAX;
627
628
629 if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
630 goto out;
631
632 ret = expires;
633
634
635
636
637
638
639
640
641 if (!ts->tick_stopped) {
642 nohz_balance_enter_idle(cpu);
643 calc_load_enter_idle();
644
645 ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
646 ts->tick_stopped = 1;
647 trace_tick_stop(1, " ");
648 }
649
650
651
652
653
654 if (unlikely(expires.tv64 == KTIME_MAX)) {
655 if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
656 hrtimer_cancel(&ts->sched_timer);
657 goto out;
658 }
659
660 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
661 hrtimer_start(&ts->sched_timer, expires,
662 HRTIMER_MODE_ABS_PINNED);
663
664 if (hrtimer_active(&ts->sched_timer))
665 goto out;
666 } else if (!tick_program_event(expires, 0))
667 goto out;
668
669
670
671
672
673 tick_do_update_jiffies64(ktime_get());
674 }
675 raise_softirq_irqoff(TIMER_SOFTIRQ);
676out:
677 ts->next_jiffies = next_jiffies;
678 ts->last_jiffies = last_jiffies;
679 ts->sleep_length = ktime_sub(dev->next_event, now);
680
681 return ret;
682}
683
684static void tick_nohz_full_stop_tick(struct tick_sched *ts)
685{
686#ifdef CONFIG_NO_HZ_FULL
687 int cpu = smp_processor_id();
688
689 if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
690 return;
691
692 if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
693 return;
694
695 if (!can_stop_full_tick())
696 return;
697
698 tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
699#endif
700}
701
702static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
703{
704
705
706
707
708
709
710
711 if (unlikely(!cpu_online(cpu))) {
712 if (cpu == tick_do_timer_cpu)
713 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
714 return false;
715 }
716
717 if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
718 return false;
719
720 if (need_resched())
721 return false;
722
723 if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
724 static int ratelimit;
725
726 if (ratelimit < 10 &&
727 (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
728 pr_warn("NOHZ: local_softirq_pending %02x\n",
729 (unsigned int) local_softirq_pending());
730 ratelimit++;
731 }
732 return false;
733 }
734
735 if (have_nohz_full_mask) {
736
737
738
739
740 if (tick_do_timer_cpu == cpu)
741 return false;
742
743
744
745
746 if (tick_do_timer_cpu == TICK_DO_TIMER_NONE)
747 return false;
748 }
749
750 return true;
751}
752
753static void __tick_nohz_idle_enter(struct tick_sched *ts)
754{
755 ktime_t now, expires;
756 int cpu = smp_processor_id();
757
758 now = tick_nohz_start_idle(cpu, ts);
759
760 if (can_stop_idle_tick(cpu, ts)) {
761 int was_stopped = ts->tick_stopped;
762
763 ts->idle_calls++;
764
765 expires = tick_nohz_stop_sched_tick(ts, now, cpu);
766 if (expires.tv64 > 0LL) {
767 ts->idle_sleeps++;
768 ts->idle_expires = expires;
769 }
770
771 if (!was_stopped && ts->tick_stopped)
772 ts->idle_jiffies = ts->last_jiffies;
773 }
774}
775
776
777
778
779
780
781
782
783
784
785
786
787
788void tick_nohz_idle_enter(void)
789{
790 struct tick_sched *ts;
791
792 WARN_ON_ONCE(irqs_disabled());
793
794
795
796
797
798
799
800 set_cpu_sd_state_idle();
801
802 local_irq_disable();
803
804 ts = &__get_cpu_var(tick_cpu_sched);
805
806
807
808
809
810 ts->inidle = 1;
811 __tick_nohz_idle_enter(ts);
812
813 local_irq_enable();
814}
815EXPORT_SYMBOL_GPL(tick_nohz_idle_enter);
816
817
818
819
820
821
822
823
824
825void tick_nohz_irq_exit(void)
826{
827 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
828
829 if (ts->inidle)
830 __tick_nohz_idle_enter(ts);
831 else
832 tick_nohz_full_stop_tick(ts);
833}
834
835
836
837
838
839
840ktime_t tick_nohz_get_sleep_length(void)
841{
842 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
843
844 return ts->sleep_length;
845}
846
847static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
848{
849 hrtimer_cancel(&ts->sched_timer);
850 hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
851
852 while (1) {
853
854 hrtimer_forward(&ts->sched_timer, now, tick_period);
855
856 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
857 hrtimer_start_expires(&ts->sched_timer,
858 HRTIMER_MODE_ABS_PINNED);
859
860 if (hrtimer_active(&ts->sched_timer))
861 break;
862 } else {
863 if (!tick_program_event(
864 hrtimer_get_expires(&ts->sched_timer), 0))
865 break;
866 }
867
868 now = ktime_get();
869 tick_do_update_jiffies64(now);
870 }
871}
872
873static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
874{
875
876 tick_do_update_jiffies64(now);
877 update_cpu_load_nohz();
878
879 calc_load_exit_idle();
880 touch_softlockup_watchdog();
881
882
883
884 ts->tick_stopped = 0;
885 ts->idle_exittime = now;
886
887 tick_nohz_restart(ts, now);
888}
889
890static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
891{
892#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
893 unsigned long ticks;
894
895 if (vtime_accounting_enabled())
896 return;
897
898
899
900
901
902 ticks = jiffies - ts->idle_jiffies;
903
904
905
906 if (ticks && ticks < LONG_MAX)
907 account_idle_ticks(ticks);
908#endif
909}
910
911
912
913
914
915
916
917
918void tick_nohz_idle_exit(void)
919{
920 int cpu = smp_processor_id();
921 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
922 ktime_t now;
923
924 local_irq_disable();
925
926 WARN_ON_ONCE(!ts->inidle);
927
928 ts->inidle = 0;
929
930 if (ts->idle_active || ts->tick_stopped)
931 now = ktime_get();
932
933 if (ts->idle_active)
934 tick_nohz_stop_idle(cpu, now);
935
936 if (ts->tick_stopped) {
937 tick_nohz_restart_sched_tick(ts, now);
938 tick_nohz_account_idle_ticks(ts);
939 }
940
941 local_irq_enable();
942}
943EXPORT_SYMBOL_GPL(tick_nohz_idle_exit);
944
945static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
946{
947 hrtimer_forward(&ts->sched_timer, now, tick_period);
948 return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
949}
950
951
952
953
954static void tick_nohz_handler(struct clock_event_device *dev)
955{
956 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
957 struct pt_regs *regs = get_irq_regs();
958 ktime_t now = ktime_get();
959
960 dev->next_event.tv64 = KTIME_MAX;
961
962 tick_sched_do_timer(now);
963 tick_sched_handle(ts, regs);
964
965 while (tick_nohz_reprogram(ts, now)) {
966 now = ktime_get();
967 tick_do_update_jiffies64(now);
968 }
969}
970
971
972
973
974static void tick_nohz_switch_to_nohz(void)
975{
976 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
977 ktime_t next;
978
979 if (!tick_nohz_enabled)
980 return;
981
982 local_irq_disable();
983 if (tick_switch_to_oneshot(tick_nohz_handler)) {
984 local_irq_enable();
985 return;
986 }
987
988 ts->nohz_mode = NOHZ_MODE_LOWRES;
989
990
991
992
993
994 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
995
996 next = tick_init_jiffy_update();
997
998 for (;;) {
999 hrtimer_set_expires(&ts->sched_timer, next);
1000 if (!tick_program_event(next, 0))
1001 break;
1002 next = ktime_add(next, tick_period);
1003 }
1004 local_irq_enable();
1005}
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018static void tick_nohz_kick_tick(int cpu, ktime_t now)
1019{
1020#if 0
1021
1022
1023 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1024 ktime_t delta;
1025
1026
1027
1028
1029
1030 delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
1031 if (delta.tv64 <= tick_period.tv64)
1032 return;
1033
1034 tick_nohz_restart(ts, now);
1035#endif
1036}
1037
1038static inline void tick_check_nohz(int cpu)
1039{
1040 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1041 ktime_t now;
1042
1043 if (!ts->idle_active && !ts->tick_stopped)
1044 return;
1045 now = ktime_get();
1046 if (ts->idle_active)
1047 tick_nohz_stop_idle(cpu, now);
1048 if (ts->tick_stopped) {
1049 tick_nohz_update_jiffies(now);
1050 tick_nohz_kick_tick(cpu, now);
1051 }
1052}
1053
1054#else
1055
1056static inline void tick_nohz_switch_to_nohz(void) { }
1057static inline void tick_check_nohz(int cpu) { }
1058
1059#endif
1060
1061
1062
1063
1064void tick_check_idle(int cpu)
1065{
1066 tick_check_oneshot_broadcast(cpu);
1067 tick_check_nohz(cpu);
1068}
1069
1070
1071
1072
1073#ifdef CONFIG_HIGH_RES_TIMERS
1074
1075
1076
1077
1078static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
1079{
1080 struct tick_sched *ts =
1081 container_of(timer, struct tick_sched, sched_timer);
1082 struct pt_regs *regs = get_irq_regs();
1083 ktime_t now = ktime_get();
1084
1085 tick_sched_do_timer(now);
1086
1087
1088
1089
1090
1091 if (regs)
1092 tick_sched_handle(ts, regs);
1093
1094 hrtimer_forward(timer, now, tick_period);
1095
1096 return HRTIMER_RESTART;
1097}
1098
1099static int sched_skew_tick;
1100
1101static int __init skew_tick(char *str)
1102{
1103 get_option(&str, &sched_skew_tick);
1104
1105 return 0;
1106}
1107early_param("skew_tick", skew_tick);
1108
1109
1110
1111
1112void tick_setup_sched_timer(void)
1113{
1114 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1115 ktime_t now = ktime_get();
1116
1117
1118
1119
1120 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1121 ts->sched_timer.function = tick_sched_timer;
1122
1123
1124 hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
1125
1126
1127 if (sched_skew_tick) {
1128 u64 offset = ktime_to_ns(tick_period) >> 1;
1129 do_div(offset, num_possible_cpus());
1130 offset *= smp_processor_id();
1131 hrtimer_add_expires_ns(&ts->sched_timer, offset);
1132 }
1133
1134 for (;;) {
1135 hrtimer_forward(&ts->sched_timer, now, tick_period);
1136 hrtimer_start_expires(&ts->sched_timer,
1137 HRTIMER_MODE_ABS_PINNED);
1138
1139 if (hrtimer_active(&ts->sched_timer))
1140 break;
1141 now = ktime_get();
1142 }
1143
1144#ifdef CONFIG_NO_HZ_COMMON
1145 if (tick_nohz_enabled)
1146 ts->nohz_mode = NOHZ_MODE_HIGHRES;
1147#endif
1148}
1149#endif
1150
1151#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
1152void tick_cancel_sched_timer(int cpu)
1153{
1154 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1155
1156# ifdef CONFIG_HIGH_RES_TIMERS
1157 if (ts->sched_timer.base)
1158 hrtimer_cancel(&ts->sched_timer);
1159# endif
1160
1161 memset(ts, 0, sizeof(*ts));
1162}
1163#endif
1164
1165
1166
1167
1168void tick_clock_notify(void)
1169{
1170 int cpu;
1171
1172 for_each_possible_cpu(cpu)
1173 set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
1174}
1175
1176
1177
1178
1179void tick_oneshot_notify(void)
1180{
1181 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1182
1183 set_bit(0, &ts->check_clocks);
1184}
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194int tick_check_oneshot_change(int allow_nohz)
1195{
1196 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1197
1198 if (!test_and_clear_bit(0, &ts->check_clocks))
1199 return 0;
1200
1201 if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
1202 return 0;
1203
1204 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
1205 return 0;
1206
1207 if (!allow_nohz)
1208 return 1;
1209
1210 tick_nohz_switch_to_nohz();
1211 return 0;
1212}
1213