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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 return false;
182 }
183#endif
184
185 return true;
186}
187
188static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
189
190
191
192
193
194void tick_nohz_full_check(void)
195{
196 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
197
198 if (tick_nohz_full_cpu(smp_processor_id())) {
199 if (ts->tick_stopped && !is_idle_task(current)) {
200 if (!can_stop_full_tick())
201 tick_nohz_restart_sched_tick(ts, ktime_get());
202 }
203 }
204}
205
206static void nohz_full_kick_work_func(struct irq_work *work)
207{
208 tick_nohz_full_check();
209}
210
211static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
212 .func = nohz_full_kick_work_func,
213};
214
215
216
217
218
219void tick_nohz_full_kick(void)
220{
221 if (tick_nohz_full_cpu(smp_processor_id()))
222 irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
223}
224
225static void nohz_full_kick_ipi(void *info)
226{
227 tick_nohz_full_check();
228}
229
230
231
232
233
234void tick_nohz_full_kick_all(void)
235{
236 if (!have_nohz_full_mask)
237 return;
238
239 preempt_disable();
240 smp_call_function_many(nohz_full_mask,
241 nohz_full_kick_ipi, NULL, false);
242 preempt_enable();
243}
244
245
246
247
248
249
250void tick_nohz_task_switch(struct task_struct *tsk)
251{
252 unsigned long flags;
253
254 local_irq_save(flags);
255
256 if (!tick_nohz_full_cpu(smp_processor_id()))
257 goto out;
258
259 if (tick_nohz_tick_stopped() && !can_stop_full_tick())
260 tick_nohz_full_kick();
261
262out:
263 local_irq_restore(flags);
264}
265
266int tick_nohz_full_cpu(int cpu)
267{
268 if (!have_nohz_full_mask)
269 return 0;
270
271 return cpumask_test_cpu(cpu, nohz_full_mask);
272}
273
274
275static int __init tick_nohz_full_setup(char *str)
276{
277 int cpu;
278
279 alloc_bootmem_cpumask_var(&nohz_full_mask);
280 if (cpulist_parse(str, nohz_full_mask) < 0) {
281 pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
282 return 1;
283 }
284
285 cpu = smp_processor_id();
286 if (cpumask_test_cpu(cpu, nohz_full_mask)) {
287 pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
288 cpumask_clear_cpu(cpu, nohz_full_mask);
289 }
290 have_nohz_full_mask = true;
291
292 return 1;
293}
294__setup("nohz_full=", tick_nohz_full_setup);
295
296static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
297 unsigned long action,
298 void *hcpu)
299{
300 unsigned int cpu = (unsigned long)hcpu;
301
302 switch (action & ~CPU_TASKS_FROZEN) {
303 case CPU_DOWN_PREPARE:
304
305
306
307
308 if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
309 return NOTIFY_BAD;
310 break;
311 }
312 return NOTIFY_OK;
313}
314
315
316
317
318
319
320static char __initdata nohz_full_buf[NR_CPUS + 1];
321
322static int tick_nohz_init_all(void)
323{
324 int err = -1;
325
326#ifdef CONFIG_NO_HZ_FULL_ALL
327 if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) {
328 pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
329 return err;
330 }
331 err = 0;
332 cpumask_setall(nohz_full_mask);
333 cpumask_clear_cpu(smp_processor_id(), nohz_full_mask);
334 have_nohz_full_mask = true;
335#endif
336 return err;
337}
338
339void __init tick_nohz_init(void)
340{
341 int cpu;
342
343 if (!have_nohz_full_mask) {
344 if (tick_nohz_init_all() < 0)
345 return;
346 }
347
348 cpu_notifier(tick_nohz_cpu_down_callback, 0);
349
350
351 for_each_cpu(cpu, nohz_full_mask) {
352 if (!rcu_is_nocb_cpu(cpu)) {
353 pr_warning("NO_HZ: CPU %d is not RCU nocb: "
354 "cleared from nohz_full range", cpu);
355 cpumask_clear_cpu(cpu, nohz_full_mask);
356 }
357 }
358
359 cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask);
360 pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
361}
362#else
363#define have_nohz_full_mask (0)
364#endif
365
366
367
368
369#ifdef CONFIG_NO_HZ_COMMON
370
371
372
373int tick_nohz_enabled __read_mostly = 1;
374
375
376
377
378static int __init setup_tick_nohz(char *str)
379{
380 if (!strcmp(str, "off"))
381 tick_nohz_enabled = 0;
382 else if (!strcmp(str, "on"))
383 tick_nohz_enabled = 1;
384 else
385 return 0;
386 return 1;
387}
388
389__setup("nohz=", setup_tick_nohz);
390
391
392
393
394
395
396
397
398
399
400
401static void tick_nohz_update_jiffies(ktime_t now)
402{
403 int cpu = smp_processor_id();
404 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
405 unsigned long flags;
406
407 ts->idle_waketime = now;
408
409 local_irq_save(flags);
410 tick_do_update_jiffies64(now);
411 local_irq_restore(flags);
412
413 touch_softlockup_watchdog();
414}
415
416
417
418
419static void
420update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
421{
422 ktime_t delta;
423
424 if (ts->idle_active) {
425 delta = ktime_sub(now, ts->idle_entrytime);
426 if (nr_iowait_cpu(cpu) > 0)
427 ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
428 else
429 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
430 ts->idle_entrytime = now;
431 }
432
433 if (last_update_time)
434 *last_update_time = ktime_to_us(now);
435
436}
437
438static void tick_nohz_stop_idle(int cpu, ktime_t now)
439{
440 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
441
442 update_ts_time_stats(cpu, ts, now, NULL);
443 ts->idle_active = 0;
444
445 sched_clock_idle_wakeup_event(0);
446}
447
448static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
449{
450 ktime_t now = ktime_get();
451
452 ts->idle_entrytime = now;
453 ts->idle_active = 1;
454 sched_clock_idle_sleep_event();
455 return now;
456}
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
473{
474 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
475 ktime_t now, idle;
476
477 if (!tick_nohz_enabled)
478 return -1;
479
480 now = ktime_get();
481 if (last_update_time) {
482 update_ts_time_stats(cpu, ts, now, last_update_time);
483 idle = ts->idle_sleeptime;
484 } else {
485 if (ts->idle_active && !nr_iowait_cpu(cpu)) {
486 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
487
488 idle = ktime_add(ts->idle_sleeptime, delta);
489 } else {
490 idle = ts->idle_sleeptime;
491 }
492 }
493
494 return ktime_to_us(idle);
495
496}
497EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
514{
515 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
516 ktime_t now, iowait;
517
518 if (!tick_nohz_enabled)
519 return -1;
520
521 now = ktime_get();
522 if (last_update_time) {
523 update_ts_time_stats(cpu, ts, now, last_update_time);
524 iowait = ts->iowait_sleeptime;
525 } else {
526 if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
527 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
528
529 iowait = ktime_add(ts->iowait_sleeptime, delta);
530 } else {
531 iowait = ts->iowait_sleeptime;
532 }
533 }
534
535 return ktime_to_us(iowait);
536}
537EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
538
539static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
540 ktime_t now, int cpu)
541{
542 unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
543 ktime_t last_update, expires, ret = { .tv64 = 0 };
544 unsigned long rcu_delta_jiffies;
545 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
546 u64 time_delta;
547
548
549 do {
550 seq = read_seqbegin(&jiffies_lock);
551 last_update = last_jiffies_update;
552 last_jiffies = jiffies;
553 time_delta = timekeeping_max_deferment();
554 } while (read_seqretry(&jiffies_lock, seq));
555
556 if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
557 arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
558 next_jiffies = last_jiffies + 1;
559 delta_jiffies = 1;
560 } else {
561
562 next_jiffies = get_next_timer_interrupt(last_jiffies);
563 delta_jiffies = next_jiffies - last_jiffies;
564 if (rcu_delta_jiffies < delta_jiffies) {
565 next_jiffies = last_jiffies + rcu_delta_jiffies;
566 delta_jiffies = rcu_delta_jiffies;
567 }
568 }
569
570
571
572
573
574 if (!ts->tick_stopped && delta_jiffies <= 1)
575 goto out;
576
577
578 if ((long)delta_jiffies >= 1) {
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593 if (cpu == tick_do_timer_cpu) {
594 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
595 ts->do_timer_last = 1;
596 } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
597 time_delta = KTIME_MAX;
598 ts->do_timer_last = 0;
599 } else if (!ts->do_timer_last) {
600 time_delta = KTIME_MAX;
601 }
602
603#ifdef CONFIG_NO_HZ_FULL
604 if (!ts->inidle) {
605 time_delta = min(time_delta,
606 scheduler_tick_max_deferment());
607 }
608#endif
609
610
611
612
613
614
615
616
617 if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
618
619
620
621
622
623
624
625 time_delta = min_t(u64, time_delta,
626 tick_period.tv64 * delta_jiffies);
627 }
628
629 if (time_delta < KTIME_MAX)
630 expires = ktime_add_ns(last_update, time_delta);
631 else
632 expires.tv64 = KTIME_MAX;
633
634
635 if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
636 goto out;
637
638 ret = expires;
639
640
641
642
643
644
645
646
647 if (!ts->tick_stopped) {
648 nohz_balance_enter_idle(cpu);
649 calc_load_enter_idle();
650
651 ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
652 ts->tick_stopped = 1;
653 trace_tick_stop(1, " ");
654 }
655
656
657
658
659
660 if (unlikely(expires.tv64 == KTIME_MAX)) {
661 if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
662 hrtimer_cancel(&ts->sched_timer);
663 goto out;
664 }
665
666 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
667 hrtimer_start(&ts->sched_timer, expires,
668 HRTIMER_MODE_ABS_PINNED);
669
670 if (hrtimer_active(&ts->sched_timer))
671 goto out;
672 } else if (!tick_program_event(expires, 0))
673 goto out;
674
675
676
677
678
679 tick_do_update_jiffies64(ktime_get());
680 }
681 raise_softirq_irqoff(TIMER_SOFTIRQ);
682out:
683 ts->next_jiffies = next_jiffies;
684 ts->last_jiffies = last_jiffies;
685 ts->sleep_length = ktime_sub(dev->next_event, now);
686
687 return ret;
688}
689
690static void tick_nohz_full_stop_tick(struct tick_sched *ts)
691{
692#ifdef CONFIG_NO_HZ_FULL
693 int cpu = smp_processor_id();
694
695 if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
696 return;
697
698 if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
699 return;
700
701 if (!can_stop_full_tick())
702 return;
703
704 tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
705#endif
706}
707
708static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
709{
710
711
712
713
714
715
716
717 if (unlikely(!cpu_online(cpu))) {
718 if (cpu == tick_do_timer_cpu)
719 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
720 return false;
721 }
722
723 if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
724 return false;
725
726 if (need_resched())
727 return false;
728
729 if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
730 static int ratelimit;
731
732 if (ratelimit < 10 &&
733 (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
734 pr_warn("NOHZ: local_softirq_pending %02x\n",
735 (unsigned int) local_softirq_pending());
736 ratelimit++;
737 }
738 return false;
739 }
740
741 if (have_nohz_full_mask) {
742
743
744
745
746 if (tick_do_timer_cpu == cpu)
747 return false;
748
749
750
751
752 if (tick_do_timer_cpu == TICK_DO_TIMER_NONE)
753 return false;
754 }
755
756 return true;
757}
758
759static void __tick_nohz_idle_enter(struct tick_sched *ts)
760{
761 ktime_t now, expires;
762 int cpu = smp_processor_id();
763
764 now = tick_nohz_start_idle(cpu, ts);
765
766 if (can_stop_idle_tick(cpu, ts)) {
767 int was_stopped = ts->tick_stopped;
768
769 ts->idle_calls++;
770
771 expires = tick_nohz_stop_sched_tick(ts, now, cpu);
772 if (expires.tv64 > 0LL) {
773 ts->idle_sleeps++;
774 ts->idle_expires = expires;
775 }
776
777 if (!was_stopped && ts->tick_stopped)
778 ts->idle_jiffies = ts->last_jiffies;
779 }
780}
781
782
783
784
785
786
787
788
789
790
791
792
793
794void tick_nohz_idle_enter(void)
795{
796 struct tick_sched *ts;
797
798 WARN_ON_ONCE(irqs_disabled());
799
800
801
802
803
804
805
806 set_cpu_sd_state_idle();
807
808 local_irq_disable();
809
810 ts = &__get_cpu_var(tick_cpu_sched);
811
812
813
814
815
816 ts->inidle = 1;
817 __tick_nohz_idle_enter(ts);
818
819 local_irq_enable();
820}
821EXPORT_SYMBOL_GPL(tick_nohz_idle_enter);
822
823
824
825
826
827
828
829
830
831void tick_nohz_irq_exit(void)
832{
833 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
834
835 if (ts->inidle) {
836
837 menu_hrtimer_cancel();
838 __tick_nohz_idle_enter(ts);
839 } else {
840 tick_nohz_full_stop_tick(ts);
841 }
842}
843
844
845
846
847
848
849ktime_t tick_nohz_get_sleep_length(void)
850{
851 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
852
853 return ts->sleep_length;
854}
855
856static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
857{
858 hrtimer_cancel(&ts->sched_timer);
859 hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
860
861 while (1) {
862
863 hrtimer_forward(&ts->sched_timer, now, tick_period);
864
865 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
866 hrtimer_start_expires(&ts->sched_timer,
867 HRTIMER_MODE_ABS_PINNED);
868
869 if (hrtimer_active(&ts->sched_timer))
870 break;
871 } else {
872 if (!tick_program_event(
873 hrtimer_get_expires(&ts->sched_timer), 0))
874 break;
875 }
876
877 now = ktime_get();
878 tick_do_update_jiffies64(now);
879 }
880}
881
882static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
883{
884
885 tick_do_update_jiffies64(now);
886 update_cpu_load_nohz();
887
888 calc_load_exit_idle();
889 touch_softlockup_watchdog();
890
891
892
893 ts->tick_stopped = 0;
894 ts->idle_exittime = now;
895
896 tick_nohz_restart(ts, now);
897}
898
899static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
900{
901#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
902 unsigned long ticks;
903
904 if (vtime_accounting_enabled())
905 return;
906
907
908
909
910
911 ticks = jiffies - ts->idle_jiffies;
912
913
914
915 if (ticks && ticks < LONG_MAX)
916 account_idle_ticks(ticks);
917#endif
918}
919
920
921
922
923
924
925
926
927void tick_nohz_idle_exit(void)
928{
929 int cpu = smp_processor_id();
930 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
931 ktime_t now;
932
933 local_irq_disable();
934
935 WARN_ON_ONCE(!ts->inidle);
936
937 ts->inidle = 0;
938
939
940 menu_hrtimer_cancel();
941 if (ts->idle_active || ts->tick_stopped)
942 now = ktime_get();
943
944 if (ts->idle_active)
945 tick_nohz_stop_idle(cpu, now);
946
947 if (ts->tick_stopped) {
948 tick_nohz_restart_sched_tick(ts, now);
949 tick_nohz_account_idle_ticks(ts);
950 }
951
952 local_irq_enable();
953}
954EXPORT_SYMBOL_GPL(tick_nohz_idle_exit);
955
956static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
957{
958 hrtimer_forward(&ts->sched_timer, now, tick_period);
959 return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
960}
961
962
963
964
965static void tick_nohz_handler(struct clock_event_device *dev)
966{
967 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
968 struct pt_regs *regs = get_irq_regs();
969 ktime_t now = ktime_get();
970
971 dev->next_event.tv64 = KTIME_MAX;
972
973 tick_sched_do_timer(now);
974 tick_sched_handle(ts, regs);
975
976 while (tick_nohz_reprogram(ts, now)) {
977 now = ktime_get();
978 tick_do_update_jiffies64(now);
979 }
980}
981
982
983
984
985static void tick_nohz_switch_to_nohz(void)
986{
987 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
988 ktime_t next;
989
990 if (!tick_nohz_enabled)
991 return;
992
993 local_irq_disable();
994 if (tick_switch_to_oneshot(tick_nohz_handler)) {
995 local_irq_enable();
996 return;
997 }
998
999 ts->nohz_mode = NOHZ_MODE_LOWRES;
1000
1001
1002
1003
1004
1005 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1006
1007 next = tick_init_jiffy_update();
1008
1009 for (;;) {
1010 hrtimer_set_expires(&ts->sched_timer, next);
1011 if (!tick_program_event(next, 0))
1012 break;
1013 next = ktime_add(next, tick_period);
1014 }
1015 local_irq_enable();
1016}
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029static void tick_nohz_kick_tick(int cpu, ktime_t now)
1030{
1031#if 0
1032
1033
1034 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1035 ktime_t delta;
1036
1037
1038
1039
1040
1041 delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
1042 if (delta.tv64 <= tick_period.tv64)
1043 return;
1044
1045 tick_nohz_restart(ts, now);
1046#endif
1047}
1048
1049static inline void tick_check_nohz(int cpu)
1050{
1051 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1052 ktime_t now;
1053
1054 if (!ts->idle_active && !ts->tick_stopped)
1055 return;
1056 now = ktime_get();
1057 if (ts->idle_active)
1058 tick_nohz_stop_idle(cpu, now);
1059 if (ts->tick_stopped) {
1060 tick_nohz_update_jiffies(now);
1061 tick_nohz_kick_tick(cpu, now);
1062 }
1063}
1064
1065#else
1066
1067static inline void tick_nohz_switch_to_nohz(void) { }
1068static inline void tick_check_nohz(int cpu) { }
1069
1070#endif
1071
1072
1073
1074
1075void tick_check_idle(int cpu)
1076{
1077 tick_check_oneshot_broadcast(cpu);
1078 tick_check_nohz(cpu);
1079}
1080
1081
1082
1083
1084#ifdef CONFIG_HIGH_RES_TIMERS
1085
1086
1087
1088
1089static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
1090{
1091 struct tick_sched *ts =
1092 container_of(timer, struct tick_sched, sched_timer);
1093 struct pt_regs *regs = get_irq_regs();
1094 ktime_t now = ktime_get();
1095
1096 tick_sched_do_timer(now);
1097
1098
1099
1100
1101
1102 if (regs)
1103 tick_sched_handle(ts, regs);
1104
1105 hrtimer_forward(timer, now, tick_period);
1106
1107 return HRTIMER_RESTART;
1108}
1109
1110static int sched_skew_tick;
1111
1112static int __init skew_tick(char *str)
1113{
1114 get_option(&str, &sched_skew_tick);
1115
1116 return 0;
1117}
1118early_param("skew_tick", skew_tick);
1119
1120
1121
1122
1123void tick_setup_sched_timer(void)
1124{
1125 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1126 ktime_t now = ktime_get();
1127
1128
1129
1130
1131 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1132 ts->sched_timer.function = tick_sched_timer;
1133
1134
1135 hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
1136
1137
1138 if (sched_skew_tick) {
1139 u64 offset = ktime_to_ns(tick_period) >> 1;
1140 do_div(offset, num_possible_cpus());
1141 offset *= smp_processor_id();
1142 hrtimer_add_expires_ns(&ts->sched_timer, offset);
1143 }
1144
1145 for (;;) {
1146 hrtimer_forward(&ts->sched_timer, now, tick_period);
1147 hrtimer_start_expires(&ts->sched_timer,
1148 HRTIMER_MODE_ABS_PINNED);
1149
1150 if (hrtimer_active(&ts->sched_timer))
1151 break;
1152 now = ktime_get();
1153 }
1154
1155#ifdef CONFIG_NO_HZ_COMMON
1156 if (tick_nohz_enabled)
1157 ts->nohz_mode = NOHZ_MODE_HIGHRES;
1158#endif
1159}
1160#endif
1161
1162#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
1163void tick_cancel_sched_timer(int cpu)
1164{
1165 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1166
1167# ifdef CONFIG_HIGH_RES_TIMERS
1168 if (ts->sched_timer.base)
1169 hrtimer_cancel(&ts->sched_timer);
1170# endif
1171
1172 memset(ts, 0, sizeof(*ts));
1173}
1174#endif
1175
1176
1177
1178
1179void tick_clock_notify(void)
1180{
1181 int cpu;
1182
1183 for_each_possible_cpu(cpu)
1184 set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
1185}
1186
1187
1188
1189
1190void tick_oneshot_notify(void)
1191{
1192 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1193
1194 set_bit(0, &ts->check_clocks);
1195}
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205int tick_check_oneshot_change(int allow_nohz)
1206{
1207 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
1208
1209 if (!test_and_clear_bit(0, &ts->check_clocks))
1210 return 0;
1211
1212 if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
1213 return 0;
1214
1215 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
1216 return 0;
1217
1218 if (!allow_nohz)
1219 return 1;
1220
1221 tick_nohz_switch_to_nohz();
1222 return 0;
1223}
1224