Commit | Line | Data |
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79bf2bb3 TG |
1 | /* |
2 | * linux/kernel/time/tick-sched.c | |
3 | * | |
4 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> | |
5 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar | |
6 | * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner | |
7 | * | |
8 | * No idle tick implementation for low and high resolution timers | |
9 | * | |
10 | * Started by: Thomas Gleixner and Ingo Molnar | |
11 | * | |
b10db7f0 | 12 | * Distribute under GPLv2. |
79bf2bb3 TG |
13 | */ |
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/tick.h> | |
23 | ||
9e203bcc DM |
24 | #include <asm/irq_regs.h> |
25 | ||
79bf2bb3 TG |
26 | #include "tick-internal.h" |
27 | ||
28 | /* | |
29 | * Per cpu nohz control structure | |
30 | */ | |
31 | static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); | |
32 | ||
33 | /* | |
34 | * The time, when the last jiffy update happened. Protected by xtime_lock. | |
35 | */ | |
36 | static ktime_t last_jiffies_update; | |
37 | ||
289f480a IM |
38 | struct tick_sched *tick_get_tick_sched(int cpu) |
39 | { | |
40 | return &per_cpu(tick_cpu_sched, cpu); | |
41 | } | |
42 | ||
79bf2bb3 TG |
43 | /* |
44 | * Must be called with interrupts disabled ! | |
45 | */ | |
46 | static void tick_do_update_jiffies64(ktime_t now) | |
47 | { | |
48 | unsigned long ticks = 0; | |
49 | ktime_t delta; | |
50 | ||
51 | /* Reevalute with xtime_lock held */ | |
52 | write_seqlock(&xtime_lock); | |
53 | ||
54 | delta = ktime_sub(now, last_jiffies_update); | |
55 | if (delta.tv64 >= tick_period.tv64) { | |
56 | ||
57 | delta = ktime_sub(delta, tick_period); | |
58 | last_jiffies_update = ktime_add(last_jiffies_update, | |
59 | tick_period); | |
60 | ||
61 | /* Slow path for long timeouts */ | |
62 | if (unlikely(delta.tv64 >= tick_period.tv64)) { | |
63 | s64 incr = ktime_to_ns(tick_period); | |
64 | ||
65 | ticks = ktime_divns(delta, incr); | |
66 | ||
67 | last_jiffies_update = ktime_add_ns(last_jiffies_update, | |
68 | incr * ticks); | |
69 | } | |
70 | do_timer(++ticks); | |
71 | } | |
72 | write_sequnlock(&xtime_lock); | |
73 | } | |
74 | ||
75 | /* | |
76 | * Initialize and return retrieve the jiffies update. | |
77 | */ | |
78 | static ktime_t tick_init_jiffy_update(void) | |
79 | { | |
80 | ktime_t period; | |
81 | ||
82 | write_seqlock(&xtime_lock); | |
83 | /* Did we start the jiffies update yet ? */ | |
84 | if (last_jiffies_update.tv64 == 0) | |
85 | last_jiffies_update = tick_next_period; | |
86 | period = last_jiffies_update; | |
87 | write_sequnlock(&xtime_lock); | |
88 | return period; | |
89 | } | |
90 | ||
91 | /* | |
92 | * NOHZ - aka dynamic tick functionality | |
93 | */ | |
94 | #ifdef CONFIG_NO_HZ | |
95 | /* | |
96 | * NO HZ enabled ? | |
97 | */ | |
98 | static int tick_nohz_enabled __read_mostly = 1; | |
99 | ||
100 | /* | |
101 | * Enable / Disable tickless mode | |
102 | */ | |
103 | static int __init setup_tick_nohz(char *str) | |
104 | { | |
105 | if (!strcmp(str, "off")) | |
106 | tick_nohz_enabled = 0; | |
107 | else if (!strcmp(str, "on")) | |
108 | tick_nohz_enabled = 1; | |
109 | else | |
110 | return 0; | |
111 | return 1; | |
112 | } | |
113 | ||
114 | __setup("nohz=", setup_tick_nohz); | |
115 | ||
116 | /** | |
117 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
118 | * | |
119 | * Called from interrupt entry when the CPU was idle | |
120 | * | |
121 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
122 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
123 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
124 | * cpu, which has the update task assigned is in a long sleep. | |
125 | */ | |
126 | void tick_nohz_update_jiffies(void) | |
127 | { | |
128 | int cpu = smp_processor_id(); | |
129 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
130 | unsigned long flags; | |
131 | ktime_t now; | |
132 | ||
133 | if (!ts->tick_stopped) | |
134 | return; | |
135 | ||
d3938204 TG |
136 | touch_softlockup_watchdog(); |
137 | ||
79bf2bb3 TG |
138 | cpu_clear(cpu, nohz_cpu_mask); |
139 | now = ktime_get(); | |
5df7fa1c | 140 | ts->idle_waketime = now; |
79bf2bb3 TG |
141 | |
142 | local_irq_save(flags); | |
143 | tick_do_update_jiffies64(now); | |
144 | local_irq_restore(flags); | |
145 | } | |
146 | ||
6378ddb5 VP |
147 | void tick_nohz_stop_idle(int cpu) |
148 | { | |
149 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
150 | ||
151 | if (ts->idle_active) { | |
152 | ktime_t now, delta; | |
153 | now = ktime_get(); | |
154 | delta = ktime_sub(now, ts->idle_entrytime); | |
155 | ts->idle_lastupdate = now; | |
156 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
157 | ts->idle_active = 0; | |
158 | } | |
159 | } | |
160 | ||
161 | static ktime_t tick_nohz_start_idle(int cpu) | |
162 | { | |
163 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
164 | ktime_t now, delta; | |
165 | ||
166 | now = ktime_get(); | |
167 | if (ts->idle_active) { | |
168 | delta = ktime_sub(now, ts->idle_entrytime); | |
169 | ts->idle_lastupdate = now; | |
170 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
171 | } | |
172 | ts->idle_entrytime = now; | |
173 | ts->idle_active = 1; | |
174 | return now; | |
175 | } | |
176 | ||
177 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) | |
178 | { | |
179 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
180 | ||
181 | *last_update_time = ktime_to_us(ts->idle_lastupdate); | |
182 | return ktime_to_us(ts->idle_sleeptime); | |
183 | } | |
184 | ||
79bf2bb3 TG |
185 | /** |
186 | * tick_nohz_stop_sched_tick - stop the idle tick from the idle task | |
187 | * | |
188 | * When the next event is more than a tick into the future, stop the idle tick | |
189 | * Called either from the idle loop or from irq_exit() when an idle period was | |
190 | * just interrupted by an interrupt which did not cause a reschedule. | |
191 | */ | |
192 | void tick_nohz_stop_sched_tick(void) | |
193 | { | |
194 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; | |
48d5e258 | 195 | unsigned long rt_jiffies; |
79bf2bb3 | 196 | struct tick_sched *ts; |
6378ddb5 | 197 | ktime_t last_update, expires, now; |
4f86d3a8 | 198 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
79bf2bb3 TG |
199 | int cpu; |
200 | ||
201 | local_irq_save(flags); | |
202 | ||
203 | cpu = smp_processor_id(); | |
6378ddb5 | 204 | now = tick_nohz_start_idle(cpu); |
79bf2bb3 TG |
205 | ts = &per_cpu(tick_cpu_sched, cpu); |
206 | ||
5e41d0d6 TG |
207 | /* |
208 | * If this cpu is offline and it is the one which updates | |
209 | * jiffies, then give up the assignment and let it be taken by | |
210 | * the cpu which runs the tick timer next. If we don't drop | |
211 | * this here the jiffies might be stale and do_timer() never | |
212 | * invoked. | |
213 | */ | |
214 | if (unlikely(!cpu_online(cpu))) { | |
215 | if (cpu == tick_do_timer_cpu) | |
216 | tick_do_timer_cpu = -1; | |
217 | } | |
218 | ||
79bf2bb3 TG |
219 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
220 | goto end; | |
221 | ||
222 | if (need_resched()) | |
223 | goto end; | |
224 | ||
225 | cpu = smp_processor_id(); | |
35282316 TG |
226 | if (unlikely(local_softirq_pending())) { |
227 | static int ratelimit; | |
228 | ||
229 | if (ratelimit < 10) { | |
230 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", | |
231 | local_softirq_pending()); | |
232 | ratelimit++; | |
233 | } | |
234 | } | |
79bf2bb3 | 235 | |
79bf2bb3 | 236 | ts->idle_calls++; |
79bf2bb3 TG |
237 | /* Read jiffies and the time when jiffies were updated last */ |
238 | do { | |
239 | seq = read_seqbegin(&xtime_lock); | |
240 | last_update = last_jiffies_update; | |
241 | last_jiffies = jiffies; | |
242 | } while (read_seqretry(&xtime_lock, seq)); | |
243 | ||
244 | /* Get the next timer wheel timer */ | |
245 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
246 | delta_jiffies = next_jiffies - last_jiffies; | |
247 | ||
48d5e258 PZ |
248 | rt_jiffies = rt_needs_cpu(cpu); |
249 | if (rt_jiffies && rt_jiffies < delta_jiffies) | |
250 | delta_jiffies = rt_jiffies; | |
251 | ||
6ba9b346 IM |
252 | if (rcu_needs_cpu(cpu)) |
253 | delta_jiffies = 1; | |
79bf2bb3 TG |
254 | /* |
255 | * Do not stop the tick, if we are only one off | |
256 | * or if the cpu is required for rcu | |
257 | */ | |
6ba9b346 | 258 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
259 | goto out; |
260 | ||
261 | /* Schedule the tick, if we are at least one jiffie off */ | |
262 | if ((long)delta_jiffies >= 1) { | |
263 | ||
6ba9b346 | 264 | if (delta_jiffies > 1) |
79bf2bb3 TG |
265 | cpu_set(cpu, nohz_cpu_mask); |
266 | /* | |
267 | * nohz_stop_sched_tick can be called several times before | |
268 | * the nohz_restart_sched_tick is called. This happens when | |
269 | * interrupts arrive which do not cause a reschedule. In the | |
270 | * first call we save the current tick time, so we can restart | |
271 | * the scheduler tick in nohz_restart_sched_tick. | |
272 | */ | |
273 | if (!ts->tick_stopped) { | |
46cb4b7c SS |
274 | if (select_nohz_load_balancer(1)) { |
275 | /* | |
276 | * sched tick not stopped! | |
277 | */ | |
278 | cpu_clear(cpu, nohz_cpu_mask); | |
279 | goto out; | |
280 | } | |
281 | ||
79bf2bb3 TG |
282 | ts->idle_tick = ts->sched_timer.expires; |
283 | ts->tick_stopped = 1; | |
284 | ts->idle_jiffies = last_jiffies; | |
2232c2d8 | 285 | rcu_enter_nohz(); |
79bf2bb3 | 286 | } |
d3ed7824 TG |
287 | |
288 | /* | |
289 | * If this cpu is the one which updates jiffies, then | |
290 | * give up the assignment and let it be taken by the | |
291 | * cpu which runs the tick timer next, which might be | |
292 | * this cpu as well. If we don't drop this here the | |
293 | * jiffies might be stale and do_timer() never | |
294 | * invoked. | |
295 | */ | |
296 | if (cpu == tick_do_timer_cpu) | |
297 | tick_do_timer_cpu = -1; | |
298 | ||
eaad084b TG |
299 | ts->idle_sleeps++; |
300 | ||
301 | /* | |
302 | * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that | |
303 | * there is no timer pending or at least extremly far | |
304 | * into the future (12 days for HZ=1000). In this case | |
305 | * we simply stop the tick timer: | |
306 | */ | |
307 | if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) { | |
308 | ts->idle_expires.tv64 = KTIME_MAX; | |
309 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) | |
310 | hrtimer_cancel(&ts->sched_timer); | |
311 | goto out; | |
312 | } | |
313 | ||
79bf2bb3 TG |
314 | /* |
315 | * calculate the expiry time for the next timer wheel | |
316 | * timer | |
317 | */ | |
318 | expires = ktime_add_ns(last_update, tick_period.tv64 * | |
319 | delta_jiffies); | |
320 | ts->idle_expires = expires; | |
79bf2bb3 TG |
321 | |
322 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
323 | hrtimer_start(&ts->sched_timer, expires, | |
324 | HRTIMER_MODE_ABS); | |
325 | /* Check, if the timer was already in the past */ | |
326 | if (hrtimer_active(&ts->sched_timer)) | |
327 | goto out; | |
4c9dc641 | 328 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
329 | goto out; |
330 | /* | |
331 | * We are past the event already. So we crossed a | |
332 | * jiffie boundary. Update jiffies and raise the | |
333 | * softirq. | |
334 | */ | |
335 | tick_do_update_jiffies64(ktime_get()); | |
336 | cpu_clear(cpu, nohz_cpu_mask); | |
337 | } | |
338 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
339 | out: | |
340 | ts->next_jiffies = next_jiffies; | |
341 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 342 | ts->sleep_length = ktime_sub(dev->next_event, now); |
79bf2bb3 TG |
343 | end: |
344 | local_irq_restore(flags); | |
345 | } | |
346 | ||
4f86d3a8 LB |
347 | /** |
348 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
349 | * | |
350 | * Called from power state control code with interrupts disabled | |
351 | */ | |
352 | ktime_t tick_nohz_get_sleep_length(void) | |
353 | { | |
354 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
355 | ||
356 | return ts->sleep_length; | |
357 | } | |
358 | ||
79bf2bb3 | 359 | /** |
8dce39c2 | 360 | * tick_nohz_restart_sched_tick - restart the idle tick from the idle task |
79bf2bb3 TG |
361 | * |
362 | * Restart the idle tick when the CPU is woken up from idle | |
363 | */ | |
364 | void tick_nohz_restart_sched_tick(void) | |
365 | { | |
366 | int cpu = smp_processor_id(); | |
367 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
368 | unsigned long ticks; | |
6378ddb5 | 369 | ktime_t now; |
79bf2bb3 | 370 | |
6378ddb5 VP |
371 | local_irq_disable(); |
372 | tick_nohz_stop_idle(cpu); | |
373 | ||
374 | if (!ts->tick_stopped) { | |
375 | local_irq_enable(); | |
79bf2bb3 | 376 | return; |
6378ddb5 | 377 | } |
79bf2bb3 | 378 | |
2232c2d8 SR |
379 | rcu_exit_nohz(); |
380 | ||
79bf2bb3 | 381 | /* Update jiffies first */ |
46cb4b7c | 382 | select_nohz_load_balancer(0); |
6378ddb5 | 383 | now = ktime_get(); |
79bf2bb3 TG |
384 | tick_do_update_jiffies64(now); |
385 | cpu_clear(cpu, nohz_cpu_mask); | |
386 | ||
79bf2bb3 TG |
387 | /* |
388 | * We stopped the tick in idle. Update process times would miss the | |
389 | * time we slept as update_process_times does only a 1 tick | |
390 | * accounting. Enforce that this is accounted to idle ! | |
391 | */ | |
392 | ticks = jiffies - ts->idle_jiffies; | |
393 | /* | |
394 | * We might be one off. Do not randomly account a huge number of ticks! | |
395 | */ | |
396 | if (ticks && ticks < LONG_MAX) { | |
397 | add_preempt_count(HARDIRQ_OFFSET); | |
398 | account_system_time(current, HARDIRQ_OFFSET, | |
399 | jiffies_to_cputime(ticks)); | |
400 | sub_preempt_count(HARDIRQ_OFFSET); | |
401 | } | |
402 | ||
403 | /* | |
404 | * Cancel the scheduled timer and restore the tick | |
405 | */ | |
406 | ts->tick_stopped = 0; | |
5df7fa1c | 407 | ts->idle_exittime = now; |
79bf2bb3 TG |
408 | hrtimer_cancel(&ts->sched_timer); |
409 | ts->sched_timer.expires = ts->idle_tick; | |
410 | ||
411 | while (1) { | |
412 | /* Forward the time to expire in the future */ | |
413 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
414 | ||
415 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
416 | hrtimer_start(&ts->sched_timer, | |
417 | ts->sched_timer.expires, | |
418 | HRTIMER_MODE_ABS); | |
419 | /* Check, if the timer was already in the past */ | |
420 | if (hrtimer_active(&ts->sched_timer)) | |
421 | break; | |
422 | } else { | |
423 | if (!tick_program_event(ts->sched_timer.expires, 0)) | |
424 | break; | |
425 | } | |
426 | /* Update jiffies and reread time */ | |
427 | tick_do_update_jiffies64(now); | |
428 | now = ktime_get(); | |
429 | } | |
430 | local_irq_enable(); | |
431 | } | |
432 | ||
433 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
434 | { | |
435 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
436 | return tick_program_event(ts->sched_timer.expires, 0); | |
437 | } | |
438 | ||
439 | /* | |
440 | * The nohz low res interrupt handler | |
441 | */ | |
442 | static void tick_nohz_handler(struct clock_event_device *dev) | |
443 | { | |
444 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
445 | struct pt_regs *regs = get_irq_regs(); | |
d3ed7824 | 446 | int cpu = smp_processor_id(); |
79bf2bb3 TG |
447 | ktime_t now = ktime_get(); |
448 | ||
449 | dev->next_event.tv64 = KTIME_MAX; | |
450 | ||
d3ed7824 TG |
451 | /* |
452 | * Check if the do_timer duty was dropped. We don't care about | |
453 | * concurrency: This happens only when the cpu in charge went | |
454 | * into a long sleep. If two cpus happen to assign themself to | |
455 | * this duty, then the jiffies update is still serialized by | |
456 | * xtime_lock. | |
457 | */ | |
458 | if (unlikely(tick_do_timer_cpu == -1)) | |
459 | tick_do_timer_cpu = cpu; | |
460 | ||
79bf2bb3 | 461 | /* Check, if the jiffies need an update */ |
d3ed7824 TG |
462 | if (tick_do_timer_cpu == cpu) |
463 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
464 | |
465 | /* | |
466 | * When we are idle and the tick is stopped, we have to touch | |
467 | * the watchdog as we might not schedule for a really long | |
468 | * time. This happens on complete idle SMP systems while | |
469 | * waiting on the login prompt. We also increment the "start | |
470 | * of idle" jiffy stamp so the idle accounting adjustment we | |
471 | * do when we go busy again does not account too much ticks. | |
472 | */ | |
473 | if (ts->tick_stopped) { | |
474 | touch_softlockup_watchdog(); | |
475 | ts->idle_jiffies++; | |
476 | } | |
477 | ||
478 | update_process_times(user_mode(regs)); | |
479 | profile_tick(CPU_PROFILING); | |
480 | ||
481 | /* Do not restart, when we are in the idle loop */ | |
482 | if (ts->tick_stopped) | |
483 | return; | |
484 | ||
485 | while (tick_nohz_reprogram(ts, now)) { | |
486 | now = ktime_get(); | |
487 | tick_do_update_jiffies64(now); | |
488 | } | |
489 | } | |
490 | ||
491 | /** | |
492 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
493 | */ | |
494 | static void tick_nohz_switch_to_nohz(void) | |
495 | { | |
496 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
497 | ktime_t next; | |
498 | ||
499 | if (!tick_nohz_enabled) | |
500 | return; | |
501 | ||
502 | local_irq_disable(); | |
503 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
504 | local_irq_enable(); | |
505 | return; | |
506 | } | |
507 | ||
508 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
509 | ||
510 | /* | |
511 | * Recycle the hrtimer in ts, so we can share the | |
512 | * hrtimer_forward with the highres code. | |
513 | */ | |
514 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
515 | /* Get the next period */ | |
516 | next = tick_init_jiffy_update(); | |
517 | ||
518 | for (;;) { | |
519 | ts->sched_timer.expires = next; | |
520 | if (!tick_program_event(next, 0)) | |
521 | break; | |
522 | next = ktime_add(next, tick_period); | |
523 | } | |
524 | local_irq_enable(); | |
525 | ||
526 | printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", | |
527 | smp_processor_id()); | |
528 | } | |
529 | ||
530 | #else | |
531 | ||
532 | static inline void tick_nohz_switch_to_nohz(void) { } | |
533 | ||
534 | #endif /* NO_HZ */ | |
535 | ||
536 | /* | |
537 | * High resolution timer specific code | |
538 | */ | |
539 | #ifdef CONFIG_HIGH_RES_TIMERS | |
540 | /* | |
4c9dc641 | 541 | * We rearm the timer until we get disabled by the idle code. |
79bf2bb3 TG |
542 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
543 | */ | |
544 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
545 | { | |
546 | struct tick_sched *ts = | |
547 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
548 | struct pt_regs *regs = get_irq_regs(); |
549 | ktime_t now = ktime_get(); | |
d3ed7824 TG |
550 | int cpu = smp_processor_id(); |
551 | ||
552 | #ifdef CONFIG_NO_HZ | |
553 | /* | |
554 | * Check if the do_timer duty was dropped. We don't care about | |
555 | * concurrency: This happens only when the cpu in charge went | |
556 | * into a long sleep. If two cpus happen to assign themself to | |
557 | * this duty, then the jiffies update is still serialized by | |
558 | * xtime_lock. | |
559 | */ | |
560 | if (unlikely(tick_do_timer_cpu == -1)) | |
561 | tick_do_timer_cpu = cpu; | |
562 | #endif | |
79bf2bb3 TG |
563 | |
564 | /* Check, if the jiffies need an update */ | |
d3ed7824 TG |
565 | if (tick_do_timer_cpu == cpu) |
566 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
567 | |
568 | /* | |
569 | * Do not call, when we are not in irq context and have | |
570 | * no valid regs pointer | |
571 | */ | |
572 | if (regs) { | |
573 | /* | |
574 | * When we are idle and the tick is stopped, we have to touch | |
575 | * the watchdog as we might not schedule for a really long | |
576 | * time. This happens on complete idle SMP systems while | |
577 | * waiting on the login prompt. We also increment the "start of | |
578 | * idle" jiffy stamp so the idle accounting adjustment we do | |
579 | * when we go busy again does not account too much ticks. | |
580 | */ | |
581 | if (ts->tick_stopped) { | |
582 | touch_softlockup_watchdog(); | |
583 | ts->idle_jiffies++; | |
584 | } | |
79bf2bb3 TG |
585 | update_process_times(user_mode(regs)); |
586 | profile_tick(CPU_PROFILING); | |
79bf2bb3 TG |
587 | } |
588 | ||
589 | /* Do not restart, when we are in the idle loop */ | |
590 | if (ts->tick_stopped) | |
591 | return HRTIMER_NORESTART; | |
592 | ||
593 | hrtimer_forward(timer, now, tick_period); | |
594 | ||
595 | return HRTIMER_RESTART; | |
596 | } | |
597 | ||
598 | /** | |
599 | * tick_setup_sched_timer - setup the tick emulation timer | |
600 | */ | |
601 | void tick_setup_sched_timer(void) | |
602 | { | |
603 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
604 | ktime_t now = ktime_get(); | |
3704540b | 605 | u64 offset; |
79bf2bb3 TG |
606 | |
607 | /* | |
608 | * Emulate tick processing via per-CPU hrtimers: | |
609 | */ | |
610 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
611 | ts->sched_timer.function = tick_sched_timer; | |
612 | ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ; | |
613 | ||
3704540b | 614 | /* Get the next period (per cpu) */ |
79bf2bb3 | 615 | ts->sched_timer.expires = tick_init_jiffy_update(); |
3704540b | 616 | offset = ktime_to_ns(tick_period) >> 1; |
b2d9323d | 617 | do_div(offset, num_possible_cpus()); |
3704540b | 618 | offset *= smp_processor_id(); |
619 | ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset); | |
79bf2bb3 TG |
620 | |
621 | for (;;) { | |
622 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
623 | hrtimer_start(&ts->sched_timer, ts->sched_timer.expires, | |
624 | HRTIMER_MODE_ABS); | |
625 | /* Check, if the timer was already in the past */ | |
626 | if (hrtimer_active(&ts->sched_timer)) | |
627 | break; | |
628 | now = ktime_get(); | |
629 | } | |
630 | ||
631 | #ifdef CONFIG_NO_HZ | |
632 | if (tick_nohz_enabled) | |
633 | ts->nohz_mode = NOHZ_MODE_HIGHRES; | |
634 | #endif | |
635 | } | |
636 | ||
637 | void tick_cancel_sched_timer(int cpu) | |
638 | { | |
639 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
640 | ||
641 | if (ts->sched_timer.base) | |
642 | hrtimer_cancel(&ts->sched_timer); | |
a7901766 | 643 | |
79bf2bb3 TG |
644 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
645 | } | |
646 | #endif /* HIGH_RES_TIMERS */ | |
647 | ||
648 | /** | |
649 | * Async notification about clocksource changes | |
650 | */ | |
651 | void tick_clock_notify(void) | |
652 | { | |
653 | int cpu; | |
654 | ||
655 | for_each_possible_cpu(cpu) | |
656 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
657 | } | |
658 | ||
659 | /* | |
660 | * Async notification about clock event changes | |
661 | */ | |
662 | void tick_oneshot_notify(void) | |
663 | { | |
664 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
665 | ||
666 | set_bit(0, &ts->check_clocks); | |
667 | } | |
668 | ||
669 | /** | |
670 | * Check, if a change happened, which makes oneshot possible. | |
671 | * | |
672 | * Called cyclic from the hrtimer softirq (driven by the timer | |
673 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
674 | * mode, because high resolution timers are disabled (either compile | |
675 | * or runtime). | |
676 | */ | |
677 | int tick_check_oneshot_change(int allow_nohz) | |
678 | { | |
679 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
680 | ||
681 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
682 | return 0; | |
683 | ||
684 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
685 | return 0; | |
686 | ||
cf4fc6cb | 687 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
688 | return 0; |
689 | ||
690 | if (!allow_nohz) | |
691 | return 1; | |
692 | ||
693 | tick_nohz_switch_to_nohz(); | |
694 | return 0; | |
695 | } |