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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 | ||
7a14ce1d IM |
51 | /* |
52 | * Do a quick check without holding xtime_lock: | |
53 | */ | |
54 | delta = ktime_sub(now, last_jiffies_update); | |
55 | if (delta.tv64 < tick_period.tv64) | |
56 | return; | |
57 | ||
79bf2bb3 TG |
58 | /* Reevalute with xtime_lock held */ |
59 | write_seqlock(&xtime_lock); | |
60 | ||
61 | delta = ktime_sub(now, last_jiffies_update); | |
62 | if (delta.tv64 >= tick_period.tv64) { | |
63 | ||
64 | delta = ktime_sub(delta, tick_period); | |
65 | last_jiffies_update = ktime_add(last_jiffies_update, | |
66 | tick_period); | |
67 | ||
68 | /* Slow path for long timeouts */ | |
69 | if (unlikely(delta.tv64 >= tick_period.tv64)) { | |
70 | s64 incr = ktime_to_ns(tick_period); | |
71 | ||
72 | ticks = ktime_divns(delta, incr); | |
73 | ||
74 | last_jiffies_update = ktime_add_ns(last_jiffies_update, | |
75 | incr * ticks); | |
76 | } | |
77 | do_timer(++ticks); | |
78 | } | |
79 | write_sequnlock(&xtime_lock); | |
80 | } | |
81 | ||
82 | /* | |
83 | * Initialize and return retrieve the jiffies update. | |
84 | */ | |
85 | static ktime_t tick_init_jiffy_update(void) | |
86 | { | |
87 | ktime_t period; | |
88 | ||
89 | write_seqlock(&xtime_lock); | |
90 | /* Did we start the jiffies update yet ? */ | |
91 | if (last_jiffies_update.tv64 == 0) | |
92 | last_jiffies_update = tick_next_period; | |
93 | period = last_jiffies_update; | |
94 | write_sequnlock(&xtime_lock); | |
95 | return period; | |
96 | } | |
97 | ||
98 | /* | |
99 | * NOHZ - aka dynamic tick functionality | |
100 | */ | |
101 | #ifdef CONFIG_NO_HZ | |
102 | /* | |
103 | * NO HZ enabled ? | |
104 | */ | |
105 | static int tick_nohz_enabled __read_mostly = 1; | |
106 | ||
107 | /* | |
108 | * Enable / Disable tickless mode | |
109 | */ | |
110 | static int __init setup_tick_nohz(char *str) | |
111 | { | |
112 | if (!strcmp(str, "off")) | |
113 | tick_nohz_enabled = 0; | |
114 | else if (!strcmp(str, "on")) | |
115 | tick_nohz_enabled = 1; | |
116 | else | |
117 | return 0; | |
118 | return 1; | |
119 | } | |
120 | ||
121 | __setup("nohz=", setup_tick_nohz); | |
122 | ||
123 | /** | |
124 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
125 | * | |
126 | * Called from interrupt entry when the CPU was idle | |
127 | * | |
128 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
129 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
130 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
131 | * cpu, which has the update task assigned is in a long sleep. | |
132 | */ | |
133 | void tick_nohz_update_jiffies(void) | |
134 | { | |
135 | int cpu = smp_processor_id(); | |
136 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
137 | unsigned long flags; | |
138 | ktime_t now; | |
139 | ||
140 | if (!ts->tick_stopped) | |
141 | return; | |
142 | ||
143 | cpu_clear(cpu, nohz_cpu_mask); | |
144 | now = ktime_get(); | |
5df7fa1c | 145 | ts->idle_waketime = now; |
79bf2bb3 TG |
146 | |
147 | local_irq_save(flags); | |
148 | tick_do_update_jiffies64(now); | |
149 | local_irq_restore(flags); | |
02ff3755 IM |
150 | |
151 | touch_softlockup_watchdog(); | |
79bf2bb3 TG |
152 | } |
153 | ||
6378ddb5 VP |
154 | void tick_nohz_stop_idle(int cpu) |
155 | { | |
156 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
157 | ||
158 | if (ts->idle_active) { | |
159 | ktime_t now, delta; | |
160 | now = ktime_get(); | |
161 | delta = ktime_sub(now, ts->idle_entrytime); | |
162 | ts->idle_lastupdate = now; | |
163 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
164 | ts->idle_active = 0; | |
56c7426b PZ |
165 | |
166 | sched_clock_idle_wakeup_event(0); | |
6378ddb5 VP |
167 | } |
168 | } | |
169 | ||
903b8a8d | 170 | static ktime_t tick_nohz_start_idle(struct tick_sched *ts) |
6378ddb5 | 171 | { |
6378ddb5 VP |
172 | ktime_t now, delta; |
173 | ||
174 | now = ktime_get(); | |
175 | if (ts->idle_active) { | |
176 | delta = ktime_sub(now, ts->idle_entrytime); | |
177 | ts->idle_lastupdate = now; | |
178 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
179 | } | |
180 | ts->idle_entrytime = now; | |
181 | ts->idle_active = 1; | |
56c7426b | 182 | sched_clock_idle_sleep_event(); |
6378ddb5 VP |
183 | return now; |
184 | } | |
185 | ||
186 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) | |
187 | { | |
188 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
189 | ||
190 | *last_update_time = ktime_to_us(ts->idle_lastupdate); | |
191 | return ktime_to_us(ts->idle_sleeptime); | |
192 | } | |
193 | ||
79bf2bb3 TG |
194 | /** |
195 | * tick_nohz_stop_sched_tick - stop the idle tick from the idle task | |
196 | * | |
197 | * When the next event is more than a tick into the future, stop the idle tick | |
198 | * Called either from the idle loop or from irq_exit() when an idle period was | |
199 | * just interrupted by an interrupt which did not cause a reschedule. | |
200 | */ | |
b8f8c3cf | 201 | void tick_nohz_stop_sched_tick(int inidle) |
79bf2bb3 TG |
202 | { |
203 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; | |
204 | struct tick_sched *ts; | |
6378ddb5 | 205 | ktime_t last_update, expires, now; |
4f86d3a8 | 206 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
79bf2bb3 TG |
207 | int cpu; |
208 | ||
209 | local_irq_save(flags); | |
210 | ||
211 | cpu = smp_processor_id(); | |
212 | ts = &per_cpu(tick_cpu_sched, cpu); | |
903b8a8d | 213 | now = tick_nohz_start_idle(ts); |
79bf2bb3 | 214 | |
5e41d0d6 TG |
215 | /* |
216 | * If this cpu is offline and it is the one which updates | |
217 | * jiffies, then give up the assignment and let it be taken by | |
218 | * the cpu which runs the tick timer next. If we don't drop | |
219 | * this here the jiffies might be stale and do_timer() never | |
220 | * invoked. | |
221 | */ | |
222 | if (unlikely(!cpu_online(cpu))) { | |
223 | if (cpu == tick_do_timer_cpu) | |
6441402b | 224 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
5e41d0d6 TG |
225 | } |
226 | ||
79bf2bb3 TG |
227 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
228 | goto end; | |
229 | ||
b8f8c3cf TG |
230 | if (!inidle && !ts->inidle) |
231 | goto end; | |
232 | ||
233 | ts->inidle = 1; | |
234 | ||
79bf2bb3 TG |
235 | if (need_resched()) |
236 | goto end; | |
237 | ||
35282316 TG |
238 | if (unlikely(local_softirq_pending())) { |
239 | static int ratelimit; | |
240 | ||
241 | if (ratelimit < 10) { | |
242 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", | |
243 | local_softirq_pending()); | |
244 | ratelimit++; | |
245 | } | |
857f3fd7 | 246 | goto end; |
35282316 | 247 | } |
79bf2bb3 | 248 | |
79bf2bb3 | 249 | ts->idle_calls++; |
79bf2bb3 TG |
250 | /* Read jiffies and the time when jiffies were updated last */ |
251 | do { | |
252 | seq = read_seqbegin(&xtime_lock); | |
253 | last_update = last_jiffies_update; | |
254 | last_jiffies = jiffies; | |
255 | } while (read_seqretry(&xtime_lock, seq)); | |
256 | ||
257 | /* Get the next timer wheel timer */ | |
258 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
259 | delta_jiffies = next_jiffies - last_jiffies; | |
260 | ||
6ba9b346 IM |
261 | if (rcu_needs_cpu(cpu)) |
262 | delta_jiffies = 1; | |
79bf2bb3 TG |
263 | /* |
264 | * Do not stop the tick, if we are only one off | |
265 | * or if the cpu is required for rcu | |
266 | */ | |
6ba9b346 | 267 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
268 | goto out; |
269 | ||
270 | /* Schedule the tick, if we are at least one jiffie off */ | |
271 | if ((long)delta_jiffies >= 1) { | |
272 | ||
6ba9b346 | 273 | if (delta_jiffies > 1) |
79bf2bb3 TG |
274 | cpu_set(cpu, nohz_cpu_mask); |
275 | /* | |
276 | * nohz_stop_sched_tick can be called several times before | |
277 | * the nohz_restart_sched_tick is called. This happens when | |
278 | * interrupts arrive which do not cause a reschedule. In the | |
279 | * first call we save the current tick time, so we can restart | |
280 | * the scheduler tick in nohz_restart_sched_tick. | |
281 | */ | |
282 | if (!ts->tick_stopped) { | |
46cb4b7c SS |
283 | if (select_nohz_load_balancer(1)) { |
284 | /* | |
285 | * sched tick not stopped! | |
286 | */ | |
287 | cpu_clear(cpu, nohz_cpu_mask); | |
288 | goto out; | |
289 | } | |
290 | ||
79bf2bb3 TG |
291 | ts->idle_tick = ts->sched_timer.expires; |
292 | ts->tick_stopped = 1; | |
293 | ts->idle_jiffies = last_jiffies; | |
2232c2d8 | 294 | rcu_enter_nohz(); |
79bf2bb3 | 295 | } |
d3ed7824 TG |
296 | |
297 | /* | |
298 | * If this cpu is the one which updates jiffies, then | |
299 | * give up the assignment and let it be taken by the | |
300 | * cpu which runs the tick timer next, which might be | |
301 | * this cpu as well. If we don't drop this here the | |
302 | * jiffies might be stale and do_timer() never | |
303 | * invoked. | |
304 | */ | |
305 | if (cpu == tick_do_timer_cpu) | |
6441402b | 306 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
d3ed7824 | 307 | |
eaad084b TG |
308 | ts->idle_sleeps++; |
309 | ||
310 | /* | |
311 | * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that | |
312 | * there is no timer pending or at least extremly far | |
313 | * into the future (12 days for HZ=1000). In this case | |
314 | * we simply stop the tick timer: | |
315 | */ | |
316 | if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) { | |
317 | ts->idle_expires.tv64 = KTIME_MAX; | |
318 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) | |
319 | hrtimer_cancel(&ts->sched_timer); | |
320 | goto out; | |
321 | } | |
322 | ||
79bf2bb3 TG |
323 | /* |
324 | * calculate the expiry time for the next timer wheel | |
325 | * timer | |
326 | */ | |
327 | expires = ktime_add_ns(last_update, tick_period.tv64 * | |
328 | delta_jiffies); | |
329 | ts->idle_expires = expires; | |
79bf2bb3 TG |
330 | |
331 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
332 | hrtimer_start(&ts->sched_timer, expires, | |
333 | HRTIMER_MODE_ABS); | |
334 | /* Check, if the timer was already in the past */ | |
335 | if (hrtimer_active(&ts->sched_timer)) | |
336 | goto out; | |
4c9dc641 | 337 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
338 | goto out; |
339 | /* | |
340 | * We are past the event already. So we crossed a | |
341 | * jiffie boundary. Update jiffies and raise the | |
342 | * softirq. | |
343 | */ | |
344 | tick_do_update_jiffies64(ktime_get()); | |
345 | cpu_clear(cpu, nohz_cpu_mask); | |
346 | } | |
347 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
348 | out: | |
349 | ts->next_jiffies = next_jiffies; | |
350 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 351 | ts->sleep_length = ktime_sub(dev->next_event, now); |
79bf2bb3 TG |
352 | end: |
353 | local_irq_restore(flags); | |
354 | } | |
355 | ||
4f86d3a8 LB |
356 | /** |
357 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
358 | * | |
359 | * Called from power state control code with interrupts disabled | |
360 | */ | |
361 | ktime_t tick_nohz_get_sleep_length(void) | |
362 | { | |
363 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
364 | ||
365 | return ts->sleep_length; | |
366 | } | |
367 | ||
79bf2bb3 | 368 | /** |
8dce39c2 | 369 | * tick_nohz_restart_sched_tick - restart the idle tick from the idle task |
79bf2bb3 TG |
370 | * |
371 | * Restart the idle tick when the CPU is woken up from idle | |
372 | */ | |
373 | void tick_nohz_restart_sched_tick(void) | |
374 | { | |
375 | int cpu = smp_processor_id(); | |
376 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
377 | unsigned long ticks; | |
6378ddb5 | 378 | ktime_t now; |
79bf2bb3 | 379 | |
6378ddb5 VP |
380 | local_irq_disable(); |
381 | tick_nohz_stop_idle(cpu); | |
382 | ||
b8f8c3cf TG |
383 | if (!ts->inidle || !ts->tick_stopped) { |
384 | ts->inidle = 0; | |
6378ddb5 | 385 | local_irq_enable(); |
79bf2bb3 | 386 | return; |
6378ddb5 | 387 | } |
79bf2bb3 | 388 | |
b8f8c3cf TG |
389 | ts->inidle = 0; |
390 | ||
2232c2d8 SR |
391 | rcu_exit_nohz(); |
392 | ||
79bf2bb3 | 393 | /* Update jiffies first */ |
46cb4b7c | 394 | select_nohz_load_balancer(0); |
6378ddb5 | 395 | now = ktime_get(); |
79bf2bb3 TG |
396 | tick_do_update_jiffies64(now); |
397 | cpu_clear(cpu, nohz_cpu_mask); | |
398 | ||
79bf2bb3 TG |
399 | /* |
400 | * We stopped the tick in idle. Update process times would miss the | |
401 | * time we slept as update_process_times does only a 1 tick | |
402 | * accounting. Enforce that this is accounted to idle ! | |
403 | */ | |
404 | ticks = jiffies - ts->idle_jiffies; | |
405 | /* | |
406 | * We might be one off. Do not randomly account a huge number of ticks! | |
407 | */ | |
408 | if (ticks && ticks < LONG_MAX) { | |
409 | add_preempt_count(HARDIRQ_OFFSET); | |
410 | account_system_time(current, HARDIRQ_OFFSET, | |
411 | jiffies_to_cputime(ticks)); | |
412 | sub_preempt_count(HARDIRQ_OFFSET); | |
413 | } | |
414 | ||
126e01bf | 415 | touch_softlockup_watchdog(); |
79bf2bb3 TG |
416 | /* |
417 | * Cancel the scheduled timer and restore the tick | |
418 | */ | |
419 | ts->tick_stopped = 0; | |
5df7fa1c | 420 | ts->idle_exittime = now; |
79bf2bb3 TG |
421 | hrtimer_cancel(&ts->sched_timer); |
422 | ts->sched_timer.expires = ts->idle_tick; | |
423 | ||
424 | while (1) { | |
425 | /* Forward the time to expire in the future */ | |
426 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
427 | ||
428 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
429 | hrtimer_start(&ts->sched_timer, | |
430 | ts->sched_timer.expires, | |
431 | HRTIMER_MODE_ABS); | |
432 | /* Check, if the timer was already in the past */ | |
433 | if (hrtimer_active(&ts->sched_timer)) | |
434 | break; | |
435 | } else { | |
436 | if (!tick_program_event(ts->sched_timer.expires, 0)) | |
437 | break; | |
438 | } | |
439 | /* Update jiffies and reread time */ | |
440 | tick_do_update_jiffies64(now); | |
441 | now = ktime_get(); | |
442 | } | |
443 | local_irq_enable(); | |
444 | } | |
445 | ||
446 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
447 | { | |
448 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
449 | return tick_program_event(ts->sched_timer.expires, 0); | |
450 | } | |
451 | ||
452 | /* | |
453 | * The nohz low res interrupt handler | |
454 | */ | |
455 | static void tick_nohz_handler(struct clock_event_device *dev) | |
456 | { | |
457 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
458 | struct pt_regs *regs = get_irq_regs(); | |
d3ed7824 | 459 | int cpu = smp_processor_id(); |
79bf2bb3 TG |
460 | ktime_t now = ktime_get(); |
461 | ||
462 | dev->next_event.tv64 = KTIME_MAX; | |
463 | ||
d3ed7824 TG |
464 | /* |
465 | * Check if the do_timer duty was dropped. We don't care about | |
466 | * concurrency: This happens only when the cpu in charge went | |
467 | * into a long sleep. If two cpus happen to assign themself to | |
468 | * this duty, then the jiffies update is still serialized by | |
469 | * xtime_lock. | |
470 | */ | |
6441402b | 471 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
472 | tick_do_timer_cpu = cpu; |
473 | ||
79bf2bb3 | 474 | /* Check, if the jiffies need an update */ |
d3ed7824 TG |
475 | if (tick_do_timer_cpu == cpu) |
476 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
477 | |
478 | /* | |
479 | * When we are idle and the tick is stopped, we have to touch | |
480 | * the watchdog as we might not schedule for a really long | |
481 | * time. This happens on complete idle SMP systems while | |
482 | * waiting on the login prompt. We also increment the "start | |
483 | * of idle" jiffy stamp so the idle accounting adjustment we | |
484 | * do when we go busy again does not account too much ticks. | |
485 | */ | |
486 | if (ts->tick_stopped) { | |
487 | touch_softlockup_watchdog(); | |
488 | ts->idle_jiffies++; | |
489 | } | |
490 | ||
491 | update_process_times(user_mode(regs)); | |
492 | profile_tick(CPU_PROFILING); | |
493 | ||
494 | /* Do not restart, when we are in the idle loop */ | |
495 | if (ts->tick_stopped) | |
496 | return; | |
497 | ||
498 | while (tick_nohz_reprogram(ts, now)) { | |
499 | now = ktime_get(); | |
500 | tick_do_update_jiffies64(now); | |
501 | } | |
502 | } | |
503 | ||
504 | /** | |
505 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
506 | */ | |
507 | static void tick_nohz_switch_to_nohz(void) | |
508 | { | |
509 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
510 | ktime_t next; | |
511 | ||
512 | if (!tick_nohz_enabled) | |
513 | return; | |
514 | ||
515 | local_irq_disable(); | |
516 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
517 | local_irq_enable(); | |
518 | return; | |
519 | } | |
520 | ||
521 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
522 | ||
523 | /* | |
524 | * Recycle the hrtimer in ts, so we can share the | |
525 | * hrtimer_forward with the highres code. | |
526 | */ | |
527 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
528 | /* Get the next period */ | |
529 | next = tick_init_jiffy_update(); | |
530 | ||
531 | for (;;) { | |
532 | ts->sched_timer.expires = next; | |
533 | if (!tick_program_event(next, 0)) | |
534 | break; | |
535 | next = ktime_add(next, tick_period); | |
536 | } | |
537 | local_irq_enable(); | |
538 | ||
539 | printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", | |
540 | smp_processor_id()); | |
541 | } | |
542 | ||
543 | #else | |
544 | ||
545 | static inline void tick_nohz_switch_to_nohz(void) { } | |
546 | ||
547 | #endif /* NO_HZ */ | |
548 | ||
549 | /* | |
550 | * High resolution timer specific code | |
551 | */ | |
552 | #ifdef CONFIG_HIGH_RES_TIMERS | |
553 | /* | |
4c9dc641 | 554 | * We rearm the timer until we get disabled by the idle code. |
79bf2bb3 TG |
555 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
556 | */ | |
557 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
558 | { | |
559 | struct tick_sched *ts = | |
560 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
561 | struct pt_regs *regs = get_irq_regs(); |
562 | ktime_t now = ktime_get(); | |
d3ed7824 TG |
563 | int cpu = smp_processor_id(); |
564 | ||
565 | #ifdef CONFIG_NO_HZ | |
566 | /* | |
567 | * Check if the do_timer duty was dropped. We don't care about | |
568 | * concurrency: This happens only when the cpu in charge went | |
569 | * into a long sleep. If two cpus happen to assign themself to | |
570 | * this duty, then the jiffies update is still serialized by | |
571 | * xtime_lock. | |
572 | */ | |
6441402b | 573 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
574 | tick_do_timer_cpu = cpu; |
575 | #endif | |
79bf2bb3 TG |
576 | |
577 | /* Check, if the jiffies need an update */ | |
d3ed7824 TG |
578 | if (tick_do_timer_cpu == cpu) |
579 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
580 | |
581 | /* | |
582 | * Do not call, when we are not in irq context and have | |
583 | * no valid regs pointer | |
584 | */ | |
585 | if (regs) { | |
586 | /* | |
587 | * When we are idle and the tick is stopped, we have to touch | |
588 | * the watchdog as we might not schedule for a really long | |
589 | * time. This happens on complete idle SMP systems while | |
590 | * waiting on the login prompt. We also increment the "start of | |
591 | * idle" jiffy stamp so the idle accounting adjustment we do | |
592 | * when we go busy again does not account too much ticks. | |
593 | */ | |
594 | if (ts->tick_stopped) { | |
595 | touch_softlockup_watchdog(); | |
596 | ts->idle_jiffies++; | |
597 | } | |
79bf2bb3 TG |
598 | update_process_times(user_mode(regs)); |
599 | profile_tick(CPU_PROFILING); | |
79bf2bb3 TG |
600 | } |
601 | ||
602 | /* Do not restart, when we are in the idle loop */ | |
603 | if (ts->tick_stopped) | |
604 | return HRTIMER_NORESTART; | |
605 | ||
606 | hrtimer_forward(timer, now, tick_period); | |
607 | ||
608 | return HRTIMER_RESTART; | |
609 | } | |
610 | ||
611 | /** | |
612 | * tick_setup_sched_timer - setup the tick emulation timer | |
613 | */ | |
614 | void tick_setup_sched_timer(void) | |
615 | { | |
616 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
617 | ktime_t now = ktime_get(); | |
3704540b | 618 | u64 offset; |
79bf2bb3 TG |
619 | |
620 | /* | |
621 | * Emulate tick processing via per-CPU hrtimers: | |
622 | */ | |
623 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
624 | ts->sched_timer.function = tick_sched_timer; | |
625 | ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ; | |
626 | ||
3704540b | 627 | /* Get the next period (per cpu) */ |
79bf2bb3 | 628 | ts->sched_timer.expires = tick_init_jiffy_update(); |
3704540b | 629 | offset = ktime_to_ns(tick_period) >> 1; |
b2d9323d | 630 | do_div(offset, num_possible_cpus()); |
3704540b JS |
631 | offset *= smp_processor_id(); |
632 | ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset); | |
79bf2bb3 TG |
633 | |
634 | for (;;) { | |
635 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
636 | hrtimer_start(&ts->sched_timer, ts->sched_timer.expires, | |
637 | HRTIMER_MODE_ABS); | |
638 | /* Check, if the timer was already in the past */ | |
639 | if (hrtimer_active(&ts->sched_timer)) | |
640 | break; | |
641 | now = ktime_get(); | |
642 | } | |
643 | ||
644 | #ifdef CONFIG_NO_HZ | |
645 | if (tick_nohz_enabled) | |
646 | ts->nohz_mode = NOHZ_MODE_HIGHRES; | |
647 | #endif | |
648 | } | |
3c4fbe5e | 649 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 650 | |
3c4fbe5e | 651 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
652 | void tick_cancel_sched_timer(int cpu) |
653 | { | |
654 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
655 | ||
3c4fbe5e | 656 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
657 | if (ts->sched_timer.base) |
658 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 659 | # endif |
a7901766 | 660 | |
79bf2bb3 TG |
661 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
662 | } | |
3c4fbe5e | 663 | #endif |
79bf2bb3 TG |
664 | |
665 | /** | |
666 | * Async notification about clocksource changes | |
667 | */ | |
668 | void tick_clock_notify(void) | |
669 | { | |
670 | int cpu; | |
671 | ||
672 | for_each_possible_cpu(cpu) | |
673 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
674 | } | |
675 | ||
676 | /* | |
677 | * Async notification about clock event changes | |
678 | */ | |
679 | void tick_oneshot_notify(void) | |
680 | { | |
681 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
682 | ||
683 | set_bit(0, &ts->check_clocks); | |
684 | } | |
685 | ||
686 | /** | |
687 | * Check, if a change happened, which makes oneshot possible. | |
688 | * | |
689 | * Called cyclic from the hrtimer softirq (driven by the timer | |
690 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
691 | * mode, because high resolution timers are disabled (either compile | |
692 | * or runtime). | |
693 | */ | |
694 | int tick_check_oneshot_change(int allow_nohz) | |
695 | { | |
696 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
697 | ||
698 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
699 | return 0; | |
700 | ||
701 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
702 | return 0; | |
703 | ||
cf4fc6cb | 704 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
705 | return 0; |
706 | ||
707 | if (!allow_nohz) | |
708 | return 1; | |
709 | ||
710 | tick_nohz_switch_to_nohz(); | |
711 | return 0; | |
712 | } |