Commit | Line | Data |
---|---|---|
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> | |
8083e4ad | 22 | #include <linux/module.h> |
79bf2bb3 | 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); | |
49d670fb TG |
78 | |
79 | /* Keep the tick_next_period variable up to date */ | |
80 | tick_next_period = ktime_add(last_jiffies_update, tick_period); | |
79bf2bb3 TG |
81 | } |
82 | write_sequnlock(&xtime_lock); | |
83 | } | |
84 | ||
85 | /* | |
86 | * Initialize and return retrieve the jiffies update. | |
87 | */ | |
88 | static ktime_t tick_init_jiffy_update(void) | |
89 | { | |
90 | ktime_t period; | |
91 | ||
92 | write_seqlock(&xtime_lock); | |
93 | /* Did we start the jiffies update yet ? */ | |
94 | if (last_jiffies_update.tv64 == 0) | |
95 | last_jiffies_update = tick_next_period; | |
96 | period = last_jiffies_update; | |
97 | write_sequnlock(&xtime_lock); | |
98 | return period; | |
99 | } | |
100 | ||
101 | /* | |
102 | * NOHZ - aka dynamic tick functionality | |
103 | */ | |
104 | #ifdef CONFIG_NO_HZ | |
105 | /* | |
106 | * NO HZ enabled ? | |
107 | */ | |
9d2ad243 | 108 | int tick_nohz_enabled __read_mostly = 1; |
79bf2bb3 TG |
109 | |
110 | /* | |
111 | * Enable / Disable tickless mode | |
112 | */ | |
113 | static int __init setup_tick_nohz(char *str) | |
114 | { | |
115 | if (!strcmp(str, "off")) | |
116 | tick_nohz_enabled = 0; | |
117 | else if (!strcmp(str, "on")) | |
118 | tick_nohz_enabled = 1; | |
119 | else | |
120 | return 0; | |
121 | return 1; | |
122 | } | |
123 | ||
124 | __setup("nohz=", setup_tick_nohz); | |
125 | ||
126 | /** | |
127 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
128 | * | |
129 | * Called from interrupt entry when the CPU was idle | |
130 | * | |
131 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
132 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
133 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
134 | * cpu, which has the update task assigned is in a long sleep. | |
135 | */ | |
eed3b9cf | 136 | static void tick_nohz_update_jiffies(ktime_t now) |
79bf2bb3 TG |
137 | { |
138 | int cpu = smp_processor_id(); | |
139 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
140 | unsigned long flags; | |
79bf2bb3 | 141 | |
5df7fa1c | 142 | ts->idle_waketime = now; |
79bf2bb3 TG |
143 | |
144 | local_irq_save(flags); | |
145 | tick_do_update_jiffies64(now); | |
146 | local_irq_restore(flags); | |
02ff3755 IM |
147 | |
148 | touch_softlockup_watchdog(); | |
79bf2bb3 TG |
149 | } |
150 | ||
595aac48 AV |
151 | /* |
152 | * Updates the per cpu time idle statistics counters | |
153 | */ | |
8d63bf94 | 154 | static void |
8c215bd3 | 155 | update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
6378ddb5 | 156 | { |
eed3b9cf | 157 | ktime_t delta; |
6378ddb5 | 158 | |
595aac48 AV |
159 | if (ts->idle_active) { |
160 | delta = ktime_sub(now, ts->idle_entrytime); | |
8c215bd3 | 161 | if (nr_iowait_cpu(cpu) > 0) |
0224cf4c | 162 | ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
6beea0cd MH |
163 | else |
164 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
8c7b09f4 | 165 | ts->idle_entrytime = now; |
595aac48 | 166 | } |
8d63bf94 | 167 | |
e0e37c20 | 168 | if (last_update_time) |
8d63bf94 AV |
169 | *last_update_time = ktime_to_us(now); |
170 | ||
595aac48 AV |
171 | } |
172 | ||
173 | static void tick_nohz_stop_idle(int cpu, ktime_t now) | |
174 | { | |
175 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
176 | ||
8c215bd3 | 177 | update_ts_time_stats(cpu, ts, now, NULL); |
eed3b9cf | 178 | ts->idle_active = 0; |
56c7426b | 179 | |
eed3b9cf | 180 | sched_clock_idle_wakeup_event(0); |
6378ddb5 VP |
181 | } |
182 | ||
8c215bd3 | 183 | static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) |
6378ddb5 | 184 | { |
430ee881 | 185 | ktime_t now = ktime_get(); |
595aac48 | 186 | |
6378ddb5 VP |
187 | ts->idle_entrytime = now; |
188 | ts->idle_active = 1; | |
56c7426b | 189 | sched_clock_idle_sleep_event(); |
6378ddb5 VP |
190 | return now; |
191 | } | |
192 | ||
b1f724c3 AV |
193 | /** |
194 | * get_cpu_idle_time_us - get the total idle time of a cpu | |
195 | * @cpu: CPU number to query | |
09a1d34f MH |
196 | * @last_update_time: variable to store update time in. Do not update |
197 | * counters if NULL. | |
b1f724c3 AV |
198 | * |
199 | * Return the cummulative idle time (since boot) for a given | |
6beea0cd | 200 | * CPU, in microseconds. |
b1f724c3 AV |
201 | * |
202 | * This time is measured via accounting rather than sampling, | |
203 | * and is as accurate as ktime_get() is. | |
204 | * | |
205 | * This function returns -1 if NOHZ is not enabled. | |
206 | */ | |
6378ddb5 VP |
207 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
208 | { | |
209 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 210 | ktime_t now, idle; |
6378ddb5 | 211 | |
8083e4ad | 212 | if (!tick_nohz_enabled) |
213 | return -1; | |
214 | ||
09a1d34f MH |
215 | now = ktime_get(); |
216 | if (last_update_time) { | |
217 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
218 | idle = ts->idle_sleeptime; | |
219 | } else { | |
220 | if (ts->idle_active && !nr_iowait_cpu(cpu)) { | |
221 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
222 | ||
223 | idle = ktime_add(ts->idle_sleeptime, delta); | |
224 | } else { | |
225 | idle = ts->idle_sleeptime; | |
226 | } | |
227 | } | |
228 | ||
229 | return ktime_to_us(idle); | |
8083e4ad | 230 | |
6378ddb5 | 231 | } |
8083e4ad | 232 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
6378ddb5 | 233 | |
6beea0cd | 234 | /** |
0224cf4c AV |
235 | * get_cpu_iowait_time_us - get the total iowait time of a cpu |
236 | * @cpu: CPU number to query | |
09a1d34f MH |
237 | * @last_update_time: variable to store update time in. Do not update |
238 | * counters if NULL. | |
0224cf4c AV |
239 | * |
240 | * Return the cummulative iowait time (since boot) for a given | |
241 | * CPU, in microseconds. | |
242 | * | |
243 | * This time is measured via accounting rather than sampling, | |
244 | * and is as accurate as ktime_get() is. | |
245 | * | |
246 | * This function returns -1 if NOHZ is not enabled. | |
247 | */ | |
248 | u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) | |
249 | { | |
250 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 251 | ktime_t now, iowait; |
0224cf4c AV |
252 | |
253 | if (!tick_nohz_enabled) | |
254 | return -1; | |
255 | ||
09a1d34f MH |
256 | now = ktime_get(); |
257 | if (last_update_time) { | |
258 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
259 | iowait = ts->iowait_sleeptime; | |
260 | } else { | |
261 | if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { | |
262 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
0224cf4c | 263 | |
09a1d34f MH |
264 | iowait = ktime_add(ts->iowait_sleeptime, delta); |
265 | } else { | |
266 | iowait = ts->iowait_sleeptime; | |
267 | } | |
268 | } | |
0224cf4c | 269 | |
09a1d34f | 270 | return ktime_to_us(iowait); |
0224cf4c AV |
271 | } |
272 | EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); | |
273 | ||
84bf1bcc FW |
274 | static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, |
275 | ktime_t now, int cpu) | |
79bf2bb3 | 276 | { |
280f0677 | 277 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies; |
84bf1bcc | 278 | ktime_t last_update, expires, ret = { .tv64 = 0 }; |
aa9b1630 | 279 | unsigned long rcu_delta_jiffies; |
4f86d3a8 | 280 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
98962465 | 281 | u64 time_delta; |
79bf2bb3 | 282 | |
79bf2bb3 TG |
283 | /* Read jiffies and the time when jiffies were updated last */ |
284 | do { | |
285 | seq = read_seqbegin(&xtime_lock); | |
286 | last_update = last_jiffies_update; | |
287 | last_jiffies = jiffies; | |
27185016 | 288 | time_delta = timekeeping_max_deferment(); |
79bf2bb3 TG |
289 | } while (read_seqretry(&xtime_lock, seq)); |
290 | ||
aa9b1630 | 291 | if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) || |
396e894d | 292 | arch_needs_cpu(cpu)) { |
3c5d92a0 | 293 | next_jiffies = last_jiffies + 1; |
6ba9b346 | 294 | delta_jiffies = 1; |
3c5d92a0 MS |
295 | } else { |
296 | /* Get the next timer wheel timer */ | |
297 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
298 | delta_jiffies = next_jiffies - last_jiffies; | |
aa9b1630 PM |
299 | if (rcu_delta_jiffies < delta_jiffies) { |
300 | next_jiffies = last_jiffies + rcu_delta_jiffies; | |
301 | delta_jiffies = rcu_delta_jiffies; | |
302 | } | |
3c5d92a0 | 303 | } |
79bf2bb3 TG |
304 | /* |
305 | * Do not stop the tick, if we are only one off | |
306 | * or if the cpu is required for rcu | |
307 | */ | |
6ba9b346 | 308 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
309 | goto out; |
310 | ||
311 | /* Schedule the tick, if we are at least one jiffie off */ | |
312 | if ((long)delta_jiffies >= 1) { | |
313 | ||
00147449 WR |
314 | /* |
315 | * If this cpu is the one which updates jiffies, then | |
316 | * give up the assignment and let it be taken by the | |
317 | * cpu which runs the tick timer next, which might be | |
318 | * this cpu as well. If we don't drop this here the | |
319 | * jiffies might be stale and do_timer() never | |
27185016 TG |
320 | * invoked. Keep track of the fact that it was the one |
321 | * which had the do_timer() duty last. If this cpu is | |
322 | * the one which had the do_timer() duty last, we | |
323 | * limit the sleep time to the timekeeping | |
324 | * max_deferement value which we retrieved | |
325 | * above. Otherwise we can sleep as long as we want. | |
00147449 | 326 | */ |
27185016 | 327 | if (cpu == tick_do_timer_cpu) { |
00147449 | 328 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
27185016 TG |
329 | ts->do_timer_last = 1; |
330 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { | |
331 | time_delta = KTIME_MAX; | |
332 | ts->do_timer_last = 0; | |
333 | } else if (!ts->do_timer_last) { | |
334 | time_delta = KTIME_MAX; | |
335 | } | |
336 | ||
00147449 | 337 | /* |
98962465 JH |
338 | * calculate the expiry time for the next timer wheel |
339 | * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals | |
340 | * that there is no timer pending or at least extremely | |
341 | * far into the future (12 days for HZ=1000). In this | |
342 | * case we set the expiry to the end of time. | |
343 | */ | |
344 | if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) { | |
345 | /* | |
346 | * Calculate the time delta for the next timer event. | |
347 | * If the time delta exceeds the maximum time delta | |
348 | * permitted by the current clocksource then adjust | |
349 | * the time delta accordingly to ensure the | |
350 | * clocksource does not wrap. | |
351 | */ | |
352 | time_delta = min_t(u64, time_delta, | |
353 | tick_period.tv64 * delta_jiffies); | |
98962465 | 354 | } |
00147449 | 355 | |
27185016 TG |
356 | if (time_delta < KTIME_MAX) |
357 | expires = ktime_add_ns(last_update, time_delta); | |
358 | else | |
359 | expires.tv64 = KTIME_MAX; | |
00147449 | 360 | |
00147449 WR |
361 | /* Skip reprogram of event if its not changed */ |
362 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) | |
363 | goto out; | |
364 | ||
84bf1bcc FW |
365 | ret = expires; |
366 | ||
79bf2bb3 TG |
367 | /* |
368 | * nohz_stop_sched_tick can be called several times before | |
369 | * the nohz_restart_sched_tick is called. This happens when | |
370 | * interrupts arrive which do not cause a reschedule. In the | |
371 | * first call we save the current tick time, so we can restart | |
372 | * the scheduler tick in nohz_restart_sched_tick. | |
373 | */ | |
374 | if (!ts->tick_stopped) { | |
c1cc017c | 375 | nohz_balance_enter_idle(cpu); |
5167e8d5 | 376 | calc_load_enter_idle(); |
46cb4b7c | 377 | |
f5d411c9 | 378 | ts->last_tick = hrtimer_get_expires(&ts->sched_timer); |
79bf2bb3 | 379 | ts->tick_stopped = 1; |
79bf2bb3 | 380 | } |
d3ed7824 | 381 | |
eaad084b | 382 | /* |
98962465 JH |
383 | * If the expiration time == KTIME_MAX, then |
384 | * in this case we simply stop the tick timer. | |
eaad084b | 385 | */ |
98962465 | 386 | if (unlikely(expires.tv64 == KTIME_MAX)) { |
eaad084b TG |
387 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
388 | hrtimer_cancel(&ts->sched_timer); | |
389 | goto out; | |
390 | } | |
391 | ||
79bf2bb3 TG |
392 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
393 | hrtimer_start(&ts->sched_timer, expires, | |
5c333864 | 394 | HRTIMER_MODE_ABS_PINNED); |
79bf2bb3 TG |
395 | /* Check, if the timer was already in the past */ |
396 | if (hrtimer_active(&ts->sched_timer)) | |
397 | goto out; | |
4c9dc641 | 398 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
399 | goto out; |
400 | /* | |
401 | * We are past the event already. So we crossed a | |
402 | * jiffie boundary. Update jiffies and raise the | |
403 | * softirq. | |
404 | */ | |
405 | tick_do_update_jiffies64(ktime_get()); | |
79bf2bb3 TG |
406 | } |
407 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
408 | out: | |
409 | ts->next_jiffies = next_jiffies; | |
410 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 411 | ts->sleep_length = ktime_sub(dev->next_event, now); |
84bf1bcc FW |
412 | |
413 | return ret; | |
280f0677 FW |
414 | } |
415 | ||
5b39939a FW |
416 | static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) |
417 | { | |
418 | /* | |
419 | * If this cpu is offline and it is the one which updates | |
420 | * jiffies, then give up the assignment and let it be taken by | |
421 | * the cpu which runs the tick timer next. If we don't drop | |
422 | * this here the jiffies might be stale and do_timer() never | |
423 | * invoked. | |
424 | */ | |
425 | if (unlikely(!cpu_online(cpu))) { | |
426 | if (cpu == tick_do_timer_cpu) | |
427 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
428 | } | |
429 | ||
430 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) | |
431 | return false; | |
432 | ||
433 | if (need_resched()) | |
434 | return false; | |
435 | ||
436 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { | |
437 | static int ratelimit; | |
438 | ||
803b0eba PM |
439 | if (ratelimit < 10 && |
440 | (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { | |
5b39939a FW |
441 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", |
442 | (unsigned int) local_softirq_pending()); | |
443 | ratelimit++; | |
444 | } | |
445 | return false; | |
446 | } | |
447 | ||
448 | return true; | |
449 | } | |
450 | ||
19f5f736 FW |
451 | static void __tick_nohz_idle_enter(struct tick_sched *ts) |
452 | { | |
84bf1bcc | 453 | ktime_t now, expires; |
5b39939a | 454 | int cpu = smp_processor_id(); |
19f5f736 | 455 | |
5b39939a | 456 | now = tick_nohz_start_idle(cpu, ts); |
2ac0d98f | 457 | |
5b39939a FW |
458 | if (can_stop_idle_tick(cpu, ts)) { |
459 | int was_stopped = ts->tick_stopped; | |
460 | ||
461 | ts->idle_calls++; | |
84bf1bcc FW |
462 | |
463 | expires = tick_nohz_stop_sched_tick(ts, now, cpu); | |
464 | if (expires.tv64 > 0LL) { | |
465 | ts->idle_sleeps++; | |
466 | ts->idle_expires = expires; | |
467 | } | |
5b39939a FW |
468 | |
469 | if (!was_stopped && ts->tick_stopped) | |
470 | ts->idle_jiffies = ts->last_jiffies; | |
471 | } | |
280f0677 FW |
472 | } |
473 | ||
474 | /** | |
475 | * tick_nohz_idle_enter - stop the idle tick from the idle task | |
476 | * | |
477 | * When the next event is more than a tick into the future, stop the idle tick | |
478 | * Called when we start the idle loop. | |
2bbb6817 | 479 | * |
1268fbc7 | 480 | * The arch is responsible of calling: |
2bbb6817 FW |
481 | * |
482 | * - rcu_idle_enter() after its last use of RCU before the CPU is put | |
483 | * to sleep. | |
484 | * - rcu_idle_exit() before the first use of RCU after the CPU is woken up. | |
280f0677 | 485 | */ |
1268fbc7 | 486 | void tick_nohz_idle_enter(void) |
280f0677 FW |
487 | { |
488 | struct tick_sched *ts; | |
489 | ||
1268fbc7 FW |
490 | WARN_ON_ONCE(irqs_disabled()); |
491 | ||
0db49b72 LT |
492 | /* |
493 | * Update the idle state in the scheduler domain hierarchy | |
494 | * when tick_nohz_stop_sched_tick() is called from the idle loop. | |
495 | * State will be updated to busy during the first busy tick after | |
496 | * exiting idle. | |
497 | */ | |
498 | set_cpu_sd_state_idle(); | |
499 | ||
1268fbc7 FW |
500 | local_irq_disable(); |
501 | ||
280f0677 FW |
502 | ts = &__get_cpu_var(tick_cpu_sched); |
503 | /* | |
504 | * set ts->inidle unconditionally. even if the system did not | |
505 | * switch to nohz mode the cpu frequency governers rely on the | |
506 | * update of the idle time accounting in tick_nohz_start_idle(). | |
507 | */ | |
508 | ts->inidle = 1; | |
19f5f736 | 509 | __tick_nohz_idle_enter(ts); |
1268fbc7 FW |
510 | |
511 | local_irq_enable(); | |
280f0677 FW |
512 | } |
513 | ||
514 | /** | |
515 | * tick_nohz_irq_exit - update next tick event from interrupt exit | |
516 | * | |
517 | * When an interrupt fires while we are idle and it doesn't cause | |
518 | * a reschedule, it may still add, modify or delete a timer, enqueue | |
519 | * an RCU callback, etc... | |
520 | * So we need to re-calculate and reprogram the next tick event. | |
521 | */ | |
522 | void tick_nohz_irq_exit(void) | |
523 | { | |
524 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
525 | ||
526 | if (!ts->inidle) | |
527 | return; | |
528 | ||
19f5f736 | 529 | __tick_nohz_idle_enter(ts); |
79bf2bb3 TG |
530 | } |
531 | ||
4f86d3a8 LB |
532 | /** |
533 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
534 | * | |
535 | * Called from power state control code with interrupts disabled | |
536 | */ | |
537 | ktime_t tick_nohz_get_sleep_length(void) | |
538 | { | |
539 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
540 | ||
541 | return ts->sleep_length; | |
542 | } | |
543 | ||
c34bec5a TG |
544 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
545 | { | |
546 | hrtimer_cancel(&ts->sched_timer); | |
f5d411c9 | 547 | hrtimer_set_expires(&ts->sched_timer, ts->last_tick); |
c34bec5a TG |
548 | |
549 | while (1) { | |
550 | /* Forward the time to expire in the future */ | |
551 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
552 | ||
553 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
268a3dcf | 554 | hrtimer_start_expires(&ts->sched_timer, |
5c333864 | 555 | HRTIMER_MODE_ABS_PINNED); |
c34bec5a TG |
556 | /* Check, if the timer was already in the past */ |
557 | if (hrtimer_active(&ts->sched_timer)) | |
558 | break; | |
559 | } else { | |
268a3dcf TG |
560 | if (!tick_program_event( |
561 | hrtimer_get_expires(&ts->sched_timer), 0)) | |
c34bec5a TG |
562 | break; |
563 | } | |
6f103929 | 564 | /* Reread time and update jiffies */ |
c34bec5a | 565 | now = ktime_get(); |
6f103929 | 566 | tick_do_update_jiffies64(now); |
c34bec5a TG |
567 | } |
568 | } | |
569 | ||
19f5f736 | 570 | static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) |
79bf2bb3 | 571 | { |
79bf2bb3 | 572 | /* Update jiffies first */ |
79bf2bb3 | 573 | tick_do_update_jiffies64(now); |
5aaa0b7a | 574 | update_cpu_load_nohz(); |
79bf2bb3 | 575 | |
749c8814 | 576 | calc_load_exit_idle(); |
2ac0d98f FW |
577 | touch_softlockup_watchdog(); |
578 | /* | |
579 | * Cancel the scheduled timer and restore the tick | |
580 | */ | |
581 | ts->tick_stopped = 0; | |
582 | ts->idle_exittime = now; | |
583 | ||
584 | tick_nohz_restart(ts, now); | |
585 | } | |
586 | ||
587 | static void tick_nohz_account_idle_ticks(struct tick_sched *ts) | |
588 | { | |
79741dd3 | 589 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
2ac0d98f | 590 | unsigned long ticks; |
79bf2bb3 TG |
591 | /* |
592 | * We stopped the tick in idle. Update process times would miss the | |
593 | * time we slept as update_process_times does only a 1 tick | |
594 | * accounting. Enforce that this is accounted to idle ! | |
595 | */ | |
596 | ticks = jiffies - ts->idle_jiffies; | |
597 | /* | |
598 | * We might be one off. Do not randomly account a huge number of ticks! | |
599 | */ | |
79741dd3 MS |
600 | if (ticks && ticks < LONG_MAX) |
601 | account_idle_ticks(ticks); | |
602 | #endif | |
19f5f736 FW |
603 | } |
604 | ||
79bf2bb3 | 605 | /** |
280f0677 | 606 | * tick_nohz_idle_exit - restart the idle tick from the idle task |
79bf2bb3 TG |
607 | * |
608 | * Restart the idle tick when the CPU is woken up from idle | |
280f0677 FW |
609 | * This also exit the RCU extended quiescent state. The CPU |
610 | * can use RCU again after this function is called. | |
79bf2bb3 | 611 | */ |
280f0677 | 612 | void tick_nohz_idle_exit(void) |
79bf2bb3 TG |
613 | { |
614 | int cpu = smp_processor_id(); | |
615 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
6378ddb5 | 616 | ktime_t now; |
79bf2bb3 | 617 | |
6378ddb5 | 618 | local_irq_disable(); |
2bbb6817 | 619 | |
15f827be FW |
620 | WARN_ON_ONCE(!ts->inidle); |
621 | ||
622 | ts->inidle = 0; | |
623 | ||
624 | if (ts->idle_active || ts->tick_stopped) | |
eed3b9cf MS |
625 | now = ktime_get(); |
626 | ||
627 | if (ts->idle_active) | |
628 | tick_nohz_stop_idle(cpu, now); | |
6378ddb5 | 629 | |
2ac0d98f | 630 | if (ts->tick_stopped) { |
19f5f736 | 631 | tick_nohz_restart_sched_tick(ts, now); |
2ac0d98f | 632 | tick_nohz_account_idle_ticks(ts); |
6378ddb5 | 633 | } |
79bf2bb3 | 634 | |
79bf2bb3 TG |
635 | local_irq_enable(); |
636 | } | |
637 | ||
638 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
639 | { | |
640 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
cc584b21 | 641 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
79bf2bb3 TG |
642 | } |
643 | ||
644 | /* | |
645 | * The nohz low res interrupt handler | |
646 | */ | |
647 | static void tick_nohz_handler(struct clock_event_device *dev) | |
648 | { | |
649 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
650 | struct pt_regs *regs = get_irq_regs(); | |
d3ed7824 | 651 | int cpu = smp_processor_id(); |
79bf2bb3 TG |
652 | ktime_t now = ktime_get(); |
653 | ||
654 | dev->next_event.tv64 = KTIME_MAX; | |
655 | ||
d3ed7824 TG |
656 | /* |
657 | * Check if the do_timer duty was dropped. We don't care about | |
658 | * concurrency: This happens only when the cpu in charge went | |
659 | * into a long sleep. If two cpus happen to assign themself to | |
660 | * this duty, then the jiffies update is still serialized by | |
661 | * xtime_lock. | |
662 | */ | |
6441402b | 663 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
664 | tick_do_timer_cpu = cpu; |
665 | ||
79bf2bb3 | 666 | /* Check, if the jiffies need an update */ |
d3ed7824 TG |
667 | if (tick_do_timer_cpu == cpu) |
668 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
669 | |
670 | /* | |
671 | * When we are idle and the tick is stopped, we have to touch | |
672 | * the watchdog as we might not schedule for a really long | |
673 | * time. This happens on complete idle SMP systems while | |
674 | * waiting on the login prompt. We also increment the "start | |
675 | * of idle" jiffy stamp so the idle accounting adjustment we | |
676 | * do when we go busy again does not account too much ticks. | |
677 | */ | |
678 | if (ts->tick_stopped) { | |
679 | touch_softlockup_watchdog(); | |
680 | ts->idle_jiffies++; | |
681 | } | |
682 | ||
683 | update_process_times(user_mode(regs)); | |
684 | profile_tick(CPU_PROFILING); | |
685 | ||
79bf2bb3 TG |
686 | while (tick_nohz_reprogram(ts, now)) { |
687 | now = ktime_get(); | |
688 | tick_do_update_jiffies64(now); | |
689 | } | |
690 | } | |
691 | ||
692 | /** | |
693 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
694 | */ | |
695 | static void tick_nohz_switch_to_nohz(void) | |
696 | { | |
697 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
698 | ktime_t next; | |
699 | ||
700 | if (!tick_nohz_enabled) | |
701 | return; | |
702 | ||
703 | local_irq_disable(); | |
704 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
705 | local_irq_enable(); | |
706 | return; | |
707 | } | |
708 | ||
709 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
710 | ||
711 | /* | |
712 | * Recycle the hrtimer in ts, so we can share the | |
713 | * hrtimer_forward with the highres code. | |
714 | */ | |
715 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
716 | /* Get the next period */ | |
717 | next = tick_init_jiffy_update(); | |
718 | ||
719 | for (;;) { | |
cc584b21 | 720 | hrtimer_set_expires(&ts->sched_timer, next); |
79bf2bb3 TG |
721 | if (!tick_program_event(next, 0)) |
722 | break; | |
723 | next = ktime_add(next, tick_period); | |
724 | } | |
725 | local_irq_enable(); | |
79bf2bb3 TG |
726 | } |
727 | ||
fb02fbc1 TG |
728 | /* |
729 | * When NOHZ is enabled and the tick is stopped, we need to kick the | |
730 | * tick timer from irq_enter() so that the jiffies update is kept | |
731 | * alive during long running softirqs. That's ugly as hell, but | |
732 | * correctness is key even if we need to fix the offending softirq in | |
733 | * the first place. | |
734 | * | |
735 | * Note, this is different to tick_nohz_restart. We just kick the | |
736 | * timer and do not touch the other magic bits which need to be done | |
737 | * when idle is left. | |
738 | */ | |
eed3b9cf | 739 | static void tick_nohz_kick_tick(int cpu, ktime_t now) |
fb02fbc1 | 740 | { |
ae99286b TG |
741 | #if 0 |
742 | /* Switch back to 2.6.27 behaviour */ | |
743 | ||
fb02fbc1 | 744 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
eed3b9cf | 745 | ktime_t delta; |
fb02fbc1 | 746 | |
c4bd822e TG |
747 | /* |
748 | * Do not touch the tick device, when the next expiry is either | |
749 | * already reached or less/equal than the tick period. | |
750 | */ | |
268a3dcf | 751 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
c4bd822e TG |
752 | if (delta.tv64 <= tick_period.tv64) |
753 | return; | |
754 | ||
755 | tick_nohz_restart(ts, now); | |
ae99286b | 756 | #endif |
fb02fbc1 TG |
757 | } |
758 | ||
eed3b9cf MS |
759 | static inline void tick_check_nohz(int cpu) |
760 | { | |
761 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
762 | ktime_t now; | |
763 | ||
764 | if (!ts->idle_active && !ts->tick_stopped) | |
765 | return; | |
766 | now = ktime_get(); | |
767 | if (ts->idle_active) | |
768 | tick_nohz_stop_idle(cpu, now); | |
769 | if (ts->tick_stopped) { | |
770 | tick_nohz_update_jiffies(now); | |
771 | tick_nohz_kick_tick(cpu, now); | |
772 | } | |
773 | } | |
774 | ||
79bf2bb3 TG |
775 | #else |
776 | ||
777 | static inline void tick_nohz_switch_to_nohz(void) { } | |
eed3b9cf | 778 | static inline void tick_check_nohz(int cpu) { } |
79bf2bb3 TG |
779 | |
780 | #endif /* NO_HZ */ | |
781 | ||
719254fa TG |
782 | /* |
783 | * Called from irq_enter to notify about the possible interruption of idle() | |
784 | */ | |
785 | void tick_check_idle(int cpu) | |
786 | { | |
fb02fbc1 | 787 | tick_check_oneshot_broadcast(cpu); |
eed3b9cf | 788 | tick_check_nohz(cpu); |
719254fa TG |
789 | } |
790 | ||
79bf2bb3 TG |
791 | /* |
792 | * High resolution timer specific code | |
793 | */ | |
794 | #ifdef CONFIG_HIGH_RES_TIMERS | |
795 | /* | |
4c9dc641 | 796 | * We rearm the timer until we get disabled by the idle code. |
79bf2bb3 TG |
797 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
798 | */ | |
799 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
800 | { | |
801 | struct tick_sched *ts = | |
802 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
803 | struct pt_regs *regs = get_irq_regs(); |
804 | ktime_t now = ktime_get(); | |
d3ed7824 TG |
805 | int cpu = smp_processor_id(); |
806 | ||
807 | #ifdef CONFIG_NO_HZ | |
808 | /* | |
809 | * Check if the do_timer duty was dropped. We don't care about | |
810 | * concurrency: This happens only when the cpu in charge went | |
811 | * into a long sleep. If two cpus happen to assign themself to | |
812 | * this duty, then the jiffies update is still serialized by | |
813 | * xtime_lock. | |
814 | */ | |
6441402b | 815 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
816 | tick_do_timer_cpu = cpu; |
817 | #endif | |
79bf2bb3 TG |
818 | |
819 | /* Check, if the jiffies need an update */ | |
d3ed7824 TG |
820 | if (tick_do_timer_cpu == cpu) |
821 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
822 | |
823 | /* | |
824 | * Do not call, when we are not in irq context and have | |
825 | * no valid regs pointer | |
826 | */ | |
827 | if (regs) { | |
828 | /* | |
829 | * When we are idle and the tick is stopped, we have to touch | |
830 | * the watchdog as we might not schedule for a really long | |
831 | * time. This happens on complete idle SMP systems while | |
832 | * waiting on the login prompt. We also increment the "start of | |
833 | * idle" jiffy stamp so the idle accounting adjustment we do | |
834 | * when we go busy again does not account too much ticks. | |
835 | */ | |
836 | if (ts->tick_stopped) { | |
837 | touch_softlockup_watchdog(); | |
2ac0d98f FW |
838 | if (idle_cpu(cpu)) |
839 | ts->idle_jiffies++; | |
79bf2bb3 | 840 | } |
79bf2bb3 TG |
841 | update_process_times(user_mode(regs)); |
842 | profile_tick(CPU_PROFILING); | |
79bf2bb3 TG |
843 | } |
844 | ||
79bf2bb3 TG |
845 | hrtimer_forward(timer, now, tick_period); |
846 | ||
847 | return HRTIMER_RESTART; | |
848 | } | |
849 | ||
5307c955 MG |
850 | static int sched_skew_tick; |
851 | ||
62cf20b3 TG |
852 | static int __init skew_tick(char *str) |
853 | { | |
854 | get_option(&str, &sched_skew_tick); | |
855 | ||
856 | return 0; | |
857 | } | |
858 | early_param("skew_tick", skew_tick); | |
859 | ||
79bf2bb3 TG |
860 | /** |
861 | * tick_setup_sched_timer - setup the tick emulation timer | |
862 | */ | |
863 | void tick_setup_sched_timer(void) | |
864 | { | |
865 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
866 | ktime_t now = ktime_get(); | |
867 | ||
868 | /* | |
869 | * Emulate tick processing via per-CPU hrtimers: | |
870 | */ | |
871 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
872 | ts->sched_timer.function = tick_sched_timer; | |
79bf2bb3 | 873 | |
3704540b | 874 | /* Get the next period (per cpu) */ |
cc584b21 | 875 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
79bf2bb3 | 876 | |
5307c955 MG |
877 | /* Offset the tick to avert xtime_lock contention. */ |
878 | if (sched_skew_tick) { | |
879 | u64 offset = ktime_to_ns(tick_period) >> 1; | |
880 | do_div(offset, num_possible_cpus()); | |
881 | offset *= smp_processor_id(); | |
882 | hrtimer_add_expires_ns(&ts->sched_timer, offset); | |
883 | } | |
884 | ||
79bf2bb3 TG |
885 | for (;;) { |
886 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
5c333864 AB |
887 | hrtimer_start_expires(&ts->sched_timer, |
888 | HRTIMER_MODE_ABS_PINNED); | |
79bf2bb3 TG |
889 | /* Check, if the timer was already in the past */ |
890 | if (hrtimer_active(&ts->sched_timer)) | |
891 | break; | |
892 | now = ktime_get(); | |
893 | } | |
894 | ||
895 | #ifdef CONFIG_NO_HZ | |
29c158e8 | 896 | if (tick_nohz_enabled) |
79bf2bb3 TG |
897 | ts->nohz_mode = NOHZ_MODE_HIGHRES; |
898 | #endif | |
899 | } | |
3c4fbe5e | 900 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 901 | |
3c4fbe5e | 902 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
903 | void tick_cancel_sched_timer(int cpu) |
904 | { | |
905 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
906 | ||
3c4fbe5e | 907 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
908 | if (ts->sched_timer.base) |
909 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 910 | # endif |
a7901766 | 911 | |
79bf2bb3 TG |
912 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
913 | } | |
3c4fbe5e | 914 | #endif |
79bf2bb3 TG |
915 | |
916 | /** | |
917 | * Async notification about clocksource changes | |
918 | */ | |
919 | void tick_clock_notify(void) | |
920 | { | |
921 | int cpu; | |
922 | ||
923 | for_each_possible_cpu(cpu) | |
924 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
925 | } | |
926 | ||
927 | /* | |
928 | * Async notification about clock event changes | |
929 | */ | |
930 | void tick_oneshot_notify(void) | |
931 | { | |
932 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
933 | ||
934 | set_bit(0, &ts->check_clocks); | |
935 | } | |
936 | ||
937 | /** | |
938 | * Check, if a change happened, which makes oneshot possible. | |
939 | * | |
940 | * Called cyclic from the hrtimer softirq (driven by the timer | |
941 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
942 | * mode, because high resolution timers are disabled (either compile | |
943 | * or runtime). | |
944 | */ | |
945 | int tick_check_oneshot_change(int allow_nohz) | |
946 | { | |
947 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
948 | ||
949 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
950 | return 0; | |
951 | ||
952 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
953 | return 0; | |
954 | ||
cf4fc6cb | 955 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
956 | return 0; |
957 | ||
958 | if (!allow_nohz) | |
959 | return 1; | |
960 | ||
961 | tick_nohz_switch_to_nohz(); | |
962 | return 0; | |
963 | } |