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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> | |
8083e4ad | 22 | #include <linux/module.h> |
00b42959 | 23 | #include <linux/irq_work.h> |
79bf2bb3 | 24 | |
9e203bcc DM |
25 | #include <asm/irq_regs.h> |
26 | ||
79bf2bb3 TG |
27 | #include "tick-internal.h" |
28 | ||
29 | /* | |
30 | * Per cpu nohz control structure | |
31 | */ | |
33a5f626 | 32 | DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); |
79bf2bb3 TG |
33 | |
34 | /* | |
d6ad4187 | 35 | * The time, when the last jiffy update happened. Protected by jiffies_lock. |
79bf2bb3 TG |
36 | */ |
37 | static ktime_t last_jiffies_update; | |
38 | ||
289f480a IM |
39 | struct tick_sched *tick_get_tick_sched(int cpu) |
40 | { | |
41 | return &per_cpu(tick_cpu_sched, cpu); | |
42 | } | |
43 | ||
79bf2bb3 TG |
44 | /* |
45 | * Must be called with interrupts disabled ! | |
46 | */ | |
47 | static void tick_do_update_jiffies64(ktime_t now) | |
48 | { | |
49 | unsigned long ticks = 0; | |
50 | ktime_t delta; | |
51 | ||
7a14ce1d | 52 | /* |
d6ad4187 | 53 | * Do a quick check without holding jiffies_lock: |
7a14ce1d IM |
54 | */ |
55 | delta = ktime_sub(now, last_jiffies_update); | |
56 | if (delta.tv64 < tick_period.tv64) | |
57 | return; | |
58 | ||
d6ad4187 JS |
59 | /* Reevalute with jiffies_lock held */ |
60 | write_seqlock(&jiffies_lock); | |
79bf2bb3 TG |
61 | |
62 | delta = ktime_sub(now, last_jiffies_update); | |
63 | if (delta.tv64 >= tick_period.tv64) { | |
64 | ||
65 | delta = ktime_sub(delta, tick_period); | |
66 | last_jiffies_update = ktime_add(last_jiffies_update, | |
67 | tick_period); | |
68 | ||
69 | /* Slow path for long timeouts */ | |
70 | if (unlikely(delta.tv64 >= tick_period.tv64)) { | |
71 | s64 incr = ktime_to_ns(tick_period); | |
72 | ||
73 | ticks = ktime_divns(delta, incr); | |
74 | ||
75 | last_jiffies_update = ktime_add_ns(last_jiffies_update, | |
76 | incr * ticks); | |
77 | } | |
78 | do_timer(++ticks); | |
49d670fb TG |
79 | |
80 | /* Keep the tick_next_period variable up to date */ | |
81 | tick_next_period = ktime_add(last_jiffies_update, tick_period); | |
79bf2bb3 | 82 | } |
d6ad4187 | 83 | write_sequnlock(&jiffies_lock); |
79bf2bb3 TG |
84 | } |
85 | ||
86 | /* | |
87 | * Initialize and return retrieve the jiffies update. | |
88 | */ | |
89 | static ktime_t tick_init_jiffy_update(void) | |
90 | { | |
91 | ktime_t period; | |
92 | ||
d6ad4187 | 93 | write_seqlock(&jiffies_lock); |
79bf2bb3 TG |
94 | /* Did we start the jiffies update yet ? */ |
95 | if (last_jiffies_update.tv64 == 0) | |
96 | last_jiffies_update = tick_next_period; | |
97 | period = last_jiffies_update; | |
d6ad4187 | 98 | write_sequnlock(&jiffies_lock); |
79bf2bb3 TG |
99 | return period; |
100 | } | |
101 | ||
5bb96226 FW |
102 | |
103 | static void tick_sched_do_timer(ktime_t now) | |
104 | { | |
105 | int cpu = smp_processor_id(); | |
106 | ||
107 | #ifdef CONFIG_NO_HZ | |
108 | /* | |
109 | * Check if the do_timer duty was dropped. We don't care about | |
110 | * concurrency: This happens only when the cpu in charge went | |
111 | * into a long sleep. If two cpus happen to assign themself to | |
112 | * this duty, then the jiffies update is still serialized by | |
9c3f9e28 | 113 | * jiffies_lock. |
5bb96226 FW |
114 | */ |
115 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) | |
116 | tick_do_timer_cpu = cpu; | |
117 | #endif | |
118 | ||
119 | /* Check, if the jiffies need an update */ | |
120 | if (tick_do_timer_cpu == cpu) | |
121 | tick_do_update_jiffies64(now); | |
122 | } | |
123 | ||
9e8f559b FW |
124 | static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) |
125 | { | |
94a57140 | 126 | #ifdef CONFIG_NO_HZ |
9e8f559b FW |
127 | /* |
128 | * When we are idle and the tick is stopped, we have to touch | |
129 | * the watchdog as we might not schedule for a really long | |
130 | * time. This happens on complete idle SMP systems while | |
131 | * waiting on the login prompt. We also increment the "start of | |
132 | * idle" jiffy stamp so the idle accounting adjustment we do | |
133 | * when we go busy again does not account too much ticks. | |
134 | */ | |
135 | if (ts->tick_stopped) { | |
136 | touch_softlockup_watchdog(); | |
137 | if (is_idle_task(current)) | |
138 | ts->idle_jiffies++; | |
139 | } | |
94a57140 | 140 | #endif |
9e8f559b FW |
141 | update_process_times(user_mode(regs)); |
142 | profile_tick(CPU_PROFILING); | |
143 | } | |
144 | ||
79bf2bb3 TG |
145 | /* |
146 | * NOHZ - aka dynamic tick functionality | |
147 | */ | |
148 | #ifdef CONFIG_NO_HZ | |
149 | /* | |
150 | * NO HZ enabled ? | |
151 | */ | |
9d2ad243 | 152 | int tick_nohz_enabled __read_mostly = 1; |
79bf2bb3 TG |
153 | |
154 | /* | |
155 | * Enable / Disable tickless mode | |
156 | */ | |
157 | static int __init setup_tick_nohz(char *str) | |
158 | { | |
159 | if (!strcmp(str, "off")) | |
160 | tick_nohz_enabled = 0; | |
161 | else if (!strcmp(str, "on")) | |
162 | tick_nohz_enabled = 1; | |
163 | else | |
164 | return 0; | |
165 | return 1; | |
166 | } | |
167 | ||
168 | __setup("nohz=", setup_tick_nohz); | |
169 | ||
170 | /** | |
171 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
172 | * | |
173 | * Called from interrupt entry when the CPU was idle | |
174 | * | |
175 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
176 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
177 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
178 | * cpu, which has the update task assigned is in a long sleep. | |
179 | */ | |
eed3b9cf | 180 | static void tick_nohz_update_jiffies(ktime_t now) |
79bf2bb3 TG |
181 | { |
182 | int cpu = smp_processor_id(); | |
183 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
184 | unsigned long flags; | |
79bf2bb3 | 185 | |
5df7fa1c | 186 | ts->idle_waketime = now; |
79bf2bb3 TG |
187 | |
188 | local_irq_save(flags); | |
189 | tick_do_update_jiffies64(now); | |
190 | local_irq_restore(flags); | |
02ff3755 IM |
191 | |
192 | touch_softlockup_watchdog(); | |
79bf2bb3 TG |
193 | } |
194 | ||
595aac48 AV |
195 | /* |
196 | * Updates the per cpu time idle statistics counters | |
197 | */ | |
8d63bf94 | 198 | static void |
8c215bd3 | 199 | update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
6378ddb5 | 200 | { |
eed3b9cf | 201 | ktime_t delta; |
6378ddb5 | 202 | |
595aac48 AV |
203 | if (ts->idle_active) { |
204 | delta = ktime_sub(now, ts->idle_entrytime); | |
8c215bd3 | 205 | if (nr_iowait_cpu(cpu) > 0) |
0224cf4c | 206 | ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
6beea0cd MH |
207 | else |
208 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
8c7b09f4 | 209 | ts->idle_entrytime = now; |
595aac48 | 210 | } |
8d63bf94 | 211 | |
e0e37c20 | 212 | if (last_update_time) |
8d63bf94 AV |
213 | *last_update_time = ktime_to_us(now); |
214 | ||
595aac48 AV |
215 | } |
216 | ||
217 | static void tick_nohz_stop_idle(int cpu, ktime_t now) | |
218 | { | |
219 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
220 | ||
8c215bd3 | 221 | update_ts_time_stats(cpu, ts, now, NULL); |
eed3b9cf | 222 | ts->idle_active = 0; |
56c7426b | 223 | |
eed3b9cf | 224 | sched_clock_idle_wakeup_event(0); |
6378ddb5 VP |
225 | } |
226 | ||
8c215bd3 | 227 | static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) |
6378ddb5 | 228 | { |
430ee881 | 229 | ktime_t now = ktime_get(); |
595aac48 | 230 | |
6378ddb5 VP |
231 | ts->idle_entrytime = now; |
232 | ts->idle_active = 1; | |
56c7426b | 233 | sched_clock_idle_sleep_event(); |
6378ddb5 VP |
234 | return now; |
235 | } | |
236 | ||
b1f724c3 AV |
237 | /** |
238 | * get_cpu_idle_time_us - get the total idle time of a cpu | |
239 | * @cpu: CPU number to query | |
09a1d34f MH |
240 | * @last_update_time: variable to store update time in. Do not update |
241 | * counters if NULL. | |
b1f724c3 AV |
242 | * |
243 | * Return the cummulative idle time (since boot) for a given | |
6beea0cd | 244 | * CPU, in microseconds. |
b1f724c3 AV |
245 | * |
246 | * This time is measured via accounting rather than sampling, | |
247 | * and is as accurate as ktime_get() is. | |
248 | * | |
249 | * This function returns -1 if NOHZ is not enabled. | |
250 | */ | |
6378ddb5 VP |
251 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
252 | { | |
253 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 254 | ktime_t now, idle; |
6378ddb5 | 255 | |
8083e4ad | 256 | if (!tick_nohz_enabled) |
257 | return -1; | |
258 | ||
09a1d34f MH |
259 | now = ktime_get(); |
260 | if (last_update_time) { | |
261 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
262 | idle = ts->idle_sleeptime; | |
263 | } else { | |
264 | if (ts->idle_active && !nr_iowait_cpu(cpu)) { | |
265 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
266 | ||
267 | idle = ktime_add(ts->idle_sleeptime, delta); | |
268 | } else { | |
269 | idle = ts->idle_sleeptime; | |
270 | } | |
271 | } | |
272 | ||
273 | return ktime_to_us(idle); | |
8083e4ad | 274 | |
6378ddb5 | 275 | } |
8083e4ad | 276 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
6378ddb5 | 277 | |
6beea0cd | 278 | /** |
0224cf4c AV |
279 | * get_cpu_iowait_time_us - get the total iowait time of a cpu |
280 | * @cpu: CPU number to query | |
09a1d34f MH |
281 | * @last_update_time: variable to store update time in. Do not update |
282 | * counters if NULL. | |
0224cf4c AV |
283 | * |
284 | * Return the cummulative iowait time (since boot) for a given | |
285 | * CPU, in microseconds. | |
286 | * | |
287 | * This time is measured via accounting rather than sampling, | |
288 | * and is as accurate as ktime_get() is. | |
289 | * | |
290 | * This function returns -1 if NOHZ is not enabled. | |
291 | */ | |
292 | u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) | |
293 | { | |
294 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 295 | ktime_t now, iowait; |
0224cf4c AV |
296 | |
297 | if (!tick_nohz_enabled) | |
298 | return -1; | |
299 | ||
09a1d34f MH |
300 | now = ktime_get(); |
301 | if (last_update_time) { | |
302 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
303 | iowait = ts->iowait_sleeptime; | |
304 | } else { | |
305 | if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { | |
306 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
0224cf4c | 307 | |
09a1d34f MH |
308 | iowait = ktime_add(ts->iowait_sleeptime, delta); |
309 | } else { | |
310 | iowait = ts->iowait_sleeptime; | |
311 | } | |
312 | } | |
0224cf4c | 313 | |
09a1d34f | 314 | return ktime_to_us(iowait); |
0224cf4c AV |
315 | } |
316 | EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); | |
317 | ||
84bf1bcc FW |
318 | static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, |
319 | ktime_t now, int cpu) | |
79bf2bb3 | 320 | { |
280f0677 | 321 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies; |
84bf1bcc | 322 | ktime_t last_update, expires, ret = { .tv64 = 0 }; |
aa9b1630 | 323 | unsigned long rcu_delta_jiffies; |
4f86d3a8 | 324 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
98962465 | 325 | u64 time_delta; |
79bf2bb3 | 326 | |
79bf2bb3 TG |
327 | /* Read jiffies and the time when jiffies were updated last */ |
328 | do { | |
d6ad4187 | 329 | seq = read_seqbegin(&jiffies_lock); |
79bf2bb3 TG |
330 | last_update = last_jiffies_update; |
331 | last_jiffies = jiffies; | |
27185016 | 332 | time_delta = timekeeping_max_deferment(); |
d6ad4187 | 333 | } while (read_seqretry(&jiffies_lock, seq)); |
79bf2bb3 | 334 | |
74876a98 | 335 | if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || |
00b42959 | 336 | arch_needs_cpu(cpu) || irq_work_needs_cpu()) { |
3c5d92a0 | 337 | next_jiffies = last_jiffies + 1; |
6ba9b346 | 338 | delta_jiffies = 1; |
3c5d92a0 MS |
339 | } else { |
340 | /* Get the next timer wheel timer */ | |
341 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
342 | delta_jiffies = next_jiffies - last_jiffies; | |
aa9b1630 PM |
343 | if (rcu_delta_jiffies < delta_jiffies) { |
344 | next_jiffies = last_jiffies + rcu_delta_jiffies; | |
345 | delta_jiffies = rcu_delta_jiffies; | |
346 | } | |
3c5d92a0 | 347 | } |
79bf2bb3 TG |
348 | /* |
349 | * Do not stop the tick, if we are only one off | |
350 | * or if the cpu is required for rcu | |
351 | */ | |
6ba9b346 | 352 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
353 | goto out; |
354 | ||
355 | /* Schedule the tick, if we are at least one jiffie off */ | |
356 | if ((long)delta_jiffies >= 1) { | |
357 | ||
00147449 WR |
358 | /* |
359 | * If this cpu is the one which updates jiffies, then | |
360 | * give up the assignment and let it be taken by the | |
361 | * cpu which runs the tick timer next, which might be | |
362 | * this cpu as well. If we don't drop this here the | |
363 | * jiffies might be stale and do_timer() never | |
27185016 TG |
364 | * invoked. Keep track of the fact that it was the one |
365 | * which had the do_timer() duty last. If this cpu is | |
366 | * the one which had the do_timer() duty last, we | |
367 | * limit the sleep time to the timekeeping | |
368 | * max_deferement value which we retrieved | |
369 | * above. Otherwise we can sleep as long as we want. | |
00147449 | 370 | */ |
27185016 | 371 | if (cpu == tick_do_timer_cpu) { |
00147449 | 372 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
27185016 TG |
373 | ts->do_timer_last = 1; |
374 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { | |
375 | time_delta = KTIME_MAX; | |
376 | ts->do_timer_last = 0; | |
377 | } else if (!ts->do_timer_last) { | |
378 | time_delta = KTIME_MAX; | |
379 | } | |
380 | ||
00147449 | 381 | /* |
98962465 JH |
382 | * calculate the expiry time for the next timer wheel |
383 | * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals | |
384 | * that there is no timer pending or at least extremely | |
385 | * far into the future (12 days for HZ=1000). In this | |
386 | * case we set the expiry to the end of time. | |
387 | */ | |
388 | if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) { | |
389 | /* | |
390 | * Calculate the time delta for the next timer event. | |
391 | * If the time delta exceeds the maximum time delta | |
392 | * permitted by the current clocksource then adjust | |
393 | * the time delta accordingly to ensure the | |
394 | * clocksource does not wrap. | |
395 | */ | |
396 | time_delta = min_t(u64, time_delta, | |
397 | tick_period.tv64 * delta_jiffies); | |
98962465 | 398 | } |
00147449 | 399 | |
27185016 TG |
400 | if (time_delta < KTIME_MAX) |
401 | expires = ktime_add_ns(last_update, time_delta); | |
402 | else | |
403 | expires.tv64 = KTIME_MAX; | |
00147449 | 404 | |
00147449 WR |
405 | /* Skip reprogram of event if its not changed */ |
406 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) | |
407 | goto out; | |
408 | ||
84bf1bcc FW |
409 | ret = expires; |
410 | ||
79bf2bb3 TG |
411 | /* |
412 | * nohz_stop_sched_tick can be called several times before | |
413 | * the nohz_restart_sched_tick is called. This happens when | |
414 | * interrupts arrive which do not cause a reschedule. In the | |
415 | * first call we save the current tick time, so we can restart | |
416 | * the scheduler tick in nohz_restart_sched_tick. | |
417 | */ | |
418 | if (!ts->tick_stopped) { | |
c1cc017c | 419 | nohz_balance_enter_idle(cpu); |
5167e8d5 | 420 | calc_load_enter_idle(); |
46cb4b7c | 421 | |
f5d411c9 | 422 | ts->last_tick = hrtimer_get_expires(&ts->sched_timer); |
79bf2bb3 | 423 | ts->tick_stopped = 1; |
79bf2bb3 | 424 | } |
d3ed7824 | 425 | |
eaad084b | 426 | /* |
98962465 JH |
427 | * If the expiration time == KTIME_MAX, then |
428 | * in this case we simply stop the tick timer. | |
eaad084b | 429 | */ |
98962465 | 430 | if (unlikely(expires.tv64 == KTIME_MAX)) { |
eaad084b TG |
431 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
432 | hrtimer_cancel(&ts->sched_timer); | |
433 | goto out; | |
434 | } | |
435 | ||
79bf2bb3 TG |
436 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
437 | hrtimer_start(&ts->sched_timer, expires, | |
5c333864 | 438 | HRTIMER_MODE_ABS_PINNED); |
79bf2bb3 TG |
439 | /* Check, if the timer was already in the past */ |
440 | if (hrtimer_active(&ts->sched_timer)) | |
441 | goto out; | |
4c9dc641 | 442 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
443 | goto out; |
444 | /* | |
445 | * We are past the event already. So we crossed a | |
446 | * jiffie boundary. Update jiffies and raise the | |
447 | * softirq. | |
448 | */ | |
449 | tick_do_update_jiffies64(ktime_get()); | |
79bf2bb3 TG |
450 | } |
451 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
452 | out: | |
453 | ts->next_jiffies = next_jiffies; | |
454 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 455 | ts->sleep_length = ktime_sub(dev->next_event, now); |
84bf1bcc FW |
456 | |
457 | return ret; | |
280f0677 FW |
458 | } |
459 | ||
5b39939a FW |
460 | static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) |
461 | { | |
462 | /* | |
463 | * If this cpu is offline and it is the one which updates | |
464 | * jiffies, then give up the assignment and let it be taken by | |
465 | * the cpu which runs the tick timer next. If we don't drop | |
466 | * this here the jiffies might be stale and do_timer() never | |
467 | * invoked. | |
468 | */ | |
469 | if (unlikely(!cpu_online(cpu))) { | |
470 | if (cpu == tick_do_timer_cpu) | |
471 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
472 | } | |
473 | ||
474 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) | |
475 | return false; | |
476 | ||
477 | if (need_resched()) | |
478 | return false; | |
479 | ||
480 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { | |
481 | static int ratelimit; | |
482 | ||
803b0eba PM |
483 | if (ratelimit < 10 && |
484 | (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { | |
cfea7d7e RV |
485 | pr_warn("NOHZ: local_softirq_pending %02x\n", |
486 | (unsigned int) local_softirq_pending()); | |
5b39939a FW |
487 | ratelimit++; |
488 | } | |
489 | return false; | |
490 | } | |
491 | ||
492 | return true; | |
493 | } | |
494 | ||
19f5f736 FW |
495 | static void __tick_nohz_idle_enter(struct tick_sched *ts) |
496 | { | |
84bf1bcc | 497 | ktime_t now, expires; |
5b39939a | 498 | int cpu = smp_processor_id(); |
19f5f736 | 499 | |
5b39939a | 500 | now = tick_nohz_start_idle(cpu, ts); |
2ac0d98f | 501 | |
5b39939a FW |
502 | if (can_stop_idle_tick(cpu, ts)) { |
503 | int was_stopped = ts->tick_stopped; | |
504 | ||
505 | ts->idle_calls++; | |
84bf1bcc FW |
506 | |
507 | expires = tick_nohz_stop_sched_tick(ts, now, cpu); | |
508 | if (expires.tv64 > 0LL) { | |
509 | ts->idle_sleeps++; | |
510 | ts->idle_expires = expires; | |
511 | } | |
5b39939a FW |
512 | |
513 | if (!was_stopped && ts->tick_stopped) | |
514 | ts->idle_jiffies = ts->last_jiffies; | |
515 | } | |
280f0677 FW |
516 | } |
517 | ||
518 | /** | |
519 | * tick_nohz_idle_enter - stop the idle tick from the idle task | |
520 | * | |
521 | * When the next event is more than a tick into the future, stop the idle tick | |
522 | * Called when we start the idle loop. | |
2bbb6817 | 523 | * |
1268fbc7 | 524 | * The arch is responsible of calling: |
2bbb6817 FW |
525 | * |
526 | * - rcu_idle_enter() after its last use of RCU before the CPU is put | |
527 | * to sleep. | |
528 | * - rcu_idle_exit() before the first use of RCU after the CPU is woken up. | |
280f0677 | 529 | */ |
1268fbc7 | 530 | void tick_nohz_idle_enter(void) |
280f0677 FW |
531 | { |
532 | struct tick_sched *ts; | |
533 | ||
1268fbc7 FW |
534 | WARN_ON_ONCE(irqs_disabled()); |
535 | ||
0db49b72 LT |
536 | /* |
537 | * Update the idle state in the scheduler domain hierarchy | |
538 | * when tick_nohz_stop_sched_tick() is called from the idle loop. | |
539 | * State will be updated to busy during the first busy tick after | |
540 | * exiting idle. | |
541 | */ | |
542 | set_cpu_sd_state_idle(); | |
543 | ||
1268fbc7 FW |
544 | local_irq_disable(); |
545 | ||
280f0677 FW |
546 | ts = &__get_cpu_var(tick_cpu_sched); |
547 | /* | |
548 | * set ts->inidle unconditionally. even if the system did not | |
549 | * switch to nohz mode the cpu frequency governers rely on the | |
550 | * update of the idle time accounting in tick_nohz_start_idle(). | |
551 | */ | |
552 | ts->inidle = 1; | |
19f5f736 | 553 | __tick_nohz_idle_enter(ts); |
1268fbc7 FW |
554 | |
555 | local_irq_enable(); | |
280f0677 | 556 | } |
4dbd2771 | 557 | EXPORT_SYMBOL_GPL(tick_nohz_idle_enter); |
280f0677 FW |
558 | |
559 | /** | |
560 | * tick_nohz_irq_exit - update next tick event from interrupt exit | |
561 | * | |
562 | * When an interrupt fires while we are idle and it doesn't cause | |
563 | * a reschedule, it may still add, modify or delete a timer, enqueue | |
564 | * an RCU callback, etc... | |
565 | * So we need to re-calculate and reprogram the next tick event. | |
566 | */ | |
567 | void tick_nohz_irq_exit(void) | |
568 | { | |
569 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
570 | ||
571 | if (!ts->inidle) | |
572 | return; | |
573 | ||
69a37bea YS |
574 | /* Cancel the timer because CPU already waken up from the C-states*/ |
575 | menu_hrtimer_cancel(); | |
19f5f736 | 576 | __tick_nohz_idle_enter(ts); |
79bf2bb3 TG |
577 | } |
578 | ||
4f86d3a8 LB |
579 | /** |
580 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
581 | * | |
582 | * Called from power state control code with interrupts disabled | |
583 | */ | |
584 | ktime_t tick_nohz_get_sleep_length(void) | |
585 | { | |
586 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
587 | ||
588 | return ts->sleep_length; | |
589 | } | |
590 | ||
c34bec5a TG |
591 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
592 | { | |
593 | hrtimer_cancel(&ts->sched_timer); | |
f5d411c9 | 594 | hrtimer_set_expires(&ts->sched_timer, ts->last_tick); |
c34bec5a TG |
595 | |
596 | while (1) { | |
597 | /* Forward the time to expire in the future */ | |
598 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
599 | ||
600 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
268a3dcf | 601 | hrtimer_start_expires(&ts->sched_timer, |
5c333864 | 602 | HRTIMER_MODE_ABS_PINNED); |
c34bec5a TG |
603 | /* Check, if the timer was already in the past */ |
604 | if (hrtimer_active(&ts->sched_timer)) | |
605 | break; | |
606 | } else { | |
268a3dcf TG |
607 | if (!tick_program_event( |
608 | hrtimer_get_expires(&ts->sched_timer), 0)) | |
c34bec5a TG |
609 | break; |
610 | } | |
6f103929 | 611 | /* Reread time and update jiffies */ |
c34bec5a | 612 | now = ktime_get(); |
6f103929 | 613 | tick_do_update_jiffies64(now); |
c34bec5a TG |
614 | } |
615 | } | |
616 | ||
19f5f736 | 617 | static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) |
79bf2bb3 | 618 | { |
79bf2bb3 | 619 | /* Update jiffies first */ |
79bf2bb3 | 620 | tick_do_update_jiffies64(now); |
5aaa0b7a | 621 | update_cpu_load_nohz(); |
79bf2bb3 | 622 | |
749c8814 | 623 | calc_load_exit_idle(); |
2ac0d98f FW |
624 | touch_softlockup_watchdog(); |
625 | /* | |
626 | * Cancel the scheduled timer and restore the tick | |
627 | */ | |
628 | ts->tick_stopped = 0; | |
629 | ts->idle_exittime = now; | |
630 | ||
631 | tick_nohz_restart(ts, now); | |
632 | } | |
633 | ||
634 | static void tick_nohz_account_idle_ticks(struct tick_sched *ts) | |
635 | { | |
3f4724ea | 636 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE |
2ac0d98f | 637 | unsigned long ticks; |
3f4724ea FW |
638 | |
639 | if (vtime_accounting_enabled()) | |
640 | return; | |
79bf2bb3 TG |
641 | /* |
642 | * We stopped the tick in idle. Update process times would miss the | |
643 | * time we slept as update_process_times does only a 1 tick | |
644 | * accounting. Enforce that this is accounted to idle ! | |
645 | */ | |
646 | ticks = jiffies - ts->idle_jiffies; | |
647 | /* | |
648 | * We might be one off. Do not randomly account a huge number of ticks! | |
649 | */ | |
79741dd3 MS |
650 | if (ticks && ticks < LONG_MAX) |
651 | account_idle_ticks(ticks); | |
652 | #endif | |
19f5f736 FW |
653 | } |
654 | ||
79bf2bb3 | 655 | /** |
280f0677 | 656 | * tick_nohz_idle_exit - restart the idle tick from the idle task |
79bf2bb3 TG |
657 | * |
658 | * Restart the idle tick when the CPU is woken up from idle | |
280f0677 FW |
659 | * This also exit the RCU extended quiescent state. The CPU |
660 | * can use RCU again after this function is called. | |
79bf2bb3 | 661 | */ |
280f0677 | 662 | void tick_nohz_idle_exit(void) |
79bf2bb3 TG |
663 | { |
664 | int cpu = smp_processor_id(); | |
665 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
6378ddb5 | 666 | ktime_t now; |
79bf2bb3 | 667 | |
6378ddb5 | 668 | local_irq_disable(); |
2bbb6817 | 669 | |
15f827be FW |
670 | WARN_ON_ONCE(!ts->inidle); |
671 | ||
672 | ts->inidle = 0; | |
673 | ||
69a37bea YS |
674 | /* Cancel the timer because CPU already waken up from the C-states*/ |
675 | menu_hrtimer_cancel(); | |
15f827be | 676 | if (ts->idle_active || ts->tick_stopped) |
eed3b9cf MS |
677 | now = ktime_get(); |
678 | ||
679 | if (ts->idle_active) | |
680 | tick_nohz_stop_idle(cpu, now); | |
6378ddb5 | 681 | |
2ac0d98f | 682 | if (ts->tick_stopped) { |
19f5f736 | 683 | tick_nohz_restart_sched_tick(ts, now); |
2ac0d98f | 684 | tick_nohz_account_idle_ticks(ts); |
6378ddb5 | 685 | } |
79bf2bb3 | 686 | |
79bf2bb3 TG |
687 | local_irq_enable(); |
688 | } | |
4dbd2771 | 689 | EXPORT_SYMBOL_GPL(tick_nohz_idle_exit); |
79bf2bb3 TG |
690 | |
691 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
692 | { | |
693 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
cc584b21 | 694 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
79bf2bb3 TG |
695 | } |
696 | ||
697 | /* | |
698 | * The nohz low res interrupt handler | |
699 | */ | |
700 | static void tick_nohz_handler(struct clock_event_device *dev) | |
701 | { | |
702 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
703 | struct pt_regs *regs = get_irq_regs(); | |
704 | ktime_t now = ktime_get(); | |
705 | ||
706 | dev->next_event.tv64 = KTIME_MAX; | |
707 | ||
5bb96226 | 708 | tick_sched_do_timer(now); |
9e8f559b | 709 | tick_sched_handle(ts, regs); |
79bf2bb3 | 710 | |
79bf2bb3 TG |
711 | while (tick_nohz_reprogram(ts, now)) { |
712 | now = ktime_get(); | |
713 | tick_do_update_jiffies64(now); | |
714 | } | |
715 | } | |
716 | ||
717 | /** | |
718 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
719 | */ | |
720 | static void tick_nohz_switch_to_nohz(void) | |
721 | { | |
722 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
723 | ktime_t next; | |
724 | ||
725 | if (!tick_nohz_enabled) | |
726 | return; | |
727 | ||
728 | local_irq_disable(); | |
729 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
730 | local_irq_enable(); | |
731 | return; | |
732 | } | |
733 | ||
734 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
735 | ||
736 | /* | |
737 | * Recycle the hrtimer in ts, so we can share the | |
738 | * hrtimer_forward with the highres code. | |
739 | */ | |
740 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
741 | /* Get the next period */ | |
742 | next = tick_init_jiffy_update(); | |
743 | ||
744 | for (;;) { | |
cc584b21 | 745 | hrtimer_set_expires(&ts->sched_timer, next); |
79bf2bb3 TG |
746 | if (!tick_program_event(next, 0)) |
747 | break; | |
748 | next = ktime_add(next, tick_period); | |
749 | } | |
750 | local_irq_enable(); | |
79bf2bb3 TG |
751 | } |
752 | ||
fb02fbc1 TG |
753 | /* |
754 | * When NOHZ is enabled and the tick is stopped, we need to kick the | |
755 | * tick timer from irq_enter() so that the jiffies update is kept | |
756 | * alive during long running softirqs. That's ugly as hell, but | |
757 | * correctness is key even if we need to fix the offending softirq in | |
758 | * the first place. | |
759 | * | |
760 | * Note, this is different to tick_nohz_restart. We just kick the | |
761 | * timer and do not touch the other magic bits which need to be done | |
762 | * when idle is left. | |
763 | */ | |
eed3b9cf | 764 | static void tick_nohz_kick_tick(int cpu, ktime_t now) |
fb02fbc1 | 765 | { |
ae99286b TG |
766 | #if 0 |
767 | /* Switch back to 2.6.27 behaviour */ | |
768 | ||
fb02fbc1 | 769 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
eed3b9cf | 770 | ktime_t delta; |
fb02fbc1 | 771 | |
c4bd822e TG |
772 | /* |
773 | * Do not touch the tick device, when the next expiry is either | |
774 | * already reached or less/equal than the tick period. | |
775 | */ | |
268a3dcf | 776 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
c4bd822e TG |
777 | if (delta.tv64 <= tick_period.tv64) |
778 | return; | |
779 | ||
780 | tick_nohz_restart(ts, now); | |
ae99286b | 781 | #endif |
fb02fbc1 TG |
782 | } |
783 | ||
eed3b9cf MS |
784 | static inline void tick_check_nohz(int cpu) |
785 | { | |
786 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
787 | ktime_t now; | |
788 | ||
789 | if (!ts->idle_active && !ts->tick_stopped) | |
790 | return; | |
791 | now = ktime_get(); | |
792 | if (ts->idle_active) | |
793 | tick_nohz_stop_idle(cpu, now); | |
794 | if (ts->tick_stopped) { | |
795 | tick_nohz_update_jiffies(now); | |
796 | tick_nohz_kick_tick(cpu, now); | |
797 | } | |
798 | } | |
799 | ||
79bf2bb3 TG |
800 | #else |
801 | ||
802 | static inline void tick_nohz_switch_to_nohz(void) { } | |
eed3b9cf | 803 | static inline void tick_check_nohz(int cpu) { } |
79bf2bb3 TG |
804 | |
805 | #endif /* NO_HZ */ | |
806 | ||
719254fa TG |
807 | /* |
808 | * Called from irq_enter to notify about the possible interruption of idle() | |
809 | */ | |
810 | void tick_check_idle(int cpu) | |
811 | { | |
fb02fbc1 | 812 | tick_check_oneshot_broadcast(cpu); |
eed3b9cf | 813 | tick_check_nohz(cpu); |
719254fa TG |
814 | } |
815 | ||
79bf2bb3 TG |
816 | /* |
817 | * High resolution timer specific code | |
818 | */ | |
819 | #ifdef CONFIG_HIGH_RES_TIMERS | |
820 | /* | |
4c9dc641 | 821 | * We rearm the timer until we get disabled by the idle code. |
351f181f | 822 | * Called with interrupts disabled. |
79bf2bb3 TG |
823 | */ |
824 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
825 | { | |
826 | struct tick_sched *ts = | |
827 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
828 | struct pt_regs *regs = get_irq_regs(); |
829 | ktime_t now = ktime_get(); | |
d3ed7824 | 830 | |
5bb96226 | 831 | tick_sched_do_timer(now); |
79bf2bb3 TG |
832 | |
833 | /* | |
834 | * Do not call, when we are not in irq context and have | |
835 | * no valid regs pointer | |
836 | */ | |
9e8f559b FW |
837 | if (regs) |
838 | tick_sched_handle(ts, regs); | |
79bf2bb3 | 839 | |
79bf2bb3 TG |
840 | hrtimer_forward(timer, now, tick_period); |
841 | ||
842 | return HRTIMER_RESTART; | |
843 | } | |
844 | ||
5307c955 MG |
845 | static int sched_skew_tick; |
846 | ||
62cf20b3 TG |
847 | static int __init skew_tick(char *str) |
848 | { | |
849 | get_option(&str, &sched_skew_tick); | |
850 | ||
851 | return 0; | |
852 | } | |
853 | early_param("skew_tick", skew_tick); | |
854 | ||
79bf2bb3 TG |
855 | /** |
856 | * tick_setup_sched_timer - setup the tick emulation timer | |
857 | */ | |
858 | void tick_setup_sched_timer(void) | |
859 | { | |
860 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
861 | ktime_t now = ktime_get(); | |
862 | ||
863 | /* | |
864 | * Emulate tick processing via per-CPU hrtimers: | |
865 | */ | |
866 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
867 | ts->sched_timer.function = tick_sched_timer; | |
79bf2bb3 | 868 | |
3704540b | 869 | /* Get the next period (per cpu) */ |
cc584b21 | 870 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
79bf2bb3 | 871 | |
9c3f9e28 | 872 | /* Offset the tick to avert jiffies_lock contention. */ |
5307c955 MG |
873 | if (sched_skew_tick) { |
874 | u64 offset = ktime_to_ns(tick_period) >> 1; | |
875 | do_div(offset, num_possible_cpus()); | |
876 | offset *= smp_processor_id(); | |
877 | hrtimer_add_expires_ns(&ts->sched_timer, offset); | |
878 | } | |
879 | ||
79bf2bb3 TG |
880 | for (;;) { |
881 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
5c333864 AB |
882 | hrtimer_start_expires(&ts->sched_timer, |
883 | HRTIMER_MODE_ABS_PINNED); | |
79bf2bb3 TG |
884 | /* Check, if the timer was already in the past */ |
885 | if (hrtimer_active(&ts->sched_timer)) | |
886 | break; | |
887 | now = ktime_get(); | |
888 | } | |
889 | ||
890 | #ifdef CONFIG_NO_HZ | |
29c158e8 | 891 | if (tick_nohz_enabled) |
79bf2bb3 TG |
892 | ts->nohz_mode = NOHZ_MODE_HIGHRES; |
893 | #endif | |
894 | } | |
3c4fbe5e | 895 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 896 | |
3c4fbe5e | 897 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
898 | void tick_cancel_sched_timer(int cpu) |
899 | { | |
900 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
901 | ||
3c4fbe5e | 902 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
903 | if (ts->sched_timer.base) |
904 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 905 | # endif |
a7901766 | 906 | |
79bf2bb3 TG |
907 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
908 | } | |
3c4fbe5e | 909 | #endif |
79bf2bb3 TG |
910 | |
911 | /** | |
912 | * Async notification about clocksource changes | |
913 | */ | |
914 | void tick_clock_notify(void) | |
915 | { | |
916 | int cpu; | |
917 | ||
918 | for_each_possible_cpu(cpu) | |
919 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
920 | } | |
921 | ||
922 | /* | |
923 | * Async notification about clock event changes | |
924 | */ | |
925 | void tick_oneshot_notify(void) | |
926 | { | |
927 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
928 | ||
929 | set_bit(0, &ts->check_clocks); | |
930 | } | |
931 | ||
932 | /** | |
933 | * Check, if a change happened, which makes oneshot possible. | |
934 | * | |
935 | * Called cyclic from the hrtimer softirq (driven by the timer | |
936 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
937 | * mode, because high resolution timers are disabled (either compile | |
938 | * or runtime). | |
939 | */ | |
940 | int tick_check_oneshot_change(int allow_nohz) | |
941 | { | |
942 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
943 | ||
944 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
945 | return 0; | |
946 | ||
947 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
948 | return 0; | |
949 | ||
cf4fc6cb | 950 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
951 | return 0; |
952 | ||
953 | if (!allow_nohz) | |
954 | return 1; | |
955 | ||
956 | tick_nohz_switch_to_nohz(); | |
957 | return 0; | |
958 | } |