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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> | |
8083e4ad | 23 | #include <linux/module.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 | */ | |
32 | static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); | |
33 | ||
34 | /* | |
35 | * The time, when the last jiffy update happened. Protected by xtime_lock. | |
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 IM |
52 | /* |
53 | * Do a quick check without holding xtime_lock: | |
54 | */ | |
55 | delta = ktime_sub(now, last_jiffies_update); | |
56 | if (delta.tv64 < tick_period.tv64) | |
57 | return; | |
58 | ||
79bf2bb3 TG |
59 | /* Reevalute with xtime_lock held */ |
60 | write_seqlock(&xtime_lock); | |
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 TG |
82 | } |
83 | write_sequnlock(&xtime_lock); | |
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 | ||
93 | write_seqlock(&xtime_lock); | |
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; | |
98 | write_sequnlock(&xtime_lock); | |
99 | return period; | |
100 | } | |
101 | ||
102 | /* | |
103 | * NOHZ - aka dynamic tick functionality | |
104 | */ | |
105 | #ifdef CONFIG_NO_HZ | |
106 | /* | |
107 | * NO HZ enabled ? | |
108 | */ | |
109 | static int tick_nohz_enabled __read_mostly = 1; | |
110 | ||
111 | /* | |
112 | * Enable / Disable tickless mode | |
113 | */ | |
114 | static int __init setup_tick_nohz(char *str) | |
115 | { | |
116 | if (!strcmp(str, "off")) | |
117 | tick_nohz_enabled = 0; | |
118 | else if (!strcmp(str, "on")) | |
119 | tick_nohz_enabled = 1; | |
120 | else | |
121 | return 0; | |
122 | return 1; | |
123 | } | |
124 | ||
125 | __setup("nohz=", setup_tick_nohz); | |
126 | ||
127 | /** | |
128 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
129 | * | |
130 | * Called from interrupt entry when the CPU was idle | |
131 | * | |
132 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
133 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
134 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
135 | * cpu, which has the update task assigned is in a long sleep. | |
136 | */ | |
eed3b9cf | 137 | static void tick_nohz_update_jiffies(ktime_t now) |
79bf2bb3 TG |
138 | { |
139 | int cpu = smp_processor_id(); | |
140 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
141 | unsigned long flags; | |
79bf2bb3 | 142 | |
6a7b3dc3 | 143 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
5df7fa1c | 144 | ts->idle_waketime = now; |
79bf2bb3 TG |
145 | |
146 | local_irq_save(flags); | |
147 | tick_do_update_jiffies64(now); | |
148 | local_irq_restore(flags); | |
02ff3755 IM |
149 | |
150 | touch_softlockup_watchdog(); | |
79bf2bb3 TG |
151 | } |
152 | ||
eed3b9cf | 153 | static void tick_nohz_stop_idle(int cpu, ktime_t now) |
6378ddb5 VP |
154 | { |
155 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
eed3b9cf | 156 | ktime_t delta; |
6378ddb5 | 157 | |
eed3b9cf MS |
158 | delta = ktime_sub(now, ts->idle_entrytime); |
159 | ts->idle_lastupdate = now; | |
160 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
161 | ts->idle_active = 0; | |
56c7426b | 162 | |
eed3b9cf | 163 | sched_clock_idle_wakeup_event(0); |
6378ddb5 VP |
164 | } |
165 | ||
903b8a8d | 166 | static ktime_t tick_nohz_start_idle(struct tick_sched *ts) |
6378ddb5 | 167 | { |
6378ddb5 VP |
168 | ktime_t now, delta; |
169 | ||
170 | now = ktime_get(); | |
171 | if (ts->idle_active) { | |
172 | delta = ktime_sub(now, ts->idle_entrytime); | |
173 | ts->idle_lastupdate = now; | |
174 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
175 | } | |
176 | ts->idle_entrytime = now; | |
177 | ts->idle_active = 1; | |
56c7426b | 178 | sched_clock_idle_sleep_event(); |
6378ddb5 VP |
179 | return now; |
180 | } | |
181 | ||
182 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) | |
183 | { | |
184 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
185 | ||
8083e4ad | 186 | if (!tick_nohz_enabled) |
187 | return -1; | |
188 | ||
189 | if (ts->idle_active) | |
190 | *last_update_time = ktime_to_us(ts->idle_lastupdate); | |
191 | else | |
192 | *last_update_time = ktime_to_us(ktime_get()); | |
193 | ||
6378ddb5 VP |
194 | return ktime_to_us(ts->idle_sleeptime); |
195 | } | |
8083e4ad | 196 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
6378ddb5 | 197 | |
79bf2bb3 TG |
198 | /** |
199 | * tick_nohz_stop_sched_tick - stop the idle tick from the idle task | |
200 | * | |
201 | * When the next event is more than a tick into the future, stop the idle tick | |
202 | * Called either from the idle loop or from irq_exit() when an idle period was | |
203 | * just interrupted by an interrupt which did not cause a reschedule. | |
204 | */ | |
b8f8c3cf | 205 | void tick_nohz_stop_sched_tick(int inidle) |
79bf2bb3 TG |
206 | { |
207 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags; | |
208 | struct tick_sched *ts; | |
6378ddb5 | 209 | ktime_t last_update, expires, now; |
4f86d3a8 | 210 | struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; |
79bf2bb3 TG |
211 | int cpu; |
212 | ||
213 | local_irq_save(flags); | |
214 | ||
215 | cpu = smp_processor_id(); | |
216 | ts = &per_cpu(tick_cpu_sched, cpu); | |
f2e21c96 EN |
217 | |
218 | /* | |
219 | * Call to tick_nohz_start_idle stops the last_update_time from being | |
220 | * updated. Thus, it must not be called in the event we are called from | |
221 | * irq_exit() with the prior state different than idle. | |
222 | */ | |
223 | if (!inidle && !ts->inidle) | |
224 | goto end; | |
225 | ||
903b8a8d | 226 | now = tick_nohz_start_idle(ts); |
79bf2bb3 | 227 | |
5e41d0d6 TG |
228 | /* |
229 | * If this cpu is offline and it is the one which updates | |
230 | * jiffies, then give up the assignment and let it be taken by | |
231 | * the cpu which runs the tick timer next. If we don't drop | |
232 | * this here the jiffies might be stale and do_timer() never | |
233 | * invoked. | |
234 | */ | |
235 | if (unlikely(!cpu_online(cpu))) { | |
236 | if (cpu == tick_do_timer_cpu) | |
6441402b | 237 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
5e41d0d6 TG |
238 | } |
239 | ||
79bf2bb3 TG |
240 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
241 | goto end; | |
242 | ||
b8f8c3cf TG |
243 | ts->inidle = 1; |
244 | ||
79bf2bb3 TG |
245 | if (need_resched()) |
246 | goto end; | |
247 | ||
fa116ea3 | 248 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { |
35282316 TG |
249 | static int ratelimit; |
250 | ||
251 | if (ratelimit < 10) { | |
252 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", | |
253 | local_softirq_pending()); | |
254 | ratelimit++; | |
255 | } | |
857f3fd7 | 256 | goto end; |
35282316 | 257 | } |
79bf2bb3 | 258 | |
79bf2bb3 | 259 | ts->idle_calls++; |
79bf2bb3 TG |
260 | /* Read jiffies and the time when jiffies were updated last */ |
261 | do { | |
262 | seq = read_seqbegin(&xtime_lock); | |
263 | last_update = last_jiffies_update; | |
264 | last_jiffies = jiffies; | |
265 | } while (read_seqretry(&xtime_lock, seq)); | |
266 | ||
3c5d92a0 MS |
267 | if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || |
268 | arch_needs_cpu(cpu)) { | |
269 | next_jiffies = last_jiffies + 1; | |
6ba9b346 | 270 | delta_jiffies = 1; |
3c5d92a0 MS |
271 | } else { |
272 | /* Get the next timer wheel timer */ | |
273 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
274 | delta_jiffies = next_jiffies - last_jiffies; | |
275 | } | |
79bf2bb3 TG |
276 | /* |
277 | * Do not stop the tick, if we are only one off | |
278 | * or if the cpu is required for rcu | |
279 | */ | |
6ba9b346 | 280 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
281 | goto out; |
282 | ||
283 | /* Schedule the tick, if we are at least one jiffie off */ | |
284 | if ((long)delta_jiffies >= 1) { | |
285 | ||
00147449 WR |
286 | /* |
287 | * calculate the expiry time for the next timer wheel | |
288 | * timer | |
289 | */ | |
290 | expires = ktime_add_ns(last_update, tick_period.tv64 * | |
291 | delta_jiffies); | |
292 | ||
293 | /* | |
294 | * If this cpu is the one which updates jiffies, then | |
295 | * give up the assignment and let it be taken by the | |
296 | * cpu which runs the tick timer next, which might be | |
297 | * this cpu as well. If we don't drop this here the | |
298 | * jiffies might be stale and do_timer() never | |
299 | * invoked. | |
300 | */ | |
301 | if (cpu == tick_do_timer_cpu) | |
302 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
303 | ||
6ba9b346 | 304 | if (delta_jiffies > 1) |
6a7b3dc3 | 305 | cpumask_set_cpu(cpu, nohz_cpu_mask); |
00147449 WR |
306 | |
307 | /* Skip reprogram of event if its not changed */ | |
308 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) | |
309 | goto out; | |
310 | ||
79bf2bb3 TG |
311 | /* |
312 | * nohz_stop_sched_tick can be called several times before | |
313 | * the nohz_restart_sched_tick is called. This happens when | |
314 | * interrupts arrive which do not cause a reschedule. In the | |
315 | * first call we save the current tick time, so we can restart | |
316 | * the scheduler tick in nohz_restart_sched_tick. | |
317 | */ | |
318 | if (!ts->tick_stopped) { | |
46cb4b7c SS |
319 | if (select_nohz_load_balancer(1)) { |
320 | /* | |
321 | * sched tick not stopped! | |
322 | */ | |
6a7b3dc3 | 323 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
46cb4b7c SS |
324 | goto out; |
325 | } | |
326 | ||
cc584b21 | 327 | ts->idle_tick = hrtimer_get_expires(&ts->sched_timer); |
79bf2bb3 TG |
328 | ts->tick_stopped = 1; |
329 | ts->idle_jiffies = last_jiffies; | |
2232c2d8 | 330 | rcu_enter_nohz(); |
79bf2bb3 | 331 | } |
d3ed7824 | 332 | |
eaad084b TG |
333 | ts->idle_sleeps++; |
334 | ||
335 | /* | |
336 | * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that | |
337 | * there is no timer pending or at least extremly far | |
338 | * into the future (12 days for HZ=1000). In this case | |
339 | * we simply stop the tick timer: | |
340 | */ | |
341 | if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) { | |
342 | ts->idle_expires.tv64 = KTIME_MAX; | |
343 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) | |
344 | hrtimer_cancel(&ts->sched_timer); | |
345 | goto out; | |
346 | } | |
347 | ||
00147449 | 348 | /* Mark expiries */ |
79bf2bb3 | 349 | ts->idle_expires = expires; |
79bf2bb3 TG |
350 | |
351 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
352 | hrtimer_start(&ts->sched_timer, expires, | |
5c333864 | 353 | HRTIMER_MODE_ABS_PINNED); |
79bf2bb3 TG |
354 | /* Check, if the timer was already in the past */ |
355 | if (hrtimer_active(&ts->sched_timer)) | |
356 | goto out; | |
4c9dc641 | 357 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
358 | goto out; |
359 | /* | |
360 | * We are past the event already. So we crossed a | |
361 | * jiffie boundary. Update jiffies and raise the | |
362 | * softirq. | |
363 | */ | |
364 | tick_do_update_jiffies64(ktime_get()); | |
6a7b3dc3 | 365 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
79bf2bb3 TG |
366 | } |
367 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
368 | out: | |
369 | ts->next_jiffies = next_jiffies; | |
370 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 371 | ts->sleep_length = ktime_sub(dev->next_event, now); |
79bf2bb3 TG |
372 | end: |
373 | local_irq_restore(flags); | |
374 | } | |
375 | ||
4f86d3a8 LB |
376 | /** |
377 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
378 | * | |
379 | * Called from power state control code with interrupts disabled | |
380 | */ | |
381 | ktime_t tick_nohz_get_sleep_length(void) | |
382 | { | |
383 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
384 | ||
385 | return ts->sleep_length; | |
386 | } | |
387 | ||
c34bec5a TG |
388 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
389 | { | |
390 | hrtimer_cancel(&ts->sched_timer); | |
268a3dcf | 391 | hrtimer_set_expires(&ts->sched_timer, ts->idle_tick); |
c34bec5a TG |
392 | |
393 | while (1) { | |
394 | /* Forward the time to expire in the future */ | |
395 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
396 | ||
397 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
268a3dcf | 398 | hrtimer_start_expires(&ts->sched_timer, |
5c333864 | 399 | HRTIMER_MODE_ABS_PINNED); |
c34bec5a TG |
400 | /* Check, if the timer was already in the past */ |
401 | if (hrtimer_active(&ts->sched_timer)) | |
402 | break; | |
403 | } else { | |
268a3dcf TG |
404 | if (!tick_program_event( |
405 | hrtimer_get_expires(&ts->sched_timer), 0)) | |
c34bec5a TG |
406 | break; |
407 | } | |
408 | /* Update jiffies and reread time */ | |
409 | tick_do_update_jiffies64(now); | |
410 | now = ktime_get(); | |
411 | } | |
412 | } | |
413 | ||
79bf2bb3 | 414 | /** |
8dce39c2 | 415 | * tick_nohz_restart_sched_tick - restart the idle tick from the idle task |
79bf2bb3 TG |
416 | * |
417 | * Restart the idle tick when the CPU is woken up from idle | |
418 | */ | |
419 | void tick_nohz_restart_sched_tick(void) | |
420 | { | |
421 | int cpu = smp_processor_id(); | |
422 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
79741dd3 | 423 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
79bf2bb3 | 424 | unsigned long ticks; |
79741dd3 | 425 | #endif |
6378ddb5 | 426 | ktime_t now; |
79bf2bb3 | 427 | |
6378ddb5 | 428 | local_irq_disable(); |
eed3b9cf MS |
429 | if (ts->idle_active || (ts->inidle && ts->tick_stopped)) |
430 | now = ktime_get(); | |
431 | ||
432 | if (ts->idle_active) | |
433 | tick_nohz_stop_idle(cpu, now); | |
6378ddb5 | 434 | |
b8f8c3cf TG |
435 | if (!ts->inidle || !ts->tick_stopped) { |
436 | ts->inidle = 0; | |
6378ddb5 | 437 | local_irq_enable(); |
79bf2bb3 | 438 | return; |
6378ddb5 | 439 | } |
79bf2bb3 | 440 | |
b8f8c3cf TG |
441 | ts->inidle = 0; |
442 | ||
2232c2d8 SR |
443 | rcu_exit_nohz(); |
444 | ||
79bf2bb3 | 445 | /* Update jiffies first */ |
46cb4b7c | 446 | select_nohz_load_balancer(0); |
79bf2bb3 | 447 | tick_do_update_jiffies64(now); |
6a7b3dc3 | 448 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
79bf2bb3 | 449 | |
79741dd3 | 450 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
79bf2bb3 TG |
451 | /* |
452 | * We stopped the tick in idle. Update process times would miss the | |
453 | * time we slept as update_process_times does only a 1 tick | |
454 | * accounting. Enforce that this is accounted to idle ! | |
455 | */ | |
456 | ticks = jiffies - ts->idle_jiffies; | |
457 | /* | |
458 | * We might be one off. Do not randomly account a huge number of ticks! | |
459 | */ | |
79741dd3 MS |
460 | if (ticks && ticks < LONG_MAX) |
461 | account_idle_ticks(ticks); | |
462 | #endif | |
79bf2bb3 | 463 | |
126e01bf | 464 | touch_softlockup_watchdog(); |
79bf2bb3 TG |
465 | /* |
466 | * Cancel the scheduled timer and restore the tick | |
467 | */ | |
468 | ts->tick_stopped = 0; | |
5df7fa1c | 469 | ts->idle_exittime = now; |
79bf2bb3 | 470 | |
c34bec5a | 471 | tick_nohz_restart(ts, now); |
79bf2bb3 | 472 | |
79bf2bb3 TG |
473 | local_irq_enable(); |
474 | } | |
475 | ||
476 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
477 | { | |
478 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
cc584b21 | 479 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
79bf2bb3 TG |
480 | } |
481 | ||
482 | /* | |
483 | * The nohz low res interrupt handler | |
484 | */ | |
485 | static void tick_nohz_handler(struct clock_event_device *dev) | |
486 | { | |
487 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
488 | struct pt_regs *regs = get_irq_regs(); | |
d3ed7824 | 489 | int cpu = smp_processor_id(); |
79bf2bb3 TG |
490 | ktime_t now = ktime_get(); |
491 | ||
492 | dev->next_event.tv64 = KTIME_MAX; | |
493 | ||
d3ed7824 TG |
494 | /* |
495 | * Check if the do_timer duty was dropped. We don't care about | |
496 | * concurrency: This happens only when the cpu in charge went | |
497 | * into a long sleep. If two cpus happen to assign themself to | |
498 | * this duty, then the jiffies update is still serialized by | |
499 | * xtime_lock. | |
500 | */ | |
6441402b | 501 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
502 | tick_do_timer_cpu = cpu; |
503 | ||
79bf2bb3 | 504 | /* Check, if the jiffies need an update */ |
d3ed7824 TG |
505 | if (tick_do_timer_cpu == cpu) |
506 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
507 | |
508 | /* | |
509 | * When we are idle and the tick is stopped, we have to touch | |
510 | * the watchdog as we might not schedule for a really long | |
511 | * time. This happens on complete idle SMP systems while | |
512 | * waiting on the login prompt. We also increment the "start | |
513 | * of idle" jiffy stamp so the idle accounting adjustment we | |
514 | * do when we go busy again does not account too much ticks. | |
515 | */ | |
516 | if (ts->tick_stopped) { | |
517 | touch_softlockup_watchdog(); | |
518 | ts->idle_jiffies++; | |
519 | } | |
520 | ||
521 | update_process_times(user_mode(regs)); | |
522 | profile_tick(CPU_PROFILING); | |
523 | ||
79bf2bb3 TG |
524 | while (tick_nohz_reprogram(ts, now)) { |
525 | now = ktime_get(); | |
526 | tick_do_update_jiffies64(now); | |
527 | } | |
528 | } | |
529 | ||
530 | /** | |
531 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
532 | */ | |
533 | static void tick_nohz_switch_to_nohz(void) | |
534 | { | |
535 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
536 | ktime_t next; | |
537 | ||
538 | if (!tick_nohz_enabled) | |
539 | return; | |
540 | ||
541 | local_irq_disable(); | |
542 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
543 | local_irq_enable(); | |
544 | return; | |
545 | } | |
546 | ||
547 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
548 | ||
549 | /* | |
550 | * Recycle the hrtimer in ts, so we can share the | |
551 | * hrtimer_forward with the highres code. | |
552 | */ | |
553 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
554 | /* Get the next period */ | |
555 | next = tick_init_jiffy_update(); | |
556 | ||
557 | for (;;) { | |
cc584b21 | 558 | hrtimer_set_expires(&ts->sched_timer, next); |
79bf2bb3 TG |
559 | if (!tick_program_event(next, 0)) |
560 | break; | |
561 | next = ktime_add(next, tick_period); | |
562 | } | |
563 | local_irq_enable(); | |
564 | ||
565 | printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", | |
566 | smp_processor_id()); | |
567 | } | |
568 | ||
fb02fbc1 TG |
569 | /* |
570 | * When NOHZ is enabled and the tick is stopped, we need to kick the | |
571 | * tick timer from irq_enter() so that the jiffies update is kept | |
572 | * alive during long running softirqs. That's ugly as hell, but | |
573 | * correctness is key even if we need to fix the offending softirq in | |
574 | * the first place. | |
575 | * | |
576 | * Note, this is different to tick_nohz_restart. We just kick the | |
577 | * timer and do not touch the other magic bits which need to be done | |
578 | * when idle is left. | |
579 | */ | |
eed3b9cf | 580 | static void tick_nohz_kick_tick(int cpu, ktime_t now) |
fb02fbc1 | 581 | { |
ae99286b TG |
582 | #if 0 |
583 | /* Switch back to 2.6.27 behaviour */ | |
584 | ||
fb02fbc1 | 585 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
eed3b9cf | 586 | ktime_t delta; |
fb02fbc1 | 587 | |
c4bd822e TG |
588 | /* |
589 | * Do not touch the tick device, when the next expiry is either | |
590 | * already reached or less/equal than the tick period. | |
591 | */ | |
268a3dcf | 592 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
c4bd822e TG |
593 | if (delta.tv64 <= tick_period.tv64) |
594 | return; | |
595 | ||
596 | tick_nohz_restart(ts, now); | |
ae99286b | 597 | #endif |
fb02fbc1 TG |
598 | } |
599 | ||
eed3b9cf MS |
600 | static inline void tick_check_nohz(int cpu) |
601 | { | |
602 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
603 | ktime_t now; | |
604 | ||
605 | if (!ts->idle_active && !ts->tick_stopped) | |
606 | return; | |
607 | now = ktime_get(); | |
608 | if (ts->idle_active) | |
609 | tick_nohz_stop_idle(cpu, now); | |
610 | if (ts->tick_stopped) { | |
611 | tick_nohz_update_jiffies(now); | |
612 | tick_nohz_kick_tick(cpu, now); | |
613 | } | |
614 | } | |
615 | ||
79bf2bb3 TG |
616 | #else |
617 | ||
618 | static inline void tick_nohz_switch_to_nohz(void) { } | |
eed3b9cf | 619 | static inline void tick_check_nohz(int cpu) { } |
79bf2bb3 TG |
620 | |
621 | #endif /* NO_HZ */ | |
622 | ||
719254fa TG |
623 | /* |
624 | * Called from irq_enter to notify about the possible interruption of idle() | |
625 | */ | |
626 | void tick_check_idle(int cpu) | |
627 | { | |
fb02fbc1 | 628 | tick_check_oneshot_broadcast(cpu); |
eed3b9cf | 629 | tick_check_nohz(cpu); |
719254fa TG |
630 | } |
631 | ||
79bf2bb3 TG |
632 | /* |
633 | * High resolution timer specific code | |
634 | */ | |
635 | #ifdef CONFIG_HIGH_RES_TIMERS | |
636 | /* | |
4c9dc641 | 637 | * We rearm the timer until we get disabled by the idle code. |
79bf2bb3 TG |
638 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
639 | */ | |
640 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
641 | { | |
642 | struct tick_sched *ts = | |
643 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
644 | struct pt_regs *regs = get_irq_regs(); |
645 | ktime_t now = ktime_get(); | |
d3ed7824 TG |
646 | int cpu = smp_processor_id(); |
647 | ||
648 | #ifdef CONFIG_NO_HZ | |
649 | /* | |
650 | * Check if the do_timer duty was dropped. We don't care about | |
651 | * concurrency: This happens only when the cpu in charge went | |
652 | * into a long sleep. If two cpus happen to assign themself to | |
653 | * this duty, then the jiffies update is still serialized by | |
654 | * xtime_lock. | |
655 | */ | |
6441402b | 656 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
657 | tick_do_timer_cpu = cpu; |
658 | #endif | |
79bf2bb3 TG |
659 | |
660 | /* Check, if the jiffies need an update */ | |
d3ed7824 TG |
661 | if (tick_do_timer_cpu == cpu) |
662 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
663 | |
664 | /* | |
665 | * Do not call, when we are not in irq context and have | |
666 | * no valid regs pointer | |
667 | */ | |
668 | if (regs) { | |
669 | /* | |
670 | * When we are idle and the tick is stopped, we have to touch | |
671 | * the watchdog as we might not schedule for a really long | |
672 | * time. This happens on complete idle SMP systems while | |
673 | * waiting on the login prompt. We also increment the "start of | |
674 | * idle" jiffy stamp so the idle accounting adjustment we do | |
675 | * when we go busy again does not account too much ticks. | |
676 | */ | |
677 | if (ts->tick_stopped) { | |
678 | touch_softlockup_watchdog(); | |
679 | ts->idle_jiffies++; | |
680 | } | |
79bf2bb3 TG |
681 | update_process_times(user_mode(regs)); |
682 | profile_tick(CPU_PROFILING); | |
79bf2bb3 TG |
683 | } |
684 | ||
79bf2bb3 TG |
685 | hrtimer_forward(timer, now, tick_period); |
686 | ||
687 | return HRTIMER_RESTART; | |
688 | } | |
689 | ||
690 | /** | |
691 | * tick_setup_sched_timer - setup the tick emulation timer | |
692 | */ | |
693 | void tick_setup_sched_timer(void) | |
694 | { | |
695 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
696 | ktime_t now = ktime_get(); | |
3704540b | 697 | u64 offset; |
79bf2bb3 TG |
698 | |
699 | /* | |
700 | * Emulate tick processing via per-CPU hrtimers: | |
701 | */ | |
702 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
703 | ts->sched_timer.function = tick_sched_timer; | |
79bf2bb3 | 704 | |
3704540b | 705 | /* Get the next period (per cpu) */ |
cc584b21 | 706 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
3704540b | 707 | offset = ktime_to_ns(tick_period) >> 1; |
b2d9323d | 708 | do_div(offset, num_possible_cpus()); |
3704540b | 709 | offset *= smp_processor_id(); |
cc584b21 | 710 | hrtimer_add_expires_ns(&ts->sched_timer, offset); |
79bf2bb3 TG |
711 | |
712 | for (;;) { | |
713 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
5c333864 AB |
714 | hrtimer_start_expires(&ts->sched_timer, |
715 | HRTIMER_MODE_ABS_PINNED); | |
79bf2bb3 TG |
716 | /* Check, if the timer was already in the past */ |
717 | if (hrtimer_active(&ts->sched_timer)) | |
718 | break; | |
719 | now = ktime_get(); | |
720 | } | |
721 | ||
722 | #ifdef CONFIG_NO_HZ | |
723 | if (tick_nohz_enabled) | |
724 | ts->nohz_mode = NOHZ_MODE_HIGHRES; | |
725 | #endif | |
726 | } | |
3c4fbe5e | 727 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 728 | |
3c4fbe5e | 729 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
730 | void tick_cancel_sched_timer(int cpu) |
731 | { | |
732 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
733 | ||
3c4fbe5e | 734 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
735 | if (ts->sched_timer.base) |
736 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 737 | # endif |
a7901766 | 738 | |
79bf2bb3 TG |
739 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
740 | } | |
3c4fbe5e | 741 | #endif |
79bf2bb3 TG |
742 | |
743 | /** | |
744 | * Async notification about clocksource changes | |
745 | */ | |
746 | void tick_clock_notify(void) | |
747 | { | |
748 | int cpu; | |
749 | ||
750 | for_each_possible_cpu(cpu) | |
751 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
752 | } | |
753 | ||
754 | /* | |
755 | * Async notification about clock event changes | |
756 | */ | |
757 | void tick_oneshot_notify(void) | |
758 | { | |
759 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
760 | ||
761 | set_bit(0, &ts->check_clocks); | |
762 | } | |
763 | ||
764 | /** | |
765 | * Check, if a change happened, which makes oneshot possible. | |
766 | * | |
767 | * Called cyclic from the hrtimer softirq (driven by the timer | |
768 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
769 | * mode, because high resolution timers are disabled (either compile | |
770 | * or runtime). | |
771 | */ | |
772 | int tick_check_oneshot_change(int allow_nohz) | |
773 | { | |
774 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
775 | ||
776 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
777 | return 0; | |
778 | ||
779 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
780 | return 0; | |
781 | ||
cf4fc6cb | 782 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
783 | return 0; |
784 | ||
785 | if (!allow_nohz) | |
786 | return 1; | |
787 | ||
788 | tick_nohz_switch_to_nohz(); | |
789 | return 0; | |
790 | } |