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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; |
98962465 | 211 | u64 time_delta; |
79bf2bb3 TG |
212 | int cpu; |
213 | ||
214 | local_irq_save(flags); | |
215 | ||
216 | cpu = smp_processor_id(); | |
217 | ts = &per_cpu(tick_cpu_sched, cpu); | |
f2e21c96 EN |
218 | |
219 | /* | |
220 | * Call to tick_nohz_start_idle stops the last_update_time from being | |
221 | * updated. Thus, it must not be called in the event we are called from | |
222 | * irq_exit() with the prior state different than idle. | |
223 | */ | |
224 | if (!inidle && !ts->inidle) | |
225 | goto end; | |
226 | ||
fdc6f192 EN |
227 | /* |
228 | * Set ts->inidle unconditionally. Even if the system did not | |
229 | * switch to NOHZ mode the cpu frequency governers rely on the | |
230 | * update of the idle time accounting in tick_nohz_start_idle(). | |
231 | */ | |
232 | ts->inidle = 1; | |
233 | ||
903b8a8d | 234 | now = tick_nohz_start_idle(ts); |
79bf2bb3 | 235 | |
5e41d0d6 TG |
236 | /* |
237 | * If this cpu is offline and it is the one which updates | |
238 | * jiffies, then give up the assignment and let it be taken by | |
239 | * the cpu which runs the tick timer next. If we don't drop | |
240 | * this here the jiffies might be stale and do_timer() never | |
241 | * invoked. | |
242 | */ | |
243 | if (unlikely(!cpu_online(cpu))) { | |
244 | if (cpu == tick_do_timer_cpu) | |
6441402b | 245 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
5e41d0d6 TG |
246 | } |
247 | ||
79bf2bb3 TG |
248 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
249 | goto end; | |
250 | ||
251 | if (need_resched()) | |
252 | goto end; | |
253 | ||
fa116ea3 | 254 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { |
35282316 TG |
255 | static int ratelimit; |
256 | ||
257 | if (ratelimit < 10) { | |
258 | printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", | |
529eaccd | 259 | (unsigned int) local_softirq_pending()); |
35282316 TG |
260 | ratelimit++; |
261 | } | |
857f3fd7 | 262 | goto end; |
35282316 | 263 | } |
79bf2bb3 | 264 | |
39c0cbe2 MG |
265 | if (nohz_ratelimit(cpu)) |
266 | goto end; | |
267 | ||
79bf2bb3 | 268 | ts->idle_calls++; |
79bf2bb3 TG |
269 | /* Read jiffies and the time when jiffies were updated last */ |
270 | do { | |
271 | seq = read_seqbegin(&xtime_lock); | |
272 | last_update = last_jiffies_update; | |
273 | last_jiffies = jiffies; | |
27185016 | 274 | time_delta = timekeeping_max_deferment(); |
79bf2bb3 TG |
275 | } while (read_seqretry(&xtime_lock, seq)); |
276 | ||
3c5d92a0 MS |
277 | if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || |
278 | arch_needs_cpu(cpu)) { | |
279 | next_jiffies = last_jiffies + 1; | |
6ba9b346 | 280 | delta_jiffies = 1; |
3c5d92a0 MS |
281 | } else { |
282 | /* Get the next timer wheel timer */ | |
283 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
284 | delta_jiffies = next_jiffies - last_jiffies; | |
285 | } | |
79bf2bb3 TG |
286 | /* |
287 | * Do not stop the tick, if we are only one off | |
288 | * or if the cpu is required for rcu | |
289 | */ | |
6ba9b346 | 290 | if (!ts->tick_stopped && delta_jiffies == 1) |
79bf2bb3 TG |
291 | goto out; |
292 | ||
293 | /* Schedule the tick, if we are at least one jiffie off */ | |
294 | if ((long)delta_jiffies >= 1) { | |
295 | ||
00147449 WR |
296 | /* |
297 | * If this cpu is the one which updates jiffies, then | |
298 | * give up the assignment and let it be taken by the | |
299 | * cpu which runs the tick timer next, which might be | |
300 | * this cpu as well. If we don't drop this here the | |
301 | * jiffies might be stale and do_timer() never | |
27185016 TG |
302 | * invoked. Keep track of the fact that it was the one |
303 | * which had the do_timer() duty last. If this cpu is | |
304 | * the one which had the do_timer() duty last, we | |
305 | * limit the sleep time to the timekeeping | |
306 | * max_deferement value which we retrieved | |
307 | * above. Otherwise we can sleep as long as we want. | |
00147449 | 308 | */ |
27185016 | 309 | if (cpu == tick_do_timer_cpu) { |
00147449 | 310 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
27185016 TG |
311 | ts->do_timer_last = 1; |
312 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { | |
313 | time_delta = KTIME_MAX; | |
314 | ts->do_timer_last = 0; | |
315 | } else if (!ts->do_timer_last) { | |
316 | time_delta = KTIME_MAX; | |
317 | } | |
318 | ||
00147449 | 319 | /* |
98962465 JH |
320 | * calculate the expiry time for the next timer wheel |
321 | * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals | |
322 | * that there is no timer pending or at least extremely | |
323 | * far into the future (12 days for HZ=1000). In this | |
324 | * case we set the expiry to the end of time. | |
325 | */ | |
326 | if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) { | |
327 | /* | |
328 | * Calculate the time delta for the next timer event. | |
329 | * If the time delta exceeds the maximum time delta | |
330 | * permitted by the current clocksource then adjust | |
331 | * the time delta accordingly to ensure the | |
332 | * clocksource does not wrap. | |
333 | */ | |
334 | time_delta = min_t(u64, time_delta, | |
335 | tick_period.tv64 * delta_jiffies); | |
98962465 | 336 | } |
00147449 | 337 | |
27185016 TG |
338 | if (time_delta < KTIME_MAX) |
339 | expires = ktime_add_ns(last_update, time_delta); | |
340 | else | |
341 | expires.tv64 = KTIME_MAX; | |
00147449 | 342 | |
6ba9b346 | 343 | if (delta_jiffies > 1) |
6a7b3dc3 | 344 | cpumask_set_cpu(cpu, nohz_cpu_mask); |
00147449 WR |
345 | |
346 | /* Skip reprogram of event if its not changed */ | |
347 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) | |
348 | goto out; | |
349 | ||
79bf2bb3 TG |
350 | /* |
351 | * nohz_stop_sched_tick can be called several times before | |
352 | * the nohz_restart_sched_tick is called. This happens when | |
353 | * interrupts arrive which do not cause a reschedule. In the | |
354 | * first call we save the current tick time, so we can restart | |
355 | * the scheduler tick in nohz_restart_sched_tick. | |
356 | */ | |
357 | if (!ts->tick_stopped) { | |
46cb4b7c SS |
358 | if (select_nohz_load_balancer(1)) { |
359 | /* | |
360 | * sched tick not stopped! | |
361 | */ | |
6a7b3dc3 | 362 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
46cb4b7c SS |
363 | goto out; |
364 | } | |
365 | ||
cc584b21 | 366 | ts->idle_tick = hrtimer_get_expires(&ts->sched_timer); |
79bf2bb3 TG |
367 | ts->tick_stopped = 1; |
368 | ts->idle_jiffies = last_jiffies; | |
2232c2d8 | 369 | rcu_enter_nohz(); |
79bf2bb3 | 370 | } |
d3ed7824 | 371 | |
eaad084b TG |
372 | ts->idle_sleeps++; |
373 | ||
98962465 JH |
374 | /* Mark expires */ |
375 | ts->idle_expires = expires; | |
376 | ||
eaad084b | 377 | /* |
98962465 JH |
378 | * If the expiration time == KTIME_MAX, then |
379 | * in this case we simply stop the tick timer. | |
eaad084b | 380 | */ |
98962465 | 381 | if (unlikely(expires.tv64 == KTIME_MAX)) { |
eaad084b TG |
382 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
383 | hrtimer_cancel(&ts->sched_timer); | |
384 | goto out; | |
385 | } | |
386 | ||
79bf2bb3 TG |
387 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
388 | hrtimer_start(&ts->sched_timer, expires, | |
5c333864 | 389 | HRTIMER_MODE_ABS_PINNED); |
79bf2bb3 TG |
390 | /* Check, if the timer was already in the past */ |
391 | if (hrtimer_active(&ts->sched_timer)) | |
392 | goto out; | |
4c9dc641 | 393 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
394 | goto out; |
395 | /* | |
396 | * We are past the event already. So we crossed a | |
397 | * jiffie boundary. Update jiffies and raise the | |
398 | * softirq. | |
399 | */ | |
400 | tick_do_update_jiffies64(ktime_get()); | |
6a7b3dc3 | 401 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
79bf2bb3 TG |
402 | } |
403 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
404 | out: | |
405 | ts->next_jiffies = next_jiffies; | |
406 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 407 | ts->sleep_length = ktime_sub(dev->next_event, now); |
79bf2bb3 TG |
408 | end: |
409 | local_irq_restore(flags); | |
410 | } | |
411 | ||
4f86d3a8 LB |
412 | /** |
413 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
414 | * | |
415 | * Called from power state control code with interrupts disabled | |
416 | */ | |
417 | ktime_t tick_nohz_get_sleep_length(void) | |
418 | { | |
419 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
420 | ||
421 | return ts->sleep_length; | |
422 | } | |
423 | ||
c34bec5a TG |
424 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
425 | { | |
426 | hrtimer_cancel(&ts->sched_timer); | |
268a3dcf | 427 | hrtimer_set_expires(&ts->sched_timer, ts->idle_tick); |
c34bec5a TG |
428 | |
429 | while (1) { | |
430 | /* Forward the time to expire in the future */ | |
431 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
432 | ||
433 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
268a3dcf | 434 | hrtimer_start_expires(&ts->sched_timer, |
5c333864 | 435 | HRTIMER_MODE_ABS_PINNED); |
c34bec5a TG |
436 | /* Check, if the timer was already in the past */ |
437 | if (hrtimer_active(&ts->sched_timer)) | |
438 | break; | |
439 | } else { | |
268a3dcf TG |
440 | if (!tick_program_event( |
441 | hrtimer_get_expires(&ts->sched_timer), 0)) | |
c34bec5a TG |
442 | break; |
443 | } | |
444 | /* Update jiffies and reread time */ | |
445 | tick_do_update_jiffies64(now); | |
446 | now = ktime_get(); | |
447 | } | |
448 | } | |
449 | ||
79bf2bb3 | 450 | /** |
8dce39c2 | 451 | * tick_nohz_restart_sched_tick - restart the idle tick from the idle task |
79bf2bb3 TG |
452 | * |
453 | * Restart the idle tick when the CPU is woken up from idle | |
454 | */ | |
455 | void tick_nohz_restart_sched_tick(void) | |
456 | { | |
457 | int cpu = smp_processor_id(); | |
458 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
79741dd3 | 459 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
79bf2bb3 | 460 | unsigned long ticks; |
79741dd3 | 461 | #endif |
6378ddb5 | 462 | ktime_t now; |
79bf2bb3 | 463 | |
6378ddb5 | 464 | local_irq_disable(); |
eed3b9cf MS |
465 | if (ts->idle_active || (ts->inidle && ts->tick_stopped)) |
466 | now = ktime_get(); | |
467 | ||
468 | if (ts->idle_active) | |
469 | tick_nohz_stop_idle(cpu, now); | |
6378ddb5 | 470 | |
b8f8c3cf TG |
471 | if (!ts->inidle || !ts->tick_stopped) { |
472 | ts->inidle = 0; | |
6378ddb5 | 473 | local_irq_enable(); |
79bf2bb3 | 474 | return; |
6378ddb5 | 475 | } |
79bf2bb3 | 476 | |
b8f8c3cf TG |
477 | ts->inidle = 0; |
478 | ||
2232c2d8 SR |
479 | rcu_exit_nohz(); |
480 | ||
79bf2bb3 | 481 | /* Update jiffies first */ |
46cb4b7c | 482 | select_nohz_load_balancer(0); |
79bf2bb3 | 483 | tick_do_update_jiffies64(now); |
6a7b3dc3 | 484 | cpumask_clear_cpu(cpu, nohz_cpu_mask); |
79bf2bb3 | 485 | |
79741dd3 | 486 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
79bf2bb3 TG |
487 | /* |
488 | * We stopped the tick in idle. Update process times would miss the | |
489 | * time we slept as update_process_times does only a 1 tick | |
490 | * accounting. Enforce that this is accounted to idle ! | |
491 | */ | |
492 | ticks = jiffies - ts->idle_jiffies; | |
493 | /* | |
494 | * We might be one off. Do not randomly account a huge number of ticks! | |
495 | */ | |
79741dd3 MS |
496 | if (ticks && ticks < LONG_MAX) |
497 | account_idle_ticks(ticks); | |
498 | #endif | |
79bf2bb3 | 499 | |
126e01bf | 500 | touch_softlockup_watchdog(); |
79bf2bb3 TG |
501 | /* |
502 | * Cancel the scheduled timer and restore the tick | |
503 | */ | |
504 | ts->tick_stopped = 0; | |
5df7fa1c | 505 | ts->idle_exittime = now; |
79bf2bb3 | 506 | |
c34bec5a | 507 | tick_nohz_restart(ts, now); |
79bf2bb3 | 508 | |
79bf2bb3 TG |
509 | local_irq_enable(); |
510 | } | |
511 | ||
512 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
513 | { | |
514 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
cc584b21 | 515 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
79bf2bb3 TG |
516 | } |
517 | ||
518 | /* | |
519 | * The nohz low res interrupt handler | |
520 | */ | |
521 | static void tick_nohz_handler(struct clock_event_device *dev) | |
522 | { | |
523 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
524 | struct pt_regs *regs = get_irq_regs(); | |
d3ed7824 | 525 | int cpu = smp_processor_id(); |
79bf2bb3 TG |
526 | ktime_t now = ktime_get(); |
527 | ||
528 | dev->next_event.tv64 = KTIME_MAX; | |
529 | ||
d3ed7824 TG |
530 | /* |
531 | * Check if the do_timer duty was dropped. We don't care about | |
532 | * concurrency: This happens only when the cpu in charge went | |
533 | * into a long sleep. If two cpus happen to assign themself to | |
534 | * this duty, then the jiffies update is still serialized by | |
535 | * xtime_lock. | |
536 | */ | |
6441402b | 537 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
538 | tick_do_timer_cpu = cpu; |
539 | ||
79bf2bb3 | 540 | /* Check, if the jiffies need an update */ |
d3ed7824 TG |
541 | if (tick_do_timer_cpu == cpu) |
542 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
543 | |
544 | /* | |
545 | * When we are idle and the tick is stopped, we have to touch | |
546 | * the watchdog as we might not schedule for a really long | |
547 | * time. This happens on complete idle SMP systems while | |
548 | * waiting on the login prompt. We also increment the "start | |
549 | * of idle" jiffy stamp so the idle accounting adjustment we | |
550 | * do when we go busy again does not account too much ticks. | |
551 | */ | |
552 | if (ts->tick_stopped) { | |
553 | touch_softlockup_watchdog(); | |
554 | ts->idle_jiffies++; | |
555 | } | |
556 | ||
557 | update_process_times(user_mode(regs)); | |
558 | profile_tick(CPU_PROFILING); | |
559 | ||
79bf2bb3 TG |
560 | while (tick_nohz_reprogram(ts, now)) { |
561 | now = ktime_get(); | |
562 | tick_do_update_jiffies64(now); | |
563 | } | |
564 | } | |
565 | ||
566 | /** | |
567 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
568 | */ | |
569 | static void tick_nohz_switch_to_nohz(void) | |
570 | { | |
571 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
572 | ktime_t next; | |
573 | ||
574 | if (!tick_nohz_enabled) | |
575 | return; | |
576 | ||
577 | local_irq_disable(); | |
578 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
579 | local_irq_enable(); | |
580 | return; | |
581 | } | |
582 | ||
583 | ts->nohz_mode = NOHZ_MODE_LOWRES; | |
584 | ||
585 | /* | |
586 | * Recycle the hrtimer in ts, so we can share the | |
587 | * hrtimer_forward with the highres code. | |
588 | */ | |
589 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
590 | /* Get the next period */ | |
591 | next = tick_init_jiffy_update(); | |
592 | ||
593 | for (;;) { | |
cc584b21 | 594 | hrtimer_set_expires(&ts->sched_timer, next); |
79bf2bb3 TG |
595 | if (!tick_program_event(next, 0)) |
596 | break; | |
597 | next = ktime_add(next, tick_period); | |
598 | } | |
599 | local_irq_enable(); | |
600 | ||
601 | printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n", | |
602 | smp_processor_id()); | |
603 | } | |
604 | ||
fb02fbc1 TG |
605 | /* |
606 | * When NOHZ is enabled and the tick is stopped, we need to kick the | |
607 | * tick timer from irq_enter() so that the jiffies update is kept | |
608 | * alive during long running softirqs. That's ugly as hell, but | |
609 | * correctness is key even if we need to fix the offending softirq in | |
610 | * the first place. | |
611 | * | |
612 | * Note, this is different to tick_nohz_restart. We just kick the | |
613 | * timer and do not touch the other magic bits which need to be done | |
614 | * when idle is left. | |
615 | */ | |
eed3b9cf | 616 | static void tick_nohz_kick_tick(int cpu, ktime_t now) |
fb02fbc1 | 617 | { |
ae99286b TG |
618 | #if 0 |
619 | /* Switch back to 2.6.27 behaviour */ | |
620 | ||
fb02fbc1 | 621 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
eed3b9cf | 622 | ktime_t delta; |
fb02fbc1 | 623 | |
c4bd822e TG |
624 | /* |
625 | * Do not touch the tick device, when the next expiry is either | |
626 | * already reached or less/equal than the tick period. | |
627 | */ | |
268a3dcf | 628 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
c4bd822e TG |
629 | if (delta.tv64 <= tick_period.tv64) |
630 | return; | |
631 | ||
632 | tick_nohz_restart(ts, now); | |
ae99286b | 633 | #endif |
fb02fbc1 TG |
634 | } |
635 | ||
eed3b9cf MS |
636 | static inline void tick_check_nohz(int cpu) |
637 | { | |
638 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
639 | ktime_t now; | |
640 | ||
641 | if (!ts->idle_active && !ts->tick_stopped) | |
642 | return; | |
643 | now = ktime_get(); | |
644 | if (ts->idle_active) | |
645 | tick_nohz_stop_idle(cpu, now); | |
646 | if (ts->tick_stopped) { | |
647 | tick_nohz_update_jiffies(now); | |
648 | tick_nohz_kick_tick(cpu, now); | |
649 | } | |
650 | } | |
651 | ||
79bf2bb3 TG |
652 | #else |
653 | ||
654 | static inline void tick_nohz_switch_to_nohz(void) { } | |
eed3b9cf | 655 | static inline void tick_check_nohz(int cpu) { } |
79bf2bb3 TG |
656 | |
657 | #endif /* NO_HZ */ | |
658 | ||
719254fa TG |
659 | /* |
660 | * Called from irq_enter to notify about the possible interruption of idle() | |
661 | */ | |
662 | void tick_check_idle(int cpu) | |
663 | { | |
fb02fbc1 | 664 | tick_check_oneshot_broadcast(cpu); |
eed3b9cf | 665 | tick_check_nohz(cpu); |
719254fa TG |
666 | } |
667 | ||
79bf2bb3 TG |
668 | /* |
669 | * High resolution timer specific code | |
670 | */ | |
671 | #ifdef CONFIG_HIGH_RES_TIMERS | |
672 | /* | |
4c9dc641 | 673 | * We rearm the timer until we get disabled by the idle code. |
79bf2bb3 TG |
674 | * Called with interrupts disabled and timer->base->cpu_base->lock held. |
675 | */ | |
676 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
677 | { | |
678 | struct tick_sched *ts = | |
679 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
680 | struct pt_regs *regs = get_irq_regs(); |
681 | ktime_t now = ktime_get(); | |
d3ed7824 TG |
682 | int cpu = smp_processor_id(); |
683 | ||
684 | #ifdef CONFIG_NO_HZ | |
685 | /* | |
686 | * Check if the do_timer duty was dropped. We don't care about | |
687 | * concurrency: This happens only when the cpu in charge went | |
688 | * into a long sleep. If two cpus happen to assign themself to | |
689 | * this duty, then the jiffies update is still serialized by | |
690 | * xtime_lock. | |
691 | */ | |
6441402b | 692 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
d3ed7824 TG |
693 | tick_do_timer_cpu = cpu; |
694 | #endif | |
79bf2bb3 TG |
695 | |
696 | /* Check, if the jiffies need an update */ | |
d3ed7824 TG |
697 | if (tick_do_timer_cpu == cpu) |
698 | tick_do_update_jiffies64(now); | |
79bf2bb3 TG |
699 | |
700 | /* | |
701 | * Do not call, when we are not in irq context and have | |
702 | * no valid regs pointer | |
703 | */ | |
704 | if (regs) { | |
705 | /* | |
706 | * When we are idle and the tick is stopped, we have to touch | |
707 | * the watchdog as we might not schedule for a really long | |
708 | * time. This happens on complete idle SMP systems while | |
709 | * waiting on the login prompt. We also increment the "start of | |
710 | * idle" jiffy stamp so the idle accounting adjustment we do | |
711 | * when we go busy again does not account too much ticks. | |
712 | */ | |
713 | if (ts->tick_stopped) { | |
714 | touch_softlockup_watchdog(); | |
715 | ts->idle_jiffies++; | |
716 | } | |
79bf2bb3 TG |
717 | update_process_times(user_mode(regs)); |
718 | profile_tick(CPU_PROFILING); | |
79bf2bb3 TG |
719 | } |
720 | ||
79bf2bb3 TG |
721 | hrtimer_forward(timer, now, tick_period); |
722 | ||
723 | return HRTIMER_RESTART; | |
724 | } | |
725 | ||
726 | /** | |
727 | * tick_setup_sched_timer - setup the tick emulation timer | |
728 | */ | |
729 | void tick_setup_sched_timer(void) | |
730 | { | |
731 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
732 | ktime_t now = ktime_get(); | |
3704540b | 733 | u64 offset; |
79bf2bb3 TG |
734 | |
735 | /* | |
736 | * Emulate tick processing via per-CPU hrtimers: | |
737 | */ | |
738 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
739 | ts->sched_timer.function = tick_sched_timer; | |
79bf2bb3 | 740 | |
3704540b | 741 | /* Get the next period (per cpu) */ |
cc584b21 | 742 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
3704540b | 743 | offset = ktime_to_ns(tick_period) >> 1; |
b2d9323d | 744 | do_div(offset, num_possible_cpus()); |
3704540b | 745 | offset *= smp_processor_id(); |
cc584b21 | 746 | hrtimer_add_expires_ns(&ts->sched_timer, offset); |
79bf2bb3 TG |
747 | |
748 | for (;;) { | |
749 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
5c333864 AB |
750 | hrtimer_start_expires(&ts->sched_timer, |
751 | HRTIMER_MODE_ABS_PINNED); | |
79bf2bb3 TG |
752 | /* Check, if the timer was already in the past */ |
753 | if (hrtimer_active(&ts->sched_timer)) | |
754 | break; | |
755 | now = ktime_get(); | |
756 | } | |
757 | ||
758 | #ifdef CONFIG_NO_HZ | |
759 | if (tick_nohz_enabled) | |
760 | ts->nohz_mode = NOHZ_MODE_HIGHRES; | |
761 | #endif | |
762 | } | |
3c4fbe5e | 763 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 764 | |
3c4fbe5e | 765 | #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
766 | void tick_cancel_sched_timer(int cpu) |
767 | { | |
768 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
769 | ||
3c4fbe5e | 770 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
771 | if (ts->sched_timer.base) |
772 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 773 | # endif |
a7901766 | 774 | |
79bf2bb3 TG |
775 | ts->nohz_mode = NOHZ_MODE_INACTIVE; |
776 | } | |
3c4fbe5e | 777 | #endif |
79bf2bb3 TG |
778 | |
779 | /** | |
780 | * Async notification about clocksource changes | |
781 | */ | |
782 | void tick_clock_notify(void) | |
783 | { | |
784 | int cpu; | |
785 | ||
786 | for_each_possible_cpu(cpu) | |
787 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
788 | } | |
789 | ||
790 | /* | |
791 | * Async notification about clock event changes | |
792 | */ | |
793 | void tick_oneshot_notify(void) | |
794 | { | |
795 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
796 | ||
797 | set_bit(0, &ts->check_clocks); | |
798 | } | |
799 | ||
800 | /** | |
801 | * Check, if a change happened, which makes oneshot possible. | |
802 | * | |
803 | * Called cyclic from the hrtimer softirq (driven by the timer | |
804 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
805 | * mode, because high resolution timers are disabled (either compile | |
806 | * or runtime). | |
807 | */ | |
808 | int tick_check_oneshot_change(int allow_nohz) | |
809 | { | |
810 | struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); | |
811 | ||
812 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
813 | return 0; | |
814 | ||
815 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
816 | return 0; | |
817 | ||
cf4fc6cb | 818 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
819 | return 0; |
820 | ||
821 | if (!allow_nohz) | |
822 | return 1; | |
823 | ||
824 | tick_nohz_switch_to_nohz(); | |
825 | return 0; | |
826 | } |