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1 | /* | |
2 | * linux/kernel/time/tick-common.c | |
3 | * | |
4 | * This file contains the base functions to manage periodic tick | |
5 | * related events. | |
6 | * | |
7 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> | |
8 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar | |
9 | * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner | |
10 | * | |
11 | * This code is licenced under the GPL version 2. For details see | |
12 | * kernel-base/COPYING. | |
13 | */ | |
14 | #include <linux/cpu.h> | |
15 | #include <linux/err.h> | |
16 | #include <linux/hrtimer.h> | |
17 | #include <linux/interrupt.h> | |
18 | #include <linux/percpu.h> | |
19 | #include <linux/profile.h> | |
20 | #include <linux/sched.h> | |
21 | #include <linux/module.h> | |
22 | #include <trace/events/power.h> | |
23 | ||
24 | #include <asm/irq_regs.h> | |
25 | ||
26 | #include "tick-internal.h" | |
27 | ||
28 | /* | |
29 | * Tick devices | |
30 | */ | |
31 | DEFINE_PER_CPU(struct tick_device, tick_cpu_device); | |
32 | /* | |
33 | * Tick next event: keeps track of the tick time | |
34 | */ | |
35 | ktime_t tick_next_period; | |
36 | ktime_t tick_period; | |
37 | ||
38 | /* | |
39 | * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR | |
40 | * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This | |
41 | * variable has two functions: | |
42 | * | |
43 | * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the | |
44 | * timekeeping lock all at once. Only the CPU which is assigned to do the | |
45 | * update is handling it. | |
46 | * | |
47 | * 2) Hand off the duty in the NOHZ idle case by setting the value to | |
48 | * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks | |
49 | * at it will take over and keep the time keeping alive. The handover | |
50 | * procedure also covers cpu hotplug. | |
51 | */ | |
52 | int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; | |
53 | ||
54 | /* | |
55 | * Debugging: see timer_list.c | |
56 | */ | |
57 | struct tick_device *tick_get_device(int cpu) | |
58 | { | |
59 | return &per_cpu(tick_cpu_device, cpu); | |
60 | } | |
61 | ||
62 | /** | |
63 | * tick_is_oneshot_available - check for a oneshot capable event device | |
64 | */ | |
65 | int tick_is_oneshot_available(void) | |
66 | { | |
67 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); | |
68 | ||
69 | if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT)) | |
70 | return 0; | |
71 | if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) | |
72 | return 1; | |
73 | return tick_broadcast_oneshot_available(); | |
74 | } | |
75 | ||
76 | /* | |
77 | * Periodic tick | |
78 | */ | |
79 | static void tick_periodic(int cpu) | |
80 | { | |
81 | if (tick_do_timer_cpu == cpu) { | |
82 | write_seqlock(&jiffies_lock); | |
83 | ||
84 | /* Keep track of the next tick event */ | |
85 | tick_next_period = ktime_add(tick_next_period, tick_period); | |
86 | ||
87 | do_timer(1); | |
88 | write_sequnlock(&jiffies_lock); | |
89 | update_wall_time(); | |
90 | } | |
91 | ||
92 | update_process_times(user_mode(get_irq_regs())); | |
93 | profile_tick(CPU_PROFILING); | |
94 | } | |
95 | ||
96 | /* | |
97 | * Event handler for periodic ticks | |
98 | */ | |
99 | void tick_handle_periodic(struct clock_event_device *dev) | |
100 | { | |
101 | int cpu = smp_processor_id(); | |
102 | ktime_t next = dev->next_event; | |
103 | ||
104 | tick_periodic(cpu); | |
105 | ||
106 | #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON) | |
107 | /* | |
108 | * The cpu might have transitioned to HIGHRES or NOHZ mode via | |
109 | * update_process_times() -> run_local_timers() -> | |
110 | * hrtimer_run_queues(). | |
111 | */ | |
112 | if (dev->event_handler != tick_handle_periodic) | |
113 | return; | |
114 | #endif | |
115 | ||
116 | if (!clockevent_state_oneshot(dev)) | |
117 | return; | |
118 | for (;;) { | |
119 | /* | |
120 | * Setup the next period for devices, which do not have | |
121 | * periodic mode: | |
122 | */ | |
123 | next = ktime_add(next, tick_period); | |
124 | ||
125 | if (!clockevents_program_event(dev, next, false)) | |
126 | return; | |
127 | /* | |
128 | * Have to be careful here. If we're in oneshot mode, | |
129 | * before we call tick_periodic() in a loop, we need | |
130 | * to be sure we're using a real hardware clocksource. | |
131 | * Otherwise we could get trapped in an infinite | |
132 | * loop, as the tick_periodic() increments jiffies, | |
133 | * which then will increment time, possibly causing | |
134 | * the loop to trigger again and again. | |
135 | */ | |
136 | if (timekeeping_valid_for_hres()) | |
137 | tick_periodic(cpu); | |
138 | } | |
139 | } | |
140 | ||
141 | /* | |
142 | * Setup the device for a periodic tick | |
143 | */ | |
144 | void tick_setup_periodic(struct clock_event_device *dev, int broadcast) | |
145 | { | |
146 | tick_set_periodic_handler(dev, broadcast); | |
147 | ||
148 | /* Broadcast setup ? */ | |
149 | if (!tick_device_is_functional(dev)) | |
150 | return; | |
151 | ||
152 | if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && | |
153 | !tick_broadcast_oneshot_active()) { | |
154 | clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC); | |
155 | } else { | |
156 | unsigned long seq; | |
157 | ktime_t next; | |
158 | ||
159 | do { | |
160 | seq = read_seqbegin(&jiffies_lock); | |
161 | next = tick_next_period; | |
162 | } while (read_seqretry(&jiffies_lock, seq)); | |
163 | ||
164 | clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); | |
165 | ||
166 | for (;;) { | |
167 | if (!clockevents_program_event(dev, next, false)) | |
168 | return; | |
169 | next = ktime_add(next, tick_period); | |
170 | } | |
171 | } | |
172 | } | |
173 | ||
174 | /* | |
175 | * Setup the tick device | |
176 | */ | |
177 | static void tick_setup_device(struct tick_device *td, | |
178 | struct clock_event_device *newdev, int cpu, | |
179 | const struct cpumask *cpumask) | |
180 | { | |
181 | void (*handler)(struct clock_event_device *) = NULL; | |
182 | ktime_t next_event = 0; | |
183 | ||
184 | /* | |
185 | * First device setup ? | |
186 | */ | |
187 | if (!td->evtdev) { | |
188 | /* | |
189 | * If no cpu took the do_timer update, assign it to | |
190 | * this cpu: | |
191 | */ | |
192 | if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { | |
193 | if (!tick_nohz_full_cpu(cpu)) | |
194 | tick_do_timer_cpu = cpu; | |
195 | else | |
196 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
197 | tick_next_period = ktime_get(); | |
198 | tick_period = NSEC_PER_SEC / HZ; | |
199 | } | |
200 | ||
201 | /* | |
202 | * Startup in periodic mode first. | |
203 | */ | |
204 | td->mode = TICKDEV_MODE_PERIODIC; | |
205 | } else { | |
206 | handler = td->evtdev->event_handler; | |
207 | next_event = td->evtdev->next_event; | |
208 | td->evtdev->event_handler = clockevents_handle_noop; | |
209 | } | |
210 | ||
211 | td->evtdev = newdev; | |
212 | ||
213 | /* | |
214 | * When the device is not per cpu, pin the interrupt to the | |
215 | * current cpu: | |
216 | */ | |
217 | if (!cpumask_equal(newdev->cpumask, cpumask)) | |
218 | irq_set_affinity(newdev->irq, cpumask); | |
219 | ||
220 | /* | |
221 | * When global broadcasting is active, check if the current | |
222 | * device is registered as a placeholder for broadcast mode. | |
223 | * This allows us to handle this x86 misfeature in a generic | |
224 | * way. This function also returns !=0 when we keep the | |
225 | * current active broadcast state for this CPU. | |
226 | */ | |
227 | if (tick_device_uses_broadcast(newdev, cpu)) | |
228 | return; | |
229 | ||
230 | if (td->mode == TICKDEV_MODE_PERIODIC) | |
231 | tick_setup_periodic(newdev, 0); | |
232 | else | |
233 | tick_setup_oneshot(newdev, handler, next_event); | |
234 | } | |
235 | ||
236 | void tick_install_replacement(struct clock_event_device *newdev) | |
237 | { | |
238 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); | |
239 | int cpu = smp_processor_id(); | |
240 | ||
241 | clockevents_exchange_device(td->evtdev, newdev); | |
242 | tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); | |
243 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) | |
244 | tick_oneshot_notify(); | |
245 | } | |
246 | ||
247 | static bool tick_check_percpu(struct clock_event_device *curdev, | |
248 | struct clock_event_device *newdev, int cpu) | |
249 | { | |
250 | if (!cpumask_test_cpu(cpu, newdev->cpumask)) | |
251 | return false; | |
252 | if (cpumask_equal(newdev->cpumask, cpumask_of(cpu))) | |
253 | return true; | |
254 | /* Check if irq affinity can be set */ | |
255 | if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq)) | |
256 | return false; | |
257 | /* Prefer an existing cpu local device */ | |
258 | if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) | |
259 | return false; | |
260 | return true; | |
261 | } | |
262 | ||
263 | static bool tick_check_preferred(struct clock_event_device *curdev, | |
264 | struct clock_event_device *newdev) | |
265 | { | |
266 | /* Prefer oneshot capable device */ | |
267 | if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) { | |
268 | if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT)) | |
269 | return false; | |
270 | if (tick_oneshot_mode_active()) | |
271 | return false; | |
272 | } | |
273 | ||
274 | /* | |
275 | * Use the higher rated one, but prefer a CPU local device with a lower | |
276 | * rating than a non-CPU local device | |
277 | */ | |
278 | return !curdev || | |
279 | newdev->rating > curdev->rating || | |
280 | !cpumask_equal(curdev->cpumask, newdev->cpumask); | |
281 | } | |
282 | ||
283 | /* | |
284 | * Check whether the new device is a better fit than curdev. curdev | |
285 | * can be NULL ! | |
286 | */ | |
287 | bool tick_check_replacement(struct clock_event_device *curdev, | |
288 | struct clock_event_device *newdev) | |
289 | { | |
290 | if (!tick_check_percpu(curdev, newdev, smp_processor_id())) | |
291 | return false; | |
292 | ||
293 | return tick_check_preferred(curdev, newdev); | |
294 | } | |
295 | ||
296 | /* | |
297 | * Check, if the new registered device should be used. Called with | |
298 | * clockevents_lock held and interrupts disabled. | |
299 | */ | |
300 | void tick_check_new_device(struct clock_event_device *newdev) | |
301 | { | |
302 | struct clock_event_device *curdev; | |
303 | struct tick_device *td; | |
304 | int cpu; | |
305 | ||
306 | cpu = smp_processor_id(); | |
307 | td = &per_cpu(tick_cpu_device, cpu); | |
308 | curdev = td->evtdev; | |
309 | ||
310 | /* cpu local device ? */ | |
311 | if (!tick_check_percpu(curdev, newdev, cpu)) | |
312 | goto out_bc; | |
313 | ||
314 | /* Preference decision */ | |
315 | if (!tick_check_preferred(curdev, newdev)) | |
316 | goto out_bc; | |
317 | ||
318 | if (!try_module_get(newdev->owner)) | |
319 | return; | |
320 | ||
321 | /* | |
322 | * Replace the eventually existing device by the new | |
323 | * device. If the current device is the broadcast device, do | |
324 | * not give it back to the clockevents layer ! | |
325 | */ | |
326 | if (tick_is_broadcast_device(curdev)) { | |
327 | clockevents_shutdown(curdev); | |
328 | curdev = NULL; | |
329 | } | |
330 | clockevents_exchange_device(curdev, newdev); | |
331 | tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); | |
332 | if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) | |
333 | tick_oneshot_notify(); | |
334 | return; | |
335 | ||
336 | out_bc: | |
337 | /* | |
338 | * Can the new device be used as a broadcast device ? | |
339 | */ | |
340 | tick_install_broadcast_device(newdev); | |
341 | } | |
342 | ||
343 | /** | |
344 | * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode | |
345 | * @state: The target state (enter/exit) | |
346 | * | |
347 | * The system enters/leaves a state, where affected devices might stop | |
348 | * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups. | |
349 | * | |
350 | * Called with interrupts disabled, so clockevents_lock is not | |
351 | * required here because the local clock event device cannot go away | |
352 | * under us. | |
353 | */ | |
354 | int tick_broadcast_oneshot_control(enum tick_broadcast_state state) | |
355 | { | |
356 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); | |
357 | ||
358 | if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP)) | |
359 | return 0; | |
360 | ||
361 | return __tick_broadcast_oneshot_control(state); | |
362 | } | |
363 | EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control); | |
364 | ||
365 | #ifdef CONFIG_HOTPLUG_CPU | |
366 | /* | |
367 | * Transfer the do_timer job away from a dying cpu. | |
368 | * | |
369 | * Called with interrupts disabled. Not locking required. If | |
370 | * tick_do_timer_cpu is owned by this cpu, nothing can change it. | |
371 | */ | |
372 | void tick_handover_do_timer(void) | |
373 | { | |
374 | if (tick_do_timer_cpu == smp_processor_id()) { | |
375 | int cpu = cpumask_first(cpu_online_mask); | |
376 | ||
377 | tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : | |
378 | TICK_DO_TIMER_NONE; | |
379 | } | |
380 | } | |
381 | ||
382 | /* | |
383 | * Shutdown an event device on a given cpu: | |
384 | * | |
385 | * This is called on a life CPU, when a CPU is dead. So we cannot | |
386 | * access the hardware device itself. | |
387 | * We just set the mode and remove it from the lists. | |
388 | */ | |
389 | void tick_shutdown(unsigned int cpu) | |
390 | { | |
391 | struct tick_device *td = &per_cpu(tick_cpu_device, cpu); | |
392 | struct clock_event_device *dev = td->evtdev; | |
393 | ||
394 | td->mode = TICKDEV_MODE_PERIODIC; | |
395 | if (dev) { | |
396 | /* | |
397 | * Prevent that the clock events layer tries to call | |
398 | * the set mode function! | |
399 | */ | |
400 | clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED); | |
401 | clockevents_exchange_device(dev, NULL); | |
402 | dev->event_handler = clockevents_handle_noop; | |
403 | td->evtdev = NULL; | |
404 | } | |
405 | } | |
406 | #endif | |
407 | ||
408 | /** | |
409 | * tick_suspend_local - Suspend the local tick device | |
410 | * | |
411 | * Called from the local cpu for freeze with interrupts disabled. | |
412 | * | |
413 | * No locks required. Nothing can change the per cpu device. | |
414 | */ | |
415 | void tick_suspend_local(void) | |
416 | { | |
417 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); | |
418 | ||
419 | clockevents_shutdown(td->evtdev); | |
420 | } | |
421 | ||
422 | /** | |
423 | * tick_resume_local - Resume the local tick device | |
424 | * | |
425 | * Called from the local CPU for unfreeze or XEN resume magic. | |
426 | * | |
427 | * No locks required. Nothing can change the per cpu device. | |
428 | */ | |
429 | void tick_resume_local(void) | |
430 | { | |
431 | struct tick_device *td = this_cpu_ptr(&tick_cpu_device); | |
432 | bool broadcast = tick_resume_check_broadcast(); | |
433 | ||
434 | clockevents_tick_resume(td->evtdev); | |
435 | if (!broadcast) { | |
436 | if (td->mode == TICKDEV_MODE_PERIODIC) | |
437 | tick_setup_periodic(td->evtdev, 0); | |
438 | else | |
439 | tick_resume_oneshot(); | |
440 | } | |
441 | } | |
442 | ||
443 | /** | |
444 | * tick_suspend - Suspend the tick and the broadcast device | |
445 | * | |
446 | * Called from syscore_suspend() via timekeeping_suspend with only one | |
447 | * CPU online and interrupts disabled or from tick_unfreeze() under | |
448 | * tick_freeze_lock. | |
449 | * | |
450 | * No locks required. Nothing can change the per cpu device. | |
451 | */ | |
452 | void tick_suspend(void) | |
453 | { | |
454 | tick_suspend_local(); | |
455 | tick_suspend_broadcast(); | |
456 | } | |
457 | ||
458 | /** | |
459 | * tick_resume - Resume the tick and the broadcast device | |
460 | * | |
461 | * Called from syscore_resume() via timekeeping_resume with only one | |
462 | * CPU online and interrupts disabled. | |
463 | * | |
464 | * No locks required. Nothing can change the per cpu device. | |
465 | */ | |
466 | void tick_resume(void) | |
467 | { | |
468 | tick_resume_broadcast(); | |
469 | tick_resume_local(); | |
470 | } | |
471 | ||
472 | #ifdef CONFIG_SUSPEND | |
473 | static DEFINE_RAW_SPINLOCK(tick_freeze_lock); | |
474 | static unsigned int tick_freeze_depth; | |
475 | ||
476 | /** | |
477 | * tick_freeze - Suspend the local tick and (possibly) timekeeping. | |
478 | * | |
479 | * Check if this is the last online CPU executing the function and if so, | |
480 | * suspend timekeeping. Otherwise suspend the local tick. | |
481 | * | |
482 | * Call with interrupts disabled. Must be balanced with %tick_unfreeze(). | |
483 | * Interrupts must not be enabled before the subsequent %tick_unfreeze(). | |
484 | */ | |
485 | void tick_freeze(void) | |
486 | { | |
487 | raw_spin_lock(&tick_freeze_lock); | |
488 | ||
489 | tick_freeze_depth++; | |
490 | if (tick_freeze_depth == num_online_cpus()) { | |
491 | trace_suspend_resume(TPS("timekeeping_freeze"), | |
492 | smp_processor_id(), true); | |
493 | timekeeping_suspend(); | |
494 | } else { | |
495 | tick_suspend_local(); | |
496 | } | |
497 | ||
498 | raw_spin_unlock(&tick_freeze_lock); | |
499 | } | |
500 | ||
501 | /** | |
502 | * tick_unfreeze - Resume the local tick and (possibly) timekeeping. | |
503 | * | |
504 | * Check if this is the first CPU executing the function and if so, resume | |
505 | * timekeeping. Otherwise resume the local tick. | |
506 | * | |
507 | * Call with interrupts disabled. Must be balanced with %tick_freeze(). | |
508 | * Interrupts must not be enabled after the preceding %tick_freeze(). | |
509 | */ | |
510 | void tick_unfreeze(void) | |
511 | { | |
512 | raw_spin_lock(&tick_freeze_lock); | |
513 | ||
514 | if (tick_freeze_depth == num_online_cpus()) { | |
515 | timekeeping_resume(); | |
516 | trace_suspend_resume(TPS("timekeeping_freeze"), | |
517 | smp_processor_id(), false); | |
518 | } else { | |
519 | tick_resume_local(); | |
520 | } | |
521 | ||
522 | tick_freeze_depth--; | |
523 | ||
524 | raw_spin_unlock(&tick_freeze_lock); | |
525 | } | |
526 | #endif /* CONFIG_SUSPEND */ | |
527 | ||
528 | /** | |
529 | * tick_init - initialize the tick control | |
530 | */ | |
531 | void __init tick_init(void) | |
532 | { | |
533 | tick_broadcast_init(); | |
534 | tick_nohz_init(); | |
535 | } |