Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * This file contains the base functions to manage periodic tick
4 : * related events.
5 : *
6 : * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
7 : * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
8 : * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
9 : */
10 : #include <linux/cpu.h>
11 : #include <linux/err.h>
12 : #include <linux/hrtimer.h>
13 : #include <linux/interrupt.h>
14 : #include <linux/nmi.h>
15 : #include <linux/percpu.h>
16 : #include <linux/profile.h>
17 : #include <linux/sched.h>
18 : #include <linux/module.h>
19 : #include <trace/events/power.h>
20 :
21 : #include <asm/irq_regs.h>
22 :
23 : #include "tick-internal.h"
24 :
25 : /*
26 : * Tick devices
27 : */
28 : DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
29 : /*
30 : * Tick next event: keeps track of the tick time. It's updated by the
31 : * CPU which handles the tick and protected by jiffies_lock. There is
32 : * no requirement to write hold the jiffies seqcount for it.
33 : */
34 : ktime_t tick_next_period;
35 :
36 : /*
37 : * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
38 : * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
39 : * variable has two functions:
40 : *
41 : * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
42 : * timekeeping lock all at once. Only the CPU which is assigned to do the
43 : * update is handling it.
44 : *
45 : * 2) Hand off the duty in the NOHZ idle case by setting the value to
46 : * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
47 : * at it will take over and keep the time keeping alive. The handover
48 : * procedure also covers cpu hotplug.
49 : */
50 : int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
51 : #ifdef CONFIG_NO_HZ_FULL
52 : /*
53 : * tick_do_timer_boot_cpu indicates the boot CPU temporarily owns
54 : * tick_do_timer_cpu and it should be taken over by an eligible secondary
55 : * when one comes online.
56 : */
57 : static int tick_do_timer_boot_cpu __read_mostly = -1;
58 : #endif
59 :
60 : /*
61 : * Debugging: see timer_list.c
62 : */
63 0 : struct tick_device *tick_get_device(int cpu)
64 : {
65 0 : return &per_cpu(tick_cpu_device, cpu);
66 : }
67 :
68 : /**
69 : * tick_is_oneshot_available - check for a oneshot capable event device
70 : */
71 4 : int tick_is_oneshot_available(void)
72 : {
73 4 : struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
74 :
75 4 : if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
76 : return 0;
77 4 : if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
78 : return 1;
79 0 : return tick_broadcast_oneshot_available();
80 : }
81 :
82 : /*
83 : * Periodic tick
84 : */
85 76 : static void tick_periodic(int cpu)
86 : {
87 76 : if (tick_do_timer_cpu == cpu) {
88 24 : raw_spin_lock(&jiffies_lock);
89 48 : write_seqcount_begin(&jiffies_seq);
90 :
91 : /* Keep track of the next tick event */
92 24 : tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
93 :
94 24 : do_timer(1);
95 24 : write_seqcount_end(&jiffies_seq);
96 24 : raw_spin_unlock(&jiffies_lock);
97 24 : update_wall_time();
98 : }
99 :
100 76 : update_process_times(user_mode(get_irq_regs()));
101 76 : profile_tick(CPU_PROFILING);
102 76 : }
103 :
104 : /*
105 : * Event handler for periodic ticks
106 : */
107 76 : void tick_handle_periodic(struct clock_event_device *dev)
108 : {
109 76 : int cpu = smp_processor_id();
110 76 : ktime_t next = dev->next_event;
111 :
112 76 : tick_periodic(cpu);
113 :
114 : #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
115 : /*
116 : * The cpu might have transitioned to HIGHRES or NOHZ mode via
117 : * update_process_times() -> run_local_timers() ->
118 : * hrtimer_run_queues().
119 : */
120 76 : if (dev->event_handler != tick_handle_periodic)
121 : return;
122 : #endif
123 :
124 72 : if (!clockevent_state_oneshot(dev))
125 : return;
126 72 : for (;;) {
127 : /*
128 : * Setup the next period for devices, which do not have
129 : * periodic mode:
130 : */
131 72 : next = ktime_add_ns(next, TICK_NSEC);
132 :
133 72 : if (!clockevents_program_event(dev, next, false))
134 : return;
135 : /*
136 : * Have to be careful here. If we're in oneshot mode,
137 : * before we call tick_periodic() in a loop, we need
138 : * to be sure we're using a real hardware clocksource.
139 : * Otherwise we could get trapped in an infinite
140 : * loop, as the tick_periodic() increments jiffies,
141 : * which then will increment time, possibly causing
142 : * the loop to trigger again and again.
143 : */
144 0 : if (timekeeping_valid_for_hres())
145 0 : tick_periodic(cpu);
146 : }
147 : }
148 :
149 : /*
150 : * Setup the device for a periodic tick
151 : */
152 4 : void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
153 : {
154 4 : tick_set_periodic_handler(dev, broadcast);
155 :
156 : /* Broadcast setup ? */
157 4 : if (!tick_device_is_functional(dev))
158 : return;
159 :
160 4 : if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
161 0 : !tick_broadcast_oneshot_active()) {
162 0 : clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
163 : } else {
164 4 : unsigned int seq;
165 4 : ktime_t next;
166 :
167 4 : do {
168 4 : seq = read_seqcount_begin(&jiffies_seq);
169 4 : next = tick_next_period;
170 4 : } while (read_seqcount_retry(&jiffies_seq, seq));
171 :
172 4 : clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
173 :
174 12 : for (;;) {
175 8 : if (!clockevents_program_event(dev, next, false))
176 : return;
177 4 : next = ktime_add_ns(next, TICK_NSEC);
178 : }
179 : }
180 : }
181 :
182 : #ifdef CONFIG_NO_HZ_FULL
183 : static void giveup_do_timer(void *info)
184 : {
185 : int cpu = *(unsigned int *)info;
186 :
187 : WARN_ON(tick_do_timer_cpu != smp_processor_id());
188 :
189 : tick_do_timer_cpu = cpu;
190 : }
191 :
192 : static void tick_take_do_timer_from_boot(void)
193 : {
194 : int cpu = smp_processor_id();
195 : int from = tick_do_timer_boot_cpu;
196 :
197 : if (from >= 0 && from != cpu)
198 : smp_call_function_single(from, giveup_do_timer, &cpu, 1);
199 : }
200 : #endif
201 :
202 : /*
203 : * Setup the tick device
204 : */
205 4 : static void tick_setup_device(struct tick_device *td,
206 : struct clock_event_device *newdev, int cpu,
207 : const struct cpumask *cpumask)
208 : {
209 4 : void (*handler)(struct clock_event_device *) = NULL;
210 4 : ktime_t next_event = 0;
211 :
212 : /*
213 : * First device setup ?
214 : */
215 4 : if (!td->evtdev) {
216 : /*
217 : * If no cpu took the do_timer update, assign it to
218 : * this cpu:
219 : */
220 4 : if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
221 1 : tick_do_timer_cpu = cpu;
222 :
223 1 : tick_next_period = ktime_get();
224 : #ifdef CONFIG_NO_HZ_FULL
225 : /*
226 : * The boot CPU may be nohz_full, in which case set
227 : * tick_do_timer_boot_cpu so the first housekeeping
228 : * secondary that comes up will take do_timer from
229 : * us.
230 : */
231 : if (tick_nohz_full_cpu(cpu))
232 : tick_do_timer_boot_cpu = cpu;
233 :
234 : } else if (tick_do_timer_boot_cpu != -1 &&
235 : !tick_nohz_full_cpu(cpu)) {
236 : tick_take_do_timer_from_boot();
237 : tick_do_timer_boot_cpu = -1;
238 : WARN_ON(tick_do_timer_cpu != cpu);
239 : #endif
240 : }
241 :
242 : /*
243 : * Startup in periodic mode first.
244 : */
245 4 : td->mode = TICKDEV_MODE_PERIODIC;
246 : } else {
247 0 : handler = td->evtdev->event_handler;
248 0 : next_event = td->evtdev->next_event;
249 0 : td->evtdev->event_handler = clockevents_handle_noop;
250 : }
251 :
252 4 : td->evtdev = newdev;
253 :
254 : /*
255 : * When the device is not per cpu, pin the interrupt to the
256 : * current cpu:
257 : */
258 4 : if (!cpumask_equal(newdev->cpumask, cpumask))
259 0 : irq_set_affinity(newdev->irq, cpumask);
260 :
261 : /*
262 : * When global broadcasting is active, check if the current
263 : * device is registered as a placeholder for broadcast mode.
264 : * This allows us to handle this x86 misfeature in a generic
265 : * way. This function also returns !=0 when we keep the
266 : * current active broadcast state for this CPU.
267 : */
268 4 : if (tick_device_uses_broadcast(newdev, cpu))
269 : return;
270 :
271 4 : if (td->mode == TICKDEV_MODE_PERIODIC)
272 4 : tick_setup_periodic(newdev, 0);
273 : else
274 0 : tick_setup_oneshot(newdev, handler, next_event);
275 : }
276 :
277 0 : void tick_install_replacement(struct clock_event_device *newdev)
278 : {
279 0 : struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
280 0 : int cpu = smp_processor_id();
281 :
282 0 : clockevents_exchange_device(td->evtdev, newdev);
283 0 : tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
284 0 : if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
285 0 : tick_oneshot_notify();
286 0 : }
287 :
288 4 : static bool tick_check_percpu(struct clock_event_device *curdev,
289 : struct clock_event_device *newdev, int cpu)
290 : {
291 4 : if (!cpumask_test_cpu(cpu, newdev->cpumask))
292 : return false;
293 4 : if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
294 : return true;
295 : /* Check if irq affinity can be set */
296 0 : if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
297 : return false;
298 : /* Prefer an existing cpu local device */
299 0 : if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
300 0 : return false;
301 : return true;
302 : }
303 :
304 4 : static bool tick_check_preferred(struct clock_event_device *curdev,
305 : struct clock_event_device *newdev)
306 : {
307 : /* Prefer oneshot capable device */
308 4 : if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
309 0 : if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
310 : return false;
311 0 : if (tick_oneshot_mode_active())
312 : return false;
313 : }
314 :
315 : /*
316 : * Use the higher rated one, but prefer a CPU local device with a lower
317 : * rating than a non-CPU local device
318 : */
319 4 : return !curdev ||
320 4 : newdev->rating > curdev->rating ||
321 0 : !cpumask_equal(curdev->cpumask, newdev->cpumask);
322 : }
323 :
324 : /*
325 : * Check whether the new device is a better fit than curdev. curdev
326 : * can be NULL !
327 : */
328 0 : bool tick_check_replacement(struct clock_event_device *curdev,
329 : struct clock_event_device *newdev)
330 : {
331 0 : if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
332 : return false;
333 :
334 0 : return tick_check_preferred(curdev, newdev);
335 : }
336 :
337 : /*
338 : * Check, if the new registered device should be used. Called with
339 : * clockevents_lock held and interrupts disabled.
340 : */
341 4 : void tick_check_new_device(struct clock_event_device *newdev)
342 : {
343 4 : struct clock_event_device *curdev;
344 4 : struct tick_device *td;
345 4 : int cpu;
346 :
347 4 : cpu = smp_processor_id();
348 4 : td = &per_cpu(tick_cpu_device, cpu);
349 4 : curdev = td->evtdev;
350 :
351 : /* cpu local device ? */
352 4 : if (!tick_check_percpu(curdev, newdev, cpu))
353 0 : goto out_bc;
354 :
355 : /* Preference decision */
356 4 : if (!tick_check_preferred(curdev, newdev))
357 0 : goto out_bc;
358 :
359 4 : if (!try_module_get(newdev->owner))
360 : return;
361 :
362 : /*
363 : * Replace the eventually existing device by the new
364 : * device. If the current device is the broadcast device, do
365 : * not give it back to the clockevents layer !
366 : */
367 4 : if (tick_is_broadcast_device(curdev)) {
368 0 : clockevents_shutdown(curdev);
369 0 : curdev = NULL;
370 : }
371 4 : clockevents_exchange_device(curdev, newdev);
372 4 : tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
373 4 : if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
374 4 : tick_oneshot_notify();
375 : return;
376 :
377 0 : out_bc:
378 : /*
379 : * Can the new device be used as a broadcast device ?
380 : */
381 0 : tick_install_broadcast_device(newdev);
382 : }
383 :
384 : /**
385 : * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
386 : * @state: The target state (enter/exit)
387 : *
388 : * The system enters/leaves a state, where affected devices might stop
389 : * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
390 : *
391 : * Called with interrupts disabled, so clockevents_lock is not
392 : * required here because the local clock event device cannot go away
393 : * under us.
394 : */
395 0 : int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
396 : {
397 0 : struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
398 :
399 0 : if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
400 : return 0;
401 :
402 0 : return __tick_broadcast_oneshot_control(state);
403 : }
404 : EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
405 :
406 : #ifdef CONFIG_HOTPLUG_CPU
407 : /*
408 : * Transfer the do_timer job away from a dying cpu.
409 : *
410 : * Called with interrupts disabled. No locking required. If
411 : * tick_do_timer_cpu is owned by this cpu, nothing can change it.
412 : */
413 0 : void tick_handover_do_timer(void)
414 : {
415 0 : if (tick_do_timer_cpu == smp_processor_id())
416 0 : tick_do_timer_cpu = cpumask_first(cpu_online_mask);
417 0 : }
418 :
419 : /*
420 : * Shutdown an event device on a given cpu:
421 : *
422 : * This is called on a life CPU, when a CPU is dead. So we cannot
423 : * access the hardware device itself.
424 : * We just set the mode and remove it from the lists.
425 : */
426 0 : void tick_shutdown(unsigned int cpu)
427 : {
428 0 : struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
429 0 : struct clock_event_device *dev = td->evtdev;
430 :
431 0 : td->mode = TICKDEV_MODE_PERIODIC;
432 0 : if (dev) {
433 : /*
434 : * Prevent that the clock events layer tries to call
435 : * the set mode function!
436 : */
437 0 : clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
438 0 : clockevents_exchange_device(dev, NULL);
439 0 : dev->event_handler = clockevents_handle_noop;
440 0 : td->evtdev = NULL;
441 : }
442 0 : }
443 : #endif
444 :
445 : /**
446 : * tick_suspend_local - Suspend the local tick device
447 : *
448 : * Called from the local cpu for freeze with interrupts disabled.
449 : *
450 : * No locks required. Nothing can change the per cpu device.
451 : */
452 0 : void tick_suspend_local(void)
453 : {
454 0 : struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
455 :
456 0 : clockevents_shutdown(td->evtdev);
457 0 : }
458 :
459 : /**
460 : * tick_resume_local - Resume the local tick device
461 : *
462 : * Called from the local CPU for unfreeze or XEN resume magic.
463 : *
464 : * No locks required. Nothing can change the per cpu device.
465 : */
466 0 : void tick_resume_local(void)
467 : {
468 0 : struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
469 0 : bool broadcast = tick_resume_check_broadcast();
470 :
471 0 : clockevents_tick_resume(td->evtdev);
472 0 : if (!broadcast) {
473 0 : if (td->mode == TICKDEV_MODE_PERIODIC)
474 0 : tick_setup_periodic(td->evtdev, 0);
475 : else
476 0 : tick_resume_oneshot();
477 : }
478 0 : }
479 :
480 : /**
481 : * tick_suspend - Suspend the tick and the broadcast device
482 : *
483 : * Called from syscore_suspend() via timekeeping_suspend with only one
484 : * CPU online and interrupts disabled or from tick_unfreeze() under
485 : * tick_freeze_lock.
486 : *
487 : * No locks required. Nothing can change the per cpu device.
488 : */
489 0 : void tick_suspend(void)
490 : {
491 0 : tick_suspend_local();
492 0 : tick_suspend_broadcast();
493 0 : }
494 :
495 : /**
496 : * tick_resume - Resume the tick and the broadcast device
497 : *
498 : * Called from syscore_resume() via timekeeping_resume with only one
499 : * CPU online and interrupts disabled.
500 : *
501 : * No locks required. Nothing can change the per cpu device.
502 : */
503 0 : void tick_resume(void)
504 : {
505 0 : tick_resume_broadcast();
506 0 : tick_resume_local();
507 0 : }
508 :
509 : #ifdef CONFIG_SUSPEND
510 : static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
511 : static unsigned int tick_freeze_depth;
512 :
513 : /**
514 : * tick_freeze - Suspend the local tick and (possibly) timekeeping.
515 : *
516 : * Check if this is the last online CPU executing the function and if so,
517 : * suspend timekeeping. Otherwise suspend the local tick.
518 : *
519 : * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
520 : * Interrupts must not be enabled before the subsequent %tick_unfreeze().
521 : */
522 : void tick_freeze(void)
523 : {
524 : raw_spin_lock(&tick_freeze_lock);
525 :
526 : tick_freeze_depth++;
527 : if (tick_freeze_depth == num_online_cpus()) {
528 : trace_suspend_resume(TPS("timekeeping_freeze"),
529 : smp_processor_id(), true);
530 : system_state = SYSTEM_SUSPEND;
531 : sched_clock_suspend();
532 : timekeeping_suspend();
533 : } else {
534 : tick_suspend_local();
535 : }
536 :
537 : raw_spin_unlock(&tick_freeze_lock);
538 : }
539 :
540 : /**
541 : * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
542 : *
543 : * Check if this is the first CPU executing the function and if so, resume
544 : * timekeeping. Otherwise resume the local tick.
545 : *
546 : * Call with interrupts disabled. Must be balanced with %tick_freeze().
547 : * Interrupts must not be enabled after the preceding %tick_freeze().
548 : */
549 : void tick_unfreeze(void)
550 : {
551 : raw_spin_lock(&tick_freeze_lock);
552 :
553 : if (tick_freeze_depth == num_online_cpus()) {
554 : timekeeping_resume();
555 : sched_clock_resume();
556 : system_state = SYSTEM_RUNNING;
557 : trace_suspend_resume(TPS("timekeeping_freeze"),
558 : smp_processor_id(), false);
559 : } else {
560 : touch_softlockup_watchdog();
561 : tick_resume_local();
562 : }
563 :
564 : tick_freeze_depth--;
565 :
566 : raw_spin_unlock(&tick_freeze_lock);
567 : }
568 : #endif /* CONFIG_SUSPEND */
569 :
570 : /**
571 : * tick_init - initialize the tick control
572 : */
573 1 : void __init tick_init(void)
574 : {
575 1 : tick_broadcast_init();
576 1 : tick_nohz_init();
577 1 : }
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