1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains the base functions to manage periodic tick
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
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>
21 #include <asm/irq_regs.h>
23 #include "tick-internal.h"
28 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
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.
34 ktime_t tick_next_period;
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:
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.
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.
50 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
51 #ifdef CONFIG_NO_HZ_FULL
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.
57 static int tick_do_timer_boot_cpu __read_mostly = -1;
61 * Debugging: see timer_list.c
63 struct tick_device *tick_get_device(int cpu)
65 return &per_cpu(tick_cpu_device, cpu);
69 * tick_is_oneshot_available - check for a oneshot capable event device
71 int tick_is_oneshot_available(void)
73 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
75 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
77 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
79 return tick_broadcast_oneshot_available();
85 static void tick_periodic(int cpu)
87 if (tick_do_timer_cpu == cpu) {
88 raw_spin_lock(&jiffies_lock);
89 write_seqcount_begin(&jiffies_seq);
91 /* Keep track of the next tick event */
92 tick_next_period = ktime_add_ns(tick_next_period, TICK_NSEC);
95 write_seqcount_end(&jiffies_seq);
96 raw_spin_unlock(&jiffies_lock);
100 update_process_times(user_mode(get_irq_regs()));
101 profile_tick(CPU_PROFILING);
105 * Event handler for periodic ticks
107 void tick_handle_periodic(struct clock_event_device *dev)
109 int cpu = smp_processor_id();
110 ktime_t next = dev->next_event;
114 #if defined(CONFIG_HIGH_RES_TIMERS) || defined(CONFIG_NO_HZ_COMMON)
116 * The cpu might have transitioned to HIGHRES or NOHZ mode via
117 * update_process_times() -> run_local_timers() ->
118 * hrtimer_run_queues().
120 if (dev->event_handler != tick_handle_periodic)
124 if (!clockevent_state_oneshot(dev))
128 * Setup the next period for devices, which do not have
131 next = ktime_add_ns(next, TICK_NSEC);
133 if (!clockevents_program_event(dev, next, false))
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.
144 if (timekeeping_valid_for_hres())
150 * Setup the device for a periodic tick
152 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
154 tick_set_periodic_handler(dev, broadcast);
156 /* Broadcast setup ? */
157 if (!tick_device_is_functional(dev))
160 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
161 !tick_broadcast_oneshot_active()) {
162 clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
168 seq = read_seqcount_begin(&jiffies_seq);
169 next = tick_next_period;
170 } while (read_seqcount_retry(&jiffies_seq, seq));
172 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
175 if (!clockevents_program_event(dev, next, false))
177 next = ktime_add_ns(next, TICK_NSEC);
182 #ifdef CONFIG_NO_HZ_FULL
183 static void giveup_do_timer(void *info)
185 int cpu = *(unsigned int *)info;
187 WARN_ON(tick_do_timer_cpu != smp_processor_id());
189 tick_do_timer_cpu = cpu;
192 static void tick_take_do_timer_from_boot(void)
194 int cpu = smp_processor_id();
195 int from = tick_do_timer_boot_cpu;
197 if (from >= 0 && from != cpu)
198 smp_call_function_single(from, giveup_do_timer, &cpu, 1);
203 * Setup the tick device
205 static void tick_setup_device(struct tick_device *td,
206 struct clock_event_device *newdev, int cpu,
207 const struct cpumask *cpumask)
209 void (*handler)(struct clock_event_device *) = NULL;
210 ktime_t next_event = 0;
213 * First device setup ?
217 * If no cpu took the do_timer update, assign it to
220 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
224 tick_do_timer_cpu = cpu;
226 next_p = ktime_get();
227 div_u64_rem(next_p, TICK_NSEC, &rem);
233 tick_next_period = next_p;
234 #ifdef CONFIG_NO_HZ_FULL
236 * The boot CPU may be nohz_full, in which case set
237 * tick_do_timer_boot_cpu so the first housekeeping
238 * secondary that comes up will take do_timer from
241 if (tick_nohz_full_cpu(cpu))
242 tick_do_timer_boot_cpu = cpu;
244 } else if (tick_do_timer_boot_cpu != -1 &&
245 !tick_nohz_full_cpu(cpu)) {
246 tick_take_do_timer_from_boot();
247 tick_do_timer_boot_cpu = -1;
248 WARN_ON(tick_do_timer_cpu != cpu);
253 * Startup in periodic mode first.
255 td->mode = TICKDEV_MODE_PERIODIC;
257 handler = td->evtdev->event_handler;
258 next_event = td->evtdev->next_event;
259 td->evtdev->event_handler = clockevents_handle_noop;
265 * When the device is not per cpu, pin the interrupt to the
268 if (!cpumask_equal(newdev->cpumask, cpumask))
269 irq_set_affinity(newdev->irq, cpumask);
272 * When global broadcasting is active, check if the current
273 * device is registered as a placeholder for broadcast mode.
274 * This allows us to handle this x86 misfeature in a generic
275 * way. This function also returns !=0 when we keep the
276 * current active broadcast state for this CPU.
278 if (tick_device_uses_broadcast(newdev, cpu))
281 if (td->mode == TICKDEV_MODE_PERIODIC)
282 tick_setup_periodic(newdev, 0);
284 tick_setup_oneshot(newdev, handler, next_event);
287 void tick_install_replacement(struct clock_event_device *newdev)
289 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
290 int cpu = smp_processor_id();
292 clockevents_exchange_device(td->evtdev, newdev);
293 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
294 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
295 tick_oneshot_notify();
298 static bool tick_check_percpu(struct clock_event_device *curdev,
299 struct clock_event_device *newdev, int cpu)
301 if (!cpumask_test_cpu(cpu, newdev->cpumask))
303 if (cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
305 /* Check if irq affinity can be set */
306 if (newdev->irq >= 0 && !irq_can_set_affinity(newdev->irq))
308 /* Prefer an existing cpu local device */
309 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
314 static bool tick_check_preferred(struct clock_event_device *curdev,
315 struct clock_event_device *newdev)
317 /* Prefer oneshot capable device */
318 if (!(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) {
319 if (curdev && (curdev->features & CLOCK_EVT_FEAT_ONESHOT))
321 if (tick_oneshot_mode_active())
326 * Use the higher rated one, but prefer a CPU local device with a lower
327 * rating than a non-CPU local device
330 newdev->rating > curdev->rating ||
331 !cpumask_equal(curdev->cpumask, newdev->cpumask);
335 * Check whether the new device is a better fit than curdev. curdev
338 bool tick_check_replacement(struct clock_event_device *curdev,
339 struct clock_event_device *newdev)
341 if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
344 return tick_check_preferred(curdev, newdev);
348 * Check, if the new registered device should be used. Called with
349 * clockevents_lock held and interrupts disabled.
351 void tick_check_new_device(struct clock_event_device *newdev)
353 struct clock_event_device *curdev;
354 struct tick_device *td;
357 cpu = smp_processor_id();
358 td = &per_cpu(tick_cpu_device, cpu);
361 if (!tick_check_replacement(curdev, newdev))
364 if (!try_module_get(newdev->owner))
368 * Replace the eventually existing device by the new
369 * device. If the current device is the broadcast device, do
370 * not give it back to the clockevents layer !
372 if (tick_is_broadcast_device(curdev)) {
373 clockevents_shutdown(curdev);
376 clockevents_exchange_device(curdev, newdev);
377 tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
378 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
379 tick_oneshot_notify();
384 * Can the new device be used as a broadcast device ?
386 tick_install_broadcast_device(newdev, cpu);
390 * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
391 * @state: The target state (enter/exit)
393 * The system enters/leaves a state, where affected devices might stop
394 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
396 * Called with interrupts disabled, so clockevents_lock is not
397 * required here because the local clock event device cannot go away
400 int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
402 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
404 if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
407 return __tick_broadcast_oneshot_control(state);
409 EXPORT_SYMBOL_GPL(tick_broadcast_oneshot_control);
411 #ifdef CONFIG_HOTPLUG_CPU
413 * Transfer the do_timer job away from a dying cpu.
415 * Called with interrupts disabled. No locking required. If
416 * tick_do_timer_cpu is owned by this cpu, nothing can change it.
418 void tick_handover_do_timer(void)
420 if (tick_do_timer_cpu == smp_processor_id())
421 tick_do_timer_cpu = cpumask_first(cpu_online_mask);
425 * Shutdown an event device on a given cpu:
427 * This is called on a life CPU, when a CPU is dead. So we cannot
428 * access the hardware device itself.
429 * We just set the mode and remove it from the lists.
431 void tick_shutdown(unsigned int cpu)
433 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
434 struct clock_event_device *dev = td->evtdev;
436 td->mode = TICKDEV_MODE_PERIODIC;
439 * Prevent that the clock events layer tries to call
440 * the set mode function!
442 clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
443 clockevents_exchange_device(dev, NULL);
444 dev->event_handler = clockevents_handle_noop;
451 * tick_suspend_local - Suspend the local tick device
453 * Called from the local cpu for freeze with interrupts disabled.
455 * No locks required. Nothing can change the per cpu device.
457 void tick_suspend_local(void)
459 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
461 clockevents_shutdown(td->evtdev);
465 * tick_resume_local - Resume the local tick device
467 * Called from the local CPU for unfreeze or XEN resume magic.
469 * No locks required. Nothing can change the per cpu device.
471 void tick_resume_local(void)
473 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
474 bool broadcast = tick_resume_check_broadcast();
476 clockevents_tick_resume(td->evtdev);
478 if (td->mode == TICKDEV_MODE_PERIODIC)
479 tick_setup_periodic(td->evtdev, 0);
481 tick_resume_oneshot();
485 * Ensure that hrtimers are up to date and the clockevents device
486 * is reprogrammed correctly when high resolution timers are
489 hrtimers_resume_local();
493 * tick_suspend - Suspend the tick and the broadcast device
495 * Called from syscore_suspend() via timekeeping_suspend with only one
496 * CPU online and interrupts disabled or from tick_unfreeze() under
499 * No locks required. Nothing can change the per cpu device.
501 void tick_suspend(void)
503 tick_suspend_local();
504 tick_suspend_broadcast();
508 * tick_resume - Resume the tick and the broadcast device
510 * Called from syscore_resume() via timekeeping_resume with only one
511 * CPU online and interrupts disabled.
513 * No locks required. Nothing can change the per cpu device.
515 void tick_resume(void)
517 tick_resume_broadcast();
521 #ifdef CONFIG_SUSPEND
522 static DEFINE_RAW_SPINLOCK(tick_freeze_lock);
523 static unsigned int tick_freeze_depth;
526 * tick_freeze - Suspend the local tick and (possibly) timekeeping.
528 * Check if this is the last online CPU executing the function and if so,
529 * suspend timekeeping. Otherwise suspend the local tick.
531 * Call with interrupts disabled. Must be balanced with %tick_unfreeze().
532 * Interrupts must not be enabled before the subsequent %tick_unfreeze().
534 void tick_freeze(void)
536 raw_spin_lock(&tick_freeze_lock);
539 if (tick_freeze_depth == num_online_cpus()) {
540 trace_suspend_resume(TPS("timekeeping_freeze"),
541 smp_processor_id(), true);
542 system_state = SYSTEM_SUSPEND;
543 sched_clock_suspend();
544 timekeeping_suspend();
546 tick_suspend_local();
549 raw_spin_unlock(&tick_freeze_lock);
553 * tick_unfreeze - Resume the local tick and (possibly) timekeeping.
555 * Check if this is the first CPU executing the function and if so, resume
556 * timekeeping. Otherwise resume the local tick.
558 * Call with interrupts disabled. Must be balanced with %tick_freeze().
559 * Interrupts must not be enabled after the preceding %tick_freeze().
561 void tick_unfreeze(void)
563 raw_spin_lock(&tick_freeze_lock);
565 if (tick_freeze_depth == num_online_cpus()) {
566 timekeeping_resume();
567 sched_clock_resume();
568 system_state = SYSTEM_RUNNING;
569 trace_suspend_resume(TPS("timekeeping_freeze"),
570 smp_processor_id(), false);
572 touch_softlockup_watchdog();
578 raw_spin_unlock(&tick_freeze_lock);
580 #endif /* CONFIG_SUSPEND */
583 * tick_init - initialize the tick control
585 void __init tick_init(void)
587 tick_broadcast_init();