1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains functions which emulate a local clock-event
4 * device via a broadcast event source.
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/percpu.h>
15 #include <linux/profile.h>
16 #include <linux/sched.h>
17 #include <linux/smp.h>
18 #include <linux/module.h>
20 #include "tick-internal.h"
23 * Broadcast support for broken x86 hardware, where the local apic
24 * timer stops in C3 state.
27 static struct tick_device tick_broadcast_device;
28 static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
29 static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
30 static cpumask_var_t tmpmask __cpumask_var_read_mostly;
31 static int tick_broadcast_forced;
33 static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
35 #ifdef CONFIG_TICK_ONESHOT
36 static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
38 static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);
39 static void tick_broadcast_clear_oneshot(int cpu);
40 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
41 # ifdef CONFIG_HOTPLUG_CPU
42 static void tick_broadcast_oneshot_offline(unsigned int cpu);
46 tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
47 static inline void tick_broadcast_clear_oneshot(int cpu) { }
48 static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
49 # ifdef CONFIG_HOTPLUG_CPU
50 static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
55 * Debugging: see timer_list.c
57 struct tick_device *tick_get_broadcast_device(void)
59 return &tick_broadcast_device;
62 struct cpumask *tick_get_broadcast_mask(void)
64 return tick_broadcast_mask;
67 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
69 const struct clock_event_device *tick_get_wakeup_device(int cpu)
71 return tick_get_oneshot_wakeup_device(cpu);
75 * Start the device in periodic mode
77 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
80 tick_setup_periodic(bc, 1);
84 * Check, if the device can be utilized as broadcast device:
86 static bool tick_check_broadcast_device(struct clock_event_device *curdev,
87 struct clock_event_device *newdev)
89 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
90 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
91 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
94 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
95 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
98 return !curdev || newdev->rating > curdev->rating;
101 #ifdef CONFIG_TICK_ONESHOT
102 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
104 return per_cpu(tick_oneshot_wakeup_device, cpu);
107 static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
110 * If we woke up early and the tick was reprogrammed in the
111 * meantime then this may be spurious but harmless.
113 tick_receive_broadcast();
116 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
119 struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
124 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
125 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
128 if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
129 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
132 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
135 if (curdev && newdev->rating <= curdev->rating)
138 if (!try_module_get(newdev->owner))
141 newdev->event_handler = tick_oneshot_wakeup_handler;
143 clockevents_exchange_device(curdev, newdev);
144 per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
148 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
153 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
161 * Conditionally install/replace broadcast device
163 void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
165 struct clock_event_device *cur = tick_broadcast_device.evtdev;
167 if (tick_set_oneshot_wakeup_device(dev, cpu))
170 if (!tick_check_broadcast_device(cur, dev))
173 if (!try_module_get(dev->owner))
176 clockevents_exchange_device(cur, dev);
178 cur->event_handler = clockevents_handle_noop;
179 tick_broadcast_device.evtdev = dev;
180 if (!cpumask_empty(tick_broadcast_mask))
181 tick_broadcast_start_periodic(dev);
183 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
187 * If the system already runs in oneshot mode, switch the newly
188 * registered broadcast device to oneshot mode explicitly.
190 if (tick_broadcast_oneshot_active()) {
191 tick_broadcast_switch_to_oneshot();
196 * Inform all cpus about this. We might be in a situation
197 * where we did not switch to oneshot mode because the per cpu
198 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
199 * of a oneshot capable broadcast device. Without that
200 * notification the systems stays stuck in periodic mode
207 * Check, if the device is the broadcast device
209 int tick_is_broadcast_device(struct clock_event_device *dev)
211 return (dev && tick_broadcast_device.evtdev == dev);
214 int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
218 if (tick_is_broadcast_device(dev)) {
219 raw_spin_lock(&tick_broadcast_lock);
220 ret = __clockevents_update_freq(dev, freq);
221 raw_spin_unlock(&tick_broadcast_lock);
227 static void err_broadcast(const struct cpumask *mask)
229 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
232 static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
235 dev->broadcast = tick_broadcast;
236 if (!dev->broadcast) {
237 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
239 dev->broadcast = err_broadcast;
244 * Check, if the device is dysfunctional and a placeholder, which
245 * needs to be handled by the broadcast device.
247 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
249 struct clock_event_device *bc = tick_broadcast_device.evtdev;
253 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
256 * Devices might be registered with both periodic and oneshot
257 * mode disabled. This signals, that the device needs to be
258 * operated from the broadcast device and is a placeholder for
259 * the cpu local device.
261 if (!tick_device_is_functional(dev)) {
262 dev->event_handler = tick_handle_periodic;
263 tick_device_setup_broadcast_func(dev);
264 cpumask_set_cpu(cpu, tick_broadcast_mask);
265 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
266 tick_broadcast_start_periodic(bc);
268 tick_broadcast_setup_oneshot(bc, false);
272 * Clear the broadcast bit for this cpu if the
273 * device is not power state affected.
275 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
276 cpumask_clear_cpu(cpu, tick_broadcast_mask);
278 tick_device_setup_broadcast_func(dev);
281 * Clear the broadcast bit if the CPU is not in
282 * periodic broadcast on state.
284 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
285 cpumask_clear_cpu(cpu, tick_broadcast_mask);
287 switch (tick_broadcast_device.mode) {
288 case TICKDEV_MODE_ONESHOT:
290 * If the system is in oneshot mode we can
291 * unconditionally clear the oneshot mask bit,
292 * because the CPU is running and therefore
293 * not in an idle state which causes the power
294 * state affected device to stop. Let the
295 * caller initialize the device.
297 tick_broadcast_clear_oneshot(cpu);
301 case TICKDEV_MODE_PERIODIC:
303 * If the system is in periodic mode, check
304 * whether the broadcast device can be
307 if (cpumask_empty(tick_broadcast_mask) && bc)
308 clockevents_shutdown(bc);
310 * If we kept the cpu in the broadcast mask,
311 * tell the caller to leave the per cpu device
312 * in shutdown state. The periodic interrupt
313 * is delivered by the broadcast device, if
314 * the broadcast device exists and is not
317 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
318 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
324 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
328 int tick_receive_broadcast(void)
330 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
331 struct clock_event_device *evt = td->evtdev;
336 if (!evt->event_handler)
339 evt->event_handler(evt);
344 * Broadcast the event to the cpus, which are set in the mask (mangled).
346 static bool tick_do_broadcast(struct cpumask *mask)
348 int cpu = smp_processor_id();
349 struct tick_device *td;
353 * Check, if the current cpu is in the mask
355 if (cpumask_test_cpu(cpu, mask)) {
356 struct clock_event_device *bc = tick_broadcast_device.evtdev;
358 cpumask_clear_cpu(cpu, mask);
360 * We only run the local handler, if the broadcast
361 * device is not hrtimer based. Otherwise we run into
362 * a hrtimer recursion.
364 * local timer_interrupt()
371 local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
374 if (!cpumask_empty(mask)) {
376 * It might be necessary to actually check whether the devices
377 * have different broadcast functions. For now, just use the
378 * one of the first device. This works as long as we have this
379 * misfeature only on x86 (lapic)
381 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
382 td->evtdev->broadcast(mask);
388 * Periodic broadcast:
389 * - invoke the broadcast handlers
391 static bool tick_do_periodic_broadcast(void)
393 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
394 return tick_do_broadcast(tmpmask);
398 * Event handler for periodic broadcast ticks
400 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
402 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
405 raw_spin_lock(&tick_broadcast_lock);
407 /* Handle spurious interrupts gracefully */
408 if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
409 raw_spin_unlock(&tick_broadcast_lock);
413 bc_local = tick_do_periodic_broadcast();
415 if (clockevent_state_oneshot(dev)) {
416 ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
418 clockevents_program_event(dev, next, true);
420 raw_spin_unlock(&tick_broadcast_lock);
423 * We run the handler of the local cpu after dropping
424 * tick_broadcast_lock because the handler might deadlock when
425 * trying to switch to oneshot mode.
428 td->evtdev->event_handler(td->evtdev);
432 * tick_broadcast_control - Enable/disable or force broadcast mode
433 * @mode: The selected broadcast mode
435 * Called when the system enters a state where affected tick devices
436 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
438 void tick_broadcast_control(enum tick_broadcast_mode mode)
440 struct clock_event_device *bc, *dev;
441 struct tick_device *td;
445 /* Protects also the local clockevent device. */
446 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
447 td = this_cpu_ptr(&tick_cpu_device);
451 * Is the device not affected by the powerstate ?
453 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
456 if (!tick_device_is_functional(dev))
459 cpu = smp_processor_id();
460 bc = tick_broadcast_device.evtdev;
461 bc_stopped = cpumask_empty(tick_broadcast_mask);
464 case TICK_BROADCAST_FORCE:
465 tick_broadcast_forced = 1;
467 case TICK_BROADCAST_ON:
468 cpumask_set_cpu(cpu, tick_broadcast_on);
469 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
471 * Only shutdown the cpu local device, if:
473 * - the broadcast device exists
474 * - the broadcast device is not a hrtimer based one
475 * - the broadcast device is in periodic mode to
476 * avoid a hiccup during switch to oneshot mode
478 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
479 tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
480 clockevents_shutdown(dev);
484 case TICK_BROADCAST_OFF:
485 if (tick_broadcast_forced)
487 cpumask_clear_cpu(cpu, tick_broadcast_on);
488 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
489 if (tick_broadcast_device.mode ==
490 TICKDEV_MODE_PERIODIC)
491 tick_setup_periodic(dev, 0);
497 if (cpumask_empty(tick_broadcast_mask)) {
499 clockevents_shutdown(bc);
500 } else if (bc_stopped) {
501 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
502 tick_broadcast_start_periodic(bc);
504 tick_broadcast_setup_oneshot(bc, false);
508 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
510 EXPORT_SYMBOL_GPL(tick_broadcast_control);
513 * Set the periodic handler depending on broadcast on/off
515 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
518 dev->event_handler = tick_handle_periodic;
520 dev->event_handler = tick_handle_periodic_broadcast;
523 #ifdef CONFIG_HOTPLUG_CPU
524 static void tick_shutdown_broadcast(void)
526 struct clock_event_device *bc = tick_broadcast_device.evtdev;
528 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
529 if (bc && cpumask_empty(tick_broadcast_mask))
530 clockevents_shutdown(bc);
535 * Remove a CPU from broadcasting
537 void tick_broadcast_offline(unsigned int cpu)
539 raw_spin_lock(&tick_broadcast_lock);
540 cpumask_clear_cpu(cpu, tick_broadcast_mask);
541 cpumask_clear_cpu(cpu, tick_broadcast_on);
542 tick_broadcast_oneshot_offline(cpu);
543 tick_shutdown_broadcast();
544 raw_spin_unlock(&tick_broadcast_lock);
549 void tick_suspend_broadcast(void)
551 struct clock_event_device *bc;
554 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
556 bc = tick_broadcast_device.evtdev;
558 clockevents_shutdown(bc);
560 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
564 * This is called from tick_resume_local() on a resuming CPU. That's
565 * called from the core resume function, tick_unfreeze() and the magic XEN
568 * In none of these cases the broadcast device mode can change and the
569 * bit of the resuming CPU in the broadcast mask is safe as well.
571 bool tick_resume_check_broadcast(void)
573 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
576 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
579 void tick_resume_broadcast(void)
581 struct clock_event_device *bc;
584 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
586 bc = tick_broadcast_device.evtdev;
589 clockevents_tick_resume(bc);
591 switch (tick_broadcast_device.mode) {
592 case TICKDEV_MODE_PERIODIC:
593 if (!cpumask_empty(tick_broadcast_mask))
594 tick_broadcast_start_periodic(bc);
596 case TICKDEV_MODE_ONESHOT:
597 if (!cpumask_empty(tick_broadcast_mask))
598 tick_resume_broadcast_oneshot(bc);
602 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
605 #ifdef CONFIG_TICK_ONESHOT
607 static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
608 static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
609 static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
612 * Exposed for debugging: see timer_list.c
614 struct cpumask *tick_get_broadcast_oneshot_mask(void)
616 return tick_broadcast_oneshot_mask;
620 * Called before going idle with interrupts disabled. Checks whether a
621 * broadcast event from the other core is about to happen. We detected
622 * that in tick_broadcast_oneshot_control(). The callsite can use this
623 * to avoid a deep idle transition as we are about to get the
624 * broadcast IPI right away.
626 int tick_check_broadcast_expired(void)
628 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
632 * Set broadcast interrupt affinity
634 static void tick_broadcast_set_affinity(struct clock_event_device *bc,
635 const struct cpumask *cpumask)
637 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
640 if (cpumask_equal(bc->cpumask, cpumask))
643 bc->cpumask = cpumask;
644 irq_set_affinity(bc->irq, bc->cpumask);
647 static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
650 if (!clockevent_state_oneshot(bc))
651 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
653 clockevents_program_event(bc, expires, 1);
654 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
657 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
659 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
663 * Called from irq_enter() when idle was interrupted to reenable the
666 void tick_check_oneshot_broadcast_this_cpu(void)
668 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
669 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
672 * We might be in the middle of switching over from
673 * periodic to oneshot. If the CPU has not yet
674 * switched over, leave the device alone.
676 if (td->mode == TICKDEV_MODE_ONESHOT) {
677 clockevents_switch_state(td->evtdev,
678 CLOCK_EVT_STATE_ONESHOT);
684 * Handle oneshot mode broadcasting
686 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
688 struct tick_device *td;
689 ktime_t now, next_event;
690 int cpu, next_cpu = 0;
693 raw_spin_lock(&tick_broadcast_lock);
694 dev->next_event = KTIME_MAX;
695 next_event = KTIME_MAX;
696 cpumask_clear(tmpmask);
698 /* Find all expired events */
699 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
701 * Required for !SMP because for_each_cpu() reports
702 * unconditionally CPU0 as set on UP kernels.
704 if (!IS_ENABLED(CONFIG_SMP) &&
705 cpumask_empty(tick_broadcast_oneshot_mask))
708 td = &per_cpu(tick_cpu_device, cpu);
709 if (td->evtdev->next_event <= now) {
710 cpumask_set_cpu(cpu, tmpmask);
712 * Mark the remote cpu in the pending mask, so
713 * it can avoid reprogramming the cpu local
714 * timer in tick_broadcast_oneshot_control().
716 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
717 } else if (td->evtdev->next_event < next_event) {
718 next_event = td->evtdev->next_event;
724 * Remove the current cpu from the pending mask. The event is
725 * delivered immediately in tick_do_broadcast() !
727 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
729 /* Take care of enforced broadcast requests */
730 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
731 cpumask_clear(tick_broadcast_force_mask);
734 * Sanity check. Catch the case where we try to broadcast to
737 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
738 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
741 * Wakeup the cpus which have an expired event.
743 bc_local = tick_do_broadcast(tmpmask);
746 * Two reasons for reprogram:
748 * - The global event did not expire any CPU local
749 * events. This happens in dyntick mode, as the maximum PIT
750 * delta is quite small.
752 * - There are pending events on sleeping CPUs which were not
755 if (next_event != KTIME_MAX)
756 tick_broadcast_set_event(dev, next_cpu, next_event);
758 raw_spin_unlock(&tick_broadcast_lock);
761 td = this_cpu_ptr(&tick_cpu_device);
762 td->evtdev->event_handler(td->evtdev);
766 static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
768 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
770 if (bc->next_event == KTIME_MAX)
772 return bc->bound_on == cpu ? -EBUSY : 0;
775 static void broadcast_shutdown_local(struct clock_event_device *bc,
776 struct clock_event_device *dev)
779 * For hrtimer based broadcasting we cannot shutdown the cpu
780 * local device if our own event is the first one to expire or
781 * if we own the broadcast timer.
783 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
784 if (broadcast_needs_cpu(bc, smp_processor_id()))
786 if (dev->next_event < bc->next_event)
789 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
792 static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
793 struct tick_device *td,
796 struct clock_event_device *bc, *dev = td->evtdev;
800 raw_spin_lock(&tick_broadcast_lock);
801 bc = tick_broadcast_device.evtdev;
803 if (state == TICK_BROADCAST_ENTER) {
805 * If the current CPU owns the hrtimer broadcast
806 * mechanism, it cannot go deep idle and we do not add
807 * the CPU to the broadcast mask. We don't have to go
808 * through the EXIT path as the local timer is not
811 ret = broadcast_needs_cpu(bc, cpu);
816 * If the broadcast device is in periodic mode, we
819 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
820 /* If it is a hrtimer based broadcast, return busy */
821 if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
826 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
827 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
829 /* Conditionally shut down the local timer. */
830 broadcast_shutdown_local(bc, dev);
833 * We only reprogram the broadcast timer if we
834 * did not mark ourself in the force mask and
835 * if the cpu local event is earlier than the
836 * broadcast event. If the current CPU is in
837 * the force mask, then we are going to be
838 * woken by the IPI right away; we return
839 * busy, so the CPU does not try to go deep
842 if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
844 } else if (dev->next_event < bc->next_event) {
845 tick_broadcast_set_event(bc, cpu, dev->next_event);
847 * In case of hrtimer broadcasts the
848 * programming might have moved the
849 * timer to this cpu. If yes, remove
850 * us from the broadcast mask and
853 ret = broadcast_needs_cpu(bc, cpu);
855 cpumask_clear_cpu(cpu,
856 tick_broadcast_oneshot_mask);
861 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
862 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
864 * The cpu which was handling the broadcast
865 * timer marked this cpu in the broadcast
866 * pending mask and fired the broadcast
867 * IPI. So we are going to handle the expired
868 * event anyway via the broadcast IPI
869 * handler. No need to reprogram the timer
870 * with an already expired event.
872 if (cpumask_test_and_clear_cpu(cpu,
873 tick_broadcast_pending_mask))
877 * Bail out if there is no next event.
879 if (dev->next_event == KTIME_MAX)
882 * If the pending bit is not set, then we are
883 * either the CPU handling the broadcast
884 * interrupt or we got woken by something else.
886 * We are no longer in the broadcast mask, so
887 * if the cpu local expiry time is already
888 * reached, we would reprogram the cpu local
889 * timer with an already expired event.
891 * This can lead to a ping-pong when we return
892 * to idle and therefore rearm the broadcast
893 * timer before the cpu local timer was able
894 * to fire. This happens because the forced
895 * reprogramming makes sure that the event
896 * will happen in the future and depending on
897 * the min_delta setting this might be far
898 * enough out that the ping-pong starts.
900 * If the cpu local next_event has expired
901 * then we know that the broadcast timer
902 * next_event has expired as well and
903 * broadcast is about to be handled. So we
904 * avoid reprogramming and enforce that the
905 * broadcast handler, which did not run yet,
906 * will invoke the cpu local handler.
908 * We cannot call the handler directly from
909 * here, because we might be in a NOHZ phase
910 * and we did not go through the irq_enter()
914 if (dev->next_event <= now) {
915 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
919 * We got woken by something else. Reprogram
920 * the cpu local timer device.
922 tick_program_event(dev->next_event, 1);
926 raw_spin_unlock(&tick_broadcast_lock);
930 static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
931 struct tick_device *td,
934 struct clock_event_device *dev, *wd;
937 if (td->mode != TICKDEV_MODE_ONESHOT)
940 wd = tick_get_oneshot_wakeup_device(cpu);
945 case TICK_BROADCAST_ENTER:
946 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
947 clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
948 clockevents_program_event(wd, dev->next_event, 1);
950 case TICK_BROADCAST_EXIT:
951 /* We may have transitioned to oneshot mode while idle */
952 if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
959 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
961 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
962 int cpu = smp_processor_id();
964 if (!tick_oneshot_wakeup_control(state, td, cpu))
967 if (tick_broadcast_device.evtdev)
968 return ___tick_broadcast_oneshot_control(state, td, cpu);
971 * If there is no broadcast or wakeup device, tell the caller not
972 * to go into deep idle.
978 * Reset the one shot broadcast for a cpu
980 * Called with tick_broadcast_lock held
982 static void tick_broadcast_clear_oneshot(int cpu)
984 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
985 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
988 static void tick_broadcast_init_next_event(struct cpumask *mask,
991 struct tick_device *td;
994 for_each_cpu(cpu, mask) {
995 td = &per_cpu(tick_cpu_device, cpu);
997 td->evtdev->next_event = expires;
1001 static inline ktime_t tick_get_next_period(void)
1006 * Protect against concurrent updates (store /load tearing on
1007 * 32bit). It does not matter if the time is already in the
1008 * past. The broadcast device which is about to be programmed will
1011 raw_spin_lock(&jiffies_lock);
1012 next = tick_next_period;
1013 raw_spin_unlock(&jiffies_lock);
1018 * tick_broadcast_setup_oneshot - setup the broadcast device
1020 static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
1023 int cpu = smp_processor_id();
1024 ktime_t nexttick = 0;
1030 * When the broadcast device was switched to oneshot by the first
1031 * CPU handling the NOHZ change, the other CPUs will reach this
1032 * code via hrtimer_run_queues() -> tick_check_oneshot_change()
1033 * too. Set up the broadcast device only once!
1035 if (bc->event_handler == tick_handle_oneshot_broadcast) {
1037 * The CPU which switched from periodic to oneshot mode
1038 * set the broadcast oneshot bit for all other CPUs which
1039 * are in the general (periodic) broadcast mask to ensure
1040 * that CPUs which wait for the periodic broadcast are
1043 * Clear the bit for the local CPU as the set bit would
1044 * prevent the first tick_broadcast_enter() after this CPU
1045 * switched to oneshot state to program the broadcast
1048 * This code can also be reached via tick_broadcast_control(),
1049 * but this cannot avoid the tick_broadcast_clear_oneshot()
1050 * as that would break the periodic to oneshot transition of
1051 * secondary CPUs. But that's harmless as the below only
1052 * clears already cleared bits.
1054 tick_broadcast_clear_oneshot(cpu);
1059 bc->event_handler = tick_handle_oneshot_broadcast;
1060 bc->next_event = KTIME_MAX;
1063 * When the tick mode is switched from periodic to oneshot it must
1064 * be ensured that CPUs which are waiting for periodic broadcast
1065 * get their wake-up at the next tick. This is achieved by ORing
1066 * tick_broadcast_mask into tick_broadcast_oneshot_mask.
1068 * For other callers, e.g. broadcast device replacement,
1069 * tick_broadcast_oneshot_mask must not be touched as this would
1070 * set bits for CPUs which are already NOHZ, but not idle. Their
1071 * next tick_broadcast_enter() would observe the bit set and fail
1072 * to update the expiry time and the broadcast event device.
1074 if (from_periodic) {
1075 cpumask_copy(tmpmask, tick_broadcast_mask);
1076 /* Remove the local CPU as it is obviously not idle */
1077 cpumask_clear_cpu(cpu, tmpmask);
1078 cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
1081 * Ensure that the oneshot broadcast handler will wake the
1082 * CPUs which are still waiting for periodic broadcast.
1084 nexttick = tick_get_next_period();
1085 tick_broadcast_init_next_event(tmpmask, nexttick);
1088 * If the underlying broadcast clock event device is
1089 * already in oneshot state, then there is nothing to do.
1090 * The device was already armed for the next tick
1091 * in tick_handle_broadcast_periodic()
1093 if (clockevent_state_oneshot(bc))
1098 * When switching from periodic to oneshot mode arm the broadcast
1099 * device for the next tick.
1101 * If the broadcast device has been replaced in oneshot mode and
1102 * the oneshot broadcast mask is not empty, then arm it to expire
1103 * immediately in order to reevaluate the next expiring timer.
1104 * @nexttick is 0 and therefore in the past which will cause the
1105 * clockevent code to force an event.
1107 * For both cases the programming can be avoided when the oneshot
1108 * broadcast mask is empty.
1110 * tick_broadcast_set_event() implicitly switches the broadcast
1111 * device to oneshot state.
1113 if (!cpumask_empty(tick_broadcast_oneshot_mask))
1114 tick_broadcast_set_event(bc, cpu, nexttick);
1118 * Select oneshot operating mode for the broadcast device
1120 void tick_broadcast_switch_to_oneshot(void)
1122 struct clock_event_device *bc;
1123 enum tick_device_mode oldmode;
1124 unsigned long flags;
1126 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1128 oldmode = tick_broadcast_device.mode;
1129 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
1130 bc = tick_broadcast_device.evtdev;
1132 tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
1134 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1137 #ifdef CONFIG_HOTPLUG_CPU
1138 void hotplug_cpu__broadcast_tick_pull(int deadcpu)
1140 struct clock_event_device *bc;
1141 unsigned long flags;
1143 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1144 bc = tick_broadcast_device.evtdev;
1146 if (bc && broadcast_needs_cpu(bc, deadcpu)) {
1147 /* This moves the broadcast assignment to this CPU: */
1148 clockevents_program_event(bc, bc->next_event, 1);
1150 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1154 * Remove a dying CPU from broadcasting
1156 static void tick_broadcast_oneshot_offline(unsigned int cpu)
1158 if (tick_get_oneshot_wakeup_device(cpu))
1159 tick_set_oneshot_wakeup_device(NULL, cpu);
1162 * Clear the broadcast masks for the dead cpu, but do not stop
1163 * the broadcast device!
1165 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
1166 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
1167 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
1172 * Check, whether the broadcast device is in one shot mode
1174 int tick_broadcast_oneshot_active(void)
1176 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
1180 * Check whether the broadcast device supports oneshot.
1182 bool tick_broadcast_oneshot_available(void)
1184 struct clock_event_device *bc = tick_broadcast_device.evtdev;
1186 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
1190 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
1192 struct clock_event_device *bc = tick_broadcast_device.evtdev;
1194 if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1201 void __init tick_broadcast_init(void)
1203 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1204 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1205 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1206 #ifdef CONFIG_TICK_ONESHOT
1207 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1208 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1209 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);