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);
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);
45 static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
46 static inline void tick_broadcast_clear_oneshot(int cpu) { }
47 static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
48 # ifdef CONFIG_HOTPLUG_CPU
49 static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
54 * Debugging: see timer_list.c
56 struct tick_device *tick_get_broadcast_device(void)
58 return &tick_broadcast_device;
61 struct cpumask *tick_get_broadcast_mask(void)
63 return tick_broadcast_mask;
66 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
68 const struct clock_event_device *tick_get_wakeup_device(int cpu)
70 return tick_get_oneshot_wakeup_device(cpu);
74 * Start the device in periodic mode
76 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
79 tick_setup_periodic(bc, 1);
83 * Check, if the device can be utilized as broadcast device:
85 static bool tick_check_broadcast_device(struct clock_event_device *curdev,
86 struct clock_event_device *newdev)
88 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
89 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
90 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
93 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
94 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
97 return !curdev || newdev->rating > curdev->rating;
100 #ifdef CONFIG_TICK_ONESHOT
101 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
103 return per_cpu(tick_oneshot_wakeup_device, cpu);
106 static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
109 * If we woke up early and the tick was reprogrammed in the
110 * meantime then this may be spurious but harmless.
112 tick_receive_broadcast();
115 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
118 struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
123 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
124 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
127 if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
128 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
131 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
134 if (curdev && newdev->rating <= curdev->rating)
137 if (!try_module_get(newdev->owner))
140 newdev->event_handler = tick_oneshot_wakeup_handler;
142 clockevents_exchange_device(curdev, newdev);
143 per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
147 static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
152 static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
160 * Conditionally install/replace broadcast device
162 void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
164 struct clock_event_device *cur = tick_broadcast_device.evtdev;
166 if (tick_set_oneshot_wakeup_device(dev, cpu))
169 if (!tick_check_broadcast_device(cur, dev))
172 if (!try_module_get(dev->owner))
175 clockevents_exchange_device(cur, dev);
177 cur->event_handler = clockevents_handle_noop;
178 tick_broadcast_device.evtdev = dev;
179 if (!cpumask_empty(tick_broadcast_mask))
180 tick_broadcast_start_periodic(dev);
182 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
186 * If the system already runs in oneshot mode, switch the newly
187 * registered broadcast device to oneshot mode explicitly.
189 if (tick_broadcast_oneshot_active()) {
190 tick_broadcast_switch_to_oneshot();
195 * Inform all cpus about this. We might be in a situation
196 * where we did not switch to oneshot mode because the per cpu
197 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
198 * of a oneshot capable broadcast device. Without that
199 * notification the systems stays stuck in periodic mode
206 * Check, if the device is the broadcast device
208 int tick_is_broadcast_device(struct clock_event_device *dev)
210 return (dev && tick_broadcast_device.evtdev == dev);
213 int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
217 if (tick_is_broadcast_device(dev)) {
218 raw_spin_lock(&tick_broadcast_lock);
219 ret = __clockevents_update_freq(dev, freq);
220 raw_spin_unlock(&tick_broadcast_lock);
226 static void err_broadcast(const struct cpumask *mask)
228 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
231 static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
234 dev->broadcast = tick_broadcast;
235 if (!dev->broadcast) {
236 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
238 dev->broadcast = err_broadcast;
243 * Check, if the device is dysfunctional and a placeholder, which
244 * needs to be handled by the broadcast device.
246 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
248 struct clock_event_device *bc = tick_broadcast_device.evtdev;
252 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
255 * Devices might be registered with both periodic and oneshot
256 * mode disabled. This signals, that the device needs to be
257 * operated from the broadcast device and is a placeholder for
258 * the cpu local device.
260 if (!tick_device_is_functional(dev)) {
261 dev->event_handler = tick_handle_periodic;
262 tick_device_setup_broadcast_func(dev);
263 cpumask_set_cpu(cpu, tick_broadcast_mask);
264 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
265 tick_broadcast_start_periodic(bc);
267 tick_broadcast_setup_oneshot(bc);
271 * Clear the broadcast bit for this cpu if the
272 * device is not power state affected.
274 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
275 cpumask_clear_cpu(cpu, tick_broadcast_mask);
277 tick_device_setup_broadcast_func(dev);
280 * Clear the broadcast bit if the CPU is not in
281 * periodic broadcast on state.
283 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
284 cpumask_clear_cpu(cpu, tick_broadcast_mask);
286 switch (tick_broadcast_device.mode) {
287 case TICKDEV_MODE_ONESHOT:
289 * If the system is in oneshot mode we can
290 * unconditionally clear the oneshot mask bit,
291 * because the CPU is running and therefore
292 * not in an idle state which causes the power
293 * state affected device to stop. Let the
294 * caller initialize the device.
296 tick_broadcast_clear_oneshot(cpu);
300 case TICKDEV_MODE_PERIODIC:
302 * If the system is in periodic mode, check
303 * whether the broadcast device can be
306 if (cpumask_empty(tick_broadcast_mask) && bc)
307 clockevents_shutdown(bc);
309 * If we kept the cpu in the broadcast mask,
310 * tell the caller to leave the per cpu device
311 * in shutdown state. The periodic interrupt
312 * is delivered by the broadcast device, if
313 * the broadcast device exists and is not
316 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
317 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
323 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
327 int tick_receive_broadcast(void)
329 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
330 struct clock_event_device *evt = td->evtdev;
335 if (!evt->event_handler)
338 evt->event_handler(evt);
343 * Broadcast the event to the cpus, which are set in the mask (mangled).
345 static bool tick_do_broadcast(struct cpumask *mask)
347 int cpu = smp_processor_id();
348 struct tick_device *td;
352 * Check, if the current cpu is in the mask
354 if (cpumask_test_cpu(cpu, mask)) {
355 struct clock_event_device *bc = tick_broadcast_device.evtdev;
357 cpumask_clear_cpu(cpu, mask);
359 * We only run the local handler, if the broadcast
360 * device is not hrtimer based. Otherwise we run into
361 * a hrtimer recursion.
363 * local timer_interrupt()
370 local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
373 if (!cpumask_empty(mask)) {
375 * It might be necessary to actually check whether the devices
376 * have different broadcast functions. For now, just use the
377 * one of the first device. This works as long as we have this
378 * misfeature only on x86 (lapic)
380 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
381 td->evtdev->broadcast(mask);
387 * Periodic broadcast:
388 * - invoke the broadcast handlers
390 static bool tick_do_periodic_broadcast(void)
392 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
393 return tick_do_broadcast(tmpmask);
397 * Event handler for periodic broadcast ticks
399 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
401 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
404 raw_spin_lock(&tick_broadcast_lock);
406 /* Handle spurious interrupts gracefully */
407 if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
408 raw_spin_unlock(&tick_broadcast_lock);
412 bc_local = tick_do_periodic_broadcast();
414 if (clockevent_state_oneshot(dev)) {
415 ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
417 clockevents_program_event(dev, next, true);
419 raw_spin_unlock(&tick_broadcast_lock);
422 * We run the handler of the local cpu after dropping
423 * tick_broadcast_lock because the handler might deadlock when
424 * trying to switch to oneshot mode.
427 td->evtdev->event_handler(td->evtdev);
431 * tick_broadcast_control - Enable/disable or force broadcast mode
432 * @mode: The selected broadcast mode
434 * Called when the system enters a state where affected tick devices
435 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
437 void tick_broadcast_control(enum tick_broadcast_mode mode)
439 struct clock_event_device *bc, *dev;
440 struct tick_device *td;
444 /* Protects also the local clockevent device. */
445 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
446 td = this_cpu_ptr(&tick_cpu_device);
450 * Is the device not affected by the powerstate ?
452 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
455 if (!tick_device_is_functional(dev))
458 cpu = smp_processor_id();
459 bc = tick_broadcast_device.evtdev;
460 bc_stopped = cpumask_empty(tick_broadcast_mask);
463 case TICK_BROADCAST_FORCE:
464 tick_broadcast_forced = 1;
466 case TICK_BROADCAST_ON:
467 cpumask_set_cpu(cpu, tick_broadcast_on);
468 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
470 * Only shutdown the cpu local device, if:
472 * - the broadcast device exists
473 * - the broadcast device is not a hrtimer based one
474 * - the broadcast device is in periodic mode to
475 * avoid a hiccup during switch to oneshot mode
477 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
478 tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
479 clockevents_shutdown(dev);
483 case TICK_BROADCAST_OFF:
484 if (tick_broadcast_forced)
486 cpumask_clear_cpu(cpu, tick_broadcast_on);
487 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
488 if (tick_broadcast_device.mode ==
489 TICKDEV_MODE_PERIODIC)
490 tick_setup_periodic(dev, 0);
496 if (cpumask_empty(tick_broadcast_mask)) {
498 clockevents_shutdown(bc);
499 } else if (bc_stopped) {
500 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
501 tick_broadcast_start_periodic(bc);
503 tick_broadcast_setup_oneshot(bc);
507 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
509 EXPORT_SYMBOL_GPL(tick_broadcast_control);
512 * Set the periodic handler depending on broadcast on/off
514 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
517 dev->event_handler = tick_handle_periodic;
519 dev->event_handler = tick_handle_periodic_broadcast;
522 #ifdef CONFIG_HOTPLUG_CPU
523 static void tick_shutdown_broadcast(void)
525 struct clock_event_device *bc = tick_broadcast_device.evtdev;
527 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
528 if (bc && cpumask_empty(tick_broadcast_mask))
529 clockevents_shutdown(bc);
534 * Remove a CPU from broadcasting
536 void tick_broadcast_offline(unsigned int cpu)
538 raw_spin_lock(&tick_broadcast_lock);
539 cpumask_clear_cpu(cpu, tick_broadcast_mask);
540 cpumask_clear_cpu(cpu, tick_broadcast_on);
541 tick_broadcast_oneshot_offline(cpu);
542 tick_shutdown_broadcast();
543 raw_spin_unlock(&tick_broadcast_lock);
548 void tick_suspend_broadcast(void)
550 struct clock_event_device *bc;
553 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
555 bc = tick_broadcast_device.evtdev;
557 clockevents_shutdown(bc);
559 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
563 * This is called from tick_resume_local() on a resuming CPU. That's
564 * called from the core resume function, tick_unfreeze() and the magic XEN
567 * In none of these cases the broadcast device mode can change and the
568 * bit of the resuming CPU in the broadcast mask is safe as well.
570 bool tick_resume_check_broadcast(void)
572 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
575 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
578 void tick_resume_broadcast(void)
580 struct clock_event_device *bc;
583 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
585 bc = tick_broadcast_device.evtdev;
588 clockevents_tick_resume(bc);
590 switch (tick_broadcast_device.mode) {
591 case TICKDEV_MODE_PERIODIC:
592 if (!cpumask_empty(tick_broadcast_mask))
593 tick_broadcast_start_periodic(bc);
595 case TICKDEV_MODE_ONESHOT:
596 if (!cpumask_empty(tick_broadcast_mask))
597 tick_resume_broadcast_oneshot(bc);
601 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
604 #ifdef CONFIG_TICK_ONESHOT
606 static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
607 static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
608 static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
611 * Exposed for debugging: see timer_list.c
613 struct cpumask *tick_get_broadcast_oneshot_mask(void)
615 return tick_broadcast_oneshot_mask;
619 * Called before going idle with interrupts disabled. Checks whether a
620 * broadcast event from the other core is about to happen. We detected
621 * that in tick_broadcast_oneshot_control(). The callsite can use this
622 * to avoid a deep idle transition as we are about to get the
623 * broadcast IPI right away.
625 int tick_check_broadcast_expired(void)
627 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
631 * Set broadcast interrupt affinity
633 static void tick_broadcast_set_affinity(struct clock_event_device *bc,
634 const struct cpumask *cpumask)
636 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
639 if (cpumask_equal(bc->cpumask, cpumask))
642 bc->cpumask = cpumask;
643 irq_set_affinity(bc->irq, bc->cpumask);
646 static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
649 if (!clockevent_state_oneshot(bc))
650 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
652 clockevents_program_event(bc, expires, 1);
653 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
656 static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
658 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
662 * Called from irq_enter() when idle was interrupted to reenable the
665 void tick_check_oneshot_broadcast_this_cpu(void)
667 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
668 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
671 * We might be in the middle of switching over from
672 * periodic to oneshot. If the CPU has not yet
673 * switched over, leave the device alone.
675 if (td->mode == TICKDEV_MODE_ONESHOT) {
676 clockevents_switch_state(td->evtdev,
677 CLOCK_EVT_STATE_ONESHOT);
683 * Handle oneshot mode broadcasting
685 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
687 struct tick_device *td;
688 ktime_t now, next_event;
689 int cpu, next_cpu = 0;
692 raw_spin_lock(&tick_broadcast_lock);
693 dev->next_event = KTIME_MAX;
694 next_event = KTIME_MAX;
695 cpumask_clear(tmpmask);
697 /* Find all expired events */
698 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
700 * Required for !SMP because for_each_cpu() reports
701 * unconditionally CPU0 as set on UP kernels.
703 if (!IS_ENABLED(CONFIG_SMP) &&
704 cpumask_empty(tick_broadcast_oneshot_mask))
707 td = &per_cpu(tick_cpu_device, cpu);
708 if (td->evtdev->next_event <= now) {
709 cpumask_set_cpu(cpu, tmpmask);
711 * Mark the remote cpu in the pending mask, so
712 * it can avoid reprogramming the cpu local
713 * timer in tick_broadcast_oneshot_control().
715 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
716 } else if (td->evtdev->next_event < next_event) {
717 next_event = td->evtdev->next_event;
723 * Remove the current cpu from the pending mask. The event is
724 * delivered immediately in tick_do_broadcast() !
726 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
728 /* Take care of enforced broadcast requests */
729 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
730 cpumask_clear(tick_broadcast_force_mask);
733 * Sanity check. Catch the case where we try to broadcast to
736 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
737 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
740 * Wakeup the cpus which have an expired event.
742 bc_local = tick_do_broadcast(tmpmask);
745 * Two reasons for reprogram:
747 * - The global event did not expire any CPU local
748 * events. This happens in dyntick mode, as the maximum PIT
749 * delta is quite small.
751 * - There are pending events on sleeping CPUs which were not
754 if (next_event != KTIME_MAX)
755 tick_broadcast_set_event(dev, next_cpu, next_event);
757 raw_spin_unlock(&tick_broadcast_lock);
760 td = this_cpu_ptr(&tick_cpu_device);
761 td->evtdev->event_handler(td->evtdev);
765 static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
767 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
769 if (bc->next_event == KTIME_MAX)
771 return bc->bound_on == cpu ? -EBUSY : 0;
774 static void broadcast_shutdown_local(struct clock_event_device *bc,
775 struct clock_event_device *dev)
778 * For hrtimer based broadcasting we cannot shutdown the cpu
779 * local device if our own event is the first one to expire or
780 * if we own the broadcast timer.
782 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
783 if (broadcast_needs_cpu(bc, smp_processor_id()))
785 if (dev->next_event < bc->next_event)
788 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
791 static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
792 struct tick_device *td,
795 struct clock_event_device *bc, *dev = td->evtdev;
799 raw_spin_lock(&tick_broadcast_lock);
800 bc = tick_broadcast_device.evtdev;
802 if (state == TICK_BROADCAST_ENTER) {
804 * If the current CPU owns the hrtimer broadcast
805 * mechanism, it cannot go deep idle and we do not add
806 * the CPU to the broadcast mask. We don't have to go
807 * through the EXIT path as the local timer is not
810 ret = broadcast_needs_cpu(bc, cpu);
815 * If the broadcast device is in periodic mode, we
818 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
819 /* If it is a hrtimer based broadcast, return busy */
820 if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
825 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
826 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
828 /* Conditionally shut down the local timer. */
829 broadcast_shutdown_local(bc, dev);
832 * We only reprogram the broadcast timer if we
833 * did not mark ourself in the force mask and
834 * if the cpu local event is earlier than the
835 * broadcast event. If the current CPU is in
836 * the force mask, then we are going to be
837 * woken by the IPI right away; we return
838 * busy, so the CPU does not try to go deep
841 if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
843 } else if (dev->next_event < bc->next_event) {
844 tick_broadcast_set_event(bc, cpu, dev->next_event);
846 * In case of hrtimer broadcasts the
847 * programming might have moved the
848 * timer to this cpu. If yes, remove
849 * us from the broadcast mask and
852 ret = broadcast_needs_cpu(bc, cpu);
854 cpumask_clear_cpu(cpu,
855 tick_broadcast_oneshot_mask);
860 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
861 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
863 * The cpu which was handling the broadcast
864 * timer marked this cpu in the broadcast
865 * pending mask and fired the broadcast
866 * IPI. So we are going to handle the expired
867 * event anyway via the broadcast IPI
868 * handler. No need to reprogram the timer
869 * with an already expired event.
871 if (cpumask_test_and_clear_cpu(cpu,
872 tick_broadcast_pending_mask))
876 * Bail out if there is no next event.
878 if (dev->next_event == KTIME_MAX)
881 * If the pending bit is not set, then we are
882 * either the CPU handling the broadcast
883 * interrupt or we got woken by something else.
885 * We are no longer in the broadcast mask, so
886 * if the cpu local expiry time is already
887 * reached, we would reprogram the cpu local
888 * timer with an already expired event.
890 * This can lead to a ping-pong when we return
891 * to idle and therefore rearm the broadcast
892 * timer before the cpu local timer was able
893 * to fire. This happens because the forced
894 * reprogramming makes sure that the event
895 * will happen in the future and depending on
896 * the min_delta setting this might be far
897 * enough out that the ping-pong starts.
899 * If the cpu local next_event has expired
900 * then we know that the broadcast timer
901 * next_event has expired as well and
902 * broadcast is about to be handled. So we
903 * avoid reprogramming and enforce that the
904 * broadcast handler, which did not run yet,
905 * will invoke the cpu local handler.
907 * We cannot call the handler directly from
908 * here, because we might be in a NOHZ phase
909 * and we did not go through the irq_enter()
913 if (dev->next_event <= now) {
914 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
918 * We got woken by something else. Reprogram
919 * the cpu local timer device.
921 tick_program_event(dev->next_event, 1);
925 raw_spin_unlock(&tick_broadcast_lock);
929 static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
930 struct tick_device *td,
933 struct clock_event_device *dev, *wd;
936 if (td->mode != TICKDEV_MODE_ONESHOT)
939 wd = tick_get_oneshot_wakeup_device(cpu);
944 case TICK_BROADCAST_ENTER:
945 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
946 clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
947 clockevents_program_event(wd, dev->next_event, 1);
949 case TICK_BROADCAST_EXIT:
950 /* We may have transitioned to oneshot mode while idle */
951 if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
958 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
960 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
961 int cpu = smp_processor_id();
963 if (!tick_oneshot_wakeup_control(state, td, cpu))
966 if (tick_broadcast_device.evtdev)
967 return ___tick_broadcast_oneshot_control(state, td, cpu);
970 * If there is no broadcast or wakeup device, tell the caller not
971 * to go into deep idle.
977 * Reset the one shot broadcast for a cpu
979 * Called with tick_broadcast_lock held
981 static void tick_broadcast_clear_oneshot(int cpu)
983 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
984 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
987 static void tick_broadcast_init_next_event(struct cpumask *mask,
990 struct tick_device *td;
993 for_each_cpu(cpu, mask) {
994 td = &per_cpu(tick_cpu_device, cpu);
996 td->evtdev->next_event = expires;
1000 static inline ktime_t tick_get_next_period(void)
1005 * Protect against concurrent updates (store /load tearing on
1006 * 32bit). It does not matter if the time is already in the
1007 * past. The broadcast device which is about to be programmed will
1010 raw_spin_lock(&jiffies_lock);
1011 next = tick_next_period;
1012 raw_spin_unlock(&jiffies_lock);
1017 * tick_broadcast_setup_oneshot - setup the broadcast device
1019 static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
1021 int cpu = smp_processor_id();
1026 /* Set it up only once ! */
1027 if (bc->event_handler != tick_handle_oneshot_broadcast) {
1028 int was_periodic = clockevent_state_periodic(bc);
1030 bc->event_handler = tick_handle_oneshot_broadcast;
1033 * We must be careful here. There might be other CPUs
1034 * waiting for periodic broadcast. We need to set the
1035 * oneshot_mask bits for those and program the
1036 * broadcast device to fire.
1038 cpumask_copy(tmpmask, tick_broadcast_mask);
1039 cpumask_clear_cpu(cpu, tmpmask);
1040 cpumask_or(tick_broadcast_oneshot_mask,
1041 tick_broadcast_oneshot_mask, tmpmask);
1043 if (was_periodic && !cpumask_empty(tmpmask)) {
1044 ktime_t nextevt = tick_get_next_period();
1046 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
1047 tick_broadcast_init_next_event(tmpmask, nextevt);
1048 tick_broadcast_set_event(bc, cpu, nextevt);
1050 bc->next_event = KTIME_MAX;
1053 * The first cpu which switches to oneshot mode sets
1054 * the bit for all other cpus which are in the general
1055 * (periodic) broadcast mask. So the bit is set and
1056 * would prevent the first broadcast enter after this
1057 * to program the bc device.
1059 tick_broadcast_clear_oneshot(cpu);
1064 * Select oneshot operating mode for the broadcast device
1066 void tick_broadcast_switch_to_oneshot(void)
1068 struct clock_event_device *bc;
1069 unsigned long flags;
1071 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1073 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
1074 bc = tick_broadcast_device.evtdev;
1076 tick_broadcast_setup_oneshot(bc);
1078 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1081 #ifdef CONFIG_HOTPLUG_CPU
1082 void hotplug_cpu__broadcast_tick_pull(int deadcpu)
1084 struct clock_event_device *bc;
1085 unsigned long flags;
1087 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1088 bc = tick_broadcast_device.evtdev;
1090 if (bc && broadcast_needs_cpu(bc, deadcpu)) {
1091 /* This moves the broadcast assignment to this CPU: */
1092 clockevents_program_event(bc, bc->next_event, 1);
1094 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1098 * Remove a dying CPU from broadcasting
1100 static void tick_broadcast_oneshot_offline(unsigned int cpu)
1102 if (tick_get_oneshot_wakeup_device(cpu))
1103 tick_set_oneshot_wakeup_device(NULL, cpu);
1106 * Clear the broadcast masks for the dead cpu, but do not stop
1107 * the broadcast device!
1109 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
1110 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
1111 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
1116 * Check, whether the broadcast device is in one shot mode
1118 int tick_broadcast_oneshot_active(void)
1120 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
1124 * Check whether the broadcast device supports oneshot.
1126 bool tick_broadcast_oneshot_available(void)
1128 struct clock_event_device *bc = tick_broadcast_device.evtdev;
1130 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
1134 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
1136 struct clock_event_device *bc = tick_broadcast_device.evtdev;
1138 if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1145 void __init tick_broadcast_init(void)
1147 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1148 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1149 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1150 #ifdef CONFIG_TICK_ONESHOT
1151 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1152 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1153 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);