2 * linux/kernel/time/tick-broadcast.c
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/interrupt.h>
18 #include <linux/percpu.h>
19 #include <linux/profile.h>
20 #include <linux/sched.h>
21 #include <linux/smp.h>
22 #include <linux/module.h>
24 #include "tick-internal.h"
27 * Broadcast support for broken x86 hardware, where the local apic
28 * timer stops in C3 state.
31 static struct tick_device tick_broadcast_device
;
32 static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly
;
33 static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly
;
34 static cpumask_var_t tmpmask __cpumask_var_read_mostly
;
35 static int tick_broadcast_forced
;
37 static __cacheline_aligned_in_smp
DEFINE_RAW_SPINLOCK(tick_broadcast_lock
);
39 #ifdef CONFIG_TICK_ONESHOT
40 static void tick_broadcast_setup_oneshot(struct clock_event_device
*bc
);
41 static void tick_broadcast_clear_oneshot(int cpu
);
42 static void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
);
44 static inline void tick_broadcast_setup_oneshot(struct clock_event_device
*bc
) { BUG(); }
45 static inline void tick_broadcast_clear_oneshot(int cpu
) { }
46 static inline void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
) { }
50 * Debugging: see timer_list.c
52 struct tick_device
*tick_get_broadcast_device(void)
54 return &tick_broadcast_device
;
57 struct cpumask
*tick_get_broadcast_mask(void)
59 return tick_broadcast_mask
;
63 * Start the device in periodic mode
65 static void tick_broadcast_start_periodic(struct clock_event_device
*bc
)
68 tick_setup_periodic(bc
, 1);
72 * Check, if the device can be utilized as broadcast device:
74 static bool tick_check_broadcast_device(struct clock_event_device
*curdev
,
75 struct clock_event_device
*newdev
)
77 if ((newdev
->features
& CLOCK_EVT_FEAT_DUMMY
) ||
78 (newdev
->features
& CLOCK_EVT_FEAT_PERCPU
) ||
79 (newdev
->features
& CLOCK_EVT_FEAT_C3STOP
))
82 if (tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
&&
83 !(newdev
->features
& CLOCK_EVT_FEAT_ONESHOT
))
86 return !curdev
|| newdev
->rating
> curdev
->rating
;
90 * Conditionally install/replace broadcast device
92 void tick_install_broadcast_device(struct clock_event_device
*dev
)
94 struct clock_event_device
*cur
= tick_broadcast_device
.evtdev
;
96 if (!tick_check_broadcast_device(cur
, dev
))
99 if (!try_module_get(dev
->owner
))
102 clockevents_exchange_device(cur
, dev
);
104 cur
->event_handler
= clockevents_handle_noop
;
105 tick_broadcast_device
.evtdev
= dev
;
106 if (!cpumask_empty(tick_broadcast_mask
))
107 tick_broadcast_start_periodic(dev
);
109 * Inform all cpus about this. We might be in a situation
110 * where we did not switch to oneshot mode because the per cpu
111 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
112 * of a oneshot capable broadcast device. Without that
113 * notification the systems stays stuck in periodic mode
116 if (dev
->features
& CLOCK_EVT_FEAT_ONESHOT
)
121 * Check, if the device is the broadcast device
123 int tick_is_broadcast_device(struct clock_event_device
*dev
)
125 return (dev
&& tick_broadcast_device
.evtdev
== dev
);
128 int tick_broadcast_update_freq(struct clock_event_device
*dev
, u32 freq
)
132 if (tick_is_broadcast_device(dev
)) {
133 raw_spin_lock(&tick_broadcast_lock
);
134 ret
= __clockevents_update_freq(dev
, freq
);
135 raw_spin_unlock(&tick_broadcast_lock
);
141 static void err_broadcast(const struct cpumask
*mask
)
143 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
146 static void tick_device_setup_broadcast_func(struct clock_event_device
*dev
)
149 dev
->broadcast
= tick_broadcast
;
150 if (!dev
->broadcast
) {
151 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
153 dev
->broadcast
= err_broadcast
;
158 * Check, if the device is disfunctional and a place holder, which
159 * needs to be handled by the broadcast device.
161 int tick_device_uses_broadcast(struct clock_event_device
*dev
, int cpu
)
163 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
167 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
170 * Devices might be registered with both periodic and oneshot
171 * mode disabled. This signals, that the device needs to be
172 * operated from the broadcast device and is a placeholder for
173 * the cpu local device.
175 if (!tick_device_is_functional(dev
)) {
176 dev
->event_handler
= tick_handle_periodic
;
177 tick_device_setup_broadcast_func(dev
);
178 cpumask_set_cpu(cpu
, tick_broadcast_mask
);
179 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
180 tick_broadcast_start_periodic(bc
);
182 tick_broadcast_setup_oneshot(bc
);
186 * Clear the broadcast bit for this cpu if the
187 * device is not power state affected.
189 if (!(dev
->features
& CLOCK_EVT_FEAT_C3STOP
))
190 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
192 tick_device_setup_broadcast_func(dev
);
195 * Clear the broadcast bit if the CPU is not in
196 * periodic broadcast on state.
198 if (!cpumask_test_cpu(cpu
, tick_broadcast_on
))
199 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
201 switch (tick_broadcast_device
.mode
) {
202 case TICKDEV_MODE_ONESHOT
:
204 * If the system is in oneshot mode we can
205 * unconditionally clear the oneshot mask bit,
206 * because the CPU is running and therefore
207 * not in an idle state which causes the power
208 * state affected device to stop. Let the
209 * caller initialize the device.
211 tick_broadcast_clear_oneshot(cpu
);
215 case TICKDEV_MODE_PERIODIC
:
217 * If the system is in periodic mode, check
218 * whether the broadcast device can be
221 if (cpumask_empty(tick_broadcast_mask
) && bc
)
222 clockevents_shutdown(bc
);
224 * If we kept the cpu in the broadcast mask,
225 * tell the caller to leave the per cpu device
226 * in shutdown state. The periodic interrupt
227 * is delivered by the broadcast device, if
228 * the broadcast device exists and is not
231 if (bc
&& !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
232 ret
= cpumask_test_cpu(cpu
, tick_broadcast_mask
);
238 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
242 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
243 int tick_receive_broadcast(void)
245 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
246 struct clock_event_device
*evt
= td
->evtdev
;
251 if (!evt
->event_handler
)
254 evt
->event_handler(evt
);
260 * Broadcast the event to the cpus, which are set in the mask (mangled).
262 static bool tick_do_broadcast(struct cpumask
*mask
)
264 int cpu
= smp_processor_id();
265 struct tick_device
*td
;
269 * Check, if the current cpu is in the mask
271 if (cpumask_test_cpu(cpu
, mask
)) {
272 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
274 cpumask_clear_cpu(cpu
, mask
);
276 * We only run the local handler, if the broadcast
277 * device is not hrtimer based. Otherwise we run into
278 * a hrtimer recursion.
280 * local timer_interrupt()
287 local
= !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
);
290 if (!cpumask_empty(mask
)) {
292 * It might be necessary to actually check whether the devices
293 * have different broadcast functions. For now, just use the
294 * one of the first device. This works as long as we have this
295 * misfeature only on x86 (lapic)
297 td
= &per_cpu(tick_cpu_device
, cpumask_first(mask
));
298 td
->evtdev
->broadcast(mask
);
304 * Periodic broadcast:
305 * - invoke the broadcast handlers
307 static bool tick_do_periodic_broadcast(void)
309 cpumask_and(tmpmask
, cpu_online_mask
, tick_broadcast_mask
);
310 return tick_do_broadcast(tmpmask
);
314 * Event handler for periodic broadcast ticks
316 static void tick_handle_periodic_broadcast(struct clock_event_device
*dev
)
318 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
321 raw_spin_lock(&tick_broadcast_lock
);
323 /* Handle spurious interrupts gracefully */
324 if (clockevent_state_shutdown(tick_broadcast_device
.evtdev
)) {
325 raw_spin_unlock(&tick_broadcast_lock
);
329 bc_local
= tick_do_periodic_broadcast();
331 if (clockevent_state_oneshot(dev
)) {
332 ktime_t next
= ktime_add(dev
->next_event
, tick_period
);
334 clockevents_program_event(dev
, next
, true);
336 raw_spin_unlock(&tick_broadcast_lock
);
339 * We run the handler of the local cpu after dropping
340 * tick_broadcast_lock because the handler might deadlock when
341 * trying to switch to oneshot mode.
344 td
->evtdev
->event_handler(td
->evtdev
);
348 * tick_broadcast_control - Enable/disable or force broadcast mode
349 * @mode: The selected broadcast mode
351 * Called when the system enters a state where affected tick devices
352 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
354 void tick_broadcast_control(enum tick_broadcast_mode mode
)
356 struct clock_event_device
*bc
, *dev
;
357 struct tick_device
*td
;
361 /* Protects also the local clockevent device. */
362 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
363 td
= this_cpu_ptr(&tick_cpu_device
);
367 * Is the device not affected by the powerstate ?
369 if (!dev
|| !(dev
->features
& CLOCK_EVT_FEAT_C3STOP
))
372 if (!tick_device_is_functional(dev
))
375 cpu
= smp_processor_id();
376 bc
= tick_broadcast_device
.evtdev
;
377 bc_stopped
= cpumask_empty(tick_broadcast_mask
);
380 case TICK_BROADCAST_FORCE
:
381 tick_broadcast_forced
= 1;
382 case TICK_BROADCAST_ON
:
383 cpumask_set_cpu(cpu
, tick_broadcast_on
);
384 if (!cpumask_test_and_set_cpu(cpu
, tick_broadcast_mask
)) {
386 * Only shutdown the cpu local device, if:
388 * - the broadcast device exists
389 * - the broadcast device is not a hrtimer based one
390 * - the broadcast device is in periodic mode to
391 * avoid a hickup during switch to oneshot mode
393 if (bc
&& !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
) &&
394 tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
395 clockevents_shutdown(dev
);
399 case TICK_BROADCAST_OFF
:
400 if (tick_broadcast_forced
)
402 cpumask_clear_cpu(cpu
, tick_broadcast_on
);
403 if (!tick_device_is_functional(dev
))
405 if (cpumask_test_and_clear_cpu(cpu
, tick_broadcast_mask
)) {
406 if (tick_broadcast_device
.mode
==
407 TICKDEV_MODE_PERIODIC
)
408 tick_setup_periodic(dev
, 0);
414 if (cpumask_empty(tick_broadcast_mask
)) {
416 clockevents_shutdown(bc
);
417 } else if (bc_stopped
) {
418 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
419 tick_broadcast_start_periodic(bc
);
421 tick_broadcast_setup_oneshot(bc
);
425 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
427 EXPORT_SYMBOL_GPL(tick_broadcast_control
);
430 * Set the periodic handler depending on broadcast on/off
432 void tick_set_periodic_handler(struct clock_event_device
*dev
, int broadcast
)
435 dev
->event_handler
= tick_handle_periodic
;
437 dev
->event_handler
= tick_handle_periodic_broadcast
;
440 #ifdef CONFIG_HOTPLUG_CPU
442 * Remove a CPU from broadcasting
444 void tick_shutdown_broadcast(unsigned int cpu
)
446 struct clock_event_device
*bc
;
449 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
451 bc
= tick_broadcast_device
.evtdev
;
452 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
453 cpumask_clear_cpu(cpu
, tick_broadcast_on
);
455 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
) {
456 if (bc
&& cpumask_empty(tick_broadcast_mask
))
457 clockevents_shutdown(bc
);
460 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
464 void tick_suspend_broadcast(void)
466 struct clock_event_device
*bc
;
469 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
471 bc
= tick_broadcast_device
.evtdev
;
473 clockevents_shutdown(bc
);
475 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
479 * This is called from tick_resume_local() on a resuming CPU. That's
480 * called from the core resume function, tick_unfreeze() and the magic XEN
483 * In none of these cases the broadcast device mode can change and the
484 * bit of the resuming CPU in the broadcast mask is safe as well.
486 bool tick_resume_check_broadcast(void)
488 if (tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
)
491 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask
);
494 void tick_resume_broadcast(void)
496 struct clock_event_device
*bc
;
499 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
501 bc
= tick_broadcast_device
.evtdev
;
504 clockevents_tick_resume(bc
);
506 switch (tick_broadcast_device
.mode
) {
507 case TICKDEV_MODE_PERIODIC
:
508 if (!cpumask_empty(tick_broadcast_mask
))
509 tick_broadcast_start_periodic(bc
);
511 case TICKDEV_MODE_ONESHOT
:
512 if (!cpumask_empty(tick_broadcast_mask
))
513 tick_resume_broadcast_oneshot(bc
);
517 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
520 #ifdef CONFIG_TICK_ONESHOT
522 static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly
;
523 static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly
;
524 static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly
;
527 * Exposed for debugging: see timer_list.c
529 struct cpumask
*tick_get_broadcast_oneshot_mask(void)
531 return tick_broadcast_oneshot_mask
;
535 * Called before going idle with interrupts disabled. Checks whether a
536 * broadcast event from the other core is about to happen. We detected
537 * that in tick_broadcast_oneshot_control(). The callsite can use this
538 * to avoid a deep idle transition as we are about to get the
539 * broadcast IPI right away.
541 int tick_check_broadcast_expired(void)
543 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask
);
547 * Set broadcast interrupt affinity
549 static void tick_broadcast_set_affinity(struct clock_event_device
*bc
,
550 const struct cpumask
*cpumask
)
552 if (!(bc
->features
& CLOCK_EVT_FEAT_DYNIRQ
))
555 if (cpumask_equal(bc
->cpumask
, cpumask
))
558 bc
->cpumask
= cpumask
;
559 irq_set_affinity(bc
->irq
, bc
->cpumask
);
562 static void tick_broadcast_set_event(struct clock_event_device
*bc
, int cpu
,
565 if (!clockevent_state_oneshot(bc
))
566 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
568 clockevents_program_event(bc
, expires
, 1);
569 tick_broadcast_set_affinity(bc
, cpumask_of(cpu
));
572 static void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
)
574 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
578 * Called from irq_enter() when idle was interrupted to reenable the
581 void tick_check_oneshot_broadcast_this_cpu(void)
583 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask
)) {
584 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
587 * We might be in the middle of switching over from
588 * periodic to oneshot. If the CPU has not yet
589 * switched over, leave the device alone.
591 if (td
->mode
== TICKDEV_MODE_ONESHOT
) {
592 clockevents_switch_state(td
->evtdev
,
593 CLOCK_EVT_STATE_ONESHOT
);
599 * Handle oneshot mode broadcasting
601 static void tick_handle_oneshot_broadcast(struct clock_event_device
*dev
)
603 struct tick_device
*td
;
604 ktime_t now
, next_event
;
605 int cpu
, next_cpu
= 0;
608 raw_spin_lock(&tick_broadcast_lock
);
609 dev
->next_event
= KTIME_MAX
;
610 next_event
= KTIME_MAX
;
611 cpumask_clear(tmpmask
);
613 /* Find all expired events */
614 for_each_cpu(cpu
, tick_broadcast_oneshot_mask
) {
616 * Required for !SMP because for_each_cpu() reports
617 * unconditionally CPU0 as set on UP kernels.
619 if (!IS_ENABLED(CONFIG_SMP
) &&
620 cpumask_empty(tick_broadcast_oneshot_mask
))
623 td
= &per_cpu(tick_cpu_device
, cpu
);
624 if (td
->evtdev
->next_event
<= now
) {
625 cpumask_set_cpu(cpu
, tmpmask
);
627 * Mark the remote cpu in the pending mask, so
628 * it can avoid reprogramming the cpu local
629 * timer in tick_broadcast_oneshot_control().
631 cpumask_set_cpu(cpu
, tick_broadcast_pending_mask
);
632 } else if (td
->evtdev
->next_event
< next_event
) {
633 next_event
= td
->evtdev
->next_event
;
639 * Remove the current cpu from the pending mask. The event is
640 * delivered immediately in tick_do_broadcast() !
642 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask
);
644 /* Take care of enforced broadcast requests */
645 cpumask_or(tmpmask
, tmpmask
, tick_broadcast_force_mask
);
646 cpumask_clear(tick_broadcast_force_mask
);
649 * Sanity check. Catch the case where we try to broadcast to
652 if (WARN_ON_ONCE(!cpumask_subset(tmpmask
, cpu_online_mask
)))
653 cpumask_and(tmpmask
, tmpmask
, cpu_online_mask
);
656 * Wakeup the cpus which have an expired event.
658 bc_local
= tick_do_broadcast(tmpmask
);
661 * Two reasons for reprogram:
663 * - The global event did not expire any CPU local
664 * events. This happens in dyntick mode, as the maximum PIT
665 * delta is quite small.
667 * - There are pending events on sleeping CPUs which were not
670 if (next_event
!= KTIME_MAX
)
671 tick_broadcast_set_event(dev
, next_cpu
, next_event
);
673 raw_spin_unlock(&tick_broadcast_lock
);
676 td
= this_cpu_ptr(&tick_cpu_device
);
677 td
->evtdev
->event_handler(td
->evtdev
);
681 static int broadcast_needs_cpu(struct clock_event_device
*bc
, int cpu
)
683 if (!(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
685 if (bc
->next_event
== KTIME_MAX
)
687 return bc
->bound_on
== cpu
? -EBUSY
: 0;
690 static void broadcast_shutdown_local(struct clock_event_device
*bc
,
691 struct clock_event_device
*dev
)
694 * For hrtimer based broadcasting we cannot shutdown the cpu
695 * local device if our own event is the first one to expire or
696 * if we own the broadcast timer.
698 if (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
) {
699 if (broadcast_needs_cpu(bc
, smp_processor_id()))
701 if (dev
->next_event
< bc
->next_event
)
704 clockevents_switch_state(dev
, CLOCK_EVT_STATE_SHUTDOWN
);
707 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state
)
709 struct clock_event_device
*bc
, *dev
;
714 * If there is no broadcast device, tell the caller not to go
717 if (!tick_broadcast_device
.evtdev
)
720 dev
= this_cpu_ptr(&tick_cpu_device
)->evtdev
;
722 raw_spin_lock(&tick_broadcast_lock
);
723 bc
= tick_broadcast_device
.evtdev
;
724 cpu
= smp_processor_id();
726 if (state
== TICK_BROADCAST_ENTER
) {
728 * If the current CPU owns the hrtimer broadcast
729 * mechanism, it cannot go deep idle and we do not add
730 * the CPU to the broadcast mask. We don't have to go
731 * through the EXIT path as the local timer is not
734 ret
= broadcast_needs_cpu(bc
, cpu
);
739 * If the broadcast device is in periodic mode, we
742 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
) {
743 /* If it is a hrtimer based broadcast, return busy */
744 if (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
)
749 if (!cpumask_test_and_set_cpu(cpu
, tick_broadcast_oneshot_mask
)) {
750 WARN_ON_ONCE(cpumask_test_cpu(cpu
, tick_broadcast_pending_mask
));
752 /* Conditionally shut down the local timer. */
753 broadcast_shutdown_local(bc
, dev
);
756 * We only reprogram the broadcast timer if we
757 * did not mark ourself in the force mask and
758 * if the cpu local event is earlier than the
759 * broadcast event. If the current CPU is in
760 * the force mask, then we are going to be
761 * woken by the IPI right away; we return
762 * busy, so the CPU does not try to go deep
765 if (cpumask_test_cpu(cpu
, tick_broadcast_force_mask
)) {
767 } else if (dev
->next_event
< bc
->next_event
) {
768 tick_broadcast_set_event(bc
, cpu
, dev
->next_event
);
770 * In case of hrtimer broadcasts the
771 * programming might have moved the
772 * timer to this cpu. If yes, remove
773 * us from the broadcast mask and
776 ret
= broadcast_needs_cpu(bc
, cpu
);
778 cpumask_clear_cpu(cpu
,
779 tick_broadcast_oneshot_mask
);
784 if (cpumask_test_and_clear_cpu(cpu
, tick_broadcast_oneshot_mask
)) {
785 clockevents_switch_state(dev
, CLOCK_EVT_STATE_ONESHOT
);
787 * The cpu which was handling the broadcast
788 * timer marked this cpu in the broadcast
789 * pending mask and fired the broadcast
790 * IPI. So we are going to handle the expired
791 * event anyway via the broadcast IPI
792 * handler. No need to reprogram the timer
793 * with an already expired event.
795 if (cpumask_test_and_clear_cpu(cpu
,
796 tick_broadcast_pending_mask
))
800 * Bail out if there is no next event.
802 if (dev
->next_event
== KTIME_MAX
)
805 * If the pending bit is not set, then we are
806 * either the CPU handling the broadcast
807 * interrupt or we got woken by something else.
809 * We are not longer in the broadcast mask, so
810 * if the cpu local expiry time is already
811 * reached, we would reprogram the cpu local
812 * timer with an already expired event.
814 * This can lead to a ping-pong when we return
815 * to idle and therefor rearm the broadcast
816 * timer before the cpu local timer was able
817 * to fire. This happens because the forced
818 * reprogramming makes sure that the event
819 * will happen in the future and depending on
820 * the min_delta setting this might be far
821 * enough out that the ping-pong starts.
823 * If the cpu local next_event has expired
824 * then we know that the broadcast timer
825 * next_event has expired as well and
826 * broadcast is about to be handled. So we
827 * avoid reprogramming and enforce that the
828 * broadcast handler, which did not run yet,
829 * will invoke the cpu local handler.
831 * We cannot call the handler directly from
832 * here, because we might be in a NOHZ phase
833 * and we did not go through the irq_enter()
837 if (dev
->next_event
<= now
) {
838 cpumask_set_cpu(cpu
, tick_broadcast_force_mask
);
842 * We got woken by something else. Reprogram
843 * the cpu local timer device.
845 tick_program_event(dev
->next_event
, 1);
849 raw_spin_unlock(&tick_broadcast_lock
);
854 * Reset the one shot broadcast for a cpu
856 * Called with tick_broadcast_lock held
858 static void tick_broadcast_clear_oneshot(int cpu
)
860 cpumask_clear_cpu(cpu
, tick_broadcast_oneshot_mask
);
861 cpumask_clear_cpu(cpu
, tick_broadcast_pending_mask
);
864 static void tick_broadcast_init_next_event(struct cpumask
*mask
,
867 struct tick_device
*td
;
870 for_each_cpu(cpu
, mask
) {
871 td
= &per_cpu(tick_cpu_device
, cpu
);
873 td
->evtdev
->next_event
= expires
;
878 * tick_broadcast_setup_oneshot - setup the broadcast device
880 static void tick_broadcast_setup_oneshot(struct clock_event_device
*bc
)
882 int cpu
= smp_processor_id();
887 /* Set it up only once ! */
888 if (bc
->event_handler
!= tick_handle_oneshot_broadcast
) {
889 int was_periodic
= clockevent_state_periodic(bc
);
891 bc
->event_handler
= tick_handle_oneshot_broadcast
;
894 * We must be careful here. There might be other CPUs
895 * waiting for periodic broadcast. We need to set the
896 * oneshot_mask bits for those and program the
897 * broadcast device to fire.
899 cpumask_copy(tmpmask
, tick_broadcast_mask
);
900 cpumask_clear_cpu(cpu
, tmpmask
);
901 cpumask_or(tick_broadcast_oneshot_mask
,
902 tick_broadcast_oneshot_mask
, tmpmask
);
904 if (was_periodic
&& !cpumask_empty(tmpmask
)) {
905 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
906 tick_broadcast_init_next_event(tmpmask
,
908 tick_broadcast_set_event(bc
, cpu
, tick_next_period
);
910 bc
->next_event
= KTIME_MAX
;
913 * The first cpu which switches to oneshot mode sets
914 * the bit for all other cpus which are in the general
915 * (periodic) broadcast mask. So the bit is set and
916 * would prevent the first broadcast enter after this
917 * to program the bc device.
919 tick_broadcast_clear_oneshot(cpu
);
924 * Select oneshot operating mode for the broadcast device
926 void tick_broadcast_switch_to_oneshot(void)
928 struct clock_event_device
*bc
;
931 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
933 tick_broadcast_device
.mode
= TICKDEV_MODE_ONESHOT
;
934 bc
= tick_broadcast_device
.evtdev
;
936 tick_broadcast_setup_oneshot(bc
);
938 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
941 #ifdef CONFIG_HOTPLUG_CPU
942 void hotplug_cpu__broadcast_tick_pull(int deadcpu
)
944 struct clock_event_device
*bc
;
947 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
948 bc
= tick_broadcast_device
.evtdev
;
950 if (bc
&& broadcast_needs_cpu(bc
, deadcpu
)) {
951 /* This moves the broadcast assignment to this CPU: */
952 clockevents_program_event(bc
, bc
->next_event
, 1);
954 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
958 * Remove a dead CPU from broadcasting
960 void tick_shutdown_broadcast_oneshot(unsigned int cpu
)
964 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
967 * Clear the broadcast masks for the dead cpu, but do not stop
968 * the broadcast device!
970 cpumask_clear_cpu(cpu
, tick_broadcast_oneshot_mask
);
971 cpumask_clear_cpu(cpu
, tick_broadcast_pending_mask
);
972 cpumask_clear_cpu(cpu
, tick_broadcast_force_mask
);
974 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
979 * Check, whether the broadcast device is in one shot mode
981 int tick_broadcast_oneshot_active(void)
983 return tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
;
987 * Check whether the broadcast device supports oneshot.
989 bool tick_broadcast_oneshot_available(void)
991 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
993 return bc
? bc
->features
& CLOCK_EVT_FEAT_ONESHOT
: false;
997 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state
)
999 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
1001 if (!bc
|| (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
1008 void __init
tick_broadcast_init(void)
1010 zalloc_cpumask_var(&tick_broadcast_mask
, GFP_NOWAIT
);
1011 zalloc_cpumask_var(&tick_broadcast_on
, GFP_NOWAIT
);
1012 zalloc_cpumask_var(&tmpmask
, GFP_NOWAIT
);
1013 #ifdef CONFIG_TICK_ONESHOT
1014 zalloc_cpumask_var(&tick_broadcast_oneshot_mask
, GFP_NOWAIT
);
1015 zalloc_cpumask_var(&tick_broadcast_pending_mask
, GFP_NOWAIT
);
1016 zalloc_cpumask_var(&tick_broadcast_force_mask
, GFP_NOWAIT
);