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
;
33 static cpumask_var_t tick_broadcast_on
;
34 static cpumask_var_t tmpmask
;
35 static DEFINE_RAW_SPINLOCK(tick_broadcast_lock
);
36 static int tick_broadcast_forced
;
38 #ifdef CONFIG_TICK_ONESHOT
39 static void tick_broadcast_clear_oneshot(int cpu
);
40 static void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
);
42 static inline void tick_broadcast_clear_oneshot(int cpu
) { }
43 static inline void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
) { }
47 * Debugging: see timer_list.c
49 struct tick_device
*tick_get_broadcast_device(void)
51 return &tick_broadcast_device
;
54 struct cpumask
*tick_get_broadcast_mask(void)
56 return tick_broadcast_mask
;
60 * Start the device in periodic mode
62 static void tick_broadcast_start_periodic(struct clock_event_device
*bc
)
65 tick_setup_periodic(bc
, 1);
69 * Check, if the device can be utilized as broadcast device:
71 static bool tick_check_broadcast_device(struct clock_event_device
*curdev
,
72 struct clock_event_device
*newdev
)
74 if ((newdev
->features
& CLOCK_EVT_FEAT_DUMMY
) ||
75 (newdev
->features
& CLOCK_EVT_FEAT_PERCPU
) ||
76 (newdev
->features
& CLOCK_EVT_FEAT_C3STOP
))
79 if (tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
&&
80 !(newdev
->features
& CLOCK_EVT_FEAT_ONESHOT
))
83 return !curdev
|| newdev
->rating
> curdev
->rating
;
87 * Conditionally install/replace broadcast device
89 void tick_install_broadcast_device(struct clock_event_device
*dev
)
91 struct clock_event_device
*cur
= tick_broadcast_device
.evtdev
;
93 if (!tick_check_broadcast_device(cur
, dev
))
96 if (!try_module_get(dev
->owner
))
99 clockevents_exchange_device(cur
, dev
);
101 cur
->event_handler
= clockevents_handle_noop
;
102 tick_broadcast_device
.evtdev
= dev
;
103 if (!cpumask_empty(tick_broadcast_mask
))
104 tick_broadcast_start_periodic(dev
);
106 * Inform all cpus about this. We might be in a situation
107 * where we did not switch to oneshot mode because the per cpu
108 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
109 * of a oneshot capable broadcast device. Without that
110 * notification the systems stays stuck in periodic mode
113 if (dev
->features
& CLOCK_EVT_FEAT_ONESHOT
)
118 * Check, if the device is the broadcast device
120 int tick_is_broadcast_device(struct clock_event_device
*dev
)
122 return (dev
&& tick_broadcast_device
.evtdev
== dev
);
125 int tick_broadcast_update_freq(struct clock_event_device
*dev
, u32 freq
)
129 if (tick_is_broadcast_device(dev
)) {
130 raw_spin_lock(&tick_broadcast_lock
);
131 ret
= __clockevents_update_freq(dev
, freq
);
132 raw_spin_unlock(&tick_broadcast_lock
);
138 static void err_broadcast(const struct cpumask
*mask
)
140 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
143 static void tick_device_setup_broadcast_func(struct clock_event_device
*dev
)
146 dev
->broadcast
= tick_broadcast
;
147 if (!dev
->broadcast
) {
148 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
150 dev
->broadcast
= err_broadcast
;
155 * Check, if the device is disfunctional and a place holder, which
156 * needs to be handled by the broadcast device.
158 int tick_device_uses_broadcast(struct clock_event_device
*dev
, int cpu
)
160 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
164 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
167 * Devices might be registered with both periodic and oneshot
168 * mode disabled. This signals, that the device needs to be
169 * operated from the broadcast device and is a placeholder for
170 * the cpu local device.
172 if (!tick_device_is_functional(dev
)) {
173 dev
->event_handler
= tick_handle_periodic
;
174 tick_device_setup_broadcast_func(dev
);
175 cpumask_set_cpu(cpu
, tick_broadcast_mask
);
176 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
177 tick_broadcast_start_periodic(bc
);
179 tick_broadcast_setup_oneshot(bc
);
183 * Clear the broadcast bit for this cpu if the
184 * device is not power state affected.
186 if (!(dev
->features
& CLOCK_EVT_FEAT_C3STOP
))
187 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
189 tick_device_setup_broadcast_func(dev
);
192 * Clear the broadcast bit if the CPU is not in
193 * periodic broadcast on state.
195 if (!cpumask_test_cpu(cpu
, tick_broadcast_on
))
196 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
198 switch (tick_broadcast_device
.mode
) {
199 case TICKDEV_MODE_ONESHOT
:
201 * If the system is in oneshot mode we can
202 * unconditionally clear the oneshot mask bit,
203 * because the CPU is running and therefore
204 * not in an idle state which causes the power
205 * state affected device to stop. Let the
206 * caller initialize the device.
208 tick_broadcast_clear_oneshot(cpu
);
212 case TICKDEV_MODE_PERIODIC
:
214 * If the system is in periodic mode, check
215 * whether the broadcast device can be
218 if (cpumask_empty(tick_broadcast_mask
) && bc
)
219 clockevents_shutdown(bc
);
221 * If we kept the cpu in the broadcast mask,
222 * tell the caller to leave the per cpu device
223 * in shutdown state. The periodic interrupt
224 * is delivered by the broadcast device, if
225 * the broadcast device exists and is not
228 if (bc
&& !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
229 ret
= cpumask_test_cpu(cpu
, tick_broadcast_mask
);
235 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
239 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
240 int tick_receive_broadcast(void)
242 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
243 struct clock_event_device
*evt
= td
->evtdev
;
248 if (!evt
->event_handler
)
251 evt
->event_handler(evt
);
257 * Broadcast the event to the cpus, which are set in the mask (mangled).
259 static bool tick_do_broadcast(struct cpumask
*mask
)
261 int cpu
= smp_processor_id();
262 struct tick_device
*td
;
266 * Check, if the current cpu is in the mask
268 if (cpumask_test_cpu(cpu
, mask
)) {
269 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
271 cpumask_clear_cpu(cpu
, mask
);
273 * We only run the local handler, if the broadcast
274 * device is not hrtimer based. Otherwise we run into
275 * a hrtimer recursion.
277 * local timer_interrupt()
284 local
= !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
);
287 if (!cpumask_empty(mask
)) {
289 * It might be necessary to actually check whether the devices
290 * have different broadcast functions. For now, just use the
291 * one of the first device. This works as long as we have this
292 * misfeature only on x86 (lapic)
294 td
= &per_cpu(tick_cpu_device
, cpumask_first(mask
));
295 td
->evtdev
->broadcast(mask
);
301 * Periodic broadcast:
302 * - invoke the broadcast handlers
304 static bool tick_do_periodic_broadcast(void)
306 cpumask_and(tmpmask
, cpu_online_mask
, tick_broadcast_mask
);
307 return tick_do_broadcast(tmpmask
);
311 * Event handler for periodic broadcast ticks
313 static void tick_handle_periodic_broadcast(struct clock_event_device
*dev
)
315 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
318 raw_spin_lock(&tick_broadcast_lock
);
320 /* Handle spurious interrupts gracefully */
321 if (clockevent_state_shutdown(tick_broadcast_device
.evtdev
)) {
322 raw_spin_unlock(&tick_broadcast_lock
);
326 bc_local
= tick_do_periodic_broadcast();
328 if (clockevent_state_oneshot(dev
)) {
329 ktime_t next
= ktime_add(dev
->next_event
, tick_period
);
331 clockevents_program_event(dev
, next
, true);
333 raw_spin_unlock(&tick_broadcast_lock
);
336 * We run the handler of the local cpu after dropping
337 * tick_broadcast_lock because the handler might deadlock when
338 * trying to switch to oneshot mode.
341 td
->evtdev
->event_handler(td
->evtdev
);
345 * tick_broadcast_control - Enable/disable or force broadcast mode
346 * @mode: The selected broadcast mode
348 * Called when the system enters a state where affected tick devices
349 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
351 void tick_broadcast_control(enum tick_broadcast_mode mode
)
353 struct clock_event_device
*bc
, *dev
;
354 struct tick_device
*td
;
358 /* Protects also the local clockevent device. */
359 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
360 td
= this_cpu_ptr(&tick_cpu_device
);
364 * Is the device not affected by the powerstate ?
366 if (!dev
|| !(dev
->features
& CLOCK_EVT_FEAT_C3STOP
))
369 if (!tick_device_is_functional(dev
))
372 cpu
= smp_processor_id();
373 bc
= tick_broadcast_device
.evtdev
;
374 bc_stopped
= cpumask_empty(tick_broadcast_mask
);
377 case TICK_BROADCAST_FORCE
:
378 tick_broadcast_forced
= 1;
379 case TICK_BROADCAST_ON
:
380 cpumask_set_cpu(cpu
, tick_broadcast_on
);
381 if (!cpumask_test_and_set_cpu(cpu
, tick_broadcast_mask
)) {
383 * Only shutdown the cpu local device, if:
385 * - the broadcast device exists
386 * - the broadcast device is not a hrtimer based one
387 * - the broadcast device is in periodic mode to
388 * avoid a hickup during switch to oneshot mode
390 if (bc
&& !(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
) &&
391 tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
392 clockevents_shutdown(dev
);
396 case TICK_BROADCAST_OFF
:
397 if (tick_broadcast_forced
)
399 cpumask_clear_cpu(cpu
, tick_broadcast_on
);
400 if (!tick_device_is_functional(dev
))
402 if (cpumask_test_and_clear_cpu(cpu
, tick_broadcast_mask
)) {
403 if (tick_broadcast_device
.mode
==
404 TICKDEV_MODE_PERIODIC
)
405 tick_setup_periodic(dev
, 0);
411 if (cpumask_empty(tick_broadcast_mask
)) {
413 clockevents_shutdown(bc
);
414 } else if (bc_stopped
) {
415 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
)
416 tick_broadcast_start_periodic(bc
);
418 tick_broadcast_setup_oneshot(bc
);
422 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
424 EXPORT_SYMBOL_GPL(tick_broadcast_control
);
427 * Set the periodic handler depending on broadcast on/off
429 void tick_set_periodic_handler(struct clock_event_device
*dev
, int broadcast
)
432 dev
->event_handler
= tick_handle_periodic
;
434 dev
->event_handler
= tick_handle_periodic_broadcast
;
437 #ifdef CONFIG_HOTPLUG_CPU
439 * Remove a CPU from broadcasting
441 void tick_shutdown_broadcast(unsigned int cpu
)
443 struct clock_event_device
*bc
;
446 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
448 bc
= tick_broadcast_device
.evtdev
;
449 cpumask_clear_cpu(cpu
, tick_broadcast_mask
);
450 cpumask_clear_cpu(cpu
, tick_broadcast_on
);
452 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
) {
453 if (bc
&& cpumask_empty(tick_broadcast_mask
))
454 clockevents_shutdown(bc
);
457 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
461 void tick_suspend_broadcast(void)
463 struct clock_event_device
*bc
;
466 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
468 bc
= tick_broadcast_device
.evtdev
;
470 clockevents_shutdown(bc
);
472 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
476 * This is called from tick_resume_local() on a resuming CPU. That's
477 * called from the core resume function, tick_unfreeze() and the magic XEN
480 * In none of these cases the broadcast device mode can change and the
481 * bit of the resuming CPU in the broadcast mask is safe as well.
483 bool tick_resume_check_broadcast(void)
485 if (tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
)
488 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask
);
491 void tick_resume_broadcast(void)
493 struct clock_event_device
*bc
;
496 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
498 bc
= tick_broadcast_device
.evtdev
;
501 clockevents_tick_resume(bc
);
503 switch (tick_broadcast_device
.mode
) {
504 case TICKDEV_MODE_PERIODIC
:
505 if (!cpumask_empty(tick_broadcast_mask
))
506 tick_broadcast_start_periodic(bc
);
508 case TICKDEV_MODE_ONESHOT
:
509 if (!cpumask_empty(tick_broadcast_mask
))
510 tick_resume_broadcast_oneshot(bc
);
514 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
517 #ifdef CONFIG_TICK_ONESHOT
519 static cpumask_var_t tick_broadcast_oneshot_mask
;
520 static cpumask_var_t tick_broadcast_pending_mask
;
521 static cpumask_var_t tick_broadcast_force_mask
;
524 * Exposed for debugging: see timer_list.c
526 struct cpumask
*tick_get_broadcast_oneshot_mask(void)
528 return tick_broadcast_oneshot_mask
;
532 * Called before going idle with interrupts disabled. Checks whether a
533 * broadcast event from the other core is about to happen. We detected
534 * that in tick_broadcast_oneshot_control(). The callsite can use this
535 * to avoid a deep idle transition as we are about to get the
536 * broadcast IPI right away.
538 int tick_check_broadcast_expired(void)
540 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask
);
544 * Set broadcast interrupt affinity
546 static void tick_broadcast_set_affinity(struct clock_event_device
*bc
,
547 const struct cpumask
*cpumask
)
549 if (!(bc
->features
& CLOCK_EVT_FEAT_DYNIRQ
))
552 if (cpumask_equal(bc
->cpumask
, cpumask
))
555 bc
->cpumask
= cpumask
;
556 irq_set_affinity(bc
->irq
, bc
->cpumask
);
559 static void tick_broadcast_set_event(struct clock_event_device
*bc
, int cpu
,
562 if (!clockevent_state_oneshot(bc
))
563 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
565 clockevents_program_event(bc
, expires
, 1);
566 tick_broadcast_set_affinity(bc
, cpumask_of(cpu
));
569 static void tick_resume_broadcast_oneshot(struct clock_event_device
*bc
)
571 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
575 * Called from irq_enter() when idle was interrupted to reenable the
578 void tick_check_oneshot_broadcast_this_cpu(void)
580 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask
)) {
581 struct tick_device
*td
= this_cpu_ptr(&tick_cpu_device
);
584 * We might be in the middle of switching over from
585 * periodic to oneshot. If the CPU has not yet
586 * switched over, leave the device alone.
588 if (td
->mode
== TICKDEV_MODE_ONESHOT
) {
589 clockevents_switch_state(td
->evtdev
,
590 CLOCK_EVT_STATE_ONESHOT
);
596 * Handle oneshot mode broadcasting
598 static void tick_handle_oneshot_broadcast(struct clock_event_device
*dev
)
600 struct tick_device
*td
;
601 ktime_t now
, next_event
;
602 int cpu
, next_cpu
= 0;
605 raw_spin_lock(&tick_broadcast_lock
);
606 dev
->next_event
= KTIME_MAX
;
607 next_event
= KTIME_MAX
;
608 cpumask_clear(tmpmask
);
610 /* Find all expired events */
611 for_each_cpu(cpu
, tick_broadcast_oneshot_mask
) {
612 td
= &per_cpu(tick_cpu_device
, cpu
);
613 if (td
->evtdev
->next_event
<= now
) {
614 cpumask_set_cpu(cpu
, tmpmask
);
616 * Mark the remote cpu in the pending mask, so
617 * it can avoid reprogramming the cpu local
618 * timer in tick_broadcast_oneshot_control().
620 cpumask_set_cpu(cpu
, tick_broadcast_pending_mask
);
621 } else if (td
->evtdev
->next_event
< next_event
) {
622 next_event
= td
->evtdev
->next_event
;
628 * Remove the current cpu from the pending mask. The event is
629 * delivered immediately in tick_do_broadcast() !
631 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask
);
633 /* Take care of enforced broadcast requests */
634 cpumask_or(tmpmask
, tmpmask
, tick_broadcast_force_mask
);
635 cpumask_clear(tick_broadcast_force_mask
);
638 * Sanity check. Catch the case where we try to broadcast to
641 if (WARN_ON_ONCE(!cpumask_subset(tmpmask
, cpu_online_mask
)))
642 cpumask_and(tmpmask
, tmpmask
, cpu_online_mask
);
645 * Wakeup the cpus which have an expired event.
647 bc_local
= tick_do_broadcast(tmpmask
);
650 * Two reasons for reprogram:
652 * - The global event did not expire any CPU local
653 * events. This happens in dyntick mode, as the maximum PIT
654 * delta is quite small.
656 * - There are pending events on sleeping CPUs which were not
659 if (next_event
!= KTIME_MAX
)
660 tick_broadcast_set_event(dev
, next_cpu
, next_event
);
662 raw_spin_unlock(&tick_broadcast_lock
);
665 td
= this_cpu_ptr(&tick_cpu_device
);
666 td
->evtdev
->event_handler(td
->evtdev
);
670 static int broadcast_needs_cpu(struct clock_event_device
*bc
, int cpu
)
672 if (!(bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
674 if (bc
->next_event
== KTIME_MAX
)
676 return bc
->bound_on
== cpu
? -EBUSY
: 0;
679 static void broadcast_shutdown_local(struct clock_event_device
*bc
,
680 struct clock_event_device
*dev
)
683 * For hrtimer based broadcasting we cannot shutdown the cpu
684 * local device if our own event is the first one to expire or
685 * if we own the broadcast timer.
687 if (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
) {
688 if (broadcast_needs_cpu(bc
, smp_processor_id()))
690 if (dev
->next_event
< bc
->next_event
)
693 clockevents_switch_state(dev
, CLOCK_EVT_STATE_SHUTDOWN
);
696 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state
)
698 struct clock_event_device
*bc
, *dev
;
703 * If there is no broadcast device, tell the caller not to go
706 if (!tick_broadcast_device
.evtdev
)
709 dev
= this_cpu_ptr(&tick_cpu_device
)->evtdev
;
711 raw_spin_lock(&tick_broadcast_lock
);
712 bc
= tick_broadcast_device
.evtdev
;
713 cpu
= smp_processor_id();
715 if (state
== TICK_BROADCAST_ENTER
) {
717 * If the current CPU owns the hrtimer broadcast
718 * mechanism, it cannot go deep idle and we do not add
719 * the CPU to the broadcast mask. We don't have to go
720 * through the EXIT path as the local timer is not
723 ret
= broadcast_needs_cpu(bc
, cpu
);
728 * If the broadcast device is in periodic mode, we
731 if (tick_broadcast_device
.mode
== TICKDEV_MODE_PERIODIC
) {
732 /* If it is a hrtimer based broadcast, return busy */
733 if (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
)
738 if (!cpumask_test_and_set_cpu(cpu
, tick_broadcast_oneshot_mask
)) {
739 WARN_ON_ONCE(cpumask_test_cpu(cpu
, tick_broadcast_pending_mask
));
741 /* Conditionally shut down the local timer. */
742 broadcast_shutdown_local(bc
, dev
);
745 * We only reprogram the broadcast timer if we
746 * did not mark ourself in the force mask and
747 * if the cpu local event is earlier than the
748 * broadcast event. If the current CPU is in
749 * the force mask, then we are going to be
750 * woken by the IPI right away; we return
751 * busy, so the CPU does not try to go deep
754 if (cpumask_test_cpu(cpu
, tick_broadcast_force_mask
)) {
756 } else if (dev
->next_event
< bc
->next_event
) {
757 tick_broadcast_set_event(bc
, cpu
, dev
->next_event
);
759 * In case of hrtimer broadcasts the
760 * programming might have moved the
761 * timer to this cpu. If yes, remove
762 * us from the broadcast mask and
765 ret
= broadcast_needs_cpu(bc
, cpu
);
767 cpumask_clear_cpu(cpu
,
768 tick_broadcast_oneshot_mask
);
773 if (cpumask_test_and_clear_cpu(cpu
, tick_broadcast_oneshot_mask
)) {
774 clockevents_switch_state(dev
, CLOCK_EVT_STATE_ONESHOT
);
776 * The cpu which was handling the broadcast
777 * timer marked this cpu in the broadcast
778 * pending mask and fired the broadcast
779 * IPI. So we are going to handle the expired
780 * event anyway via the broadcast IPI
781 * handler. No need to reprogram the timer
782 * with an already expired event.
784 if (cpumask_test_and_clear_cpu(cpu
,
785 tick_broadcast_pending_mask
))
789 * Bail out if there is no next event.
791 if (dev
->next_event
== KTIME_MAX
)
794 * If the pending bit is not set, then we are
795 * either the CPU handling the broadcast
796 * interrupt or we got woken by something else.
798 * We are not longer in the broadcast mask, so
799 * if the cpu local expiry time is already
800 * reached, we would reprogram the cpu local
801 * timer with an already expired event.
803 * This can lead to a ping-pong when we return
804 * to idle and therefor rearm the broadcast
805 * timer before the cpu local timer was able
806 * to fire. This happens because the forced
807 * reprogramming makes sure that the event
808 * will happen in the future and depending on
809 * the min_delta setting this might be far
810 * enough out that the ping-pong starts.
812 * If the cpu local next_event has expired
813 * then we know that the broadcast timer
814 * next_event has expired as well and
815 * broadcast is about to be handled. So we
816 * avoid reprogramming and enforce that the
817 * broadcast handler, which did not run yet,
818 * will invoke the cpu local handler.
820 * We cannot call the handler directly from
821 * here, because we might be in a NOHZ phase
822 * and we did not go through the irq_enter()
826 if (dev
->next_event
<= now
) {
827 cpumask_set_cpu(cpu
, tick_broadcast_force_mask
);
831 * We got woken by something else. Reprogram
832 * the cpu local timer device.
834 tick_program_event(dev
->next_event
, 1);
838 raw_spin_unlock(&tick_broadcast_lock
);
843 * Reset the one shot broadcast for a cpu
845 * Called with tick_broadcast_lock held
847 static void tick_broadcast_clear_oneshot(int cpu
)
849 cpumask_clear_cpu(cpu
, tick_broadcast_oneshot_mask
);
850 cpumask_clear_cpu(cpu
, tick_broadcast_pending_mask
);
853 static void tick_broadcast_init_next_event(struct cpumask
*mask
,
856 struct tick_device
*td
;
859 for_each_cpu(cpu
, mask
) {
860 td
= &per_cpu(tick_cpu_device
, cpu
);
862 td
->evtdev
->next_event
= expires
;
867 * tick_broadcast_setup_oneshot - setup the broadcast device
869 void tick_broadcast_setup_oneshot(struct clock_event_device
*bc
)
871 int cpu
= smp_processor_id();
876 /* Set it up only once ! */
877 if (bc
->event_handler
!= tick_handle_oneshot_broadcast
) {
878 int was_periodic
= clockevent_state_periodic(bc
);
880 bc
->event_handler
= tick_handle_oneshot_broadcast
;
883 * We must be careful here. There might be other CPUs
884 * waiting for periodic broadcast. We need to set the
885 * oneshot_mask bits for those and program the
886 * broadcast device to fire.
888 cpumask_copy(tmpmask
, tick_broadcast_mask
);
889 cpumask_clear_cpu(cpu
, tmpmask
);
890 cpumask_or(tick_broadcast_oneshot_mask
,
891 tick_broadcast_oneshot_mask
, tmpmask
);
893 if (was_periodic
&& !cpumask_empty(tmpmask
)) {
894 clockevents_switch_state(bc
, CLOCK_EVT_STATE_ONESHOT
);
895 tick_broadcast_init_next_event(tmpmask
,
897 tick_broadcast_set_event(bc
, cpu
, tick_next_period
);
899 bc
->next_event
= KTIME_MAX
;
902 * The first cpu which switches to oneshot mode sets
903 * the bit for all other cpus which are in the general
904 * (periodic) broadcast mask. So the bit is set and
905 * would prevent the first broadcast enter after this
906 * to program the bc device.
908 tick_broadcast_clear_oneshot(cpu
);
913 * Select oneshot operating mode for the broadcast device
915 void tick_broadcast_switch_to_oneshot(void)
917 struct clock_event_device
*bc
;
920 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
922 tick_broadcast_device
.mode
= TICKDEV_MODE_ONESHOT
;
923 bc
= tick_broadcast_device
.evtdev
;
925 tick_broadcast_setup_oneshot(bc
);
927 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
930 #ifdef CONFIG_HOTPLUG_CPU
931 void hotplug_cpu__broadcast_tick_pull(int deadcpu
)
933 struct clock_event_device
*bc
;
936 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
937 bc
= tick_broadcast_device
.evtdev
;
939 if (bc
&& broadcast_needs_cpu(bc
, deadcpu
)) {
940 /* This moves the broadcast assignment to this CPU: */
941 clockevents_program_event(bc
, bc
->next_event
, 1);
943 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
947 * Remove a dead CPU from broadcasting
949 void tick_shutdown_broadcast_oneshot(unsigned int cpu
)
953 raw_spin_lock_irqsave(&tick_broadcast_lock
, flags
);
956 * Clear the broadcast masks for the dead cpu, but do not stop
957 * the broadcast device!
959 cpumask_clear_cpu(cpu
, tick_broadcast_oneshot_mask
);
960 cpumask_clear_cpu(cpu
, tick_broadcast_pending_mask
);
961 cpumask_clear_cpu(cpu
, tick_broadcast_force_mask
);
963 raw_spin_unlock_irqrestore(&tick_broadcast_lock
, flags
);
968 * Check, whether the broadcast device is in one shot mode
970 int tick_broadcast_oneshot_active(void)
972 return tick_broadcast_device
.mode
== TICKDEV_MODE_ONESHOT
;
976 * Check whether the broadcast device supports oneshot.
978 bool tick_broadcast_oneshot_available(void)
980 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
982 return bc
? bc
->features
& CLOCK_EVT_FEAT_ONESHOT
: false;
986 int __tick_broadcast_oneshot_control(enum tick_broadcast_state state
)
988 struct clock_event_device
*bc
= tick_broadcast_device
.evtdev
;
990 if (!bc
|| (bc
->features
& CLOCK_EVT_FEAT_HRTIMER
))
997 void __init
tick_broadcast_init(void)
999 zalloc_cpumask_var(&tick_broadcast_mask
, GFP_NOWAIT
);
1000 zalloc_cpumask_var(&tick_broadcast_on
, GFP_NOWAIT
);
1001 zalloc_cpumask_var(&tmpmask
, GFP_NOWAIT
);
1002 #ifdef CONFIG_TICK_ONESHOT
1003 zalloc_cpumask_var(&tick_broadcast_oneshot_mask
, GFP_NOWAIT
);
1004 zalloc_cpumask_var(&tick_broadcast_pending_mask
, GFP_NOWAIT
);
1005 zalloc_cpumask_var(&tick_broadcast_force_mask
, GFP_NOWAIT
);