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1/*
2 * linux/kernel/time/tick-broadcast.c
3 *
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
6 *
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
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
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>
23
24#include "tick-internal.h"
25
26/*
27 * Broadcast support for broken x86 hardware, where the local apic
28 * timer stops in C3 state.
29 */
30
31static struct tick_device tick_broadcast_device;
32static cpumask_var_t tick_broadcast_mask;
33static cpumask_var_t tick_broadcast_on;
34static cpumask_var_t tmpmask;
35static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
36static int tick_broadcast_force;
37
38#ifdef CONFIG_TICK_ONESHOT
39static void tick_broadcast_clear_oneshot(int cpu);
40#else
41static inline void tick_broadcast_clear_oneshot(int cpu) { }
42#endif
43
44/*
45 * Debugging: see timer_list.c
46 */
47struct tick_device *tick_get_broadcast_device(void)
48{
49 return &tick_broadcast_device;
50}
51
52struct cpumask *tick_get_broadcast_mask(void)
53{
54 return tick_broadcast_mask;
55}
56
57/*
58 * Start the device in periodic mode
59 */
60static void tick_broadcast_start_periodic(struct clock_event_device *bc)
61{
62 if (bc)
63 tick_setup_periodic(bc, 1);
64}
65
66/*
67 * Check, if the device can be utilized as broadcast device:
68 */
69static bool tick_check_broadcast_device(struct clock_event_device *curdev,
70 struct clock_event_device *newdev)
71{
72 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
73 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
74 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
75 return false;
76
77 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
78 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
79 return false;
80
81 return !curdev || newdev->rating > curdev->rating;
82}
83
84/*
85 * Conditionally install/replace broadcast device
86 */
87void tick_install_broadcast_device(struct clock_event_device *dev)
88{
89 struct clock_event_device *cur = tick_broadcast_device.evtdev;
90
91 if (!tick_check_broadcast_device(cur, dev))
92 return;
93
94 if (!try_module_get(dev->owner))
95 return;
96
97 clockevents_exchange_device(cur, dev);
98 if (cur)
99 cur->event_handler = clockevents_handle_noop;
100 tick_broadcast_device.evtdev = dev;
101 if (!cpumask_empty(tick_broadcast_mask))
102 tick_broadcast_start_periodic(dev);
103 /*
104 * Inform all cpus about this. We might be in a situation
105 * where we did not switch to oneshot mode because the per cpu
106 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
107 * of a oneshot capable broadcast device. Without that
108 * notification the systems stays stuck in periodic mode
109 * forever.
110 */
111 if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
112 tick_clock_notify();
113}
114
115/*
116 * Check, if the device is the broadcast device
117 */
118int tick_is_broadcast_device(struct clock_event_device *dev)
119{
120 return (dev && tick_broadcast_device.evtdev == dev);
121}
122
123int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
124{
125 int ret = -ENODEV;
126
127 if (tick_is_broadcast_device(dev)) {
128 raw_spin_lock(&tick_broadcast_lock);
129 ret = __clockevents_update_freq(dev, freq);
130 raw_spin_unlock(&tick_broadcast_lock);
131 }
132 return ret;
133}
134
135
136static void err_broadcast(const struct cpumask *mask)
137{
138 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
139}
140
141static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
142{
143 if (!dev->broadcast)
144 dev->broadcast = tick_broadcast;
145 if (!dev->broadcast) {
146 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
147 dev->name);
148 dev->broadcast = err_broadcast;
149 }
150}
151
152/*
153 * Check, if the device is disfunctional and a place holder, which
154 * needs to be handled by the broadcast device.
155 */
156int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
157{
158 struct clock_event_device *bc = tick_broadcast_device.evtdev;
159 unsigned long flags;
160 int ret;
161
162 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
163
164 /*
165 * Devices might be registered with both periodic and oneshot
166 * mode disabled. This signals, that the device needs to be
167 * operated from the broadcast device and is a placeholder for
168 * the cpu local device.
169 */
170 if (!tick_device_is_functional(dev)) {
171 dev->event_handler = tick_handle_periodic;
172 tick_device_setup_broadcast_func(dev);
173 cpumask_set_cpu(cpu, tick_broadcast_mask);
174 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
175 tick_broadcast_start_periodic(bc);
176 else
177 tick_broadcast_setup_oneshot(bc);
178 ret = 1;
179 } else {
180 /*
181 * Clear the broadcast bit for this cpu if the
182 * device is not power state affected.
183 */
184 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
185 cpumask_clear_cpu(cpu, tick_broadcast_mask);
186 else
187 tick_device_setup_broadcast_func(dev);
188
189 /*
190 * Clear the broadcast bit if the CPU is not in
191 * periodic broadcast on state.
192 */
193 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
194 cpumask_clear_cpu(cpu, tick_broadcast_mask);
195
196 switch (tick_broadcast_device.mode) {
197 case TICKDEV_MODE_ONESHOT:
198 /*
199 * If the system is in oneshot mode we can
200 * unconditionally clear the oneshot mask bit,
201 * because the CPU is running and therefore
202 * not in an idle state which causes the power
203 * state affected device to stop. Let the
204 * caller initialize the device.
205 */
206 tick_broadcast_clear_oneshot(cpu);
207 ret = 0;
208 break;
209
210 case TICKDEV_MODE_PERIODIC:
211 /*
212 * If the system is in periodic mode, check
213 * whether the broadcast device can be
214 * switched off now.
215 */
216 if (cpumask_empty(tick_broadcast_mask) && bc)
217 clockevents_shutdown(bc);
218 /*
219 * If we kept the cpu in the broadcast mask,
220 * tell the caller to leave the per cpu device
221 * in shutdown state. The periodic interrupt
222 * is delivered by the broadcast device.
223 */
224 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
225 break;
226 default:
227 /* Nothing to do */
228 ret = 0;
229 break;
230 }
231 }
232 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
233 return ret;
234}
235
236#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
237int tick_receive_broadcast(void)
238{
239 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
240 struct clock_event_device *evt = td->evtdev;
241
242 if (!evt)
243 return -ENODEV;
244
245 if (!evt->event_handler)
246 return -EINVAL;
247
248 evt->event_handler(evt);
249 return 0;
250}
251#endif
252
253/*
254 * Broadcast the event to the cpus, which are set in the mask (mangled).
255 */
256static void tick_do_broadcast(struct cpumask *mask)
257{
258 int cpu = smp_processor_id();
259 struct tick_device *td;
260
261 /*
262 * Check, if the current cpu is in the mask
263 */
264 if (cpumask_test_cpu(cpu, mask)) {
265 cpumask_clear_cpu(cpu, mask);
266 td = &per_cpu(tick_cpu_device, cpu);
267 td->evtdev->event_handler(td->evtdev);
268 }
269
270 if (!cpumask_empty(mask)) {
271 /*
272 * It might be necessary to actually check whether the devices
273 * have different broadcast functions. For now, just use the
274 * one of the first device. This works as long as we have this
275 * misfeature only on x86 (lapic)
276 */
277 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
278 td->evtdev->broadcast(mask);
279 }
280}
281
282/*
283 * Periodic broadcast:
284 * - invoke the broadcast handlers
285 */
286static void tick_do_periodic_broadcast(void)
287{
288 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
289 tick_do_broadcast(tmpmask);
290}
291
292/*
293 * Event handler for periodic broadcast ticks
294 */
295static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
296{
297 ktime_t next;
298
299 raw_spin_lock(&tick_broadcast_lock);
300
301 tick_do_periodic_broadcast();
302
303 /*
304 * The device is in periodic mode. No reprogramming necessary:
305 */
306 if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
307 goto unlock;
308
309 /*
310 * Setup the next period for devices, which do not have
311 * periodic mode. We read dev->next_event first and add to it
312 * when the event already expired. clockevents_program_event()
313 * sets dev->next_event only when the event is really
314 * programmed to the device.
315 */
316 for (next = dev->next_event; ;) {
317 next = ktime_add(next, tick_period);
318
319 if (!clockevents_program_event(dev, next, false))
320 goto unlock;
321 tick_do_periodic_broadcast();
322 }
323unlock:
324 raw_spin_unlock(&tick_broadcast_lock);
325}
326
327/*
328 * Powerstate information: The system enters/leaves a state, where
329 * affected devices might stop
330 */
331static void tick_do_broadcast_on_off(unsigned long *reason)
332{
333 struct clock_event_device *bc, *dev;
334 struct tick_device *td;
335 unsigned long flags;
336 int cpu, bc_stopped;
337
338 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
339
340 cpu = smp_processor_id();
341 td = &per_cpu(tick_cpu_device, cpu);
342 dev = td->evtdev;
343 bc = tick_broadcast_device.evtdev;
344
345 /*
346 * Is the device not affected by the powerstate ?
347 */
348 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
349 goto out;
350
351 if (!tick_device_is_functional(dev))
352 goto out;
353
354 bc_stopped = cpumask_empty(tick_broadcast_mask);
355
356 switch (*reason) {
357 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
358 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
359 cpumask_set_cpu(cpu, tick_broadcast_on);
360 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
361 if (tick_broadcast_device.mode ==
362 TICKDEV_MODE_PERIODIC)
363 clockevents_shutdown(dev);
364 }
365 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
366 tick_broadcast_force = 1;
367 break;
368 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
369 if (tick_broadcast_force)
370 break;
371 cpumask_clear_cpu(cpu, tick_broadcast_on);
372 if (!tick_device_is_functional(dev))
373 break;
374 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
375 if (tick_broadcast_device.mode ==
376 TICKDEV_MODE_PERIODIC)
377 tick_setup_periodic(dev, 0);
378 }
379 break;
380 }
381
382 if (cpumask_empty(tick_broadcast_mask)) {
383 if (!bc_stopped)
384 clockevents_shutdown(bc);
385 } else if (bc_stopped) {
386 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
387 tick_broadcast_start_periodic(bc);
388 else
389 tick_broadcast_setup_oneshot(bc);
390 }
391out:
392 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
393}
394
395/*
396 * Powerstate information: The system enters/leaves a state, where
397 * affected devices might stop.
398 */
399void tick_broadcast_on_off(unsigned long reason, int *oncpu)
400{
401 if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
402 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
403 "offline CPU #%d\n", *oncpu);
404 else
405 tick_do_broadcast_on_off(&reason);
406}
407
408/*
409 * Set the periodic handler depending on broadcast on/off
410 */
411void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
412{
413 if (!broadcast)
414 dev->event_handler = tick_handle_periodic;
415 else
416 dev->event_handler = tick_handle_periodic_broadcast;
417}
418
419/*
420 * Remove a CPU from broadcasting
421 */
422void tick_shutdown_broadcast(unsigned int *cpup)
423{
424 struct clock_event_device *bc;
425 unsigned long flags;
426 unsigned int cpu = *cpup;
427
428 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
429
430 bc = tick_broadcast_device.evtdev;
431 cpumask_clear_cpu(cpu, tick_broadcast_mask);
432 cpumask_clear_cpu(cpu, tick_broadcast_on);
433
434 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
435 if (bc && cpumask_empty(tick_broadcast_mask))
436 clockevents_shutdown(bc);
437 }
438
439 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
440}
441
442void tick_suspend_broadcast(void)
443{
444 struct clock_event_device *bc;
445 unsigned long flags;
446
447 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
448
449 bc = tick_broadcast_device.evtdev;
450 if (bc)
451 clockevents_shutdown(bc);
452
453 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
454}
455
456int tick_resume_broadcast(void)
457{
458 struct clock_event_device *bc;
459 unsigned long flags;
460 int broadcast = 0;
461
462 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
463
464 bc = tick_broadcast_device.evtdev;
465
466 if (bc) {
467 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
468
469 switch (tick_broadcast_device.mode) {
470 case TICKDEV_MODE_PERIODIC:
471 if (!cpumask_empty(tick_broadcast_mask))
472 tick_broadcast_start_periodic(bc);
473 broadcast = cpumask_test_cpu(smp_processor_id(),
474 tick_broadcast_mask);
475 break;
476 case TICKDEV_MODE_ONESHOT:
477 if (!cpumask_empty(tick_broadcast_mask))
478 broadcast = tick_resume_broadcast_oneshot(bc);
479 break;
480 }
481 }
482 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
483
484 return broadcast;
485}
486
487
488#ifdef CONFIG_TICK_ONESHOT
489
490static cpumask_var_t tick_broadcast_oneshot_mask;
491static cpumask_var_t tick_broadcast_pending_mask;
492static cpumask_var_t tick_broadcast_force_mask;
493
494/*
495 * Exposed for debugging: see timer_list.c
496 */
497struct cpumask *tick_get_broadcast_oneshot_mask(void)
498{
499 return tick_broadcast_oneshot_mask;
500}
501
502/*
503 * Called before going idle with interrupts disabled. Checks whether a
504 * broadcast event from the other core is about to happen. We detected
505 * that in tick_broadcast_oneshot_control(). The callsite can use this
506 * to avoid a deep idle transition as we are about to get the
507 * broadcast IPI right away.
508 */
509int tick_check_broadcast_expired(void)
510{
511 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
512}
513
514/*
515 * Set broadcast interrupt affinity
516 */
517static void tick_broadcast_set_affinity(struct clock_event_device *bc,
518 const struct cpumask *cpumask)
519{
520 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
521 return;
522
523 if (cpumask_equal(bc->cpumask, cpumask))
524 return;
525
526 bc->cpumask = cpumask;
527 irq_set_affinity(bc->irq, bc->cpumask);
528}
529
530static int tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
531 ktime_t expires, int force)
532{
533 int ret;
534
535 if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
536 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
537
538 ret = clockevents_program_event(bc, expires, force);
539 if (!ret)
540 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
541 return ret;
542}
543
544int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
545{
546 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
547 return 0;
548}
549
550/*
551 * Called from irq_enter() when idle was interrupted to reenable the
552 * per cpu device.
553 */
554void tick_check_oneshot_broadcast_this_cpu(void)
555{
556 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
557 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
558
559 /*
560 * We might be in the middle of switching over from
561 * periodic to oneshot. If the CPU has not yet
562 * switched over, leave the device alone.
563 */
564 if (td->mode == TICKDEV_MODE_ONESHOT) {
565 clockevents_set_mode(td->evtdev,
566 CLOCK_EVT_MODE_ONESHOT);
567 }
568 }
569}
570
571/*
572 * Handle oneshot mode broadcasting
573 */
574static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
575{
576 struct tick_device *td;
577 ktime_t now, next_event;
578 int cpu, next_cpu = 0;
579
580 raw_spin_lock(&tick_broadcast_lock);
581again:
582 dev->next_event.tv64 = KTIME_MAX;
583 next_event.tv64 = KTIME_MAX;
584 cpumask_clear(tmpmask);
585 now = ktime_get();
586 /* Find all expired events */
587 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
588 td = &per_cpu(tick_cpu_device, cpu);
589 if (td->evtdev->next_event.tv64 <= now.tv64) {
590 cpumask_set_cpu(cpu, tmpmask);
591 /*
592 * Mark the remote cpu in the pending mask, so
593 * it can avoid reprogramming the cpu local
594 * timer in tick_broadcast_oneshot_control().
595 */
596 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
597 } else if (td->evtdev->next_event.tv64 < next_event.tv64) {
598 next_event.tv64 = td->evtdev->next_event.tv64;
599 next_cpu = cpu;
600 }
601 }
602
603 /*
604 * Remove the current cpu from the pending mask. The event is
605 * delivered immediately in tick_do_broadcast() !
606 */
607 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
608
609 /* Take care of enforced broadcast requests */
610 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
611 cpumask_clear(tick_broadcast_force_mask);
612
613 /*
614 * Sanity check. Catch the case where we try to broadcast to
615 * offline cpus.
616 */
617 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
618 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
619
620 /*
621 * Wakeup the cpus which have an expired event.
622 */
623 tick_do_broadcast(tmpmask);
624
625 /*
626 * Two reasons for reprogram:
627 *
628 * - The global event did not expire any CPU local
629 * events. This happens in dyntick mode, as the maximum PIT
630 * delta is quite small.
631 *
632 * - There are pending events on sleeping CPUs which were not
633 * in the event mask
634 */
635 if (next_event.tv64 != KTIME_MAX) {
636 /*
637 * Rearm the broadcast device. If event expired,
638 * repeat the above
639 */
640 if (tick_broadcast_set_event(dev, next_cpu, next_event, 0))
641 goto again;
642 }
643 raw_spin_unlock(&tick_broadcast_lock);
644}
645
646static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
647{
648 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
649 return 0;
650 if (bc->next_event.tv64 == KTIME_MAX)
651 return 0;
652 return bc->bound_on == cpu ? -EBUSY : 0;
653}
654
655static void broadcast_shutdown_local(struct clock_event_device *bc,
656 struct clock_event_device *dev)
657{
658 /*
659 * For hrtimer based broadcasting we cannot shutdown the cpu
660 * local device if our own event is the first one to expire or
661 * if we own the broadcast timer.
662 */
663 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
664 if (broadcast_needs_cpu(bc, smp_processor_id()))
665 return;
666 if (dev->next_event.tv64 < bc->next_event.tv64)
667 return;
668 }
669 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
670}
671
672static void broadcast_move_bc(int deadcpu)
673{
674 struct clock_event_device *bc = tick_broadcast_device.evtdev;
675
676 if (!bc || !broadcast_needs_cpu(bc, deadcpu))
677 return;
678 /* This moves the broadcast assignment to this cpu */
679 clockevents_program_event(bc, bc->next_event, 1);
680}
681
682/*
683 * Powerstate information: The system enters/leaves a state, where
684 * affected devices might stop
685 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
686 */
687int tick_broadcast_oneshot_control(unsigned long reason)
688{
689 struct clock_event_device *bc, *dev;
690 struct tick_device *td;
691 unsigned long flags;
692 ktime_t now;
693 int cpu, ret = 0;
694
695 /*
696 * Periodic mode does not care about the enter/exit of power
697 * states
698 */
699 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
700 return 0;
701
702 /*
703 * We are called with preemtion disabled from the depth of the
704 * idle code, so we can't be moved away.
705 */
706 cpu = smp_processor_id();
707 td = &per_cpu(tick_cpu_device, cpu);
708 dev = td->evtdev;
709
710 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
711 return 0;
712
713 bc = tick_broadcast_device.evtdev;
714
715 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
716 if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
717 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
718 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
719 broadcast_shutdown_local(bc, dev);
720 /*
721 * We only reprogram the broadcast timer if we
722 * did not mark ourself in the force mask and
723 * if the cpu local event is earlier than the
724 * broadcast event. If the current CPU is in
725 * the force mask, then we are going to be
726 * woken by the IPI right away.
727 */
728 if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
729 dev->next_event.tv64 < bc->next_event.tv64)
730 tick_broadcast_set_event(bc, cpu, dev->next_event, 1);
731 }
732 /*
733 * If the current CPU owns the hrtimer broadcast
734 * mechanism, it cannot go deep idle and we remove the
735 * CPU from the broadcast mask. We don't have to go
736 * through the EXIT path as the local timer is not
737 * shutdown.
738 */
739 ret = broadcast_needs_cpu(bc, cpu);
740 if (ret)
741 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
742 } else {
743 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
744 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
745 /*
746 * The cpu which was handling the broadcast
747 * timer marked this cpu in the broadcast
748 * pending mask and fired the broadcast
749 * IPI. So we are going to handle the expired
750 * event anyway via the broadcast IPI
751 * handler. No need to reprogram the timer
752 * with an already expired event.
753 */
754 if (cpumask_test_and_clear_cpu(cpu,
755 tick_broadcast_pending_mask))
756 goto out;
757
758 /*
759 * Bail out if there is no next event.
760 */
761 if (dev->next_event.tv64 == KTIME_MAX)
762 goto out;
763 /*
764 * If the pending bit is not set, then we are
765 * either the CPU handling the broadcast
766 * interrupt or we got woken by something else.
767 *
768 * We are not longer in the broadcast mask, so
769 * if the cpu local expiry time is already
770 * reached, we would reprogram the cpu local
771 * timer with an already expired event.
772 *
773 * This can lead to a ping-pong when we return
774 * to idle and therefor rearm the broadcast
775 * timer before the cpu local timer was able
776 * to fire. This happens because the forced
777 * reprogramming makes sure that the event
778 * will happen in the future and depending on
779 * the min_delta setting this might be far
780 * enough out that the ping-pong starts.
781 *
782 * If the cpu local next_event has expired
783 * then we know that the broadcast timer
784 * next_event has expired as well and
785 * broadcast is about to be handled. So we
786 * avoid reprogramming and enforce that the
787 * broadcast handler, which did not run yet,
788 * will invoke the cpu local handler.
789 *
790 * We cannot call the handler directly from
791 * here, because we might be in a NOHZ phase
792 * and we did not go through the irq_enter()
793 * nohz fixups.
794 */
795 now = ktime_get();
796 if (dev->next_event.tv64 <= now.tv64) {
797 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
798 goto out;
799 }
800 /*
801 * We got woken by something else. Reprogram
802 * the cpu local timer device.
803 */
804 tick_program_event(dev->next_event, 1);
805 }
806 }
807out:
808 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
809 return ret;
810}
811
812/*
813 * Reset the one shot broadcast for a cpu
814 *
815 * Called with tick_broadcast_lock held
816 */
817static void tick_broadcast_clear_oneshot(int cpu)
818{
819 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
820 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
821}
822
823static void tick_broadcast_init_next_event(struct cpumask *mask,
824 ktime_t expires)
825{
826 struct tick_device *td;
827 int cpu;
828
829 for_each_cpu(cpu, mask) {
830 td = &per_cpu(tick_cpu_device, cpu);
831 if (td->evtdev)
832 td->evtdev->next_event = expires;
833 }
834}
835
836/**
837 * tick_broadcast_setup_oneshot - setup the broadcast device
838 */
839void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
840{
841 int cpu = smp_processor_id();
842
843 /* Set it up only once ! */
844 if (bc->event_handler != tick_handle_oneshot_broadcast) {
845 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
846
847 bc->event_handler = tick_handle_oneshot_broadcast;
848
849 /*
850 * We must be careful here. There might be other CPUs
851 * waiting for periodic broadcast. We need to set the
852 * oneshot_mask bits for those and program the
853 * broadcast device to fire.
854 */
855 cpumask_copy(tmpmask, tick_broadcast_mask);
856 cpumask_clear_cpu(cpu, tmpmask);
857 cpumask_or(tick_broadcast_oneshot_mask,
858 tick_broadcast_oneshot_mask, tmpmask);
859
860 if (was_periodic && !cpumask_empty(tmpmask)) {
861 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
862 tick_broadcast_init_next_event(tmpmask,
863 tick_next_period);
864 tick_broadcast_set_event(bc, cpu, tick_next_period, 1);
865 } else
866 bc->next_event.tv64 = KTIME_MAX;
867 } else {
868 /*
869 * The first cpu which switches to oneshot mode sets
870 * the bit for all other cpus which are in the general
871 * (periodic) broadcast mask. So the bit is set and
872 * would prevent the first broadcast enter after this
873 * to program the bc device.
874 */
875 tick_broadcast_clear_oneshot(cpu);
876 }
877}
878
879/*
880 * Select oneshot operating mode for the broadcast device
881 */
882void tick_broadcast_switch_to_oneshot(void)
883{
884 struct clock_event_device *bc;
885 unsigned long flags;
886
887 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
888
889 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
890 bc = tick_broadcast_device.evtdev;
891 if (bc)
892 tick_broadcast_setup_oneshot(bc);
893
894 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
895}
896
897
898/*
899 * Remove a dead CPU from broadcasting
900 */
901void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
902{
903 unsigned long flags;
904 unsigned int cpu = *cpup;
905
906 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
907
908 /*
909 * Clear the broadcast masks for the dead cpu, but do not stop
910 * the broadcast device!
911 */
912 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
913 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
914 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
915
916 broadcast_move_bc(cpu);
917
918 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
919}
920
921/*
922 * Check, whether the broadcast device is in one shot mode
923 */
924int tick_broadcast_oneshot_active(void)
925{
926 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
927}
928
929/*
930 * Check whether the broadcast device supports oneshot.
931 */
932bool tick_broadcast_oneshot_available(void)
933{
934 struct clock_event_device *bc = tick_broadcast_device.evtdev;
935
936 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
937}
938
939#endif
940
941void __init tick_broadcast_init(void)
942{
943 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
944 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
945 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
946#ifdef CONFIG_TICK_ONESHOT
947 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
948 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
949 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
950#endif
951}
1/*
2 * linux/kernel/time/tick-broadcast.c
3 *
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
6 *
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
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
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>
23
24#include "tick-internal.h"
25
26/*
27 * Broadcast support for broken x86 hardware, where the local apic
28 * timer stops in C3 state.
29 */
30
31static struct tick_device tick_broadcast_device;
32static cpumask_var_t tick_broadcast_mask;
33static cpumask_var_t tick_broadcast_on;
34static cpumask_var_t tmpmask;
35static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
36static int tick_broadcast_forced;
37
38#ifdef CONFIG_TICK_ONESHOT
39static void tick_broadcast_clear_oneshot(int cpu);
40static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
41#else
42static inline void tick_broadcast_clear_oneshot(int cpu) { }
43static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
44#endif
45
46/*
47 * Debugging: see timer_list.c
48 */
49struct tick_device *tick_get_broadcast_device(void)
50{
51 return &tick_broadcast_device;
52}
53
54struct cpumask *tick_get_broadcast_mask(void)
55{
56 return tick_broadcast_mask;
57}
58
59/*
60 * Start the device in periodic mode
61 */
62static void tick_broadcast_start_periodic(struct clock_event_device *bc)
63{
64 if (bc)
65 tick_setup_periodic(bc, 1);
66}
67
68/*
69 * Check, if the device can be utilized as broadcast device:
70 */
71static bool tick_check_broadcast_device(struct clock_event_device *curdev,
72 struct clock_event_device *newdev)
73{
74 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
75 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
76 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
77 return false;
78
79 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
80 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
81 return false;
82
83 return !curdev || newdev->rating > curdev->rating;
84}
85
86/*
87 * Conditionally install/replace broadcast device
88 */
89void tick_install_broadcast_device(struct clock_event_device *dev)
90{
91 struct clock_event_device *cur = tick_broadcast_device.evtdev;
92
93 if (!tick_check_broadcast_device(cur, dev))
94 return;
95
96 if (!try_module_get(dev->owner))
97 return;
98
99 clockevents_exchange_device(cur, dev);
100 if (cur)
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);
105 /*
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
111 * forever.
112 */
113 if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
114 tick_clock_notify();
115}
116
117/*
118 * Check, if the device is the broadcast device
119 */
120int tick_is_broadcast_device(struct clock_event_device *dev)
121{
122 return (dev && tick_broadcast_device.evtdev == dev);
123}
124
125int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
126{
127 int ret = -ENODEV;
128
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);
133 }
134 return ret;
135}
136
137
138static void err_broadcast(const struct cpumask *mask)
139{
140 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
141}
142
143static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
144{
145 if (!dev->broadcast)
146 dev->broadcast = tick_broadcast;
147 if (!dev->broadcast) {
148 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
149 dev->name);
150 dev->broadcast = err_broadcast;
151 }
152}
153
154/*
155 * Check, if the device is disfunctional and a place holder, which
156 * needs to be handled by the broadcast device.
157 */
158int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
159{
160 struct clock_event_device *bc = tick_broadcast_device.evtdev;
161 unsigned long flags;
162 int ret = 0;
163
164 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
165
166 /*
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.
171 */
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);
178 else
179 tick_broadcast_setup_oneshot(bc);
180 ret = 1;
181 } else {
182 /*
183 * Clear the broadcast bit for this cpu if the
184 * device is not power state affected.
185 */
186 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
187 cpumask_clear_cpu(cpu, tick_broadcast_mask);
188 else
189 tick_device_setup_broadcast_func(dev);
190
191 /*
192 * Clear the broadcast bit if the CPU is not in
193 * periodic broadcast on state.
194 */
195 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
196 cpumask_clear_cpu(cpu, tick_broadcast_mask);
197
198 switch (tick_broadcast_device.mode) {
199 case TICKDEV_MODE_ONESHOT:
200 /*
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.
207 */
208 tick_broadcast_clear_oneshot(cpu);
209 ret = 0;
210 break;
211
212 case TICKDEV_MODE_PERIODIC:
213 /*
214 * If the system is in periodic mode, check
215 * whether the broadcast device can be
216 * switched off now.
217 */
218 if (cpumask_empty(tick_broadcast_mask) && bc)
219 clockevents_shutdown(bc);
220 /*
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
226 * hrtimer based.
227 */
228 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
229 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
230 break;
231 default:
232 break;
233 }
234 }
235 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
236 return ret;
237}
238
239#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
240int tick_receive_broadcast(void)
241{
242 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
243 struct clock_event_device *evt = td->evtdev;
244
245 if (!evt)
246 return -ENODEV;
247
248 if (!evt->event_handler)
249 return -EINVAL;
250
251 evt->event_handler(evt);
252 return 0;
253}
254#endif
255
256/*
257 * Broadcast the event to the cpus, which are set in the mask (mangled).
258 */
259static bool tick_do_broadcast(struct cpumask *mask)
260{
261 int cpu = smp_processor_id();
262 struct tick_device *td;
263 bool local = false;
264
265 /*
266 * Check, if the current cpu is in the mask
267 */
268 if (cpumask_test_cpu(cpu, mask)) {
269 struct clock_event_device *bc = tick_broadcast_device.evtdev;
270
271 cpumask_clear_cpu(cpu, mask);
272 /*
273 * We only run the local handler, if the broadcast
274 * device is not hrtimer based. Otherwise we run into
275 * a hrtimer recursion.
276 *
277 * local timer_interrupt()
278 * local_handler()
279 * expire_hrtimers()
280 * bc_handler()
281 * local_handler()
282 * expire_hrtimers()
283 */
284 local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
285 }
286
287 if (!cpumask_empty(mask)) {
288 /*
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)
293 */
294 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
295 td->evtdev->broadcast(mask);
296 }
297 return local;
298}
299
300/*
301 * Periodic broadcast:
302 * - invoke the broadcast handlers
303 */
304static bool tick_do_periodic_broadcast(void)
305{
306 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
307 return tick_do_broadcast(tmpmask);
308}
309
310/*
311 * Event handler for periodic broadcast ticks
312 */
313static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
314{
315 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
316 bool bc_local;
317
318 raw_spin_lock(&tick_broadcast_lock);
319
320 /* Handle spurious interrupts gracefully */
321 if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
322 raw_spin_unlock(&tick_broadcast_lock);
323 return;
324 }
325
326 bc_local = tick_do_periodic_broadcast();
327
328 if (clockevent_state_oneshot(dev)) {
329 ktime_t next = ktime_add(dev->next_event, tick_period);
330
331 clockevents_program_event(dev, next, true);
332 }
333 raw_spin_unlock(&tick_broadcast_lock);
334
335 /*
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.
339 */
340 if (bc_local)
341 td->evtdev->event_handler(td->evtdev);
342}
343
344/**
345 * tick_broadcast_control - Enable/disable or force broadcast mode
346 * @mode: The selected broadcast mode
347 *
348 * Called when the system enters a state where affected tick devices
349 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
350 */
351void tick_broadcast_control(enum tick_broadcast_mode mode)
352{
353 struct clock_event_device *bc, *dev;
354 struct tick_device *td;
355 int cpu, bc_stopped;
356 unsigned long flags;
357
358 /* Protects also the local clockevent device. */
359 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
360 td = this_cpu_ptr(&tick_cpu_device);
361 dev = td->evtdev;
362
363 /*
364 * Is the device not affected by the powerstate ?
365 */
366 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
367 goto out;
368
369 if (!tick_device_is_functional(dev))
370 goto out;
371
372 cpu = smp_processor_id();
373 bc = tick_broadcast_device.evtdev;
374 bc_stopped = cpumask_empty(tick_broadcast_mask);
375
376 switch (mode) {
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)) {
382 /*
383 * Only shutdown the cpu local device, if:
384 *
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
389 */
390 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
391 tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
392 clockevents_shutdown(dev);
393 }
394 break;
395
396 case TICK_BROADCAST_OFF:
397 if (tick_broadcast_forced)
398 break;
399 cpumask_clear_cpu(cpu, tick_broadcast_on);
400 if (!tick_device_is_functional(dev))
401 break;
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);
406 }
407 break;
408 }
409
410 if (bc) {
411 if (cpumask_empty(tick_broadcast_mask)) {
412 if (!bc_stopped)
413 clockevents_shutdown(bc);
414 } else if (bc_stopped) {
415 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
416 tick_broadcast_start_periodic(bc);
417 else
418 tick_broadcast_setup_oneshot(bc);
419 }
420 }
421out:
422 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
423}
424EXPORT_SYMBOL_GPL(tick_broadcast_control);
425
426/*
427 * Set the periodic handler depending on broadcast on/off
428 */
429void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
430{
431 if (!broadcast)
432 dev->event_handler = tick_handle_periodic;
433 else
434 dev->event_handler = tick_handle_periodic_broadcast;
435}
436
437#ifdef CONFIG_HOTPLUG_CPU
438/*
439 * Remove a CPU from broadcasting
440 */
441void tick_shutdown_broadcast(unsigned int cpu)
442{
443 struct clock_event_device *bc;
444 unsigned long flags;
445
446 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
447
448 bc = tick_broadcast_device.evtdev;
449 cpumask_clear_cpu(cpu, tick_broadcast_mask);
450 cpumask_clear_cpu(cpu, tick_broadcast_on);
451
452 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
453 if (bc && cpumask_empty(tick_broadcast_mask))
454 clockevents_shutdown(bc);
455 }
456
457 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
458}
459#endif
460
461void tick_suspend_broadcast(void)
462{
463 struct clock_event_device *bc;
464 unsigned long flags;
465
466 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
467
468 bc = tick_broadcast_device.evtdev;
469 if (bc)
470 clockevents_shutdown(bc);
471
472 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
473}
474
475/*
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
478 * resume hackery.
479 *
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.
482 */
483bool tick_resume_check_broadcast(void)
484{
485 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
486 return false;
487 else
488 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
489}
490
491void tick_resume_broadcast(void)
492{
493 struct clock_event_device *bc;
494 unsigned long flags;
495
496 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
497
498 bc = tick_broadcast_device.evtdev;
499
500 if (bc) {
501 clockevents_tick_resume(bc);
502
503 switch (tick_broadcast_device.mode) {
504 case TICKDEV_MODE_PERIODIC:
505 if (!cpumask_empty(tick_broadcast_mask))
506 tick_broadcast_start_periodic(bc);
507 break;
508 case TICKDEV_MODE_ONESHOT:
509 if (!cpumask_empty(tick_broadcast_mask))
510 tick_resume_broadcast_oneshot(bc);
511 break;
512 }
513 }
514 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
515}
516
517#ifdef CONFIG_TICK_ONESHOT
518
519static cpumask_var_t tick_broadcast_oneshot_mask;
520static cpumask_var_t tick_broadcast_pending_mask;
521static cpumask_var_t tick_broadcast_force_mask;
522
523/*
524 * Exposed for debugging: see timer_list.c
525 */
526struct cpumask *tick_get_broadcast_oneshot_mask(void)
527{
528 return tick_broadcast_oneshot_mask;
529}
530
531/*
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.
537 */
538int tick_check_broadcast_expired(void)
539{
540 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
541}
542
543/*
544 * Set broadcast interrupt affinity
545 */
546static void tick_broadcast_set_affinity(struct clock_event_device *bc,
547 const struct cpumask *cpumask)
548{
549 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
550 return;
551
552 if (cpumask_equal(bc->cpumask, cpumask))
553 return;
554
555 bc->cpumask = cpumask;
556 irq_set_affinity(bc->irq, bc->cpumask);
557}
558
559static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
560 ktime_t expires)
561{
562 if (!clockevent_state_oneshot(bc))
563 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
564
565 clockevents_program_event(bc, expires, 1);
566 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
567}
568
569static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
570{
571 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
572}
573
574/*
575 * Called from irq_enter() when idle was interrupted to reenable the
576 * per cpu device.
577 */
578void tick_check_oneshot_broadcast_this_cpu(void)
579{
580 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
581 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
582
583 /*
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.
587 */
588 if (td->mode == TICKDEV_MODE_ONESHOT) {
589 clockevents_switch_state(td->evtdev,
590 CLOCK_EVT_STATE_ONESHOT);
591 }
592 }
593}
594
595/*
596 * Handle oneshot mode broadcasting
597 */
598static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
599{
600 struct tick_device *td;
601 ktime_t now, next_event;
602 int cpu, next_cpu = 0;
603 bool bc_local;
604
605 raw_spin_lock(&tick_broadcast_lock);
606 dev->next_event = KTIME_MAX;
607 next_event = KTIME_MAX;
608 cpumask_clear(tmpmask);
609 now = ktime_get();
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);
615 /*
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().
619 */
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;
623 next_cpu = cpu;
624 }
625 }
626
627 /*
628 * Remove the current cpu from the pending mask. The event is
629 * delivered immediately in tick_do_broadcast() !
630 */
631 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
632
633 /* Take care of enforced broadcast requests */
634 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
635 cpumask_clear(tick_broadcast_force_mask);
636
637 /*
638 * Sanity check. Catch the case where we try to broadcast to
639 * offline cpus.
640 */
641 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
642 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
643
644 /*
645 * Wakeup the cpus which have an expired event.
646 */
647 bc_local = tick_do_broadcast(tmpmask);
648
649 /*
650 * Two reasons for reprogram:
651 *
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.
655 *
656 * - There are pending events on sleeping CPUs which were not
657 * in the event mask
658 */
659 if (next_event != KTIME_MAX)
660 tick_broadcast_set_event(dev, next_cpu, next_event);
661
662 raw_spin_unlock(&tick_broadcast_lock);
663
664 if (bc_local) {
665 td = this_cpu_ptr(&tick_cpu_device);
666 td->evtdev->event_handler(td->evtdev);
667 }
668}
669
670static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
671{
672 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
673 return 0;
674 if (bc->next_event == KTIME_MAX)
675 return 0;
676 return bc->bound_on == cpu ? -EBUSY : 0;
677}
678
679static void broadcast_shutdown_local(struct clock_event_device *bc,
680 struct clock_event_device *dev)
681{
682 /*
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.
686 */
687 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
688 if (broadcast_needs_cpu(bc, smp_processor_id()))
689 return;
690 if (dev->next_event < bc->next_event)
691 return;
692 }
693 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
694}
695
696int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
697{
698 struct clock_event_device *bc, *dev;
699 int cpu, ret = 0;
700 ktime_t now;
701
702 /*
703 * If there is no broadcast device, tell the caller not to go
704 * into deep idle.
705 */
706 if (!tick_broadcast_device.evtdev)
707 return -EBUSY;
708
709 dev = this_cpu_ptr(&tick_cpu_device)->evtdev;
710
711 raw_spin_lock(&tick_broadcast_lock);
712 bc = tick_broadcast_device.evtdev;
713 cpu = smp_processor_id();
714
715 if (state == TICK_BROADCAST_ENTER) {
716 /*
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
721 * shutdown.
722 */
723 ret = broadcast_needs_cpu(bc, cpu);
724 if (ret)
725 goto out;
726
727 /*
728 * If the broadcast device is in periodic mode, we
729 * return.
730 */
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)
734 ret = -EBUSY;
735 goto out;
736 }
737
738 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
739 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
740
741 /* Conditionally shut down the local timer. */
742 broadcast_shutdown_local(bc, dev);
743
744 /*
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
752 * idle.
753 */
754 if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
755 ret = -EBUSY;
756 } else if (dev->next_event < bc->next_event) {
757 tick_broadcast_set_event(bc, cpu, dev->next_event);
758 /*
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
763 * return busy.
764 */
765 ret = broadcast_needs_cpu(bc, cpu);
766 if (ret) {
767 cpumask_clear_cpu(cpu,
768 tick_broadcast_oneshot_mask);
769 }
770 }
771 }
772 } else {
773 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
774 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
775 /*
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.
783 */
784 if (cpumask_test_and_clear_cpu(cpu,
785 tick_broadcast_pending_mask))
786 goto out;
787
788 /*
789 * Bail out if there is no next event.
790 */
791 if (dev->next_event == KTIME_MAX)
792 goto out;
793 /*
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.
797 *
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.
802 *
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.
811 *
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.
819 *
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()
823 * nohz fixups.
824 */
825 now = ktime_get();
826 if (dev->next_event <= now) {
827 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
828 goto out;
829 }
830 /*
831 * We got woken by something else. Reprogram
832 * the cpu local timer device.
833 */
834 tick_program_event(dev->next_event, 1);
835 }
836 }
837out:
838 raw_spin_unlock(&tick_broadcast_lock);
839 return ret;
840}
841
842/*
843 * Reset the one shot broadcast for a cpu
844 *
845 * Called with tick_broadcast_lock held
846 */
847static void tick_broadcast_clear_oneshot(int cpu)
848{
849 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
850 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
851}
852
853static void tick_broadcast_init_next_event(struct cpumask *mask,
854 ktime_t expires)
855{
856 struct tick_device *td;
857 int cpu;
858
859 for_each_cpu(cpu, mask) {
860 td = &per_cpu(tick_cpu_device, cpu);
861 if (td->evtdev)
862 td->evtdev->next_event = expires;
863 }
864}
865
866/**
867 * tick_broadcast_setup_oneshot - setup the broadcast device
868 */
869void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
870{
871 int cpu = smp_processor_id();
872
873 if (!bc)
874 return;
875
876 /* Set it up only once ! */
877 if (bc->event_handler != tick_handle_oneshot_broadcast) {
878 int was_periodic = clockevent_state_periodic(bc);
879
880 bc->event_handler = tick_handle_oneshot_broadcast;
881
882 /*
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.
887 */
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);
892
893 if (was_periodic && !cpumask_empty(tmpmask)) {
894 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
895 tick_broadcast_init_next_event(tmpmask,
896 tick_next_period);
897 tick_broadcast_set_event(bc, cpu, tick_next_period);
898 } else
899 bc->next_event = KTIME_MAX;
900 } else {
901 /*
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.
907 */
908 tick_broadcast_clear_oneshot(cpu);
909 }
910}
911
912/*
913 * Select oneshot operating mode for the broadcast device
914 */
915void tick_broadcast_switch_to_oneshot(void)
916{
917 struct clock_event_device *bc;
918 unsigned long flags;
919
920 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
921
922 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
923 bc = tick_broadcast_device.evtdev;
924 if (bc)
925 tick_broadcast_setup_oneshot(bc);
926
927 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
928}
929
930#ifdef CONFIG_HOTPLUG_CPU
931void hotplug_cpu__broadcast_tick_pull(int deadcpu)
932{
933 struct clock_event_device *bc;
934 unsigned long flags;
935
936 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
937 bc = tick_broadcast_device.evtdev;
938
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);
942 }
943 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
944}
945
946/*
947 * Remove a dead CPU from broadcasting
948 */
949void tick_shutdown_broadcast_oneshot(unsigned int cpu)
950{
951 unsigned long flags;
952
953 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
954
955 /*
956 * Clear the broadcast masks for the dead cpu, but do not stop
957 * the broadcast device!
958 */
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);
962
963 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
964}
965#endif
966
967/*
968 * Check, whether the broadcast device is in one shot mode
969 */
970int tick_broadcast_oneshot_active(void)
971{
972 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
973}
974
975/*
976 * Check whether the broadcast device supports oneshot.
977 */
978bool tick_broadcast_oneshot_available(void)
979{
980 struct clock_event_device *bc = tick_broadcast_device.evtdev;
981
982 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
983}
984
985#else
986int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
987{
988 struct clock_event_device *bc = tick_broadcast_device.evtdev;
989
990 if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
991 return -EBUSY;
992
993 return 0;
994}
995#endif
996
997void __init tick_broadcast_init(void)
998{
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);
1006#endif
1007}