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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_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}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains functions which emulate a local clock-event
4 * device via a broadcast event source.
5 *
6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
9 */
10#include <linux/cpu.h>
11#include <linux/err.h>
12#include <linux/hrtimer.h>
13#include <linux/interrupt.h>
14#include <linux/percpu.h>
15#include <linux/profile.h>
16#include <linux/sched.h>
17#include <linux/smp.h>
18#include <linux/module.h>
19
20#include "tick-internal.h"
21
22/*
23 * Broadcast support for broken x86 hardware, where the local apic
24 * timer stops in C3 state.
25 */
26
27static struct tick_device tick_broadcast_device;
28static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
29static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
30static cpumask_var_t tmpmask __cpumask_var_read_mostly;
31static int tick_broadcast_forced;
32
33static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
34
35#ifdef CONFIG_TICK_ONESHOT
36static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
37static void tick_broadcast_clear_oneshot(int cpu);
38static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
39# ifdef CONFIG_HOTPLUG_CPU
40static void tick_broadcast_oneshot_offline(unsigned int cpu);
41# endif
42#else
43static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
44static inline void tick_broadcast_clear_oneshot(int cpu) { }
45static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
46# ifdef CONFIG_HOTPLUG_CPU
47static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
48# endif
49#endif
50
51/*
52 * Debugging: see timer_list.c
53 */
54struct tick_device *tick_get_broadcast_device(void)
55{
56 return &tick_broadcast_device;
57}
58
59struct cpumask *tick_get_broadcast_mask(void)
60{
61 return tick_broadcast_mask;
62}
63
64/*
65 * Start the device in periodic mode
66 */
67static void tick_broadcast_start_periodic(struct clock_event_device *bc)
68{
69 if (bc)
70 tick_setup_periodic(bc, 1);
71}
72
73/*
74 * Check, if the device can be utilized as broadcast device:
75 */
76static bool tick_check_broadcast_device(struct clock_event_device *curdev,
77 struct clock_event_device *newdev)
78{
79 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
80 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
81 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
82 return false;
83
84 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
85 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
86 return false;
87
88 return !curdev || newdev->rating > curdev->rating;
89}
90
91/*
92 * Conditionally install/replace broadcast device
93 */
94void tick_install_broadcast_device(struct clock_event_device *dev)
95{
96 struct clock_event_device *cur = tick_broadcast_device.evtdev;
97
98 if (!tick_check_broadcast_device(cur, dev))
99 return;
100
101 if (!try_module_get(dev->owner))
102 return;
103
104 clockevents_exchange_device(cur, dev);
105 if (cur)
106 cur->event_handler = clockevents_handle_noop;
107 tick_broadcast_device.evtdev = dev;
108 if (!cpumask_empty(tick_broadcast_mask))
109 tick_broadcast_start_periodic(dev);
110 /*
111 * Inform all cpus about this. We might be in a situation
112 * where we did not switch to oneshot mode because the per cpu
113 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
114 * of a oneshot capable broadcast device. Without that
115 * notification the systems stays stuck in periodic mode
116 * forever.
117 */
118 if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
119 tick_clock_notify();
120}
121
122/*
123 * Check, if the device is the broadcast device
124 */
125int tick_is_broadcast_device(struct clock_event_device *dev)
126{
127 return (dev && tick_broadcast_device.evtdev == dev);
128}
129
130int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
131{
132 int ret = -ENODEV;
133
134 if (tick_is_broadcast_device(dev)) {
135 raw_spin_lock(&tick_broadcast_lock);
136 ret = __clockevents_update_freq(dev, freq);
137 raw_spin_unlock(&tick_broadcast_lock);
138 }
139 return ret;
140}
141
142
143static void err_broadcast(const struct cpumask *mask)
144{
145 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
146}
147
148static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
149{
150 if (!dev->broadcast)
151 dev->broadcast = tick_broadcast;
152 if (!dev->broadcast) {
153 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
154 dev->name);
155 dev->broadcast = err_broadcast;
156 }
157}
158
159/*
160 * Check, if the device is disfunctional and a place holder, which
161 * needs to be handled by the broadcast device.
162 */
163int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
164{
165 struct clock_event_device *bc = tick_broadcast_device.evtdev;
166 unsigned long flags;
167 int ret = 0;
168
169 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
170
171 /*
172 * Devices might be registered with both periodic and oneshot
173 * mode disabled. This signals, that the device needs to be
174 * operated from the broadcast device and is a placeholder for
175 * the cpu local device.
176 */
177 if (!tick_device_is_functional(dev)) {
178 dev->event_handler = tick_handle_periodic;
179 tick_device_setup_broadcast_func(dev);
180 cpumask_set_cpu(cpu, tick_broadcast_mask);
181 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
182 tick_broadcast_start_periodic(bc);
183 else
184 tick_broadcast_setup_oneshot(bc);
185 ret = 1;
186 } else {
187 /*
188 * Clear the broadcast bit for this cpu if the
189 * device is not power state affected.
190 */
191 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
192 cpumask_clear_cpu(cpu, tick_broadcast_mask);
193 else
194 tick_device_setup_broadcast_func(dev);
195
196 /*
197 * Clear the broadcast bit if the CPU is not in
198 * periodic broadcast on state.
199 */
200 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
201 cpumask_clear_cpu(cpu, tick_broadcast_mask);
202
203 switch (tick_broadcast_device.mode) {
204 case TICKDEV_MODE_ONESHOT:
205 /*
206 * If the system is in oneshot mode we can
207 * unconditionally clear the oneshot mask bit,
208 * because the CPU is running and therefore
209 * not in an idle state which causes the power
210 * state affected device to stop. Let the
211 * caller initialize the device.
212 */
213 tick_broadcast_clear_oneshot(cpu);
214 ret = 0;
215 break;
216
217 case TICKDEV_MODE_PERIODIC:
218 /*
219 * If the system is in periodic mode, check
220 * whether the broadcast device can be
221 * switched off now.
222 */
223 if (cpumask_empty(tick_broadcast_mask) && bc)
224 clockevents_shutdown(bc);
225 /*
226 * If we kept the cpu in the broadcast mask,
227 * tell the caller to leave the per cpu device
228 * in shutdown state. The periodic interrupt
229 * is delivered by the broadcast device, if
230 * the broadcast device exists and is not
231 * hrtimer based.
232 */
233 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
234 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
235 break;
236 default:
237 break;
238 }
239 }
240 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
241 return ret;
242}
243
244#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
245int tick_receive_broadcast(void)
246{
247 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
248 struct clock_event_device *evt = td->evtdev;
249
250 if (!evt)
251 return -ENODEV;
252
253 if (!evt->event_handler)
254 return -EINVAL;
255
256 evt->event_handler(evt);
257 return 0;
258}
259#endif
260
261/*
262 * Broadcast the event to the cpus, which are set in the mask (mangled).
263 */
264static bool tick_do_broadcast(struct cpumask *mask)
265{
266 int cpu = smp_processor_id();
267 struct tick_device *td;
268 bool local = false;
269
270 /*
271 * Check, if the current cpu is in the mask
272 */
273 if (cpumask_test_cpu(cpu, mask)) {
274 struct clock_event_device *bc = tick_broadcast_device.evtdev;
275
276 cpumask_clear_cpu(cpu, mask);
277 /*
278 * We only run the local handler, if the broadcast
279 * device is not hrtimer based. Otherwise we run into
280 * a hrtimer recursion.
281 *
282 * local timer_interrupt()
283 * local_handler()
284 * expire_hrtimers()
285 * bc_handler()
286 * local_handler()
287 * expire_hrtimers()
288 */
289 local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
290 }
291
292 if (!cpumask_empty(mask)) {
293 /*
294 * It might be necessary to actually check whether the devices
295 * have different broadcast functions. For now, just use the
296 * one of the first device. This works as long as we have this
297 * misfeature only on x86 (lapic)
298 */
299 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
300 td->evtdev->broadcast(mask);
301 }
302 return local;
303}
304
305/*
306 * Periodic broadcast:
307 * - invoke the broadcast handlers
308 */
309static bool tick_do_periodic_broadcast(void)
310{
311 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
312 return tick_do_broadcast(tmpmask);
313}
314
315/*
316 * Event handler for periodic broadcast ticks
317 */
318static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
319{
320 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
321 bool bc_local;
322
323 raw_spin_lock(&tick_broadcast_lock);
324
325 /* Handle spurious interrupts gracefully */
326 if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
327 raw_spin_unlock(&tick_broadcast_lock);
328 return;
329 }
330
331 bc_local = tick_do_periodic_broadcast();
332
333 if (clockevent_state_oneshot(dev)) {
334 ktime_t next = ktime_add(dev->next_event, tick_period);
335
336 clockevents_program_event(dev, next, true);
337 }
338 raw_spin_unlock(&tick_broadcast_lock);
339
340 /*
341 * We run the handler of the local cpu after dropping
342 * tick_broadcast_lock because the handler might deadlock when
343 * trying to switch to oneshot mode.
344 */
345 if (bc_local)
346 td->evtdev->event_handler(td->evtdev);
347}
348
349/**
350 * tick_broadcast_control - Enable/disable or force broadcast mode
351 * @mode: The selected broadcast mode
352 *
353 * Called when the system enters a state where affected tick devices
354 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
355 */
356void tick_broadcast_control(enum tick_broadcast_mode mode)
357{
358 struct clock_event_device *bc, *dev;
359 struct tick_device *td;
360 int cpu, bc_stopped;
361 unsigned long flags;
362
363 /* Protects also the local clockevent device. */
364 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
365 td = this_cpu_ptr(&tick_cpu_device);
366 dev = td->evtdev;
367
368 /*
369 * Is the device not affected by the powerstate ?
370 */
371 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
372 goto out;
373
374 if (!tick_device_is_functional(dev))
375 goto out;
376
377 cpu = smp_processor_id();
378 bc = tick_broadcast_device.evtdev;
379 bc_stopped = cpumask_empty(tick_broadcast_mask);
380
381 switch (mode) {
382 case TICK_BROADCAST_FORCE:
383 tick_broadcast_forced = 1;
384 /* fall through */
385 case TICK_BROADCAST_ON:
386 cpumask_set_cpu(cpu, tick_broadcast_on);
387 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
388 /*
389 * Only shutdown the cpu local device, if:
390 *
391 * - the broadcast device exists
392 * - the broadcast device is not a hrtimer based one
393 * - the broadcast device is in periodic mode to
394 * avoid a hickup during switch to oneshot mode
395 */
396 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
397 tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
398 clockevents_shutdown(dev);
399 }
400 break;
401
402 case TICK_BROADCAST_OFF:
403 if (tick_broadcast_forced)
404 break;
405 cpumask_clear_cpu(cpu, tick_broadcast_on);
406 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
407 if (tick_broadcast_device.mode ==
408 TICKDEV_MODE_PERIODIC)
409 tick_setup_periodic(dev, 0);
410 }
411 break;
412 }
413
414 if (bc) {
415 if (cpumask_empty(tick_broadcast_mask)) {
416 if (!bc_stopped)
417 clockevents_shutdown(bc);
418 } else if (bc_stopped) {
419 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
420 tick_broadcast_start_periodic(bc);
421 else
422 tick_broadcast_setup_oneshot(bc);
423 }
424 }
425out:
426 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
427}
428EXPORT_SYMBOL_GPL(tick_broadcast_control);
429
430/*
431 * Set the periodic handler depending on broadcast on/off
432 */
433void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
434{
435 if (!broadcast)
436 dev->event_handler = tick_handle_periodic;
437 else
438 dev->event_handler = tick_handle_periodic_broadcast;
439}
440
441#ifdef CONFIG_HOTPLUG_CPU
442static void tick_shutdown_broadcast(void)
443{
444 struct clock_event_device *bc = tick_broadcast_device.evtdev;
445
446 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
447 if (bc && cpumask_empty(tick_broadcast_mask))
448 clockevents_shutdown(bc);
449 }
450}
451
452/*
453 * Remove a CPU from broadcasting
454 */
455void tick_broadcast_offline(unsigned int cpu)
456{
457 raw_spin_lock(&tick_broadcast_lock);
458 cpumask_clear_cpu(cpu, tick_broadcast_mask);
459 cpumask_clear_cpu(cpu, tick_broadcast_on);
460 tick_broadcast_oneshot_offline(cpu);
461 tick_shutdown_broadcast();
462 raw_spin_unlock(&tick_broadcast_lock);
463}
464
465#endif
466
467void tick_suspend_broadcast(void)
468{
469 struct clock_event_device *bc;
470 unsigned long flags;
471
472 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
473
474 bc = tick_broadcast_device.evtdev;
475 if (bc)
476 clockevents_shutdown(bc);
477
478 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
479}
480
481/*
482 * This is called from tick_resume_local() on a resuming CPU. That's
483 * called from the core resume function, tick_unfreeze() and the magic XEN
484 * resume hackery.
485 *
486 * In none of these cases the broadcast device mode can change and the
487 * bit of the resuming CPU in the broadcast mask is safe as well.
488 */
489bool tick_resume_check_broadcast(void)
490{
491 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
492 return false;
493 else
494 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
495}
496
497void tick_resume_broadcast(void)
498{
499 struct clock_event_device *bc;
500 unsigned long flags;
501
502 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
503
504 bc = tick_broadcast_device.evtdev;
505
506 if (bc) {
507 clockevents_tick_resume(bc);
508
509 switch (tick_broadcast_device.mode) {
510 case TICKDEV_MODE_PERIODIC:
511 if (!cpumask_empty(tick_broadcast_mask))
512 tick_broadcast_start_periodic(bc);
513 break;
514 case TICKDEV_MODE_ONESHOT:
515 if (!cpumask_empty(tick_broadcast_mask))
516 tick_resume_broadcast_oneshot(bc);
517 break;
518 }
519 }
520 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
521}
522
523#ifdef CONFIG_TICK_ONESHOT
524
525static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
526static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
527static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
528
529/*
530 * Exposed for debugging: see timer_list.c
531 */
532struct cpumask *tick_get_broadcast_oneshot_mask(void)
533{
534 return tick_broadcast_oneshot_mask;
535}
536
537/*
538 * Called before going idle with interrupts disabled. Checks whether a
539 * broadcast event from the other core is about to happen. We detected
540 * that in tick_broadcast_oneshot_control(). The callsite can use this
541 * to avoid a deep idle transition as we are about to get the
542 * broadcast IPI right away.
543 */
544int tick_check_broadcast_expired(void)
545{
546 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
547}
548
549/*
550 * Set broadcast interrupt affinity
551 */
552static void tick_broadcast_set_affinity(struct clock_event_device *bc,
553 const struct cpumask *cpumask)
554{
555 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
556 return;
557
558 if (cpumask_equal(bc->cpumask, cpumask))
559 return;
560
561 bc->cpumask = cpumask;
562 irq_set_affinity(bc->irq, bc->cpumask);
563}
564
565static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
566 ktime_t expires)
567{
568 if (!clockevent_state_oneshot(bc))
569 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
570
571 clockevents_program_event(bc, expires, 1);
572 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
573}
574
575static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
576{
577 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
578}
579
580/*
581 * Called from irq_enter() when idle was interrupted to reenable the
582 * per cpu device.
583 */
584void tick_check_oneshot_broadcast_this_cpu(void)
585{
586 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
587 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
588
589 /*
590 * We might be in the middle of switching over from
591 * periodic to oneshot. If the CPU has not yet
592 * switched over, leave the device alone.
593 */
594 if (td->mode == TICKDEV_MODE_ONESHOT) {
595 clockevents_switch_state(td->evtdev,
596 CLOCK_EVT_STATE_ONESHOT);
597 }
598 }
599}
600
601/*
602 * Handle oneshot mode broadcasting
603 */
604static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
605{
606 struct tick_device *td;
607 ktime_t now, next_event;
608 int cpu, next_cpu = 0;
609 bool bc_local;
610
611 raw_spin_lock(&tick_broadcast_lock);
612 dev->next_event = KTIME_MAX;
613 next_event = KTIME_MAX;
614 cpumask_clear(tmpmask);
615 now = ktime_get();
616 /* Find all expired events */
617 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
618 /*
619 * Required for !SMP because for_each_cpu() reports
620 * unconditionally CPU0 as set on UP kernels.
621 */
622 if (!IS_ENABLED(CONFIG_SMP) &&
623 cpumask_empty(tick_broadcast_oneshot_mask))
624 break;
625
626 td = &per_cpu(tick_cpu_device, cpu);
627 if (td->evtdev->next_event <= now) {
628 cpumask_set_cpu(cpu, tmpmask);
629 /*
630 * Mark the remote cpu in the pending mask, so
631 * it can avoid reprogramming the cpu local
632 * timer in tick_broadcast_oneshot_control().
633 */
634 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
635 } else if (td->evtdev->next_event < next_event) {
636 next_event = td->evtdev->next_event;
637 next_cpu = cpu;
638 }
639 }
640
641 /*
642 * Remove the current cpu from the pending mask. The event is
643 * delivered immediately in tick_do_broadcast() !
644 */
645 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
646
647 /* Take care of enforced broadcast requests */
648 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
649 cpumask_clear(tick_broadcast_force_mask);
650
651 /*
652 * Sanity check. Catch the case where we try to broadcast to
653 * offline cpus.
654 */
655 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
656 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
657
658 /*
659 * Wakeup the cpus which have an expired event.
660 */
661 bc_local = tick_do_broadcast(tmpmask);
662
663 /*
664 * Two reasons for reprogram:
665 *
666 * - The global event did not expire any CPU local
667 * events. This happens in dyntick mode, as the maximum PIT
668 * delta is quite small.
669 *
670 * - There are pending events on sleeping CPUs which were not
671 * in the event mask
672 */
673 if (next_event != KTIME_MAX)
674 tick_broadcast_set_event(dev, next_cpu, next_event);
675
676 raw_spin_unlock(&tick_broadcast_lock);
677
678 if (bc_local) {
679 td = this_cpu_ptr(&tick_cpu_device);
680 td->evtdev->event_handler(td->evtdev);
681 }
682}
683
684static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
685{
686 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
687 return 0;
688 if (bc->next_event == KTIME_MAX)
689 return 0;
690 return bc->bound_on == cpu ? -EBUSY : 0;
691}
692
693static void broadcast_shutdown_local(struct clock_event_device *bc,
694 struct clock_event_device *dev)
695{
696 /*
697 * For hrtimer based broadcasting we cannot shutdown the cpu
698 * local device if our own event is the first one to expire or
699 * if we own the broadcast timer.
700 */
701 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
702 if (broadcast_needs_cpu(bc, smp_processor_id()))
703 return;
704 if (dev->next_event < bc->next_event)
705 return;
706 }
707 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
708}
709
710int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
711{
712 struct clock_event_device *bc, *dev;
713 int cpu, ret = 0;
714 ktime_t now;
715
716 /*
717 * If there is no broadcast device, tell the caller not to go
718 * into deep idle.
719 */
720 if (!tick_broadcast_device.evtdev)
721 return -EBUSY;
722
723 dev = this_cpu_ptr(&tick_cpu_device)->evtdev;
724
725 raw_spin_lock(&tick_broadcast_lock);
726 bc = tick_broadcast_device.evtdev;
727 cpu = smp_processor_id();
728
729 if (state == TICK_BROADCAST_ENTER) {
730 /*
731 * If the current CPU owns the hrtimer broadcast
732 * mechanism, it cannot go deep idle and we do not add
733 * the CPU to the broadcast mask. We don't have to go
734 * through the EXIT path as the local timer is not
735 * shutdown.
736 */
737 ret = broadcast_needs_cpu(bc, cpu);
738 if (ret)
739 goto out;
740
741 /*
742 * If the broadcast device is in periodic mode, we
743 * return.
744 */
745 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
746 /* If it is a hrtimer based broadcast, return busy */
747 if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
748 ret = -EBUSY;
749 goto out;
750 }
751
752 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
753 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
754
755 /* Conditionally shut down the local timer. */
756 broadcast_shutdown_local(bc, dev);
757
758 /*
759 * We only reprogram the broadcast timer if we
760 * did not mark ourself in the force mask and
761 * if the cpu local event is earlier than the
762 * broadcast event. If the current CPU is in
763 * the force mask, then we are going to be
764 * woken by the IPI right away; we return
765 * busy, so the CPU does not try to go deep
766 * idle.
767 */
768 if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
769 ret = -EBUSY;
770 } else if (dev->next_event < bc->next_event) {
771 tick_broadcast_set_event(bc, cpu, dev->next_event);
772 /*
773 * In case of hrtimer broadcasts the
774 * programming might have moved the
775 * timer to this cpu. If yes, remove
776 * us from the broadcast mask and
777 * return busy.
778 */
779 ret = broadcast_needs_cpu(bc, cpu);
780 if (ret) {
781 cpumask_clear_cpu(cpu,
782 tick_broadcast_oneshot_mask);
783 }
784 }
785 }
786 } else {
787 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
788 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
789 /*
790 * The cpu which was handling the broadcast
791 * timer marked this cpu in the broadcast
792 * pending mask and fired the broadcast
793 * IPI. So we are going to handle the expired
794 * event anyway via the broadcast IPI
795 * handler. No need to reprogram the timer
796 * with an already expired event.
797 */
798 if (cpumask_test_and_clear_cpu(cpu,
799 tick_broadcast_pending_mask))
800 goto out;
801
802 /*
803 * Bail out if there is no next event.
804 */
805 if (dev->next_event == KTIME_MAX)
806 goto out;
807 /*
808 * If the pending bit is not set, then we are
809 * either the CPU handling the broadcast
810 * interrupt or we got woken by something else.
811 *
812 * We are no longer in the broadcast mask, so
813 * if the cpu local expiry time is already
814 * reached, we would reprogram the cpu local
815 * timer with an already expired event.
816 *
817 * This can lead to a ping-pong when we return
818 * to idle and therefore rearm the broadcast
819 * timer before the cpu local timer was able
820 * to fire. This happens because the forced
821 * reprogramming makes sure that the event
822 * will happen in the future and depending on
823 * the min_delta setting this might be far
824 * enough out that the ping-pong starts.
825 *
826 * If the cpu local next_event has expired
827 * then we know that the broadcast timer
828 * next_event has expired as well and
829 * broadcast is about to be handled. So we
830 * avoid reprogramming and enforce that the
831 * broadcast handler, which did not run yet,
832 * will invoke the cpu local handler.
833 *
834 * We cannot call the handler directly from
835 * here, because we might be in a NOHZ phase
836 * and we did not go through the irq_enter()
837 * nohz fixups.
838 */
839 now = ktime_get();
840 if (dev->next_event <= now) {
841 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
842 goto out;
843 }
844 /*
845 * We got woken by something else. Reprogram
846 * the cpu local timer device.
847 */
848 tick_program_event(dev->next_event, 1);
849 }
850 }
851out:
852 raw_spin_unlock(&tick_broadcast_lock);
853 return ret;
854}
855
856/*
857 * Reset the one shot broadcast for a cpu
858 *
859 * Called with tick_broadcast_lock held
860 */
861static void tick_broadcast_clear_oneshot(int cpu)
862{
863 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
864 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
865}
866
867static void tick_broadcast_init_next_event(struct cpumask *mask,
868 ktime_t expires)
869{
870 struct tick_device *td;
871 int cpu;
872
873 for_each_cpu(cpu, mask) {
874 td = &per_cpu(tick_cpu_device, cpu);
875 if (td->evtdev)
876 td->evtdev->next_event = expires;
877 }
878}
879
880/**
881 * tick_broadcast_setup_oneshot - setup the broadcast device
882 */
883static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
884{
885 int cpu = smp_processor_id();
886
887 if (!bc)
888 return;
889
890 /* Set it up only once ! */
891 if (bc->event_handler != tick_handle_oneshot_broadcast) {
892 int was_periodic = clockevent_state_periodic(bc);
893
894 bc->event_handler = tick_handle_oneshot_broadcast;
895
896 /*
897 * We must be careful here. There might be other CPUs
898 * waiting for periodic broadcast. We need to set the
899 * oneshot_mask bits for those and program the
900 * broadcast device to fire.
901 */
902 cpumask_copy(tmpmask, tick_broadcast_mask);
903 cpumask_clear_cpu(cpu, tmpmask);
904 cpumask_or(tick_broadcast_oneshot_mask,
905 tick_broadcast_oneshot_mask, tmpmask);
906
907 if (was_periodic && !cpumask_empty(tmpmask)) {
908 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
909 tick_broadcast_init_next_event(tmpmask,
910 tick_next_period);
911 tick_broadcast_set_event(bc, cpu, tick_next_period);
912 } else
913 bc->next_event = KTIME_MAX;
914 } else {
915 /*
916 * The first cpu which switches to oneshot mode sets
917 * the bit for all other cpus which are in the general
918 * (periodic) broadcast mask. So the bit is set and
919 * would prevent the first broadcast enter after this
920 * to program the bc device.
921 */
922 tick_broadcast_clear_oneshot(cpu);
923 }
924}
925
926/*
927 * Select oneshot operating mode for the broadcast device
928 */
929void tick_broadcast_switch_to_oneshot(void)
930{
931 struct clock_event_device *bc;
932 unsigned long flags;
933
934 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
935
936 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
937 bc = tick_broadcast_device.evtdev;
938 if (bc)
939 tick_broadcast_setup_oneshot(bc);
940
941 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
942}
943
944#ifdef CONFIG_HOTPLUG_CPU
945void hotplug_cpu__broadcast_tick_pull(int deadcpu)
946{
947 struct clock_event_device *bc;
948 unsigned long flags;
949
950 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
951 bc = tick_broadcast_device.evtdev;
952
953 if (bc && broadcast_needs_cpu(bc, deadcpu)) {
954 /* This moves the broadcast assignment to this CPU: */
955 clockevents_program_event(bc, bc->next_event, 1);
956 }
957 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
958}
959
960/*
961 * Remove a dying CPU from broadcasting
962 */
963static void tick_broadcast_oneshot_offline(unsigned int cpu)
964{
965 /*
966 * Clear the broadcast masks for the dead cpu, but do not stop
967 * the broadcast device!
968 */
969 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
970 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
971 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
972}
973#endif
974
975/*
976 * Check, whether the broadcast device is in one shot mode
977 */
978int tick_broadcast_oneshot_active(void)
979{
980 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
981}
982
983/*
984 * Check whether the broadcast device supports oneshot.
985 */
986bool tick_broadcast_oneshot_available(void)
987{
988 struct clock_event_device *bc = tick_broadcast_device.evtdev;
989
990 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
991}
992
993#else
994int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
995{
996 struct clock_event_device *bc = tick_broadcast_device.evtdev;
997
998 if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
999 return -EBUSY;
1000
1001 return 0;
1002}
1003#endif
1004
1005void __init tick_broadcast_init(void)
1006{
1007 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1008 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1009 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1010#ifdef CONFIG_TICK_ONESHOT
1011 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1012 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1013 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
1014#endif
1015}