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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 __cpumask_var_read_mostly;
33static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
34static cpumask_var_t tmpmask __cpumask_var_read_mostly;
35static int tick_broadcast_forced;
36
37static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
38
39#ifdef CONFIG_TICK_ONESHOT
40static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
41static void tick_broadcast_clear_oneshot(int cpu);
42static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
43#else
44static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
45static inline void tick_broadcast_clear_oneshot(int cpu) { }
46static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
47#endif
48
49/*
50 * Debugging: see timer_list.c
51 */
52struct tick_device *tick_get_broadcast_device(void)
53{
54 return &tick_broadcast_device;
55}
56
57struct cpumask *tick_get_broadcast_mask(void)
58{
59 return tick_broadcast_mask;
60}
61
62/*
63 * Start the device in periodic mode
64 */
65static void tick_broadcast_start_periodic(struct clock_event_device *bc)
66{
67 if (bc)
68 tick_setup_periodic(bc, 1);
69}
70
71/*
72 * Check, if the device can be utilized as broadcast device:
73 */
74static bool tick_check_broadcast_device(struct clock_event_device *curdev,
75 struct clock_event_device *newdev)
76{
77 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
78 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
79 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
80 return false;
81
82 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
83 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
84 return false;
85
86 return !curdev || newdev->rating > curdev->rating;
87}
88
89/*
90 * Conditionally install/replace broadcast device
91 */
92void tick_install_broadcast_device(struct clock_event_device *dev)
93{
94 struct clock_event_device *cur = tick_broadcast_device.evtdev;
95
96 if (!tick_check_broadcast_device(cur, dev))
97 return;
98
99 if (!try_module_get(dev->owner))
100 return;
101
102 clockevents_exchange_device(cur, dev);
103 if (cur)
104 cur->event_handler = clockevents_handle_noop;
105 tick_broadcast_device.evtdev = dev;
106 if (!cpumask_empty(tick_broadcast_mask))
107 tick_broadcast_start_periodic(dev);
108 /*
109 * Inform all cpus about this. We might be in a situation
110 * where we did not switch to oneshot mode because the per cpu
111 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
112 * of a oneshot capable broadcast device. Without that
113 * notification the systems stays stuck in periodic mode
114 * forever.
115 */
116 if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
117 tick_clock_notify();
118}
119
120/*
121 * Check, if the device is the broadcast device
122 */
123int tick_is_broadcast_device(struct clock_event_device *dev)
124{
125 return (dev && tick_broadcast_device.evtdev == dev);
126}
127
128int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
129{
130 int ret = -ENODEV;
131
132 if (tick_is_broadcast_device(dev)) {
133 raw_spin_lock(&tick_broadcast_lock);
134 ret = __clockevents_update_freq(dev, freq);
135 raw_spin_unlock(&tick_broadcast_lock);
136 }
137 return ret;
138}
139
140
141static void err_broadcast(const struct cpumask *mask)
142{
143 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
144}
145
146static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
147{
148 if (!dev->broadcast)
149 dev->broadcast = tick_broadcast;
150 if (!dev->broadcast) {
151 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
152 dev->name);
153 dev->broadcast = err_broadcast;
154 }
155}
156
157/*
158 * Check, if the device is disfunctional and a place holder, which
159 * needs to be handled by the broadcast device.
160 */
161int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
162{
163 struct clock_event_device *bc = tick_broadcast_device.evtdev;
164 unsigned long flags;
165 int ret = 0;
166
167 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
168
169 /*
170 * Devices might be registered with both periodic and oneshot
171 * mode disabled. This signals, that the device needs to be
172 * operated from the broadcast device and is a placeholder for
173 * the cpu local device.
174 */
175 if (!tick_device_is_functional(dev)) {
176 dev->event_handler = tick_handle_periodic;
177 tick_device_setup_broadcast_func(dev);
178 cpumask_set_cpu(cpu, tick_broadcast_mask);
179 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
180 tick_broadcast_start_periodic(bc);
181 else
182 tick_broadcast_setup_oneshot(bc);
183 ret = 1;
184 } else {
185 /*
186 * Clear the broadcast bit for this cpu if the
187 * device is not power state affected.
188 */
189 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
190 cpumask_clear_cpu(cpu, tick_broadcast_mask);
191 else
192 tick_device_setup_broadcast_func(dev);
193
194 /*
195 * Clear the broadcast bit if the CPU is not in
196 * periodic broadcast on state.
197 */
198 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
199 cpumask_clear_cpu(cpu, tick_broadcast_mask);
200
201 switch (tick_broadcast_device.mode) {
202 case TICKDEV_MODE_ONESHOT:
203 /*
204 * If the system is in oneshot mode we can
205 * unconditionally clear the oneshot mask bit,
206 * because the CPU is running and therefore
207 * not in an idle state which causes the power
208 * state affected device to stop. Let the
209 * caller initialize the device.
210 */
211 tick_broadcast_clear_oneshot(cpu);
212 ret = 0;
213 break;
214
215 case TICKDEV_MODE_PERIODIC:
216 /*
217 * If the system is in periodic mode, check
218 * whether the broadcast device can be
219 * switched off now.
220 */
221 if (cpumask_empty(tick_broadcast_mask) && bc)
222 clockevents_shutdown(bc);
223 /*
224 * If we kept the cpu in the broadcast mask,
225 * tell the caller to leave the per cpu device
226 * in shutdown state. The periodic interrupt
227 * is delivered by the broadcast device, if
228 * the broadcast device exists and is not
229 * hrtimer based.
230 */
231 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
232 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
233 break;
234 default:
235 break;
236 }
237 }
238 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
239 return ret;
240}
241
242#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
243int tick_receive_broadcast(void)
244{
245 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
246 struct clock_event_device *evt = td->evtdev;
247
248 if (!evt)
249 return -ENODEV;
250
251 if (!evt->event_handler)
252 return -EINVAL;
253
254 evt->event_handler(evt);
255 return 0;
256}
257#endif
258
259/*
260 * Broadcast the event to the cpus, which are set in the mask (mangled).
261 */
262static bool tick_do_broadcast(struct cpumask *mask)
263{
264 int cpu = smp_processor_id();
265 struct tick_device *td;
266 bool local = false;
267
268 /*
269 * Check, if the current cpu is in the mask
270 */
271 if (cpumask_test_cpu(cpu, mask)) {
272 struct clock_event_device *bc = tick_broadcast_device.evtdev;
273
274 cpumask_clear_cpu(cpu, mask);
275 /*
276 * We only run the local handler, if the broadcast
277 * device is not hrtimer based. Otherwise we run into
278 * a hrtimer recursion.
279 *
280 * local timer_interrupt()
281 * local_handler()
282 * expire_hrtimers()
283 * bc_handler()
284 * local_handler()
285 * expire_hrtimers()
286 */
287 local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
288 }
289
290 if (!cpumask_empty(mask)) {
291 /*
292 * It might be necessary to actually check whether the devices
293 * have different broadcast functions. For now, just use the
294 * one of the first device. This works as long as we have this
295 * misfeature only on x86 (lapic)
296 */
297 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
298 td->evtdev->broadcast(mask);
299 }
300 return local;
301}
302
303/*
304 * Periodic broadcast:
305 * - invoke the broadcast handlers
306 */
307static bool tick_do_periodic_broadcast(void)
308{
309 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
310 return tick_do_broadcast(tmpmask);
311}
312
313/*
314 * Event handler for periodic broadcast ticks
315 */
316static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
317{
318 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
319 bool bc_local;
320
321 raw_spin_lock(&tick_broadcast_lock);
322
323 /* Handle spurious interrupts gracefully */
324 if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
325 raw_spin_unlock(&tick_broadcast_lock);
326 return;
327 }
328
329 bc_local = tick_do_periodic_broadcast();
330
331 if (clockevent_state_oneshot(dev)) {
332 ktime_t next = ktime_add(dev->next_event, tick_period);
333
334 clockevents_program_event(dev, next, true);
335 }
336 raw_spin_unlock(&tick_broadcast_lock);
337
338 /*
339 * We run the handler of the local cpu after dropping
340 * tick_broadcast_lock because the handler might deadlock when
341 * trying to switch to oneshot mode.
342 */
343 if (bc_local)
344 td->evtdev->event_handler(td->evtdev);
345}
346
347/**
348 * tick_broadcast_control - Enable/disable or force broadcast mode
349 * @mode: The selected broadcast mode
350 *
351 * Called when the system enters a state where affected tick devices
352 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
353 */
354void tick_broadcast_control(enum tick_broadcast_mode mode)
355{
356 struct clock_event_device *bc, *dev;
357 struct tick_device *td;
358 int cpu, bc_stopped;
359 unsigned long flags;
360
361 /* Protects also the local clockevent device. */
362 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
363 td = this_cpu_ptr(&tick_cpu_device);
364 dev = td->evtdev;
365
366 /*
367 * Is the device not affected by the powerstate ?
368 */
369 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
370 goto out;
371
372 if (!tick_device_is_functional(dev))
373 goto out;
374
375 cpu = smp_processor_id();
376 bc = tick_broadcast_device.evtdev;
377 bc_stopped = cpumask_empty(tick_broadcast_mask);
378
379 switch (mode) {
380 case TICK_BROADCAST_FORCE:
381 tick_broadcast_forced = 1;
382 case TICK_BROADCAST_ON:
383 cpumask_set_cpu(cpu, tick_broadcast_on);
384 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
385 /*
386 * Only shutdown the cpu local device, if:
387 *
388 * - the broadcast device exists
389 * - the broadcast device is not a hrtimer based one
390 * - the broadcast device is in periodic mode to
391 * avoid a hickup during switch to oneshot mode
392 */
393 if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
394 tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
395 clockevents_shutdown(dev);
396 }
397 break;
398
399 case TICK_BROADCAST_OFF:
400 if (tick_broadcast_forced)
401 break;
402 cpumask_clear_cpu(cpu, tick_broadcast_on);
403 if (!tick_device_is_functional(dev))
404 break;
405 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
406 if (tick_broadcast_device.mode ==
407 TICKDEV_MODE_PERIODIC)
408 tick_setup_periodic(dev, 0);
409 }
410 break;
411 }
412
413 if (bc) {
414 if (cpumask_empty(tick_broadcast_mask)) {
415 if (!bc_stopped)
416 clockevents_shutdown(bc);
417 } else if (bc_stopped) {
418 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
419 tick_broadcast_start_periodic(bc);
420 else
421 tick_broadcast_setup_oneshot(bc);
422 }
423 }
424out:
425 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
426}
427EXPORT_SYMBOL_GPL(tick_broadcast_control);
428
429/*
430 * Set the periodic handler depending on broadcast on/off
431 */
432void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
433{
434 if (!broadcast)
435 dev->event_handler = tick_handle_periodic;
436 else
437 dev->event_handler = tick_handle_periodic_broadcast;
438}
439
440#ifdef CONFIG_HOTPLUG_CPU
441/*
442 * Remove a CPU from broadcasting
443 */
444void tick_shutdown_broadcast(unsigned int cpu)
445{
446 struct clock_event_device *bc;
447 unsigned long flags;
448
449 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
450
451 bc = tick_broadcast_device.evtdev;
452 cpumask_clear_cpu(cpu, tick_broadcast_mask);
453 cpumask_clear_cpu(cpu, tick_broadcast_on);
454
455 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
456 if (bc && cpumask_empty(tick_broadcast_mask))
457 clockevents_shutdown(bc);
458 }
459
460 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
461}
462#endif
463
464void tick_suspend_broadcast(void)
465{
466 struct clock_event_device *bc;
467 unsigned long flags;
468
469 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
470
471 bc = tick_broadcast_device.evtdev;
472 if (bc)
473 clockevents_shutdown(bc);
474
475 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
476}
477
478/*
479 * This is called from tick_resume_local() on a resuming CPU. That's
480 * called from the core resume function, tick_unfreeze() and the magic XEN
481 * resume hackery.
482 *
483 * In none of these cases the broadcast device mode can change and the
484 * bit of the resuming CPU in the broadcast mask is safe as well.
485 */
486bool tick_resume_check_broadcast(void)
487{
488 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
489 return false;
490 else
491 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
492}
493
494void tick_resume_broadcast(void)
495{
496 struct clock_event_device *bc;
497 unsigned long flags;
498
499 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
500
501 bc = tick_broadcast_device.evtdev;
502
503 if (bc) {
504 clockevents_tick_resume(bc);
505
506 switch (tick_broadcast_device.mode) {
507 case TICKDEV_MODE_PERIODIC:
508 if (!cpumask_empty(tick_broadcast_mask))
509 tick_broadcast_start_periodic(bc);
510 break;
511 case TICKDEV_MODE_ONESHOT:
512 if (!cpumask_empty(tick_broadcast_mask))
513 tick_resume_broadcast_oneshot(bc);
514 break;
515 }
516 }
517 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
518}
519
520#ifdef CONFIG_TICK_ONESHOT
521
522static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
523static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
524static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
525
526/*
527 * Exposed for debugging: see timer_list.c
528 */
529struct cpumask *tick_get_broadcast_oneshot_mask(void)
530{
531 return tick_broadcast_oneshot_mask;
532}
533
534/*
535 * Called before going idle with interrupts disabled. Checks whether a
536 * broadcast event from the other core is about to happen. We detected
537 * that in tick_broadcast_oneshot_control(). The callsite can use this
538 * to avoid a deep idle transition as we are about to get the
539 * broadcast IPI right away.
540 */
541int tick_check_broadcast_expired(void)
542{
543 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
544}
545
546/*
547 * Set broadcast interrupt affinity
548 */
549static void tick_broadcast_set_affinity(struct clock_event_device *bc,
550 const struct cpumask *cpumask)
551{
552 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
553 return;
554
555 if (cpumask_equal(bc->cpumask, cpumask))
556 return;
557
558 bc->cpumask = cpumask;
559 irq_set_affinity(bc->irq, bc->cpumask);
560}
561
562static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
563 ktime_t expires)
564{
565 if (!clockevent_state_oneshot(bc))
566 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
567
568 clockevents_program_event(bc, expires, 1);
569 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
570}
571
572static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
573{
574 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
575}
576
577/*
578 * Called from irq_enter() when idle was interrupted to reenable the
579 * per cpu device.
580 */
581void tick_check_oneshot_broadcast_this_cpu(void)
582{
583 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
584 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
585
586 /*
587 * We might be in the middle of switching over from
588 * periodic to oneshot. If the CPU has not yet
589 * switched over, leave the device alone.
590 */
591 if (td->mode == TICKDEV_MODE_ONESHOT) {
592 clockevents_switch_state(td->evtdev,
593 CLOCK_EVT_STATE_ONESHOT);
594 }
595 }
596}
597
598/*
599 * Handle oneshot mode broadcasting
600 */
601static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
602{
603 struct tick_device *td;
604 ktime_t now, next_event;
605 int cpu, next_cpu = 0;
606 bool bc_local;
607
608 raw_spin_lock(&tick_broadcast_lock);
609 dev->next_event = KTIME_MAX;
610 next_event = KTIME_MAX;
611 cpumask_clear(tmpmask);
612 now = ktime_get();
613 /* Find all expired events */
614 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
615 /*
616 * Required for !SMP because for_each_cpu() reports
617 * unconditionally CPU0 as set on UP kernels.
618 */
619 if (!IS_ENABLED(CONFIG_SMP) &&
620 cpumask_empty(tick_broadcast_oneshot_mask))
621 break;
622
623 td = &per_cpu(tick_cpu_device, cpu);
624 if (td->evtdev->next_event <= now) {
625 cpumask_set_cpu(cpu, tmpmask);
626 /*
627 * Mark the remote cpu in the pending mask, so
628 * it can avoid reprogramming the cpu local
629 * timer in tick_broadcast_oneshot_control().
630 */
631 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
632 } else if (td->evtdev->next_event < next_event) {
633 next_event = td->evtdev->next_event;
634 next_cpu = cpu;
635 }
636 }
637
638 /*
639 * Remove the current cpu from the pending mask. The event is
640 * delivered immediately in tick_do_broadcast() !
641 */
642 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
643
644 /* Take care of enforced broadcast requests */
645 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
646 cpumask_clear(tick_broadcast_force_mask);
647
648 /*
649 * Sanity check. Catch the case where we try to broadcast to
650 * offline cpus.
651 */
652 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
653 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
654
655 /*
656 * Wakeup the cpus which have an expired event.
657 */
658 bc_local = tick_do_broadcast(tmpmask);
659
660 /*
661 * Two reasons for reprogram:
662 *
663 * - The global event did not expire any CPU local
664 * events. This happens in dyntick mode, as the maximum PIT
665 * delta is quite small.
666 *
667 * - There are pending events on sleeping CPUs which were not
668 * in the event mask
669 */
670 if (next_event != KTIME_MAX)
671 tick_broadcast_set_event(dev, next_cpu, next_event);
672
673 raw_spin_unlock(&tick_broadcast_lock);
674
675 if (bc_local) {
676 td = this_cpu_ptr(&tick_cpu_device);
677 td->evtdev->event_handler(td->evtdev);
678 }
679}
680
681static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
682{
683 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
684 return 0;
685 if (bc->next_event == KTIME_MAX)
686 return 0;
687 return bc->bound_on == cpu ? -EBUSY : 0;
688}
689
690static void broadcast_shutdown_local(struct clock_event_device *bc,
691 struct clock_event_device *dev)
692{
693 /*
694 * For hrtimer based broadcasting we cannot shutdown the cpu
695 * local device if our own event is the first one to expire or
696 * if we own the broadcast timer.
697 */
698 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
699 if (broadcast_needs_cpu(bc, smp_processor_id()))
700 return;
701 if (dev->next_event < bc->next_event)
702 return;
703 }
704 clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
705}
706
707int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
708{
709 struct clock_event_device *bc, *dev;
710 int cpu, ret = 0;
711 ktime_t now;
712
713 /*
714 * If there is no broadcast device, tell the caller not to go
715 * into deep idle.
716 */
717 if (!tick_broadcast_device.evtdev)
718 return -EBUSY;
719
720 dev = this_cpu_ptr(&tick_cpu_device)->evtdev;
721
722 raw_spin_lock(&tick_broadcast_lock);
723 bc = tick_broadcast_device.evtdev;
724 cpu = smp_processor_id();
725
726 if (state == TICK_BROADCAST_ENTER) {
727 /*
728 * If the current CPU owns the hrtimer broadcast
729 * mechanism, it cannot go deep idle and we do not add
730 * the CPU to the broadcast mask. We don't have to go
731 * through the EXIT path as the local timer is not
732 * shutdown.
733 */
734 ret = broadcast_needs_cpu(bc, cpu);
735 if (ret)
736 goto out;
737
738 /*
739 * If the broadcast device is in periodic mode, we
740 * return.
741 */
742 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
743 /* If it is a hrtimer based broadcast, return busy */
744 if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
745 ret = -EBUSY;
746 goto out;
747 }
748
749 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
750 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
751
752 /* Conditionally shut down the local timer. */
753 broadcast_shutdown_local(bc, dev);
754
755 /*
756 * We only reprogram the broadcast timer if we
757 * did not mark ourself in the force mask and
758 * if the cpu local event is earlier than the
759 * broadcast event. If the current CPU is in
760 * the force mask, then we are going to be
761 * woken by the IPI right away; we return
762 * busy, so the CPU does not try to go deep
763 * idle.
764 */
765 if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
766 ret = -EBUSY;
767 } else if (dev->next_event < bc->next_event) {
768 tick_broadcast_set_event(bc, cpu, dev->next_event);
769 /*
770 * In case of hrtimer broadcasts the
771 * programming might have moved the
772 * timer to this cpu. If yes, remove
773 * us from the broadcast mask and
774 * return busy.
775 */
776 ret = broadcast_needs_cpu(bc, cpu);
777 if (ret) {
778 cpumask_clear_cpu(cpu,
779 tick_broadcast_oneshot_mask);
780 }
781 }
782 }
783 } else {
784 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
785 clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
786 /*
787 * The cpu which was handling the broadcast
788 * timer marked this cpu in the broadcast
789 * pending mask and fired the broadcast
790 * IPI. So we are going to handle the expired
791 * event anyway via the broadcast IPI
792 * handler. No need to reprogram the timer
793 * with an already expired event.
794 */
795 if (cpumask_test_and_clear_cpu(cpu,
796 tick_broadcast_pending_mask))
797 goto out;
798
799 /*
800 * Bail out if there is no next event.
801 */
802 if (dev->next_event == KTIME_MAX)
803 goto out;
804 /*
805 * If the pending bit is not set, then we are
806 * either the CPU handling the broadcast
807 * interrupt or we got woken by something else.
808 *
809 * We are not longer in the broadcast mask, so
810 * if the cpu local expiry time is already
811 * reached, we would reprogram the cpu local
812 * timer with an already expired event.
813 *
814 * This can lead to a ping-pong when we return
815 * to idle and therefor rearm the broadcast
816 * timer before the cpu local timer was able
817 * to fire. This happens because the forced
818 * reprogramming makes sure that the event
819 * will happen in the future and depending on
820 * the min_delta setting this might be far
821 * enough out that the ping-pong starts.
822 *
823 * If the cpu local next_event has expired
824 * then we know that the broadcast timer
825 * next_event has expired as well and
826 * broadcast is about to be handled. So we
827 * avoid reprogramming and enforce that the
828 * broadcast handler, which did not run yet,
829 * will invoke the cpu local handler.
830 *
831 * We cannot call the handler directly from
832 * here, because we might be in a NOHZ phase
833 * and we did not go through the irq_enter()
834 * nohz fixups.
835 */
836 now = ktime_get();
837 if (dev->next_event <= now) {
838 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
839 goto out;
840 }
841 /*
842 * We got woken by something else. Reprogram
843 * the cpu local timer device.
844 */
845 tick_program_event(dev->next_event, 1);
846 }
847 }
848out:
849 raw_spin_unlock(&tick_broadcast_lock);
850 return ret;
851}
852
853/*
854 * Reset the one shot broadcast for a cpu
855 *
856 * Called with tick_broadcast_lock held
857 */
858static void tick_broadcast_clear_oneshot(int cpu)
859{
860 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
861 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
862}
863
864static void tick_broadcast_init_next_event(struct cpumask *mask,
865 ktime_t expires)
866{
867 struct tick_device *td;
868 int cpu;
869
870 for_each_cpu(cpu, mask) {
871 td = &per_cpu(tick_cpu_device, cpu);
872 if (td->evtdev)
873 td->evtdev->next_event = expires;
874 }
875}
876
877/**
878 * tick_broadcast_setup_oneshot - setup the broadcast device
879 */
880static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
881{
882 int cpu = smp_processor_id();
883
884 if (!bc)
885 return;
886
887 /* Set it up only once ! */
888 if (bc->event_handler != tick_handle_oneshot_broadcast) {
889 int was_periodic = clockevent_state_periodic(bc);
890
891 bc->event_handler = tick_handle_oneshot_broadcast;
892
893 /*
894 * We must be careful here. There might be other CPUs
895 * waiting for periodic broadcast. We need to set the
896 * oneshot_mask bits for those and program the
897 * broadcast device to fire.
898 */
899 cpumask_copy(tmpmask, tick_broadcast_mask);
900 cpumask_clear_cpu(cpu, tmpmask);
901 cpumask_or(tick_broadcast_oneshot_mask,
902 tick_broadcast_oneshot_mask, tmpmask);
903
904 if (was_periodic && !cpumask_empty(tmpmask)) {
905 clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
906 tick_broadcast_init_next_event(tmpmask,
907 tick_next_period);
908 tick_broadcast_set_event(bc, cpu, tick_next_period);
909 } else
910 bc->next_event = KTIME_MAX;
911 } else {
912 /*
913 * The first cpu which switches to oneshot mode sets
914 * the bit for all other cpus which are in the general
915 * (periodic) broadcast mask. So the bit is set and
916 * would prevent the first broadcast enter after this
917 * to program the bc device.
918 */
919 tick_broadcast_clear_oneshot(cpu);
920 }
921}
922
923/*
924 * Select oneshot operating mode for the broadcast device
925 */
926void tick_broadcast_switch_to_oneshot(void)
927{
928 struct clock_event_device *bc;
929 unsigned long flags;
930
931 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
932
933 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
934 bc = tick_broadcast_device.evtdev;
935 if (bc)
936 tick_broadcast_setup_oneshot(bc);
937
938 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
939}
940
941#ifdef CONFIG_HOTPLUG_CPU
942void hotplug_cpu__broadcast_tick_pull(int deadcpu)
943{
944 struct clock_event_device *bc;
945 unsigned long flags;
946
947 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
948 bc = tick_broadcast_device.evtdev;
949
950 if (bc && broadcast_needs_cpu(bc, deadcpu)) {
951 /* This moves the broadcast assignment to this CPU: */
952 clockevents_program_event(bc, bc->next_event, 1);
953 }
954 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
955}
956
957/*
958 * Remove a dead CPU from broadcasting
959 */
960void tick_shutdown_broadcast_oneshot(unsigned int cpu)
961{
962 unsigned long flags;
963
964 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
965
966 /*
967 * Clear the broadcast masks for the dead cpu, but do not stop
968 * the broadcast device!
969 */
970 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
971 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
972 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
973
974 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
975}
976#endif
977
978/*
979 * Check, whether the broadcast device is in one shot mode
980 */
981int tick_broadcast_oneshot_active(void)
982{
983 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
984}
985
986/*
987 * Check whether the broadcast device supports oneshot.
988 */
989bool tick_broadcast_oneshot_available(void)
990{
991 struct clock_event_device *bc = tick_broadcast_device.evtdev;
992
993 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
994}
995
996#else
997int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
998{
999 struct clock_event_device *bc = tick_broadcast_device.evtdev;
1000
1001 if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1002 return -EBUSY;
1003
1004 return 0;
1005}
1006#endif
1007
1008void __init tick_broadcast_init(void)
1009{
1010 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1011 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1012 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1013#ifdef CONFIG_TICK_ONESHOT
1014 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1015 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1016 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
1017#endif
1018}
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 fallthrough;
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}