Loading...
1/*
2 * linux/kernel/time/tick-broadcast.c
3 *
4 * This file contains functions which emulate a local clock-event
5 * device via a broadcast event source.
6 *
7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
10 *
11 * This code is licenced under the GPL version 2. For details see
12 * kernel-base/COPYING.
13 */
14#include <linux/cpu.h>
15#include <linux/err.h>
16#include <linux/hrtimer.h>
17#include <linux/interrupt.h>
18#include <linux/percpu.h>
19#include <linux/profile.h>
20#include <linux/sched.h>
21#include <linux/smp.h>
22#include <linux/module.h>
23
24#include "tick-internal.h"
25
26/*
27 * Broadcast support for broken x86 hardware, where the local apic
28 * timer stops in C3 state.
29 */
30
31static struct tick_device tick_broadcast_device;
32static cpumask_var_t tick_broadcast_mask;
33static cpumask_var_t tick_broadcast_on;
34static cpumask_var_t tmpmask;
35static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
36static int tick_broadcast_force;
37
38#ifdef CONFIG_TICK_ONESHOT
39static void tick_broadcast_clear_oneshot(int cpu);
40#else
41static inline void tick_broadcast_clear_oneshot(int cpu) { }
42#endif
43
44/*
45 * Debugging: see timer_list.c
46 */
47struct tick_device *tick_get_broadcast_device(void)
48{
49 return &tick_broadcast_device;
50}
51
52struct cpumask *tick_get_broadcast_mask(void)
53{
54 return tick_broadcast_mask;
55}
56
57/*
58 * Start the device in periodic mode
59 */
60static void tick_broadcast_start_periodic(struct clock_event_device *bc)
61{
62 if (bc)
63 tick_setup_periodic(bc, 1);
64}
65
66/*
67 * Check, if the device can be utilized as broadcast device:
68 */
69static bool tick_check_broadcast_device(struct clock_event_device *curdev,
70 struct clock_event_device *newdev)
71{
72 if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
73 (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
74 (newdev->features & CLOCK_EVT_FEAT_C3STOP))
75 return false;
76
77 if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
78 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
79 return false;
80
81 return !curdev || newdev->rating > curdev->rating;
82}
83
84/*
85 * Conditionally install/replace broadcast device
86 */
87void tick_install_broadcast_device(struct clock_event_device *dev)
88{
89 struct clock_event_device *cur = tick_broadcast_device.evtdev;
90
91 if (!tick_check_broadcast_device(cur, dev))
92 return;
93
94 if (!try_module_get(dev->owner))
95 return;
96
97 clockevents_exchange_device(cur, dev);
98 if (cur)
99 cur->event_handler = clockevents_handle_noop;
100 tick_broadcast_device.evtdev = dev;
101 if (!cpumask_empty(tick_broadcast_mask))
102 tick_broadcast_start_periodic(dev);
103 /*
104 * Inform all cpus about this. We might be in a situation
105 * where we did not switch to oneshot mode because the per cpu
106 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
107 * of a oneshot capable broadcast device. Without that
108 * notification the systems stays stuck in periodic mode
109 * forever.
110 */
111 if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
112 tick_clock_notify();
113}
114
115/*
116 * Check, if the device is the broadcast device
117 */
118int tick_is_broadcast_device(struct clock_event_device *dev)
119{
120 return (dev && tick_broadcast_device.evtdev == dev);
121}
122
123int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
124{
125 int ret = -ENODEV;
126
127 if (tick_is_broadcast_device(dev)) {
128 raw_spin_lock(&tick_broadcast_lock);
129 ret = __clockevents_update_freq(dev, freq);
130 raw_spin_unlock(&tick_broadcast_lock);
131 }
132 return ret;
133}
134
135
136static void err_broadcast(const struct cpumask *mask)
137{
138 pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
139}
140
141static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
142{
143 if (!dev->broadcast)
144 dev->broadcast = tick_broadcast;
145 if (!dev->broadcast) {
146 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
147 dev->name);
148 dev->broadcast = err_broadcast;
149 }
150}
151
152/*
153 * Check, if the device is disfunctional and a place holder, which
154 * needs to be handled by the broadcast device.
155 */
156int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
157{
158 struct clock_event_device *bc = tick_broadcast_device.evtdev;
159 unsigned long flags;
160 int ret;
161
162 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
163
164 /*
165 * Devices might be registered with both periodic and oneshot
166 * mode disabled. This signals, that the device needs to be
167 * operated from the broadcast device and is a placeholder for
168 * the cpu local device.
169 */
170 if (!tick_device_is_functional(dev)) {
171 dev->event_handler = tick_handle_periodic;
172 tick_device_setup_broadcast_func(dev);
173 cpumask_set_cpu(cpu, tick_broadcast_mask);
174 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
175 tick_broadcast_start_periodic(bc);
176 else
177 tick_broadcast_setup_oneshot(bc);
178 ret = 1;
179 } else {
180 /*
181 * Clear the broadcast bit for this cpu if the
182 * device is not power state affected.
183 */
184 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
185 cpumask_clear_cpu(cpu, tick_broadcast_mask);
186 else
187 tick_device_setup_broadcast_func(dev);
188
189 /*
190 * Clear the broadcast bit if the CPU is not in
191 * periodic broadcast on state.
192 */
193 if (!cpumask_test_cpu(cpu, tick_broadcast_on))
194 cpumask_clear_cpu(cpu, tick_broadcast_mask);
195
196 switch (tick_broadcast_device.mode) {
197 case TICKDEV_MODE_ONESHOT:
198 /*
199 * If the system is in oneshot mode we can
200 * unconditionally clear the oneshot mask bit,
201 * because the CPU is running and therefore
202 * not in an idle state which causes the power
203 * state affected device to stop. Let the
204 * caller initialize the device.
205 */
206 tick_broadcast_clear_oneshot(cpu);
207 ret = 0;
208 break;
209
210 case TICKDEV_MODE_PERIODIC:
211 /*
212 * If the system is in periodic mode, check
213 * whether the broadcast device can be
214 * switched off now.
215 */
216 if (cpumask_empty(tick_broadcast_mask) && bc)
217 clockevents_shutdown(bc);
218 /*
219 * If we kept the cpu in the broadcast mask,
220 * tell the caller to leave the per cpu device
221 * in shutdown state. The periodic interrupt
222 * is delivered by the broadcast device.
223 */
224 ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
225 break;
226 default:
227 /* Nothing to do */
228 ret = 0;
229 break;
230 }
231 }
232 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
233 return ret;
234}
235
236#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
237int tick_receive_broadcast(void)
238{
239 struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
240 struct clock_event_device *evt = td->evtdev;
241
242 if (!evt)
243 return -ENODEV;
244
245 if (!evt->event_handler)
246 return -EINVAL;
247
248 evt->event_handler(evt);
249 return 0;
250}
251#endif
252
253/*
254 * Broadcast the event to the cpus, which are set in the mask (mangled).
255 */
256static void tick_do_broadcast(struct cpumask *mask)
257{
258 int cpu = smp_processor_id();
259 struct tick_device *td;
260
261 /*
262 * Check, if the current cpu is in the mask
263 */
264 if (cpumask_test_cpu(cpu, mask)) {
265 cpumask_clear_cpu(cpu, mask);
266 td = &per_cpu(tick_cpu_device, cpu);
267 td->evtdev->event_handler(td->evtdev);
268 }
269
270 if (!cpumask_empty(mask)) {
271 /*
272 * It might be necessary to actually check whether the devices
273 * have different broadcast functions. For now, just use the
274 * one of the first device. This works as long as we have this
275 * misfeature only on x86 (lapic)
276 */
277 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
278 td->evtdev->broadcast(mask);
279 }
280}
281
282/*
283 * Periodic broadcast:
284 * - invoke the broadcast handlers
285 */
286static void tick_do_periodic_broadcast(void)
287{
288 cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
289 tick_do_broadcast(tmpmask);
290}
291
292/*
293 * Event handler for periodic broadcast ticks
294 */
295static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
296{
297 ktime_t next;
298
299 raw_spin_lock(&tick_broadcast_lock);
300
301 tick_do_periodic_broadcast();
302
303 /*
304 * The device is in periodic mode. No reprogramming necessary:
305 */
306 if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
307 goto unlock;
308
309 /*
310 * Setup the next period for devices, which do not have
311 * periodic mode. We read dev->next_event first and add to it
312 * when the event already expired. clockevents_program_event()
313 * sets dev->next_event only when the event is really
314 * programmed to the device.
315 */
316 for (next = dev->next_event; ;) {
317 next = ktime_add(next, tick_period);
318
319 if (!clockevents_program_event(dev, next, false))
320 goto unlock;
321 tick_do_periodic_broadcast();
322 }
323unlock:
324 raw_spin_unlock(&tick_broadcast_lock);
325}
326
327/*
328 * Powerstate information: The system enters/leaves a state, where
329 * affected devices might stop
330 */
331static void tick_do_broadcast_on_off(unsigned long *reason)
332{
333 struct clock_event_device *bc, *dev;
334 struct tick_device *td;
335 unsigned long flags;
336 int cpu, bc_stopped;
337
338 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
339
340 cpu = smp_processor_id();
341 td = &per_cpu(tick_cpu_device, cpu);
342 dev = td->evtdev;
343 bc = tick_broadcast_device.evtdev;
344
345 /*
346 * Is the device not affected by the powerstate ?
347 */
348 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
349 goto out;
350
351 if (!tick_device_is_functional(dev))
352 goto out;
353
354 bc_stopped = cpumask_empty(tick_broadcast_mask);
355
356 switch (*reason) {
357 case CLOCK_EVT_NOTIFY_BROADCAST_ON:
358 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
359 cpumask_set_cpu(cpu, tick_broadcast_on);
360 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
361 if (tick_broadcast_device.mode ==
362 TICKDEV_MODE_PERIODIC)
363 clockevents_shutdown(dev);
364 }
365 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
366 tick_broadcast_force = 1;
367 break;
368 case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
369 if (tick_broadcast_force)
370 break;
371 cpumask_clear_cpu(cpu, tick_broadcast_on);
372 if (!tick_device_is_functional(dev))
373 break;
374 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
375 if (tick_broadcast_device.mode ==
376 TICKDEV_MODE_PERIODIC)
377 tick_setup_periodic(dev, 0);
378 }
379 break;
380 }
381
382 if (cpumask_empty(tick_broadcast_mask)) {
383 if (!bc_stopped)
384 clockevents_shutdown(bc);
385 } else if (bc_stopped) {
386 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
387 tick_broadcast_start_periodic(bc);
388 else
389 tick_broadcast_setup_oneshot(bc);
390 }
391out:
392 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
393}
394
395/*
396 * Powerstate information: The system enters/leaves a state, where
397 * affected devices might stop.
398 */
399void tick_broadcast_on_off(unsigned long reason, int *oncpu)
400{
401 if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
402 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
403 "offline CPU #%d\n", *oncpu);
404 else
405 tick_do_broadcast_on_off(&reason);
406}
407
408/*
409 * Set the periodic handler depending on broadcast on/off
410 */
411void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
412{
413 if (!broadcast)
414 dev->event_handler = tick_handle_periodic;
415 else
416 dev->event_handler = tick_handle_periodic_broadcast;
417}
418
419/*
420 * Remove a CPU from broadcasting
421 */
422void tick_shutdown_broadcast(unsigned int *cpup)
423{
424 struct clock_event_device *bc;
425 unsigned long flags;
426 unsigned int cpu = *cpup;
427
428 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
429
430 bc = tick_broadcast_device.evtdev;
431 cpumask_clear_cpu(cpu, tick_broadcast_mask);
432 cpumask_clear_cpu(cpu, tick_broadcast_on);
433
434 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
435 if (bc && cpumask_empty(tick_broadcast_mask))
436 clockevents_shutdown(bc);
437 }
438
439 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
440}
441
442void tick_suspend_broadcast(void)
443{
444 struct clock_event_device *bc;
445 unsigned long flags;
446
447 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
448
449 bc = tick_broadcast_device.evtdev;
450 if (bc)
451 clockevents_shutdown(bc);
452
453 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
454}
455
456int tick_resume_broadcast(void)
457{
458 struct clock_event_device *bc;
459 unsigned long flags;
460 int broadcast = 0;
461
462 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
463
464 bc = tick_broadcast_device.evtdev;
465
466 if (bc) {
467 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
468
469 switch (tick_broadcast_device.mode) {
470 case TICKDEV_MODE_PERIODIC:
471 if (!cpumask_empty(tick_broadcast_mask))
472 tick_broadcast_start_periodic(bc);
473 broadcast = cpumask_test_cpu(smp_processor_id(),
474 tick_broadcast_mask);
475 break;
476 case TICKDEV_MODE_ONESHOT:
477 if (!cpumask_empty(tick_broadcast_mask))
478 broadcast = tick_resume_broadcast_oneshot(bc);
479 break;
480 }
481 }
482 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
483
484 return broadcast;
485}
486
487
488#ifdef CONFIG_TICK_ONESHOT
489
490static cpumask_var_t tick_broadcast_oneshot_mask;
491static cpumask_var_t tick_broadcast_pending_mask;
492static cpumask_var_t tick_broadcast_force_mask;
493
494/*
495 * Exposed for debugging: see timer_list.c
496 */
497struct cpumask *tick_get_broadcast_oneshot_mask(void)
498{
499 return tick_broadcast_oneshot_mask;
500}
501
502/*
503 * Called before going idle with interrupts disabled. Checks whether a
504 * broadcast event from the other core is about to happen. We detected
505 * that in tick_broadcast_oneshot_control(). The callsite can use this
506 * to avoid a deep idle transition as we are about to get the
507 * broadcast IPI right away.
508 */
509int tick_check_broadcast_expired(void)
510{
511 return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
512}
513
514/*
515 * Set broadcast interrupt affinity
516 */
517static void tick_broadcast_set_affinity(struct clock_event_device *bc,
518 const struct cpumask *cpumask)
519{
520 if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
521 return;
522
523 if (cpumask_equal(bc->cpumask, cpumask))
524 return;
525
526 bc->cpumask = cpumask;
527 irq_set_affinity(bc->irq, bc->cpumask);
528}
529
530static int tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
531 ktime_t expires, int force)
532{
533 int ret;
534
535 if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
536 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
537
538 ret = clockevents_program_event(bc, expires, force);
539 if (!ret)
540 tick_broadcast_set_affinity(bc, cpumask_of(cpu));
541 return ret;
542}
543
544int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
545{
546 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
547 return 0;
548}
549
550/*
551 * Called from irq_enter() when idle was interrupted to reenable the
552 * per cpu device.
553 */
554void tick_check_oneshot_broadcast_this_cpu(void)
555{
556 if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
557 struct tick_device *td = &__get_cpu_var(tick_cpu_device);
558
559 /*
560 * We might be in the middle of switching over from
561 * periodic to oneshot. If the CPU has not yet
562 * switched over, leave the device alone.
563 */
564 if (td->mode == TICKDEV_MODE_ONESHOT) {
565 clockevents_set_mode(td->evtdev,
566 CLOCK_EVT_MODE_ONESHOT);
567 }
568 }
569}
570
571/*
572 * Handle oneshot mode broadcasting
573 */
574static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
575{
576 struct tick_device *td;
577 ktime_t now, next_event;
578 int cpu, next_cpu = 0;
579
580 raw_spin_lock(&tick_broadcast_lock);
581again:
582 dev->next_event.tv64 = KTIME_MAX;
583 next_event.tv64 = KTIME_MAX;
584 cpumask_clear(tmpmask);
585 now = ktime_get();
586 /* Find all expired events */
587 for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
588 td = &per_cpu(tick_cpu_device, cpu);
589 if (td->evtdev->next_event.tv64 <= now.tv64) {
590 cpumask_set_cpu(cpu, tmpmask);
591 /*
592 * Mark the remote cpu in the pending mask, so
593 * it can avoid reprogramming the cpu local
594 * timer in tick_broadcast_oneshot_control().
595 */
596 cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
597 } else if (td->evtdev->next_event.tv64 < next_event.tv64) {
598 next_event.tv64 = td->evtdev->next_event.tv64;
599 next_cpu = cpu;
600 }
601 }
602
603 /*
604 * Remove the current cpu from the pending mask. The event is
605 * delivered immediately in tick_do_broadcast() !
606 */
607 cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
608
609 /* Take care of enforced broadcast requests */
610 cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
611 cpumask_clear(tick_broadcast_force_mask);
612
613 /*
614 * Sanity check. Catch the case where we try to broadcast to
615 * offline cpus.
616 */
617 if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
618 cpumask_and(tmpmask, tmpmask, cpu_online_mask);
619
620 /*
621 * Wakeup the cpus which have an expired event.
622 */
623 tick_do_broadcast(tmpmask);
624
625 /*
626 * Two reasons for reprogram:
627 *
628 * - The global event did not expire any CPU local
629 * events. This happens in dyntick mode, as the maximum PIT
630 * delta is quite small.
631 *
632 * - There are pending events on sleeping CPUs which were not
633 * in the event mask
634 */
635 if (next_event.tv64 != KTIME_MAX) {
636 /*
637 * Rearm the broadcast device. If event expired,
638 * repeat the above
639 */
640 if (tick_broadcast_set_event(dev, next_cpu, next_event, 0))
641 goto again;
642 }
643 raw_spin_unlock(&tick_broadcast_lock);
644}
645
646static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
647{
648 if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
649 return 0;
650 if (bc->next_event.tv64 == KTIME_MAX)
651 return 0;
652 return bc->bound_on == cpu ? -EBUSY : 0;
653}
654
655static void broadcast_shutdown_local(struct clock_event_device *bc,
656 struct clock_event_device *dev)
657{
658 /*
659 * For hrtimer based broadcasting we cannot shutdown the cpu
660 * local device if our own event is the first one to expire or
661 * if we own the broadcast timer.
662 */
663 if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
664 if (broadcast_needs_cpu(bc, smp_processor_id()))
665 return;
666 if (dev->next_event.tv64 < bc->next_event.tv64)
667 return;
668 }
669 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
670}
671
672static void broadcast_move_bc(int deadcpu)
673{
674 struct clock_event_device *bc = tick_broadcast_device.evtdev;
675
676 if (!bc || !broadcast_needs_cpu(bc, deadcpu))
677 return;
678 /* This moves the broadcast assignment to this cpu */
679 clockevents_program_event(bc, bc->next_event, 1);
680}
681
682/*
683 * Powerstate information: The system enters/leaves a state, where
684 * affected devices might stop
685 * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
686 */
687int tick_broadcast_oneshot_control(unsigned long reason)
688{
689 struct clock_event_device *bc, *dev;
690 struct tick_device *td;
691 unsigned long flags;
692 ktime_t now;
693 int cpu, ret = 0;
694
695 /*
696 * Periodic mode does not care about the enter/exit of power
697 * states
698 */
699 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
700 return 0;
701
702 /*
703 * We are called with preemtion disabled from the depth of the
704 * idle code, so we can't be moved away.
705 */
706 cpu = smp_processor_id();
707 td = &per_cpu(tick_cpu_device, cpu);
708 dev = td->evtdev;
709
710 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
711 return 0;
712
713 bc = tick_broadcast_device.evtdev;
714
715 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
716 if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
717 if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
718 WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
719 broadcast_shutdown_local(bc, dev);
720 /*
721 * We only reprogram the broadcast timer if we
722 * did not mark ourself in the force mask and
723 * if the cpu local event is earlier than the
724 * broadcast event. If the current CPU is in
725 * the force mask, then we are going to be
726 * woken by the IPI right away.
727 */
728 if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
729 dev->next_event.tv64 < bc->next_event.tv64)
730 tick_broadcast_set_event(bc, cpu, dev->next_event, 1);
731 }
732 /*
733 * If the current CPU owns the hrtimer broadcast
734 * mechanism, it cannot go deep idle and we remove the
735 * CPU from the broadcast mask. We don't have to go
736 * through the EXIT path as the local timer is not
737 * shutdown.
738 */
739 ret = broadcast_needs_cpu(bc, cpu);
740 if (ret)
741 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
742 } else {
743 if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
744 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
745 /*
746 * The cpu which was handling the broadcast
747 * timer marked this cpu in the broadcast
748 * pending mask and fired the broadcast
749 * IPI. So we are going to handle the expired
750 * event anyway via the broadcast IPI
751 * handler. No need to reprogram the timer
752 * with an already expired event.
753 */
754 if (cpumask_test_and_clear_cpu(cpu,
755 tick_broadcast_pending_mask))
756 goto out;
757
758 /*
759 * Bail out if there is no next event.
760 */
761 if (dev->next_event.tv64 == KTIME_MAX)
762 goto out;
763 /*
764 * If the pending bit is not set, then we are
765 * either the CPU handling the broadcast
766 * interrupt or we got woken by something else.
767 *
768 * We are not longer in the broadcast mask, so
769 * if the cpu local expiry time is already
770 * reached, we would reprogram the cpu local
771 * timer with an already expired event.
772 *
773 * This can lead to a ping-pong when we return
774 * to idle and therefor rearm the broadcast
775 * timer before the cpu local timer was able
776 * to fire. This happens because the forced
777 * reprogramming makes sure that the event
778 * will happen in the future and depending on
779 * the min_delta setting this might be far
780 * enough out that the ping-pong starts.
781 *
782 * If the cpu local next_event has expired
783 * then we know that the broadcast timer
784 * next_event has expired as well and
785 * broadcast is about to be handled. So we
786 * avoid reprogramming and enforce that the
787 * broadcast handler, which did not run yet,
788 * will invoke the cpu local handler.
789 *
790 * We cannot call the handler directly from
791 * here, because we might be in a NOHZ phase
792 * and we did not go through the irq_enter()
793 * nohz fixups.
794 */
795 now = ktime_get();
796 if (dev->next_event.tv64 <= now.tv64) {
797 cpumask_set_cpu(cpu, tick_broadcast_force_mask);
798 goto out;
799 }
800 /*
801 * We got woken by something else. Reprogram
802 * the cpu local timer device.
803 */
804 tick_program_event(dev->next_event, 1);
805 }
806 }
807out:
808 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
809 return ret;
810}
811
812/*
813 * Reset the one shot broadcast for a cpu
814 *
815 * Called with tick_broadcast_lock held
816 */
817static void tick_broadcast_clear_oneshot(int cpu)
818{
819 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
820 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
821}
822
823static void tick_broadcast_init_next_event(struct cpumask *mask,
824 ktime_t expires)
825{
826 struct tick_device *td;
827 int cpu;
828
829 for_each_cpu(cpu, mask) {
830 td = &per_cpu(tick_cpu_device, cpu);
831 if (td->evtdev)
832 td->evtdev->next_event = expires;
833 }
834}
835
836/**
837 * tick_broadcast_setup_oneshot - setup the broadcast device
838 */
839void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
840{
841 int cpu = smp_processor_id();
842
843 /* Set it up only once ! */
844 if (bc->event_handler != tick_handle_oneshot_broadcast) {
845 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
846
847 bc->event_handler = tick_handle_oneshot_broadcast;
848
849 /*
850 * We must be careful here. There might be other CPUs
851 * waiting for periodic broadcast. We need to set the
852 * oneshot_mask bits for those and program the
853 * broadcast device to fire.
854 */
855 cpumask_copy(tmpmask, tick_broadcast_mask);
856 cpumask_clear_cpu(cpu, tmpmask);
857 cpumask_or(tick_broadcast_oneshot_mask,
858 tick_broadcast_oneshot_mask, tmpmask);
859
860 if (was_periodic && !cpumask_empty(tmpmask)) {
861 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
862 tick_broadcast_init_next_event(tmpmask,
863 tick_next_period);
864 tick_broadcast_set_event(bc, cpu, tick_next_period, 1);
865 } else
866 bc->next_event.tv64 = KTIME_MAX;
867 } else {
868 /*
869 * The first cpu which switches to oneshot mode sets
870 * the bit for all other cpus which are in the general
871 * (periodic) broadcast mask. So the bit is set and
872 * would prevent the first broadcast enter after this
873 * to program the bc device.
874 */
875 tick_broadcast_clear_oneshot(cpu);
876 }
877}
878
879/*
880 * Select oneshot operating mode for the broadcast device
881 */
882void tick_broadcast_switch_to_oneshot(void)
883{
884 struct clock_event_device *bc;
885 unsigned long flags;
886
887 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
888
889 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
890 bc = tick_broadcast_device.evtdev;
891 if (bc)
892 tick_broadcast_setup_oneshot(bc);
893
894 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
895}
896
897
898/*
899 * Remove a dead CPU from broadcasting
900 */
901void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
902{
903 unsigned long flags;
904 unsigned int cpu = *cpup;
905
906 raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
907
908 /*
909 * Clear the broadcast masks for the dead cpu, but do not stop
910 * the broadcast device!
911 */
912 cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
913 cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
914 cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
915
916 broadcast_move_bc(cpu);
917
918 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
919}
920
921/*
922 * Check, whether the broadcast device is in one shot mode
923 */
924int tick_broadcast_oneshot_active(void)
925{
926 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
927}
928
929/*
930 * Check whether the broadcast device supports oneshot.
931 */
932bool tick_broadcast_oneshot_available(void)
933{
934 struct clock_event_device *bc = tick_broadcast_device.evtdev;
935
936 return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
937}
938
939#endif
940
941void __init tick_broadcast_init(void)
942{
943 zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
944 zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
945 zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
946#ifdef CONFIG_TICK_ONESHOT
947 zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
948 zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
949 zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
950#endif
951}
1// 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}