summaryrefslogtreecommitdiff
path: root/kernel/time/tick-broadcast.c
blob: b4843099a8da74ad79903e8ea9d59b260006f277 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains functions which emulate a local clock-event
 * device via a broadcast event source.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/module.h>

#include "tick-internal.h"

/*
 * Broadcast support for broken x86 hardware, where the local apic
 * timer stops in C3 state.
 */

static struct tick_device tick_broadcast_device;
static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
static cpumask_var_t tmpmask __cpumask_var_read_mostly;
static int tick_broadcast_forced;

static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);

#ifdef CONFIG_TICK_ONESHOT
static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);

static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);
static void tick_broadcast_clear_oneshot(int cpu);
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
# ifdef CONFIG_HOTPLUG_CPU
static void tick_broadcast_oneshot_offline(unsigned int cpu);
# endif
#else
static inline void
tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
static inline void tick_broadcast_clear_oneshot(int cpu) { }
static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
# ifdef CONFIG_HOTPLUG_CPU
static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
# endif
#endif

/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_broadcast_device(void)
{
	return &tick_broadcast_device;
}

struct cpumask *tick_get_broadcast_mask(void)
{
	return tick_broadcast_mask;
}

static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);

const struct clock_event_device *tick_get_wakeup_device(int cpu)
{
	return tick_get_oneshot_wakeup_device(cpu);
}

/*
 * Start the device in periodic mode
 */
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
	if (bc)
		tick_setup_periodic(bc, 1);
}

/*
 * Check, if the device can be utilized as broadcast device:
 */
static bool tick_check_broadcast_device(struct clock_event_device *curdev,
					struct clock_event_device *newdev)
{
	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
		return false;

	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
		return false;

	return !curdev || newdev->rating > curdev->rating;
}

#ifdef CONFIG_TICK_ONESHOT
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
	return per_cpu(tick_oneshot_wakeup_device, cpu);
}

static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
{
	/*
	 * If we woke up early and the tick was reprogrammed in the
	 * meantime then this may be spurious but harmless.
	 */
	tick_receive_broadcast();
}

static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
					   int cpu)
{
	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);

	if (!newdev)
		goto set_device;

	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
		 return false;

	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
		return false;

	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
		return false;

	if (curdev && newdev->rating <= curdev->rating)
		return false;

	if (!try_module_get(newdev->owner))
		return false;

	newdev->event_handler = tick_oneshot_wakeup_handler;
set_device:
	clockevents_exchange_device(curdev, newdev);
	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
	return true;
}
#else
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
	return NULL;
}

static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
					   int cpu)
{
	return false;
}
#endif

/*
 * Conditionally install/replace broadcast device
 */
void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
{
	struct clock_event_device *cur = tick_broadcast_device.evtdev;

	if (tick_set_oneshot_wakeup_device(dev, cpu))
		return;

	if (!tick_check_broadcast_device(cur, dev))
		return;

	if (!try_module_get(dev->owner))
		return;

	clockevents_exchange_device(cur, dev);
	if (cur)
		cur->event_handler = clockevents_handle_noop;
	tick_broadcast_device.evtdev = dev;
	if (!cpumask_empty(tick_broadcast_mask))
		tick_broadcast_start_periodic(dev);

	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
		return;

	/*
	 * If the system already runs in oneshot mode, switch the newly
	 * registered broadcast device to oneshot mode explicitly.
	 */
	if (tick_broadcast_oneshot_active()) {
		tick_broadcast_switch_to_oneshot();
		return;
	}

	/*
	 * Inform all cpus about this. We might be in a situation
	 * where we did not switch to oneshot mode because the per cpu
	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
	 * of a oneshot capable broadcast device. Without that
	 * notification the systems stays stuck in periodic mode
	 * forever.
	 */
	tick_clock_notify();
}

/*
 * Check, if the device is the broadcast device
 */
int tick_is_broadcast_device(struct clock_event_device *dev)
{
	return (dev && tick_broadcast_device.evtdev == dev);
}

int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
{
	int ret = -ENODEV;

	if (tick_is_broadcast_device(dev)) {
		raw_spin_lock(&tick_broadcast_lock);
		ret = __clockevents_update_freq(dev, freq);
		raw_spin_unlock(&tick_broadcast_lock);
	}
	return ret;
}


static void err_broadcast(const struct cpumask *mask)
{
	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
}

static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
{
	if (!dev->broadcast)
		dev->broadcast = tick_broadcast;
	if (!dev->broadcast) {
		pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
			     dev->name);
		dev->broadcast = err_broadcast;
	}
}

/*
 * Check, if the device is dysfunctional and a placeholder, which
 * needs to be handled by the broadcast device.
 */
int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;
	unsigned long flags;
	int ret = 0;

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

	/*
	 * Devices might be registered with both periodic and oneshot
	 * mode disabled. This signals, that the device needs to be
	 * operated from the broadcast device and is a placeholder for
	 * the cpu local device.
	 */
	if (!tick_device_is_functional(dev)) {
		dev->event_handler = tick_handle_periodic;
		tick_device_setup_broadcast_func(dev);
		cpumask_set_cpu(cpu, tick_broadcast_mask);
		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
			tick_broadcast_start_periodic(bc);
		else
			tick_broadcast_setup_oneshot(bc, false);
		ret = 1;
	} else {
		/*
		 * Clear the broadcast bit for this cpu if the
		 * device is not power state affected.
		 */
		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
			cpumask_clear_cpu(cpu, tick_broadcast_mask);
		else
			tick_device_setup_broadcast_func(dev);

		/*
		 * Clear the broadcast bit if the CPU is not in
		 * periodic broadcast on state.
		 */
		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
			cpumask_clear_cpu(cpu, tick_broadcast_mask);

		switch (tick_broadcast_device.mode) {
		case TICKDEV_MODE_ONESHOT:
			/*
			 * If the system is in oneshot mode we can
			 * unconditionally clear the oneshot mask bit,
			 * because the CPU is running and therefore
			 * not in an idle state which causes the power
			 * state affected device to stop. Let the
			 * caller initialize the device.
			 */
			tick_broadcast_clear_oneshot(cpu);
			ret = 0;
			break;

		case TICKDEV_MODE_PERIODIC:
			/*
			 * If the system is in periodic mode, check
			 * whether the broadcast device can be
			 * switched off now.
			 */
			if (cpumask_empty(tick_broadcast_mask) && bc)
				clockevents_shutdown(bc);
			/*
			 * If we kept the cpu in the broadcast mask,
			 * tell the caller to leave the per cpu device
			 * in shutdown state. The periodic interrupt
			 * is delivered by the broadcast device, if
			 * the broadcast device exists and is not
			 * hrtimer based.
			 */
			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
			break;
		default:
			break;
		}
	}
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
	return ret;
}

int tick_receive_broadcast(void)
{
	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
	struct clock_event_device *evt = td->evtdev;

	if (!evt)
		return -ENODEV;

	if (!evt->event_handler)
		return -EINVAL;

	evt->event_handler(evt);
	return 0;
}

/*
 * Broadcast the event to the cpus, which are set in the mask (mangled).
 */
static bool tick_do_broadcast(struct cpumask *mask)
{
	int cpu = smp_processor_id();
	struct tick_device *td;
	bool local = false;

	/*
	 * Check, if the current cpu is in the mask
	 */
	if (cpumask_test_cpu(cpu, mask)) {
		struct clock_event_device *bc = tick_broadcast_device.evtdev;

		cpumask_clear_cpu(cpu, mask);
		/*
		 * We only run the local handler, if the broadcast
		 * device is not hrtimer based. Otherwise we run into
		 * a hrtimer recursion.
		 *
		 * local timer_interrupt()
		 *   local_handler()
		 *     expire_hrtimers()
		 *       bc_handler()
		 *         local_handler()
		 *	     expire_hrtimers()
		 */
		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
	}

	if (!cpumask_empty(mask)) {
		/*
		 * It might be necessary to actually check whether the devices
		 * have different broadcast functions. For now, just use the
		 * one of the first device. This works as long as we have this
		 * misfeature only on x86 (lapic)
		 */
		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
		td->evtdev->broadcast(mask);
	}
	return local;
}

/*
 * Periodic broadcast:
 * - invoke the broadcast handlers
 */
static bool tick_do_periodic_broadcast(void)
{
	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
	return tick_do_broadcast(tmpmask);
}

/*
 * Event handler for periodic broadcast ticks
 */
static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
{
	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
	bool bc_local;

	raw_spin_lock(&tick_broadcast_lock);

	/* Handle spurious interrupts gracefully */
	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
		raw_spin_unlock(&tick_broadcast_lock);
		return;
	}

	bc_local = tick_do_periodic_broadcast();

	if (clockevent_state_oneshot(dev)) {
		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);

		clockevents_program_event(dev, next, true);
	}
	raw_spin_unlock(&tick_broadcast_lock);

	/*
	 * We run the handler of the local cpu after dropping
	 * tick_broadcast_lock because the handler might deadlock when
	 * trying to switch to oneshot mode.
	 */
	if (bc_local)
		td->evtdev->event_handler(td->evtdev);
}

/**
 * tick_broadcast_control - Enable/disable or force broadcast mode
 * @mode:	The selected broadcast mode
 *
 * Called when the system enters a state where affected tick devices
 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
 */
void tick_broadcast_control(enum tick_broadcast_mode mode)
{
	struct clock_event_device *bc, *dev;
	struct tick_device *td;
	int cpu, bc_stopped;
	unsigned long flags;

	/* Protects also the local clockevent device. */
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
	td = this_cpu_ptr(&tick_cpu_device);
	dev = td->evtdev;

	/*
	 * Is the device not affected by the powerstate ?
	 */
	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
		goto out;

	if (!tick_device_is_functional(dev))
		goto out;

	cpu = smp_processor_id();
	bc = tick_broadcast_device.evtdev;
	bc_stopped = cpumask_empty(tick_broadcast_mask);

	switch (mode) {
	case TICK_BROADCAST_FORCE:
		tick_broadcast_forced = 1;
		fallthrough;
	case TICK_BROADCAST_ON:
		cpumask_set_cpu(cpu, tick_broadcast_on);
		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
			/*
			 * Only shutdown the cpu local device, if:
			 *
			 * - the broadcast device exists
			 * - the broadcast device is not a hrtimer based one
			 * - the broadcast device is in periodic mode to
			 *   avoid a hiccup during switch to oneshot mode
			 */
			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
				clockevents_shutdown(dev);
		}
		break;

	case TICK_BROADCAST_OFF:
		if (tick_broadcast_forced)
			break;
		cpumask_clear_cpu(cpu, tick_broadcast_on);
		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
			if (tick_broadcast_device.mode ==
			    TICKDEV_MODE_PERIODIC)
				tick_setup_periodic(dev, 0);
		}
		break;
	}

	if (bc) {
		if (cpumask_empty(tick_broadcast_mask)) {
			if (!bc_stopped)
				clockevents_shutdown(bc);
		} else if (bc_stopped) {
			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
				tick_broadcast_start_periodic(bc);
			else
				tick_broadcast_setup_oneshot(bc, false);
		}
	}
out:
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
EXPORT_SYMBOL_GPL(tick_broadcast_control);

/*
 * Set the periodic handler depending on broadcast on/off
 */
void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
{
	if (!broadcast)
		dev->event_handler = tick_handle_periodic;
	else
		dev->event_handler = tick_handle_periodic_broadcast;
}

#ifdef CONFIG_HOTPLUG_CPU
static void tick_shutdown_broadcast(void)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;

	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
		if (bc && cpumask_empty(tick_broadcast_mask))
			clockevents_shutdown(bc);
	}
}

/*
 * Remove a CPU from broadcasting
 */
void tick_broadcast_offline(unsigned int cpu)
{
	raw_spin_lock(&tick_broadcast_lock);
	cpumask_clear_cpu(cpu, tick_broadcast_mask);
	cpumask_clear_cpu(cpu, tick_broadcast_on);
	tick_broadcast_oneshot_offline(cpu);
	tick_shutdown_broadcast();
	raw_spin_unlock(&tick_broadcast_lock);
}

#endif

void tick_suspend_broadcast(void)
{
	struct clock_event_device *bc;
	unsigned long flags;

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

	bc = tick_broadcast_device.evtdev;
	if (bc)
		clockevents_shutdown(bc);

	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

/*
 * This is called from tick_resume_local() on a resuming CPU. That's
 * called from the core resume function, tick_unfreeze() and the magic XEN
 * resume hackery.
 *
 * In none of these cases the broadcast device mode can change and the
 * bit of the resuming CPU in the broadcast mask is safe as well.
 */
bool tick_resume_check_broadcast(void)
{
	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
		return false;
	else
		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
}

void tick_resume_broadcast(void)
{
	struct clock_event_device *bc;
	unsigned long flags;

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

	bc = tick_broadcast_device.evtdev;

	if (bc) {
		clockevents_tick_resume(bc);

		switch (tick_broadcast_device.mode) {
		case TICKDEV_MODE_PERIODIC:
			if (!cpumask_empty(tick_broadcast_mask))
				tick_broadcast_start_periodic(bc);
			break;
		case TICKDEV_MODE_ONESHOT:
			if (!cpumask_empty(tick_broadcast_mask))
				tick_resume_broadcast_oneshot(bc);
			break;
		}
	}
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

#ifdef CONFIG_TICK_ONESHOT

static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;

/*
 * Exposed for debugging: see timer_list.c
 */
struct cpumask *tick_get_broadcast_oneshot_mask(void)
{
	return tick_broadcast_oneshot_mask;
}

/*
 * Called before going idle with interrupts disabled. Checks whether a
 * broadcast event from the other core is about to happen. We detected
 * that in tick_broadcast_oneshot_control(). The callsite can use this
 * to avoid a deep idle transition as we are about to get the
 * broadcast IPI right away.
 */
noinstr int tick_check_broadcast_expired(void)
{
#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
#else
	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
#endif
}

/*
 * Set broadcast interrupt affinity
 */
static void tick_broadcast_set_affinity(struct clock_event_device *bc,
					const struct cpumask *cpumask)
{
	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
		return;

	if (cpumask_equal(bc->cpumask, cpumask))
		return;

	bc->cpumask = cpumask;
	irq_set_affinity(bc->irq, bc->cpumask);
}

static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
				     ktime_t expires)
{
	if (!clockevent_state_oneshot(bc))
		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);

	clockevents_program_event(bc, expires, 1);
	tick_broadcast_set_affinity(bc, cpumask_of(cpu));
}

static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
}

/*
 * Called from irq_enter() when idle was interrupted to reenable the
 * per cpu device.
 */
void tick_check_oneshot_broadcast_this_cpu(void)
{
	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);

		/*
		 * We might be in the middle of switching over from
		 * periodic to oneshot. If the CPU has not yet
		 * switched over, leave the device alone.
		 */
		if (td->mode == TICKDEV_MODE_ONESHOT) {
			clockevents_switch_state(td->evtdev,
					      CLOCK_EVT_STATE_ONESHOT);
		}
	}
}

/*
 * Handle oneshot mode broadcasting
 */
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
{
	struct tick_device *td;
	ktime_t now, next_event;
	int cpu, next_cpu = 0;
	bool bc_local;

	raw_spin_lock(&tick_broadcast_lock);
	dev->next_event = KTIME_MAX;
	next_event = KTIME_MAX;
	cpumask_clear(tmpmask);
	now = ktime_get();
	/* Find all expired events */
	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
		/*
		 * Required for !SMP because for_each_cpu() reports
		 * unconditionally CPU0 as set on UP kernels.
		 */
		if (!IS_ENABLED(CONFIG_SMP) &&
		    cpumask_empty(tick_broadcast_oneshot_mask))
			break;

		td = &per_cpu(tick_cpu_device, cpu);
		if (td->evtdev->next_event <= now) {
			cpumask_set_cpu(cpu, tmpmask);
			/*
			 * Mark the remote cpu in the pending mask, so
			 * it can avoid reprogramming the cpu local
			 * timer in tick_broadcast_oneshot_control().
			 */
			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
		} else if (td->evtdev->next_event < next_event) {
			next_event = td->evtdev->next_event;
			next_cpu = cpu;
		}
	}

	/*
	 * Remove the current cpu from the pending mask. The event is
	 * delivered immediately in tick_do_broadcast() !
	 */
	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);

	/* Take care of enforced broadcast requests */
	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
	cpumask_clear(tick_broadcast_force_mask);

	/*
	 * Sanity check. Catch the case where we try to broadcast to
	 * offline cpus.
	 */
	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
		cpumask_and(tmpmask, tmpmask, cpu_online_mask);

	/*
	 * Wakeup the cpus which have an expired event.
	 */
	bc_local = tick_do_broadcast(tmpmask);

	/*
	 * Two reasons for reprogram:
	 *
	 * - The global event did not expire any CPU local
	 * events. This happens in dyntick mode, as the maximum PIT
	 * delta is quite small.
	 *
	 * - There are pending events on sleeping CPUs which were not
	 * in the event mask
	 */
	if (next_event != KTIME_MAX)
		tick_broadcast_set_event(dev, next_cpu, next_event);

	raw_spin_unlock(&tick_broadcast_lock);

	if (bc_local) {
		td = this_cpu_ptr(&tick_cpu_device);
		td->evtdev->event_handler(td->evtdev);
	}
}

static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
{
	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
		return 0;
	if (bc->next_event == KTIME_MAX)
		return 0;
	return bc->bound_on == cpu ? -EBUSY : 0;
}

static void broadcast_shutdown_local(struct clock_event_device *bc,
				     struct clock_event_device *dev)
{
	/*
	 * For hrtimer based broadcasting we cannot shutdown the cpu
	 * local device if our own event is the first one to expire or
	 * if we own the broadcast timer.
	 */
	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
		if (broadcast_needs_cpu(bc, smp_processor_id()))
			return;
		if (dev->next_event < bc->next_event)
			return;
	}
	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
}

static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
					     struct tick_device *td,
					     int cpu)
{
	struct clock_event_device *bc, *dev = td->evtdev;
	int ret = 0;
	ktime_t now;

	raw_spin_lock(&tick_broadcast_lock);
	bc = tick_broadcast_device.evtdev;

	if (state == TICK_BROADCAST_ENTER) {
		/*
		 * If the current CPU owns the hrtimer broadcast
		 * mechanism, it cannot go deep idle and we do not add
		 * the CPU to the broadcast mask. We don't have to go
		 * through the EXIT path as the local timer is not
		 * shutdown.
		 */
		ret = broadcast_needs_cpu(bc, cpu);
		if (ret)
			goto out;

		/*
		 * If the broadcast device is in periodic mode, we
		 * return.
		 */
		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
			/* If it is a hrtimer based broadcast, return busy */
			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
				ret = -EBUSY;
			goto out;
		}

		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));

			/* Conditionally shut down the local timer. */
			broadcast_shutdown_local(bc, dev);

			/*
			 * We only reprogram the broadcast timer if we
			 * did not mark ourself in the force mask and
			 * if the cpu local event is earlier than the
			 * broadcast event. If the current CPU is in
			 * the force mask, then we are going to be
			 * woken by the IPI right away; we return
			 * busy, so the CPU does not try to go deep
			 * idle.
			 */
			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
				ret = -EBUSY;
			} else if (dev->next_event < bc->next_event) {
				tick_broadcast_set_event(bc, cpu, dev->next_event);
				/*
				 * In case of hrtimer broadcasts the
				 * programming might have moved the
				 * timer to this cpu. If yes, remove
				 * us from the broadcast mask and
				 * return busy.
				 */
				ret = broadcast_needs_cpu(bc, cpu);
				if (ret) {
					cpumask_clear_cpu(cpu,
						tick_broadcast_oneshot_mask);
				}
			}
		}
	} else {
		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
			/*
			 * The cpu which was handling the broadcast
			 * timer marked this cpu in the broadcast
			 * pending mask and fired the broadcast
			 * IPI. So we are going to handle the expired
			 * event anyway via the broadcast IPI
			 * handler. No need to reprogram the timer
			 * with an already expired event.
			 */
			if (cpumask_test_and_clear_cpu(cpu,
				       tick_broadcast_pending_mask))
				goto out;

			/*
			 * Bail out if there is no next event.
			 */
			if (dev->next_event == KTIME_MAX)
				goto out;
			/*
			 * If the pending bit is not set, then we are
			 * either the CPU handling the broadcast
			 * interrupt or we got woken by something else.
			 *
			 * We are no longer in the broadcast mask, so
			 * if the cpu local expiry time is already
			 * reached, we would reprogram the cpu local
			 * timer with an already expired event.
			 *
			 * This can lead to a ping-pong when we return
			 * to idle and therefore rearm the broadcast
			 * timer before the cpu local timer was able
			 * to fire. This happens because the forced
			 * reprogramming makes sure that the event
			 * will happen in the future and depending on
			 * the min_delta setting this might be far
			 * enough out that the ping-pong starts.
			 *
			 * If the cpu local next_event has expired
			 * then we know that the broadcast timer
			 * next_event has expired as well and
			 * broadcast is about to be handled. So we
			 * avoid reprogramming and enforce that the
			 * broadcast handler, which did not run yet,
			 * will invoke the cpu local handler.
			 *
			 * We cannot call the handler directly from
			 * here, because we might be in a NOHZ phase
			 * and we did not go through the irq_enter()
			 * nohz fixups.
			 */
			now = ktime_get();
			if (dev->next_event <= now) {
				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
				goto out;
			}
			/*
			 * We got woken by something else. Reprogram
			 * the cpu local timer device.
			 */
			tick_program_event(dev->next_event, 1);
		}
	}
out:
	raw_spin_unlock(&tick_broadcast_lock);
	return ret;
}

static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
				       struct tick_device *td,
				       int cpu)
{
	struct clock_event_device *dev, *wd;

	dev = td->evtdev;
	if (td->mode != TICKDEV_MODE_ONESHOT)
		return -EINVAL;

	wd = tick_get_oneshot_wakeup_device(cpu);
	if (!wd)
		return -ENODEV;

	switch (state) {
	case TICK_BROADCAST_ENTER:
		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
		clockevents_program_event(wd, dev->next_event, 1);
		break;
	case TICK_BROADCAST_EXIT:
		/* We may have transitioned to oneshot mode while idle */
		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
			return -ENODEV;
	}

	return 0;
}

int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
	int cpu = smp_processor_id();

	if (!tick_oneshot_wakeup_control(state, td, cpu))
		return 0;

	if (tick_broadcast_device.evtdev)
		return ___tick_broadcast_oneshot_control(state, td, cpu);

	/*
	 * If there is no broadcast or wakeup device, tell the caller not
	 * to go into deep idle.
	 */
	return -EBUSY;
}

/*
 * Reset the one shot broadcast for a cpu
 *
 * Called with tick_broadcast_lock held
 */
static void tick_broadcast_clear_oneshot(int cpu)
{
	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
}

static void tick_broadcast_init_next_event(struct cpumask *mask,
					   ktime_t expires)
{
	struct tick_device *td;
	int cpu;

	for_each_cpu(cpu, mask) {
		td = &per_cpu(tick_cpu_device, cpu);
		if (td->evtdev)
			td->evtdev->next_event = expires;
	}
}

static inline ktime_t tick_get_next_period(void)
{
	ktime_t next;

	/*
	 * Protect against concurrent updates (store /load tearing on
	 * 32bit). It does not matter if the time is already in the
	 * past. The broadcast device which is about to be programmed will
	 * fire in any case.
	 */
	raw_spin_lock(&jiffies_lock);
	next = tick_next_period;
	raw_spin_unlock(&jiffies_lock);
	return next;
}

/**
 * tick_broadcast_setup_oneshot - setup the broadcast device
 */
static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
					 bool from_periodic)
{
	int cpu = smp_processor_id();
	ktime_t nexttick = 0;

	if (!bc)
		return;

	/*
	 * When the broadcast device was switched to oneshot by the first
	 * CPU handling the NOHZ change, the other CPUs will reach this
	 * code via hrtimer_run_queues() -> tick_check_oneshot_change()
	 * too. Set up the broadcast device only once!
	 */
	if (bc->event_handler == tick_handle_oneshot_broadcast) {
		/*
		 * The CPU which switched from periodic to oneshot mode
		 * set the broadcast oneshot bit for all other CPUs which
		 * are in the general (periodic) broadcast mask to ensure
		 * that CPUs which wait for the periodic broadcast are
		 * woken up.
		 *
		 * Clear the bit for the local CPU as the set bit would
		 * prevent the first tick_broadcast_enter() after this CPU
		 * switched to oneshot state to program the broadcast
		 * device.
		 *
		 * This code can also be reached via tick_broadcast_control(),
		 * but this cannot avoid the tick_broadcast_clear_oneshot()
		 * as that would break the periodic to oneshot transition of
		 * secondary CPUs. But that's harmless as the below only
		 * clears already cleared bits.
		 */
		tick_broadcast_clear_oneshot(cpu);
		return;
	}


	bc->event_handler = tick_handle_oneshot_broadcast;
	bc->next_event = KTIME_MAX;

	/*
	 * When the tick mode is switched from periodic to oneshot it must
	 * be ensured that CPUs which are waiting for periodic broadcast
	 * get their wake-up at the next tick.  This is achieved by ORing
	 * tick_broadcast_mask into tick_broadcast_oneshot_mask.
	 *
	 * For other callers, e.g. broadcast device replacement,
	 * tick_broadcast_oneshot_mask must not be touched as this would
	 * set bits for CPUs which are already NOHZ, but not idle. Their
	 * next tick_broadcast_enter() would observe the bit set and fail
	 * to update the expiry time and the broadcast event device.
	 */
	if (from_periodic) {
		cpumask_copy(tmpmask, tick_broadcast_mask);
		/* Remove the local CPU as it is obviously not idle */
		cpumask_clear_cpu(cpu, tmpmask);
		cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);

		/*
		 * Ensure that the oneshot broadcast handler will wake the
		 * CPUs which are still waiting for periodic broadcast.
		 */
		nexttick = tick_get_next_period();
		tick_broadcast_init_next_event(tmpmask, nexttick);

		/*
		 * If the underlying broadcast clock event device is
		 * already in oneshot state, then there is nothing to do.
		 * The device was already armed for the next tick
		 * in tick_handle_broadcast_periodic()
		 */
		if (clockevent_state_oneshot(bc))
			return;
	}

	/*
	 * When switching from periodic to oneshot mode arm the broadcast
	 * device for the next tick.
	 *
	 * If the broadcast device has been replaced in oneshot mode and
	 * the oneshot broadcast mask is not empty, then arm it to expire
	 * immediately in order to reevaluate the next expiring timer.
	 * @nexttick is 0 and therefore in the past which will cause the
	 * clockevent code to force an event.
	 *
	 * For both cases the programming can be avoided when the oneshot
	 * broadcast mask is empty.
	 *
	 * tick_broadcast_set_event() implicitly switches the broadcast
	 * device to oneshot state.
	 */
	if (!cpumask_empty(tick_broadcast_oneshot_mask))
		tick_broadcast_set_event(bc, cpu, nexttick);
}

/*
 * Select oneshot operating mode for the broadcast device
 */
void tick_broadcast_switch_to_oneshot(void)
{
	struct clock_event_device *bc;
	enum tick_device_mode oldmode;
	unsigned long flags;

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

	oldmode = tick_broadcast_device.mode;
	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
	bc = tick_broadcast_device.evtdev;
	if (bc)
		tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);

	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

#ifdef CONFIG_HOTPLUG_CPU
void hotplug_cpu__broadcast_tick_pull(int deadcpu)
{
	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
	struct clock_event_device *bc;
	unsigned long flags;

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
	bc = tick_broadcast_device.evtdev;

	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
		/*
		 * If the broadcast force bit of the current CPU is set,
		 * then the current CPU has not yet reprogrammed the local
		 * timer device to avoid a ping-pong race. See
		 * ___tick_broadcast_oneshot_control().
		 *
		 * If the broadcast device is hrtimer based then
		 * programming the broadcast event below does not have any
		 * effect because the local clockevent device is not
		 * running and not programmed because the broadcast event
		 * is not earlier than the pending event of the local clock
		 * event device. As a consequence all CPUs waiting for a
		 * broadcast event are stuck forever.
		 *
		 * Detect this condition and reprogram the cpu local timer
		 * device to avoid the starvation.
		 */
		if (tick_check_broadcast_expired()) {
			cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask);
			tick_program_event(td->evtdev->next_event, 1);
		}

		/* This moves the broadcast assignment to this CPU: */
		clockevents_program_event(bc, bc->next_event, 1);
	}
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

/*
 * Remove a dying CPU from broadcasting
 */
static void tick_broadcast_oneshot_offline(unsigned int cpu)
{
	if (tick_get_oneshot_wakeup_device(cpu))
		tick_set_oneshot_wakeup_device(NULL, cpu);

	/*
	 * Clear the broadcast masks for the dead cpu, but do not stop
	 * the broadcast device!
	 */
	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
}
#endif

/*
 * Check, whether the broadcast device is in one shot mode
 */
int tick_broadcast_oneshot_active(void)
{
	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
}

/*
 * Check whether the broadcast device supports oneshot.
 */
bool tick_broadcast_oneshot_available(void)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;

	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
}

#else
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;

	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
		return -EBUSY;

	return 0;
}
#endif

void __init tick_broadcast_init(void)
{
	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
#ifdef CONFIG_TICK_ONESHOT
	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
#endif
}