summaryrefslogtreecommitdiff
path: root/kernel/sched/deadline.c
blob: 2b8cbf09d1a4add6fe837be0080a71a35f145164 (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
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
/*
 * Deadline Scheduling Class (SCHED_DEADLINE)
 *
 * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
 *
 * Tasks that periodically executes their instances for less than their
 * runtime won't miss any of their deadlines.
 * Tasks that are not periodic or sporadic or that tries to execute more
 * than their reserved bandwidth will be slowed down (and may potentially
 * miss some of their deadlines), and won't affect any other task.
 *
 * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
 *                    Juri Lelli <juri.lelli@gmail.com>,
 *                    Michael Trimarchi <michael@amarulasolutions.com>,
 *                    Fabio Checconi <fchecconi@gmail.com>
 */
#include "sched.h"

#include <linux/slab.h>

struct dl_bandwidth def_dl_bandwidth;

static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
{
	return container_of(dl_se, struct task_struct, dl);
}

static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
{
	return container_of(dl_rq, struct rq, dl);
}

static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
{
	struct task_struct *p = dl_task_of(dl_se);
	struct rq *rq = task_rq(p);

	return &rq->dl;
}

static inline int on_dl_rq(struct sched_dl_entity *dl_se)
{
	return !RB_EMPTY_NODE(&dl_se->rb_node);
}

static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
{
	struct sched_dl_entity *dl_se = &p->dl;

	return dl_rq->rb_leftmost == &dl_se->rb_node;
}

void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
{
	raw_spin_lock_init(&dl_b->dl_runtime_lock);
	dl_b->dl_period = period;
	dl_b->dl_runtime = runtime;
}

extern unsigned long to_ratio(u64 period, u64 runtime);

void init_dl_bw(struct dl_bw *dl_b)
{
	raw_spin_lock_init(&dl_b->lock);
	raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
	if (global_rt_runtime() == RUNTIME_INF)
		dl_b->bw = -1;
	else
		dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
	raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
	dl_b->total_bw = 0;
}

void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
{
	dl_rq->rb_root = RB_ROOT;

#ifdef CONFIG_SMP
	/* zero means no -deadline tasks */
	dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;

	dl_rq->dl_nr_migratory = 0;
	dl_rq->overloaded = 0;
	dl_rq->pushable_dl_tasks_root = RB_ROOT;
#else
	init_dl_bw(&dl_rq->dl_bw);
#endif
}

#ifdef CONFIG_SMP

static inline int dl_overloaded(struct rq *rq)
{
	return atomic_read(&rq->rd->dlo_count);
}

static inline void dl_set_overload(struct rq *rq)
{
	if (!rq->online)
		return;

	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
	/*
	 * Must be visible before the overload count is
	 * set (as in sched_rt.c).
	 *
	 * Matched by the barrier in pull_dl_task().
	 */
	smp_wmb();
	atomic_inc(&rq->rd->dlo_count);
}

static inline void dl_clear_overload(struct rq *rq)
{
	if (!rq->online)
		return;

	atomic_dec(&rq->rd->dlo_count);
	cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
}

static void update_dl_migration(struct dl_rq *dl_rq)
{
	if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
		if (!dl_rq->overloaded) {
			dl_set_overload(rq_of_dl_rq(dl_rq));
			dl_rq->overloaded = 1;
		}
	} else if (dl_rq->overloaded) {
		dl_clear_overload(rq_of_dl_rq(dl_rq));
		dl_rq->overloaded = 0;
	}
}

static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
	struct task_struct *p = dl_task_of(dl_se);

	if (p->nr_cpus_allowed > 1)
		dl_rq->dl_nr_migratory++;

	update_dl_migration(dl_rq);
}

static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
	struct task_struct *p = dl_task_of(dl_se);

	if (p->nr_cpus_allowed > 1)
		dl_rq->dl_nr_migratory--;

	update_dl_migration(dl_rq);
}

/*
 * The list of pushable -deadline task is not a plist, like in
 * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
 */
static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
	struct dl_rq *dl_rq = &rq->dl;
	struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
	struct rb_node *parent = NULL;
	struct task_struct *entry;
	int leftmost = 1;

	BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));

	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct task_struct,
				 pushable_dl_tasks);
		if (dl_entity_preempt(&p->dl, &entry->dl))
			link = &parent->rb_left;
		else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	if (leftmost)
		dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;

	rb_link_node(&p->pushable_dl_tasks, parent, link);
	rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
}

static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
	struct dl_rq *dl_rq = &rq->dl;

	if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
		return;

	if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
		struct rb_node *next_node;

		next_node = rb_next(&p->pushable_dl_tasks);
		dl_rq->pushable_dl_tasks_leftmost = next_node;
	}

	rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
	RB_CLEAR_NODE(&p->pushable_dl_tasks);
}

static inline int has_pushable_dl_tasks(struct rq *rq)
{
	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
}

static int push_dl_task(struct rq *rq);

static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
{
	return dl_task(prev);
}

static inline void set_post_schedule(struct rq *rq)
{
	rq->post_schedule = has_pushable_dl_tasks(rq);
}

#else

static inline
void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
}

static inline
void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
}

static inline
void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
}

static inline
void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
}

static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
{
	return false;
}

static inline int pull_dl_task(struct rq *rq)
{
	return 0;
}

static inline void set_post_schedule(struct rq *rq)
{
}
#endif /* CONFIG_SMP */

static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
				  int flags);

/*
 * We are being explicitly informed that a new instance is starting,
 * and this means that:
 *  - the absolute deadline of the entity has to be placed at
 *    current time + relative deadline;
 *  - the runtime of the entity has to be set to the maximum value.
 *
 * The capability of specifying such event is useful whenever a -deadline
 * entity wants to (try to!) synchronize its behaviour with the scheduler's
 * one, and to (try to!) reconcile itself with its own scheduling
 * parameters.
 */
static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
				       struct sched_dl_entity *pi_se)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
	struct rq *rq = rq_of_dl_rq(dl_rq);

	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);

	/*
	 * We use the regular wall clock time to set deadlines in the
	 * future; in fact, we must consider execution overheads (time
	 * spent on hardirq context, etc.).
	 */
	dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
	dl_se->runtime = pi_se->dl_runtime;
	dl_se->dl_new = 0;
}

/*
 * Pure Earliest Deadline First (EDF) scheduling does not deal with the
 * possibility of a entity lasting more than what it declared, and thus
 * exhausting its runtime.
 *
 * Here we are interested in making runtime overrun possible, but we do
 * not want a entity which is misbehaving to affect the scheduling of all
 * other entities.
 * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
 * is used, in order to confine each entity within its own bandwidth.
 *
 * This function deals exactly with that, and ensures that when the runtime
 * of a entity is replenished, its deadline is also postponed. That ensures
 * the overrunning entity can't interfere with other entity in the system and
 * can't make them miss their deadlines. Reasons why this kind of overruns
 * could happen are, typically, a entity voluntarily trying to overcome its
 * runtime, or it just underestimated it during sched_setscheduler_ex().
 */
static void replenish_dl_entity(struct sched_dl_entity *dl_se,
				struct sched_dl_entity *pi_se)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
	struct rq *rq = rq_of_dl_rq(dl_rq);

	BUG_ON(pi_se->dl_runtime <= 0);

	/*
	 * This could be the case for a !-dl task that is boosted.
	 * Just go with full inherited parameters.
	 */
	if (dl_se->dl_deadline == 0) {
		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
		dl_se->runtime = pi_se->dl_runtime;
	}

	/*
	 * We keep moving the deadline away until we get some
	 * available runtime for the entity. This ensures correct
	 * handling of situations where the runtime overrun is
	 * arbitrary large.
	 */
	while (dl_se->runtime <= 0) {
		dl_se->deadline += pi_se->dl_period;
		dl_se->runtime += pi_se->dl_runtime;
	}

	/*
	 * At this point, the deadline really should be "in
	 * the future" with respect to rq->clock. If it's
	 * not, we are, for some reason, lagging too much!
	 * Anyway, after having warn userspace abut that,
	 * we still try to keep the things running by
	 * resetting the deadline and the budget of the
	 * entity.
	 */
	if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
		printk_deferred_once("sched: DL replenish lagged to much\n");
		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
		dl_se->runtime = pi_se->dl_runtime;
	}
}

/*
 * Here we check if --at time t-- an entity (which is probably being
 * [re]activated or, in general, enqueued) can use its remaining runtime
 * and its current deadline _without_ exceeding the bandwidth it is
 * assigned (function returns true if it can't). We are in fact applying
 * one of the CBS rules: when a task wakes up, if the residual runtime
 * over residual deadline fits within the allocated bandwidth, then we
 * can keep the current (absolute) deadline and residual budget without
 * disrupting the schedulability of the system. Otherwise, we should
 * refill the runtime and set the deadline a period in the future,
 * because keeping the current (absolute) deadline of the task would
 * result in breaking guarantees promised to other tasks (refer to
 * Documentation/scheduler/sched-deadline.txt for more informations).
 *
 * This function returns true if:
 *
 *   runtime / (deadline - t) > dl_runtime / dl_period ,
 *
 * IOW we can't recycle current parameters.
 *
 * Notice that the bandwidth check is done against the period. For
 * task with deadline equal to period this is the same of using
 * dl_deadline instead of dl_period in the equation above.
 */
static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
			       struct sched_dl_entity *pi_se, u64 t)
{
	u64 left, right;

	/*
	 * left and right are the two sides of the equation above,
	 * after a bit of shuffling to use multiplications instead
	 * of divisions.
	 *
	 * Note that none of the time values involved in the two
	 * multiplications are absolute: dl_deadline and dl_runtime
	 * are the relative deadline and the maximum runtime of each
	 * instance, runtime is the runtime left for the last instance
	 * and (deadline - t), since t is rq->clock, is the time left
	 * to the (absolute) deadline. Even if overflowing the u64 type
	 * is very unlikely to occur in both cases, here we scale down
	 * as we want to avoid that risk at all. Scaling down by 10
	 * means that we reduce granularity to 1us. We are fine with it,
	 * since this is only a true/false check and, anyway, thinking
	 * of anything below microseconds resolution is actually fiction
	 * (but still we want to give the user that illusion >;).
	 */
	left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
	right = ((dl_se->deadline - t) >> DL_SCALE) *
		(pi_se->dl_runtime >> DL_SCALE);

	return dl_time_before(right, left);
}

/*
 * When a -deadline entity is queued back on the runqueue, its runtime and
 * deadline might need updating.
 *
 * The policy here is that we update the deadline of the entity only if:
 *  - the current deadline is in the past,
 *  - using the remaining runtime with the current deadline would make
 *    the entity exceed its bandwidth.
 */
static void update_dl_entity(struct sched_dl_entity *dl_se,
			     struct sched_dl_entity *pi_se)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
	struct rq *rq = rq_of_dl_rq(dl_rq);

	/*
	 * The arrival of a new instance needs special treatment, i.e.,
	 * the actual scheduling parameters have to be "renewed".
	 */
	if (dl_se->dl_new) {
		setup_new_dl_entity(dl_se, pi_se);
		return;
	}

	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
	    dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
		dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
		dl_se->runtime = pi_se->dl_runtime;
	}
}

/*
 * If the entity depleted all its runtime, and if we want it to sleep
 * while waiting for some new execution time to become available, we
 * set the bandwidth enforcement timer to the replenishment instant
 * and try to activate it.
 *
 * Notice that it is important for the caller to know if the timer
 * actually started or not (i.e., the replenishment instant is in
 * the future or in the past).
 */
static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
	struct rq *rq = rq_of_dl_rq(dl_rq);
	ktime_t now, act;
	ktime_t soft, hard;
	unsigned long range;
	s64 delta;

	if (boosted)
		return 0;
	/*
	 * We want the timer to fire at the deadline, but considering
	 * that it is actually coming from rq->clock and not from
	 * hrtimer's time base reading.
	 */
	act = ns_to_ktime(dl_se->deadline);
	now = hrtimer_cb_get_time(&dl_se->dl_timer);
	delta = ktime_to_ns(now) - rq_clock(rq);
	act = ktime_add_ns(act, delta);

	/*
	 * If the expiry time already passed, e.g., because the value
	 * chosen as the deadline is too small, don't even try to
	 * start the timer in the past!
	 */
	if (ktime_us_delta(act, now) < 0)
		return 0;

	hrtimer_set_expires(&dl_se->dl_timer, act);

	soft = hrtimer_get_softexpires(&dl_se->dl_timer);
	hard = hrtimer_get_expires(&dl_se->dl_timer);
	range = ktime_to_ns(ktime_sub(hard, soft));
	__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
				 range, HRTIMER_MODE_ABS, 0);

	return hrtimer_active(&dl_se->dl_timer);
}

/*
 * This is the bandwidth enforcement timer callback. If here, we know
 * a task is not on its dl_rq, since the fact that the timer was running
 * means the task is throttled and needs a runtime replenishment.
 *
 * However, what we actually do depends on the fact the task is active,
 * (it is on its rq) or has been removed from there by a call to
 * dequeue_task_dl(). In the former case we must issue the runtime
 * replenishment and add the task back to the dl_rq; in the latter, we just
 * do nothing but clearing dl_throttled, so that runtime and deadline
 * updating (and the queueing back to dl_rq) will be done by the
 * next call to enqueue_task_dl().
 */
static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
{
	struct sched_dl_entity *dl_se = container_of(timer,
						     struct sched_dl_entity,
						     dl_timer);
	struct task_struct *p = dl_task_of(dl_se);
	struct rq *rq;
again:
	rq = task_rq(p);
	raw_spin_lock(&rq->lock);

	if (rq != task_rq(p)) {
		/* Task was moved, retrying. */
		raw_spin_unlock(&rq->lock);
		goto again;
	}

	/*
	 * We need to take care of a possible races here. In fact, the
	 * task might have changed its scheduling policy to something
	 * different from SCHED_DEADLINE or changed its reservation
	 * parameters (through sched_setattr()).
	 */
	if (!dl_task(p) || dl_se->dl_new)
		goto unlock;

	sched_clock_tick();
	update_rq_clock(rq);
	dl_se->dl_throttled = 0;
	dl_se->dl_yielded = 0;
	if (p->on_rq) {
		enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
		if (task_has_dl_policy(rq->curr))
			check_preempt_curr_dl(rq, p, 0);
		else
			resched_task(rq->curr);
#ifdef CONFIG_SMP
		/*
		 * Queueing this task back might have overloaded rq,
		 * check if we need to kick someone away.
		 */
		if (has_pushable_dl_tasks(rq))
			push_dl_task(rq);
#endif
	}
unlock:
	raw_spin_unlock(&rq->lock);

	return HRTIMER_NORESTART;
}

void init_dl_task_timer(struct sched_dl_entity *dl_se)
{
	struct hrtimer *timer = &dl_se->dl_timer;

	if (hrtimer_active(timer)) {
		hrtimer_try_to_cancel(timer);
		return;
	}

	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	timer->function = dl_task_timer;
}

static
int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
{
	int dmiss = dl_time_before(dl_se->deadline, rq_clock(rq));
	int rorun = dl_se->runtime <= 0;

	if (!rorun && !dmiss)
		return 0;

	/*
	 * If we are beyond our current deadline and we are still
	 * executing, then we have already used some of the runtime of
	 * the next instance. Thus, if we do not account that, we are
	 * stealing bandwidth from the system at each deadline miss!
	 */
	if (dmiss) {
		dl_se->runtime = rorun ? dl_se->runtime : 0;
		dl_se->runtime -= rq_clock(rq) - dl_se->deadline;
	}

	return 1;
}

extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);

/*
 * Update the current task's runtime statistics (provided it is still
 * a -deadline task and has not been removed from the dl_rq).
 */
static void update_curr_dl(struct rq *rq)
{
	struct task_struct *curr = rq->curr;
	struct sched_dl_entity *dl_se = &curr->dl;
	u64 delta_exec;

	if (!dl_task(curr) || !on_dl_rq(dl_se))
		return;

	/*
	 * Consumed budget is computed considering the time as
	 * observed by schedulable tasks (excluding time spent
	 * in hardirq context, etc.). Deadlines are instead
	 * computed using hard walltime. This seems to be the more
	 * natural solution, but the full ramifications of this
	 * approach need further study.
	 */
	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
	if (unlikely((s64)delta_exec <= 0))
		return;

	schedstat_set(curr->se.statistics.exec_max,
		      max(curr->se.statistics.exec_max, delta_exec));

	curr->se.sum_exec_runtime += delta_exec;
	account_group_exec_runtime(curr, delta_exec);

	curr->se.exec_start = rq_clock_task(rq);
	cpuacct_charge(curr, delta_exec);

	sched_rt_avg_update(rq, delta_exec);

	dl_se->runtime -= delta_exec;
	if (dl_runtime_exceeded(rq, dl_se)) {
		__dequeue_task_dl(rq, curr, 0);
		if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
			dl_se->dl_throttled = 1;
		else
			enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);

		if (!is_leftmost(curr, &rq->dl))
			resched_task(curr);
	}

	/*
	 * Because -- for now -- we share the rt bandwidth, we need to
	 * account our runtime there too, otherwise actual rt tasks
	 * would be able to exceed the shared quota.
	 *
	 * Account to the root rt group for now.
	 *
	 * The solution we're working towards is having the RT groups scheduled
	 * using deadline servers -- however there's a few nasties to figure
	 * out before that can happen.
	 */
	if (rt_bandwidth_enabled()) {
		struct rt_rq *rt_rq = &rq->rt;

		raw_spin_lock(&rt_rq->rt_runtime_lock);
		/*
		 * We'll let actual RT tasks worry about the overflow here, we
		 * have our own CBS to keep us inline; only account when RT
		 * bandwidth is relevant.
		 */
		if (sched_rt_bandwidth_account(rt_rq))
			rt_rq->rt_time += delta_exec;
		raw_spin_unlock(&rt_rq->rt_runtime_lock);
	}
}

#ifdef CONFIG_SMP

static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);

static inline u64 next_deadline(struct rq *rq)
{
	struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);

	if (next && dl_prio(next->prio))
		return next->dl.deadline;
	else
		return 0;
}

static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
{
	struct rq *rq = rq_of_dl_rq(dl_rq);

	if (dl_rq->earliest_dl.curr == 0 ||
	    dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
		/*
		 * If the dl_rq had no -deadline tasks, or if the new task
		 * has shorter deadline than the current one on dl_rq, we
		 * know that the previous earliest becomes our next earliest,
		 * as the new task becomes the earliest itself.
		 */
		dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
		dl_rq->earliest_dl.curr = deadline;
		cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
	} else if (dl_rq->earliest_dl.next == 0 ||
		   dl_time_before(deadline, dl_rq->earliest_dl.next)) {
		/*
		 * On the other hand, if the new -deadline task has a
		 * a later deadline than the earliest one on dl_rq, but
		 * it is earlier than the next (if any), we must
		 * recompute the next-earliest.
		 */
		dl_rq->earliest_dl.next = next_deadline(rq);
	}
}

static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
{
	struct rq *rq = rq_of_dl_rq(dl_rq);

	/*
	 * Since we may have removed our earliest (and/or next earliest)
	 * task we must recompute them.
	 */
	if (!dl_rq->dl_nr_running) {
		dl_rq->earliest_dl.curr = 0;
		dl_rq->earliest_dl.next = 0;
		cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
	} else {
		struct rb_node *leftmost = dl_rq->rb_leftmost;
		struct sched_dl_entity *entry;

		entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
		dl_rq->earliest_dl.curr = entry->deadline;
		dl_rq->earliest_dl.next = next_deadline(rq);
		cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
	}
}

#else

static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}

#endif /* CONFIG_SMP */

static inline
void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
	int prio = dl_task_of(dl_se)->prio;
	u64 deadline = dl_se->deadline;

	WARN_ON(!dl_prio(prio));
	dl_rq->dl_nr_running++;
	add_nr_running(rq_of_dl_rq(dl_rq), 1);

	inc_dl_deadline(dl_rq, deadline);
	inc_dl_migration(dl_se, dl_rq);
}

static inline
void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
	int prio = dl_task_of(dl_se)->prio;

	WARN_ON(!dl_prio(prio));
	WARN_ON(!dl_rq->dl_nr_running);
	dl_rq->dl_nr_running--;
	sub_nr_running(rq_of_dl_rq(dl_rq), 1);

	dec_dl_deadline(dl_rq, dl_se->deadline);
	dec_dl_migration(dl_se, dl_rq);
}

static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
	struct rb_node **link = &dl_rq->rb_root.rb_node;
	struct rb_node *parent = NULL;
	struct sched_dl_entity *entry;
	int leftmost = 1;

	BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));

	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_dl_entity, rb_node);
		if (dl_time_before(dl_se->deadline, entry->deadline))
			link = &parent->rb_left;
		else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	if (leftmost)
		dl_rq->rb_leftmost = &dl_se->rb_node;

	rb_link_node(&dl_se->rb_node, parent, link);
	rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);

	inc_dl_tasks(dl_se, dl_rq);
}

static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
{
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);

	if (RB_EMPTY_NODE(&dl_se->rb_node))
		return;

	if (dl_rq->rb_leftmost == &dl_se->rb_node) {
		struct rb_node *next_node;

		next_node = rb_next(&dl_se->rb_node);
		dl_rq->rb_leftmost = next_node;
	}

	rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
	RB_CLEAR_NODE(&dl_se->rb_node);

	dec_dl_tasks(dl_se, dl_rq);
}

static void
enqueue_dl_entity(struct sched_dl_entity *dl_se,
		  struct sched_dl_entity *pi_se, int flags)
{
	BUG_ON(on_dl_rq(dl_se));

	/*
	 * If this is a wakeup or a new instance, the scheduling
	 * parameters of the task might need updating. Otherwise,
	 * we want a replenishment of its runtime.
	 */
	if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
		replenish_dl_entity(dl_se, pi_se);
	else
		update_dl_entity(dl_se, pi_se);

	__enqueue_dl_entity(dl_se);
}

static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
{
	__dequeue_dl_entity(dl_se);
}

static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
	struct task_struct *pi_task = rt_mutex_get_top_task(p);
	struct sched_dl_entity *pi_se = &p->dl;

	/*
	 * Use the scheduling parameters of the top pi-waiter
	 * task if we have one and its (relative) deadline is
	 * smaller than our one... OTW we keep our runtime and
	 * deadline.
	 */
	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
		pi_se = &pi_task->dl;

	/*
	 * If p is throttled, we do nothing. In fact, if it exhausted
	 * its budget it needs a replenishment and, since it now is on
	 * its rq, the bandwidth timer callback (which clearly has not
	 * run yet) will take care of this.
	 */
	if (p->dl.dl_throttled)
		return;

	enqueue_dl_entity(&p->dl, pi_se, flags);

	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
		enqueue_pushable_dl_task(rq, p);
}

static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
	dequeue_dl_entity(&p->dl);
	dequeue_pushable_dl_task(rq, p);
}

static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
	update_curr_dl(rq);
	__dequeue_task_dl(rq, p, flags);
}

/*
 * Yield task semantic for -deadline tasks is:
 *
 *   get off from the CPU until our next instance, with
 *   a new runtime. This is of little use now, since we
 *   don't have a bandwidth reclaiming mechanism. Anyway,
 *   bandwidth reclaiming is planned for the future, and
 *   yield_task_dl will indicate that some spare budget
 *   is available for other task instances to use it.
 */
static void yield_task_dl(struct rq *rq)
{
	struct task_struct *p = rq->curr;

	/*
	 * We make the task go to sleep until its current deadline by
	 * forcing its runtime to zero. This way, update_curr_dl() stops
	 * it and the bandwidth timer will wake it up and will give it
	 * new scheduling parameters (thanks to dl_yielded=1).
	 */
	if (p->dl.runtime > 0) {
		rq->curr->dl.dl_yielded = 1;
		p->dl.runtime = 0;
	}
	update_curr_dl(rq);
}

#ifdef CONFIG_SMP

static int find_later_rq(struct task_struct *task);

static int
select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
{
	struct task_struct *curr;
	struct rq *rq;

	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
		goto out;

	rq = cpu_rq(cpu);

	rcu_read_lock();
	curr = ACCESS_ONCE(rq->curr); /* unlocked access */

	/*
	 * If we are dealing with a -deadline task, we must
	 * decide where to wake it up.
	 * If it has a later deadline and the current task
	 * on this rq can't move (provided the waking task
	 * can!) we prefer to send it somewhere else. On the
	 * other hand, if it has a shorter deadline, we
	 * try to make it stay here, it might be important.
	 */
	if (unlikely(dl_task(curr)) &&
	    (curr->nr_cpus_allowed < 2 ||
	     !dl_entity_preempt(&p->dl, &curr->dl)) &&
	    (p->nr_cpus_allowed > 1)) {
		int target = find_later_rq(p);

		if (target != -1)
			cpu = target;
	}
	rcu_read_unlock();

out:
	return cpu;
}

static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
{
	/*
	 * Current can't be migrated, useless to reschedule,
	 * let's hope p can move out.
	 */
	if (rq->curr->nr_cpus_allowed == 1 ||
	    cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
		return;

	/*
	 * p is migratable, so let's not schedule it and
	 * see if it is pushed or pulled somewhere else.
	 */
	if (p->nr_cpus_allowed != 1 &&
	    cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
		return;

	resched_task(rq->curr);
}

static int pull_dl_task(struct rq *this_rq);

#endif /* CONFIG_SMP */

/*
 * Only called when both the current and waking task are -deadline
 * tasks.
 */
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
				  int flags)
{
	if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
		resched_task(rq->curr);
		return;
	}

#ifdef CONFIG_SMP
	/*
	 * In the unlikely case current and p have the same deadline
	 * let us try to decide what's the best thing to do...
	 */
	if ((p->dl.deadline == rq->curr->dl.deadline) &&
	    !test_tsk_need_resched(rq->curr))
		check_preempt_equal_dl(rq, p);
#endif /* CONFIG_SMP */
}

#ifdef CONFIG_SCHED_HRTICK
static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
{
	s64 delta = p->dl.dl_runtime - p->dl.runtime;

	if (delta > 10000)
		hrtick_start(rq, p->dl.runtime);
}
#endif

static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
						   struct dl_rq *dl_rq)
{
	struct rb_node *left = dl_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_dl_entity, rb_node);
}

struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
{
	struct sched_dl_entity *dl_se;
	struct task_struct *p;
	struct dl_rq *dl_rq;

	dl_rq = &rq->dl;

	if (need_pull_dl_task(rq, prev)) {
		pull_dl_task(rq);
		/*
		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
		 * means a stop task can slip in, in which case we need to
		 * re-start task selection.
		 */
		if (rq->stop && rq->stop->on_rq)
			return RETRY_TASK;
	}

	/*
	 * When prev is DL, we may throttle it in put_prev_task().
	 * So, we update time before we check for dl_nr_running.
	 */
	if (prev->sched_class == &dl_sched_class)
		update_curr_dl(rq);

	if (unlikely(!dl_rq->dl_nr_running))
		return NULL;

	put_prev_task(rq, prev);

	dl_se = pick_next_dl_entity(rq, dl_rq);
	BUG_ON(!dl_se);

	p = dl_task_of(dl_se);
	p->se.exec_start = rq_clock_task(rq);

	/* Running task will never be pushed. */
       dequeue_pushable_dl_task(rq, p);

#ifdef CONFIG_SCHED_HRTICK
	if (hrtick_enabled(rq))
		start_hrtick_dl(rq, p);
#endif

	set_post_schedule(rq);

	return p;
}

static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
{
	update_curr_dl(rq);

	if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
		enqueue_pushable_dl_task(rq, p);
}

static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
{
	update_curr_dl(rq);

#ifdef CONFIG_SCHED_HRTICK
	if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
		start_hrtick_dl(rq, p);
#endif
}

static void task_fork_dl(struct task_struct *p)
{
	/*
	 * SCHED_DEADLINE tasks cannot fork and this is achieved through
	 * sched_fork()
	 */
}

static void task_dead_dl(struct task_struct *p)
{
	struct hrtimer *timer = &p->dl.dl_timer;
	struct dl_bw *dl_b = dl_bw_of(task_cpu(p));

	/*
	 * Since we are TASK_DEAD we won't slip out of the domain!
	 */
	raw_spin_lock_irq(&dl_b->lock);
	dl_b->total_bw -= p->dl.dl_bw;
	raw_spin_unlock_irq(&dl_b->lock);

	hrtimer_cancel(timer);
}

static void set_curr_task_dl(struct rq *rq)
{
	struct task_struct *p = rq->curr;

	p->se.exec_start = rq_clock_task(rq);

	/* You can't push away the running task */
	dequeue_pushable_dl_task(rq, p);
}

#ifdef CONFIG_SMP

/* Only try algorithms three times */
#define DL_MAX_TRIES 3

static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
{
	if (!task_running(rq, p) &&
	    (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
	    (p->nr_cpus_allowed > 1))
		return 1;

	return 0;
}

/* Returns the second earliest -deadline task, NULL otherwise */
static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
{
	struct rb_node *next_node = rq->dl.rb_leftmost;
	struct sched_dl_entity *dl_se;
	struct task_struct *p = NULL;

next_node:
	next_node = rb_next(next_node);
	if (next_node) {
		dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
		p = dl_task_of(dl_se);

		if (pick_dl_task(rq, p, cpu))
			return p;

		goto next_node;
	}

	return NULL;
}

static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);

static int find_later_rq(struct task_struct *task)
{
	struct sched_domain *sd;
	struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
	int this_cpu = smp_processor_id();
	int best_cpu, cpu = task_cpu(task);

	/* Make sure the mask is initialized first */
	if (unlikely(!later_mask))
		return -1;

	if (task->nr_cpus_allowed == 1)
		return -1;

	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
			task, later_mask);
	if (best_cpu == -1)
		return -1;

	/*
	 * If we are here, some target has been found,
	 * the most suitable of which is cached in best_cpu.
	 * This is, among the runqueues where the current tasks
	 * have later deadlines than the task's one, the rq
	 * with the latest possible one.
	 *
	 * Now we check how well this matches with task's
	 * affinity and system topology.
	 *
	 * The last cpu where the task run is our first
	 * guess, since it is most likely cache-hot there.
	 */
	if (cpumask_test_cpu(cpu, later_mask))
		return cpu;
	/*
	 * Check if this_cpu is to be skipped (i.e., it is
	 * not in the mask) or not.
	 */
	if (!cpumask_test_cpu(this_cpu, later_mask))
		this_cpu = -1;

	rcu_read_lock();
	for_each_domain(cpu, sd) {
		if (sd->flags & SD_WAKE_AFFINE) {

			/*
			 * If possible, preempting this_cpu is
			 * cheaper than migrating.
			 */
			if (this_cpu != -1 &&
			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
				rcu_read_unlock();
				return this_cpu;
			}

			/*
			 * Last chance: if best_cpu is valid and is
			 * in the mask, that becomes our choice.
			 */
			if (best_cpu < nr_cpu_ids &&
			    cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
				rcu_read_unlock();
				return best_cpu;
			}
		}
	}
	rcu_read_unlock();

	/*
	 * At this point, all our guesses failed, we just return
	 * 'something', and let the caller sort the things out.
	 */
	if (this_cpu != -1)
		return this_cpu;

	cpu = cpumask_any(later_mask);
	if (cpu < nr_cpu_ids)
		return cpu;

	return -1;
}

/* Locks the rq it finds */
static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
{
	struct rq *later_rq = NULL;
	int tries;
	int cpu;

	for (tries = 0; tries < DL_MAX_TRIES; tries++) {
		cpu = find_later_rq(task);

		if ((cpu == -1) || (cpu == rq->cpu))
			break;

		later_rq = cpu_rq(cpu);

		/* Retry if something changed. */
		if (double_lock_balance(rq, later_rq)) {
			if (unlikely(task_rq(task) != rq ||
				     !cpumask_test_cpu(later_rq->cpu,
				                       &task->cpus_allowed) ||
				     task_running(rq, task) || !task->on_rq)) {
				double_unlock_balance(rq, later_rq);
				later_rq = NULL;
				break;
			}
		}

		/*
		 * If the rq we found has no -deadline task, or
		 * its earliest one has a later deadline than our
		 * task, the rq is a good one.
		 */
		if (!later_rq->dl.dl_nr_running ||
		    dl_time_before(task->dl.deadline,
				   later_rq->dl.earliest_dl.curr))
			break;

		/* Otherwise we try again. */
		double_unlock_balance(rq, later_rq);
		later_rq = NULL;
	}

	return later_rq;
}

static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
{
	struct task_struct *p;

	if (!has_pushable_dl_tasks(rq))
		return NULL;

	p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
		     struct task_struct, pushable_dl_tasks);

	BUG_ON(rq->cpu != task_cpu(p));
	BUG_ON(task_current(rq, p));
	BUG_ON(p->nr_cpus_allowed <= 1);

	BUG_ON(!p->on_rq);
	BUG_ON(!dl_task(p));

	return p;
}

/*
 * See if the non running -deadline tasks on this rq
 * can be sent to some other CPU where they can preempt
 * and start executing.
 */
static int push_dl_task(struct rq *rq)
{
	struct task_struct *next_task;
	struct rq *later_rq;

	if (!rq->dl.overloaded)
		return 0;

	next_task = pick_next_pushable_dl_task(rq);
	if (!next_task)
		return 0;

retry:
	if (unlikely(next_task == rq->curr)) {
		WARN_ON(1);
		return 0;
	}

	/*
	 * If next_task preempts rq->curr, and rq->curr
	 * can move away, it makes sense to just reschedule
	 * without going further in pushing next_task.
	 */
	if (dl_task(rq->curr) &&
	    dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
	    rq->curr->nr_cpus_allowed > 1) {
		resched_task(rq->curr);
		return 0;
	}

	/* We might release rq lock */
	get_task_struct(next_task);

	/* Will lock the rq it'll find */
	later_rq = find_lock_later_rq(next_task, rq);
	if (!later_rq) {
		struct task_struct *task;

		/*
		 * We must check all this again, since
		 * find_lock_later_rq releases rq->lock and it is
		 * then possible that next_task has migrated.
		 */
		task = pick_next_pushable_dl_task(rq);
		if (task_cpu(next_task) == rq->cpu && task == next_task) {
			/*
			 * The task is still there. We don't try
			 * again, some other cpu will pull it when ready.
			 */
			dequeue_pushable_dl_task(rq, next_task);
			goto out;
		}

		if (!task)
			/* No more tasks */
			goto out;

		put_task_struct(next_task);
		next_task = task;
		goto retry;
	}

	deactivate_task(rq, next_task, 0);
	set_task_cpu(next_task, later_rq->cpu);
	activate_task(later_rq, next_task, 0);

	resched_task(later_rq->curr);

	double_unlock_balance(rq, later_rq);

out:
	put_task_struct(next_task);

	return 1;
}

static void push_dl_tasks(struct rq *rq)
{
	/* Terminates as it moves a -deadline task */
	while (push_dl_task(rq))
		;
}

static int pull_dl_task(struct rq *this_rq)
{
	int this_cpu = this_rq->cpu, ret = 0, cpu;
	struct task_struct *p;
	struct rq *src_rq;
	u64 dmin = LONG_MAX;

	if (likely(!dl_overloaded(this_rq)))
		return 0;

	/*
	 * Match the barrier from dl_set_overloaded; this guarantees that if we
	 * see overloaded we must also see the dlo_mask bit.
	 */
	smp_rmb();

	for_each_cpu(cpu, this_rq->rd->dlo_mask) {
		if (this_cpu == cpu)
			continue;

		src_rq = cpu_rq(cpu);

		/*
		 * It looks racy, abd it is! However, as in sched_rt.c,
		 * we are fine with this.
		 */
		if (this_rq->dl.dl_nr_running &&
		    dl_time_before(this_rq->dl.earliest_dl.curr,
				   src_rq->dl.earliest_dl.next))
			continue;

		/* Might drop this_rq->lock */
		double_lock_balance(this_rq, src_rq);

		/*
		 * If there are no more pullable tasks on the
		 * rq, we're done with it.
		 */
		if (src_rq->dl.dl_nr_running <= 1)
			goto skip;

		p = pick_next_earliest_dl_task(src_rq, this_cpu);

		/*
		 * We found a task to be pulled if:
		 *  - it preempts our current (if there's one),
		 *  - it will preempt the last one we pulled (if any).
		 */
		if (p && dl_time_before(p->dl.deadline, dmin) &&
		    (!this_rq->dl.dl_nr_running ||
		     dl_time_before(p->dl.deadline,
				    this_rq->dl.earliest_dl.curr))) {
			WARN_ON(p == src_rq->curr);
			WARN_ON(!p->on_rq);

			/*
			 * Then we pull iff p has actually an earlier
			 * deadline than the current task of its runqueue.
			 */
			if (dl_time_before(p->dl.deadline,
					   src_rq->curr->dl.deadline))
				goto skip;

			ret = 1;

			deactivate_task(src_rq, p, 0);
			set_task_cpu(p, this_cpu);
			activate_task(this_rq, p, 0);
			dmin = p->dl.deadline;

			/* Is there any other task even earlier? */
		}
skip:
		double_unlock_balance(this_rq, src_rq);
	}

	return ret;
}

static void post_schedule_dl(struct rq *rq)
{
	push_dl_tasks(rq);
}

/*
 * Since the task is not running and a reschedule is not going to happen
 * anytime soon on its runqueue, we try pushing it away now.
 */
static void task_woken_dl(struct rq *rq, struct task_struct *p)
{
	if (!task_running(rq, p) &&
	    !test_tsk_need_resched(rq->curr) &&
	    has_pushable_dl_tasks(rq) &&
	    p->nr_cpus_allowed > 1 &&
	    dl_task(rq->curr) &&
	    (rq->curr->nr_cpus_allowed < 2 ||
	     dl_entity_preempt(&rq->curr->dl, &p->dl))) {
		push_dl_tasks(rq);
	}
}

static void set_cpus_allowed_dl(struct task_struct *p,
				const struct cpumask *new_mask)
{
	struct rq *rq;
	int weight;

	BUG_ON(!dl_task(p));

	/*
	 * Update only if the task is actually running (i.e.,
	 * it is on the rq AND it is not throttled).
	 */
	if (!on_dl_rq(&p->dl))
		return;

	weight = cpumask_weight(new_mask);

	/*
	 * Only update if the process changes its state from whether it
	 * can migrate or not.
	 */
	if ((p->nr_cpus_allowed > 1) == (weight > 1))
		return;

	rq = task_rq(p);

	/*
	 * The process used to be able to migrate OR it can now migrate
	 */
	if (weight <= 1) {
		if (!task_current(rq, p))
			dequeue_pushable_dl_task(rq, p);
		BUG_ON(!rq->dl.dl_nr_migratory);
		rq->dl.dl_nr_migratory--;
	} else {
		if (!task_current(rq, p))
			enqueue_pushable_dl_task(rq, p);
		rq->dl.dl_nr_migratory++;
	}

	update_dl_migration(&rq->dl);
}

/* Assumes rq->lock is held */
static void rq_online_dl(struct rq *rq)
{
	if (rq->dl.overloaded)
		dl_set_overload(rq);

	if (rq->dl.dl_nr_running > 0)
		cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
}

/* Assumes rq->lock is held */
static void rq_offline_dl(struct rq *rq)
{
	if (rq->dl.overloaded)
		dl_clear_overload(rq);

	cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
}

void init_sched_dl_class(void)
{
	unsigned int i;

	for_each_possible_cpu(i)
		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
					GFP_KERNEL, cpu_to_node(i));
}

#endif /* CONFIG_SMP */

static void switched_from_dl(struct rq *rq, struct task_struct *p)
{
	if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
		hrtimer_try_to_cancel(&p->dl.dl_timer);

#ifdef CONFIG_SMP
	/*
	 * Since this might be the only -deadline task on the rq,
	 * this is the right place to try to pull some other one
	 * from an overloaded cpu, if any.
	 */
	if (!rq->dl.dl_nr_running)
		pull_dl_task(rq);
#endif
}

/*
 * When switching to -deadline, we may overload the rq, then
 * we try to push someone off, if possible.
 */
static void switched_to_dl(struct rq *rq, struct task_struct *p)
{
	int check_resched = 1;

	/*
	 * If p is throttled, don't consider the possibility
	 * of preempting rq->curr, the check will be done right
	 * after its runtime will get replenished.
	 */
	if (unlikely(p->dl.dl_throttled))
		return;

	if (p->on_rq && rq->curr != p) {
#ifdef CONFIG_SMP
		if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
			/* Only reschedule if pushing failed */
			check_resched = 0;
#endif /* CONFIG_SMP */
		if (check_resched && task_has_dl_policy(rq->curr))
			check_preempt_curr_dl(rq, p, 0);
	}
}

/*
 * If the scheduling parameters of a -deadline task changed,
 * a push or pull operation might be needed.
 */
static void prio_changed_dl(struct rq *rq, struct task_struct *p,
			    int oldprio)
{
	if (p->on_rq || rq->curr == p) {
#ifdef CONFIG_SMP
		/*
		 * This might be too much, but unfortunately
		 * we don't have the old deadline value, and
		 * we can't argue if the task is increasing
		 * or lowering its prio, so...
		 */
		if (!rq->dl.overloaded)
			pull_dl_task(rq);

		/*
		 * If we now have a earlier deadline task than p,
		 * then reschedule, provided p is still on this
		 * runqueue.
		 */
		if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
		    rq->curr == p)
			resched_task(p);
#else
		/*
		 * Again, we don't know if p has a earlier
		 * or later deadline, so let's blindly set a
		 * (maybe not needed) rescheduling point.
		 */
		resched_task(p);
#endif /* CONFIG_SMP */
	} else
		switched_to_dl(rq, p);
}

const struct sched_class dl_sched_class = {
	.next			= &rt_sched_class,
	.enqueue_task		= enqueue_task_dl,
	.dequeue_task		= dequeue_task_dl,
	.yield_task		= yield_task_dl,

	.check_preempt_curr	= check_preempt_curr_dl,

	.pick_next_task		= pick_next_task_dl,
	.put_prev_task		= put_prev_task_dl,

#ifdef CONFIG_SMP
	.select_task_rq		= select_task_rq_dl,
	.set_cpus_allowed       = set_cpus_allowed_dl,
	.rq_online              = rq_online_dl,
	.rq_offline             = rq_offline_dl,
	.post_schedule		= post_schedule_dl,
	.task_woken		= task_woken_dl,
#endif

	.set_curr_task		= set_curr_task_dl,
	.task_tick		= task_tick_dl,
	.task_fork              = task_fork_dl,
	.task_dead		= task_dead_dl,

	.prio_changed           = prio_changed_dl,
	.switched_from		= switched_from_dl,
	.switched_to		= switched_to_dl,
};