aboutsummaryrefslogtreecommitdiffstats
path: root/arch/powerpc/platforms/cell/spufs/sched.c
blob: 5d5f680cd0b8ced5789556e444a0b8b955cc23c8 (plain) (blame)
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
/* sched.c - SPU scheduler.
 *
 * Copyright (C) IBM 2005
 * Author: Mark Nutter <mnutter@us.ibm.com>
 *
 * 2006-03-31	NUMA domains added.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#undef DEBUG

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/completion.h>
#include <linux/vmalloc.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/numa.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/pid_namespace.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/marker.h>

#include <asm/io.h>
#include <asm/mmu_context.h>
#include <asm/spu.h>
#include <asm/spu_csa.h>
#include <asm/spu_priv1.h>
#include "spufs.h"

struct spu_prio_array {
	DECLARE_BITMAP(bitmap, MAX_PRIO);
	struct list_head runq[MAX_PRIO];
	spinlock_t runq_lock;
	int nr_waiting;
};

static unsigned long spu_avenrun[3];
static struct spu_prio_array *spu_prio;
static struct task_struct *spusched_task;
static struct timer_list spusched_timer;
static struct timer_list spuloadavg_timer;

/*
 * Priority of a normal, non-rt, non-niced'd process (aka nice level 0).
 */
#define NORMAL_PRIO		120

/*
 * Frequency of the spu scheduler tick.  By default we do one SPU scheduler
 * tick for every 10 CPU scheduler ticks.
 */
#define SPUSCHED_TICK		(10)

/*
 * These are the 'tuning knobs' of the scheduler:
 *
 * Minimum timeslice is 5 msecs (or 1 spu scheduler tick, whichever is
 * larger), default timeslice is 100 msecs, maximum timeslice is 800 msecs.
 */
#define MIN_SPU_TIMESLICE	max(5 * HZ / (1000 * SPUSCHED_TICK), 1)
#define DEF_SPU_TIMESLICE	(100 * HZ / (1000 * SPUSCHED_TICK))

#define MAX_USER_PRIO		(MAX_PRIO - MAX_RT_PRIO)
#define SCALE_PRIO(x, prio) \
	max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_SPU_TIMESLICE)

/*
 * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:
 * [800ms ... 100ms ... 5ms]
 *
 * The higher a thread's priority, the bigger timeslices
 * it gets during one round of execution. But even the lowest
 * priority thread gets MIN_TIMESLICE worth of execution time.
 */
void spu_set_timeslice(struct spu_context *ctx)
{
	if (ctx->prio < NORMAL_PRIO)
		ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE * 4, ctx->prio);
	else
		ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE, ctx->prio);
}

/*
 * Update scheduling information from the owning thread.
 */
void __spu_update_sched_info(struct spu_context *ctx)
{
	/*
	 * assert that the context is not on the runqueue, so it is safe
	 * to change its scheduling parameters.
	 */
	BUG_ON(!list_empty(&ctx->rq));

	/*
	 * 32-Bit assignments are atomic on powerpc, and we don't care about
	 * memory ordering here because retrieving the controlling thread is
	 * per definition racy.
	 */
	ctx->tid = current->pid;

	/*
	 * We do our own priority calculations, so we normally want
	 * ->static_prio to start with. Unfortunately this field
	 * contains junk for threads with a realtime scheduling
	 * policy so we have to look at ->prio in this case.
	 */
	if (rt_prio(current->prio))
		ctx->prio = current->prio;
	else
		ctx->prio = current->static_prio;
	ctx->policy = current->policy;

	/*
	 * TO DO: the context may be loaded, so we may need to activate
	 * it again on a different node. But it shouldn't hurt anything
	 * to update its parameters, because we know that the scheduler
	 * is not actively looking at this field, since it is not on the
	 * runqueue. The context will be rescheduled on the proper node
	 * if it is timesliced or preempted.
	 */
	ctx->cpus_allowed = current->cpus_allowed;
}

void spu_update_sched_info(struct spu_context *ctx)
{
	int node;

	if (ctx->state == SPU_STATE_RUNNABLE) {
		node = ctx->spu->node;

		/*
		 * Take list_mutex to sync with find_victim().
		 */
		mutex_lock(&cbe_spu_info[node].list_mutex);
		__spu_update_sched_info(ctx);
		mutex_unlock(&cbe_spu_info[node].list_mutex);
	} else {
		__spu_update_sched_info(ctx);
	}
}

static int __node_allowed(struct spu_context *ctx, int node)
{
	if (nr_cpus_node(node)) {
		cpumask_t mask = node_to_cpumask(node);

		if (cpus_intersects(mask, ctx->cpus_allowed))
			return 1;
	}

	return 0;
}

static int node_allowed(struct spu_context *ctx, int node)
{
	int rval;

	spin_lock(&spu_prio->runq_lock);
	rval = __node_allowed(ctx, node);
	spin_unlock(&spu_prio->runq_lock);

	return rval;
}

void do_notify_spus_active(void)
{
	int node;

	/*
	 * Wake up the active spu_contexts.
	 *
	 * When the awakened processes see their "notify_active" flag is set,
	 * they will call spu_switch_notify().
	 */
	for_each_online_node(node) {
		struct spu *spu;

		mutex_lock(&cbe_spu_info[node].list_mutex);
		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
			if (spu->alloc_state != SPU_FREE) {
				struct spu_context *ctx = spu->ctx;
				set_bit(SPU_SCHED_NOTIFY_ACTIVE,
					&ctx->sched_flags);
				mb();
				wake_up_all(&ctx->stop_wq);
			}
		}
		mutex_unlock(&cbe_spu_info[node].list_mutex);
	}
}

/**
 * spu_bind_context - bind spu context to physical spu
 * @spu:	physical spu to bind to
 * @ctx:	context to bind
 */
static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
{
	spu_context_trace(spu_bind_context__enter, ctx, spu);

	spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);

	if (ctx->flags & SPU_CREATE_NOSCHED)
		atomic_inc(&cbe_spu_info[spu->node].reserved_spus);

	ctx->stats.slb_flt_base = spu->stats.slb_flt;
	ctx->stats.class2_intr_base = spu->stats.class2_intr;

	spu->ctx = ctx;
	spu->flags = 0;
	ctx->spu = spu;
	ctx->ops = &spu_hw_ops;
	spu->pid = current->pid;
	spu->tgid = current->tgid;
	spu_associate_mm(spu, ctx->owner);
	spu->ibox_callback = spufs_ibox_callback;
	spu->wbox_callback = spufs_wbox_callback;
	spu->stop_callback = spufs_stop_callback;
	spu->mfc_callback = spufs_mfc_callback;
	mb();
	spu_unmap_mappings(ctx);
	spu_restore(&ctx->csa, spu);
	spu->timestamp = jiffies;
	spu_cpu_affinity_set(spu, raw_smp_processor_id());
	spu_switch_notify(spu, ctx);
	ctx->state = SPU_STATE_RUNNABLE;

	spuctx_switch_state(ctx, SPU_UTIL_USER);
}

/*
 * Must be used with the list_mutex held.
 */
static inline int sched_spu(struct spu *spu)
{
	BUG_ON(!mutex_is_locked(&cbe_spu_info[spu->node].list_mutex));

	return (!spu->ctx || !(spu->ctx->flags & SPU_CREATE_NOSCHED));
}

static void aff_merge_remaining_ctxs(struct spu_gang *gang)
{
	struct spu_context *ctx;

	list_for_each_entry(ctx, &gang->aff_list_head, aff_list) {
		if (list_empty(&ctx->aff_list))
			list_add(&ctx->aff_list, &gang->aff_list_head);
	}
	gang->aff_flags |= AFF_MERGED;
}

static void aff_set_offsets(struct spu_gang *gang)
{
	struct spu_context *ctx;
	int offset;

	offset = -1;
	list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
								aff_list) {
		if (&ctx->aff_list == &gang->aff_list_head)
			break;
		ctx->aff_offset = offset--;
	}

	offset = 0;
	list_for_each_entry(ctx, gang->aff_ref_ctx->aff_list.prev, aff_list) {
		if (&ctx->aff_list == &gang->aff_list_head)
			break;
		ctx->aff_offset = offset++;
	}

	gang->aff_flags |= AFF_OFFSETS_SET;
}

static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
		 int group_size, int lowest_offset)
{
	struct spu *spu;
	int node, n;

	/*
	 * TODO: A better algorithm could be used to find a good spu to be
	 *       used as reference location for the ctxs chain.
	 */
	node = cpu_to_node(raw_smp_processor_id());
	for (n = 0; n < MAX_NUMNODES; n++, node++) {
		node = (node < MAX_NUMNODES) ? node : 0;
		if (!node_allowed(ctx, node))
			continue;
		mutex_lock(&cbe_spu_info[node].list_mutex);
		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
			if ((!mem_aff || spu->has_mem_affinity) &&
							sched_spu(spu)) {
				mutex_unlock(&cbe_spu_info[node].list_mutex);
				return spu;
			}
		}
		mutex_unlock(&cbe_spu_info[node].list_mutex);
	}
	return NULL;
}

static void aff_set_ref_point_location(struct spu_gang *gang)
{
	int mem_aff, gs, lowest_offset;
	struct spu_context *ctx;
	struct spu *tmp;

	mem_aff = gang->aff_ref_ctx->flags & SPU_CREATE_AFFINITY_MEM;
	lowest_offset = 0;
	gs = 0;

	list_for_each_entry(tmp, &gang->aff_list_head, aff_list)
		gs++;

	list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
								aff_list) {
		if (&ctx->aff_list == &gang->aff_list_head)
			break;
		lowest_offset = ctx->aff_offset;
	}

	gang->aff_ref_spu = aff_ref_location(gang->aff_ref_ctx, mem_aff, gs,
							lowest_offset);
}

static struct spu *ctx_location(struct spu *ref, int offset, int node)
{
	struct spu *spu;

	spu = NULL;
	if (offset >= 0) {
		list_for_each_entry(spu, ref->aff_list.prev, aff_list) {
			BUG_ON(spu->node != node);
			if (offset == 0)
				break;
			if (sched_spu(spu))
				offset--;
		}
	} else {
		list_for_each_entry_reverse(spu, ref->aff_list.next, aff_list) {
			BUG_ON(spu->node != node);
			if (offset == 0)
				break;
			if (sched_spu(spu))
				offset++;
		}
	}

	return spu;
}

/*
 * affinity_check is called each time a context is going to be scheduled.
 * It returns the spu ptr on which the context must run.
 */
static int has_affinity(struct spu_context *ctx)
{
	struct spu_gang *gang = ctx->gang;

	if (list_empty(&ctx->aff_list))
		return 0;

	if (!gang->aff_ref_spu) {
		if (!(gang->aff_flags & AFF_MERGED))
			aff_merge_remaining_ctxs(gang);
		if (!(gang->aff_flags & AFF_OFFSETS_SET))
			aff_set_offsets(gang);
		aff_set_ref_point_location(gang);
	}

	return gang->aff_ref_spu != NULL;
}

/**
 * spu_unbind_context - unbind spu context from physical spu
 * @spu:	physical spu to unbind from
 * @ctx:	context to unbind
 */
static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
{
	spu_context_trace(spu_unbind_context__enter, ctx, spu);

	spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);

 	if (spu->ctx->flags & SPU_CREATE_NOSCHED)
		atomic_dec(&cbe_spu_info[spu->node].reserved_spus);

	if (ctx->gang){
		mutex_lock(&ctx->gang->aff_mutex);
		if (has_affinity(ctx)) {
			if (atomic_dec_and_test(&ctx->gang->aff_sched_count))
				ctx->gang->aff_ref_spu = NULL;
		}
		mutex_unlock(&ctx->gang->aff_mutex);
	}

	spu_switch_notify(spu, NULL);
	spu_unmap_mappings(ctx);
	spu_save(&ctx->csa, spu);
	spu->timestamp = jiffies;
	ctx->state = SPU_STATE_SAVED;
	spu->ibox_callback = NULL;
	spu->wbox_callback = NULL;
	spu->stop_callback = NULL;
	spu->mfc_callback = NULL;
	spu_associate_mm(spu, NULL);
	spu->pid = 0;
	spu->tgid = 0;
	ctx->ops = &spu_backing_ops;
	spu->flags = 0;
	spu->ctx = NULL;

	ctx->stats.slb_flt +=
		(spu->stats.slb_flt - ctx->stats.slb_flt_base);
	ctx->stats.class2_intr +=
		(spu->stats.class2_intr - ctx->stats.class2_intr_base);

	/* This maps the underlying spu state to idle */
	spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
	ctx->spu = NULL;
}

/**
 * spu_add_to_rq - add a context to the runqueue
 * @ctx:       context to add
 */
static void __spu_add_to_rq(struct spu_context *ctx)
{
	/*
	 * Unfortunately this code path can be called from multiple threads
	 * on behalf of a single context due to the way the problem state
	 * mmap support works.
	 *
	 * Fortunately we need to wake up all these threads at the same time
	 * and can simply skip the runqueue addition for every but the first
	 * thread getting into this codepath.
	 *
	 * It's still quite hacky, and long-term we should proxy all other
	 * threads through the owner thread so that spu_run is in control
	 * of all the scheduling activity for a given context.
	 */
	if (list_empty(&ctx->rq)) {
		list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
		set_bit(ctx->prio, spu_prio->bitmap);
		if (!spu_prio->nr_waiting++)
			__mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
	}
}

static void spu_add_to_rq(struct spu_context *ctx)
{
	spin_lock(&spu_prio->runq_lock);
	__spu_add_to_rq(ctx);
	spin_unlock(&spu_prio->runq_lock);
}

static void __spu_del_from_rq(struct spu_context *ctx)
{
	int prio = ctx->prio;

	if (!list_empty(&ctx->rq)) {
		if (!--spu_prio->nr_waiting)
			del_timer(&spusched_timer);
		list_del_init(&ctx->rq);

		if (list_empty(&spu_prio->runq[prio]))
			clear_bit(prio, spu_prio->bitmap);
	}
}

void spu_del_from_rq(struct spu_context *ctx)
{
	spin_lock(&spu_prio->runq_lock);
	__spu_del_from_rq(ctx);
	spin_unlock(&spu_prio->runq_lock);
}

static void spu_prio_wait(struct spu_context *ctx)
{
	DEFINE_WAIT(wait);

	/*
	 * The caller must explicitly wait for a context to be loaded
	 * if the nosched flag is set.  If NOSCHED is not set, the caller
	 * queues the context and waits for an spu event or error.
	 */
	BUG_ON(!(ctx->flags & SPU_CREATE_NOSCHED));

	spin_lock(&spu_prio->runq_lock);
	prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
	if (!signal_pending(current)) {
		__spu_add_to_rq(ctx);
		spin_unlock(&spu_prio->runq_lock);
		mutex_unlock(&ctx->state_mutex);
		schedule();
		mutex_lock(&ctx->state_mutex);
		spin_lock(&spu_prio->runq_lock);
		__spu_del_from_rq(ctx);
	}
	spin_unlock(&spu_prio->runq_lock);
	__set_current_state(TASK_RUNNING);
	remove_wait_queue(&ctx->stop_wq, &wait);
}

static struct spu *spu_get_idle(struct spu_context *ctx)
{
	struct spu *spu, *aff_ref_spu;
	int node, n;

	spu_context_nospu_trace(spu_get_idle__enter, ctx);

	if (ctx->gang) {
		mutex_lock(&ctx->gang->aff_mutex);
		if (has_affinity(ctx)) {
			aff_ref_spu = ctx->gang->aff_ref_spu;
			atomic_inc(&ctx->gang->aff_sched_count);
			mutex_unlock(&ctx->gang->aff_mutex);
			node = aff_ref_spu->node;

			mutex_lock(&cbe_spu_info[node].list_mutex);
			spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
			if (spu && spu->alloc_state == SPU_FREE)
				goto found;
			mutex_unlock(&cbe_spu_info[node].list_mutex);

			mutex_lock(&ctx->gang->aff_mutex);
			if (atomic_dec_and_test(&ctx->gang->aff_sched_count))
				ctx->gang->aff_ref_spu = NULL;
			mutex_unlock(&ctx->gang->aff_mutex);
			goto not_found;
		}
		mutex_unlock(&ctx->gang->aff_mutex);
	}
	node = cpu_to_node(raw_smp_processor_id());
	for (n = 0; n < MAX_NUMNODES; n++, node++) {
		node = (node < MAX_NUMNODES) ? node : 0;
		if (!node_allowed(ctx, node))
			continue;

		mutex_lock(&cbe_spu_info[node].list_mutex);
		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
			if (spu->alloc_state == SPU_FREE)
				goto found;
		}
		mutex_unlock(&cbe_spu_info[node].list_mutex);
	}

 not_found:
	spu_context_nospu_trace(spu_get_idle__not_found, ctx);
	return NULL;

 found:
	spu->alloc_state = SPU_USED;
	mutex_unlock(&cbe_spu_info[node].list_mutex);
	spu_context_trace(spu_get_idle__found, ctx, spu);
	spu_init_channels(spu);
	return spu;
}

/**
 * find_victim - find a lower priority context to preempt
 * @ctx:	canidate context for running
 *
 * Returns the freed physical spu to run the new context on.
 */
static struct spu *find_victim(struct spu_context *ctx)
{
	struct spu_context *victim = NULL;
	struct spu *spu;
	int node, n;

	spu_context_nospu_trace(spu_find_vitim__enter, ctx);

	/*
	 * Look for a possible preemption candidate on the local node first.
	 * If there is no candidate look at the other nodes.  This isn't
	 * exactly fair, but so far the whole spu scheduler tries to keep
	 * a strong node affinity.  We might want to fine-tune this in
	 * the future.
	 */
 restart:
	node = cpu_to_node(raw_smp_processor_id());
	for (n = 0; n < MAX_NUMNODES; n++, node++) {
		node = (node < MAX_NUMNODES) ? node : 0;
		if (!node_allowed(ctx, node))
			continue;

		mutex_lock(&cbe_spu_info[node].list_mutex);
		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
			struct spu_context *tmp = spu->ctx;

			if (tmp && tmp->prio > ctx->prio &&
			    !(tmp->flags & SPU_CREATE_NOSCHED) &&
			    (!victim || tmp->prio > victim->prio))
				victim = spu->ctx;
		}
		mutex_unlock(&cbe_spu_info[node].list_mutex);

		if (victim) {
			/*
			 * This nests ctx->state_mutex, but we always lock
			 * higher priority contexts before lower priority
			 * ones, so this is safe until we introduce
			 * priority inheritance schemes.
			 *
			 * XXX if the highest priority context is locked,
			 * this can loop a long time.  Might be better to
			 * look at another context or give up after X retries.
			 */
			if (!mutex_trylock(&victim->state_mutex)) {
				victim = NULL;
				goto restart;
			}

			spu = victim->spu;
			if (!spu || victim->prio <= ctx->prio) {
				/*
				 * This race can happen because we've dropped
				 * the active list mutex.  Not a problem, just
				 * restart the search.
				 */
				mutex_unlock(&victim->state_mutex);
				victim = NULL;
				goto restart;
			}

			spu_context_trace(__spu_deactivate__unload, ctx, spu);

			mutex_lock(&cbe_spu_info[node].list_mutex);
			cbe_spu_info[node].nr_active--;
			spu_unbind_context(spu, victim);
			mutex_unlock(&cbe_spu_info[node].list_mutex);

			victim->stats.invol_ctx_switch++;
			spu->stats.invol_ctx_switch++;
			spu_add_to_rq(victim);

			mutex_unlock(&victim->state_mutex);

			return spu;
		}
	}

	return NULL;
}

static void __spu_schedule(struct spu *spu, struct spu_context *ctx)
{
	int node = spu->node;
	int success = 0;

	spu_set_timeslice(ctx);

	mutex_lock(&cbe_spu_info[node].list_mutex);
	if (spu->ctx == NULL) {
		spu_bind_context(spu, ctx);
		cbe_spu_info[node].nr_active++;
		spu->alloc_state = SPU_USED;
		success = 1;
	}
	mutex_unlock(&cbe_spu_info[node].list_mutex);

	if (success)
		wake_up_all(&ctx->run_wq);
	else
		spu_add_to_rq(ctx);
}

static void spu_schedule(struct spu *spu, struct spu_context *ctx)
{
	/* not a candidate for interruptible because it's called either
	   from the scheduler thread or from spu_deactivate */
	mutex_lock(&ctx->state_mutex);
	__spu_schedule(spu, ctx);
	spu_release(ctx);
}

static void spu_unschedule(struct spu *spu, struct spu_context *ctx)
{
	int node = spu->node;

	mutex_lock(&cbe_spu_info[node].list_mutex);
	cbe_spu_info[node].nr_active--;
	spu->alloc_state = SPU_FREE;
	spu_unbind_context(spu, ctx);
	ctx->stats.invol_ctx_switch++;
	spu->stats.invol_ctx_switch++;
	mutex_unlock(&cbe_spu_info[node].list_mutex);
}

/**
 * spu_activate - find a free spu for a context and execute it
 * @ctx:	spu context to schedule
 * @flags:	flags (currently ignored)
 *
 * Tries to find a free spu to run @ctx.  If no free spu is available
 * add the context to the runqueue so it gets woken up once an spu
 * is available.
 */
int spu_activate(struct spu_context *ctx, unsigned long flags)
{
	struct spu *spu;

	/*
	 * If there are multiple threads waiting for a single context
	 * only one actually binds the context while the others will
	 * only be able to acquire the state_mutex once the context
	 * already is in runnable state.
	 */
	if (ctx->spu)
		return 0;

spu_activate_top:
	if (signal_pending(current))
		return -ERESTARTSYS;

	spu = spu_get_idle(ctx);
	/*
	 * If this is a realtime thread we try to get it running by
	 * preempting a lower priority thread.
	 */
	if (!spu && rt_prio(ctx->prio))
		spu = find_victim(ctx);
	if (spu) {
		unsigned long runcntl;

		runcntl = ctx->ops->runcntl_read(ctx);
		__spu_schedule(spu, ctx);
		if (runcntl & SPU_RUNCNTL_RUNNABLE)
			spuctx_switch_state(ctx, SPU_UTIL_USER);

		return 0;
	}

	if (ctx->flags & SPU_CREATE_NOSCHED) {
		spu_prio_wait(ctx);
		goto spu_activate_top;
	}

	spu_add_to_rq(ctx);

	return 0;
}

/**
 * grab_runnable_context - try to find a runnable context
 *
 * Remove the highest priority context on the runqueue and return it
 * to the caller.  Returns %NULL if no runnable context was found.
 */
static struct spu_context *grab_runnable_context(int prio, int node)
{
	struct spu_context *ctx;
	int best;

	spin_lock(&spu_prio->runq_lock);
	best = find_first_bit(spu_prio->bitmap, prio);
	while (best < prio) {
		struct list_head *rq = &spu_prio->runq[best];

		list_for_each_entry(ctx, rq, rq) {
			/* XXX(hch): check for affinity here aswell */
			if (__node_allowed(ctx, node)) {
				__spu_del_from_rq(ctx);
				goto found;
			}
		}
		best++;
	}
	ctx = NULL;
 found:
	spin_unlock(&spu_prio->runq_lock);
	return ctx;
}

static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
{
	struct spu *spu = ctx->spu;
	struct spu_context *new = NULL;

	if (spu) {
		new = grab_runnable_context(max_prio, spu->node);
		if (new || force) {
			spu_unschedule(spu, ctx);
			if (new) {
				if (new->flags & SPU_CREATE_NOSCHED)
					wake_up(&new->stop_wq);
				else {
					spu_release(ctx);
					spu_schedule(spu, new);
					/* this one can't easily be made
					   interruptible */
					mutex_lock(&ctx->state_mutex);
				}
			}
		}
	}

	return new != NULL;
}

/**
 * spu_deactivate - unbind a context from it's physical spu
 * @ctx:	spu context to unbind
 *
 * Unbind @ctx from the physical spu it is running on and schedule
 * the highest priority context to run on the freed physical spu.
 */
void spu_deactivate(struct spu_context *ctx)
{
	spu_context_nospu_trace(spu_deactivate__enter, ctx);
	__spu_deactivate(ctx, 1, MAX_PRIO);
}

/**
 * spu_yield -	yield a physical spu if others are waiting
 * @ctx:	spu context to yield
 *
 * Check if there is a higher priority context waiting and if yes
 * unbind @ctx from the physical spu and schedule the highest
 * priority context to run on the freed physical spu instead.
 */
void spu_yield(struct spu_context *ctx)
{
	spu_context_nospu_trace(spu_yield__enter, ctx);
	if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
		mutex_lock(&ctx->state_mutex);
		__spu_deactivate(ctx, 0, MAX_PRIO);
		mutex_unlock(&ctx->state_mutex);
	}
}

static noinline void spusched_tick(struct spu_context *ctx)
{
	struct spu_context *new = NULL;
	struct spu *spu = NULL;

	if (spu_acquire(ctx))
		BUG();	/* a kernel thread never has signals pending */

	if (ctx->state != SPU_STATE_RUNNABLE)
		goto out;
	if (ctx->flags & SPU_CREATE_NOSCHED)
		goto out;
	if (ctx->policy == SCHED_FIFO)
		goto out;

	if (--ctx->time_slice && ctx->policy != SCHED_IDLE)
		goto out;

	spu = ctx->spu;

	spu_context_trace(spusched_tick__preempt, ctx, spu);

	new = grab_runnable_context(ctx->prio + 1, spu->node);
	if (new) {
		spu_unschedule(spu, ctx);
		if (ctx->policy != SCHED_IDLE)
			spu_add_to_rq(ctx);
	} else {
		spu_context_nospu_trace(spusched_tick__newslice, ctx);
		ctx->time_slice++;
	}
out:
	spu_release(ctx);

	if (new)
		spu_schedule(spu, new);
}

/**
 * count_active_contexts - count nr of active tasks
 *
 * Return the number of tasks currently running or waiting to run.
 *
 * Note that we don't take runq_lock / list_mutex here.  Reading
 * a single 32bit value is atomic on powerpc, and we don't care
 * about memory ordering issues here.
 */
static unsigned long count_active_contexts(void)
{
	int nr_active = 0, node;

	for (node = 0; node < MAX_NUMNODES; node++)
		nr_active += cbe_spu_info[node].nr_active;
	nr_active += spu_prio->nr_waiting;

	return nr_active;
}

/**
 * spu_calc_load - update the avenrun load estimates.
 *
 * No locking against reading these values from userspace, as for
 * the CPU loadavg code.
 */
static void spu_calc_load(void)
{
	unsigned long active_tasks; /* fixed-point */

	active_tasks = count_active_contexts() * FIXED_1;
	CALC_LOAD(spu_avenrun[0], EXP_1, active_tasks);
	CALC_LOAD(spu_avenrun[1], EXP_5, active_tasks);
	CALC_LOAD(spu_avenrun[2], EXP_15, active_tasks);
}

static void spusched_wake(unsigned long data)
{
	mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
	wake_up_process(spusched_task);
}

static void spuloadavg_wake(unsigned long data)
{
	mod_timer(&spuloadavg_timer, jiffies + LOAD_FREQ);
	spu_calc_load();
}

static int spusched_thread(void *unused)
{
	struct spu *spu;
	int node;

	while (!kthread_should_stop()) {
		set_current_state(TASK_INTERRUPTIBLE);
		schedule();
		for (node = 0; node < MAX_NUMNODES; node++) {
			struct mutex *mtx = &cbe_spu_info[node].list_mutex;

			mutex_lock(mtx);
			list_for_each_entry(spu, &cbe_spu_info[node].spus,
					cbe_list) {
				struct spu_context *ctx = spu->ctx;

				if (ctx) {
					mutex_unlock(mtx);
					spusched_tick(ctx);
					mutex_lock(mtx);
				}
			}
			mutex_unlock(mtx);
		}
	}

	return 0;
}

void spuctx_switch_state(struct spu_context *ctx,
		enum spu_utilization_state new_state)
{
	unsigned long long curtime;
	signed long long delta;
	struct timespec ts;
	struct spu *spu;
	enum spu_utilization_state old_state;

	ktime_get_ts(&ts);
	curtime = timespec_to_ns(&ts);
	delta = curtime - ctx->stats.tstamp;

	WARN_ON(!mutex_is_locked(&ctx->state_mutex));
	WARN_ON(delta < 0);

	spu = ctx->spu;
	old_state = ctx->stats.util_state;
	ctx->stats.util_state = new_state;
	ctx->stats.tstamp = curtime;

	/*
	 * Update the physical SPU utilization statistics.
	 */
	if (spu) {
		ctx->stats.times[old_state] += delta;
		spu->stats.times[old_state] += delta;
		spu->stats.util_state = new_state;
		spu->stats.tstamp = curtime;
	}
}

#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)

static int show_spu_loadavg(struct seq_file *s, void *private)
{
	int a, b, c;

	a = spu_avenrun[0] + (FIXED_1/200);
	b = spu_avenrun[1] + (FIXED_1/200);
	c = spu_avenrun[2] + (FIXED_1/200);

	/*
	 * Note that last_pid doesn't really make much sense for the
	 * SPU loadavg (it even seems very odd on the CPU side...),
	 * but we include it here to have a 100% compatible interface.
	 */
	seq_printf(s, "%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
		LOAD_INT(a), LOAD_FRAC(a),
		LOAD_INT(b), LOAD_FRAC(b),
		LOAD_INT(c), LOAD_FRAC(c),
		count_active_contexts(),
		atomic_read(&nr_spu_contexts),
		current->nsproxy->pid_ns->last_pid);
	return 0;
}

static int spu_loadavg_open(struct inode *inode, struct file *file)
{
	return single_open(file, show_spu_loadavg, NULL);
}

static const struct file_operations spu_loadavg_fops = {
	.open		= spu_loadavg_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

int __init spu_sched_init(void)
{
	struct proc_dir_entry *entry;
	int err = -ENOMEM, i;

	spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
	if (!spu_prio)
		goto out;

	for (i = 0; i < MAX_PRIO; i++) {
		INIT_LIST_HEAD(&spu_prio->runq[i]);
		__clear_bit(i, spu_prio->bitmap);
	}
	spin_lock_init(&spu_prio->runq_lock);

	setup_timer(&spusched_timer, spusched_wake, 0);
	setup_timer(&spuloadavg_timer, spuloadavg_wake, 0);

	spusched_task = kthread_run(spusched_thread, NULL, "spusched");
	if (IS_ERR(spusched_task)) {
		err = PTR_ERR(spusched_task);
		goto out_free_spu_prio;
	}

	mod_timer(&spuloadavg_timer, 0);

	entry = create_proc_entry("spu_loadavg", 0, NULL);
	if (!entry)
		goto out_stop_kthread;
	entry->proc_fops = &spu_loadavg_fops;

	pr_debug("spusched: tick: %d, min ticks: %d, default ticks: %d\n",
			SPUSCHED_TICK, MIN_SPU_TIMESLICE, DEF_SPU_TIMESLICE);
	return 0;

 out_stop_kthread:
	kthread_stop(spusched_task);
 out_free_spu_prio:
	kfree(spu_prio);
 out:
	return err;
}

void spu_sched_exit(void)
{
	struct spu *spu;
	int node;

	remove_proc_entry("spu_loadavg", NULL);

	del_timer_sync(&spusched_timer);
	del_timer_sync(&spuloadavg_timer);
	kthread_stop(spusched_task);

	for (node = 0; node < MAX_NUMNODES; node++) {
		mutex_lock(&cbe_spu_info[node].list_mutex);
		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list)
			if (spu->alloc_state != SPU_FREE)
				spu->alloc_state = SPU_FREE;
		mutex_unlock(&cbe_spu_info[node].list_mutex);
	}
	kfree(spu_prio);
}