summaryrefslogtreecommitdiff
path: root/net/sunrpc/sched.c
blob: 2d9eb7fbd5213323f870fa25286512e466a7e764 (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
/*
 * linux/net/sunrpc/sched.c
 *
 * Scheduling for synchronous and asynchronous RPC requests.
 *
 * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
 * 
 * TCP NFS related read + write fixes
 * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 */

#include <linux/module.h>

#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/spinlock.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/xprt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY		RPCDBG_SCHED
#define RPC_TASK_MAGIC_ID	0xf00baa
static int			rpc_task_id;
#endif

/*
 * RPC slabs and memory pools
 */
#define RPC_BUFFER_MAXSIZE	(2048)
#define RPC_BUFFER_POOLSIZE	(8)
#define RPC_TASK_POOLSIZE	(8)
static kmem_cache_t	*rpc_task_slabp;
static kmem_cache_t	*rpc_buffer_slabp;
static mempool_t	*rpc_task_mempool;
static mempool_t	*rpc_buffer_mempool;

static void			__rpc_default_timer(struct rpc_task *task);
static void			rpciod_killall(void);
static void			rpc_free(struct rpc_task *task);

static void			rpc_async_schedule(void *);

/*
 * RPC tasks that create another task (e.g. for contacting the portmapper)
 * will wait on this queue for their child's completion
 */
static RPC_WAITQ(childq, "childq");

/*
 * RPC tasks sit here while waiting for conditions to improve.
 */
static RPC_WAITQ(delay_queue, "delayq");

/*
 * All RPC tasks are linked into this list
 */
static LIST_HEAD(all_tasks);

/*
 * rpciod-related stuff
 */
static DECLARE_MUTEX(rpciod_sema);
static unsigned int		rpciod_users;
static struct workqueue_struct *rpciod_workqueue;

/*
 * Spinlock for other critical sections of code.
 */
static DEFINE_SPINLOCK(rpc_sched_lock);

/*
 * Disable the timer for a given RPC task. Should be called with
 * queue->lock and bh_disabled in order to avoid races within
 * rpc_run_timer().
 */
static inline void
__rpc_disable_timer(struct rpc_task *task)
{
	dprintk("RPC: %4d disabling timer\n", task->tk_pid);
	task->tk_timeout_fn = NULL;
	task->tk_timeout = 0;
}

/*
 * Run a timeout function.
 * We use the callback in order to allow __rpc_wake_up_task()
 * and friends to disable the timer synchronously on SMP systems
 * without calling del_timer_sync(). The latter could cause a
 * deadlock if called while we're holding spinlocks...
 */
static void rpc_run_timer(struct rpc_task *task)
{
	void (*callback)(struct rpc_task *);

	callback = task->tk_timeout_fn;
	task->tk_timeout_fn = NULL;
	if (callback && RPC_IS_QUEUED(task)) {
		dprintk("RPC: %4d running timer\n", task->tk_pid);
		callback(task);
	}
	smp_mb__before_clear_bit();
	clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
	smp_mb__after_clear_bit();
}

/*
 * Set up a timer for the current task.
 */
static inline void
__rpc_add_timer(struct rpc_task *task, rpc_action timer)
{
	if (!task->tk_timeout)
		return;

	dprintk("RPC: %4d setting alarm for %lu ms\n",
			task->tk_pid, task->tk_timeout * 1000 / HZ);

	if (timer)
		task->tk_timeout_fn = timer;
	else
		task->tk_timeout_fn = __rpc_default_timer;
	set_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
	mod_timer(&task->tk_timer, jiffies + task->tk_timeout);
}

/*
 * Delete any timer for the current task. Because we use del_timer_sync(),
 * this function should never be called while holding queue->lock.
 */
static void
rpc_delete_timer(struct rpc_task *task)
{
	if (RPC_IS_QUEUED(task))
		return;
	if (test_and_clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate)) {
		del_singleshot_timer_sync(&task->tk_timer);
		dprintk("RPC: %4d deleting timer\n", task->tk_pid);
	}
}

/*
 * Add new request to a priority queue.
 */
static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct rpc_task *task)
{
	struct list_head *q;
	struct rpc_task *t;

	INIT_LIST_HEAD(&task->u.tk_wait.links);
	q = &queue->tasks[task->tk_priority];
	if (unlikely(task->tk_priority > queue->maxpriority))
		q = &queue->tasks[queue->maxpriority];
	list_for_each_entry(t, q, u.tk_wait.list) {
		if (t->tk_cookie == task->tk_cookie) {
			list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
			return;
		}
	}
	list_add_tail(&task->u.tk_wait.list, q);
}

/*
 * Add new request to wait queue.
 *
 * Swapper tasks always get inserted at the head of the queue.
 * This should avoid many nasty memory deadlocks and hopefully
 * improve overall performance.
 * Everyone else gets appended to the queue to ensure proper FIFO behavior.
 */
static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
{
	BUG_ON (RPC_IS_QUEUED(task));

	if (RPC_IS_PRIORITY(queue))
		__rpc_add_wait_queue_priority(queue, task);
	else if (RPC_IS_SWAPPER(task))
		list_add(&task->u.tk_wait.list, &queue->tasks[0]);
	else
		list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
	task->u.tk_wait.rpc_waitq = queue;
	rpc_set_queued(task);

	dprintk("RPC: %4d added to queue %p \"%s\"\n",
				task->tk_pid, queue, rpc_qname(queue));
}

/*
 * Remove request from a priority queue.
 */
static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
{
	struct rpc_task *t;

	if (!list_empty(&task->u.tk_wait.links)) {
		t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.tk_wait.list);
		list_move(&t->u.tk_wait.list, &task->u.tk_wait.list);
		list_splice_init(&task->u.tk_wait.links, &t->u.tk_wait.links);
	}
	list_del(&task->u.tk_wait.list);
}

/*
 * Remove request from queue.
 * Note: must be called with spin lock held.
 */
static void __rpc_remove_wait_queue(struct rpc_task *task)
{
	struct rpc_wait_queue *queue;
	queue = task->u.tk_wait.rpc_waitq;

	if (RPC_IS_PRIORITY(queue))
		__rpc_remove_wait_queue_priority(task);
	else
		list_del(&task->u.tk_wait.list);
	dprintk("RPC: %4d removed from queue %p \"%s\"\n",
				task->tk_pid, queue, rpc_qname(queue));
}

static inline void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
{
	queue->priority = priority;
	queue->count = 1 << (priority * 2);
}

static inline void rpc_set_waitqueue_cookie(struct rpc_wait_queue *queue, unsigned long cookie)
{
	queue->cookie = cookie;
	queue->nr = RPC_BATCH_COUNT;
}

static inline void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
{
	rpc_set_waitqueue_priority(queue, queue->maxpriority);
	rpc_set_waitqueue_cookie(queue, 0);
}

static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, int maxprio)
{
	int i;

	spin_lock_init(&queue->lock);
	for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
		INIT_LIST_HEAD(&queue->tasks[i]);
	queue->maxpriority = maxprio;
	rpc_reset_waitqueue_priority(queue);
#ifdef RPC_DEBUG
	queue->name = qname;
#endif
}

void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
{
	__rpc_init_priority_wait_queue(queue, qname, RPC_PRIORITY_HIGH);
}

void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
{
	__rpc_init_priority_wait_queue(queue, qname, 0);
}
EXPORT_SYMBOL(rpc_init_wait_queue);

/*
 * Make an RPC task runnable.
 *
 * Note: If the task is ASYNC, this must be called with 
 * the spinlock held to protect the wait queue operation.
 */
static void rpc_make_runnable(struct rpc_task *task)
{
	int do_ret;

	BUG_ON(task->tk_timeout_fn);
	do_ret = rpc_test_and_set_running(task);
	rpc_clear_queued(task);
	if (do_ret)
		return;
	if (RPC_IS_ASYNC(task)) {
		int status;

		INIT_WORK(&task->u.tk_work, rpc_async_schedule, (void *)task);
		status = queue_work(task->tk_workqueue, &task->u.tk_work);
		if (status < 0) {
			printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
			task->tk_status = status;
			return;
		}
	} else
		wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
}

/*
 * Place a newly initialized task on the workqueue.
 */
static inline void
rpc_schedule_run(struct rpc_task *task)
{
	/* Don't run a child twice! */
	if (RPC_IS_ACTIVATED(task))
		return;
	task->tk_active = 1;
	rpc_make_runnable(task);
}

/*
 * Prepare for sleeping on a wait queue.
 * By always appending tasks to the list we ensure FIFO behavior.
 * NB: An RPC task will only receive interrupt-driven events as long
 * as it's on a wait queue.
 */
static void __rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
			rpc_action action, rpc_action timer)
{
	dprintk("RPC: %4d sleep_on(queue \"%s\" time %ld)\n", task->tk_pid,
				rpc_qname(q), jiffies);

	if (!RPC_IS_ASYNC(task) && !RPC_IS_ACTIVATED(task)) {
		printk(KERN_ERR "RPC: Inactive synchronous task put to sleep!\n");
		return;
	}

	/* Mark the task as being activated if so needed */
	if (!RPC_IS_ACTIVATED(task))
		task->tk_active = 1;

	__rpc_add_wait_queue(q, task);

	BUG_ON(task->tk_callback != NULL);
	task->tk_callback = action;
	__rpc_add_timer(task, timer);
}

void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
				rpc_action action, rpc_action timer)
{
	/*
	 * Protect the queue operations.
	 */
	spin_lock_bh(&q->lock);
	__rpc_sleep_on(q, task, action, timer);
	spin_unlock_bh(&q->lock);
}

/**
 * __rpc_do_wake_up_task - wake up a single rpc_task
 * @task: task to be woken up
 *
 * Caller must hold queue->lock, and have cleared the task queued flag.
 */
static void __rpc_do_wake_up_task(struct rpc_task *task)
{
	dprintk("RPC: %4d __rpc_wake_up_task (now %ld)\n", task->tk_pid, jiffies);

#ifdef RPC_DEBUG
	BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif
	/* Has the task been executed yet? If not, we cannot wake it up! */
	if (!RPC_IS_ACTIVATED(task)) {
		printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
		return;
	}

	__rpc_disable_timer(task);
	__rpc_remove_wait_queue(task);

	rpc_make_runnable(task);

	dprintk("RPC:      __rpc_wake_up_task done\n");
}

/*
 * Wake up the specified task
 */
static void __rpc_wake_up_task(struct rpc_task *task)
{
	if (rpc_start_wakeup(task)) {
		if (RPC_IS_QUEUED(task))
			__rpc_do_wake_up_task(task);
		rpc_finish_wakeup(task);
	}
}

/*
 * Default timeout handler if none specified by user
 */
static void
__rpc_default_timer(struct rpc_task *task)
{
	dprintk("RPC: %d timeout (default timer)\n", task->tk_pid);
	task->tk_status = -ETIMEDOUT;
	rpc_wake_up_task(task);
}

/*
 * Wake up the specified task
 */
void rpc_wake_up_task(struct rpc_task *task)
{
	if (rpc_start_wakeup(task)) {
		if (RPC_IS_QUEUED(task)) {
			struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;

			spin_lock_bh(&queue->lock);
			__rpc_do_wake_up_task(task);
			spin_unlock_bh(&queue->lock);
		}
		rpc_finish_wakeup(task);
	}
}

/*
 * Wake up the next task on a priority queue.
 */
static struct rpc_task * __rpc_wake_up_next_priority(struct rpc_wait_queue *queue)
{
	struct list_head *q;
	struct rpc_task *task;

	/*
	 * Service a batch of tasks from a single cookie.
	 */
	q = &queue->tasks[queue->priority];
	if (!list_empty(q)) {
		task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
		if (queue->cookie == task->tk_cookie) {
			if (--queue->nr)
				goto out;
			list_move_tail(&task->u.tk_wait.list, q);
		}
		/*
		 * Check if we need to switch queues.
		 */
		if (--queue->count)
			goto new_cookie;
	}

	/*
	 * Service the next queue.
	 */
	do {
		if (q == &queue->tasks[0])
			q = &queue->tasks[queue->maxpriority];
		else
			q = q - 1;
		if (!list_empty(q)) {
			task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
			goto new_queue;
		}
	} while (q != &queue->tasks[queue->priority]);

	rpc_reset_waitqueue_priority(queue);
	return NULL;

new_queue:
	rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
new_cookie:
	rpc_set_waitqueue_cookie(queue, task->tk_cookie);
out:
	__rpc_wake_up_task(task);
	return task;
}

/*
 * Wake up the next task on the wait queue.
 */
struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
{
	struct rpc_task	*task = NULL;

	dprintk("RPC:      wake_up_next(%p \"%s\")\n", queue, rpc_qname(queue));
	spin_lock_bh(&queue->lock);
	if (RPC_IS_PRIORITY(queue))
		task = __rpc_wake_up_next_priority(queue);
	else {
		task_for_first(task, &queue->tasks[0])
			__rpc_wake_up_task(task);
	}
	spin_unlock_bh(&queue->lock);

	return task;
}

/**
 * rpc_wake_up - wake up all rpc_tasks
 * @queue: rpc_wait_queue on which the tasks are sleeping
 *
 * Grabs queue->lock
 */
void rpc_wake_up(struct rpc_wait_queue *queue)
{
	struct rpc_task *task;

	struct list_head *head;
	spin_lock_bh(&queue->lock);
	head = &queue->tasks[queue->maxpriority];
	for (;;) {
		while (!list_empty(head)) {
			task = list_entry(head->next, struct rpc_task, u.tk_wait.list);
			__rpc_wake_up_task(task);
		}
		if (head == &queue->tasks[0])
			break;
		head--;
	}
	spin_unlock_bh(&queue->lock);
}

/**
 * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
 * @queue: rpc_wait_queue on which the tasks are sleeping
 * @status: status value to set
 *
 * Grabs queue->lock
 */
void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
{
	struct list_head *head;
	struct rpc_task *task;

	spin_lock_bh(&queue->lock);
	head = &queue->tasks[queue->maxpriority];
	for (;;) {
		while (!list_empty(head)) {
			task = list_entry(head->next, struct rpc_task, u.tk_wait.list);
			task->tk_status = status;
			__rpc_wake_up_task(task);
		}
		if (head == &queue->tasks[0])
			break;
		head--;
	}
	spin_unlock_bh(&queue->lock);
}

/*
 * Run a task at a later time
 */
static void	__rpc_atrun(struct rpc_task *);
void
rpc_delay(struct rpc_task *task, unsigned long delay)
{
	task->tk_timeout = delay;
	rpc_sleep_on(&delay_queue, task, NULL, __rpc_atrun);
}

static void
__rpc_atrun(struct rpc_task *task)
{
	task->tk_status = 0;
	rpc_wake_up_task(task);
}

/*
 * Helper that calls task->tk_exit if it exists and then returns
 * true if we should exit __rpc_execute.
 */
static inline int __rpc_do_exit(struct rpc_task *task)
{
	if (task->tk_exit != NULL) {
		lock_kernel();
		task->tk_exit(task);
		unlock_kernel();
		/* If tk_action is non-null, we should restart the call */
		if (task->tk_action != NULL) {
			if (!RPC_ASSASSINATED(task)) {
				/* Release RPC slot and buffer memory */
				xprt_release(task);
				rpc_free(task);
				return 0;
			}
			printk(KERN_ERR "RPC: dead task tried to walk away.\n");
		}
	}
	return 1;
}

static int rpc_wait_bit_interruptible(void *word)
{
	if (signal_pending(current))
		return -ERESTARTSYS;
	schedule();
	return 0;
}

/*
 * This is the RPC `scheduler' (or rather, the finite state machine).
 */
static int __rpc_execute(struct rpc_task *task)
{
	int		status = 0;

	dprintk("RPC: %4d rpc_execute flgs %x\n",
				task->tk_pid, task->tk_flags);

	BUG_ON(RPC_IS_QUEUED(task));

	for (;;) {
		/*
		 * Garbage collection of pending timers...
		 */
		rpc_delete_timer(task);

		/*
		 * Execute any pending callback.
		 */
		if (RPC_DO_CALLBACK(task)) {
			/* Define a callback save pointer */
			void (*save_callback)(struct rpc_task *);
	
			/* 
			 * If a callback exists, save it, reset it,
			 * call it.
			 * The save is needed to stop from resetting
			 * another callback set within the callback handler
			 * - Dave
			 */
			save_callback=task->tk_callback;
			task->tk_callback=NULL;
			lock_kernel();
			save_callback(task);
			unlock_kernel();
		}

		/*
		 * Perform the next FSM step.
		 * tk_action may be NULL when the task has been killed
		 * by someone else.
		 */
		if (!RPC_IS_QUEUED(task)) {
			if (task->tk_action != NULL) {
				lock_kernel();
				task->tk_action(task);
				unlock_kernel();
			} else if (__rpc_do_exit(task))
				break;
		}

		/*
		 * Lockless check for whether task is sleeping or not.
		 */
		if (!RPC_IS_QUEUED(task))
			continue;
		rpc_clear_running(task);
		if (RPC_IS_ASYNC(task)) {
			/* Careful! we may have raced... */
			if (RPC_IS_QUEUED(task))
				return 0;
			if (rpc_test_and_set_running(task))
				return 0;
			continue;
		}

		/* sync task: sleep here */
		dprintk("RPC: %4d sync task going to sleep\n", task->tk_pid);
		/* Note: Caller should be using rpc_clnt_sigmask() */
		status = out_of_line_wait_on_bit(&task->tk_runstate,
				RPC_TASK_QUEUED, rpc_wait_bit_interruptible,
				TASK_INTERRUPTIBLE);
		if (status == -ERESTARTSYS) {
			/*
			 * When a sync task receives a signal, it exits with
			 * -ERESTARTSYS. In order to catch any callbacks that
			 * clean up after sleeping on some queue, we don't
			 * break the loop here, but go around once more.
			 */
			dprintk("RPC: %4d got signal\n", task->tk_pid);
			task->tk_flags |= RPC_TASK_KILLED;
			rpc_exit(task, -ERESTARTSYS);
			rpc_wake_up_task(task);
		}
		rpc_set_running(task);
		dprintk("RPC: %4d sync task resuming\n", task->tk_pid);
	}

	dprintk("RPC: %4d exit() = %d\n", task->tk_pid, task->tk_status);
	status = task->tk_status;

	/* Release all resources associated with the task */
	rpc_release_task(task);
	return status;
}

/*
 * User-visible entry point to the scheduler.
 *
 * This may be called recursively if e.g. an async NFS task updates
 * the attributes and finds that dirty pages must be flushed.
 * NOTE: Upon exit of this function the task is guaranteed to be
 *	 released. In particular note that tk_release() will have
 *	 been called, so your task memory may have been freed.
 */
int
rpc_execute(struct rpc_task *task)
{
	BUG_ON(task->tk_active);

	task->tk_active = 1;
	rpc_set_running(task);
	return __rpc_execute(task);
}

static void rpc_async_schedule(void *arg)
{
	__rpc_execute((struct rpc_task *)arg);
}

/*
 * Allocate memory for RPC purposes.
 *
 * We try to ensure that some NFS reads and writes can always proceed
 * by using a mempool when allocating 'small' buffers.
 * In order to avoid memory starvation triggering more writebacks of
 * NFS requests, we use GFP_NOFS rather than GFP_KERNEL.
 */
void *
rpc_malloc(struct rpc_task *task, size_t size)
{
	int	gfp;

	if (task->tk_flags & RPC_TASK_SWAPPER)
		gfp = GFP_ATOMIC;
	else
		gfp = GFP_NOFS;

	if (size > RPC_BUFFER_MAXSIZE) {
		task->tk_buffer =  kmalloc(size, gfp);
		if (task->tk_buffer)
			task->tk_bufsize = size;
	} else {
		task->tk_buffer =  mempool_alloc(rpc_buffer_mempool, gfp);
		if (task->tk_buffer)
			task->tk_bufsize = RPC_BUFFER_MAXSIZE;
	}
	return task->tk_buffer;
}

static void
rpc_free(struct rpc_task *task)
{
	if (task->tk_buffer) {
		if (task->tk_bufsize == RPC_BUFFER_MAXSIZE)
			mempool_free(task->tk_buffer, rpc_buffer_mempool);
		else
			kfree(task->tk_buffer);
		task->tk_buffer = NULL;
		task->tk_bufsize = 0;
	}
}

/*
 * Creation and deletion of RPC task structures
 */
void rpc_init_task(struct rpc_task *task, struct rpc_clnt *clnt, rpc_action callback, int flags)
{
	memset(task, 0, sizeof(*task));
	init_timer(&task->tk_timer);
	task->tk_timer.data     = (unsigned long) task;
	task->tk_timer.function = (void (*)(unsigned long)) rpc_run_timer;
	task->tk_client = clnt;
	task->tk_flags  = flags;
	task->tk_exit   = callback;

	/* Initialize retry counters */
	task->tk_garb_retry = 2;
	task->tk_cred_retry = 2;

	task->tk_priority = RPC_PRIORITY_NORMAL;
	task->tk_cookie = (unsigned long)current;

	/* Initialize workqueue for async tasks */
	task->tk_workqueue = rpciod_workqueue;

	if (clnt) {
		atomic_inc(&clnt->cl_users);
		if (clnt->cl_softrtry)
			task->tk_flags |= RPC_TASK_SOFT;
		if (!clnt->cl_intr)
			task->tk_flags |= RPC_TASK_NOINTR;
	}

#ifdef RPC_DEBUG
	task->tk_magic = RPC_TASK_MAGIC_ID;
	task->tk_pid = rpc_task_id++;
#endif
	/* Add to global list of all tasks */
	spin_lock(&rpc_sched_lock);
	list_add_tail(&task->tk_task, &all_tasks);
	spin_unlock(&rpc_sched_lock);

	dprintk("RPC: %4d new task procpid %d\n", task->tk_pid,
				current->pid);
}

static struct rpc_task *
rpc_alloc_task(void)
{
	return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
}

static void
rpc_default_free_task(struct rpc_task *task)
{
	dprintk("RPC: %4d freeing task\n", task->tk_pid);
	mempool_free(task, rpc_task_mempool);
}

/*
 * Create a new task for the specified client.  We have to
 * clean up after an allocation failure, as the client may
 * have specified "oneshot".
 */
struct rpc_task *
rpc_new_task(struct rpc_clnt *clnt, rpc_action callback, int flags)
{
	struct rpc_task	*task;

	task = rpc_alloc_task();
	if (!task)
		goto cleanup;

	rpc_init_task(task, clnt, callback, flags);

	/* Replace tk_release */
	task->tk_release = rpc_default_free_task;

	dprintk("RPC: %4d allocated task\n", task->tk_pid);
	task->tk_flags |= RPC_TASK_DYNAMIC;
out:
	return task;

cleanup:
	/* Check whether to release the client */
	if (clnt) {
		printk("rpc_new_task: failed, users=%d, oneshot=%d\n",
			atomic_read(&clnt->cl_users), clnt->cl_oneshot);
		atomic_inc(&clnt->cl_users); /* pretend we were used ... */
		rpc_release_client(clnt);
	}
	goto out;
}

void rpc_release_task(struct rpc_task *task)
{
	dprintk("RPC: %4d release task\n", task->tk_pid);

#ifdef RPC_DEBUG
	BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif

	/* Remove from global task list */
	spin_lock(&rpc_sched_lock);
	list_del(&task->tk_task);
	spin_unlock(&rpc_sched_lock);

	BUG_ON (RPC_IS_QUEUED(task));
	task->tk_active = 0;

	/* Synchronously delete any running timer */
	rpc_delete_timer(task);

	/* Release resources */
	if (task->tk_rqstp)
		xprt_release(task);
	if (task->tk_msg.rpc_cred)
		rpcauth_unbindcred(task);
	rpc_free(task);
	if (task->tk_client) {
		rpc_release_client(task->tk_client);
		task->tk_client = NULL;
	}

#ifdef RPC_DEBUG
	task->tk_magic = 0;
#endif
	if (task->tk_release)
		task->tk_release(task);
}

/**
 * rpc_find_parent - find the parent of a child task.
 * @child: child task
 *
 * Checks that the parent task is still sleeping on the
 * queue 'childq'. If so returns a pointer to the parent.
 * Upon failure returns NULL.
 *
 * Caller must hold childq.lock
 */
static inline struct rpc_task *rpc_find_parent(struct rpc_task *child)
{
	struct rpc_task	*task, *parent;
	struct list_head *le;

	parent = (struct rpc_task *) child->tk_calldata;
	task_for_each(task, le, &childq.tasks[0])
		if (task == parent)
			return parent;

	return NULL;
}

static void rpc_child_exit(struct rpc_task *child)
{
	struct rpc_task	*parent;

	spin_lock_bh(&childq.lock);
	if ((parent = rpc_find_parent(child)) != NULL) {
		parent->tk_status = child->tk_status;
		__rpc_wake_up_task(parent);
	}
	spin_unlock_bh(&childq.lock);
}

/*
 * Note: rpc_new_task releases the client after a failure.
 */
struct rpc_task *
rpc_new_child(struct rpc_clnt *clnt, struct rpc_task *parent)
{
	struct rpc_task	*task;

	task = rpc_new_task(clnt, NULL, RPC_TASK_ASYNC | RPC_TASK_CHILD);
	if (!task)
		goto fail;
	task->tk_exit = rpc_child_exit;
	task->tk_calldata = parent;
	return task;

fail:
	parent->tk_status = -ENOMEM;
	return NULL;
}

void rpc_run_child(struct rpc_task *task, struct rpc_task *child, rpc_action func)
{
	spin_lock_bh(&childq.lock);
	/* N.B. Is it possible for the child to have already finished? */
	__rpc_sleep_on(&childq, task, func, NULL);
	rpc_schedule_run(child);
	spin_unlock_bh(&childq.lock);
}

/*
 * Kill all tasks for the given client.
 * XXX: kill their descendants as well?
 */
void rpc_killall_tasks(struct rpc_clnt *clnt)
{
	struct rpc_task	*rovr;
	struct list_head *le;

	dprintk("RPC:      killing all tasks for client %p\n", clnt);

	/*
	 * Spin lock all_tasks to prevent changes...
	 */
	spin_lock(&rpc_sched_lock);
	alltask_for_each(rovr, le, &all_tasks) {
		if (! RPC_IS_ACTIVATED(rovr))
			continue;
		if (!clnt || rovr->tk_client == clnt) {
			rovr->tk_flags |= RPC_TASK_KILLED;
			rpc_exit(rovr, -EIO);
			rpc_wake_up_task(rovr);
		}
	}
	spin_unlock(&rpc_sched_lock);
}

static DECLARE_MUTEX_LOCKED(rpciod_running);

static void rpciod_killall(void)
{
	unsigned long flags;

	while (!list_empty(&all_tasks)) {
		clear_thread_flag(TIF_SIGPENDING);
		rpc_killall_tasks(NULL);
		flush_workqueue(rpciod_workqueue);
		if (!list_empty(&all_tasks)) {
			dprintk("rpciod_killall: waiting for tasks to exit\n");
			yield();
		}
	}

	spin_lock_irqsave(&current->sighand->siglock, flags);
	recalc_sigpending();
	spin_unlock_irqrestore(&current->sighand->siglock, flags);
}

/*
 * Start up the rpciod process if it's not already running.
 */
int
rpciod_up(void)
{
	struct workqueue_struct *wq;
	int error = 0;

	down(&rpciod_sema);
	dprintk("rpciod_up: users %d\n", rpciod_users);
	rpciod_users++;
	if (rpciod_workqueue)
		goto out;
	/*
	 * If there's no pid, we should be the first user.
	 */
	if (rpciod_users > 1)
		printk(KERN_WARNING "rpciod_up: no workqueue, %d users??\n", rpciod_users);
	/*
	 * Create the rpciod thread and wait for it to start.
	 */
	error = -ENOMEM;
	wq = create_workqueue("rpciod");
	if (wq == NULL) {
		printk(KERN_WARNING "rpciod_up: create workqueue failed, error=%d\n", error);
		rpciod_users--;
		goto out;
	}
	rpciod_workqueue = wq;
	error = 0;
out:
	up(&rpciod_sema);
	return error;
}

void
rpciod_down(void)
{
	down(&rpciod_sema);
	dprintk("rpciod_down sema %d\n", rpciod_users);
	if (rpciod_users) {
		if (--rpciod_users)
			goto out;
	} else
		printk(KERN_WARNING "rpciod_down: no users??\n");

	if (!rpciod_workqueue) {
		dprintk("rpciod_down: Nothing to do!\n");
		goto out;
	}
	rpciod_killall();

	destroy_workqueue(rpciod_workqueue);
	rpciod_workqueue = NULL;
 out:
	up(&rpciod_sema);
}

#ifdef RPC_DEBUG
void rpc_show_tasks(void)
{
	struct list_head *le;
	struct rpc_task *t;

	spin_lock(&rpc_sched_lock);
	if (list_empty(&all_tasks)) {
		spin_unlock(&rpc_sched_lock);
		return;
	}
	printk("-pid- proc flgs status -client- -prog- --rqstp- -timeout "
		"-rpcwait -action- --exit--\n");
	alltask_for_each(t, le, &all_tasks) {
		const char *rpc_waitq = "none";

		if (RPC_IS_QUEUED(t))
			rpc_waitq = rpc_qname(t->u.tk_wait.rpc_waitq);

		printk("%05d %04d %04x %06d %8p %6d %8p %08ld %8s %8p %8p\n",
			t->tk_pid,
			(t->tk_msg.rpc_proc ? t->tk_msg.rpc_proc->p_proc : -1),
			t->tk_flags, t->tk_status,
			t->tk_client,
			(t->tk_client ? t->tk_client->cl_prog : 0),
			t->tk_rqstp, t->tk_timeout,
			rpc_waitq,
			t->tk_action, t->tk_exit);
	}
	spin_unlock(&rpc_sched_lock);
}
#endif

void
rpc_destroy_mempool(void)
{
	if (rpc_buffer_mempool)
		mempool_destroy(rpc_buffer_mempool);
	if (rpc_task_mempool)
		mempool_destroy(rpc_task_mempool);
	if (rpc_task_slabp && kmem_cache_destroy(rpc_task_slabp))
		printk(KERN_INFO "rpc_task: not all structures were freed\n");
	if (rpc_buffer_slabp && kmem_cache_destroy(rpc_buffer_slabp))
		printk(KERN_INFO "rpc_buffers: not all structures were freed\n");
}

int
rpc_init_mempool(void)
{
	rpc_task_slabp = kmem_cache_create("rpc_tasks",
					     sizeof(struct rpc_task),
					     0, SLAB_HWCACHE_ALIGN,
					     NULL, NULL);
	if (!rpc_task_slabp)
		goto err_nomem;
	rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
					     RPC_BUFFER_MAXSIZE,
					     0, SLAB_HWCACHE_ALIGN,
					     NULL, NULL);
	if (!rpc_buffer_slabp)
		goto err_nomem;
	rpc_task_mempool = mempool_create(RPC_TASK_POOLSIZE,
					    mempool_alloc_slab,
					    mempool_free_slab,
					    rpc_task_slabp);
	if (!rpc_task_mempool)
		goto err_nomem;
	rpc_buffer_mempool = mempool_create(RPC_BUFFER_POOLSIZE,
					    mempool_alloc_slab,
					    mempool_free_slab,
					    rpc_buffer_slabp);
	if (!rpc_buffer_mempool)
		goto err_nomem;
	return 0;
err_nomem:
	rpc_destroy_mempool();
	return -ENOMEM;
}