summaryrefslogtreecommitdiff
path: root/kernel/torture.c
blob: bbf6d473e50c1480a110c8f0edb5f941e317967b (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
/*
 * Common functions for in-kernel torture tests.
 *
 * 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 of the License, 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, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright (C) IBM Corporation, 2014
 *
 * Author: Paul E. McKenney <paulmck@us.ibm.com>
 *	Based on kernel/rcu/torture.c.
 */

#define pr_fmt(fmt) fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/trace_clock.h>
#include <linux/ktime.h>
#include <asm/byteorder.h>
#include <linux/torture.h>
#include "rcu/rcu.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");

static char *torture_type;
static int verbose;

/* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
#define FULLSTOP_DONTSTOP 0	/* Normal operation. */
#define FULLSTOP_SHUTDOWN 1	/* System shutdown with torture running. */
#define FULLSTOP_RMMOD    2	/* Normal rmmod of torture. */
static int fullstop = FULLSTOP_RMMOD;
static DEFINE_MUTEX(fullstop_mutex);

#ifdef CONFIG_HOTPLUG_CPU

/*
 * Variables for online-offline handling.  Only present if CPU hotplug
 * is enabled, otherwise does nothing.
 */

static struct task_struct *onoff_task;
static long onoff_holdoff;
static long onoff_interval;
static long n_offline_attempts;
static long n_offline_successes;
static unsigned long sum_offline;
static int min_offline = -1;
static int max_offline;
static long n_online_attempts;
static long n_online_successes;
static unsigned long sum_online;
static int min_online = -1;
static int max_online;

/*
 * Attempt to take a CPU offline.  Return false if the CPU is already
 * offline or if it is not subject to CPU-hotplug operations.  The
 * caller can detect other failures by looking at the statistics.
 */
bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
		     unsigned long *sum_offl, int *min_offl, int *max_offl)
{
	unsigned long delta;
	int ret;
	unsigned long starttime;

	if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
		return false;

	if (verbose > 1)
		pr_alert("%s" TORTURE_FLAG
			 "torture_onoff task: offlining %d\n",
			 torture_type, cpu);
	starttime = jiffies;
	(*n_offl_attempts)++;
	ret = cpu_down(cpu);
	if (ret) {
		if (verbose)
			pr_alert("%s" TORTURE_FLAG
				 "torture_onoff task: offline %d failed: errno %d\n",
				 torture_type, cpu, ret);
	} else {
		if (verbose > 1)
			pr_alert("%s" TORTURE_FLAG
				 "torture_onoff task: offlined %d\n",
				 torture_type, cpu);
		(*n_offl_successes)++;
		delta = jiffies - starttime;
		*sum_offl += delta;
		if (*min_offl < 0) {
			*min_offl = delta;
			*max_offl = delta;
		}
		if (*min_offl > delta)
			*min_offl = delta;
		if (*max_offl < delta)
			*max_offl = delta;
	}

	return true;
}
EXPORT_SYMBOL_GPL(torture_offline);

/*
 * Attempt to bring a CPU online.  Return false if the CPU is already
 * online or if it is not subject to CPU-hotplug operations.  The
 * caller can detect other failures by looking at the statistics.
 */
bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
		    unsigned long *sum_onl, int *min_onl, int *max_onl)
{
	unsigned long delta;
	int ret;
	unsigned long starttime;

	if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
		return false;

	if (verbose > 1)
		pr_alert("%s" TORTURE_FLAG
			 "torture_onoff task: onlining %d\n",
			 torture_type, cpu);
	starttime = jiffies;
	(*n_onl_attempts)++;
	ret = cpu_up(cpu);
	if (ret) {
		if (verbose)
			pr_alert("%s" TORTURE_FLAG
				 "torture_onoff task: online %d failed: errno %d\n",
				 torture_type, cpu, ret);
	} else {
		if (verbose > 1)
			pr_alert("%s" TORTURE_FLAG
				 "torture_onoff task: onlined %d\n",
				 torture_type, cpu);
		(*n_onl_successes)++;
		delta = jiffies - starttime;
		*sum_onl += delta;
		if (*min_onl < 0) {
			*min_onl = delta;
			*max_onl = delta;
		}
		if (*min_onl > delta)
			*min_onl = delta;
		if (*max_onl < delta)
			*max_onl = delta;
	}

	return true;
}
EXPORT_SYMBOL_GPL(torture_online);

/*
 * Execute random CPU-hotplug operations at the interval specified
 * by the onoff_interval.
 */
static int
torture_onoff(void *arg)
{
	int cpu;
	int maxcpu = -1;
	DEFINE_TORTURE_RANDOM(rand);
	int ret;

	VERBOSE_TOROUT_STRING("torture_onoff task started");
	for_each_online_cpu(cpu)
		maxcpu = cpu;
	WARN_ON(maxcpu < 0);
	if (!IS_MODULE(CONFIG_TORTURE_TEST))
		for_each_possible_cpu(cpu) {
			if (cpu_online(cpu))
				continue;
			ret = cpu_up(cpu);
			if (ret && verbose) {
				pr_alert("%s" TORTURE_FLAG
					 "%s: Initial online %d: errno %d\n",
					 __func__, torture_type, cpu, ret);
			}
		}

	if (maxcpu == 0) {
		VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
		goto stop;
	}

	if (onoff_holdoff > 0) {
		VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
		schedule_timeout_interruptible(onoff_holdoff);
		VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
	}
	while (!torture_must_stop()) {
		cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
		if (!torture_offline(cpu,
				     &n_offline_attempts, &n_offline_successes,
				     &sum_offline, &min_offline, &max_offline))
			torture_online(cpu,
				       &n_online_attempts, &n_online_successes,
				       &sum_online, &min_online, &max_online);
		schedule_timeout_interruptible(onoff_interval);
	}

stop:
	torture_kthread_stopping("torture_onoff");
	return 0;
}

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

/*
 * Initiate online-offline handling.
 */
int torture_onoff_init(long ooholdoff, long oointerval)
{
#ifdef CONFIG_HOTPLUG_CPU
	onoff_holdoff = ooholdoff;
	onoff_interval = oointerval;
	if (onoff_interval <= 0)
		return 0;
	return torture_create_kthread(torture_onoff, NULL, onoff_task);
#else /* #ifdef CONFIG_HOTPLUG_CPU */
	return 0;
#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
}
EXPORT_SYMBOL_GPL(torture_onoff_init);

/*
 * Clean up after online/offline testing.
 */
static void torture_onoff_cleanup(void)
{
#ifdef CONFIG_HOTPLUG_CPU
	if (onoff_task == NULL)
		return;
	VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
	kthread_stop(onoff_task);
	onoff_task = NULL;
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
}
EXPORT_SYMBOL_GPL(torture_onoff_cleanup);

/*
 * Print online/offline testing statistics.
 */
void torture_onoff_stats(void)
{
#ifdef CONFIG_HOTPLUG_CPU
	pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
		n_online_successes, n_online_attempts,
		n_offline_successes, n_offline_attempts,
		min_online, max_online,
		min_offline, max_offline,
		sum_online, sum_offline, HZ);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
}
EXPORT_SYMBOL_GPL(torture_onoff_stats);

/*
 * Were all the online/offline operations successful?
 */
bool torture_onoff_failures(void)
{
#ifdef CONFIG_HOTPLUG_CPU
	return n_online_successes != n_online_attempts ||
	       n_offline_successes != n_offline_attempts;
#else /* #ifdef CONFIG_HOTPLUG_CPU */
	return false;
#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
}
EXPORT_SYMBOL_GPL(torture_onoff_failures);

#define TORTURE_RANDOM_MULT	39916801  /* prime */
#define TORTURE_RANDOM_ADD	479001701 /* prime */
#define TORTURE_RANDOM_REFRESH	10000

/*
 * Crude but fast random-number generator.  Uses a linear congruential
 * generator, with occasional help from cpu_clock().
 */
unsigned long
torture_random(struct torture_random_state *trsp)
{
	if (--trsp->trs_count < 0) {
		trsp->trs_state += (unsigned long)local_clock();
		trsp->trs_count = TORTURE_RANDOM_REFRESH;
	}
	trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
		TORTURE_RANDOM_ADD;
	return swahw32(trsp->trs_state);
}
EXPORT_SYMBOL_GPL(torture_random);

/*
 * Variables for shuffling.  The idea is to ensure that each CPU stays
 * idle for an extended period to test interactions with dyntick idle,
 * as well as interactions with any per-CPU variables.
 */
struct shuffle_task {
	struct list_head st_l;
	struct task_struct *st_t;
};

static long shuffle_interval;	/* In jiffies. */
static struct task_struct *shuffler_task;
static cpumask_var_t shuffle_tmp_mask;
static int shuffle_idle_cpu;	/* Force all torture tasks off this CPU */
static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
static DEFINE_MUTEX(shuffle_task_mutex);

/*
 * Register a task to be shuffled.  If there is no memory, just splat
 * and don't bother registering.
 */
void torture_shuffle_task_register(struct task_struct *tp)
{
	struct shuffle_task *stp;

	if (WARN_ON_ONCE(tp == NULL))
		return;
	stp = kmalloc(sizeof(*stp), GFP_KERNEL);
	if (WARN_ON_ONCE(stp == NULL))
		return;
	stp->st_t = tp;
	mutex_lock(&shuffle_task_mutex);
	list_add(&stp->st_l, &shuffle_task_list);
	mutex_unlock(&shuffle_task_mutex);
}
EXPORT_SYMBOL_GPL(torture_shuffle_task_register);

/*
 * Unregister all tasks, for example, at the end of the torture run.
 */
static void torture_shuffle_task_unregister_all(void)
{
	struct shuffle_task *stp;
	struct shuffle_task *p;

	mutex_lock(&shuffle_task_mutex);
	list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
		list_del(&stp->st_l);
		kfree(stp);
	}
	mutex_unlock(&shuffle_task_mutex);
}

/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 * A special case is when shuffle_idle_cpu = -1, in which case we allow
 * the tasks to run on all CPUs.
 */
static void torture_shuffle_tasks(void)
{
	struct shuffle_task *stp;

	cpumask_setall(shuffle_tmp_mask);
	get_online_cpus();

	/* No point in shuffling if there is only one online CPU (ex: UP) */
	if (num_online_cpus() == 1) {
		put_online_cpus();
		return;
	}

	/* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
	shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
	if (shuffle_idle_cpu >= nr_cpu_ids)
		shuffle_idle_cpu = -1;
	else
		cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);

	mutex_lock(&shuffle_task_mutex);
	list_for_each_entry(stp, &shuffle_task_list, st_l)
		set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
	mutex_unlock(&shuffle_task_mutex);

	put_online_cpus();
}

/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 * system to become idle at a time and cut off its timer ticks. This is meant
 * to test the support for such tickless idle CPU in RCU.
 */
static int torture_shuffle(void *arg)
{
	VERBOSE_TOROUT_STRING("torture_shuffle task started");
	do {
		schedule_timeout_interruptible(shuffle_interval);
		torture_shuffle_tasks();
		torture_shutdown_absorb("torture_shuffle");
	} while (!torture_must_stop());
	torture_kthread_stopping("torture_shuffle");
	return 0;
}

/*
 * Start the shuffler, with shuffint in jiffies.
 */
int torture_shuffle_init(long shuffint)
{
	shuffle_interval = shuffint;

	shuffle_idle_cpu = -1;

	if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
		VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
		return -ENOMEM;
	}

	/* Create the shuffler thread */
	return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
}
EXPORT_SYMBOL_GPL(torture_shuffle_init);

/*
 * Stop the shuffling.
 */
static void torture_shuffle_cleanup(void)
{
	torture_shuffle_task_unregister_all();
	if (shuffler_task) {
		VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
		kthread_stop(shuffler_task);
		free_cpumask_var(shuffle_tmp_mask);
	}
	shuffler_task = NULL;
}
EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);

/*
 * Variables for auto-shutdown.  This allows "lights out" torture runs
 * to be fully scripted.
 */
static struct task_struct *shutdown_task;
static ktime_t shutdown_time;		/* time to system shutdown. */
static void (*torture_shutdown_hook)(void);

/*
 * Absorb kthreads into a kernel function that won't return, so that
 * they won't ever access module text or data again.
 */
void torture_shutdown_absorb(const char *title)
{
	while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
		pr_notice("torture thread %s parking due to system shutdown\n",
			  title);
		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
	}
}
EXPORT_SYMBOL_GPL(torture_shutdown_absorb);

/*
 * Cause the torture test to shutdown the system after the test has
 * run for the time specified by the shutdown_secs parameter.
 */
static int torture_shutdown(void *arg)
{
	ktime_t ktime_snap;

	VERBOSE_TOROUT_STRING("torture_shutdown task started");
	ktime_snap = ktime_get();
	while (ktime_before(ktime_snap, shutdown_time) &&
	       !torture_must_stop()) {
		if (verbose)
			pr_alert("%s" TORTURE_FLAG
				 "torture_shutdown task: %llu ms remaining\n",
				 torture_type,
				 ktime_ms_delta(shutdown_time, ktime_snap));
		set_current_state(TASK_INTERRUPTIBLE);
		schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
		ktime_snap = ktime_get();
	}
	if (torture_must_stop()) {
		torture_kthread_stopping("torture_shutdown");
		return 0;
	}

	/* OK, shut down the system. */

	VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
	shutdown_task = NULL;	/* Avoid self-kill deadlock. */
	if (torture_shutdown_hook)
		torture_shutdown_hook();
	else
		VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
	rcu_ftrace_dump(DUMP_ALL);
	kernel_power_off();	/* Shut down the system. */
	return 0;
}

/*
 * Start up the shutdown task.
 */
int torture_shutdown_init(int ssecs, void (*cleanup)(void))
{
	torture_shutdown_hook = cleanup;
	if (ssecs > 0) {
		shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
		return torture_create_kthread(torture_shutdown, NULL,
					     shutdown_task);
	}
	return 0;
}
EXPORT_SYMBOL_GPL(torture_shutdown_init);

/*
 * Detect and respond to a system shutdown.
 */
static int torture_shutdown_notify(struct notifier_block *unused1,
				   unsigned long unused2, void *unused3)
{
	mutex_lock(&fullstop_mutex);
	if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
		VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
		WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
	} else {
		pr_warn("Concurrent rmmod and shutdown illegal!\n");
	}
	mutex_unlock(&fullstop_mutex);
	return NOTIFY_DONE;
}

static struct notifier_block torture_shutdown_nb = {
	.notifier_call = torture_shutdown_notify,
};

/*
 * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 */
static void torture_shutdown_cleanup(void)
{
	unregister_reboot_notifier(&torture_shutdown_nb);
	if (shutdown_task != NULL) {
		VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
		kthread_stop(shutdown_task);
	}
	shutdown_task = NULL;
}

/*
 * Variables for stuttering, which means to periodically pause and
 * restart testing in order to catch bugs that appear when load is
 * suddenly applied to or removed from the system.
 */
static struct task_struct *stutter_task;
static int stutter_pause_test;
static int stutter;

/*
 * Block until the stutter interval ends.  This must be called periodically
 * by all running kthreads that need to be subject to stuttering.
 */
bool stutter_wait(const char *title)
{
	int spt;

	cond_resched_tasks_rcu_qs();
	spt = READ_ONCE(stutter_pause_test);
	for (; spt; spt = READ_ONCE(stutter_pause_test)) {
		if (spt == 1) {
			schedule_timeout_interruptible(1);
		} else if (spt == 2) {
			while (READ_ONCE(stutter_pause_test))
				cond_resched();
		} else {
			schedule_timeout_interruptible(round_jiffies_relative(HZ));
		}
		torture_shutdown_absorb(title);
	}
	return !!spt;
}
EXPORT_SYMBOL_GPL(stutter_wait);

/*
 * Cause the torture test to "stutter", starting and stopping all
 * threads periodically.
 */
static int torture_stutter(void *arg)
{
	VERBOSE_TOROUT_STRING("torture_stutter task started");
	do {
		if (!torture_must_stop() && stutter > 1) {
			WRITE_ONCE(stutter_pause_test, 1);
			schedule_timeout_interruptible(stutter - 1);
			WRITE_ONCE(stutter_pause_test, 2);
			schedule_timeout_interruptible(1);
		}
		WRITE_ONCE(stutter_pause_test, 0);
		if (!torture_must_stop())
			schedule_timeout_interruptible(stutter);
		torture_shutdown_absorb("torture_stutter");
	} while (!torture_must_stop());
	torture_kthread_stopping("torture_stutter");
	return 0;
}

/*
 * Initialize and kick off the torture_stutter kthread.
 */
int torture_stutter_init(const int s)
{
	stutter = s;
	return torture_create_kthread(torture_stutter, NULL, stutter_task);
}
EXPORT_SYMBOL_GPL(torture_stutter_init);

/*
 * Cleanup after the torture_stutter kthread.
 */
static void torture_stutter_cleanup(void)
{
	if (!stutter_task)
		return;
	VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
	kthread_stop(stutter_task);
	stutter_task = NULL;
}

/*
 * Initialize torture module.  Please note that this is -not- invoked via
 * the usual module_init() mechanism, but rather by an explicit call from
 * the client torture module.  This call must be paired with a later
 * torture_init_end().
 *
 * The runnable parameter points to a flag that controls whether or not
 * the test is currently runnable.  If there is no such flag, pass in NULL.
 */
bool torture_init_begin(char *ttype, int v)
{
	mutex_lock(&fullstop_mutex);
	if (torture_type != NULL) {
		pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
			 ttype, torture_type);
		pr_alert("torture_init_begin: One torture test at a time!\n");
		mutex_unlock(&fullstop_mutex);
		return false;
	}
	torture_type = ttype;
	verbose = v;
	fullstop = FULLSTOP_DONTSTOP;
	return true;
}
EXPORT_SYMBOL_GPL(torture_init_begin);

/*
 * Tell the torture module that initialization is complete.
 */
void torture_init_end(void)
{
	mutex_unlock(&fullstop_mutex);
	register_reboot_notifier(&torture_shutdown_nb);
}
EXPORT_SYMBOL_GPL(torture_init_end);

/*
 * Clean up torture module.  Please note that this is -not- invoked via
 * the usual module_exit() mechanism, but rather by an explicit call from
 * the client torture module.  Returns true if a race with system shutdown
 * is detected, otherwise, all kthreads started by functions in this file
 * will be shut down.
 *
 * This must be called before the caller starts shutting down its own
 * kthreads.
 *
 * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 * in order to correctly perform the cleanup. They are separated because
 * threads can still need to reference the torture_type type, thus nullify
 * only after completing all other relevant calls.
 */
bool torture_cleanup_begin(void)
{
	mutex_lock(&fullstop_mutex);
	if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
		pr_warn("Concurrent rmmod and shutdown illegal!\n");
		mutex_unlock(&fullstop_mutex);
		schedule_timeout_uninterruptible(10);
		return true;
	}
	WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
	mutex_unlock(&fullstop_mutex);
	torture_shutdown_cleanup();
	torture_shuffle_cleanup();
	torture_stutter_cleanup();
	torture_onoff_cleanup();
	return false;
}
EXPORT_SYMBOL_GPL(torture_cleanup_begin);

void torture_cleanup_end(void)
{
	mutex_lock(&fullstop_mutex);
	torture_type = NULL;
	mutex_unlock(&fullstop_mutex);
}
EXPORT_SYMBOL_GPL(torture_cleanup_end);

/*
 * Is it time for the current torture test to stop?
 */
bool torture_must_stop(void)
{
	return torture_must_stop_irq() || kthread_should_stop();
}
EXPORT_SYMBOL_GPL(torture_must_stop);

/*
 * Is it time for the current torture test to stop?  This is the irq-safe
 * version, hence no check for kthread_should_stop().
 */
bool torture_must_stop_irq(void)
{
	return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
}
EXPORT_SYMBOL_GPL(torture_must_stop_irq);

/*
 * Each kthread must wait for kthread_should_stop() before returning from
 * its top-level function, otherwise segfaults ensue.  This function
 * prints a "stopping" message and waits for kthread_should_stop(), and
 * should be called from all torture kthreads immediately prior to
 * returning.
 */
void torture_kthread_stopping(char *title)
{
	char buf[128];

	snprintf(buf, sizeof(buf), "Stopping %s", title);
	VERBOSE_TOROUT_STRING(buf);
	while (!kthread_should_stop()) {
		torture_shutdown_absorb(title);
		schedule_timeout_uninterruptible(1);
	}
}
EXPORT_SYMBOL_GPL(torture_kthread_stopping);

/*
 * Create a generic torture kthread that is immediately runnable.  If you
 * need the kthread to be stopped so that you can do something to it before
 * it starts, you will need to open-code your own.
 */
int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
			    char *f, struct task_struct **tp)
{
	int ret = 0;

	VERBOSE_TOROUT_STRING(m);
	*tp = kthread_run(fn, arg, "%s", s);
	if (IS_ERR(*tp)) {
		ret = PTR_ERR(*tp);
		VERBOSE_TOROUT_ERRSTRING(f);
		*tp = NULL;
	}
	torture_shuffle_task_register(*tp);
	return ret;
}
EXPORT_SYMBOL_GPL(_torture_create_kthread);

/*
 * Stop a generic kthread, emitting a message.
 */
void _torture_stop_kthread(char *m, struct task_struct **tp)
{
	if (*tp == NULL)
		return;
	VERBOSE_TOROUT_STRING(m);
	kthread_stop(*tp);
	*tp = NULL;
}
EXPORT_SYMBOL_GPL(_torture_stop_kthread);