projects/linux·blob v3.15 · refs

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1/*
2 * Common functions for in-kernel torture tests.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
17 *
18 * Copyright (C) IBM Corporation, 2014
19 *
20 * Author: Paul E. McKenney <[email protected]>
21 * Based on kernel/rcu/torture.c.
22 */
23#include <linux/types.h>
24#include <linux/kernel.h>
25#include <linux/init.h>
26#include <linux/module.h>
27#include <linux/kthread.h>
28#include <linux/err.h>
29#include <linux/spinlock.h>
30#include <linux/smp.h>
31#include <linux/interrupt.h>
32#include <linux/sched.h>
33#include <linux/atomic.h>
34#include <linux/bitops.h>
35#include <linux/completion.h>
36#include <linux/moduleparam.h>
37#include <linux/percpu.h>
38#include <linux/notifier.h>
39#include <linux/reboot.h>
40#include <linux/freezer.h>
41#include <linux/cpu.h>
42#include <linux/delay.h>
43#include <linux/stat.h>
44#include <linux/slab.h>
45#include <linux/trace_clock.h>
46#include <asm/byteorder.h>
47#include <linux/torture.h>
48
49MODULE_LICENSE("GPL");
50MODULE_AUTHOR("Paul E. McKenney <[email protected]>");
51
52static char *torture_type;
53static bool verbose;
54
55/* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */
56#define FULLSTOP_DONTSTOP 0 /* Normal operation. */
57#define FULLSTOP_SHUTDOWN 1 /* System shutdown with torture running. */
58#define FULLSTOP_RMMOD 2 /* Normal rmmod of torture. */
59static int fullstop = FULLSTOP_RMMOD;
60static DEFINE_MUTEX(fullstop_mutex);
61static int *torture_runnable;
62
63#ifdef CONFIG_HOTPLUG_CPU
64
65/*
66 * Variables for online-offline handling. Only present if CPU hotplug
67 * is enabled, otherwise does nothing.
68 */
69
70static struct task_struct *onoff_task;
71static long onoff_holdoff;
72static long onoff_interval;
73static long n_offline_attempts;
74static long n_offline_successes;
75static unsigned long sum_offline;
76static int min_offline = -1;
77static int max_offline;
78static long n_online_attempts;
79static long n_online_successes;
80static unsigned long sum_online;
81static int min_online = -1;
82static int max_online;
83
84/*
85 * Execute random CPU-hotplug operations at the interval specified
86 * by the onoff_interval.
87 */
88static int
89torture_onoff(void *arg)
90{
91 int cpu;
92 unsigned long delta;
93 int maxcpu = -1;
94 DEFINE_TORTURE_RANDOM(rand);
95 int ret;
96 unsigned long starttime;
97
98 VERBOSE_TOROUT_STRING("torture_onoff task started");
99 for_each_online_cpu(cpu)
100 maxcpu = cpu;
101 WARN_ON(maxcpu < 0);
102 if (onoff_holdoff > 0) {
103 VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
104 schedule_timeout_interruptible(onoff_holdoff);
105 VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
106 }
107 while (!torture_must_stop()) {
108 cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
109 if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
110 if (verbose)
111 pr_alert("%s" TORTURE_FLAG
112 "torture_onoff task: offlining %d\n",
113 torture_type, cpu);
114 starttime = jiffies;
115 n_offline_attempts++;
116 ret = cpu_down(cpu);
117 if (ret) {
118 if (verbose)
119 pr_alert("%s" TORTURE_FLAG
120 "torture_onoff task: offline %d failed: errno %d\n",
121 torture_type, cpu, ret);
122 } else {
123 if (verbose)
124 pr_alert("%s" TORTURE_FLAG
125 "torture_onoff task: offlined %d\n",
126 torture_type, cpu);
127 n_offline_successes++;
128 delta = jiffies - starttime;
129 sum_offline += delta;
130 if (min_offline < 0) {
131 min_offline = delta;
132 max_offline = delta;
133 }
134 if (min_offline > delta)
135 min_offline = delta;
136 if (max_offline < delta)
137 max_offline = delta;
138 }
139 } else if (cpu_is_hotpluggable(cpu)) {
140 if (verbose)
141 pr_alert("%s" TORTURE_FLAG
142 "torture_onoff task: onlining %d\n",
143 torture_type, cpu);
144 starttime = jiffies;
145 n_online_attempts++;
146 ret = cpu_up(cpu);
147 if (ret) {
148 if (verbose)
149 pr_alert("%s" TORTURE_FLAG
150 "torture_onoff task: online %d failed: errno %d\n",
151 torture_type, cpu, ret);
152 } else {
153 if (verbose)
154 pr_alert("%s" TORTURE_FLAG
155 "torture_onoff task: onlined %d\n",
156 torture_type, cpu);
157 n_online_successes++;
158 delta = jiffies - starttime;
159 sum_online += delta;
160 if (min_online < 0) {
161 min_online = delta;
162 max_online = delta;
163 }
164 if (min_online > delta)
165 min_online = delta;
166 if (max_online < delta)
167 max_online = delta;
168 }
169 }
170 schedule_timeout_interruptible(onoff_interval);
171 }
172 torture_kthread_stopping("torture_onoff");
173 return 0;
174}
175
176#endif /* #ifdef CONFIG_HOTPLUG_CPU */
177
178/*
179 * Initiate online-offline handling.
180 */
181int torture_onoff_init(long ooholdoff, long oointerval)
182{
183 int ret = 0;
184
185#ifdef CONFIG_HOTPLUG_CPU
186 onoff_holdoff = ooholdoff;
187 onoff_interval = oointerval;
188 if (onoff_interval <= 0)
189 return 0;
190 ret = torture_create_kthread(torture_onoff, NULL, onoff_task);
191#endif /* #ifdef CONFIG_HOTPLUG_CPU */
192 return ret;
193}
194EXPORT_SYMBOL_GPL(torture_onoff_init);
195
196/*
197 * Clean up after online/offline testing.
198 */
199static void torture_onoff_cleanup(void)
200{
201#ifdef CONFIG_HOTPLUG_CPU
202 if (onoff_task == NULL)
203 return;
204 VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
205 kthread_stop(onoff_task);
206 onoff_task = NULL;
207#endif /* #ifdef CONFIG_HOTPLUG_CPU */
208}
209EXPORT_SYMBOL_GPL(torture_onoff_cleanup);
210
211/*
212 * Print online/offline testing statistics.
213 */
214char *torture_onoff_stats(char *page)
215{
216#ifdef CONFIG_HOTPLUG_CPU
217 page += sprintf(page,
218 "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
219 n_online_successes, n_online_attempts,
220 n_offline_successes, n_offline_attempts,
221 min_online, max_online,
222 min_offline, max_offline,
223 sum_online, sum_offline, HZ);
224#endif /* #ifdef CONFIG_HOTPLUG_CPU */
225 return page;
226}
227EXPORT_SYMBOL_GPL(torture_onoff_stats);
228
229/*
230 * Were all the online/offline operations successful?
231 */
232bool torture_onoff_failures(void)
233{
234#ifdef CONFIG_HOTPLUG_CPU
235 return n_online_successes != n_online_attempts ||
236 n_offline_successes != n_offline_attempts;
237#else /* #ifdef CONFIG_HOTPLUG_CPU */
238 return false;
239#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
240}
241EXPORT_SYMBOL_GPL(torture_onoff_failures);
242
243#define TORTURE_RANDOM_MULT 39916801 /* prime */
244#define TORTURE_RANDOM_ADD 479001701 /* prime */
245#define TORTURE_RANDOM_REFRESH 10000
246
247/*
248 * Crude but fast random-number generator. Uses a linear congruential
249 * generator, with occasional help from cpu_clock().
250 */
251unsigned long
252torture_random(struct torture_random_state *trsp)
253{
254 if (--trsp->trs_count < 0) {
255 trsp->trs_state += (unsigned long)local_clock();
256 trsp->trs_count = TORTURE_RANDOM_REFRESH;
257 }
258 trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
259 TORTURE_RANDOM_ADD;
260 return swahw32(trsp->trs_state);
261}
262EXPORT_SYMBOL_GPL(torture_random);
263
264/*
265 * Variables for shuffling. The idea is to ensure that each CPU stays
266 * idle for an extended period to test interactions with dyntick idle,
267 * as well as interactions with any per-CPU varibles.
268 */
269struct shuffle_task {
270 struct list_head st_l;
271 struct task_struct *st_t;
272};
273
274static long shuffle_interval; /* In jiffies. */
275static struct task_struct *shuffler_task;
276static cpumask_var_t shuffle_tmp_mask;
277static int shuffle_idle_cpu; /* Force all torture tasks off this CPU */
278static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
279static DEFINE_MUTEX(shuffle_task_mutex);
280
281/*
282 * Register a task to be shuffled. If there is no memory, just splat
283 * and don't bother registering.
284 */
285void torture_shuffle_task_register(struct task_struct *tp)
286{
287 struct shuffle_task *stp;
288
289 if (WARN_ON_ONCE(tp == NULL))
290 return;
291 stp = kmalloc(sizeof(*stp), GFP_KERNEL);
292 if (WARN_ON_ONCE(stp == NULL))
293 return;
294 stp->st_t = tp;
295 mutex_lock(&shuffle_task_mutex);
296 list_add(&stp->st_l, &shuffle_task_list);
297 mutex_unlock(&shuffle_task_mutex);
298}
299EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
300
301/*
302 * Unregister all tasks, for example, at the end of the torture run.
303 */
304static void torture_shuffle_task_unregister_all(void)
305{
306 struct shuffle_task *stp;
307 struct shuffle_task *p;
308
309 mutex_lock(&shuffle_task_mutex);
310 list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
311 list_del(&stp->st_l);
312 kfree(stp);
313 }
314 mutex_unlock(&shuffle_task_mutex);
315}
316
317/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
318 * A special case is when shuffle_idle_cpu = -1, in which case we allow
319 * the tasks to run on all CPUs.
320 */
321static void torture_shuffle_tasks(void)
322{
323 struct shuffle_task *stp;
324
325 cpumask_setall(shuffle_tmp_mask);
326 get_online_cpus();
327
328 /* No point in shuffling if there is only one online CPU (ex: UP) */
329 if (num_online_cpus() == 1) {
330 put_online_cpus();
331 return;
332 }
333
334 /* Advance to the next CPU. Upon overflow, don't idle any CPUs. */
335 shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
336 if (shuffle_idle_cpu >= nr_cpu_ids)
337 shuffle_idle_cpu = -1;
338 if (shuffle_idle_cpu != -1) {
339 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
340 if (cpumask_empty(shuffle_tmp_mask)) {
341 put_online_cpus();
342 return;
343 }
344 }
345
346 mutex_lock(&shuffle_task_mutex);
347 list_for_each_entry(stp, &shuffle_task_list, st_l)
348 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
349 mutex_unlock(&shuffle_task_mutex);
350
351 put_online_cpus();
352}
353
354/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
355 * system to become idle at a time and cut off its timer ticks. This is meant
356 * to test the support for such tickless idle CPU in RCU.
357 */
358static int torture_shuffle(void *arg)
359{
360 VERBOSE_TOROUT_STRING("torture_shuffle task started");
361 do {
362 schedule_timeout_interruptible(shuffle_interval);
363 torture_shuffle_tasks();
364 torture_shutdown_absorb("torture_shuffle");
365 } while (!torture_must_stop());
366 torture_kthread_stopping("torture_shuffle");
367 return 0;
368}
369
370/*
371 * Start the shuffler, with shuffint in jiffies.
372 */
373int torture_shuffle_init(long shuffint)
374{
375 shuffle_interval = shuffint;
376
377 shuffle_idle_cpu = -1;
378
379 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
380 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
381 return -ENOMEM;
382 }
383
384 /* Create the shuffler thread */
385 return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
386}
387EXPORT_SYMBOL_GPL(torture_shuffle_init);
388
389/*
390 * Stop the shuffling.
391 */
392static void torture_shuffle_cleanup(void)
393{
394 torture_shuffle_task_unregister_all();
395 if (shuffler_task) {
396 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
397 kthread_stop(shuffler_task);
398 free_cpumask_var(shuffle_tmp_mask);
399 }
400 shuffler_task = NULL;
401}
402EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
403
404/*
405 * Variables for auto-shutdown. This allows "lights out" torture runs
406 * to be fully scripted.
407 */
408static int shutdown_secs; /* desired test duration in seconds. */
409static struct task_struct *shutdown_task;
410static unsigned long shutdown_time; /* jiffies to system shutdown. */
411static void (*torture_shutdown_hook)(void);
412
413/*
414 * Absorb kthreads into a kernel function that won't return, so that
415 * they won't ever access module text or data again.
416 */
417void torture_shutdown_absorb(const char *title)
418{
419 while (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
420 pr_notice("torture thread %s parking due to system shutdown\n",
421 title);
422 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
423 }
424}
425EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
426
427/*
428 * Cause the torture test to shutdown the system after the test has
429 * run for the time specified by the shutdown_secs parameter.
430 */
431static int torture_shutdown(void *arg)
432{
433 long delta;
434 unsigned long jiffies_snap;
435
436 VERBOSE_TOROUT_STRING("torture_shutdown task started");
437 jiffies_snap = jiffies;
438 while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
439 !torture_must_stop()) {
440 delta = shutdown_time - jiffies_snap;
441 if (verbose)
442 pr_alert("%s" TORTURE_FLAG
443 "torture_shutdown task: %lu jiffies remaining\n",
444 torture_type, delta);
445 schedule_timeout_interruptible(delta);
446 jiffies_snap = jiffies;
447 }
448 if (torture_must_stop()) {
449 torture_kthread_stopping("torture_shutdown");
450 return 0;
451 }
452
453 /* OK, shut down the system. */
454
455 VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
456 shutdown_task = NULL; /* Avoid self-kill deadlock. */
457 if (torture_shutdown_hook)
458 torture_shutdown_hook();
459 else
460 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
461 kernel_power_off(); /* Shut down the system. */
462 return 0;
463}
464
465/*
466 * Start up the shutdown task.
467 */
468int torture_shutdown_init(int ssecs, void (*cleanup)(void))
469{
470 int ret = 0;
471
472 shutdown_secs = ssecs;
473 torture_shutdown_hook = cleanup;
474 if (shutdown_secs > 0) {
475 shutdown_time = jiffies + shutdown_secs * HZ;
476 ret = torture_create_kthread(torture_shutdown, NULL,
477 shutdown_task);
478 }
479 return ret;
480}
481EXPORT_SYMBOL_GPL(torture_shutdown_init);
482
483/*
484 * Detect and respond to a system shutdown.
485 */
486static int torture_shutdown_notify(struct notifier_block *unused1,
487 unsigned long unused2, void *unused3)
488{
489 mutex_lock(&fullstop_mutex);
490 if (ACCESS_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
491 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
492 ACCESS_ONCE(fullstop) = FULLSTOP_SHUTDOWN;
493 } else {
494 pr_warn("Concurrent rmmod and shutdown illegal!\n");
495 }
496 mutex_unlock(&fullstop_mutex);
497 return NOTIFY_DONE;
498}
499
500static struct notifier_block torture_shutdown_nb = {
501 .notifier_call = torture_shutdown_notify,
502};
503
504/*
505 * Shut down the shutdown task. Say what??? Heh! This can happen if
506 * the torture module gets an rmmod before the shutdown time arrives. ;-)
507 */
508static void torture_shutdown_cleanup(void)
509{
510 unregister_reboot_notifier(&torture_shutdown_nb);
511 if (shutdown_task != NULL) {
512 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
513 kthread_stop(shutdown_task);
514 }
515 shutdown_task = NULL;
516}
517
518/*
519 * Variables for stuttering, which means to periodically pause and
520 * restart testing in order to catch bugs that appear when load is
521 * suddenly applied to or removed from the system.
522 */
523static struct task_struct *stutter_task;
524static int stutter_pause_test;
525static int stutter;
526
527/*
528 * Block until the stutter interval ends. This must be called periodically
529 * by all running kthreads that need to be subject to stuttering.
530 */
531void stutter_wait(const char *title)
532{
533 while (ACCESS_ONCE(stutter_pause_test) ||
534 (torture_runnable && !ACCESS_ONCE(*torture_runnable))) {
535 if (stutter_pause_test)
536 schedule_timeout_interruptible(1);
537 else
538 schedule_timeout_interruptible(round_jiffies_relative(HZ));
539 torture_shutdown_absorb(title);
540 }
541}
542EXPORT_SYMBOL_GPL(stutter_wait);
543
544/*
545 * Cause the torture test to "stutter", starting and stopping all
546 * threads periodically.
547 */
548static int torture_stutter(void *arg)
549{
550 VERBOSE_TOROUT_STRING("torture_stutter task started");
551 do {
552 if (!torture_must_stop()) {
553 schedule_timeout_interruptible(stutter);
554 ACCESS_ONCE(stutter_pause_test) = 1;
555 }
556 if (!torture_must_stop())
557 schedule_timeout_interruptible(stutter);
558 ACCESS_ONCE(stutter_pause_test) = 0;
559 torture_shutdown_absorb("torture_stutter");
560 } while (!torture_must_stop());
561 torture_kthread_stopping("torture_stutter");
562 return 0;
563}
564
565/*
566 * Initialize and kick off the torture_stutter kthread.
567 */
568int torture_stutter_init(int s)
569{
570 int ret;
571
572 stutter = s;
573 ret = torture_create_kthread(torture_stutter, NULL, stutter_task);
574 return ret;
575}
576EXPORT_SYMBOL_GPL(torture_stutter_init);
577
578/*
579 * Cleanup after the torture_stutter kthread.
580 */
581static void torture_stutter_cleanup(void)
582{
583 if (!stutter_task)
584 return;
585 VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
586 kthread_stop(stutter_task);
587 stutter_task = NULL;
588}
589
590/*
591 * Initialize torture module. Please note that this is -not- invoked via
592 * the usual module_init() mechanism, but rather by an explicit call from
593 * the client torture module. This call must be paired with a later
594 * torture_init_end().
595 *
596 * The runnable parameter points to a flag that controls whether or not
597 * the test is currently runnable. If there is no such flag, pass in NULL.
598 */
599void __init torture_init_begin(char *ttype, bool v, int *runnable)
600{
601 mutex_lock(&fullstop_mutex);
602 torture_type = ttype;
603 verbose = v;
604 torture_runnable = runnable;
605 fullstop = FULLSTOP_DONTSTOP;
606
607}
608EXPORT_SYMBOL_GPL(torture_init_begin);
609
610/*
611 * Tell the torture module that initialization is complete.
612 */
613void __init torture_init_end(void)
614{
615 mutex_unlock(&fullstop_mutex);
616 register_reboot_notifier(&torture_shutdown_nb);
617}
618EXPORT_SYMBOL_GPL(torture_init_end);
619
620/*
621 * Clean up torture module. Please note that this is -not- invoked via
622 * the usual module_exit() mechanism, but rather by an explicit call from
623 * the client torture module. Returns true if a race with system shutdown
624 * is detected, otherwise, all kthreads started by functions in this file
625 * will be shut down.
626 *
627 * This must be called before the caller starts shutting down its own
628 * kthreads.
629 */
630bool torture_cleanup(void)
631{
632 mutex_lock(&fullstop_mutex);
633 if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
634 pr_warn("Concurrent rmmod and shutdown illegal!\n");
635 mutex_unlock(&fullstop_mutex);
636 schedule_timeout_uninterruptible(10);
637 return true;
638 }
639 ACCESS_ONCE(fullstop) = FULLSTOP_RMMOD;
640 mutex_unlock(&fullstop_mutex);
641 torture_shutdown_cleanup();
642 torture_shuffle_cleanup();
643 torture_stutter_cleanup();
644 torture_onoff_cleanup();
645 return false;
646}
647EXPORT_SYMBOL_GPL(torture_cleanup);
648
649/*
650 * Is it time for the current torture test to stop?
651 */
652bool torture_must_stop(void)
653{
654 return torture_must_stop_irq() || kthread_should_stop();
655}
656EXPORT_SYMBOL_GPL(torture_must_stop);
657
658/*
659 * Is it time for the current torture test to stop? This is the irq-safe
660 * version, hence no check for kthread_should_stop().
661 */
662bool torture_must_stop_irq(void)
663{
664 return ACCESS_ONCE(fullstop) != FULLSTOP_DONTSTOP;
665}
666EXPORT_SYMBOL_GPL(torture_must_stop_irq);
667
668/*
669 * Each kthread must wait for kthread_should_stop() before returning from
670 * its top-level function, otherwise segfaults ensue. This function
671 * prints a "stopping" message and waits for kthread_should_stop(), and
672 * should be called from all torture kthreads immediately prior to
673 * returning.
674 */
675void torture_kthread_stopping(char *title)
676{
677 if (verbose)
678 VERBOSE_TOROUT_STRING(title);
679 while (!kthread_should_stop()) {
680 torture_shutdown_absorb(title);
681 schedule_timeout_uninterruptible(1);
682 }
683}
684EXPORT_SYMBOL_GPL(torture_kthread_stopping);
685
686/*
687 * Create a generic torture kthread that is immediately runnable. If you
688 * need the kthread to be stopped so that you can do something to it before
689 * it starts, you will need to open-code your own.
690 */
691int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
692 char *f, struct task_struct **tp)
693{
694 int ret = 0;
695
696 VERBOSE_TOROUT_STRING(m);
697 *tp = kthread_run(fn, arg, s);
698 if (IS_ERR(*tp)) {
699 ret = PTR_ERR(*tp);
700 VERBOSE_TOROUT_ERRSTRING(f);
701 *tp = NULL;
702 }
703 torture_shuffle_task_register(*tp);
704 return ret;
705}
706EXPORT_SYMBOL_GPL(_torture_create_kthread);
707
708/*
709 * Stop a generic kthread, emitting a message.
710 */
711void _torture_stop_kthread(char *m, struct task_struct **tp)
712{
713 if (*tp == NULL)
714 return;
715 VERBOSE_TOROUT_STRING(m);
716 kthread_stop(*tp);
717 *tp = NULL;
718}
719EXPORT_SYMBOL_GPL(_torture_stop_kthread);