328a8257c8855133c617b123a7a9d4f417607592
[linux-3.10.git] / kernel / rcutorture.c
1 /*
2  * Read-Copy Update module-based torture test facility
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, write to the Free Software
16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17  *
18  * Copyright (C) IBM Corporation, 2005, 2006
19  *
20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
21  *          Josh Triplett <josh@freedesktop.org>
22  *
23  * See also:  Documentation/RCU/torture.txt
24  */
25 #include <linux/types.h>
26 #include <linux/kernel.h>
27 #include <linux/init.h>
28 #include <linux/module.h>
29 #include <linux/kthread.h>
30 #include <linux/err.h>
31 #include <linux/spinlock.h>
32 #include <linux/smp.h>
33 #include <linux/rcupdate.h>
34 #include <linux/interrupt.h>
35 #include <linux/sched.h>
36 #include <asm/atomic.h>
37 #include <linux/bitops.h>
38 #include <linux/completion.h>
39 #include <linux/moduleparam.h>
40 #include <linux/percpu.h>
41 #include <linux/notifier.h>
42 #include <linux/reboot.h>
43 #include <linux/freezer.h>
44 #include <linux/cpu.h>
45 #include <linux/delay.h>
46 #include <linux/stat.h>
47 #include <linux/srcu.h>
48 #include <linux/slab.h>
49 #include <asm/byteorder.h>
50
51 MODULE_LICENSE("GPL");
52 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
53               "Josh Triplett <josh@freedesktop.org>");
54
55 static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
56 static int nfakewriters = 4;    /* # fake writer threads */
57 static int stat_interval;       /* Interval between stats, in seconds. */
58                                 /*  Defaults to "only at end of test". */
59 static int verbose;             /* Print more debug info. */
60 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
61 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
62 static int stutter = 5;         /* Start/stop testing interval (in sec) */
63 static int irqreader = 1;       /* RCU readers from irq (timers). */
64 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
65
66 module_param(nreaders, int, 0444);
67 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
68 module_param(nfakewriters, int, 0444);
69 MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
70 module_param(stat_interval, int, 0444);
71 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
72 module_param(verbose, bool, 0444);
73 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
74 module_param(test_no_idle_hz, bool, 0444);
75 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
76 module_param(shuffle_interval, int, 0444);
77 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
78 module_param(stutter, int, 0444);
79 MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
80 module_param(irqreader, int, 0444);
81 MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
82 module_param(torture_type, charp, 0444);
83 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
84
85 #define TORTURE_FLAG "-torture:"
86 #define PRINTK_STRING(s) \
87         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
88 #define VERBOSE_PRINTK_STRING(s) \
89         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
90 #define VERBOSE_PRINTK_ERRSTRING(s) \
91         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
92
93 static char printk_buf[4096];
94
95 static int nrealreaders;
96 static struct task_struct *writer_task;
97 static struct task_struct **fakewriter_tasks;
98 static struct task_struct **reader_tasks;
99 static struct task_struct *stats_task;
100 static struct task_struct *shuffler_task;
101 static struct task_struct *stutter_task;
102
103 #define RCU_TORTURE_PIPE_LEN 10
104
105 struct rcu_torture {
106         struct rcu_head rtort_rcu;
107         int rtort_pipe_count;
108         struct list_head rtort_free;
109         int rtort_mbtest;
110 };
111
112 static LIST_HEAD(rcu_torture_freelist);
113 static struct rcu_torture *rcu_torture_current = NULL;
114 static long rcu_torture_current_version = 0;
115 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
116 static DEFINE_SPINLOCK(rcu_torture_lock);
117 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
118         { 0 };
119 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
120         { 0 };
121 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
122 static atomic_t n_rcu_torture_alloc;
123 static atomic_t n_rcu_torture_alloc_fail;
124 static atomic_t n_rcu_torture_free;
125 static atomic_t n_rcu_torture_mberror;
126 static atomic_t n_rcu_torture_error;
127 static long n_rcu_torture_timers = 0;
128 static struct list_head rcu_torture_removed;
129 static cpumask_var_t shuffle_tmp_mask;
130
131 static int stutter_pause_test = 0;
132
133 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
134 #define RCUTORTURE_RUNNABLE_INIT 1
135 #else
136 #define RCUTORTURE_RUNNABLE_INIT 0
137 #endif
138 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
139
140 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
141
142 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
143 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with rcutorture running. */
144 #define FULLSTOP_RMMOD    2     /* Normal rmmod of rcutorture. */
145 static int fullstop = FULLSTOP_RMMOD;
146 DEFINE_MUTEX(fullstop_mutex);   /* Protect fullstop transitions and spawning */
147                                 /*  of kthreads. */
148
149 /*
150  * Detect and respond to a system shutdown.
151  */
152 static int
153 rcutorture_shutdown_notify(struct notifier_block *unused1,
154                            unsigned long unused2, void *unused3)
155 {
156         mutex_lock(&fullstop_mutex);
157         if (fullstop == FULLSTOP_DONTSTOP)
158                 fullstop = FULLSTOP_SHUTDOWN;
159         else
160                 printk(KERN_WARNING /* but going down anyway, so... */
161                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
162         mutex_unlock(&fullstop_mutex);
163         return NOTIFY_DONE;
164 }
165
166 /*
167  * Absorb kthreads into a kernel function that won't return, so that
168  * they won't ever access module text or data again.
169  */
170 static void rcutorture_shutdown_absorb(char *title)
171 {
172         if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
173                 printk(KERN_NOTICE
174                        "rcutorture thread %s parking due to system shutdown\n",
175                        title);
176                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
177         }
178 }
179
180 /*
181  * Allocate an element from the rcu_tortures pool.
182  */
183 static struct rcu_torture *
184 rcu_torture_alloc(void)
185 {
186         struct list_head *p;
187
188         spin_lock_bh(&rcu_torture_lock);
189         if (list_empty(&rcu_torture_freelist)) {
190                 atomic_inc(&n_rcu_torture_alloc_fail);
191                 spin_unlock_bh(&rcu_torture_lock);
192                 return NULL;
193         }
194         atomic_inc(&n_rcu_torture_alloc);
195         p = rcu_torture_freelist.next;
196         list_del_init(p);
197         spin_unlock_bh(&rcu_torture_lock);
198         return container_of(p, struct rcu_torture, rtort_free);
199 }
200
201 /*
202  * Free an element to the rcu_tortures pool.
203  */
204 static void
205 rcu_torture_free(struct rcu_torture *p)
206 {
207         atomic_inc(&n_rcu_torture_free);
208         spin_lock_bh(&rcu_torture_lock);
209         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
210         spin_unlock_bh(&rcu_torture_lock);
211 }
212
213 struct rcu_random_state {
214         unsigned long rrs_state;
215         long rrs_count;
216 };
217
218 #define RCU_RANDOM_MULT 39916801  /* prime */
219 #define RCU_RANDOM_ADD  479001701 /* prime */
220 #define RCU_RANDOM_REFRESH 10000
221
222 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
223
224 /*
225  * Crude but fast random-number generator.  Uses a linear congruential
226  * generator, with occasional help from cpu_clock().
227  */
228 static unsigned long
229 rcu_random(struct rcu_random_state *rrsp)
230 {
231         if (--rrsp->rrs_count < 0) {
232                 rrsp->rrs_state +=
233                         (unsigned long)cpu_clock(raw_smp_processor_id());
234                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
235         }
236         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
237         return swahw32(rrsp->rrs_state);
238 }
239
240 static void
241 rcu_stutter_wait(char *title)
242 {
243         while (stutter_pause_test || !rcutorture_runnable) {
244                 if (rcutorture_runnable)
245                         schedule_timeout_interruptible(1);
246                 else
247                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
248                 rcutorture_shutdown_absorb(title);
249         }
250 }
251
252 /*
253  * Operations vector for selecting different types of tests.
254  */
255
256 struct rcu_torture_ops {
257         void (*init)(void);
258         void (*cleanup)(void);
259         int (*readlock)(void);
260         void (*read_delay)(struct rcu_random_state *rrsp);
261         void (*readunlock)(int idx);
262         int (*completed)(void);
263         void (*deferred_free)(struct rcu_torture *p);
264         void (*sync)(void);
265         void (*cb_barrier)(void);
266         int (*stats)(char *page);
267         int irq_capable;
268         char *name;
269 };
270 static struct rcu_torture_ops *cur_ops = NULL;
271
272 /*
273  * Definitions for rcu torture testing.
274  */
275
276 static int rcu_torture_read_lock(void) __acquires(RCU)
277 {
278         rcu_read_lock();
279         return 0;
280 }
281
282 static void rcu_read_delay(struct rcu_random_state *rrsp)
283 {
284         const unsigned long shortdelay_us = 200;
285         const unsigned long longdelay_ms = 50;
286
287         /* We want a short delay sometimes to make a reader delay the grace
288          * period, and we want a long delay occasionally to trigger
289          * force_quiescent_state. */
290
291         if (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
292                 mdelay(longdelay_ms);
293         if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
294                 udelay(shortdelay_us);
295 }
296
297 static void rcu_torture_read_unlock(int idx) __releases(RCU)
298 {
299         rcu_read_unlock();
300 }
301
302 static int rcu_torture_completed(void)
303 {
304         return rcu_batches_completed();
305 }
306
307 static void
308 rcu_torture_cb(struct rcu_head *p)
309 {
310         int i;
311         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
312
313         if (fullstop != FULLSTOP_DONTSTOP) {
314                 /* Test is ending, just drop callbacks on the floor. */
315                 /* The next initialization will pick up the pieces. */
316                 return;
317         }
318         i = rp->rtort_pipe_count;
319         if (i > RCU_TORTURE_PIPE_LEN)
320                 i = RCU_TORTURE_PIPE_LEN;
321         atomic_inc(&rcu_torture_wcount[i]);
322         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
323                 rp->rtort_mbtest = 0;
324                 rcu_torture_free(rp);
325         } else
326                 cur_ops->deferred_free(rp);
327 }
328
329 static void rcu_torture_deferred_free(struct rcu_torture *p)
330 {
331         call_rcu(&p->rtort_rcu, rcu_torture_cb);
332 }
333
334 static struct rcu_torture_ops rcu_ops = {
335         .init           = NULL,
336         .cleanup        = NULL,
337         .readlock       = rcu_torture_read_lock,
338         .read_delay     = rcu_read_delay,
339         .readunlock     = rcu_torture_read_unlock,
340         .completed      = rcu_torture_completed,
341         .deferred_free  = rcu_torture_deferred_free,
342         .sync           = synchronize_rcu,
343         .cb_barrier     = rcu_barrier,
344         .stats          = NULL,
345         .irq_capable    = 1,
346         .name           = "rcu"
347 };
348
349 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
350 {
351         int i;
352         struct rcu_torture *rp;
353         struct rcu_torture *rp1;
354
355         cur_ops->sync();
356         list_add(&p->rtort_free, &rcu_torture_removed);
357         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
358                 i = rp->rtort_pipe_count;
359                 if (i > RCU_TORTURE_PIPE_LEN)
360                         i = RCU_TORTURE_PIPE_LEN;
361                 atomic_inc(&rcu_torture_wcount[i]);
362                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
363                         rp->rtort_mbtest = 0;
364                         list_del(&rp->rtort_free);
365                         rcu_torture_free(rp);
366                 }
367         }
368 }
369
370 static void rcu_sync_torture_init(void)
371 {
372         INIT_LIST_HEAD(&rcu_torture_removed);
373 }
374
375 static struct rcu_torture_ops rcu_sync_ops = {
376         .init           = rcu_sync_torture_init,
377         .cleanup        = NULL,
378         .readlock       = rcu_torture_read_lock,
379         .read_delay     = rcu_read_delay,
380         .readunlock     = rcu_torture_read_unlock,
381         .completed      = rcu_torture_completed,
382         .deferred_free  = rcu_sync_torture_deferred_free,
383         .sync           = synchronize_rcu,
384         .cb_barrier     = NULL,
385         .stats          = NULL,
386         .irq_capable    = 1,
387         .name           = "rcu_sync"
388 };
389
390 /*
391  * Definitions for rcu_bh torture testing.
392  */
393
394 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
395 {
396         rcu_read_lock_bh();
397         return 0;
398 }
399
400 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
401 {
402         rcu_read_unlock_bh();
403 }
404
405 static int rcu_bh_torture_completed(void)
406 {
407         return rcu_batches_completed_bh();
408 }
409
410 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
411 {
412         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
413 }
414
415 struct rcu_bh_torture_synchronize {
416         struct rcu_head head;
417         struct completion completion;
418 };
419
420 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
421 {
422         struct rcu_bh_torture_synchronize *rcu;
423
424         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
425         complete(&rcu->completion);
426 }
427
428 static void rcu_bh_torture_synchronize(void)
429 {
430         struct rcu_bh_torture_synchronize rcu;
431
432         init_completion(&rcu.completion);
433         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
434         wait_for_completion(&rcu.completion);
435 }
436
437 static struct rcu_torture_ops rcu_bh_ops = {
438         .init           = NULL,
439         .cleanup        = NULL,
440         .readlock       = rcu_bh_torture_read_lock,
441         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
442         .readunlock     = rcu_bh_torture_read_unlock,
443         .completed      = rcu_bh_torture_completed,
444         .deferred_free  = rcu_bh_torture_deferred_free,
445         .sync           = rcu_bh_torture_synchronize,
446         .cb_barrier     = rcu_barrier_bh,
447         .stats          = NULL,
448         .irq_capable    = 1,
449         .name           = "rcu_bh"
450 };
451
452 static struct rcu_torture_ops rcu_bh_sync_ops = {
453         .init           = rcu_sync_torture_init,
454         .cleanup        = NULL,
455         .readlock       = rcu_bh_torture_read_lock,
456         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
457         .readunlock     = rcu_bh_torture_read_unlock,
458         .completed      = rcu_bh_torture_completed,
459         .deferred_free  = rcu_sync_torture_deferred_free,
460         .sync           = rcu_bh_torture_synchronize,
461         .cb_barrier     = NULL,
462         .stats          = NULL,
463         .irq_capable    = 1,
464         .name           = "rcu_bh_sync"
465 };
466
467 /*
468  * Definitions for srcu torture testing.
469  */
470
471 static struct srcu_struct srcu_ctl;
472
473 static void srcu_torture_init(void)
474 {
475         init_srcu_struct(&srcu_ctl);
476         rcu_sync_torture_init();
477 }
478
479 static void srcu_torture_cleanup(void)
480 {
481         synchronize_srcu(&srcu_ctl);
482         cleanup_srcu_struct(&srcu_ctl);
483 }
484
485 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
486 {
487         return srcu_read_lock(&srcu_ctl);
488 }
489
490 static void srcu_read_delay(struct rcu_random_state *rrsp)
491 {
492         long delay;
493         const long uspertick = 1000000 / HZ;
494         const long longdelay = 10;
495
496         /* We want there to be long-running readers, but not all the time. */
497
498         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
499         if (!delay)
500                 schedule_timeout_interruptible(longdelay);
501 }
502
503 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
504 {
505         srcu_read_unlock(&srcu_ctl, idx);
506 }
507
508 static int srcu_torture_completed(void)
509 {
510         return srcu_batches_completed(&srcu_ctl);
511 }
512
513 static void srcu_torture_synchronize(void)
514 {
515         synchronize_srcu(&srcu_ctl);
516 }
517
518 static int srcu_torture_stats(char *page)
519 {
520         int cnt = 0;
521         int cpu;
522         int idx = srcu_ctl.completed & 0x1;
523
524         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
525                        torture_type, TORTURE_FLAG, idx);
526         for_each_possible_cpu(cpu) {
527                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
528                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
529                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
530         }
531         cnt += sprintf(&page[cnt], "\n");
532         return cnt;
533 }
534
535 static struct rcu_torture_ops srcu_ops = {
536         .init           = srcu_torture_init,
537         .cleanup        = srcu_torture_cleanup,
538         .readlock       = srcu_torture_read_lock,
539         .read_delay     = srcu_read_delay,
540         .readunlock     = srcu_torture_read_unlock,
541         .completed      = srcu_torture_completed,
542         .deferred_free  = rcu_sync_torture_deferred_free,
543         .sync           = srcu_torture_synchronize,
544         .cb_barrier     = NULL,
545         .stats          = srcu_torture_stats,
546         .name           = "srcu"
547 };
548
549 /*
550  * Definitions for sched torture testing.
551  */
552
553 static int sched_torture_read_lock(void)
554 {
555         preempt_disable();
556         return 0;
557 }
558
559 static void sched_torture_read_unlock(int idx)
560 {
561         preempt_enable();
562 }
563
564 static int sched_torture_completed(void)
565 {
566         return 0;
567 }
568
569 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
570 {
571         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
572 }
573
574 static void sched_torture_synchronize(void)
575 {
576         synchronize_sched();
577 }
578
579 static struct rcu_torture_ops sched_ops = {
580         .init           = rcu_sync_torture_init,
581         .cleanup        = NULL,
582         .readlock       = sched_torture_read_lock,
583         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
584         .readunlock     = sched_torture_read_unlock,
585         .completed      = sched_torture_completed,
586         .deferred_free  = rcu_sched_torture_deferred_free,
587         .sync           = sched_torture_synchronize,
588         .cb_barrier     = rcu_barrier_sched,
589         .stats          = NULL,
590         .irq_capable    = 1,
591         .name           = "sched"
592 };
593
594 static struct rcu_torture_ops sched_ops_sync = {
595         .init           = rcu_sync_torture_init,
596         .cleanup        = NULL,
597         .readlock       = sched_torture_read_lock,
598         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
599         .readunlock     = sched_torture_read_unlock,
600         .completed      = sched_torture_completed,
601         .deferred_free  = rcu_sync_torture_deferred_free,
602         .sync           = sched_torture_synchronize,
603         .cb_barrier     = NULL,
604         .stats          = NULL,
605         .name           = "sched_sync"
606 };
607
608 extern int rcu_expedited_torture_stats(char *page);
609
610 static struct rcu_torture_ops sched_expedited_ops = {
611         .init           = rcu_sync_torture_init,
612         .cleanup        = NULL,
613         .readlock       = sched_torture_read_lock,
614         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
615         .readunlock     = sched_torture_read_unlock,
616         .completed      = sched_torture_completed,
617         .deferred_free  = rcu_sync_torture_deferred_free,
618         .sync           = synchronize_sched_expedited,
619         .cb_barrier     = NULL,
620         .stats          = rcu_expedited_torture_stats,
621         .irq_capable    = 1,
622         .name           = "sched_expedited"
623 };
624
625 /*
626  * RCU torture writer kthread.  Repeatedly substitutes a new structure
627  * for that pointed to by rcu_torture_current, freeing the old structure
628  * after a series of grace periods (the "pipeline").
629  */
630 static int
631 rcu_torture_writer(void *arg)
632 {
633         int i;
634         long oldbatch = rcu_batches_completed();
635         struct rcu_torture *rp;
636         struct rcu_torture *old_rp;
637         static DEFINE_RCU_RANDOM(rand);
638
639         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
640         set_user_nice(current, 19);
641
642         do {
643                 schedule_timeout_uninterruptible(1);
644                 if ((rp = rcu_torture_alloc()) == NULL)
645                         continue;
646                 rp->rtort_pipe_count = 0;
647                 udelay(rcu_random(&rand) & 0x3ff);
648                 old_rp = rcu_torture_current;
649                 rp->rtort_mbtest = 1;
650                 rcu_assign_pointer(rcu_torture_current, rp);
651                 smp_wmb();
652                 if (old_rp) {
653                         i = old_rp->rtort_pipe_count;
654                         if (i > RCU_TORTURE_PIPE_LEN)
655                                 i = RCU_TORTURE_PIPE_LEN;
656                         atomic_inc(&rcu_torture_wcount[i]);
657                         old_rp->rtort_pipe_count++;
658                         cur_ops->deferred_free(old_rp);
659                 }
660                 rcu_torture_current_version++;
661                 oldbatch = cur_ops->completed();
662                 rcu_stutter_wait("rcu_torture_writer");
663         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
664         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
665         rcutorture_shutdown_absorb("rcu_torture_writer");
666         while (!kthread_should_stop())
667                 schedule_timeout_uninterruptible(1);
668         return 0;
669 }
670
671 /*
672  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
673  * delay between calls.
674  */
675 static int
676 rcu_torture_fakewriter(void *arg)
677 {
678         DEFINE_RCU_RANDOM(rand);
679
680         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
681         set_user_nice(current, 19);
682
683         do {
684                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
685                 udelay(rcu_random(&rand) & 0x3ff);
686                 cur_ops->sync();
687                 rcu_stutter_wait("rcu_torture_fakewriter");
688         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
689
690         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
691         rcutorture_shutdown_absorb("rcu_torture_fakewriter");
692         while (!kthread_should_stop())
693                 schedule_timeout_uninterruptible(1);
694         return 0;
695 }
696
697 /*
698  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
699  * incrementing the corresponding element of the pipeline array.  The
700  * counter in the element should never be greater than 1, otherwise, the
701  * RCU implementation is broken.
702  */
703 static void rcu_torture_timer(unsigned long unused)
704 {
705         int idx;
706         int completed;
707         static DEFINE_RCU_RANDOM(rand);
708         static DEFINE_SPINLOCK(rand_lock);
709         struct rcu_torture *p;
710         int pipe_count;
711
712         idx = cur_ops->readlock();
713         completed = cur_ops->completed();
714         p = rcu_dereference(rcu_torture_current);
715         if (p == NULL) {
716                 /* Leave because rcu_torture_writer is not yet underway */
717                 cur_ops->readunlock(idx);
718                 return;
719         }
720         if (p->rtort_mbtest == 0)
721                 atomic_inc(&n_rcu_torture_mberror);
722         spin_lock(&rand_lock);
723         cur_ops->read_delay(&rand);
724         n_rcu_torture_timers++;
725         spin_unlock(&rand_lock);
726         preempt_disable();
727         pipe_count = p->rtort_pipe_count;
728         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
729                 /* Should not happen, but... */
730                 pipe_count = RCU_TORTURE_PIPE_LEN;
731         }
732         ++__get_cpu_var(rcu_torture_count)[pipe_count];
733         completed = cur_ops->completed() - completed;
734         if (completed > RCU_TORTURE_PIPE_LEN) {
735                 /* Should not happen, but... */
736                 completed = RCU_TORTURE_PIPE_LEN;
737         }
738         ++__get_cpu_var(rcu_torture_batch)[completed];
739         preempt_enable();
740         cur_ops->readunlock(idx);
741 }
742
743 /*
744  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
745  * incrementing the corresponding element of the pipeline array.  The
746  * counter in the element should never be greater than 1, otherwise, the
747  * RCU implementation is broken.
748  */
749 static int
750 rcu_torture_reader(void *arg)
751 {
752         int completed;
753         int idx;
754         DEFINE_RCU_RANDOM(rand);
755         struct rcu_torture *p;
756         int pipe_count;
757         struct timer_list t;
758
759         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
760         set_user_nice(current, 19);
761         if (irqreader && cur_ops->irq_capable)
762                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
763
764         do {
765                 if (irqreader && cur_ops->irq_capable) {
766                         if (!timer_pending(&t))
767                                 mod_timer(&t, 1);
768                 }
769                 idx = cur_ops->readlock();
770                 completed = cur_ops->completed();
771                 p = rcu_dereference(rcu_torture_current);
772                 if (p == NULL) {
773                         /* Wait for rcu_torture_writer to get underway */
774                         cur_ops->readunlock(idx);
775                         schedule_timeout_interruptible(HZ);
776                         continue;
777                 }
778                 if (p->rtort_mbtest == 0)
779                         atomic_inc(&n_rcu_torture_mberror);
780                 cur_ops->read_delay(&rand);
781                 preempt_disable();
782                 pipe_count = p->rtort_pipe_count;
783                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
784                         /* Should not happen, but... */
785                         pipe_count = RCU_TORTURE_PIPE_LEN;
786                 }
787                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
788                 completed = cur_ops->completed() - completed;
789                 if (completed > RCU_TORTURE_PIPE_LEN) {
790                         /* Should not happen, but... */
791                         completed = RCU_TORTURE_PIPE_LEN;
792                 }
793                 ++__get_cpu_var(rcu_torture_batch)[completed];
794                 preempt_enable();
795                 cur_ops->readunlock(idx);
796                 schedule();
797                 rcu_stutter_wait("rcu_torture_reader");
798         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
799         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
800         rcutorture_shutdown_absorb("rcu_torture_reader");
801         if (irqreader && cur_ops->irq_capable)
802                 del_timer_sync(&t);
803         while (!kthread_should_stop())
804                 schedule_timeout_uninterruptible(1);
805         return 0;
806 }
807
808 /*
809  * Create an RCU-torture statistics message in the specified buffer.
810  */
811 static int
812 rcu_torture_printk(char *page)
813 {
814         int cnt = 0;
815         int cpu;
816         int i;
817         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
818         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
819
820         for_each_possible_cpu(cpu) {
821                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
822                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
823                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
824                 }
825         }
826         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
827                 if (pipesummary[i] != 0)
828                         break;
829         }
830         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
831         cnt += sprintf(&page[cnt],
832                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
833                        "rtmbe: %d nt: %ld",
834                        rcu_torture_current,
835                        rcu_torture_current_version,
836                        list_empty(&rcu_torture_freelist),
837                        atomic_read(&n_rcu_torture_alloc),
838                        atomic_read(&n_rcu_torture_alloc_fail),
839                        atomic_read(&n_rcu_torture_free),
840                        atomic_read(&n_rcu_torture_mberror),
841                        n_rcu_torture_timers);
842         if (atomic_read(&n_rcu_torture_mberror) != 0)
843                 cnt += sprintf(&page[cnt], " !!!");
844         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
845         if (i > 1) {
846                 cnt += sprintf(&page[cnt], "!!! ");
847                 atomic_inc(&n_rcu_torture_error);
848                 WARN_ON_ONCE(1);
849         }
850         cnt += sprintf(&page[cnt], "Reader Pipe: ");
851         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
852                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
853         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
854         cnt += sprintf(&page[cnt], "Reader Batch: ");
855         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
856                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
857         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
858         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
859         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
860                 cnt += sprintf(&page[cnt], " %d",
861                                atomic_read(&rcu_torture_wcount[i]));
862         }
863         cnt += sprintf(&page[cnt], "\n");
864         if (cur_ops->stats)
865                 cnt += cur_ops->stats(&page[cnt]);
866         return cnt;
867 }
868
869 /*
870  * Print torture statistics.  Caller must ensure that there is only
871  * one call to this function at a given time!!!  This is normally
872  * accomplished by relying on the module system to only have one copy
873  * of the module loaded, and then by giving the rcu_torture_stats
874  * kthread full control (or the init/cleanup functions when rcu_torture_stats
875  * thread is not running).
876  */
877 static void
878 rcu_torture_stats_print(void)
879 {
880         int cnt;
881
882         cnt = rcu_torture_printk(printk_buf);
883         printk(KERN_ALERT "%s", printk_buf);
884 }
885
886 /*
887  * Periodically prints torture statistics, if periodic statistics printing
888  * was specified via the stat_interval module parameter.
889  *
890  * No need to worry about fullstop here, since this one doesn't reference
891  * volatile state or register callbacks.
892  */
893 static int
894 rcu_torture_stats(void *arg)
895 {
896         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
897         do {
898                 schedule_timeout_interruptible(stat_interval * HZ);
899                 rcu_torture_stats_print();
900                 rcutorture_shutdown_absorb("rcu_torture_stats");
901         } while (!kthread_should_stop());
902         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
903         return 0;
904 }
905
906 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
907
908 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
909  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
910  */
911 static void rcu_torture_shuffle_tasks(void)
912 {
913         int i;
914
915         cpumask_setall(shuffle_tmp_mask);
916         get_online_cpus();
917
918         /* No point in shuffling if there is only one online CPU (ex: UP) */
919         if (num_online_cpus() == 1) {
920                 put_online_cpus();
921                 return;
922         }
923
924         if (rcu_idle_cpu != -1)
925                 cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
926
927         set_cpus_allowed_ptr(current, shuffle_tmp_mask);
928
929         if (reader_tasks) {
930                 for (i = 0; i < nrealreaders; i++)
931                         if (reader_tasks[i])
932                                 set_cpus_allowed_ptr(reader_tasks[i],
933                                                      shuffle_tmp_mask);
934         }
935
936         if (fakewriter_tasks) {
937                 for (i = 0; i < nfakewriters; i++)
938                         if (fakewriter_tasks[i])
939                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
940                                                      shuffle_tmp_mask);
941         }
942
943         if (writer_task)
944                 set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
945
946         if (stats_task)
947                 set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
948
949         if (rcu_idle_cpu == -1)
950                 rcu_idle_cpu = num_online_cpus() - 1;
951         else
952                 rcu_idle_cpu--;
953
954         put_online_cpus();
955 }
956
957 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
958  * system to become idle at a time and cut off its timer ticks. This is meant
959  * to test the support for such tickless idle CPU in RCU.
960  */
961 static int
962 rcu_torture_shuffle(void *arg)
963 {
964         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
965         do {
966                 schedule_timeout_interruptible(shuffle_interval * HZ);
967                 rcu_torture_shuffle_tasks();
968                 rcutorture_shutdown_absorb("rcu_torture_shuffle");
969         } while (!kthread_should_stop());
970         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
971         return 0;
972 }
973
974 /* Cause the rcutorture test to "stutter", starting and stopping all
975  * threads periodically.
976  */
977 static int
978 rcu_torture_stutter(void *arg)
979 {
980         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
981         do {
982                 schedule_timeout_interruptible(stutter * HZ);
983                 stutter_pause_test = 1;
984                 if (!kthread_should_stop())
985                         schedule_timeout_interruptible(stutter * HZ);
986                 stutter_pause_test = 0;
987                 rcutorture_shutdown_absorb("rcu_torture_stutter");
988         } while (!kthread_should_stop());
989         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
990         return 0;
991 }
992
993 static inline void
994 rcu_torture_print_module_parms(char *tag)
995 {
996         printk(KERN_ALERT "%s" TORTURE_FLAG
997                 "--- %s: nreaders=%d nfakewriters=%d "
998                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
999                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
1000                 torture_type, tag, nrealreaders, nfakewriters,
1001                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1002                 stutter, irqreader);
1003 }
1004
1005 static struct notifier_block rcutorture_nb = {
1006         .notifier_call = rcutorture_shutdown_notify,
1007 };
1008
1009 static void
1010 rcu_torture_cleanup(void)
1011 {
1012         int i;
1013
1014         mutex_lock(&fullstop_mutex);
1015         if (fullstop == FULLSTOP_SHUTDOWN) {
1016                 printk(KERN_WARNING /* but going down anyway, so... */
1017                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
1018                 mutex_unlock(&fullstop_mutex);
1019                 schedule_timeout_uninterruptible(10);
1020                 if (cur_ops->cb_barrier != NULL)
1021                         cur_ops->cb_barrier();
1022                 return;
1023         }
1024         fullstop = FULLSTOP_RMMOD;
1025         mutex_unlock(&fullstop_mutex);
1026         unregister_reboot_notifier(&rcutorture_nb);
1027         if (stutter_task) {
1028                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
1029                 kthread_stop(stutter_task);
1030         }
1031         stutter_task = NULL;
1032         if (shuffler_task) {
1033                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
1034                 kthread_stop(shuffler_task);
1035                 free_cpumask_var(shuffle_tmp_mask);
1036         }
1037         shuffler_task = NULL;
1038
1039         if (writer_task) {
1040                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1041                 kthread_stop(writer_task);
1042         }
1043         writer_task = NULL;
1044
1045         if (reader_tasks) {
1046                 for (i = 0; i < nrealreaders; i++) {
1047                         if (reader_tasks[i]) {
1048                                 VERBOSE_PRINTK_STRING(
1049                                         "Stopping rcu_torture_reader task");
1050                                 kthread_stop(reader_tasks[i]);
1051                         }
1052                         reader_tasks[i] = NULL;
1053                 }
1054                 kfree(reader_tasks);
1055                 reader_tasks = NULL;
1056         }
1057         rcu_torture_current = NULL;
1058
1059         if (fakewriter_tasks) {
1060                 for (i = 0; i < nfakewriters; i++) {
1061                         if (fakewriter_tasks[i]) {
1062                                 VERBOSE_PRINTK_STRING(
1063                                         "Stopping rcu_torture_fakewriter task");
1064                                 kthread_stop(fakewriter_tasks[i]);
1065                         }
1066                         fakewriter_tasks[i] = NULL;
1067                 }
1068                 kfree(fakewriter_tasks);
1069                 fakewriter_tasks = NULL;
1070         }
1071
1072         if (stats_task) {
1073                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1074                 kthread_stop(stats_task);
1075         }
1076         stats_task = NULL;
1077
1078         /* Wait for all RCU callbacks to fire.  */
1079
1080         if (cur_ops->cb_barrier != NULL)
1081                 cur_ops->cb_barrier();
1082
1083         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1084
1085         if (cur_ops->cleanup)
1086                 cur_ops->cleanup();
1087         if (atomic_read(&n_rcu_torture_error))
1088                 rcu_torture_print_module_parms("End of test: FAILURE");
1089         else
1090                 rcu_torture_print_module_parms("End of test: SUCCESS");
1091 }
1092
1093 static int __init
1094 rcu_torture_init(void)
1095 {
1096         int i;
1097         int cpu;
1098         int firsterr = 0;
1099         static struct rcu_torture_ops *torture_ops[] =
1100                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1101                   &sched_expedited_ops,
1102                   &srcu_ops, &sched_ops, &sched_ops_sync, };
1103
1104         mutex_lock(&fullstop_mutex);
1105
1106         /* Process args and tell the world that the torturer is on the job. */
1107         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1108                 cur_ops = torture_ops[i];
1109                 if (strcmp(torture_type, cur_ops->name) == 0)
1110                         break;
1111         }
1112         if (i == ARRAY_SIZE(torture_ops)) {
1113                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1114                        torture_type);
1115                 mutex_unlock(&fullstop_mutex);
1116                 return (-EINVAL);
1117         }
1118         if (cur_ops->init)
1119                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1120
1121         if (nreaders >= 0)
1122                 nrealreaders = nreaders;
1123         else
1124                 nrealreaders = 2 * num_online_cpus();
1125         rcu_torture_print_module_parms("Start of test");
1126         fullstop = FULLSTOP_DONTSTOP;
1127
1128         /* Set up the freelist. */
1129
1130         INIT_LIST_HEAD(&rcu_torture_freelist);
1131         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1132                 rcu_tortures[i].rtort_mbtest = 0;
1133                 list_add_tail(&rcu_tortures[i].rtort_free,
1134                               &rcu_torture_freelist);
1135         }
1136
1137         /* Initialize the statistics so that each run gets its own numbers. */
1138
1139         rcu_torture_current = NULL;
1140         rcu_torture_current_version = 0;
1141         atomic_set(&n_rcu_torture_alloc, 0);
1142         atomic_set(&n_rcu_torture_alloc_fail, 0);
1143         atomic_set(&n_rcu_torture_free, 0);
1144         atomic_set(&n_rcu_torture_mberror, 0);
1145         atomic_set(&n_rcu_torture_error, 0);
1146         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1147                 atomic_set(&rcu_torture_wcount[i], 0);
1148         for_each_possible_cpu(cpu) {
1149                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1150                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1151                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1152                 }
1153         }
1154
1155         /* Start up the kthreads. */
1156
1157         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1158         writer_task = kthread_run(rcu_torture_writer, NULL,
1159                                   "rcu_torture_writer");
1160         if (IS_ERR(writer_task)) {
1161                 firsterr = PTR_ERR(writer_task);
1162                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1163                 writer_task = NULL;
1164                 goto unwind;
1165         }
1166         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1167                                    GFP_KERNEL);
1168         if (fakewriter_tasks == NULL) {
1169                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1170                 firsterr = -ENOMEM;
1171                 goto unwind;
1172         }
1173         for (i = 0; i < nfakewriters; i++) {
1174                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1175                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1176                                                   "rcu_torture_fakewriter");
1177                 if (IS_ERR(fakewriter_tasks[i])) {
1178                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1179                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1180                         fakewriter_tasks[i] = NULL;
1181                         goto unwind;
1182                 }
1183         }
1184         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1185                                GFP_KERNEL);
1186         if (reader_tasks == NULL) {
1187                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1188                 firsterr = -ENOMEM;
1189                 goto unwind;
1190         }
1191         for (i = 0; i < nrealreaders; i++) {
1192                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1193                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1194                                               "rcu_torture_reader");
1195                 if (IS_ERR(reader_tasks[i])) {
1196                         firsterr = PTR_ERR(reader_tasks[i]);
1197                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1198                         reader_tasks[i] = NULL;
1199                         goto unwind;
1200                 }
1201         }
1202         if (stat_interval > 0) {
1203                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1204                 stats_task = kthread_run(rcu_torture_stats, NULL,
1205                                         "rcu_torture_stats");
1206                 if (IS_ERR(stats_task)) {
1207                         firsterr = PTR_ERR(stats_task);
1208                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1209                         stats_task = NULL;
1210                         goto unwind;
1211                 }
1212         }
1213         if (test_no_idle_hz) {
1214                 rcu_idle_cpu = num_online_cpus() - 1;
1215
1216                 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1217                         firsterr = -ENOMEM;
1218                         VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1219                         goto unwind;
1220                 }
1221
1222                 /* Create the shuffler thread */
1223                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1224                                           "rcu_torture_shuffle");
1225                 if (IS_ERR(shuffler_task)) {
1226                         free_cpumask_var(shuffle_tmp_mask);
1227                         firsterr = PTR_ERR(shuffler_task);
1228                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1229                         shuffler_task = NULL;
1230                         goto unwind;
1231                 }
1232         }
1233         if (stutter < 0)
1234                 stutter = 0;
1235         if (stutter) {
1236                 /* Create the stutter thread */
1237                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1238                                           "rcu_torture_stutter");
1239                 if (IS_ERR(stutter_task)) {
1240                         firsterr = PTR_ERR(stutter_task);
1241                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1242                         stutter_task = NULL;
1243                         goto unwind;
1244                 }
1245         }
1246         register_reboot_notifier(&rcutorture_nb);
1247         mutex_unlock(&fullstop_mutex);
1248         return 0;
1249
1250 unwind:
1251         mutex_unlock(&fullstop_mutex);
1252         rcu_torture_cleanup();
1253         return firsterr;
1254 }
1255
1256 module_init(rcu_torture_init);
1257 module_exit(rcu_torture_cleanup);