rcu: Add synchronize_sched_expedited() torture tests
[linux-2.6.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         long delay;
285         const long longdelay = 200;
286
287         /* We want there to be long-running readers, but not all the time. */
288
289         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
290         if (!delay)
291                 udelay(longdelay);
292 }
293
294 static void rcu_torture_read_unlock(int idx) __releases(RCU)
295 {
296         rcu_read_unlock();
297 }
298
299 static int rcu_torture_completed(void)
300 {
301         return rcu_batches_completed();
302 }
303
304 static void
305 rcu_torture_cb(struct rcu_head *p)
306 {
307         int i;
308         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
309
310         if (fullstop != FULLSTOP_DONTSTOP) {
311                 /* Test is ending, just drop callbacks on the floor. */
312                 /* The next initialization will pick up the pieces. */
313                 return;
314         }
315         i = rp->rtort_pipe_count;
316         if (i > RCU_TORTURE_PIPE_LEN)
317                 i = RCU_TORTURE_PIPE_LEN;
318         atomic_inc(&rcu_torture_wcount[i]);
319         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
320                 rp->rtort_mbtest = 0;
321                 rcu_torture_free(rp);
322         } else
323                 cur_ops->deferred_free(rp);
324 }
325
326 static void rcu_torture_deferred_free(struct rcu_torture *p)
327 {
328         call_rcu(&p->rtort_rcu, rcu_torture_cb);
329 }
330
331 static struct rcu_torture_ops rcu_ops = {
332         .init           = NULL,
333         .cleanup        = NULL,
334         .readlock       = rcu_torture_read_lock,
335         .read_delay     = rcu_read_delay,
336         .readunlock     = rcu_torture_read_unlock,
337         .completed      = rcu_torture_completed,
338         .deferred_free  = rcu_torture_deferred_free,
339         .sync           = synchronize_rcu,
340         .cb_barrier     = rcu_barrier,
341         .stats          = NULL,
342         .irq_capable    = 1,
343         .name           = "rcu"
344 };
345
346 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
347 {
348         int i;
349         struct rcu_torture *rp;
350         struct rcu_torture *rp1;
351
352         cur_ops->sync();
353         list_add(&p->rtort_free, &rcu_torture_removed);
354         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
355                 i = rp->rtort_pipe_count;
356                 if (i > RCU_TORTURE_PIPE_LEN)
357                         i = RCU_TORTURE_PIPE_LEN;
358                 atomic_inc(&rcu_torture_wcount[i]);
359                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
360                         rp->rtort_mbtest = 0;
361                         list_del(&rp->rtort_free);
362                         rcu_torture_free(rp);
363                 }
364         }
365 }
366
367 static void rcu_sync_torture_init(void)
368 {
369         INIT_LIST_HEAD(&rcu_torture_removed);
370 }
371
372 static struct rcu_torture_ops rcu_sync_ops = {
373         .init           = rcu_sync_torture_init,
374         .cleanup        = NULL,
375         .readlock       = rcu_torture_read_lock,
376         .read_delay     = rcu_read_delay,
377         .readunlock     = rcu_torture_read_unlock,
378         .completed      = rcu_torture_completed,
379         .deferred_free  = rcu_sync_torture_deferred_free,
380         .sync           = synchronize_rcu,
381         .cb_barrier     = NULL,
382         .stats          = NULL,
383         .irq_capable    = 1,
384         .name           = "rcu_sync"
385 };
386
387 /*
388  * Definitions for rcu_bh torture testing.
389  */
390
391 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
392 {
393         rcu_read_lock_bh();
394         return 0;
395 }
396
397 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
398 {
399         rcu_read_unlock_bh();
400 }
401
402 static int rcu_bh_torture_completed(void)
403 {
404         return rcu_batches_completed_bh();
405 }
406
407 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
408 {
409         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
410 }
411
412 struct rcu_bh_torture_synchronize {
413         struct rcu_head head;
414         struct completion completion;
415 };
416
417 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
418 {
419         struct rcu_bh_torture_synchronize *rcu;
420
421         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
422         complete(&rcu->completion);
423 }
424
425 static void rcu_bh_torture_synchronize(void)
426 {
427         struct rcu_bh_torture_synchronize rcu;
428
429         init_completion(&rcu.completion);
430         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
431         wait_for_completion(&rcu.completion);
432 }
433
434 static struct rcu_torture_ops rcu_bh_ops = {
435         .init           = NULL,
436         .cleanup        = NULL,
437         .readlock       = rcu_bh_torture_read_lock,
438         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
439         .readunlock     = rcu_bh_torture_read_unlock,
440         .completed      = rcu_bh_torture_completed,
441         .deferred_free  = rcu_bh_torture_deferred_free,
442         .sync           = rcu_bh_torture_synchronize,
443         .cb_barrier     = rcu_barrier_bh,
444         .stats          = NULL,
445         .irq_capable    = 1,
446         .name           = "rcu_bh"
447 };
448
449 static struct rcu_torture_ops rcu_bh_sync_ops = {
450         .init           = rcu_sync_torture_init,
451         .cleanup        = NULL,
452         .readlock       = rcu_bh_torture_read_lock,
453         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
454         .readunlock     = rcu_bh_torture_read_unlock,
455         .completed      = rcu_bh_torture_completed,
456         .deferred_free  = rcu_sync_torture_deferred_free,
457         .sync           = rcu_bh_torture_synchronize,
458         .cb_barrier     = NULL,
459         .stats          = NULL,
460         .irq_capable    = 1,
461         .name           = "rcu_bh_sync"
462 };
463
464 /*
465  * Definitions for srcu torture testing.
466  */
467
468 static struct srcu_struct srcu_ctl;
469
470 static void srcu_torture_init(void)
471 {
472         init_srcu_struct(&srcu_ctl);
473         rcu_sync_torture_init();
474 }
475
476 static void srcu_torture_cleanup(void)
477 {
478         synchronize_srcu(&srcu_ctl);
479         cleanup_srcu_struct(&srcu_ctl);
480 }
481
482 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
483 {
484         return srcu_read_lock(&srcu_ctl);
485 }
486
487 static void srcu_read_delay(struct rcu_random_state *rrsp)
488 {
489         long delay;
490         const long uspertick = 1000000 / HZ;
491         const long longdelay = 10;
492
493         /* We want there to be long-running readers, but not all the time. */
494
495         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
496         if (!delay)
497                 schedule_timeout_interruptible(longdelay);
498 }
499
500 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
501 {
502         srcu_read_unlock(&srcu_ctl, idx);
503 }
504
505 static int srcu_torture_completed(void)
506 {
507         return srcu_batches_completed(&srcu_ctl);
508 }
509
510 static void srcu_torture_synchronize(void)
511 {
512         synchronize_srcu(&srcu_ctl);
513 }
514
515 static int srcu_torture_stats(char *page)
516 {
517         int cnt = 0;
518         int cpu;
519         int idx = srcu_ctl.completed & 0x1;
520
521         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
522                        torture_type, TORTURE_FLAG, idx);
523         for_each_possible_cpu(cpu) {
524                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
525                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
526                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
527         }
528         cnt += sprintf(&page[cnt], "\n");
529         return cnt;
530 }
531
532 static struct rcu_torture_ops srcu_ops = {
533         .init           = srcu_torture_init,
534         .cleanup        = srcu_torture_cleanup,
535         .readlock       = srcu_torture_read_lock,
536         .read_delay     = srcu_read_delay,
537         .readunlock     = srcu_torture_read_unlock,
538         .completed      = srcu_torture_completed,
539         .deferred_free  = rcu_sync_torture_deferred_free,
540         .sync           = srcu_torture_synchronize,
541         .cb_barrier     = NULL,
542         .stats          = srcu_torture_stats,
543         .name           = "srcu"
544 };
545
546 /*
547  * Definitions for sched torture testing.
548  */
549
550 static int sched_torture_read_lock(void)
551 {
552         preempt_disable();
553         return 0;
554 }
555
556 static void sched_torture_read_unlock(int idx)
557 {
558         preempt_enable();
559 }
560
561 static int sched_torture_completed(void)
562 {
563         return 0;
564 }
565
566 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
567 {
568         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
569 }
570
571 static void sched_torture_synchronize(void)
572 {
573         synchronize_sched();
574 }
575
576 static struct rcu_torture_ops sched_ops = {
577         .init           = rcu_sync_torture_init,
578         .cleanup        = NULL,
579         .readlock       = sched_torture_read_lock,
580         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
581         .readunlock     = sched_torture_read_unlock,
582         .completed      = sched_torture_completed,
583         .deferred_free  = rcu_sched_torture_deferred_free,
584         .sync           = sched_torture_synchronize,
585         .cb_barrier     = rcu_barrier_sched,
586         .stats          = NULL,
587         .irq_capable    = 1,
588         .name           = "sched"
589 };
590
591 static struct rcu_torture_ops sched_ops_sync = {
592         .init           = rcu_sync_torture_init,
593         .cleanup        = NULL,
594         .readlock       = sched_torture_read_lock,
595         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
596         .readunlock     = sched_torture_read_unlock,
597         .completed      = sched_torture_completed,
598         .deferred_free  = rcu_sync_torture_deferred_free,
599         .sync           = sched_torture_synchronize,
600         .cb_barrier     = NULL,
601         .stats          = NULL,
602         .name           = "sched_sync"
603 };
604
605 extern int rcu_expedited_torture_stats(char *page);
606
607 static struct rcu_torture_ops sched_expedited_ops = {
608         .init           = rcu_sync_torture_init,
609         .cleanup        = NULL,
610         .readlock       = sched_torture_read_lock,
611         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
612         .readunlock     = sched_torture_read_unlock,
613         .completed      = sched_torture_completed,
614         .deferred_free  = rcu_sync_torture_deferred_free,
615         .sync           = synchronize_sched_expedited,
616         .cb_barrier     = NULL,
617         .stats          = rcu_expedited_torture_stats,
618         .irq_capable    = 1,
619         .name           = "sched_expedited"
620 };
621
622 /*
623  * RCU torture writer kthread.  Repeatedly substitutes a new structure
624  * for that pointed to by rcu_torture_current, freeing the old structure
625  * after a series of grace periods (the "pipeline").
626  */
627 static int
628 rcu_torture_writer(void *arg)
629 {
630         int i;
631         long oldbatch = rcu_batches_completed();
632         struct rcu_torture *rp;
633         struct rcu_torture *old_rp;
634         static DEFINE_RCU_RANDOM(rand);
635
636         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
637         set_user_nice(current, 19);
638
639         do {
640                 schedule_timeout_uninterruptible(1);
641                 if ((rp = rcu_torture_alloc()) == NULL)
642                         continue;
643                 rp->rtort_pipe_count = 0;
644                 udelay(rcu_random(&rand) & 0x3ff);
645                 old_rp = rcu_torture_current;
646                 rp->rtort_mbtest = 1;
647                 rcu_assign_pointer(rcu_torture_current, rp);
648                 smp_wmb();
649                 if (old_rp) {
650                         i = old_rp->rtort_pipe_count;
651                         if (i > RCU_TORTURE_PIPE_LEN)
652                                 i = RCU_TORTURE_PIPE_LEN;
653                         atomic_inc(&rcu_torture_wcount[i]);
654                         old_rp->rtort_pipe_count++;
655                         cur_ops->deferred_free(old_rp);
656                 }
657                 rcu_torture_current_version++;
658                 oldbatch = cur_ops->completed();
659                 rcu_stutter_wait("rcu_torture_writer");
660         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
661         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
662         rcutorture_shutdown_absorb("rcu_torture_writer");
663         while (!kthread_should_stop())
664                 schedule_timeout_uninterruptible(1);
665         return 0;
666 }
667
668 /*
669  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
670  * delay between calls.
671  */
672 static int
673 rcu_torture_fakewriter(void *arg)
674 {
675         DEFINE_RCU_RANDOM(rand);
676
677         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
678         set_user_nice(current, 19);
679
680         do {
681                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
682                 udelay(rcu_random(&rand) & 0x3ff);
683                 cur_ops->sync();
684                 rcu_stutter_wait("rcu_torture_fakewriter");
685         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
686
687         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
688         rcutorture_shutdown_absorb("rcu_torture_fakewriter");
689         while (!kthread_should_stop())
690                 schedule_timeout_uninterruptible(1);
691         return 0;
692 }
693
694 /*
695  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
696  * incrementing the corresponding element of the pipeline array.  The
697  * counter in the element should never be greater than 1, otherwise, the
698  * RCU implementation is broken.
699  */
700 static void rcu_torture_timer(unsigned long unused)
701 {
702         int idx;
703         int completed;
704         static DEFINE_RCU_RANDOM(rand);
705         static DEFINE_SPINLOCK(rand_lock);
706         struct rcu_torture *p;
707         int pipe_count;
708
709         idx = cur_ops->readlock();
710         completed = cur_ops->completed();
711         p = rcu_dereference(rcu_torture_current);
712         if (p == NULL) {
713                 /* Leave because rcu_torture_writer is not yet underway */
714                 cur_ops->readunlock(idx);
715                 return;
716         }
717         if (p->rtort_mbtest == 0)
718                 atomic_inc(&n_rcu_torture_mberror);
719         spin_lock(&rand_lock);
720         cur_ops->read_delay(&rand);
721         n_rcu_torture_timers++;
722         spin_unlock(&rand_lock);
723         preempt_disable();
724         pipe_count = p->rtort_pipe_count;
725         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
726                 /* Should not happen, but... */
727                 pipe_count = RCU_TORTURE_PIPE_LEN;
728         }
729         ++__get_cpu_var(rcu_torture_count)[pipe_count];
730         completed = cur_ops->completed() - completed;
731         if (completed > RCU_TORTURE_PIPE_LEN) {
732                 /* Should not happen, but... */
733                 completed = RCU_TORTURE_PIPE_LEN;
734         }
735         ++__get_cpu_var(rcu_torture_batch)[completed];
736         preempt_enable();
737         cur_ops->readunlock(idx);
738 }
739
740 /*
741  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
742  * incrementing the corresponding element of the pipeline array.  The
743  * counter in the element should never be greater than 1, otherwise, the
744  * RCU implementation is broken.
745  */
746 static int
747 rcu_torture_reader(void *arg)
748 {
749         int completed;
750         int idx;
751         DEFINE_RCU_RANDOM(rand);
752         struct rcu_torture *p;
753         int pipe_count;
754         struct timer_list t;
755
756         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
757         set_user_nice(current, 19);
758         if (irqreader && cur_ops->irq_capable)
759                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
760
761         do {
762                 if (irqreader && cur_ops->irq_capable) {
763                         if (!timer_pending(&t))
764                                 mod_timer(&t, 1);
765                 }
766                 idx = cur_ops->readlock();
767                 completed = cur_ops->completed();
768                 p = rcu_dereference(rcu_torture_current);
769                 if (p == NULL) {
770                         /* Wait for rcu_torture_writer to get underway */
771                         cur_ops->readunlock(idx);
772                         schedule_timeout_interruptible(HZ);
773                         continue;
774                 }
775                 if (p->rtort_mbtest == 0)
776                         atomic_inc(&n_rcu_torture_mberror);
777                 cur_ops->read_delay(&rand);
778                 preempt_disable();
779                 pipe_count = p->rtort_pipe_count;
780                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
781                         /* Should not happen, but... */
782                         pipe_count = RCU_TORTURE_PIPE_LEN;
783                 }
784                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
785                 completed = cur_ops->completed() - completed;
786                 if (completed > RCU_TORTURE_PIPE_LEN) {
787                         /* Should not happen, but... */
788                         completed = RCU_TORTURE_PIPE_LEN;
789                 }
790                 ++__get_cpu_var(rcu_torture_batch)[completed];
791                 preempt_enable();
792                 cur_ops->readunlock(idx);
793                 schedule();
794                 rcu_stutter_wait("rcu_torture_reader");
795         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
796         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
797         rcutorture_shutdown_absorb("rcu_torture_reader");
798         if (irqreader && cur_ops->irq_capable)
799                 del_timer_sync(&t);
800         while (!kthread_should_stop())
801                 schedule_timeout_uninterruptible(1);
802         return 0;
803 }
804
805 /*
806  * Create an RCU-torture statistics message in the specified buffer.
807  */
808 static int
809 rcu_torture_printk(char *page)
810 {
811         int cnt = 0;
812         int cpu;
813         int i;
814         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
815         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
816
817         for_each_possible_cpu(cpu) {
818                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
819                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
820                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
821                 }
822         }
823         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
824                 if (pipesummary[i] != 0)
825                         break;
826         }
827         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
828         cnt += sprintf(&page[cnt],
829                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
830                        "rtmbe: %d nt: %ld",
831                        rcu_torture_current,
832                        rcu_torture_current_version,
833                        list_empty(&rcu_torture_freelist),
834                        atomic_read(&n_rcu_torture_alloc),
835                        atomic_read(&n_rcu_torture_alloc_fail),
836                        atomic_read(&n_rcu_torture_free),
837                        atomic_read(&n_rcu_torture_mberror),
838                        n_rcu_torture_timers);
839         if (atomic_read(&n_rcu_torture_mberror) != 0)
840                 cnt += sprintf(&page[cnt], " !!!");
841         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
842         if (i > 1) {
843                 cnt += sprintf(&page[cnt], "!!! ");
844                 atomic_inc(&n_rcu_torture_error);
845                 WARN_ON_ONCE(1);
846         }
847         cnt += sprintf(&page[cnt], "Reader Pipe: ");
848         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
849                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
850         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
851         cnt += sprintf(&page[cnt], "Reader Batch: ");
852         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
853                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
854         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
855         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
856         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
857                 cnt += sprintf(&page[cnt], " %d",
858                                atomic_read(&rcu_torture_wcount[i]));
859         }
860         cnt += sprintf(&page[cnt], "\n");
861         if (cur_ops->stats)
862                 cnt += cur_ops->stats(&page[cnt]);
863         return cnt;
864 }
865
866 /*
867  * Print torture statistics.  Caller must ensure that there is only
868  * one call to this function at a given time!!!  This is normally
869  * accomplished by relying on the module system to only have one copy
870  * of the module loaded, and then by giving the rcu_torture_stats
871  * kthread full control (or the init/cleanup functions when rcu_torture_stats
872  * thread is not running).
873  */
874 static void
875 rcu_torture_stats_print(void)
876 {
877         int cnt;
878
879         cnt = rcu_torture_printk(printk_buf);
880         printk(KERN_ALERT "%s", printk_buf);
881 }
882
883 /*
884  * Periodically prints torture statistics, if periodic statistics printing
885  * was specified via the stat_interval module parameter.
886  *
887  * No need to worry about fullstop here, since this one doesn't reference
888  * volatile state or register callbacks.
889  */
890 static int
891 rcu_torture_stats(void *arg)
892 {
893         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
894         do {
895                 schedule_timeout_interruptible(stat_interval * HZ);
896                 rcu_torture_stats_print();
897                 rcutorture_shutdown_absorb("rcu_torture_stats");
898         } while (!kthread_should_stop());
899         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
900         return 0;
901 }
902
903 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
904
905 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
906  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
907  */
908 static void rcu_torture_shuffle_tasks(void)
909 {
910         int i;
911
912         cpumask_setall(shuffle_tmp_mask);
913         get_online_cpus();
914
915         /* No point in shuffling if there is only one online CPU (ex: UP) */
916         if (num_online_cpus() == 1) {
917                 put_online_cpus();
918                 return;
919         }
920
921         if (rcu_idle_cpu != -1)
922                 cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
923
924         set_cpus_allowed_ptr(current, shuffle_tmp_mask);
925
926         if (reader_tasks) {
927                 for (i = 0; i < nrealreaders; i++)
928                         if (reader_tasks[i])
929                                 set_cpus_allowed_ptr(reader_tasks[i],
930                                                      shuffle_tmp_mask);
931         }
932
933         if (fakewriter_tasks) {
934                 for (i = 0; i < nfakewriters; i++)
935                         if (fakewriter_tasks[i])
936                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
937                                                      shuffle_tmp_mask);
938         }
939
940         if (writer_task)
941                 set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
942
943         if (stats_task)
944                 set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
945
946         if (rcu_idle_cpu == -1)
947                 rcu_idle_cpu = num_online_cpus() - 1;
948         else
949                 rcu_idle_cpu--;
950
951         put_online_cpus();
952 }
953
954 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
955  * system to become idle at a time and cut off its timer ticks. This is meant
956  * to test the support for such tickless idle CPU in RCU.
957  */
958 static int
959 rcu_torture_shuffle(void *arg)
960 {
961         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
962         do {
963                 schedule_timeout_interruptible(shuffle_interval * HZ);
964                 rcu_torture_shuffle_tasks();
965                 rcutorture_shutdown_absorb("rcu_torture_shuffle");
966         } while (!kthread_should_stop());
967         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
968         return 0;
969 }
970
971 /* Cause the rcutorture test to "stutter", starting and stopping all
972  * threads periodically.
973  */
974 static int
975 rcu_torture_stutter(void *arg)
976 {
977         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
978         do {
979                 schedule_timeout_interruptible(stutter * HZ);
980                 stutter_pause_test = 1;
981                 if (!kthread_should_stop())
982                         schedule_timeout_interruptible(stutter * HZ);
983                 stutter_pause_test = 0;
984                 rcutorture_shutdown_absorb("rcu_torture_stutter");
985         } while (!kthread_should_stop());
986         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
987         return 0;
988 }
989
990 static inline void
991 rcu_torture_print_module_parms(char *tag)
992 {
993         printk(KERN_ALERT "%s" TORTURE_FLAG
994                 "--- %s: nreaders=%d nfakewriters=%d "
995                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
996                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
997                 torture_type, tag, nrealreaders, nfakewriters,
998                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
999                 stutter, irqreader);
1000 }
1001
1002 static struct notifier_block rcutorture_nb = {
1003         .notifier_call = rcutorture_shutdown_notify,
1004 };
1005
1006 static void
1007 rcu_torture_cleanup(void)
1008 {
1009         int i;
1010
1011         mutex_lock(&fullstop_mutex);
1012         if (fullstop == FULLSTOP_SHUTDOWN) {
1013                 printk(KERN_WARNING /* but going down anyway, so... */
1014                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
1015                 mutex_unlock(&fullstop_mutex);
1016                 schedule_timeout_uninterruptible(10);
1017                 if (cur_ops->cb_barrier != NULL)
1018                         cur_ops->cb_barrier();
1019                 return;
1020         }
1021         fullstop = FULLSTOP_RMMOD;
1022         mutex_unlock(&fullstop_mutex);
1023         unregister_reboot_notifier(&rcutorture_nb);
1024         if (stutter_task) {
1025                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
1026                 kthread_stop(stutter_task);
1027         }
1028         stutter_task = NULL;
1029         if (shuffler_task) {
1030                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
1031                 kthread_stop(shuffler_task);
1032                 free_cpumask_var(shuffle_tmp_mask);
1033         }
1034         shuffler_task = NULL;
1035
1036         if (writer_task) {
1037                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1038                 kthread_stop(writer_task);
1039         }
1040         writer_task = NULL;
1041
1042         if (reader_tasks) {
1043                 for (i = 0; i < nrealreaders; i++) {
1044                         if (reader_tasks[i]) {
1045                                 VERBOSE_PRINTK_STRING(
1046                                         "Stopping rcu_torture_reader task");
1047                                 kthread_stop(reader_tasks[i]);
1048                         }
1049                         reader_tasks[i] = NULL;
1050                 }
1051                 kfree(reader_tasks);
1052                 reader_tasks = NULL;
1053         }
1054         rcu_torture_current = NULL;
1055
1056         if (fakewriter_tasks) {
1057                 for (i = 0; i < nfakewriters; i++) {
1058                         if (fakewriter_tasks[i]) {
1059                                 VERBOSE_PRINTK_STRING(
1060                                         "Stopping rcu_torture_fakewriter task");
1061                                 kthread_stop(fakewriter_tasks[i]);
1062                         }
1063                         fakewriter_tasks[i] = NULL;
1064                 }
1065                 kfree(fakewriter_tasks);
1066                 fakewriter_tasks = NULL;
1067         }
1068
1069         if (stats_task) {
1070                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1071                 kthread_stop(stats_task);
1072         }
1073         stats_task = NULL;
1074
1075         /* Wait for all RCU callbacks to fire.  */
1076
1077         if (cur_ops->cb_barrier != NULL)
1078                 cur_ops->cb_barrier();
1079
1080         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1081
1082         if (cur_ops->cleanup)
1083                 cur_ops->cleanup();
1084         if (atomic_read(&n_rcu_torture_error))
1085                 rcu_torture_print_module_parms("End of test: FAILURE");
1086         else
1087                 rcu_torture_print_module_parms("End of test: SUCCESS");
1088 }
1089
1090 static int __init
1091 rcu_torture_init(void)
1092 {
1093         int i;
1094         int cpu;
1095         int firsterr = 0;
1096         static struct rcu_torture_ops *torture_ops[] =
1097                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1098                   &sched_expedited_ops,
1099                   &srcu_ops, &sched_ops, &sched_ops_sync, };
1100
1101         mutex_lock(&fullstop_mutex);
1102
1103         /* Process args and tell the world that the torturer is on the job. */
1104         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1105                 cur_ops = torture_ops[i];
1106                 if (strcmp(torture_type, cur_ops->name) == 0)
1107                         break;
1108         }
1109         if (i == ARRAY_SIZE(torture_ops)) {
1110                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1111                        torture_type);
1112                 mutex_unlock(&fullstop_mutex);
1113                 return (-EINVAL);
1114         }
1115         if (cur_ops->init)
1116                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1117
1118         if (nreaders >= 0)
1119                 nrealreaders = nreaders;
1120         else
1121                 nrealreaders = 2 * num_online_cpus();
1122         rcu_torture_print_module_parms("Start of test");
1123         fullstop = FULLSTOP_DONTSTOP;
1124
1125         /* Set up the freelist. */
1126
1127         INIT_LIST_HEAD(&rcu_torture_freelist);
1128         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1129                 rcu_tortures[i].rtort_mbtest = 0;
1130                 list_add_tail(&rcu_tortures[i].rtort_free,
1131                               &rcu_torture_freelist);
1132         }
1133
1134         /* Initialize the statistics so that each run gets its own numbers. */
1135
1136         rcu_torture_current = NULL;
1137         rcu_torture_current_version = 0;
1138         atomic_set(&n_rcu_torture_alloc, 0);
1139         atomic_set(&n_rcu_torture_alloc_fail, 0);
1140         atomic_set(&n_rcu_torture_free, 0);
1141         atomic_set(&n_rcu_torture_mberror, 0);
1142         atomic_set(&n_rcu_torture_error, 0);
1143         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1144                 atomic_set(&rcu_torture_wcount[i], 0);
1145         for_each_possible_cpu(cpu) {
1146                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1147                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1148                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1149                 }
1150         }
1151
1152         /* Start up the kthreads. */
1153
1154         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1155         writer_task = kthread_run(rcu_torture_writer, NULL,
1156                                   "rcu_torture_writer");
1157         if (IS_ERR(writer_task)) {
1158                 firsterr = PTR_ERR(writer_task);
1159                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1160                 writer_task = NULL;
1161                 goto unwind;
1162         }
1163         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1164                                    GFP_KERNEL);
1165         if (fakewriter_tasks == NULL) {
1166                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1167                 firsterr = -ENOMEM;
1168                 goto unwind;
1169         }
1170         for (i = 0; i < nfakewriters; i++) {
1171                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1172                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1173                                                   "rcu_torture_fakewriter");
1174                 if (IS_ERR(fakewriter_tasks[i])) {
1175                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1176                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1177                         fakewriter_tasks[i] = NULL;
1178                         goto unwind;
1179                 }
1180         }
1181         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1182                                GFP_KERNEL);
1183         if (reader_tasks == NULL) {
1184                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1185                 firsterr = -ENOMEM;
1186                 goto unwind;
1187         }
1188         for (i = 0; i < nrealreaders; i++) {
1189                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1190                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1191                                               "rcu_torture_reader");
1192                 if (IS_ERR(reader_tasks[i])) {
1193                         firsterr = PTR_ERR(reader_tasks[i]);
1194                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1195                         reader_tasks[i] = NULL;
1196                         goto unwind;
1197                 }
1198         }
1199         if (stat_interval > 0) {
1200                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1201                 stats_task = kthread_run(rcu_torture_stats, NULL,
1202                                         "rcu_torture_stats");
1203                 if (IS_ERR(stats_task)) {
1204                         firsterr = PTR_ERR(stats_task);
1205                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1206                         stats_task = NULL;
1207                         goto unwind;
1208                 }
1209         }
1210         if (test_no_idle_hz) {
1211                 rcu_idle_cpu = num_online_cpus() - 1;
1212
1213                 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1214                         firsterr = -ENOMEM;
1215                         VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1216                         goto unwind;
1217                 }
1218
1219                 /* Create the shuffler thread */
1220                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1221                                           "rcu_torture_shuffle");
1222                 if (IS_ERR(shuffler_task)) {
1223                         free_cpumask_var(shuffle_tmp_mask);
1224                         firsterr = PTR_ERR(shuffler_task);
1225                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1226                         shuffler_task = NULL;
1227                         goto unwind;
1228                 }
1229         }
1230         if (stutter < 0)
1231                 stutter = 0;
1232         if (stutter) {
1233                 /* Create the stutter thread */
1234                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1235                                           "rcu_torture_stutter");
1236                 if (IS_ERR(stutter_task)) {
1237                         firsterr = PTR_ERR(stutter_task);
1238                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1239                         stutter_task = NULL;
1240                         goto unwind;
1241                 }
1242         }
1243         register_reboot_notifier(&rcutorture_nb);
1244         mutex_unlock(&fullstop_mutex);
1245         return 0;
1246
1247 unwind:
1248         mutex_unlock(&fullstop_mutex);
1249         rcu_torture_cleanup();
1250         return firsterr;
1251 }
1252
1253 module_init(rcu_torture_init);
1254 module_exit(rcu_torture_cleanup);