[PATCH] rcutorture: add call_rcu_bh() operations
[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
19  *
20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
21  *
22  * See also:  Documentation/RCU/torture.txt
23  */
24 #include <linux/types.h>
25 #include <linux/kernel.h>
26 #include <linux/init.h>
27 #include <linux/module.h>
28 #include <linux/kthread.h>
29 #include <linux/err.h>
30 #include <linux/spinlock.h>
31 #include <linux/smp.h>
32 #include <linux/rcupdate.h>
33 #include <linux/interrupt.h>
34 #include <linux/sched.h>
35 #include <asm/atomic.h>
36 #include <linux/bitops.h>
37 #include <linux/module.h>
38 #include <linux/completion.h>
39 #include <linux/moduleparam.h>
40 #include <linux/percpu.h>
41 #include <linux/notifier.h>
42 #include <linux/cpu.h>
43 #include <linux/random.h>
44 #include <linux/delay.h>
45 #include <linux/byteorder/swabb.h>
46 #include <linux/stat.h>
47
48 MODULE_LICENSE("GPL");
49
50 static int nreaders = -1;       /* # reader threads, defaults to 4*ncpus */
51 static int stat_interval;       /* Interval between stats, in seconds. */
52                                 /*  Defaults to "only at end of test". */
53 static int verbose;             /* Print more debug info. */
54 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
55 static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
56 static char *torture_type = "rcu"; /* What to torture. */
57
58 module_param(nreaders, int, 0);
59 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
60 module_param(stat_interval, int, 0);
61 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
62 module_param(verbose, bool, 0);
63 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
64 module_param(test_no_idle_hz, bool, 0);
65 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
66 module_param(shuffle_interval, int, 0);
67 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
68 module_param(torture_type, charp, 0);
69 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh)");
70
71 #define TORTURE_FLAG "-torture:"
72 #define PRINTK_STRING(s) \
73         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
74 #define VERBOSE_PRINTK_STRING(s) \
75         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
76 #define VERBOSE_PRINTK_ERRSTRING(s) \
77         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
78
79 static char printk_buf[4096];
80
81 static int nrealreaders;
82 static struct task_struct *writer_task;
83 static struct task_struct **reader_tasks;
84 static struct task_struct *stats_task;
85 static struct task_struct *shuffler_task;
86
87 #define RCU_TORTURE_PIPE_LEN 10
88
89 struct rcu_torture {
90         struct rcu_head rtort_rcu;
91         int rtort_pipe_count;
92         struct list_head rtort_free;
93         int rtort_mbtest;
94 };
95
96 static int fullstop = 0;        /* stop generating callbacks at test end. */
97 static LIST_HEAD(rcu_torture_freelist);
98 static struct rcu_torture *rcu_torture_current = NULL;
99 static long rcu_torture_current_version = 0;
100 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
101 static DEFINE_SPINLOCK(rcu_torture_lock);
102 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
103         { 0 };
104 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
105         { 0 };
106 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
107 atomic_t n_rcu_torture_alloc;
108 atomic_t n_rcu_torture_alloc_fail;
109 atomic_t n_rcu_torture_free;
110 atomic_t n_rcu_torture_mberror;
111 atomic_t n_rcu_torture_error;
112
113 /*
114  * Allocate an element from the rcu_tortures pool.
115  */
116 static struct rcu_torture *
117 rcu_torture_alloc(void)
118 {
119         struct list_head *p;
120
121         spin_lock_bh(&rcu_torture_lock);
122         if (list_empty(&rcu_torture_freelist)) {
123                 atomic_inc(&n_rcu_torture_alloc_fail);
124                 spin_unlock_bh(&rcu_torture_lock);
125                 return NULL;
126         }
127         atomic_inc(&n_rcu_torture_alloc);
128         p = rcu_torture_freelist.next;
129         list_del_init(p);
130         spin_unlock_bh(&rcu_torture_lock);
131         return container_of(p, struct rcu_torture, rtort_free);
132 }
133
134 /*
135  * Free an element to the rcu_tortures pool.
136  */
137 static void
138 rcu_torture_free(struct rcu_torture *p)
139 {
140         atomic_inc(&n_rcu_torture_free);
141         spin_lock_bh(&rcu_torture_lock);
142         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
143         spin_unlock_bh(&rcu_torture_lock);
144 }
145
146 struct rcu_random_state {
147         unsigned long rrs_state;
148         unsigned long rrs_count;
149 };
150
151 #define RCU_RANDOM_MULT 39916801  /* prime */
152 #define RCU_RANDOM_ADD  479001701 /* prime */
153 #define RCU_RANDOM_REFRESH 10000
154
155 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
156
157 /*
158  * Crude but fast random-number generator.  Uses a linear congruential
159  * generator, with occasional help from get_random_bytes().
160  */
161 static long
162 rcu_random(struct rcu_random_state *rrsp)
163 {
164         long refresh;
165
166         if (--rrsp->rrs_count < 0) {
167                 get_random_bytes(&refresh, sizeof(refresh));
168                 rrsp->rrs_state += refresh;
169                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
170         }
171         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
172         return swahw32(rrsp->rrs_state);
173 }
174
175 /*
176  * Operations vector for selecting different types of tests.
177  */
178
179 struct rcu_torture_ops {
180         void (*init)(void);
181         void (*cleanup)(void);
182         int (*readlock)(void);
183         void (*readunlock)(int idx);
184         int (*completed)(void);
185         void (*deferredfree)(struct rcu_torture *p);
186         int (*stats)(char *page);
187         char *name;
188 };
189 static struct rcu_torture_ops *cur_ops = NULL;
190
191 /*
192  * Definitions for rcu torture testing.
193  */
194
195 static int rcu_torture_read_lock(void)
196 {
197         rcu_read_lock();
198         return 0;
199 }
200
201 static void rcu_torture_read_unlock(int idx)
202 {
203         rcu_read_unlock();
204 }
205
206 static int rcu_torture_completed(void)
207 {
208         return rcu_batches_completed();
209 }
210
211 static void
212 rcu_torture_cb(struct rcu_head *p)
213 {
214         int i;
215         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
216
217         if (fullstop) {
218                 /* Test is ending, just drop callbacks on the floor. */
219                 /* The next initialization will pick up the pieces. */
220                 return;
221         }
222         i = rp->rtort_pipe_count;
223         if (i > RCU_TORTURE_PIPE_LEN)
224                 i = RCU_TORTURE_PIPE_LEN;
225         atomic_inc(&rcu_torture_wcount[i]);
226         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
227                 rp->rtort_mbtest = 0;
228                 rcu_torture_free(rp);
229         } else
230                 cur_ops->deferredfree(rp);
231 }
232
233 static void rcu_torture_deferred_free(struct rcu_torture *p)
234 {
235         call_rcu(&p->rtort_rcu, rcu_torture_cb);
236 }
237
238 static struct rcu_torture_ops rcu_ops = {
239         .init = NULL,
240         .cleanup = NULL,
241         .readlock = rcu_torture_read_lock,
242         .readunlock = rcu_torture_read_unlock,
243         .completed = rcu_torture_completed,
244         .deferredfree = rcu_torture_deferred_free,
245         .stats = NULL,
246         .name = "rcu"
247 };
248
249 /*
250  * Definitions for rcu_bh torture testing.
251  */
252
253 static int rcu_bh_torture_read_lock(void)
254 {
255         rcu_read_lock_bh();
256         return 0;
257 }
258
259 static void rcu_bh_torture_read_unlock(int idx)
260 {
261         rcu_read_unlock_bh();
262 }
263
264 static int rcu_bh_torture_completed(void)
265 {
266         return rcu_batches_completed_bh();
267 }
268
269 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
270 {
271         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
272 }
273
274 static struct rcu_torture_ops rcu_bh_ops = {
275         .init = NULL,
276         .cleanup = NULL,
277         .readlock = rcu_bh_torture_read_lock,
278         .readunlock = rcu_bh_torture_read_unlock,
279         .completed = rcu_bh_torture_completed,
280         .deferredfree = rcu_bh_torture_deferred_free,
281         .stats = NULL,
282         .name = "rcu_bh"
283 };
284
285 static struct rcu_torture_ops *torture_ops[] =
286         { &rcu_ops, &rcu_bh_ops, NULL };
287
288 /*
289  * RCU torture writer kthread.  Repeatedly substitutes a new structure
290  * for that pointed to by rcu_torture_current, freeing the old structure
291  * after a series of grace periods (the "pipeline").
292  */
293 static int
294 rcu_torture_writer(void *arg)
295 {
296         int i;
297         long oldbatch = rcu_batches_completed();
298         struct rcu_torture *rp;
299         struct rcu_torture *old_rp;
300         static DEFINE_RCU_RANDOM(rand);
301
302         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
303         set_user_nice(current, 19);
304
305         do {
306                 schedule_timeout_uninterruptible(1);
307                 if ((rp = rcu_torture_alloc()) == NULL)
308                         continue;
309                 rp->rtort_pipe_count = 0;
310                 udelay(rcu_random(&rand) & 0x3ff);
311                 old_rp = rcu_torture_current;
312                 rp->rtort_mbtest = 1;
313                 rcu_assign_pointer(rcu_torture_current, rp);
314                 smp_wmb();
315                 if (old_rp != NULL) {
316                         i = old_rp->rtort_pipe_count;
317                         if (i > RCU_TORTURE_PIPE_LEN)
318                                 i = RCU_TORTURE_PIPE_LEN;
319                         atomic_inc(&rcu_torture_wcount[i]);
320                         old_rp->rtort_pipe_count++;
321                         cur_ops->deferredfree(old_rp);
322                 }
323                 rcu_torture_current_version++;
324                 oldbatch = cur_ops->completed();
325         } while (!kthread_should_stop() && !fullstop);
326         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
327         while (!kthread_should_stop())
328                 schedule_timeout_uninterruptible(1);
329         return 0;
330 }
331
332 /*
333  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
334  * incrementing the corresponding element of the pipeline array.  The
335  * counter in the element should never be greater than 1, otherwise, the
336  * RCU implementation is broken.
337  */
338 static int
339 rcu_torture_reader(void *arg)
340 {
341         int completed;
342         int idx;
343         DEFINE_RCU_RANDOM(rand);
344         struct rcu_torture *p;
345         int pipe_count;
346
347         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
348         set_user_nice(current, 19);
349
350         do {
351                 idx = cur_ops->readlock();
352                 completed = cur_ops->completed();
353                 p = rcu_dereference(rcu_torture_current);
354                 if (p == NULL) {
355                         /* Wait for rcu_torture_writer to get underway */
356                         cur_ops->readunlock(idx);
357                         schedule_timeout_interruptible(HZ);
358                         continue;
359                 }
360                 if (p->rtort_mbtest == 0)
361                         atomic_inc(&n_rcu_torture_mberror);
362                 udelay(rcu_random(&rand) & 0x7f);
363                 preempt_disable();
364                 pipe_count = p->rtort_pipe_count;
365                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
366                         /* Should not happen, but... */
367                         pipe_count = RCU_TORTURE_PIPE_LEN;
368                 }
369                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
370                 completed = cur_ops->completed() - completed;
371                 if (completed > RCU_TORTURE_PIPE_LEN) {
372                         /* Should not happen, but... */
373                         completed = RCU_TORTURE_PIPE_LEN;
374                 }
375                 ++__get_cpu_var(rcu_torture_batch)[completed];
376                 preempt_enable();
377                 cur_ops->readunlock(idx);
378                 schedule();
379         } while (!kthread_should_stop() && !fullstop);
380         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
381         while (!kthread_should_stop())
382                 schedule_timeout_uninterruptible(1);
383         return 0;
384 }
385
386 /*
387  * Create an RCU-torture statistics message in the specified buffer.
388  */
389 static int
390 rcu_torture_printk(char *page)
391 {
392         int cnt = 0;
393         int cpu;
394         int i;
395         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
396         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
397
398         for_each_possible_cpu(cpu) {
399                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
400                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
401                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
402                 }
403         }
404         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
405                 if (pipesummary[i] != 0)
406                         break;
407         }
408         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
409         cnt += sprintf(&page[cnt],
410                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
411                        "rtmbe: %d",
412                        rcu_torture_current,
413                        rcu_torture_current_version,
414                        list_empty(&rcu_torture_freelist),
415                        atomic_read(&n_rcu_torture_alloc),
416                        atomic_read(&n_rcu_torture_alloc_fail),
417                        atomic_read(&n_rcu_torture_free),
418                        atomic_read(&n_rcu_torture_mberror));
419         if (atomic_read(&n_rcu_torture_mberror) != 0)
420                 cnt += sprintf(&page[cnt], " !!!");
421         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
422         if (i > 1) {
423                 cnt += sprintf(&page[cnt], "!!! ");
424                 atomic_inc(&n_rcu_torture_error);
425         }
426         cnt += sprintf(&page[cnt], "Reader Pipe: ");
427         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
428                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
429         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
430         cnt += sprintf(&page[cnt], "Reader Batch: ");
431         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
432                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
433         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
434         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
435         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
436                 cnt += sprintf(&page[cnt], " %d",
437                                atomic_read(&rcu_torture_wcount[i]));
438         }
439         cnt += sprintf(&page[cnt], "\n");
440         if (cur_ops->stats != NULL)
441                 cnt += cur_ops->stats(&page[cnt]);
442         return cnt;
443 }
444
445 /*
446  * Print torture statistics.  Caller must ensure that there is only
447  * one call to this function at a given time!!!  This is normally
448  * accomplished by relying on the module system to only have one copy
449  * of the module loaded, and then by giving the rcu_torture_stats
450  * kthread full control (or the init/cleanup functions when rcu_torture_stats
451  * thread is not running).
452  */
453 static void
454 rcu_torture_stats_print(void)
455 {
456         int cnt;
457
458         cnt = rcu_torture_printk(printk_buf);
459         printk(KERN_ALERT "%s", printk_buf);
460 }
461
462 /*
463  * Periodically prints torture statistics, if periodic statistics printing
464  * was specified via the stat_interval module parameter.
465  *
466  * No need to worry about fullstop here, since this one doesn't reference
467  * volatile state or register callbacks.
468  */
469 static int
470 rcu_torture_stats(void *arg)
471 {
472         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
473         do {
474                 schedule_timeout_interruptible(stat_interval * HZ);
475                 rcu_torture_stats_print();
476         } while (!kthread_should_stop());
477         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
478         return 0;
479 }
480
481 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
482
483 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
484  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
485  */
486 void rcu_torture_shuffle_tasks(void)
487 {
488         cpumask_t tmp_mask = CPU_MASK_ALL;
489         int i;
490
491         lock_cpu_hotplug();
492
493         /* No point in shuffling if there is only one online CPU (ex: UP) */
494         if (num_online_cpus() == 1) {
495                 unlock_cpu_hotplug();
496                 return;
497         }
498
499         if (rcu_idle_cpu != -1)
500                 cpu_clear(rcu_idle_cpu, tmp_mask);
501
502         set_cpus_allowed(current, tmp_mask);
503
504         if (reader_tasks != NULL) {
505                 for (i = 0; i < nrealreaders; i++)
506                         if (reader_tasks[i])
507                                 set_cpus_allowed(reader_tasks[i], tmp_mask);
508         }
509
510         if (writer_task)
511                 set_cpus_allowed(writer_task, tmp_mask);
512
513         if (stats_task)
514                 set_cpus_allowed(stats_task, tmp_mask);
515
516         if (rcu_idle_cpu == -1)
517                 rcu_idle_cpu = num_online_cpus() - 1;
518         else
519                 rcu_idle_cpu--;
520
521         unlock_cpu_hotplug();
522 }
523
524 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
525  * system to become idle at a time and cut off its timer ticks. This is meant
526  * to test the support for such tickless idle CPU in RCU.
527  */
528 static int
529 rcu_torture_shuffle(void *arg)
530 {
531         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
532         do {
533                 schedule_timeout_interruptible(shuffle_interval * HZ);
534                 rcu_torture_shuffle_tasks();
535         } while (!kthread_should_stop());
536         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
537         return 0;
538 }
539
540 static inline void
541 rcu_torture_print_module_parms(char *tag)
542 {
543         printk(KERN_ALERT "%s" TORTURE_FLAG "--- %s: nreaders=%d "
544                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
545                 "shuffle_interval = %d\n",
546                 torture_type, tag, nrealreaders, stat_interval, verbose,
547                 test_no_idle_hz, shuffle_interval);
548 }
549
550 static void
551 rcu_torture_cleanup(void)
552 {
553         int i;
554
555         fullstop = 1;
556         if (shuffler_task != NULL) {
557                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
558                 kthread_stop(shuffler_task);
559         }
560         shuffler_task = NULL;
561
562         if (writer_task != NULL) {
563                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
564                 kthread_stop(writer_task);
565         }
566         writer_task = NULL;
567
568         if (reader_tasks != NULL) {
569                 for (i = 0; i < nrealreaders; i++) {
570                         if (reader_tasks[i] != NULL) {
571                                 VERBOSE_PRINTK_STRING(
572                                         "Stopping rcu_torture_reader task");
573                                 kthread_stop(reader_tasks[i]);
574                         }
575                         reader_tasks[i] = NULL;
576                 }
577                 kfree(reader_tasks);
578                 reader_tasks = NULL;
579         }
580         rcu_torture_current = NULL;
581
582         if (stats_task != NULL) {
583                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
584                 kthread_stop(stats_task);
585         }
586         stats_task = NULL;
587
588         /* Wait for all RCU callbacks to fire.  */
589         rcu_barrier();
590
591         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
592
593         if (cur_ops->cleanup != NULL)
594                 cur_ops->cleanup();
595         if (atomic_read(&n_rcu_torture_error))
596                 rcu_torture_print_module_parms("End of test: FAILURE");
597         else
598                 rcu_torture_print_module_parms("End of test: SUCCESS");
599 }
600
601 static int
602 rcu_torture_init(void)
603 {
604         int i;
605         int cpu;
606         int firsterr = 0;
607
608         /* Process args and tell the world that the torturer is on the job. */
609
610         for (i = 0; cur_ops = torture_ops[i], cur_ops != NULL; i++) {
611                 cur_ops = torture_ops[i];
612                 if (strcmp(torture_type, cur_ops->name) == 0) {
613                         break;
614                 }
615         }
616         if (cur_ops == NULL) {
617                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
618                        torture_type);
619                 return (-EINVAL);
620         }
621         if (cur_ops->init != NULL)
622                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
623
624         if (nreaders >= 0)
625                 nrealreaders = nreaders;
626         else
627                 nrealreaders = 2 * num_online_cpus();
628         rcu_torture_print_module_parms("Start of test");
629         fullstop = 0;
630
631         /* Set up the freelist. */
632
633         INIT_LIST_HEAD(&rcu_torture_freelist);
634         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
635                 rcu_tortures[i].rtort_mbtest = 0;
636                 list_add_tail(&rcu_tortures[i].rtort_free,
637                               &rcu_torture_freelist);
638         }
639
640         /* Initialize the statistics so that each run gets its own numbers. */
641
642         rcu_torture_current = NULL;
643         rcu_torture_current_version = 0;
644         atomic_set(&n_rcu_torture_alloc, 0);
645         atomic_set(&n_rcu_torture_alloc_fail, 0);
646         atomic_set(&n_rcu_torture_free, 0);
647         atomic_set(&n_rcu_torture_mberror, 0);
648         atomic_set(&n_rcu_torture_error, 0);
649         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
650                 atomic_set(&rcu_torture_wcount[i], 0);
651         for_each_possible_cpu(cpu) {
652                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
653                         per_cpu(rcu_torture_count, cpu)[i] = 0;
654                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
655                 }
656         }
657
658         /* Start up the kthreads. */
659
660         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
661         writer_task = kthread_run(rcu_torture_writer, NULL,
662                                   "rcu_torture_writer");
663         if (IS_ERR(writer_task)) {
664                 firsterr = PTR_ERR(writer_task);
665                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
666                 writer_task = NULL;
667                 goto unwind;
668         }
669         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
670                                GFP_KERNEL);
671         if (reader_tasks == NULL) {
672                 VERBOSE_PRINTK_ERRSTRING("out of memory");
673                 firsterr = -ENOMEM;
674                 goto unwind;
675         }
676         for (i = 0; i < nrealreaders; i++) {
677                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
678                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
679                                               "rcu_torture_reader");
680                 if (IS_ERR(reader_tasks[i])) {
681                         firsterr = PTR_ERR(reader_tasks[i]);
682                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
683                         reader_tasks[i] = NULL;
684                         goto unwind;
685                 }
686         }
687         if (stat_interval > 0) {
688                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
689                 stats_task = kthread_run(rcu_torture_stats, NULL,
690                                         "rcu_torture_stats");
691                 if (IS_ERR(stats_task)) {
692                         firsterr = PTR_ERR(stats_task);
693                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
694                         stats_task = NULL;
695                         goto unwind;
696                 }
697         }
698         if (test_no_idle_hz) {
699                 rcu_idle_cpu = num_online_cpus() - 1;
700                 /* Create the shuffler thread */
701                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
702                                           "rcu_torture_shuffle");
703                 if (IS_ERR(shuffler_task)) {
704                         firsterr = PTR_ERR(shuffler_task);
705                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
706                         shuffler_task = NULL;
707                         goto unwind;
708                 }
709         }
710         return 0;
711
712 unwind:
713         rcu_torture_cleanup();
714         return firsterr;
715 }
716
717 module_init(rcu_torture_init);
718 module_exit(rcu_torture_cleanup);