[PATCH] rcu: Mention rcu_bh in description of rcutorture's torture_type parameter
[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 #include <linux/srcu.h>
48
49 MODULE_LICENSE("GPL");
50 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");
51
52 static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
53 static int stat_interval;       /* Interval between stats, in seconds. */
54                                 /*  Defaults to "only at end of test". */
55 static int verbose;             /* Print more debug info. */
56 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
57 static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
58 static char *torture_type = "rcu"; /* What to torture: rcu, rcu_bh, srcu. */
59
60 module_param(nreaders, int, 0);
61 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
62 module_param(stat_interval, int, 0);
63 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
64 module_param(verbose, bool, 0);
65 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
66 module_param(test_no_idle_hz, bool, 0);
67 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
68 module_param(shuffle_interval, int, 0);
69 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
70 module_param(torture_type, charp, 0);
71 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
72
73 #define TORTURE_FLAG "-torture:"
74 #define PRINTK_STRING(s) \
75         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
76 #define VERBOSE_PRINTK_STRING(s) \
77         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
78 #define VERBOSE_PRINTK_ERRSTRING(s) \
79         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
80
81 static char printk_buf[4096];
82
83 static int nrealreaders;
84 static struct task_struct *writer_task;
85 static struct task_struct **reader_tasks;
86 static struct task_struct *stats_task;
87 static struct task_struct *shuffler_task;
88
89 #define RCU_TORTURE_PIPE_LEN 10
90
91 struct rcu_torture {
92         struct rcu_head rtort_rcu;
93         int rtort_pipe_count;
94         struct list_head rtort_free;
95         int rtort_mbtest;
96 };
97
98 static int fullstop = 0;        /* stop generating callbacks at test end. */
99 static LIST_HEAD(rcu_torture_freelist);
100 static struct rcu_torture *rcu_torture_current = NULL;
101 static long rcu_torture_current_version = 0;
102 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
103 static DEFINE_SPINLOCK(rcu_torture_lock);
104 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
105         { 0 };
106 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
107         { 0 };
108 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
109 static atomic_t n_rcu_torture_alloc;
110 static atomic_t n_rcu_torture_alloc_fail;
111 static atomic_t n_rcu_torture_free;
112 static atomic_t n_rcu_torture_mberror;
113 static atomic_t n_rcu_torture_error;
114
115 /*
116  * Allocate an element from the rcu_tortures pool.
117  */
118 static struct rcu_torture *
119 rcu_torture_alloc(void)
120 {
121         struct list_head *p;
122
123         spin_lock_bh(&rcu_torture_lock);
124         if (list_empty(&rcu_torture_freelist)) {
125                 atomic_inc(&n_rcu_torture_alloc_fail);
126                 spin_unlock_bh(&rcu_torture_lock);
127                 return NULL;
128         }
129         atomic_inc(&n_rcu_torture_alloc);
130         p = rcu_torture_freelist.next;
131         list_del_init(p);
132         spin_unlock_bh(&rcu_torture_lock);
133         return container_of(p, struct rcu_torture, rtort_free);
134 }
135
136 /*
137  * Free an element to the rcu_tortures pool.
138  */
139 static void
140 rcu_torture_free(struct rcu_torture *p)
141 {
142         atomic_inc(&n_rcu_torture_free);
143         spin_lock_bh(&rcu_torture_lock);
144         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
145         spin_unlock_bh(&rcu_torture_lock);
146 }
147
148 struct rcu_random_state {
149         unsigned long rrs_state;
150         unsigned long rrs_count;
151 };
152
153 #define RCU_RANDOM_MULT 39916801  /* prime */
154 #define RCU_RANDOM_ADD  479001701 /* prime */
155 #define RCU_RANDOM_REFRESH 10000
156
157 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
158
159 /*
160  * Crude but fast random-number generator.  Uses a linear congruential
161  * generator, with occasional help from get_random_bytes().
162  */
163 static long
164 rcu_random(struct rcu_random_state *rrsp)
165 {
166         long refresh;
167
168         if (--rrsp->rrs_count < 0) {
169                 get_random_bytes(&refresh, sizeof(refresh));
170                 rrsp->rrs_state += refresh;
171                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
172         }
173         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
174         return swahw32(rrsp->rrs_state);
175 }
176
177 /*
178  * Operations vector for selecting different types of tests.
179  */
180
181 struct rcu_torture_ops {
182         void (*init)(void);
183         void (*cleanup)(void);
184         int (*readlock)(void);
185         void (*readdelay)(struct rcu_random_state *rrsp);
186         void (*readunlock)(int idx);
187         int (*completed)(void);
188         void (*deferredfree)(struct rcu_torture *p);
189         int (*stats)(char *page);
190         char *name;
191 };
192 static struct rcu_torture_ops *cur_ops = NULL;
193
194 /*
195  * Definitions for rcu torture testing.
196  */
197
198 static int rcu_torture_read_lock(void) __acquires(RCU)
199 {
200         rcu_read_lock();
201         return 0;
202 }
203
204 static void rcu_read_delay(struct rcu_random_state *rrsp)
205 {
206         long delay;
207         const long longdelay = 200;
208
209         /* We want there to be long-running readers, but not all the time. */
210
211         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
212         if (!delay)
213                 udelay(longdelay);
214 }
215
216 static void rcu_torture_read_unlock(int idx) __releases(RCU)
217 {
218         rcu_read_unlock();
219 }
220
221 static int rcu_torture_completed(void)
222 {
223         return rcu_batches_completed();
224 }
225
226 static void
227 rcu_torture_cb(struct rcu_head *p)
228 {
229         int i;
230         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
231
232         if (fullstop) {
233                 /* Test is ending, just drop callbacks on the floor. */
234                 /* The next initialization will pick up the pieces. */
235                 return;
236         }
237         i = rp->rtort_pipe_count;
238         if (i > RCU_TORTURE_PIPE_LEN)
239                 i = RCU_TORTURE_PIPE_LEN;
240         atomic_inc(&rcu_torture_wcount[i]);
241         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
242                 rp->rtort_mbtest = 0;
243                 rcu_torture_free(rp);
244         } else
245                 cur_ops->deferredfree(rp);
246 }
247
248 static void rcu_torture_deferred_free(struct rcu_torture *p)
249 {
250         call_rcu(&p->rtort_rcu, rcu_torture_cb);
251 }
252
253 static struct rcu_torture_ops rcu_ops = {
254         .init = NULL,
255         .cleanup = NULL,
256         .readlock = rcu_torture_read_lock,
257         .readdelay = rcu_read_delay,
258         .readunlock = rcu_torture_read_unlock,
259         .completed = rcu_torture_completed,
260         .deferredfree = rcu_torture_deferred_free,
261         .stats = NULL,
262         .name = "rcu"
263 };
264
265 /*
266  * Definitions for rcu_bh torture testing.
267  */
268
269 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
270 {
271         rcu_read_lock_bh();
272         return 0;
273 }
274
275 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
276 {
277         rcu_read_unlock_bh();
278 }
279
280 static int rcu_bh_torture_completed(void)
281 {
282         return rcu_batches_completed_bh();
283 }
284
285 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
286 {
287         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
288 }
289
290 static struct rcu_torture_ops rcu_bh_ops = {
291         .init = NULL,
292         .cleanup = NULL,
293         .readlock = rcu_bh_torture_read_lock,
294         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
295         .readunlock = rcu_bh_torture_read_unlock,
296         .completed = rcu_bh_torture_completed,
297         .deferredfree = rcu_bh_torture_deferred_free,
298         .stats = NULL,
299         .name = "rcu_bh"
300 };
301
302 /*
303  * Definitions for srcu torture testing.
304  */
305
306 static struct srcu_struct srcu_ctl;
307 static struct list_head srcu_removed;
308
309 static void srcu_torture_init(void)
310 {
311         init_srcu_struct(&srcu_ctl);
312         INIT_LIST_HEAD(&srcu_removed);
313 }
314
315 static void srcu_torture_cleanup(void)
316 {
317         synchronize_srcu(&srcu_ctl);
318         cleanup_srcu_struct(&srcu_ctl);
319 }
320
321 static int srcu_torture_read_lock(void)
322 {
323         return srcu_read_lock(&srcu_ctl);
324 }
325
326 static void srcu_read_delay(struct rcu_random_state *rrsp)
327 {
328         long delay;
329         const long uspertick = 1000000 / HZ;
330         const long longdelay = 10;
331
332         /* We want there to be long-running readers, but not all the time. */
333
334         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
335         if (!delay)
336                 schedule_timeout_interruptible(longdelay);
337 }
338
339 static void srcu_torture_read_unlock(int idx)
340 {
341         srcu_read_unlock(&srcu_ctl, idx);
342 }
343
344 static int srcu_torture_completed(void)
345 {
346         return srcu_batches_completed(&srcu_ctl);
347 }
348
349 static void srcu_torture_deferred_free(struct rcu_torture *p)
350 {
351         int i;
352         struct rcu_torture *rp;
353         struct rcu_torture *rp1;
354
355         synchronize_srcu(&srcu_ctl);
356         list_add(&p->rtort_free, &srcu_removed);
357         list_for_each_entry_safe(rp, rp1, &srcu_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 int srcu_torture_stats(char *page)
371 {
372         int cnt = 0;
373         int cpu;
374         int idx = srcu_ctl.completed & 0x1;
375
376         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
377                        torture_type, TORTURE_FLAG, idx);
378         for_each_possible_cpu(cpu) {
379                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
380                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
381                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
382         }
383         cnt += sprintf(&page[cnt], "\n");
384         return cnt;
385 }
386
387 static struct rcu_torture_ops srcu_ops = {
388         .init = srcu_torture_init,
389         .cleanup = srcu_torture_cleanup,
390         .readlock = srcu_torture_read_lock,
391         .readdelay = srcu_read_delay,
392         .readunlock = srcu_torture_read_unlock,
393         .completed = srcu_torture_completed,
394         .deferredfree = srcu_torture_deferred_free,
395         .stats = srcu_torture_stats,
396         .name = "srcu"
397 };
398
399 static struct rcu_torture_ops *torture_ops[] =
400         { &rcu_ops, &rcu_bh_ops, &srcu_ops, NULL };
401
402 /*
403  * RCU torture writer kthread.  Repeatedly substitutes a new structure
404  * for that pointed to by rcu_torture_current, freeing the old structure
405  * after a series of grace periods (the "pipeline").
406  */
407 static int
408 rcu_torture_writer(void *arg)
409 {
410         int i;
411         long oldbatch = rcu_batches_completed();
412         struct rcu_torture *rp;
413         struct rcu_torture *old_rp;
414         static DEFINE_RCU_RANDOM(rand);
415
416         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
417         set_user_nice(current, 19);
418
419         do {
420                 schedule_timeout_uninterruptible(1);
421                 if ((rp = rcu_torture_alloc()) == NULL)
422                         continue;
423                 rp->rtort_pipe_count = 0;
424                 udelay(rcu_random(&rand) & 0x3ff);
425                 old_rp = rcu_torture_current;
426                 rp->rtort_mbtest = 1;
427                 rcu_assign_pointer(rcu_torture_current, rp);
428                 smp_wmb();
429                 if (old_rp != NULL) {
430                         i = old_rp->rtort_pipe_count;
431                         if (i > RCU_TORTURE_PIPE_LEN)
432                                 i = RCU_TORTURE_PIPE_LEN;
433                         atomic_inc(&rcu_torture_wcount[i]);
434                         old_rp->rtort_pipe_count++;
435                         cur_ops->deferredfree(old_rp);
436                 }
437                 rcu_torture_current_version++;
438                 oldbatch = cur_ops->completed();
439         } while (!kthread_should_stop() && !fullstop);
440         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
441         while (!kthread_should_stop())
442                 schedule_timeout_uninterruptible(1);
443         return 0;
444 }
445
446 /*
447  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
448  * incrementing the corresponding element of the pipeline array.  The
449  * counter in the element should never be greater than 1, otherwise, the
450  * RCU implementation is broken.
451  */
452 static int
453 rcu_torture_reader(void *arg)
454 {
455         int completed;
456         int idx;
457         DEFINE_RCU_RANDOM(rand);
458         struct rcu_torture *p;
459         int pipe_count;
460
461         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
462         set_user_nice(current, 19);
463
464         do {
465                 idx = cur_ops->readlock();
466                 completed = cur_ops->completed();
467                 p = rcu_dereference(rcu_torture_current);
468                 if (p == NULL) {
469                         /* Wait for rcu_torture_writer to get underway */
470                         cur_ops->readunlock(idx);
471                         schedule_timeout_interruptible(HZ);
472                         continue;
473                 }
474                 if (p->rtort_mbtest == 0)
475                         atomic_inc(&n_rcu_torture_mberror);
476                 cur_ops->readdelay(&rand);
477                 preempt_disable();
478                 pipe_count = p->rtort_pipe_count;
479                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
480                         /* Should not happen, but... */
481                         pipe_count = RCU_TORTURE_PIPE_LEN;
482                 }
483                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
484                 completed = cur_ops->completed() - completed;
485                 if (completed > RCU_TORTURE_PIPE_LEN) {
486                         /* Should not happen, but... */
487                         completed = RCU_TORTURE_PIPE_LEN;
488                 }
489                 ++__get_cpu_var(rcu_torture_batch)[completed];
490                 preempt_enable();
491                 cur_ops->readunlock(idx);
492                 schedule();
493         } while (!kthread_should_stop() && !fullstop);
494         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
495         while (!kthread_should_stop())
496                 schedule_timeout_uninterruptible(1);
497         return 0;
498 }
499
500 /*
501  * Create an RCU-torture statistics message in the specified buffer.
502  */
503 static int
504 rcu_torture_printk(char *page)
505 {
506         int cnt = 0;
507         int cpu;
508         int i;
509         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
510         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
511
512         for_each_possible_cpu(cpu) {
513                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
514                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
515                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
516                 }
517         }
518         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
519                 if (pipesummary[i] != 0)
520                         break;
521         }
522         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
523         cnt += sprintf(&page[cnt],
524                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
525                        "rtmbe: %d",
526                        rcu_torture_current,
527                        rcu_torture_current_version,
528                        list_empty(&rcu_torture_freelist),
529                        atomic_read(&n_rcu_torture_alloc),
530                        atomic_read(&n_rcu_torture_alloc_fail),
531                        atomic_read(&n_rcu_torture_free),
532                        atomic_read(&n_rcu_torture_mberror));
533         if (atomic_read(&n_rcu_torture_mberror) != 0)
534                 cnt += sprintf(&page[cnt], " !!!");
535         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
536         if (i > 1) {
537                 cnt += sprintf(&page[cnt], "!!! ");
538                 atomic_inc(&n_rcu_torture_error);
539         }
540         cnt += sprintf(&page[cnt], "Reader Pipe: ");
541         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
542                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
543         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
544         cnt += sprintf(&page[cnt], "Reader Batch: ");
545         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
546                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
547         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
548         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
549         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
550                 cnt += sprintf(&page[cnt], " %d",
551                                atomic_read(&rcu_torture_wcount[i]));
552         }
553         cnt += sprintf(&page[cnt], "\n");
554         if (cur_ops->stats != NULL)
555                 cnt += cur_ops->stats(&page[cnt]);
556         return cnt;
557 }
558
559 /*
560  * Print torture statistics.  Caller must ensure that there is only
561  * one call to this function at a given time!!!  This is normally
562  * accomplished by relying on the module system to only have one copy
563  * of the module loaded, and then by giving the rcu_torture_stats
564  * kthread full control (or the init/cleanup functions when rcu_torture_stats
565  * thread is not running).
566  */
567 static void
568 rcu_torture_stats_print(void)
569 {
570         int cnt;
571
572         cnt = rcu_torture_printk(printk_buf);
573         printk(KERN_ALERT "%s", printk_buf);
574 }
575
576 /*
577  * Periodically prints torture statistics, if periodic statistics printing
578  * was specified via the stat_interval module parameter.
579  *
580  * No need to worry about fullstop here, since this one doesn't reference
581  * volatile state or register callbacks.
582  */
583 static int
584 rcu_torture_stats(void *arg)
585 {
586         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
587         do {
588                 schedule_timeout_interruptible(stat_interval * HZ);
589                 rcu_torture_stats_print();
590         } while (!kthread_should_stop());
591         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
592         return 0;
593 }
594
595 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
596
597 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
598  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
599  */
600 static void rcu_torture_shuffle_tasks(void)
601 {
602         cpumask_t tmp_mask = CPU_MASK_ALL;
603         int i;
604
605         lock_cpu_hotplug();
606
607         /* No point in shuffling if there is only one online CPU (ex: UP) */
608         if (num_online_cpus() == 1) {
609                 unlock_cpu_hotplug();
610                 return;
611         }
612
613         if (rcu_idle_cpu != -1)
614                 cpu_clear(rcu_idle_cpu, tmp_mask);
615
616         set_cpus_allowed(current, tmp_mask);
617
618         if (reader_tasks != NULL) {
619                 for (i = 0; i < nrealreaders; i++)
620                         if (reader_tasks[i])
621                                 set_cpus_allowed(reader_tasks[i], tmp_mask);
622         }
623
624         if (writer_task)
625                 set_cpus_allowed(writer_task, tmp_mask);
626
627         if (stats_task)
628                 set_cpus_allowed(stats_task, tmp_mask);
629
630         if (rcu_idle_cpu == -1)
631                 rcu_idle_cpu = num_online_cpus() - 1;
632         else
633                 rcu_idle_cpu--;
634
635         unlock_cpu_hotplug();
636 }
637
638 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
639  * system to become idle at a time and cut off its timer ticks. This is meant
640  * to test the support for such tickless idle CPU in RCU.
641  */
642 static int
643 rcu_torture_shuffle(void *arg)
644 {
645         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
646         do {
647                 schedule_timeout_interruptible(shuffle_interval * HZ);
648                 rcu_torture_shuffle_tasks();
649         } while (!kthread_should_stop());
650         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
651         return 0;
652 }
653
654 static inline void
655 rcu_torture_print_module_parms(char *tag)
656 {
657         printk(KERN_ALERT "%s" TORTURE_FLAG "--- %s: nreaders=%d "
658                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
659                 "shuffle_interval = %d\n",
660                 torture_type, tag, nrealreaders, stat_interval, verbose,
661                 test_no_idle_hz, shuffle_interval);
662 }
663
664 static void
665 rcu_torture_cleanup(void)
666 {
667         int i;
668
669         fullstop = 1;
670         if (shuffler_task != NULL) {
671                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
672                 kthread_stop(shuffler_task);
673         }
674         shuffler_task = NULL;
675
676         if (writer_task != NULL) {
677                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
678                 kthread_stop(writer_task);
679         }
680         writer_task = NULL;
681
682         if (reader_tasks != NULL) {
683                 for (i = 0; i < nrealreaders; i++) {
684                         if (reader_tasks[i] != NULL) {
685                                 VERBOSE_PRINTK_STRING(
686                                         "Stopping rcu_torture_reader task");
687                                 kthread_stop(reader_tasks[i]);
688                         }
689                         reader_tasks[i] = NULL;
690                 }
691                 kfree(reader_tasks);
692                 reader_tasks = NULL;
693         }
694         rcu_torture_current = NULL;
695
696         if (stats_task != NULL) {
697                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
698                 kthread_stop(stats_task);
699         }
700         stats_task = NULL;
701
702         /* Wait for all RCU callbacks to fire.  */
703         rcu_barrier();
704
705         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
706
707         if (cur_ops->cleanup != NULL)
708                 cur_ops->cleanup();
709         if (atomic_read(&n_rcu_torture_error))
710                 rcu_torture_print_module_parms("End of test: FAILURE");
711         else
712                 rcu_torture_print_module_parms("End of test: SUCCESS");
713 }
714
715 static int
716 rcu_torture_init(void)
717 {
718         int i;
719         int cpu;
720         int firsterr = 0;
721
722         /* Process args and tell the world that the torturer is on the job. */
723
724         for (i = 0; cur_ops = torture_ops[i], cur_ops != NULL; i++) {
725                 cur_ops = torture_ops[i];
726                 if (strcmp(torture_type, cur_ops->name) == 0) {
727                         break;
728                 }
729         }
730         if (cur_ops == NULL) {
731                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
732                        torture_type);
733                 return (-EINVAL);
734         }
735         if (cur_ops->init != NULL)
736                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
737
738         if (nreaders >= 0)
739                 nrealreaders = nreaders;
740         else
741                 nrealreaders = 2 * num_online_cpus();
742         rcu_torture_print_module_parms("Start of test");
743         fullstop = 0;
744
745         /* Set up the freelist. */
746
747         INIT_LIST_HEAD(&rcu_torture_freelist);
748         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
749                 rcu_tortures[i].rtort_mbtest = 0;
750                 list_add_tail(&rcu_tortures[i].rtort_free,
751                               &rcu_torture_freelist);
752         }
753
754         /* Initialize the statistics so that each run gets its own numbers. */
755
756         rcu_torture_current = NULL;
757         rcu_torture_current_version = 0;
758         atomic_set(&n_rcu_torture_alloc, 0);
759         atomic_set(&n_rcu_torture_alloc_fail, 0);
760         atomic_set(&n_rcu_torture_free, 0);
761         atomic_set(&n_rcu_torture_mberror, 0);
762         atomic_set(&n_rcu_torture_error, 0);
763         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
764                 atomic_set(&rcu_torture_wcount[i], 0);
765         for_each_possible_cpu(cpu) {
766                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
767                         per_cpu(rcu_torture_count, cpu)[i] = 0;
768                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
769                 }
770         }
771
772         /* Start up the kthreads. */
773
774         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
775         writer_task = kthread_run(rcu_torture_writer, NULL,
776                                   "rcu_torture_writer");
777         if (IS_ERR(writer_task)) {
778                 firsterr = PTR_ERR(writer_task);
779                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
780                 writer_task = NULL;
781                 goto unwind;
782         }
783         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
784                                GFP_KERNEL);
785         if (reader_tasks == NULL) {
786                 VERBOSE_PRINTK_ERRSTRING("out of memory");
787                 firsterr = -ENOMEM;
788                 goto unwind;
789         }
790         for (i = 0; i < nrealreaders; i++) {
791                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
792                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
793                                               "rcu_torture_reader");
794                 if (IS_ERR(reader_tasks[i])) {
795                         firsterr = PTR_ERR(reader_tasks[i]);
796                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
797                         reader_tasks[i] = NULL;
798                         goto unwind;
799                 }
800         }
801         if (stat_interval > 0) {
802                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
803                 stats_task = kthread_run(rcu_torture_stats, NULL,
804                                         "rcu_torture_stats");
805                 if (IS_ERR(stats_task)) {
806                         firsterr = PTR_ERR(stats_task);
807                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
808                         stats_task = NULL;
809                         goto unwind;
810                 }
811         }
812         if (test_no_idle_hz) {
813                 rcu_idle_cpu = num_online_cpus() - 1;
814                 /* Create the shuffler thread */
815                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
816                                           "rcu_torture_shuffle");
817                 if (IS_ERR(shuffler_task)) {
818                         firsterr = PTR_ERR(shuffler_task);
819                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
820                         shuffler_task = NULL;
821                         goto unwind;
822                 }
823         }
824         return 0;
825
826 unwind:
827         rcu_torture_cleanup();
828         return firsterr;
829 }
830
831 module_init(rcu_torture_init);
832 module_exit(rcu_torture_cleanup);