git.oblomov.eu Git - linux-2.6/blob - 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
 130 static int stutter_pause_test = 0;
 131
 132 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 133 #define RCUTORTURE_RUNNABLE_INIT 1
 134 #else
 135 #define RCUTORTURE_RUNNABLE_INIT 0
 136 #endif
 137 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 138
 139 #define FULLSTOP_SHUTDOWN 1     /* Bail due to system shutdown/panic. */
 140 #define FULLSTOP_CLEANUP  2     /* Orderly shutdown. */
 141 static int fullstop;            /* stop generating callbacks at test end. */
 142 DEFINE_MUTEX(fullstop_mutex);   /* protect fullstop transitions and */
 143                                 /*  spawning of kthreads. */
 144
 145 /*
 146  * Detect and respond to a signal-based shutdown.
 147  */
 148 static int
 149 rcutorture_shutdown_notify(struct notifier_block *unused1,
 150                            unsigned long unused2, void *unused3)
 151 {
 152         if (fullstop)
 153                 return NOTIFY_DONE;
 154         mutex_lock(&fullstop_mutex);
 155         if (!fullstop)
 156                 fullstop = FULLSTOP_SHUTDOWN;
 157         mutex_unlock(&fullstop_mutex);
 158         return NOTIFY_DONE;
 159 }
 160
 161 /*
 162  * Allocate an element from the rcu_tortures pool.
 163  */
 164 static struct rcu_torture *
 165 rcu_torture_alloc(void)
 166 {
 167         struct list_head *p;
 168
 169         spin_lock_bh(&rcu_torture_lock);
 170         if (list_empty(&rcu_torture_freelist)) {
 171                 atomic_inc(&n_rcu_torture_alloc_fail);
 172                 spin_unlock_bh(&rcu_torture_lock);
 173                 return NULL;
 174         }
 175         atomic_inc(&n_rcu_torture_alloc);
 176         p = rcu_torture_freelist.next;
 177         list_del_init(p);
 178         spin_unlock_bh(&rcu_torture_lock);
 179         return container_of(p, struct rcu_torture, rtort_free);
 180 }
 181
 182 /*
 183  * Free an element to the rcu_tortures pool.
 184  */
 185 static void
 186 rcu_torture_free(struct rcu_torture *p)
 187 {
 188         atomic_inc(&n_rcu_torture_free);
 189         spin_lock_bh(&rcu_torture_lock);
 190         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 191         spin_unlock_bh(&rcu_torture_lock);
 192 }
 193
 194 struct rcu_random_state {
 195         unsigned long rrs_state;
 196         long rrs_count;
 197 };
 198
 199 #define RCU_RANDOM_MULT 39916801  /* prime */
 200 #define RCU_RANDOM_ADD  479001701 /* prime */
 201 #define RCU_RANDOM_REFRESH 10000
 202
 203 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 204
 205 /*
 206  * Crude but fast random-number generator.  Uses a linear congruential
 207  * generator, with occasional help from cpu_clock().
 208  */
 209 static unsigned long
 210 rcu_random(struct rcu_random_state *rrsp)
 211 {
 212         if (--rrsp->rrs_count < 0) {
 213                 rrsp->rrs_state +=
 214                         (unsigned long)cpu_clock(raw_smp_processor_id());
 215                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 216         }
 217         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 218         return swahw32(rrsp->rrs_state);
 219 }
 220
 221 static void
 222 rcu_stutter_wait(void)
 223 {
 224         while ((stutter_pause_test || !rcutorture_runnable) && !fullstop) {
 225                 if (rcutorture_runnable)
 226                         schedule_timeout_interruptible(1);
 227                 else
 228                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 229         }
 230 }
 231
 232 /*
 233  * Operations vector for selecting different types of tests.
 234  */
 235
 236 struct rcu_torture_ops {
 237         void (*init)(void);
 238         void (*cleanup)(void);
 239         int (*readlock)(void);
 240         void (*readdelay)(struct rcu_random_state *rrsp);
 241         void (*readunlock)(int idx);
 242         int (*completed)(void);
 243         void (*deferredfree)(struct rcu_torture *p);
 244         void (*sync)(void);
 245         void (*cb_barrier)(void);
 246         int (*stats)(char *page);
 247         int irqcapable;
 248         char *name;
 249 };
 250 static struct rcu_torture_ops *cur_ops = NULL;
 251
 252 /*
 253  * Definitions for rcu torture testing.
 254  */
 255
 256 static int rcu_torture_read_lock(void) __acquires(RCU)
 257 {
 258         rcu_read_lock();
 259         return 0;
 260 }
 261
 262 static void rcu_read_delay(struct rcu_random_state *rrsp)
 263 {
 264         long delay;
 265         const long longdelay = 200;
 266
 267         /* We want there to be long-running readers, but not all the time. */
 268
 269         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
 270         if (!delay)
 271                 udelay(longdelay);
 272 }
 273
 274 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 275 {
 276         rcu_read_unlock();
 277 }
 278
 279 static int rcu_torture_completed(void)
 280 {
 281         return rcu_batches_completed();
 282 }
 283
 284 static void
 285 rcu_torture_cb(struct rcu_head *p)
 286 {
 287         int i;
 288         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 289
 290         if (fullstop) {
 291                 /* Test is ending, just drop callbacks on the floor. */
 292                 /* The next initialization will pick up the pieces. */
 293                 return;
 294         }
 295         i = rp->rtort_pipe_count;
 296         if (i > RCU_TORTURE_PIPE_LEN)
 297                 i = RCU_TORTURE_PIPE_LEN;
 298         atomic_inc(&rcu_torture_wcount[i]);
 299         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 300                 rp->rtort_mbtest = 0;
 301                 rcu_torture_free(rp);
 302         } else
 303                 cur_ops->deferredfree(rp);
 304 }
 305
 306 static void rcu_torture_deferred_free(struct rcu_torture *p)
 307 {
 308         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 309 }
 310
 311 static struct rcu_torture_ops rcu_ops = {
 312         .init = NULL,
 313         .cleanup = NULL,
 314         .readlock = rcu_torture_read_lock,
 315         .readdelay = rcu_read_delay,
 316         .readunlock = rcu_torture_read_unlock,
 317         .completed = rcu_torture_completed,
 318         .deferredfree = rcu_torture_deferred_free,
 319         .sync = synchronize_rcu,
 320         .cb_barrier = rcu_barrier,
 321         .stats = NULL,
 322         .irqcapable = 1,
 323         .name = "rcu"
 324 };
 325
 326 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 327 {
 328         int i;
 329         struct rcu_torture *rp;
 330         struct rcu_torture *rp1;
 331
 332         cur_ops->sync();
 333         list_add(&p->rtort_free, &rcu_torture_removed);
 334         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 335                 i = rp->rtort_pipe_count;
 336                 if (i > RCU_TORTURE_PIPE_LEN)
 337                         i = RCU_TORTURE_PIPE_LEN;
 338                 atomic_inc(&rcu_torture_wcount[i]);
 339                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 340                         rp->rtort_mbtest = 0;
 341                         list_del(&rp->rtort_free);
 342                         rcu_torture_free(rp);
 343                 }
 344         }
 345 }
 346
 347 static void rcu_sync_torture_init(void)
 348 {
 349         INIT_LIST_HEAD(&rcu_torture_removed);
 350 }
 351
 352 static struct rcu_torture_ops rcu_sync_ops = {
 353         .init = rcu_sync_torture_init,
 354         .cleanup = NULL,
 355         .readlock = rcu_torture_read_lock,
 356         .readdelay = rcu_read_delay,
 357         .readunlock = rcu_torture_read_unlock,
 358         .completed = rcu_torture_completed,
 359         .deferredfree = rcu_sync_torture_deferred_free,
 360         .sync = synchronize_rcu,
 361         .cb_barrier = NULL,
 362         .stats = NULL,
 363         .irqcapable = 1,
 364         .name = "rcu_sync"
 365 };
 366
 367 /*
 368  * Definitions for rcu_bh torture testing.
 369  */
 370
 371 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 372 {
 373         rcu_read_lock_bh();
 374         return 0;
 375 }
 376
 377 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 378 {
 379         rcu_read_unlock_bh();
 380 }
 381
 382 static int rcu_bh_torture_completed(void)
 383 {
 384         return rcu_batches_completed_bh();
 385 }
 386
 387 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 388 {
 389         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 390 }
 391
 392 struct rcu_bh_torture_synchronize {
 393         struct rcu_head head;
 394         struct completion completion;
 395 };
 396
 397 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 398 {
 399         struct rcu_bh_torture_synchronize *rcu;
 400
 401         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 402         complete(&rcu->completion);
 403 }
 404
 405 static void rcu_bh_torture_synchronize(void)
 406 {
 407         struct rcu_bh_torture_synchronize rcu;
 408
 409         init_completion(&rcu.completion);
 410         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 411         wait_for_completion(&rcu.completion);
 412 }
 413
 414 static struct rcu_torture_ops rcu_bh_ops = {
 415         .init = NULL,
 416         .cleanup = NULL,
 417         .readlock = rcu_bh_torture_read_lock,
 418         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 419         .readunlock = rcu_bh_torture_read_unlock,
 420         .completed = rcu_bh_torture_completed,
 421         .deferredfree = rcu_bh_torture_deferred_free,
 422         .sync = rcu_bh_torture_synchronize,
 423         .cb_barrier = rcu_barrier_bh,
 424         .stats = NULL,
 425         .irqcapable = 1,
 426         .name = "rcu_bh"
 427 };
 428
 429 static struct rcu_torture_ops rcu_bh_sync_ops = {
 430         .init = rcu_sync_torture_init,
 431         .cleanup = NULL,
 432         .readlock = rcu_bh_torture_read_lock,
 433         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 434         .readunlock = rcu_bh_torture_read_unlock,
 435         .completed = rcu_bh_torture_completed,
 436         .deferredfree = rcu_sync_torture_deferred_free,
 437         .sync = rcu_bh_torture_synchronize,
 438         .cb_barrier = NULL,
 439         .stats = NULL,
 440         .irqcapable = 1,
 441         .name = "rcu_bh_sync"
 442 };
 443
 444 /*
 445  * Definitions for srcu torture testing.
 446  */
 447
 448 static struct srcu_struct srcu_ctl;
 449
 450 static void srcu_torture_init(void)
 451 {
 452         init_srcu_struct(&srcu_ctl);
 453         rcu_sync_torture_init();
 454 }
 455
 456 static void srcu_torture_cleanup(void)
 457 {
 458         synchronize_srcu(&srcu_ctl);
 459         cleanup_srcu_struct(&srcu_ctl);
 460 }
 461
 462 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 463 {
 464         return srcu_read_lock(&srcu_ctl);
 465 }
 466
 467 static void srcu_read_delay(struct rcu_random_state *rrsp)
 468 {
 469         long delay;
 470         const long uspertick = 1000000 / HZ;
 471         const long longdelay = 10;
 472
 473         /* We want there to be long-running readers, but not all the time. */
 474
 475         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 476         if (!delay)
 477                 schedule_timeout_interruptible(longdelay);
 478 }
 479
 480 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 481 {
 482         srcu_read_unlock(&srcu_ctl, idx);
 483 }
 484
 485 static int srcu_torture_completed(void)
 486 {
 487         return srcu_batches_completed(&srcu_ctl);
 488 }
 489
 490 static void srcu_torture_synchronize(void)
 491 {
 492         synchronize_srcu(&srcu_ctl);
 493 }
 494
 495 static int srcu_torture_stats(char *page)
 496 {
 497         int cnt = 0;
 498         int cpu;
 499         int idx = srcu_ctl.completed & 0x1;
 500
 501         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 502                        torture_type, TORTURE_FLAG, idx);
 503         for_each_possible_cpu(cpu) {
 504                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 505                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 506                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 507         }
 508         cnt += sprintf(&page[cnt], "\n");
 509         return cnt;
 510 }
 511
 512 static struct rcu_torture_ops srcu_ops = {
 513         .init = srcu_torture_init,
 514         .cleanup = srcu_torture_cleanup,
 515         .readlock = srcu_torture_read_lock,
 516         .readdelay = srcu_read_delay,
 517         .readunlock = srcu_torture_read_unlock,
 518         .completed = srcu_torture_completed,
 519         .deferredfree = rcu_sync_torture_deferred_free,
 520         .sync = srcu_torture_synchronize,
 521         .cb_barrier = NULL,
 522         .stats = srcu_torture_stats,
 523         .name = "srcu"
 524 };
 525
 526 /*
 527  * Definitions for sched torture testing.
 528  */
 529
 530 static int sched_torture_read_lock(void)
 531 {
 532         preempt_disable();
 533         return 0;
 534 }
 535
 536 static void sched_torture_read_unlock(int idx)
 537 {
 538         preempt_enable();
 539 }
 540
 541 static int sched_torture_completed(void)
 542 {
 543         return 0;
 544 }
 545
 546 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 547 {
 548         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 549 }
 550
 551 static void sched_torture_synchronize(void)
 552 {
 553         synchronize_sched();
 554 }
 555
 556 static struct rcu_torture_ops sched_ops = {
 557         .init = rcu_sync_torture_init,
 558         .cleanup = NULL,
 559         .readlock = sched_torture_read_lock,
 560         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 561         .readunlock = sched_torture_read_unlock,
 562         .completed = sched_torture_completed,
 563         .deferredfree = rcu_sched_torture_deferred_free,
 564         .sync = sched_torture_synchronize,
 565         .cb_barrier = rcu_barrier_sched,
 566         .stats = NULL,
 567         .irqcapable = 1,
 568         .name = "sched"
 569 };
 570
 571 static struct rcu_torture_ops sched_ops_sync = {
 572         .init = rcu_sync_torture_init,
 573         .cleanup = NULL,
 574         .readlock = sched_torture_read_lock,
 575         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 576         .readunlock = sched_torture_read_unlock,
 577         .completed = sched_torture_completed,
 578         .deferredfree = rcu_sync_torture_deferred_free,
 579         .sync = sched_torture_synchronize,
 580         .cb_barrier = NULL,
 581         .stats = NULL,
 582         .name = "sched_sync"
 583 };
 584
 585 /*
 586  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 587  * for that pointed to by rcu_torture_current, freeing the old structure
 588  * after a series of grace periods (the "pipeline").
 589  */
 590 static int
 591 rcu_torture_writer(void *arg)
 592 {
 593         int i;
 594         long oldbatch = rcu_batches_completed();
 595         struct rcu_torture *rp;
 596         struct rcu_torture *old_rp;
 597         static DEFINE_RCU_RANDOM(rand);
 598
 599         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 600         set_user_nice(current, 19);
 601
 602         do {
 603                 schedule_timeout_uninterruptible(1);
 604                 if ((rp = rcu_torture_alloc()) == NULL)
 605                         continue;
 606                 rp->rtort_pipe_count = 0;
 607                 udelay(rcu_random(&rand) & 0x3ff);
 608                 old_rp = rcu_torture_current;
 609                 rp->rtort_mbtest = 1;
 610                 rcu_assign_pointer(rcu_torture_current, rp);
 611                 smp_wmb();
 612                 if (old_rp) {
 613                         i = old_rp->rtort_pipe_count;
 614                         if (i > RCU_TORTURE_PIPE_LEN)
 615                                 i = RCU_TORTURE_PIPE_LEN;
 616                         atomic_inc(&rcu_torture_wcount[i]);
 617                         old_rp->rtort_pipe_count++;
 618                         cur_ops->deferredfree(old_rp);
 619                 }
 620                 rcu_torture_current_version++;
 621                 oldbatch = cur_ops->completed();
 622                 rcu_stutter_wait();
 623         } while (!kthread_should_stop() && !fullstop);
 624         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 625         while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN)
 626                 schedule_timeout_uninterruptible(1);
 627         return 0;
 628 }
 629
 630 /*
 631  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 632  * delay between calls.
 633  */
 634 static int
 635 rcu_torture_fakewriter(void *arg)
 636 {
 637         DEFINE_RCU_RANDOM(rand);
 638
 639         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 640         set_user_nice(current, 19);
 641
 642         do {
 643                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 644                 udelay(rcu_random(&rand) & 0x3ff);
 645                 cur_ops->sync();
 646                 rcu_stutter_wait();
 647         } while (!kthread_should_stop() && !fullstop);
 648
 649         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 650         while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN)
 651                 schedule_timeout_uninterruptible(1);
 652         return 0;
 653 }
 654
 655 /*
 656  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 657  * incrementing the corresponding element of the pipeline array.  The
 658  * counter in the element should never be greater than 1, otherwise, the
 659  * RCU implementation is broken.
 660  */
 661 static void rcu_torture_timer(unsigned long unused)
 662 {
 663         int idx;
 664         int completed;
 665         static DEFINE_RCU_RANDOM(rand);
 666         static DEFINE_SPINLOCK(rand_lock);
 667         struct rcu_torture *p;
 668         int pipe_count;
 669
 670         idx = cur_ops->readlock();
 671         completed = cur_ops->completed();
 672         p = rcu_dereference(rcu_torture_current);
 673         if (p == NULL) {
 674                 /* Leave because rcu_torture_writer is not yet underway */
 675                 cur_ops->readunlock(idx);
 676                 return;
 677         }
 678         if (p->rtort_mbtest == 0)
 679                 atomic_inc(&n_rcu_torture_mberror);
 680         spin_lock(&rand_lock);
 681         cur_ops->readdelay(&rand);
 682         n_rcu_torture_timers++;
 683         spin_unlock(&rand_lock);
 684         preempt_disable();
 685         pipe_count = p->rtort_pipe_count;
 686         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 687                 /* Should not happen, but... */
 688                 pipe_count = RCU_TORTURE_PIPE_LEN;
 689         }
 690         ++__get_cpu_var(rcu_torture_count)[pipe_count];
 691         completed = cur_ops->completed() - completed;
 692         if (completed > RCU_TORTURE_PIPE_LEN) {
 693                 /* Should not happen, but... */
 694                 completed = RCU_TORTURE_PIPE_LEN;
 695         }
 696         ++__get_cpu_var(rcu_torture_batch)[completed];
 697         preempt_enable();
 698         cur_ops->readunlock(idx);
 699 }
 700
 701 /*
 702  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 703  * incrementing the corresponding element of the pipeline array.  The
 704  * counter in the element should never be greater than 1, otherwise, the
 705  * RCU implementation is broken.
 706  */
 707 static int
 708 rcu_torture_reader(void *arg)
 709 {
 710         int completed;
 711         int idx;
 712         DEFINE_RCU_RANDOM(rand);
 713         struct rcu_torture *p;
 714         int pipe_count;
 715         struct timer_list t;
 716
 717         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 718         set_user_nice(current, 19);
 719         if (irqreader && cur_ops->irqcapable)
 720                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
 721
 722         do {
 723                 if (irqreader && cur_ops->irqcapable) {
 724                         if (!timer_pending(&t))
 725                                 mod_timer(&t, 1);
 726                 }
 727                 idx = cur_ops->readlock();
 728                 completed = cur_ops->completed();
 729                 p = rcu_dereference(rcu_torture_current);
 730                 if (p == NULL) {
 731                         /* Wait for rcu_torture_writer to get underway */
 732                         cur_ops->readunlock(idx);
 733                         schedule_timeout_interruptible(HZ);
 734                         continue;
 735                 }
 736                 if (p->rtort_mbtest == 0)
 737                         atomic_inc(&n_rcu_torture_mberror);
 738                 cur_ops->readdelay(&rand);
 739                 preempt_disable();
 740                 pipe_count = p->rtort_pipe_count;
 741                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 742                         /* Should not happen, but... */
 743                         pipe_count = RCU_TORTURE_PIPE_LEN;
 744                 }
 745                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 746                 completed = cur_ops->completed() - completed;
 747                 if (completed > RCU_TORTURE_PIPE_LEN) {
 748                         /* Should not happen, but... */
 749                         completed = RCU_TORTURE_PIPE_LEN;
 750                 }
 751                 ++__get_cpu_var(rcu_torture_batch)[completed];
 752                 preempt_enable();
 753                 cur_ops->readunlock(idx);
 754                 schedule();
 755                 rcu_stutter_wait();
 756         } while (!kthread_should_stop() && !fullstop);
 757         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 758         if (irqreader && cur_ops->irqcapable)
 759                 del_timer_sync(&t);
 760         while (!kthread_should_stop() && fullstop != FULLSTOP_SHUTDOWN)
 761                 schedule_timeout_uninterruptible(1);
 762         return 0;
 763 }
 764
 765 /*
 766  * Create an RCU-torture statistics message in the specified buffer.
 767  */
 768 static int
 769 rcu_torture_printk(char *page)
 770 {
 771         int cnt = 0;
 772         int cpu;
 773         int i;
 774         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 775         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 776
 777         for_each_possible_cpu(cpu) {
 778                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 779                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 780                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 781                 }
 782         }
 783         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 784                 if (pipesummary[i] != 0)
 785                         break;
 786         }
 787         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 788         cnt += sprintf(&page[cnt],
 789                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 790                        "rtmbe: %d nt: %ld",
 791                        rcu_torture_current,
 792                        rcu_torture_current_version,
 793                        list_empty(&rcu_torture_freelist),
 794                        atomic_read(&n_rcu_torture_alloc),
 795                        atomic_read(&n_rcu_torture_alloc_fail),
 796                        atomic_read(&n_rcu_torture_free),
 797                        atomic_read(&n_rcu_torture_mberror),
 798                        n_rcu_torture_timers);
 799         if (atomic_read(&n_rcu_torture_mberror) != 0)
 800                 cnt += sprintf(&page[cnt], " !!!");
 801         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 802         if (i > 1) {
 803                 cnt += sprintf(&page[cnt], "!!! ");
 804                 atomic_inc(&n_rcu_torture_error);
 805                 WARN_ON_ONCE(1);
 806         }
 807         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 808         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 809                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 810         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 811         cnt += sprintf(&page[cnt], "Reader Batch: ");
 812         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 813                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 814         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 815         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 816         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 817                 cnt += sprintf(&page[cnt], " %d",
 818                                atomic_read(&rcu_torture_wcount[i]));
 819         }
 820         cnt += sprintf(&page[cnt], "\n");
 821         if (cur_ops->stats)
 822                 cnt += cur_ops->stats(&page[cnt]);
 823         return cnt;
 824 }
 825
 826 /*
 827  * Print torture statistics.  Caller must ensure that there is only
 828  * one call to this function at a given time!!!  This is normally
 829  * accomplished by relying on the module system to only have one copy
 830  * of the module loaded, and then by giving the rcu_torture_stats
 831  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 832  * thread is not running).
 833  */
 834 static void
 835 rcu_torture_stats_print(void)
 836 {
 837         int cnt;
 838
 839         cnt = rcu_torture_printk(printk_buf);
 840         printk(KERN_ALERT "%s", printk_buf);
 841 }
 842
 843 /*
 844  * Periodically prints torture statistics, if periodic statistics printing
 845  * was specified via the stat_interval module parameter.
 846  *
 847  * No need to worry about fullstop here, since this one doesn't reference
 848  * volatile state or register callbacks.
 849  */
 850 static int
 851 rcu_torture_stats(void *arg)
 852 {
 853         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 854         do {
 855                 schedule_timeout_interruptible(stat_interval * HZ);
 856                 rcu_torture_stats_print();
 857         } while (!kthread_should_stop() && !fullstop);
 858         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 859         return 0;
 860 }
 861
 862 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 863
 864 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 865  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 866  */
 867 static void rcu_torture_shuffle_tasks(void)
 868 {
 869         cpumask_var_t tmp_mask;
 870         int i;
 871
 872         if (!alloc_cpumask_var(&tmp_mask, GFP_KERNEL))
 873                 BUG();
 874
 875         cpumask_setall(tmp_mask);
 876         get_online_cpus();
 877
 878         /* No point in shuffling if there is only one online CPU (ex: UP) */
 879         if (num_online_cpus() == 1)
 880                 goto out;
 881
 882         if (rcu_idle_cpu != -1)
 883                 cpumask_clear_cpu(rcu_idle_cpu, tmp_mask);
 884
 885         set_cpus_allowed_ptr(current, tmp_mask);
 886
 887         if (reader_tasks) {
 888                 for (i = 0; i < nrealreaders; i++)
 889                         if (reader_tasks[i])
 890                                 set_cpus_allowed_ptr(reader_tasks[i],
 891                                                      tmp_mask);
 892         }
 893
 894         if (fakewriter_tasks) {
 895                 for (i = 0; i < nfakewriters; i++)
 896                         if (fakewriter_tasks[i])
 897                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
 898                                                      tmp_mask);
 899         }
 900
 901         if (writer_task)
 902                 set_cpus_allowed_ptr(writer_task, tmp_mask);
 903
 904         if (stats_task)
 905                 set_cpus_allowed_ptr(stats_task, tmp_mask);
 906
 907         if (rcu_idle_cpu == -1)
 908                 rcu_idle_cpu = num_online_cpus() - 1;
 909         else
 910                 rcu_idle_cpu--;
 911
 912 out:
 913         put_online_cpus();
 914         free_cpumask_var(tmp_mask);
 915 }
 916
 917 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 918  * system to become idle at a time and cut off its timer ticks. This is meant
 919  * to test the support for such tickless idle CPU in RCU.
 920  */
 921 static int
 922 rcu_torture_shuffle(void *arg)
 923 {
 924         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
 925         do {
 926                 schedule_timeout_interruptible(shuffle_interval * HZ);
 927                 rcu_torture_shuffle_tasks();
 928         } while (!kthread_should_stop() && !fullstop);
 929         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
 930         return 0;
 931 }
 932
 933 /* Cause the rcutorture test to "stutter", starting and stopping all
 934  * threads periodically.
 935  */
 936 static int
 937 rcu_torture_stutter(void *arg)
 938 {
 939         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
 940         do {
 941                 schedule_timeout_interruptible(stutter * HZ);
 942                 stutter_pause_test = 1;
 943                 if (!kthread_should_stop() && !fullstop)
 944                         schedule_timeout_interruptible(stutter * HZ);
 945                 stutter_pause_test = 0;
 946         } while (!kthread_should_stop() && !fullstop);
 947         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
 948         return 0;
 949 }
 950
 951 static inline void
 952 rcu_torture_print_module_parms(char *tag)
 953 {
 954         printk(KERN_ALERT "%s" TORTURE_FLAG
 955                 "--- %s: nreaders=%d nfakewriters=%d "
 956                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
 957                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
 958                 torture_type, tag, nrealreaders, nfakewriters,
 959                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 960                 stutter, irqreader);
 961 }
 962
 963 static struct notifier_block rcutorture_nb = {
 964         .notifier_call = rcutorture_shutdown_notify,
 965 };
 966
 967 static void
 968 rcu_torture_cleanup(void)
 969 {
 970         int i;
 971
 972         mutex_lock(&fullstop_mutex);
 973         if (!fullstop) {
 974                 /* If being signaled, let it happen, then exit. */
 975                 mutex_unlock(&fullstop_mutex);
 976                 schedule_timeout_interruptible(10 * HZ);
 977                 if (cur_ops->cb_barrier != NULL)
 978                         cur_ops->cb_barrier();
 979                 return;
 980         }
 981         fullstop = FULLSTOP_CLEANUP;
 982         mutex_unlock(&fullstop_mutex);
 983         unregister_reboot_notifier(&rcutorture_nb);
 984         if (stutter_task) {
 985                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
 986                 kthread_stop(stutter_task);
 987         }
 988         stutter_task = NULL;
 989         if (shuffler_task) {
 990                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
 991                 kthread_stop(shuffler_task);
 992         }
 993         shuffler_task = NULL;
 994
 995         if (writer_task) {
 996                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
 997                 kthread_stop(writer_task);
 998         }
 999         writer_task = NULL;
1000
1001         if (reader_tasks) {
1002                 for (i = 0; i < nrealreaders; i++) {
1003                         if (reader_tasks[i]) {
1004                                 VERBOSE_PRINTK_STRING(
1005                                         "Stopping rcu_torture_reader task");
1006                                 kthread_stop(reader_tasks[i]);
1007                         }
1008                         reader_tasks[i] = NULL;
1009                 }
1010                 kfree(reader_tasks);
1011                 reader_tasks = NULL;
1012         }
1013         rcu_torture_current = NULL;
1014
1015         if (fakewriter_tasks) {
1016                 for (i = 0; i < nfakewriters; i++) {
1017                         if (fakewriter_tasks[i]) {
1018                                 VERBOSE_PRINTK_STRING(
1019                                         "Stopping rcu_torture_fakewriter task");
1020                                 kthread_stop(fakewriter_tasks[i]);
1021                         }
1022                         fakewriter_tasks[i] = NULL;
1023                 }
1024                 kfree(fakewriter_tasks);
1025                 fakewriter_tasks = NULL;
1026         }
1027
1028         if (stats_task) {
1029                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1030                 kthread_stop(stats_task);
1031         }
1032         stats_task = NULL;
1033
1034         /* Wait for all RCU callbacks to fire.  */
1035
1036         if (cur_ops->cb_barrier != NULL)
1037                 cur_ops->cb_barrier();
1038
1039         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1040
1041         if (cur_ops->cleanup)
1042                 cur_ops->cleanup();
1043         if (atomic_read(&n_rcu_torture_error))
1044                 rcu_torture_print_module_parms("End of test: FAILURE");
1045         else
1046                 rcu_torture_print_module_parms("End of test: SUCCESS");
1047 }
1048
1049 static int __init
1050 rcu_torture_init(void)
1051 {
1052         int i;
1053         int cpu;
1054         int firsterr = 0;
1055         static struct rcu_torture_ops *torture_ops[] =
1056                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1057                   &srcu_ops, &sched_ops, &sched_ops_sync, };
1058
1059         mutex_lock(&fullstop_mutex);
1060
1061         /* Process args and tell the world that the torturer is on the job. */
1062         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1063                 cur_ops = torture_ops[i];
1064                 if (strcmp(torture_type, cur_ops->name) == 0)
1065                         break;
1066         }
1067         if (i == ARRAY_SIZE(torture_ops)) {
1068                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1069                        torture_type);
1070                 mutex_unlock(&fullstop_mutex);
1071                 return (-EINVAL);
1072         }
1073         if (cur_ops->init)
1074                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1075
1076         if (nreaders >= 0)
1077                 nrealreaders = nreaders;
1078         else
1079                 nrealreaders = 2 * num_online_cpus();
1080         rcu_torture_print_module_parms("Start of test");
1081         fullstop = 0;
1082
1083         /* Set up the freelist. */
1084
1085         INIT_LIST_HEAD(&rcu_torture_freelist);
1086         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1087                 rcu_tortures[i].rtort_mbtest = 0;
1088                 list_add_tail(&rcu_tortures[i].rtort_free,
1089                               &rcu_torture_freelist);
1090         }
1091
1092         /* Initialize the statistics so that each run gets its own numbers. */
1093
1094         rcu_torture_current = NULL;
1095         rcu_torture_current_version = 0;
1096         atomic_set(&n_rcu_torture_alloc, 0);
1097         atomic_set(&n_rcu_torture_alloc_fail, 0);
1098         atomic_set(&n_rcu_torture_free, 0);
1099         atomic_set(&n_rcu_torture_mberror, 0);
1100         atomic_set(&n_rcu_torture_error, 0);
1101         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1102                 atomic_set(&rcu_torture_wcount[i], 0);
1103         for_each_possible_cpu(cpu) {
1104                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1105                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1106                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1107                 }
1108         }
1109
1110         /* Start up the kthreads. */
1111
1112         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1113         writer_task = kthread_run(rcu_torture_writer, NULL,
1114                                   "rcu_torture_writer");
1115         if (IS_ERR(writer_task)) {
1116                 firsterr = PTR_ERR(writer_task);
1117                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1118                 writer_task = NULL;
1119                 goto unwind;
1120         }
1121         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1122                                    GFP_KERNEL);
1123         if (fakewriter_tasks == NULL) {
1124                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1125                 firsterr = -ENOMEM;
1126                 goto unwind;
1127         }
1128         for (i = 0; i < nfakewriters; i++) {
1129                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1130                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1131                                                   "rcu_torture_fakewriter");
1132                 if (IS_ERR(fakewriter_tasks[i])) {
1133                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1134                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1135                         fakewriter_tasks[i] = NULL;
1136                         goto unwind;
1137                 }
1138         }
1139         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1140                                GFP_KERNEL);
1141         if (reader_tasks == NULL) {
1142                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1143                 firsterr = -ENOMEM;
1144                 goto unwind;
1145         }
1146         for (i = 0; i < nrealreaders; i++) {
1147                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1148                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1149                                               "rcu_torture_reader");
1150                 if (IS_ERR(reader_tasks[i])) {
1151                         firsterr = PTR_ERR(reader_tasks[i]);
1152                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1153                         reader_tasks[i] = NULL;
1154                         goto unwind;
1155                 }
1156         }
1157         if (stat_interval > 0) {
1158                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1159                 stats_task = kthread_run(rcu_torture_stats, NULL,
1160                                         "rcu_torture_stats");
1161                 if (IS_ERR(stats_task)) {
1162                         firsterr = PTR_ERR(stats_task);
1163                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1164                         stats_task = NULL;
1165                         goto unwind;
1166                 }
1167         }
1168         if (test_no_idle_hz) {
1169                 rcu_idle_cpu = num_online_cpus() - 1;
1170                 /* Create the shuffler thread */
1171                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1172                                           "rcu_torture_shuffle");
1173                 if (IS_ERR(shuffler_task)) {
1174                         firsterr = PTR_ERR(shuffler_task);
1175                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1176                         shuffler_task = NULL;
1177                         goto unwind;
1178                 }
1179         }
1180         if (stutter < 0)
1181                 stutter = 0;
1182         if (stutter) {
1183                 /* Create the stutter thread */
1184                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1185                                           "rcu_torture_stutter");
1186                 if (IS_ERR(stutter_task)) {
1187                         firsterr = PTR_ERR(stutter_task);
1188                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1189                         stutter_task = NULL;
1190                         goto unwind;
1191                 }
1192         }
1193         register_reboot_notifier(&rcutorture_nb);
1194         mutex_unlock(&fullstop_mutex);
1195         return 0;
1196
1197 unwind:
1198         mutex_unlock(&fullstop_mutex);
1199         rcu_torture_cleanup();
1200         return firsterr;
1201 }
1202
1203 module_init(rcu_torture_init);
1204 module_exit(rcu_torture_cleanup);