kernel/rcutorture.c

   1 /*
   2  * Read-Copy Update module-based torture test facility
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2005, 2006
  19  *
  20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  21  *          Josh Triplett <josh@freedesktop.org>
  22  *
  23  * See also:  Documentation/RCU/torture.txt
  24  */
  25 #include <linux/types.h>
  26 #include <linux/kernel.h>
  27 #include <linux/init.h>
  28 #include <linux/module.h>
  29 #include <linux/kthread.h>
  30 #include <linux/err.h>
  31 #include <linux/spinlock.h>
  32 #include <linux/smp.h>
  33 #include <linux/rcupdate.h>
  34 #include <linux/interrupt.h>
  35 #include <linux/sched.h>
  36 #include <asm/atomic.h>
  37 #include <linux/bitops.h>
  38 #include <linux/completion.h>
  39 #include <linux/moduleparam.h>
  40 #include <linux/percpu.h>
  41 #include <linux/notifier.h>
  42 #include <linux/reboot.h>
  43 #include <linux/freezer.h>
  44 #include <linux/cpu.h>
  45 #include <linux/delay.h>
  46 #include <linux/stat.h>
  47 #include <linux/srcu.h>
  48 #include <linux/slab.h>
  49 #include <asm/byteorder.h>
  50
  51 MODULE_LICENSE("GPL");
  52 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
  53               "Josh Triplett <josh@freedesktop.org>");
  54
  55 static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
  56 static int nfakewriters = 4;    /* # fake writer threads */
  57 static int stat_interval;       /* Interval between stats, in seconds. */
  58                                 /*  Defaults to "only at end of test". */
  59 static int verbose;             /* Print more debug info. */
  60 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
  61 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
  62 static int stutter = 5;         /* Start/stop testing interval (in sec) */
  63 static int irqreader = 1;       /* RCU readers from irq (timers). */
  64 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
  65
  66 module_param(nreaders, int, 0444);
  67 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  68 module_param(nfakewriters, int, 0444);
  69 MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
  70 module_param(stat_interval, int, 0444);
  71 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  72 module_param(verbose, bool, 0444);
  73 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  74 module_param(test_no_idle_hz, bool, 0444);
  75 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  76 module_param(shuffle_interval, int, 0444);
  77 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  78 module_param(stutter, int, 0444);
  79 MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
  80 module_param(irqreader, int, 0444);
  81 MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
  82 module_param(torture_type, charp, 0444);
  83 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
  84
  85 #define TORTURE_FLAG "-torture:"
  86 #define PRINTK_STRING(s) \
  87         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  88 #define VERBOSE_PRINTK_STRING(s) \
  89         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  90 #define VERBOSE_PRINTK_ERRSTRING(s) \
  91         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
  92
  93 static char printk_buf[4096];
  94
  95 static int nrealreaders;
  96 static struct task_struct *writer_task;
  97 static struct task_struct **fakewriter_tasks;
  98 static struct task_struct **reader_tasks;
  99 static struct task_struct *stats_task;
 100 static struct task_struct *shuffler_task;
 101 static struct task_struct *stutter_task;
 102
 103 #define RCU_TORTURE_PIPE_LEN 10
 104
 105 struct rcu_torture {
 106         struct rcu_head rtort_rcu;
 107         int rtort_pipe_count;
 108         struct list_head rtort_free;
 109         int rtort_mbtest;
 110 };
 111
 112 static LIST_HEAD(rcu_torture_freelist);
 113 static struct rcu_torture *rcu_torture_current = NULL;
 114 static long rcu_torture_current_version = 0;
 115 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 116 static DEFINE_SPINLOCK(rcu_torture_lock);
 117 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
 118         { 0 };
 119 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
 120         { 0 };
 121 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 122 static atomic_t n_rcu_torture_alloc;
 123 static atomic_t n_rcu_torture_alloc_fail;
 124 static atomic_t n_rcu_torture_free;
 125 static atomic_t n_rcu_torture_mberror;
 126 static atomic_t n_rcu_torture_error;
 127 static long n_rcu_torture_timers = 0;
 128 static struct list_head rcu_torture_removed;
 129 static cpumask_var_t shuffle_tmp_mask;
 130
 131 static int stutter_pause_test = 0;
 132
 133 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 134 #define RCUTORTURE_RUNNABLE_INIT 1
 135 #else
 136 #define RCUTORTURE_RUNNABLE_INIT 0
 137 #endif
 138 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 139
 140 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
 141
 142 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
 143 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with rcutorture running. */
 144 #define FULLSTOP_RMMOD    2     /* Normal rmmod of rcutorture. */
 145 static int fullstop = FULLSTOP_RMMOD;
 146 DEFINE_MUTEX(fullstop_mutex);   /* Protect fullstop transitions and spawning */
 147                                 /*  of kthreads. */
 148
 149 /*
 150  * Detect and respond to a system shutdown.
 151  */
 152 static int
 153 rcutorture_shutdown_notify(struct notifier_block *unused1,
 154                            unsigned long unused2, void *unused3)
 155 {
 156         mutex_lock(&fullstop_mutex);
 157         if (fullstop == FULLSTOP_DONTSTOP)
 158                 fullstop = FULLSTOP_SHUTDOWN;
 159         else
 160                 printk(KERN_WARNING /* but going down anyway, so... */
 161                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 162         mutex_unlock(&fullstop_mutex);
 163         return NOTIFY_DONE;
 164 }
 165
 166 /*
 167  * Absorb kthreads into a kernel function that won't return, so that
 168  * they won't ever access module text or data again.
 169  */
 170 static void rcutorture_shutdown_absorb(char *title)
 171 {
 172         if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 173                 printk(KERN_NOTICE
 174                        "rcutorture thread %s parking due to system shutdown\n",
 175                        title);
 176                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 177         }
 178 }
 179
 180 /*
 181  * Allocate an element from the rcu_tortures pool.
 182  */
 183 static struct rcu_torture *
 184 rcu_torture_alloc(void)
 185 {
 186         struct list_head *p;
 187
 188         spin_lock_bh(&rcu_torture_lock);
 189         if (list_empty(&rcu_torture_freelist)) {
 190                 atomic_inc(&n_rcu_torture_alloc_fail);
 191                 spin_unlock_bh(&rcu_torture_lock);
 192                 return NULL;
 193         }
 194         atomic_inc(&n_rcu_torture_alloc);
 195         p = rcu_torture_freelist.next;
 196         list_del_init(p);
 197         spin_unlock_bh(&rcu_torture_lock);
 198         return container_of(p, struct rcu_torture, rtort_free);
 199 }
 200
 201 /*
 202  * Free an element to the rcu_tortures pool.
 203  */
 204 static void
 205 rcu_torture_free(struct rcu_torture *p)
 206 {
 207         atomic_inc(&n_rcu_torture_free);
 208         spin_lock_bh(&rcu_torture_lock);
 209         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 210         spin_unlock_bh(&rcu_torture_lock);
 211 }
 212
 213 struct rcu_random_state {
 214         unsigned long rrs_state;
 215         long rrs_count;
 216 };
 217
 218 #define RCU_RANDOM_MULT 39916801  /* prime */
 219 #define RCU_RANDOM_ADD  479001701 /* prime */
 220 #define RCU_RANDOM_REFRESH 10000
 221
 222 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 223
 224 /*
 225  * Crude but fast random-number generator.  Uses a linear congruential
 226  * generator, with occasional help from cpu_clock().
 227  */
 228 static unsigned long
 229 rcu_random(struct rcu_random_state *rrsp)
 230 {
 231         if (--rrsp->rrs_count < 0) {
 232                 rrsp->rrs_state +=
 233                         (unsigned long)cpu_clock(raw_smp_processor_id());
 234                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 235         }
 236         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 237         return swahw32(rrsp->rrs_state);
 238 }
 239
 240 static void
 241 rcu_stutter_wait(char *title)
 242 {
 243         while (stutter_pause_test || !rcutorture_runnable) {
 244                 if (rcutorture_runnable)
 245                         schedule_timeout_interruptible(1);
 246                 else
 247                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 248                 rcutorture_shutdown_absorb(title);
 249         }
 250 }
 251
 252 /*
 253  * Operations vector for selecting different types of tests.
 254  */
 255
 256 struct rcu_torture_ops {
 257         void (*init)(void);
 258         void (*cleanup)(void);
 259         int (*readlock)(void);
 260         void (*read_delay)(struct rcu_random_state *rrsp);
 261         void (*readunlock)(int idx);
 262         int (*completed)(void);
 263         void (*deferred_free)(struct rcu_torture *p);
 264         void (*sync)(void);
 265         void (*cb_barrier)(void);
 266         int (*stats)(char *page);
 267         int irq_capable;
 268         char *name;
 269 };
 270 static struct rcu_torture_ops *cur_ops = NULL;
 271
 272 /*
 273  * Definitions for rcu torture testing.
 274  */
 275
 276 static int rcu_torture_read_lock(void) __acquires(RCU)
 277 {
 278         rcu_read_lock();
 279         return 0;
 280 }
 281
 282 static void rcu_read_delay(struct rcu_random_state *rrsp)
 283 {
 284         long delay;
 285         const long longdelay = 200;
 286
 287         /* We want there to be long-running readers, but not all the time. */
 288
 289         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
 290         if (!delay)
 291                 udelay(longdelay);
 292 }
 293
 294 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 295 {
 296         rcu_read_unlock();
 297 }
 298
 299 static int rcu_torture_completed(void)
 300 {
 301         return rcu_batches_completed();
 302 }
 303
 304 static void
 305 rcu_torture_cb(struct rcu_head *p)
 306 {
 307         int i;
 308         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 309
 310         if (fullstop != FULLSTOP_DONTSTOP) {
 311                 /* Test is ending, just drop callbacks on the floor. */
 312                 /* The next initialization will pick up the pieces. */
 313                 return;
 314         }
 315         i = rp->rtort_pipe_count;
 316         if (i > RCU_TORTURE_PIPE_LEN)
 317                 i = RCU_TORTURE_PIPE_LEN;
 318         atomic_inc(&rcu_torture_wcount[i]);
 319         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 320                 rp->rtort_mbtest = 0;
 321                 rcu_torture_free(rp);
 322         } else
 323                 cur_ops->deferred_free(rp);
 324 }
 325
 326 static void rcu_torture_deferred_free(struct rcu_torture *p)
 327 {
 328         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 329 }
 330
 331 static struct rcu_torture_ops rcu_ops = {
 332         .init           = NULL,
 333         .cleanup        = NULL,
 334         .readlock       = rcu_torture_read_lock,
 335         .read_delay     = rcu_read_delay,
 336         .readunlock     = rcu_torture_read_unlock,
 337         .completed      = rcu_torture_completed,
 338         .deferred_free  = rcu_torture_deferred_free,
 339         .sync           = synchronize_rcu,
 340         .cb_barrier     = rcu_barrier,
 341         .stats          = NULL,
 342         .irq_capable    = 1,
 343         .name           = "rcu"
 344 };
 345
 346 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 347 {
 348         int i;
 349         struct rcu_torture *rp;
 350         struct rcu_torture *rp1;
 351
 352         cur_ops->sync();
 353         list_add(&p->rtort_free, &rcu_torture_removed);
 354         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 355                 i = rp->rtort_pipe_count;
 356                 if (i > RCU_TORTURE_PIPE_LEN)
 357                         i = RCU_TORTURE_PIPE_LEN;
 358                 atomic_inc(&rcu_torture_wcount[i]);
 359                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 360                         rp->rtort_mbtest = 0;
 361                         list_del(&rp->rtort_free);
 362                         rcu_torture_free(rp);
 363                 }
 364         }
 365 }
 366
 367 static void rcu_sync_torture_init(void)
 368 {
 369         INIT_LIST_HEAD(&rcu_torture_removed);
 370 }
 371
 372 static struct rcu_torture_ops rcu_sync_ops = {
 373         .init           = rcu_sync_torture_init,
 374         .cleanup        = NULL,
 375         .readlock       = rcu_torture_read_lock,
 376         .read_delay     = rcu_read_delay,
 377         .readunlock     = rcu_torture_read_unlock,
 378         .completed      = rcu_torture_completed,
 379         .deferred_free  = rcu_sync_torture_deferred_free,
 380         .sync           = synchronize_rcu,
 381         .cb_barrier     = NULL,
 382         .stats          = NULL,
 383         .irq_capable    = 1,
 384         .name           = "rcu_sync"
 385 };
 386
 387 /*
 388  * Definitions for rcu_bh torture testing.
 389  */
 390
 391 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 392 {
 393         rcu_read_lock_bh();
 394         return 0;
 395 }
 396
 397 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 398 {
 399         rcu_read_unlock_bh();
 400 }
 401
 402 static int rcu_bh_torture_completed(void)
 403 {
 404         return rcu_batches_completed_bh();
 405 }
 406
 407 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 408 {
 409         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 410 }
 411
 412 struct rcu_bh_torture_synchronize {
 413         struct rcu_head head;
 414         struct completion completion;
 415 };
 416
 417 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 418 {
 419         struct rcu_bh_torture_synchronize *rcu;
 420
 421         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 422         complete(&rcu->completion);
 423 }
 424
 425 static void rcu_bh_torture_synchronize(void)
 426 {
 427         struct rcu_bh_torture_synchronize rcu;
 428
 429         init_completion(&rcu.completion);
 430         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 431         wait_for_completion(&rcu.completion);
 432 }
 433
 434 static struct rcu_torture_ops rcu_bh_ops = {
 435         .init           = NULL,
 436         .cleanup        = NULL,
 437         .readlock       = rcu_bh_torture_read_lock,
 438         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 439         .readunlock     = rcu_bh_torture_read_unlock,
 440         .completed      = rcu_bh_torture_completed,
 441         .deferred_free  = rcu_bh_torture_deferred_free,
 442         .sync           = rcu_bh_torture_synchronize,
 443         .cb_barrier     = rcu_barrier_bh,
 444         .stats          = NULL,
 445         .irq_capable    = 1,
 446         .name           = "rcu_bh"
 447 };
 448
 449 static struct rcu_torture_ops rcu_bh_sync_ops = {
 450         .init           = rcu_sync_torture_init,
 451         .cleanup        = NULL,
 452         .readlock       = rcu_bh_torture_read_lock,
 453         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 454         .readunlock     = rcu_bh_torture_read_unlock,
 455         .completed      = rcu_bh_torture_completed,
 456         .deferred_free  = rcu_sync_torture_deferred_free,
 457         .sync           = rcu_bh_torture_synchronize,
 458         .cb_barrier     = NULL,
 459         .stats          = NULL,
 460         .irq_capable    = 1,
 461         .name           = "rcu_bh_sync"
 462 };
 463
 464 /*
 465  * Definitions for srcu torture testing.
 466  */
 467
 468 static struct srcu_struct srcu_ctl;
 469
 470 static void srcu_torture_init(void)
 471 {
 472         init_srcu_struct(&srcu_ctl);
 473         rcu_sync_torture_init();
 474 }
 475
 476 static void srcu_torture_cleanup(void)
 477 {
 478         synchronize_srcu(&srcu_ctl);
 479         cleanup_srcu_struct(&srcu_ctl);
 480 }
 481
 482 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 483 {
 484         return srcu_read_lock(&srcu_ctl);
 485 }
 486
 487 static void srcu_read_delay(struct rcu_random_state *rrsp)
 488 {
 489         long delay;
 490         const long uspertick = 1000000 / HZ;
 491         const long longdelay = 10;
 492
 493         /* We want there to be long-running readers, but not all the time. */
 494
 495         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 496         if (!delay)
 497                 schedule_timeout_interruptible(longdelay);
 498 }
 499
 500 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 501 {
 502         srcu_read_unlock(&srcu_ctl, idx);
 503 }
 504
 505 static int srcu_torture_completed(void)
 506 {
 507         return srcu_batches_completed(&srcu_ctl);
 508 }
 509
 510 static void srcu_torture_synchronize(void)
 511 {
 512         synchronize_srcu(&srcu_ctl);
 513 }
 514
 515 static int srcu_torture_stats(char *page)
 516 {
 517         int cnt = 0;
 518         int cpu;
 519         int idx = srcu_ctl.completed & 0x1;
 520
 521         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 522                        torture_type, TORTURE_FLAG, idx);
 523         for_each_possible_cpu(cpu) {
 524                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 525                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 526                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 527         }
 528         cnt += sprintf(&page[cnt], "\n");
 529         return cnt;
 530 }
 531
 532 static struct rcu_torture_ops srcu_ops = {
 533         .init           = srcu_torture_init,
 534         .cleanup        = srcu_torture_cleanup,
 535         .readlock       = srcu_torture_read_lock,
 536         .read_delay     = srcu_read_delay,
 537         .readunlock     = srcu_torture_read_unlock,
 538         .completed      = srcu_torture_completed,
 539         .deferred_free  = rcu_sync_torture_deferred_free,
 540         .sync           = srcu_torture_synchronize,
 541         .cb_barrier     = NULL,
 542         .stats          = srcu_torture_stats,
 543         .name           = "srcu"
 544 };
 545
 546 /*
 547  * Definitions for sched torture testing.
 548  */
 549
 550 static int sched_torture_read_lock(void)
 551 {
 552         preempt_disable();
 553         return 0;
 554 }
 555
 556 static void sched_torture_read_unlock(int idx)
 557 {
 558         preempt_enable();
 559 }
 560
 561 static int sched_torture_completed(void)
 562 {
 563         return 0;
 564 }
 565
 566 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 567 {
 568         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 569 }
 570
 571 static void sched_torture_synchronize(void)
 572 {
 573         synchronize_sched();
 574 }
 575
 576 static struct rcu_torture_ops sched_ops = {
 577         .init           = rcu_sync_torture_init,
 578         .cleanup        = NULL,
 579         .readlock       = sched_torture_read_lock,
 580         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 581         .readunlock     = sched_torture_read_unlock,
 582         .completed      = sched_torture_completed,
 583         .deferred_free  = rcu_sched_torture_deferred_free,
 584         .sync           = sched_torture_synchronize,
 585         .cb_barrier     = rcu_barrier_sched,
 586         .stats          = NULL,
 587         .irq_capable    = 1,
 588         .name           = "sched"
 589 };
 590
 591 static struct rcu_torture_ops sched_ops_sync = {
 592         .init           = rcu_sync_torture_init,
 593         .cleanup        = NULL,
 594         .readlock       = sched_torture_read_lock,
 595         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 596         .readunlock     = sched_torture_read_unlock,
 597         .completed      = sched_torture_completed,
 598         .deferred_free  = rcu_sync_torture_deferred_free,
 599         .sync           = sched_torture_synchronize,
 600         .cb_barrier     = NULL,
 601         .stats          = NULL,
 602         .name           = "sched_sync"
 603 };
 604
 605 extern int rcu_expedited_torture_stats(char *page);
 606
 607 static struct rcu_torture_ops sched_expedited_ops = {
 608         .init           = rcu_sync_torture_init,
 609         .cleanup        = NULL,
 610         .readlock       = sched_torture_read_lock,
 611         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 612         .readunlock     = sched_torture_read_unlock,
 613         .completed      = sched_torture_completed,
 614         .deferred_free  = rcu_sync_torture_deferred_free,
 615         .sync           = synchronize_sched_expedited,
 616         .cb_barrier     = NULL,
 617         .stats          = rcu_expedited_torture_stats,
 618         .irq_capable    = 1,
 619         .name           = "sched_expedited"
 620 };
 621
 622 /*
 623  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 624  * for that pointed to by rcu_torture_current, freeing the old structure
 625  * after a series of grace periods (the "pipeline").
 626  */
 627 static int
 628 rcu_torture_writer(void *arg)
 629 {
 630         int i;
 631         long oldbatch = rcu_batches_completed();
 632         struct rcu_torture *rp;
 633         struct rcu_torture *old_rp;
 634         static DEFINE_RCU_RANDOM(rand);
 635
 636         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 637         set_user_nice(current, 19);
 638
 639         do {
 640                 schedule_timeout_uninterruptible(1);
 641                 if ((rp = rcu_torture_alloc()) == NULL)
 642                         continue;
 643                 rp->rtort_pipe_count = 0;
 644                 udelay(rcu_random(&rand) & 0x3ff);
 645                 old_rp = rcu_torture_current;
 646                 rp->rtort_mbtest = 1;
 647                 rcu_assign_pointer(rcu_torture_current, rp);
 648                 smp_wmb();
 649                 if (old_rp) {
 650                         i = old_rp->rtort_pipe_count;
 651                         if (i > RCU_TORTURE_PIPE_LEN)
 652                                 i = RCU_TORTURE_PIPE_LEN;
 653                         atomic_inc(&rcu_torture_wcount[i]);
 654                         old_rp->rtort_pipe_count++;
 655                         cur_ops->deferred_free(old_rp);
 656                 }
 657                 rcu_torture_current_version++;
 658                 oldbatch = cur_ops->completed();
 659                 rcu_stutter_wait("rcu_torture_writer");
 660         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 661         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 662         rcutorture_shutdown_absorb("rcu_torture_writer");
 663         while (!kthread_should_stop())
 664                 schedule_timeout_uninterruptible(1);
 665         return 0;
 666 }
 667
 668 /*
 669  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 670  * delay between calls.
 671  */
 672 static int
 673 rcu_torture_fakewriter(void *arg)
 674 {
 675         DEFINE_RCU_RANDOM(rand);
 676
 677         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 678         set_user_nice(current, 19);
 679
 680         do {
 681                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 682                 udelay(rcu_random(&rand) & 0x3ff);
 683                 cur_ops->sync();
 684                 rcu_stutter_wait("rcu_torture_fakewriter");
 685         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 686
 687         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 688         rcutorture_shutdown_absorb("rcu_torture_fakewriter");
 689         while (!kthread_should_stop())
 690                 schedule_timeout_uninterruptible(1);
 691         return 0;
 692 }
 693
 694 /*
 695  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 696  * incrementing the corresponding element of the pipeline array.  The
 697  * counter in the element should never be greater than 1, otherwise, the
 698  * RCU implementation is broken.
 699  */
 700 static void rcu_torture_timer(unsigned long unused)
 701 {
 702         int idx;
 703         int completed;
 704         static DEFINE_RCU_RANDOM(rand);
 705         static DEFINE_SPINLOCK(rand_lock);
 706         struct rcu_torture *p;
 707         int pipe_count;
 708
 709         idx = cur_ops->readlock();
 710         completed = cur_ops->completed();
 711         p = rcu_dereference(rcu_torture_current);
 712         if (p == NULL) {
 713                 /* Leave because rcu_torture_writer is not yet underway */
 714                 cur_ops->readunlock(idx);
 715                 return;
 716         }
 717         if (p->rtort_mbtest == 0)
 718                 atomic_inc(&n_rcu_torture_mberror);
 719         spin_lock(&rand_lock);
 720         cur_ops->read_delay(&rand);
 721         n_rcu_torture_timers++;
 722         spin_unlock(&rand_lock);
 723         preempt_disable();
 724         pipe_count = p->rtort_pipe_count;
 725         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 726                 /* Should not happen, but... */
 727                 pipe_count = RCU_TORTURE_PIPE_LEN;
 728         }
 729         ++__get_cpu_var(rcu_torture_count)[pipe_count];
 730         completed = cur_ops->completed() - completed;
 731         if (completed > RCU_TORTURE_PIPE_LEN) {
 732                 /* Should not happen, but... */
 733                 completed = RCU_TORTURE_PIPE_LEN;
 734         }
 735         ++__get_cpu_var(rcu_torture_batch)[completed];
 736         preempt_enable();
 737         cur_ops->readunlock(idx);
 738 }
 739
 740 /*
 741  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 742  * incrementing the corresponding element of the pipeline array.  The
 743  * counter in the element should never be greater than 1, otherwise, the
 744  * RCU implementation is broken.
 745  */
 746 static int
 747 rcu_torture_reader(void *arg)
 748 {
 749         int completed;
 750         int idx;
 751         DEFINE_RCU_RANDOM(rand);
 752         struct rcu_torture *p;
 753         int pipe_count;
 754         struct timer_list t;
 755
 756         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 757         set_user_nice(current, 19);
 758         if (irqreader && cur_ops->irq_capable)
 759                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
 760
 761         do {
 762                 if (irqreader && cur_ops->irq_capable) {
 763                         if (!timer_pending(&t))
 764                                 mod_timer(&t, 1);
 765                 }
 766                 idx = cur_ops->readlock();
 767                 completed = cur_ops->completed();
 768                 p = rcu_dereference(rcu_torture_current);
 769                 if (p == NULL) {
 770                         /* Wait for rcu_torture_writer to get underway */
 771                         cur_ops->readunlock(idx);
 772                         schedule_timeout_interruptible(HZ);
 773                         continue;
 774                 }
 775                 if (p->rtort_mbtest == 0)
 776                         atomic_inc(&n_rcu_torture_mberror);
 777                 cur_ops->read_delay(&rand);
 778                 preempt_disable();
 779                 pipe_count = p->rtort_pipe_count;
 780                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 781                         /* Should not happen, but... */
 782                         pipe_count = RCU_TORTURE_PIPE_LEN;
 783                 }
 784                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 785                 completed = cur_ops->completed() - completed;
 786                 if (completed > RCU_TORTURE_PIPE_LEN) {
 787                         /* Should not happen, but... */
 788                         completed = RCU_TORTURE_PIPE_LEN;
 789                 }
 790                 ++__get_cpu_var(rcu_torture_batch)[completed];
 791                 preempt_enable();
 792                 cur_ops->readunlock(idx);
 793                 schedule();
 794                 rcu_stutter_wait("rcu_torture_reader");
 795         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 796         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 797         rcutorture_shutdown_absorb("rcu_torture_reader");
 798         if (irqreader && cur_ops->irq_capable)
 799                 del_timer_sync(&t);
 800         while (!kthread_should_stop())
 801                 schedule_timeout_uninterruptible(1);
 802         return 0;
 803 }
 804
 805 /*
 806  * Create an RCU-torture statistics message in the specified buffer.
 807  */
 808 static int
 809 rcu_torture_printk(char *page)
 810 {
 811         int cnt = 0;
 812         int cpu;
 813         int i;
 814         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 815         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 816
 817         for_each_possible_cpu(cpu) {
 818                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 819                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 820                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 821                 }
 822         }
 823         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 824                 if (pipesummary[i] != 0)
 825                         break;
 826         }
 827         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 828         cnt += sprintf(&page[cnt],
 829                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 830                        "rtmbe: %d nt: %ld",
 831                        rcu_torture_current,
 832                        rcu_torture_current_version,
 833                        list_empty(&rcu_torture_freelist),
 834                        atomic_read(&n_rcu_torture_alloc),
 835                        atomic_read(&n_rcu_torture_alloc_fail),
 836                        atomic_read(&n_rcu_torture_free),
 837                        atomic_read(&n_rcu_torture_mberror),
 838                        n_rcu_torture_timers);
 839         if (atomic_read(&n_rcu_torture_mberror) != 0)
 840                 cnt += sprintf(&page[cnt], " !!!");
 841         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 842         if (i > 1) {
 843                 cnt += sprintf(&page[cnt], "!!! ");
 844                 atomic_inc(&n_rcu_torture_error);
 845                 WARN_ON_ONCE(1);
 846         }
 847         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 848         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 849                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 850         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 851         cnt += sprintf(&page[cnt], "Reader Batch: ");
 852         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 853                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 854         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 855         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 856         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 857                 cnt += sprintf(&page[cnt], " %d",
 858                                atomic_read(&rcu_torture_wcount[i]));
 859         }
 860         cnt += sprintf(&page[cnt], "\n");
 861         if (cur_ops->stats)
 862                 cnt += cur_ops->stats(&page[cnt]);
 863         return cnt;
 864 }
 865
 866 /*
 867  * Print torture statistics.  Caller must ensure that there is only
 868  * one call to this function at a given time!!!  This is normally
 869  * accomplished by relying on the module system to only have one copy
 870  * of the module loaded, and then by giving the rcu_torture_stats
 871  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 872  * thread is not running).
 873  */
 874 static void
 875 rcu_torture_stats_print(void)
 876 {
 877         int cnt;
 878
 879         cnt = rcu_torture_printk(printk_buf);
 880         printk(KERN_ALERT "%s", printk_buf);
 881 }
 882
 883 /*
 884  * Periodically prints torture statistics, if periodic statistics printing
 885  * was specified via the stat_interval module parameter.
 886  *
 887  * No need to worry about fullstop here, since this one doesn't reference
 888  * volatile state or register callbacks.
 889  */
 890 static int
 891 rcu_torture_stats(void *arg)
 892 {
 893         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 894         do {
 895                 schedule_timeout_interruptible(stat_interval * HZ);
 896                 rcu_torture_stats_print();
 897                 rcutorture_shutdown_absorb("rcu_torture_stats");
 898         } while (!kthread_should_stop());
 899         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 900         return 0;
 901 }
 902
 903 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 904
 905 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 906  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 907  */
 908 static void rcu_torture_shuffle_tasks(void)
 909 {
 910         int i;
 911
 912         cpumask_setall(shuffle_tmp_mask);
 913         get_online_cpus();
 914
 915         /* No point in shuffling if there is only one online CPU (ex: UP) */
 916         if (num_online_cpus() == 1) {
 917                 put_online_cpus();
 918                 return;
 919         }
 920
 921         if (rcu_idle_cpu != -1)
 922                 cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
 923
 924         set_cpus_allowed_ptr(current, shuffle_tmp_mask);
 925
 926         if (reader_tasks) {
 927                 for (i = 0; i < nrealreaders; i++)
 928                         if (reader_tasks[i])
 929                                 set_cpus_allowed_ptr(reader_tasks[i],
 930                                                      shuffle_tmp_mask);
 931         }
 932
 933         if (fakewriter_tasks) {
 934                 for (i = 0; i < nfakewriters; i++)
 935                         if (fakewriter_tasks[i])
 936                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
 937                                                      shuffle_tmp_mask);
 938         }
 939
 940         if (writer_task)
 941                 set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
 942
 943         if (stats_task)
 944                 set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
 945
 946         if (rcu_idle_cpu == -1)
 947                 rcu_idle_cpu = num_online_cpus() - 1;
 948         else
 949                 rcu_idle_cpu--;
 950
 951         put_online_cpus();
 952 }
 953
 954 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 955  * system to become idle at a time and cut off its timer ticks. This is meant
 956  * to test the support for such tickless idle CPU in RCU.
 957  */
 958 static int
 959 rcu_torture_shuffle(void *arg)
 960 {
 961         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
 962         do {
 963                 schedule_timeout_interruptible(shuffle_interval * HZ);
 964                 rcu_torture_shuffle_tasks();
 965                 rcutorture_shutdown_absorb("rcu_torture_shuffle");
 966         } while (!kthread_should_stop());
 967         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
 968         return 0;
 969 }
 970
 971 /* Cause the rcutorture test to "stutter", starting and stopping all
 972  * threads periodically.
 973  */
 974 static int
 975 rcu_torture_stutter(void *arg)
 976 {
 977         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
 978         do {
 979                 schedule_timeout_interruptible(stutter * HZ);
 980                 stutter_pause_test = 1;
 981                 if (!kthread_should_stop())
 982                         schedule_timeout_interruptible(stutter * HZ);
 983                 stutter_pause_test = 0;
 984                 rcutorture_shutdown_absorb("rcu_torture_stutter");
 985         } while (!kthread_should_stop());
 986         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
 987         return 0;
 988 }
 989
 990 static inline void
 991 rcu_torture_print_module_parms(char *tag)
 992 {
 993         printk(KERN_ALERT "%s" TORTURE_FLAG
 994                 "--- %s: nreaders=%d nfakewriters=%d "
 995                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
 996                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
 997                 torture_type, tag, nrealreaders, nfakewriters,
 998                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 999                 stutter, irqreader);
1000 }
1001
1002 static struct notifier_block rcutorture_nb = {
1003         .notifier_call = rcutorture_shutdown_notify,
1004 };
1005
1006 static void
1007 rcu_torture_cleanup(void)
1008 {
1009         int i;
1010
1011         mutex_lock(&fullstop_mutex);
1012         if (fullstop == FULLSTOP_SHUTDOWN) {
1013                 printk(KERN_WARNING /* but going down anyway, so... */
1014                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
1015                 mutex_unlock(&fullstop_mutex);
1016                 schedule_timeout_uninterruptible(10);
1017                 if (cur_ops->cb_barrier != NULL)
1018                         cur_ops->cb_barrier();
1019                 return;
1020         }
1021         fullstop = FULLSTOP_RMMOD;
1022         mutex_unlock(&fullstop_mutex);
1023         unregister_reboot_notifier(&rcutorture_nb);
1024         if (stutter_task) {
1025                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
1026                 kthread_stop(stutter_task);
1027         }
1028         stutter_task = NULL;
1029         if (shuffler_task) {
1030                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
1031                 kthread_stop(shuffler_task);
1032                 free_cpumask_var(shuffle_tmp_mask);
1033         }
1034         shuffler_task = NULL;
1035
1036         if (writer_task) {
1037                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1038                 kthread_stop(writer_task);
1039         }
1040         writer_task = NULL;
1041
1042         if (reader_tasks) {
1043                 for (i = 0; i < nrealreaders; i++) {
1044                         if (reader_tasks[i]) {
1045                                 VERBOSE_PRINTK_STRING(
1046                                         "Stopping rcu_torture_reader task");
1047                                 kthread_stop(reader_tasks[i]);
1048                         }
1049                         reader_tasks[i] = NULL;
1050                 }
1051                 kfree(reader_tasks);
1052                 reader_tasks = NULL;
1053         }
1054         rcu_torture_current = NULL;
1055
1056         if (fakewriter_tasks) {
1057                 for (i = 0; i < nfakewriters; i++) {
1058                         if (fakewriter_tasks[i]) {
1059                                 VERBOSE_PRINTK_STRING(
1060                                         "Stopping rcu_torture_fakewriter task");
1061                                 kthread_stop(fakewriter_tasks[i]);
1062                         }
1063                         fakewriter_tasks[i] = NULL;
1064                 }
1065                 kfree(fakewriter_tasks);
1066                 fakewriter_tasks = NULL;
1067         }
1068
1069         if (stats_task) {
1070                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1071                 kthread_stop(stats_task);
1072         }
1073         stats_task = NULL;
1074
1075         /* Wait for all RCU callbacks to fire.  */
1076
1077         if (cur_ops->cb_barrier != NULL)
1078                 cur_ops->cb_barrier();
1079
1080         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1081
1082         if (cur_ops->cleanup)
1083                 cur_ops->cleanup();
1084         if (atomic_read(&n_rcu_torture_error))
1085                 rcu_torture_print_module_parms("End of test: FAILURE");
1086         else
1087                 rcu_torture_print_module_parms("End of test: SUCCESS");
1088 }
1089
1090 static int __init
1091 rcu_torture_init(void)
1092 {
1093         int i;
1094         int cpu;
1095         int firsterr = 0;
1096         static struct rcu_torture_ops *torture_ops[] =
1097                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1098                   &sched_expedited_ops,
1099                   &srcu_ops, &sched_ops, &sched_ops_sync, };
1100
1101         mutex_lock(&fullstop_mutex);
1102
1103         /* Process args and tell the world that the torturer is on the job. */
1104         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1105                 cur_ops = torture_ops[i];
1106                 if (strcmp(torture_type, cur_ops->name) == 0)
1107                         break;
1108         }
1109         if (i == ARRAY_SIZE(torture_ops)) {
1110                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1111                        torture_type);
1112                 mutex_unlock(&fullstop_mutex);
1113                 return (-EINVAL);
1114         }
1115         if (cur_ops->init)
1116                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1117
1118         if (nreaders >= 0)
1119                 nrealreaders = nreaders;
1120         else
1121                 nrealreaders = 2 * num_online_cpus();
1122         rcu_torture_print_module_parms("Start of test");
1123         fullstop = FULLSTOP_DONTSTOP;
1124
1125         /* Set up the freelist. */
1126
1127         INIT_LIST_HEAD(&rcu_torture_freelist);
1128         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1129                 rcu_tortures[i].rtort_mbtest = 0;
1130                 list_add_tail(&rcu_tortures[i].rtort_free,
1131                               &rcu_torture_freelist);
1132         }
1133
1134         /* Initialize the statistics so that each run gets its own numbers. */
1135
1136         rcu_torture_current = NULL;
1137         rcu_torture_current_version = 0;
1138         atomic_set(&n_rcu_torture_alloc, 0);
1139         atomic_set(&n_rcu_torture_alloc_fail, 0);
1140         atomic_set(&n_rcu_torture_free, 0);
1141         atomic_set(&n_rcu_torture_mberror, 0);
1142         atomic_set(&n_rcu_torture_error, 0);
1143         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1144                 atomic_set(&rcu_torture_wcount[i], 0);
1145         for_each_possible_cpu(cpu) {
1146                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1147                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1148                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1149                 }
1150         }
1151
1152         /* Start up the kthreads. */
1153
1154         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1155         writer_task = kthread_run(rcu_torture_writer, NULL,
1156                                   "rcu_torture_writer");
1157         if (IS_ERR(writer_task)) {
1158                 firsterr = PTR_ERR(writer_task);
1159                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1160                 writer_task = NULL;
1161                 goto unwind;
1162         }
1163         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1164                                    GFP_KERNEL);
1165         if (fakewriter_tasks == NULL) {
1166                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1167                 firsterr = -ENOMEM;
1168                 goto unwind;
1169         }
1170         for (i = 0; i < nfakewriters; i++) {
1171                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1172                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1173                                                   "rcu_torture_fakewriter");
1174                 if (IS_ERR(fakewriter_tasks[i])) {
1175                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1176                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1177                         fakewriter_tasks[i] = NULL;
1178                         goto unwind;
1179                 }
1180         }
1181         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1182                                GFP_KERNEL);
1183         if (reader_tasks == NULL) {
1184                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1185                 firsterr = -ENOMEM;
1186                 goto unwind;
1187         }
1188         for (i = 0; i < nrealreaders; i++) {
1189                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1190                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1191                                               "rcu_torture_reader");
1192                 if (IS_ERR(reader_tasks[i])) {
1193                         firsterr = PTR_ERR(reader_tasks[i]);
1194                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1195                         reader_tasks[i] = NULL;
1196                         goto unwind;
1197                 }
1198         }
1199         if (stat_interval > 0) {
1200                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1201                 stats_task = kthread_run(rcu_torture_stats, NULL,
1202                                         "rcu_torture_stats");
1203                 if (IS_ERR(stats_task)) {
1204                         firsterr = PTR_ERR(stats_task);
1205                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1206                         stats_task = NULL;
1207                         goto unwind;
1208                 }
1209         }
1210         if (test_no_idle_hz) {
1211                 rcu_idle_cpu = num_online_cpus() - 1;
1212
1213                 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1214                         firsterr = -ENOMEM;
1215                         VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1216                         goto unwind;
1217                 }
1218
1219                 /* Create the shuffler thread */
1220                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1221                                           "rcu_torture_shuffle");
1222                 if (IS_ERR(shuffler_task)) {
1223                         free_cpumask_var(shuffle_tmp_mask);
1224                         firsterr = PTR_ERR(shuffler_task);
1225                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1226                         shuffler_task = NULL;
1227                         goto unwind;
1228                 }
1229         }
1230         if (stutter < 0)
1231                 stutter = 0;
1232         if (stutter) {
1233                 /* Create the stutter thread */
1234                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1235                                           "rcu_torture_stutter");
1236                 if (IS_ERR(stutter_task)) {
1237                         firsterr = PTR_ERR(stutter_task);
1238                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1239                         stutter_task = NULL;
1240                         goto unwind;
1241                 }
1242         }
1243         register_reboot_notifier(&rcutorture_nb);
1244         mutex_unlock(&fullstop_mutex);
1245         return 0;
1246
1247 unwind:
1248         mutex_unlock(&fullstop_mutex);
1249         rcu_torture_cleanup();
1250         return firsterr;
1251 }
1252
1253 module_init(rcu_torture_init);
1254 module_exit(rcu_torture_cleanup);