SAFE public projects git trees. - safe/jmp/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;
 114 static long rcu_torture_current_version;
 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;
 128 static struct list_head rcu_torture_removed;
 129 static cpumask_var_t shuffle_tmp_mask;
 130
 131 static int stutter_pause_test;
 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
 271 static struct rcu_torture_ops *cur_ops;
 272
 273 /*
 274  * Definitions for rcu torture testing.
 275  */
 276
 277 static int rcu_torture_read_lock(void) __acquires(RCU)
 278 {
 279         rcu_read_lock();
 280         return 0;
 281 }
 282
 283 static void rcu_read_delay(struct rcu_random_state *rrsp)
 284 {
 285         const unsigned long shortdelay_us = 200;
 286         const unsigned long longdelay_ms = 50;
 287
 288         /* We want a short delay sometimes to make a reader delay the grace
 289          * period, and we want a long delay occasionally to trigger
 290          * force_quiescent_state. */
 291
 292         if (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
 293                 mdelay(longdelay_ms);
 294         if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
 295                 udelay(shortdelay_us);
 296 }
 297
 298 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 299 {
 300         rcu_read_unlock();
 301 }
 302
 303 static int rcu_torture_completed(void)
 304 {
 305         return rcu_batches_completed();
 306 }
 307
 308 static void
 309 rcu_torture_cb(struct rcu_head *p)
 310 {
 311         int i;
 312         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 313
 314         if (fullstop != FULLSTOP_DONTSTOP) {
 315                 /* Test is ending, just drop callbacks on the floor. */
 316                 /* The next initialization will pick up the pieces. */
 317                 return;
 318         }
 319         i = rp->rtort_pipe_count;
 320         if (i > RCU_TORTURE_PIPE_LEN)
 321                 i = RCU_TORTURE_PIPE_LEN;
 322         atomic_inc(&rcu_torture_wcount[i]);
 323         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 324                 rp->rtort_mbtest = 0;
 325                 rcu_torture_free(rp);
 326         } else
 327                 cur_ops->deferred_free(rp);
 328 }
 329
 330 static void rcu_torture_deferred_free(struct rcu_torture *p)
 331 {
 332         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 333 }
 334
 335 static struct rcu_torture_ops rcu_ops = {
 336         .init           = NULL,
 337         .cleanup        = NULL,
 338         .readlock       = rcu_torture_read_lock,
 339         .read_delay     = rcu_read_delay,
 340         .readunlock     = rcu_torture_read_unlock,
 341         .completed      = rcu_torture_completed,
 342         .deferred_free  = rcu_torture_deferred_free,
 343         .sync           = synchronize_rcu,
 344         .cb_barrier     = rcu_barrier,
 345         .stats          = NULL,
 346         .irq_capable    = 1,
 347         .name           = "rcu"
 348 };
 349
 350 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 351 {
 352         int i;
 353         struct rcu_torture *rp;
 354         struct rcu_torture *rp1;
 355
 356         cur_ops->sync();
 357         list_add(&p->rtort_free, &rcu_torture_removed);
 358         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 359                 i = rp->rtort_pipe_count;
 360                 if (i > RCU_TORTURE_PIPE_LEN)
 361                         i = RCU_TORTURE_PIPE_LEN;
 362                 atomic_inc(&rcu_torture_wcount[i]);
 363                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 364                         rp->rtort_mbtest = 0;
 365                         list_del(&rp->rtort_free);
 366                         rcu_torture_free(rp);
 367                 }
 368         }
 369 }
 370
 371 static void rcu_sync_torture_init(void)
 372 {
 373         INIT_LIST_HEAD(&rcu_torture_removed);
 374 }
 375
 376 static struct rcu_torture_ops rcu_sync_ops = {
 377         .init           = rcu_sync_torture_init,
 378         .cleanup        = NULL,
 379         .readlock       = rcu_torture_read_lock,
 380         .read_delay     = rcu_read_delay,
 381         .readunlock     = rcu_torture_read_unlock,
 382         .completed      = rcu_torture_completed,
 383         .deferred_free  = rcu_sync_torture_deferred_free,
 384         .sync           = synchronize_rcu,
 385         .cb_barrier     = NULL,
 386         .stats          = NULL,
 387         .irq_capable    = 1,
 388         .name           = "rcu_sync"
 389 };
 390
 391 /*
 392  * Definitions for rcu_bh torture testing.
 393  */
 394
 395 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 396 {
 397         rcu_read_lock_bh();
 398         return 0;
 399 }
 400
 401 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 402 {
 403         rcu_read_unlock_bh();
 404 }
 405
 406 static int rcu_bh_torture_completed(void)
 407 {
 408         return rcu_batches_completed_bh();
 409 }
 410
 411 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 412 {
 413         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 414 }
 415
 416 struct rcu_bh_torture_synchronize {
 417         struct rcu_head head;
 418         struct completion completion;
 419 };
 420
 421 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 422 {
 423         struct rcu_bh_torture_synchronize *rcu;
 424
 425         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 426         complete(&rcu->completion);
 427 }
 428
 429 static void rcu_bh_torture_synchronize(void)
 430 {
 431         struct rcu_bh_torture_synchronize rcu;
 432
 433         init_completion(&rcu.completion);
 434         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 435         wait_for_completion(&rcu.completion);
 436 }
 437
 438 static struct rcu_torture_ops rcu_bh_ops = {
 439         .init           = NULL,
 440         .cleanup        = NULL,
 441         .readlock       = rcu_bh_torture_read_lock,
 442         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 443         .readunlock     = rcu_bh_torture_read_unlock,
 444         .completed      = rcu_bh_torture_completed,
 445         .deferred_free  = rcu_bh_torture_deferred_free,
 446         .sync           = rcu_bh_torture_synchronize,
 447         .cb_barrier     = rcu_barrier_bh,
 448         .stats          = NULL,
 449         .irq_capable    = 1,
 450         .name           = "rcu_bh"
 451 };
 452
 453 static struct rcu_torture_ops rcu_bh_sync_ops = {
 454         .init           = rcu_sync_torture_init,
 455         .cleanup        = NULL,
 456         .readlock       = rcu_bh_torture_read_lock,
 457         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 458         .readunlock     = rcu_bh_torture_read_unlock,
 459         .completed      = rcu_bh_torture_completed,
 460         .deferred_free  = rcu_sync_torture_deferred_free,
 461         .sync           = rcu_bh_torture_synchronize,
 462         .cb_barrier     = NULL,
 463         .stats          = NULL,
 464         .irq_capable    = 1,
 465         .name           = "rcu_bh_sync"
 466 };
 467
 468 /*
 469  * Definitions for srcu torture testing.
 470  */
 471
 472 static struct srcu_struct srcu_ctl;
 473
 474 static void srcu_torture_init(void)
 475 {
 476         init_srcu_struct(&srcu_ctl);
 477         rcu_sync_torture_init();
 478 }
 479
 480 static void srcu_torture_cleanup(void)
 481 {
 482         synchronize_srcu(&srcu_ctl);
 483         cleanup_srcu_struct(&srcu_ctl);
 484 }
 485
 486 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 487 {
 488         return srcu_read_lock(&srcu_ctl);
 489 }
 490
 491 static void srcu_read_delay(struct rcu_random_state *rrsp)
 492 {
 493         long delay;
 494         const long uspertick = 1000000 / HZ;
 495         const long longdelay = 10;
 496
 497         /* We want there to be long-running readers, but not all the time. */
 498
 499         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 500         if (!delay)
 501                 schedule_timeout_interruptible(longdelay);
 502 }
 503
 504 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 505 {
 506         srcu_read_unlock(&srcu_ctl, idx);
 507 }
 508
 509 static int srcu_torture_completed(void)
 510 {
 511         return srcu_batches_completed(&srcu_ctl);
 512 }
 513
 514 static void srcu_torture_synchronize(void)
 515 {
 516         synchronize_srcu(&srcu_ctl);
 517 }
 518
 519 static int srcu_torture_stats(char *page)
 520 {
 521         int cnt = 0;
 522         int cpu;
 523         int idx = srcu_ctl.completed & 0x1;
 524
 525         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 526                        torture_type, TORTURE_FLAG, idx);
 527         for_each_possible_cpu(cpu) {
 528                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 529                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 530                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 531         }
 532         cnt += sprintf(&page[cnt], "\n");
 533         return cnt;
 534 }
 535
 536 static struct rcu_torture_ops srcu_ops = {
 537         .init           = srcu_torture_init,
 538         .cleanup        = srcu_torture_cleanup,
 539         .readlock       = srcu_torture_read_lock,
 540         .read_delay     = srcu_read_delay,
 541         .readunlock     = srcu_torture_read_unlock,
 542         .completed      = srcu_torture_completed,
 543         .deferred_free  = rcu_sync_torture_deferred_free,
 544         .sync           = srcu_torture_synchronize,
 545         .cb_barrier     = NULL,
 546         .stats          = srcu_torture_stats,
 547         .name           = "srcu"
 548 };
 549
 550 /*
 551  * Definitions for sched torture testing.
 552  */
 553
 554 static int sched_torture_read_lock(void)
 555 {
 556         preempt_disable();
 557         return 0;
 558 }
 559
 560 static void sched_torture_read_unlock(int idx)
 561 {
 562         preempt_enable();
 563 }
 564
 565 static int sched_torture_completed(void)
 566 {
 567         return 0;
 568 }
 569
 570 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 571 {
 572         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 573 }
 574
 575 static void sched_torture_synchronize(void)
 576 {
 577         synchronize_sched();
 578 }
 579
 580 static struct rcu_torture_ops sched_ops = {
 581         .init           = rcu_sync_torture_init,
 582         .cleanup        = NULL,
 583         .readlock       = sched_torture_read_lock,
 584         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 585         .readunlock     = sched_torture_read_unlock,
 586         .completed      = sched_torture_completed,
 587         .deferred_free  = rcu_sched_torture_deferred_free,
 588         .sync           = sched_torture_synchronize,
 589         .cb_barrier     = rcu_barrier_sched,
 590         .stats          = NULL,
 591         .irq_capable    = 1,
 592         .name           = "sched"
 593 };
 594
 595 static struct rcu_torture_ops sched_ops_sync = {
 596         .init           = rcu_sync_torture_init,
 597         .cleanup        = NULL,
 598         .readlock       = sched_torture_read_lock,
 599         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 600         .readunlock     = sched_torture_read_unlock,
 601         .completed      = sched_torture_completed,
 602         .deferred_free  = rcu_sync_torture_deferred_free,
 603         .sync           = sched_torture_synchronize,
 604         .cb_barrier     = NULL,
 605         .stats          = NULL,
 606         .name           = "sched_sync"
 607 };
 608
 609 static struct rcu_torture_ops sched_expedited_ops = {
 610         .init           = rcu_sync_torture_init,
 611         .cleanup        = NULL,
 612         .readlock       = sched_torture_read_lock,
 613         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 614         .readunlock     = sched_torture_read_unlock,
 615         .completed      = sched_torture_completed,
 616         .deferred_free  = rcu_sync_torture_deferred_free,
 617         .sync           = synchronize_sched_expedited,
 618         .cb_barrier     = NULL,
 619         .stats          = rcu_expedited_torture_stats,
 620         .irq_capable    = 1,
 621         .name           = "sched_expedited"
 622 };
 623
 624 /*
 625  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 626  * for that pointed to by rcu_torture_current, freeing the old structure
 627  * after a series of grace periods (the "pipeline").
 628  */
 629 static int
 630 rcu_torture_writer(void *arg)
 631 {
 632         int i;
 633         long oldbatch = rcu_batches_completed();
 634         struct rcu_torture *rp;
 635         struct rcu_torture *old_rp;
 636         static DEFINE_RCU_RANDOM(rand);
 637
 638         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 639         set_user_nice(current, 19);
 640
 641         do {
 642                 schedule_timeout_uninterruptible(1);
 643                 rp = rcu_torture_alloc();
 644                 if (rp == NULL)
 645                         continue;
 646                 rp->rtort_pipe_count = 0;
 647                 udelay(rcu_random(&rand) & 0x3ff);
 648                 old_rp = rcu_torture_current;
 649                 rp->rtort_mbtest = 1;
 650                 rcu_assign_pointer(rcu_torture_current, rp);
 651                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
 652                 if (old_rp) {
 653                         i = old_rp->rtort_pipe_count;
 654                         if (i > RCU_TORTURE_PIPE_LEN)
 655                                 i = RCU_TORTURE_PIPE_LEN;
 656                         atomic_inc(&rcu_torture_wcount[i]);
 657                         old_rp->rtort_pipe_count++;
 658                         cur_ops->deferred_free(old_rp);
 659                 }
 660                 rcu_torture_current_version++;
 661                 oldbatch = cur_ops->completed();
 662                 rcu_stutter_wait("rcu_torture_writer");
 663         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 664         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 665         rcutorture_shutdown_absorb("rcu_torture_writer");
 666         while (!kthread_should_stop())
 667                 schedule_timeout_uninterruptible(1);
 668         return 0;
 669 }
 670
 671 /*
 672  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 673  * delay between calls.
 674  */
 675 static int
 676 rcu_torture_fakewriter(void *arg)
 677 {
 678         DEFINE_RCU_RANDOM(rand);
 679
 680         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 681         set_user_nice(current, 19);
 682
 683         do {
 684                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 685                 udelay(rcu_random(&rand) & 0x3ff);
 686                 cur_ops->sync();
 687                 rcu_stutter_wait("rcu_torture_fakewriter");
 688         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 689
 690         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 691         rcutorture_shutdown_absorb("rcu_torture_fakewriter");
 692         while (!kthread_should_stop())
 693                 schedule_timeout_uninterruptible(1);
 694         return 0;
 695 }
 696
 697 /*
 698  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 699  * incrementing the corresponding element of the pipeline array.  The
 700  * counter in the element should never be greater than 1, otherwise, the
 701  * RCU implementation is broken.
 702  */
 703 static void rcu_torture_timer(unsigned long unused)
 704 {
 705         int idx;
 706         int completed;
 707         static DEFINE_RCU_RANDOM(rand);
 708         static DEFINE_SPINLOCK(rand_lock);
 709         struct rcu_torture *p;
 710         int pipe_count;
 711
 712         idx = cur_ops->readlock();
 713         completed = cur_ops->completed();
 714         p = rcu_dereference(rcu_torture_current);
 715         if (p == NULL) {
 716                 /* Leave because rcu_torture_writer is not yet underway */
 717                 cur_ops->readunlock(idx);
 718                 return;
 719         }
 720         if (p->rtort_mbtest == 0)
 721                 atomic_inc(&n_rcu_torture_mberror);
 722         spin_lock(&rand_lock);
 723         cur_ops->read_delay(&rand);
 724         n_rcu_torture_timers++;
 725         spin_unlock(&rand_lock);
 726         preempt_disable();
 727         pipe_count = p->rtort_pipe_count;
 728         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 729                 /* Should not happen, but... */
 730                 pipe_count = RCU_TORTURE_PIPE_LEN;
 731         }
 732         ++__get_cpu_var(rcu_torture_count)[pipe_count];
 733         completed = cur_ops->completed() - completed;
 734         if (completed > RCU_TORTURE_PIPE_LEN) {
 735                 /* Should not happen, but... */
 736                 completed = RCU_TORTURE_PIPE_LEN;
 737         }
 738         ++__get_cpu_var(rcu_torture_batch)[completed];
 739         preempt_enable();
 740         cur_ops->readunlock(idx);
 741 }
 742
 743 /*
 744  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 745  * incrementing the corresponding element of the pipeline array.  The
 746  * counter in the element should never be greater than 1, otherwise, the
 747  * RCU implementation is broken.
 748  */
 749 static int
 750 rcu_torture_reader(void *arg)
 751 {
 752         int completed;
 753         int idx;
 754         DEFINE_RCU_RANDOM(rand);
 755         struct rcu_torture *p;
 756         int pipe_count;
 757         struct timer_list t;
 758
 759         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 760         set_user_nice(current, 19);
 761         if (irqreader && cur_ops->irq_capable)
 762                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
 763
 764         do {
 765                 if (irqreader && cur_ops->irq_capable) {
 766                         if (!timer_pending(&t))
 767                                 mod_timer(&t, 1);
 768                 }
 769                 idx = cur_ops->readlock();
 770                 completed = cur_ops->completed();
 771                 p = rcu_dereference(rcu_torture_current);
 772                 if (p == NULL) {
 773                         /* Wait for rcu_torture_writer to get underway */
 774                         cur_ops->readunlock(idx);
 775                         schedule_timeout_interruptible(HZ);
 776                         continue;
 777                 }
 778                 if (p->rtort_mbtest == 0)
 779                         atomic_inc(&n_rcu_torture_mberror);
 780                 cur_ops->read_delay(&rand);
 781                 preempt_disable();
 782                 pipe_count = p->rtort_pipe_count;
 783                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 784                         /* Should not happen, but... */
 785                         pipe_count = RCU_TORTURE_PIPE_LEN;
 786                 }
 787                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 788                 completed = cur_ops->completed() - completed;
 789                 if (completed > RCU_TORTURE_PIPE_LEN) {
 790                         /* Should not happen, but... */
 791                         completed = RCU_TORTURE_PIPE_LEN;
 792                 }
 793                 ++__get_cpu_var(rcu_torture_batch)[completed];
 794                 preempt_enable();
 795                 cur_ops->readunlock(idx);
 796                 schedule();
 797                 rcu_stutter_wait("rcu_torture_reader");
 798         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 799         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 800         rcutorture_shutdown_absorb("rcu_torture_reader");
 801         if (irqreader && cur_ops->irq_capable)
 802                 del_timer_sync(&t);
 803         while (!kthread_should_stop())
 804                 schedule_timeout_uninterruptible(1);
 805         return 0;
 806 }
 807
 808 /*
 809  * Create an RCU-torture statistics message in the specified buffer.
 810  */
 811 static int
 812 rcu_torture_printk(char *page)
 813 {
 814         int cnt = 0;
 815         int cpu;
 816         int i;
 817         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 818         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 819
 820         for_each_possible_cpu(cpu) {
 821                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 822                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 823                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 824                 }
 825         }
 826         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 827                 if (pipesummary[i] != 0)
 828                         break;
 829         }
 830         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 831         cnt += sprintf(&page[cnt],
 832                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 833                        "rtmbe: %d nt: %ld",
 834                        rcu_torture_current,
 835                        rcu_torture_current_version,
 836                        list_empty(&rcu_torture_freelist),
 837                        atomic_read(&n_rcu_torture_alloc),
 838                        atomic_read(&n_rcu_torture_alloc_fail),
 839                        atomic_read(&n_rcu_torture_free),
 840                        atomic_read(&n_rcu_torture_mberror),
 841                        n_rcu_torture_timers);
 842         if (atomic_read(&n_rcu_torture_mberror) != 0)
 843                 cnt += sprintf(&page[cnt], " !!!");
 844         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 845         if (i > 1) {
 846                 cnt += sprintf(&page[cnt], "!!! ");
 847                 atomic_inc(&n_rcu_torture_error);
 848                 WARN_ON_ONCE(1);
 849         }
 850         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 851         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 852                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 853         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 854         cnt += sprintf(&page[cnt], "Reader Batch: ");
 855         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 856                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 857         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 858         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 859         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 860                 cnt += sprintf(&page[cnt], " %d",
 861                                atomic_read(&rcu_torture_wcount[i]));
 862         }
 863         cnt += sprintf(&page[cnt], "\n");
 864         if (cur_ops->stats)
 865                 cnt += cur_ops->stats(&page[cnt]);
 866         return cnt;
 867 }
 868
 869 /*
 870  * Print torture statistics.  Caller must ensure that there is only
 871  * one call to this function at a given time!!!  This is normally
 872  * accomplished by relying on the module system to only have one copy
 873  * of the module loaded, and then by giving the rcu_torture_stats
 874  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 875  * thread is not running).
 876  */
 877 static void
 878 rcu_torture_stats_print(void)
 879 {
 880         int cnt;
 881
 882         cnt = rcu_torture_printk(printk_buf);
 883         printk(KERN_ALERT "%s", printk_buf);
 884 }
 885
 886 /*
 887  * Periodically prints torture statistics, if periodic statistics printing
 888  * was specified via the stat_interval module parameter.
 889  *
 890  * No need to worry about fullstop here, since this one doesn't reference
 891  * volatile state or register callbacks.
 892  */
 893 static int
 894 rcu_torture_stats(void *arg)
 895 {
 896         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 897         do {
 898                 schedule_timeout_interruptible(stat_interval * HZ);
 899                 rcu_torture_stats_print();
 900                 rcutorture_shutdown_absorb("rcu_torture_stats");
 901         } while (!kthread_should_stop());
 902         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 903         return 0;
 904 }
 905
 906 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 907
 908 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 909  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 910  */
 911 static void rcu_torture_shuffle_tasks(void)
 912 {
 913         int i;
 914
 915         cpumask_setall(shuffle_tmp_mask);
 916         get_online_cpus();
 917
 918         /* No point in shuffling if there is only one online CPU (ex: UP) */
 919         if (num_online_cpus() == 1) {
 920                 put_online_cpus();
 921                 return;
 922         }
 923
 924         if (rcu_idle_cpu != -1)
 925                 cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
 926
 927         set_cpus_allowed_ptr(current, shuffle_tmp_mask);
 928
 929         if (reader_tasks) {
 930                 for (i = 0; i < nrealreaders; i++)
 931                         if (reader_tasks[i])
 932                                 set_cpus_allowed_ptr(reader_tasks[i],
 933                                                      shuffle_tmp_mask);
 934         }
 935
 936         if (fakewriter_tasks) {
 937                 for (i = 0; i < nfakewriters; i++)
 938                         if (fakewriter_tasks[i])
 939                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
 940                                                      shuffle_tmp_mask);
 941         }
 942
 943         if (writer_task)
 944                 set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
 945
 946         if (stats_task)
 947                 set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
 948
 949         if (rcu_idle_cpu == -1)
 950                 rcu_idle_cpu = num_online_cpus() - 1;
 951         else
 952                 rcu_idle_cpu--;
 953
 954         put_online_cpus();
 955 }
 956
 957 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 958  * system to become idle at a time and cut off its timer ticks. This is meant
 959  * to test the support for such tickless idle CPU in RCU.
 960  */
 961 static int
 962 rcu_torture_shuffle(void *arg)
 963 {
 964         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
 965         do {
 966                 schedule_timeout_interruptible(shuffle_interval * HZ);
 967                 rcu_torture_shuffle_tasks();
 968                 rcutorture_shutdown_absorb("rcu_torture_shuffle");
 969         } while (!kthread_should_stop());
 970         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
 971         return 0;
 972 }
 973
 974 /* Cause the rcutorture test to "stutter", starting and stopping all
 975  * threads periodically.
 976  */
 977 static int
 978 rcu_torture_stutter(void *arg)
 979 {
 980         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
 981         do {
 982                 schedule_timeout_interruptible(stutter * HZ);
 983                 stutter_pause_test = 1;
 984                 if (!kthread_should_stop())
 985                         schedule_timeout_interruptible(stutter * HZ);
 986                 stutter_pause_test = 0;
 987                 rcutorture_shutdown_absorb("rcu_torture_stutter");
 988         } while (!kthread_should_stop());
 989         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
 990         return 0;
 991 }
 992
 993 static inline void
 994 rcu_torture_print_module_parms(char *tag)
 995 {
 996         printk(KERN_ALERT "%s" TORTURE_FLAG
 997                 "--- %s: nreaders=%d nfakewriters=%d "
 998                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
 999                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
1000                 torture_type, tag, nrealreaders, nfakewriters,
1001                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1002                 stutter, irqreader);
1003 }
1004
1005 static struct notifier_block rcutorture_nb = {
1006         .notifier_call = rcutorture_shutdown_notify,
1007 };
1008
1009 static void
1010 rcu_torture_cleanup(void)
1011 {
1012         int i;
1013
1014         mutex_lock(&fullstop_mutex);
1015         if (fullstop == FULLSTOP_SHUTDOWN) {
1016                 printk(KERN_WARNING /* but going down anyway, so... */
1017                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
1018                 mutex_unlock(&fullstop_mutex);
1019                 schedule_timeout_uninterruptible(10);
1020                 if (cur_ops->cb_barrier != NULL)
1021                         cur_ops->cb_barrier();
1022                 return;
1023         }
1024         fullstop = FULLSTOP_RMMOD;
1025         mutex_unlock(&fullstop_mutex);
1026         unregister_reboot_notifier(&rcutorture_nb);
1027         if (stutter_task) {
1028                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
1029                 kthread_stop(stutter_task);
1030         }
1031         stutter_task = NULL;
1032         if (shuffler_task) {
1033                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
1034                 kthread_stop(shuffler_task);
1035                 free_cpumask_var(shuffle_tmp_mask);
1036         }
1037         shuffler_task = NULL;
1038
1039         if (writer_task) {
1040                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1041                 kthread_stop(writer_task);
1042         }
1043         writer_task = NULL;
1044
1045         if (reader_tasks) {
1046                 for (i = 0; i < nrealreaders; i++) {
1047                         if (reader_tasks[i]) {
1048                                 VERBOSE_PRINTK_STRING(
1049                                         "Stopping rcu_torture_reader task");
1050                                 kthread_stop(reader_tasks[i]);
1051                         }
1052                         reader_tasks[i] = NULL;
1053                 }
1054                 kfree(reader_tasks);
1055                 reader_tasks = NULL;
1056         }
1057         rcu_torture_current = NULL;
1058
1059         if (fakewriter_tasks) {
1060                 for (i = 0; i < nfakewriters; i++) {
1061                         if (fakewriter_tasks[i]) {
1062                                 VERBOSE_PRINTK_STRING(
1063                                         "Stopping rcu_torture_fakewriter task");
1064                                 kthread_stop(fakewriter_tasks[i]);
1065                         }
1066                         fakewriter_tasks[i] = NULL;
1067                 }
1068                 kfree(fakewriter_tasks);
1069                 fakewriter_tasks = NULL;
1070         }
1071
1072         if (stats_task) {
1073                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1074                 kthread_stop(stats_task);
1075         }
1076         stats_task = NULL;
1077
1078         /* Wait for all RCU callbacks to fire.  */
1079
1080         if (cur_ops->cb_barrier != NULL)
1081                 cur_ops->cb_barrier();
1082
1083         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1084
1085         if (cur_ops->cleanup)
1086                 cur_ops->cleanup();
1087         if (atomic_read(&n_rcu_torture_error))
1088                 rcu_torture_print_module_parms("End of test: FAILURE");
1089         else
1090                 rcu_torture_print_module_parms("End of test: SUCCESS");
1091 }
1092
1093 static int __init
1094 rcu_torture_init(void)
1095 {
1096         int i;
1097         int cpu;
1098         int firsterr = 0;
1099         static struct rcu_torture_ops *torture_ops[] =
1100                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1101                   &sched_expedited_ops,
1102                   &srcu_ops, &sched_ops, &sched_ops_sync, };
1103
1104         mutex_lock(&fullstop_mutex);
1105
1106         /* Process args and tell the world that the torturer is on the job. */
1107         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1108                 cur_ops = torture_ops[i];
1109                 if (strcmp(torture_type, cur_ops->name) == 0)
1110                         break;
1111         }
1112         if (i == ARRAY_SIZE(torture_ops)) {
1113                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1114                        torture_type);
1115                 mutex_unlock(&fullstop_mutex);
1116                 return -EINVAL;
1117         }
1118         if (cur_ops->init)
1119                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1120
1121         if (nreaders >= 0)
1122                 nrealreaders = nreaders;
1123         else
1124                 nrealreaders = 2 * num_online_cpus();
1125         rcu_torture_print_module_parms("Start of test");
1126         fullstop = FULLSTOP_DONTSTOP;
1127
1128         /* Set up the freelist. */
1129
1130         INIT_LIST_HEAD(&rcu_torture_freelist);
1131         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1132                 rcu_tortures[i].rtort_mbtest = 0;
1133                 list_add_tail(&rcu_tortures[i].rtort_free,
1134                               &rcu_torture_freelist);
1135         }
1136
1137         /* Initialize the statistics so that each run gets its own numbers. */
1138
1139         rcu_torture_current = NULL;
1140         rcu_torture_current_version = 0;
1141         atomic_set(&n_rcu_torture_alloc, 0);
1142         atomic_set(&n_rcu_torture_alloc_fail, 0);
1143         atomic_set(&n_rcu_torture_free, 0);
1144         atomic_set(&n_rcu_torture_mberror, 0);
1145         atomic_set(&n_rcu_torture_error, 0);
1146         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1147                 atomic_set(&rcu_torture_wcount[i], 0);
1148         for_each_possible_cpu(cpu) {
1149                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1150                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1151                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1152                 }
1153         }
1154
1155         /* Start up the kthreads. */
1156
1157         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1158         writer_task = kthread_run(rcu_torture_writer, NULL,
1159                                   "rcu_torture_writer");
1160         if (IS_ERR(writer_task)) {
1161                 firsterr = PTR_ERR(writer_task);
1162                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1163                 writer_task = NULL;
1164                 goto unwind;
1165         }
1166         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1167                                    GFP_KERNEL);
1168         if (fakewriter_tasks == NULL) {
1169                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1170                 firsterr = -ENOMEM;
1171                 goto unwind;
1172         }
1173         for (i = 0; i < nfakewriters; i++) {
1174                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1175                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1176                                                   "rcu_torture_fakewriter");
1177                 if (IS_ERR(fakewriter_tasks[i])) {
1178                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1179                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1180                         fakewriter_tasks[i] = NULL;
1181                         goto unwind;
1182                 }
1183         }
1184         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1185                                GFP_KERNEL);
1186         if (reader_tasks == NULL) {
1187                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1188                 firsterr = -ENOMEM;
1189                 goto unwind;
1190         }
1191         for (i = 0; i < nrealreaders; i++) {
1192                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1193                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1194                                               "rcu_torture_reader");
1195                 if (IS_ERR(reader_tasks[i])) {
1196                         firsterr = PTR_ERR(reader_tasks[i]);
1197                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1198                         reader_tasks[i] = NULL;
1199                         goto unwind;
1200                 }
1201         }
1202         if (stat_interval > 0) {
1203                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1204                 stats_task = kthread_run(rcu_torture_stats, NULL,
1205                                         "rcu_torture_stats");
1206                 if (IS_ERR(stats_task)) {
1207                         firsterr = PTR_ERR(stats_task);
1208                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1209                         stats_task = NULL;
1210                         goto unwind;
1211                 }
1212         }
1213         if (test_no_idle_hz) {
1214                 rcu_idle_cpu = num_online_cpus() - 1;
1215
1216                 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1217                         firsterr = -ENOMEM;
1218                         VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1219                         goto unwind;
1220                 }
1221
1222                 /* Create the shuffler thread */
1223                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1224                                           "rcu_torture_shuffle");
1225                 if (IS_ERR(shuffler_task)) {
1226                         free_cpumask_var(shuffle_tmp_mask);
1227                         firsterr = PTR_ERR(shuffler_task);
1228                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1229                         shuffler_task = NULL;
1230                         goto unwind;
1231                 }
1232         }
1233         if (stutter < 0)
1234                 stutter = 0;
1235         if (stutter) {
1236                 /* Create the stutter thread */
1237                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1238                                           "rcu_torture_stutter");
1239                 if (IS_ERR(stutter_task)) {
1240                         firsterr = PTR_ERR(stutter_task);
1241                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1242                         stutter_task = NULL;
1243                         goto unwind;
1244                 }
1245         }
1246         register_reboot_notifier(&rcutorture_nb);
1247         mutex_unlock(&fullstop_mutex);
1248         return 0;
1249
1250 unwind:
1251         mutex_unlock(&fullstop_mutex);
1252         rcu_torture_cleanup();
1253         return firsterr;
1254 }
1255
1256 module_init(rcu_torture_init);
1257 module_exit(rcu_torture_cleanup);