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