linux/kernel/rcutorture.c
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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
  51MODULE_LICENSE("GPL");
  52MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
  53              "Josh Triplett <josh@freedesktop.org>");
  54
  55static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
  56static int nfakewriters = 4;    /* # fake writer threads */
  57static int stat_interval;       /* Interval between stats, in seconds. */
  58                                /*  Defaults to "only at end of test". */
  59static int verbose;             /* Print more debug info. */
  60static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
  61static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
  62static int stutter = 5;         /* Start/stop testing interval (in sec) */
  63static int irqreader = 1;       /* RCU readers from irq (timers). */
  64static char *torture_type = "rcu"; /* What RCU implementation to torture. */
  65
  66module_param(nreaders, int, 0444);
  67MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  68module_param(nfakewriters, int, 0444);
  69MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
  70module_param(stat_interval, int, 0444);
  71MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  72module_param(verbose, bool, 0444);
  73MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  74module_param(test_no_idle_hz, bool, 0444);
  75MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  76module_param(shuffle_interval, int, 0444);
  77MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  78module_param(stutter, int, 0444);
  79MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
  80module_param(irqreader, int, 0444);
  81MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
  82module_param(torture_type, charp, 0444);
  83MODULE_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
  93static char printk_buf[4096];
  94
  95static int nrealreaders;
  96static struct task_struct *writer_task;
  97static struct task_struct **fakewriter_tasks;
  98static struct task_struct **reader_tasks;
  99static struct task_struct *stats_task;
 100static struct task_struct *shuffler_task;
 101static struct task_struct *stutter_task;
 102
 103#define RCU_TORTURE_PIPE_LEN 10
 104
 105struct 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
 112static LIST_HEAD(rcu_torture_freelist);
 113static struct rcu_torture *rcu_torture_current = NULL;
 114static long rcu_torture_current_version = 0;
 115static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 116static DEFINE_SPINLOCK(rcu_torture_lock);
 117static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
 118        { 0 };
 119static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
 120        { 0 };
 121static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 122static atomic_t n_rcu_torture_alloc;
 123static atomic_t n_rcu_torture_alloc_fail;
 124static atomic_t n_rcu_torture_free;
 125static atomic_t n_rcu_torture_mberror;
 126static atomic_t n_rcu_torture_error;
 127static long n_rcu_torture_timers = 0;
 128static struct list_head rcu_torture_removed;
 129static cpumask_var_t shuffle_tmp_mask;
 130
 131static int stutter_pause_test = 0;
 132
 133#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 134#define RCUTORTURE_RUNNABLE_INIT 1
 135#else
 136#define RCUTORTURE_RUNNABLE_INIT 0
 137#endif
 138int 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. */
 145static int fullstop = FULLSTOP_RMMOD;
 146DEFINE_MUTEX(fullstop_mutex);   /* Protect fullstop transitions and spawning */
 147                                /*  of kthreads. */
 148
 149/*
 150 * Detect and respond to a system shutdown.
 151 */
 152static int
 153rcutorture_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 */
 170static 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 */
 183static struct rcu_torture *
 184rcu_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 */
 204static void
 205rcu_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
 213struct 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 */
 228static unsigned long
 229rcu_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
 240static void
 241rcu_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
 256struct rcu_torture_ops {
 257        void (*init)(void);
 258        void (*cleanup)(void);
 259        int (*readlock)(void);
 260        void (*readdelay)(struct rcu_random_state *rrsp);
 261        void (*readunlock)(int idx);
 262        int (*completed)(void);
 263        void (*deferredfree)(struct rcu_torture *p);
 264        void (*sync)(void);
 265        void (*cb_barrier)(void);
 266        int (*stats)(char *page);
 267        int irqcapable;
 268        char *name;
 269};
 270static struct rcu_torture_ops *cur_ops = NULL;
 271
 272/*
 273 * Definitions for rcu torture testing.
 274 */
 275
 276static int rcu_torture_read_lock(void) __acquires(RCU)
 277{
 278        rcu_read_lock();
 279        return 0;
 280}
 281
 282static void rcu_read_delay(struct rcu_random_state *rrsp)
 283{
 284        long delay;
 285        const long longdelay = 200;
 286
 287        /* We want there to be long-running readers, but not all the time. */
 288
 289        delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
 290        if (!delay)
 291                udelay(longdelay);
 292}
 293
 294static void rcu_torture_read_unlock(int idx) __releases(RCU)
 295{
 296        rcu_read_unlock();
 297}
 298
 299static int rcu_torture_completed(void)
 300{
 301        return rcu_batches_completed();
 302}
 303
 304static void
 305rcu_torture_cb(struct rcu_head *p)
 306{
 307        int i;
 308        struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 309
 310        if (fullstop != FULLSTOP_DONTSTOP) {
 311                /* Test is ending, just drop callbacks on the floor. */
 312                /* The next initialization will pick up the pieces. */
 313                return;
 314        }
 315        i = rp->rtort_pipe_count;
 316        if (i > RCU_TORTURE_PIPE_LEN)
 317                i = RCU_TORTURE_PIPE_LEN;
 318        atomic_inc(&rcu_torture_wcount[i]);
 319        if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 320                rp->rtort_mbtest = 0;
 321                rcu_torture_free(rp);
 322        } else
 323                cur_ops->deferredfree(rp);
 324}
 325
 326static void rcu_torture_deferred_free(struct rcu_torture *p)
 327{
 328        call_rcu(&p->rtort_rcu, rcu_torture_cb);
 329}
 330
 331static struct rcu_torture_ops rcu_ops = {
 332        .init = NULL,
 333        .cleanup = NULL,
 334        .readlock = rcu_torture_read_lock,
 335        .readdelay = rcu_read_delay,
 336        .readunlock = rcu_torture_read_unlock,
 337        .completed = rcu_torture_completed,
 338        .deferredfree = rcu_torture_deferred_free,
 339        .sync = synchronize_rcu,
 340        .cb_barrier = rcu_barrier,
 341        .stats = NULL,
 342        .irqcapable = 1,
 343        .name = "rcu"
 344};
 345
 346static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 347{
 348        int i;
 349        struct rcu_torture *rp;
 350        struct rcu_torture *rp1;
 351
 352        cur_ops->sync();
 353        list_add(&p->rtort_free, &rcu_torture_removed);
 354        list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 355                i = rp->rtort_pipe_count;
 356                if (i > RCU_TORTURE_PIPE_LEN)
 357                        i = RCU_TORTURE_PIPE_LEN;
 358                atomic_inc(&rcu_torture_wcount[i]);
 359                if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 360                        rp->rtort_mbtest = 0;
 361                        list_del(&rp->rtort_free);
 362                        rcu_torture_free(rp);
 363                }
 364        }
 365}
 366
 367static void rcu_sync_torture_init(void)
 368{
 369        INIT_LIST_HEAD(&rcu_torture_removed);
 370}
 371
 372static struct rcu_torture_ops rcu_sync_ops = {
 373        .init = rcu_sync_torture_init,
 374        .cleanup = NULL,
 375        .readlock = rcu_torture_read_lock,
 376        .readdelay = rcu_read_delay,
 377        .readunlock = rcu_torture_read_unlock,
 378        .completed = rcu_torture_completed,
 379        .deferredfree = rcu_sync_torture_deferred_free,
 380        .sync = synchronize_rcu,
 381        .cb_barrier = NULL,
 382        .stats = NULL,
 383        .irqcapable = 1,
 384        .name = "rcu_sync"
 385};
 386
 387/*
 388 * Definitions for rcu_bh torture testing.
 389 */
 390
 391static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 392{
 393        rcu_read_lock_bh();
 394        return 0;
 395}
 396
 397static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 398{
 399        rcu_read_unlock_bh();
 400}
 401
 402static int rcu_bh_torture_completed(void)
 403{
 404        return rcu_batches_completed_bh();
 405}
 406
 407static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 408{
 409        call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 410}
 411
 412struct rcu_bh_torture_synchronize {
 413        struct rcu_head head;
 414        struct completion completion;
 415};
 416
 417static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 418{
 419        struct rcu_bh_torture_synchronize *rcu;
 420
 421        rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 422        complete(&rcu->completion);
 423}
 424
 425static void rcu_bh_torture_synchronize(void)
 426{
 427        struct rcu_bh_torture_synchronize rcu;
 428
 429        init_completion(&rcu.completion);
 430        call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 431        wait_for_completion(&rcu.completion);
 432}
 433
 434static struct rcu_torture_ops rcu_bh_ops = {
 435        .init = NULL,
 436        .cleanup = NULL,
 437        .readlock = rcu_bh_torture_read_lock,
 438        .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 439        .readunlock = rcu_bh_torture_read_unlock,
 440        .completed = rcu_bh_torture_completed,
 441        .deferredfree = rcu_bh_torture_deferred_free,
 442        .sync = rcu_bh_torture_synchronize,
 443        .cb_barrier = rcu_barrier_bh,
 444        .stats = NULL,
 445        .irqcapable = 1,
 446        .name = "rcu_bh"
 447};
 448
 449static struct rcu_torture_ops rcu_bh_sync_ops = {
 450        .init = rcu_sync_torture_init,
 451        .cleanup = NULL,
 452        .readlock = rcu_bh_torture_read_lock,
 453        .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 454        .readunlock = rcu_bh_torture_read_unlock,
 455        .completed = rcu_bh_torture_completed,
 456        .deferredfree = rcu_sync_torture_deferred_free,
 457        .sync = rcu_bh_torture_synchronize,
 458        .cb_barrier = NULL,
 459        .stats = NULL,
 460        .irqcapable = 1,
 461        .name = "rcu_bh_sync"
 462};
 463
 464/*
 465 * Definitions for srcu torture testing.
 466 */
 467
 468static struct srcu_struct srcu_ctl;
 469
 470static void srcu_torture_init(void)
 471{
 472        init_srcu_struct(&srcu_ctl);
 473        rcu_sync_torture_init();
 474}
 475
 476static void srcu_torture_cleanup(void)
 477{
 478        synchronize_srcu(&srcu_ctl);
 479        cleanup_srcu_struct(&srcu_ctl);
 480}
 481
 482static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 483{
 484        return srcu_read_lock(&srcu_ctl);
 485}
 486
 487static void srcu_read_delay(struct rcu_random_state *rrsp)
 488{
 489        long delay;
 490        const long uspertick = 1000000 / HZ;
 491        const long longdelay = 10;
 492
 493        /* We want there to be long-running readers, but not all the time. */
 494
 495        delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 496        if (!delay)
 497                schedule_timeout_interruptible(longdelay);
 498}
 499
 500static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 501{
 502        srcu_read_unlock(&srcu_ctl, idx);
 503}
 504
 505static int srcu_torture_completed(void)
 506{
 507        return srcu_batches_completed(&srcu_ctl);
 508}
 509
 510static void srcu_torture_synchronize(void)
 511{
 512        synchronize_srcu(&srcu_ctl);
 513}
 514
 515static int srcu_torture_stats(char *page)
 516{
 517        int cnt = 0;
 518        int cpu;
 519        int idx = srcu_ctl.completed & 0x1;
 520
 521        cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 522                       torture_type, TORTURE_FLAG, idx);
 523        for_each_possible_cpu(cpu) {
 524                cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 525                               per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 526                               per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 527        }
 528        cnt += sprintf(&page[cnt], "\n");
 529        return cnt;
 530}
 531
 532static struct rcu_torture_ops srcu_ops = {
 533        .init = srcu_torture_init,
 534        .cleanup = srcu_torture_cleanup,
 535        .readlock = srcu_torture_read_lock,
 536        .readdelay = srcu_read_delay,
 537        .readunlock = srcu_torture_read_unlock,
 538        .completed = srcu_torture_completed,
 539        .deferredfree = rcu_sync_torture_deferred_free,
 540        .sync = srcu_torture_synchronize,
 541        .cb_barrier = NULL,
 542        .stats = srcu_torture_stats,
 543        .name = "srcu"
 544};
 545
 546/*
 547 * Definitions for sched torture testing.
 548 */
 549
 550static int sched_torture_read_lock(void)
 551{
 552        preempt_disable();
 553        return 0;
 554}
 555
 556static void sched_torture_read_unlock(int idx)
 557{
 558        preempt_enable();
 559}
 560
 561static int sched_torture_completed(void)
 562{
 563        return 0;
 564}
 565
 566static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 567{
 568        call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 569}
 570
 571static void sched_torture_synchronize(void)
 572{
 573        synchronize_sched();
 574}
 575
 576static struct rcu_torture_ops sched_ops = {
 577        .init = rcu_sync_torture_init,
 578        .cleanup = NULL,
 579        .readlock = sched_torture_read_lock,
 580        .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 581        .readunlock = sched_torture_read_unlock,
 582        .completed = sched_torture_completed,
 583        .deferredfree = rcu_sched_torture_deferred_free,
 584        .sync = sched_torture_synchronize,
 585        .cb_barrier = rcu_barrier_sched,
 586        .stats = NULL,
 587        .irqcapable = 1,
 588        .name = "sched"
 589};
 590
 591static struct rcu_torture_ops sched_ops_sync = {
 592        .init = rcu_sync_torture_init,
 593        .cleanup = NULL,
 594        .readlock = sched_torture_read_lock,
 595        .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
 596        .readunlock = sched_torture_read_unlock,
 597        .completed = sched_torture_completed,
 598        .deferredfree = rcu_sync_torture_deferred_free,
 599        .sync = sched_torture_synchronize,
 600        .cb_barrier = NULL,
 601        .stats = NULL,
 602        .name = "sched_sync"
 603};
 604
 605/*
 606 * RCU torture writer kthread.  Repeatedly substitutes a new structure
 607 * for that pointed to by rcu_torture_current, freeing the old structure
 608 * after a series of grace periods (the "pipeline").
 609 */
 610static int
 611rcu_torture_writer(void *arg)
 612{
 613        int i;
 614        long oldbatch = rcu_batches_completed();
 615        struct rcu_torture *rp;
 616        struct rcu_torture *old_rp;
 617        static DEFINE_RCU_RANDOM(rand);
 618
 619        VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 620        set_user_nice(current, 19);
 621
 622        do {
 623                schedule_timeout_uninterruptible(1);
 624                if ((rp = rcu_torture_alloc()) == NULL)
 625                        continue;
 626                rp->rtort_pipe_count = 0;
 627                udelay(rcu_random(&rand) & 0x3ff);
 628                old_rp = rcu_torture_current;
 629                rp->rtort_mbtest = 1;
 630                rcu_assign_pointer(rcu_torture_current, rp);
 631                smp_wmb();
 632                if (old_rp) {
 633                        i = old_rp->rtort_pipe_count;
 634                        if (i > RCU_TORTURE_PIPE_LEN)
 635                                i = RCU_TORTURE_PIPE_LEN;
 636                        atomic_inc(&rcu_torture_wcount[i]);
 637                        old_rp->rtort_pipe_count++;
 638                        cur_ops->deferredfree(old_rp);
 639                }
 640                rcu_torture_current_version++;
 641                oldbatch = cur_ops->completed();
 642                rcu_stutter_wait("rcu_torture_writer");
 643        } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 644        VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 645        rcutorture_shutdown_absorb("rcu_torture_writer");
 646        while (!kthread_should_stop())
 647                schedule_timeout_uninterruptible(1);
 648        return 0;
 649}
 650
 651/*
 652 * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 653 * delay between calls.
 654 */
 655static int
 656rcu_torture_fakewriter(void *arg)
 657{
 658        DEFINE_RCU_RANDOM(rand);
 659
 660        VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 661        set_user_nice(current, 19);
 662
 663        do {
 664                schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 665                udelay(rcu_random(&rand) & 0x3ff);
 666                cur_ops->sync();
 667                rcu_stutter_wait("rcu_torture_fakewriter");
 668        } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 669
 670        VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 671        rcutorture_shutdown_absorb("rcu_torture_fakewriter");
 672        while (!kthread_should_stop())
 673                schedule_timeout_uninterruptible(1);
 674        return 0;
 675}
 676
 677/*
 678 * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 679 * incrementing the corresponding element of the pipeline array.  The
 680 * counter in the element should never be greater than 1, otherwise, the
 681 * RCU implementation is broken.
 682 */
 683static void rcu_torture_timer(unsigned long unused)
 684{
 685        int idx;
 686        int completed;
 687        static DEFINE_RCU_RANDOM(rand);
 688        static DEFINE_SPINLOCK(rand_lock);
 689        struct rcu_torture *p;
 690        int pipe_count;
 691
 692        idx = cur_ops->readlock();
 693        completed = cur_ops->completed();
 694        p = rcu_dereference(rcu_torture_current);
 695        if (p == NULL) {
 696                /* Leave because rcu_torture_writer is not yet underway */
 697                cur_ops->readunlock(idx);
 698                return;
 699        }
 700        if (p->rtort_mbtest == 0)
 701                atomic_inc(&n_rcu_torture_mberror);
 702        spin_lock(&rand_lock);
 703        cur_ops->readdelay(&rand);
 704        n_rcu_torture_timers++;
 705        spin_unlock(&rand_lock);
 706        preempt_disable();
 707        pipe_count = p->rtort_pipe_count;
 708        if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 709                /* Should not happen, but... */
 710                pipe_count = RCU_TORTURE_PIPE_LEN;
 711        }
 712        ++__get_cpu_var(rcu_torture_count)[pipe_count];
 713        completed = cur_ops->completed() - completed;
 714        if (completed > RCU_TORTURE_PIPE_LEN) {
 715                /* Should not happen, but... */
 716                completed = RCU_TORTURE_PIPE_LEN;
 717        }
 718        ++__get_cpu_var(rcu_torture_batch)[completed];
 719        preempt_enable();
 720        cur_ops->readunlock(idx);
 721}
 722
 723/*
 724 * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 725 * incrementing the corresponding element of the pipeline array.  The
 726 * counter in the element should never be greater than 1, otherwise, the
 727 * RCU implementation is broken.
 728 */
 729static int
 730rcu_torture_reader(void *arg)
 731{
 732        int completed;
 733        int idx;
 734        DEFINE_RCU_RANDOM(rand);
 735        struct rcu_torture *p;
 736        int pipe_count;
 737        struct timer_list t;
 738
 739        VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 740        set_user_nice(current, 19);
 741        if (irqreader && cur_ops->irqcapable)
 742                setup_timer_on_stack(&t, rcu_torture_timer, 0);
 743
 744        do {
 745                if (irqreader && cur_ops->irqcapable) {
 746                        if (!timer_pending(&t))
 747                                mod_timer(&t, 1);
 748                }
 749                idx = cur_ops->readlock();
 750                completed = cur_ops->completed();
 751                p = rcu_dereference(rcu_torture_current);
 752                if (p == NULL) {
 753                        /* Wait for rcu_torture_writer to get underway */
 754                        cur_ops->readunlock(idx);
 755                        schedule_timeout_interruptible(HZ);
 756                        continue;
 757                }
 758                if (p->rtort_mbtest == 0)
 759                        atomic_inc(&n_rcu_torture_mberror);
 760                cur_ops->readdelay(&rand);
 761                preempt_disable();
 762                pipe_count = p->rtort_pipe_count;
 763                if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 764                        /* Should not happen, but... */
 765                        pipe_count = RCU_TORTURE_PIPE_LEN;
 766                }
 767                ++__get_cpu_var(rcu_torture_count)[pipe_count];
 768                completed = cur_ops->completed() - completed;
 769                if (completed > RCU_TORTURE_PIPE_LEN) {
 770                        /* Should not happen, but... */
 771                        completed = RCU_TORTURE_PIPE_LEN;
 772                }
 773                ++__get_cpu_var(rcu_torture_batch)[completed];
 774                preempt_enable();
 775                cur_ops->readunlock(idx);
 776                schedule();
 777                rcu_stutter_wait("rcu_torture_reader");
 778        } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 779        VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 780        rcutorture_shutdown_absorb("rcu_torture_reader");
 781        if (irqreader && cur_ops->irqcapable)
 782                del_timer_sync(&t);
 783        while (!kthread_should_stop())
 784                schedule_timeout_uninterruptible(1);
 785        return 0;
 786}
 787
 788/*
 789 * Create an RCU-torture statistics message in the specified buffer.
 790 */
 791static int
 792rcu_torture_printk(char *page)
 793{
 794        int cnt = 0;
 795        int cpu;
 796        int i;
 797        long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 798        long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 799
 800        for_each_possible_cpu(cpu) {
 801                for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 802                        pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 803                        batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 804                }
 805        }
 806        for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 807                if (pipesummary[i] != 0)
 808                        break;
 809        }
 810        cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 811        cnt += sprintf(&page[cnt],
 812                       "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 813                       "rtmbe: %d nt: %ld",
 814                       rcu_torture_current,
 815                       rcu_torture_current_version,
 816                       list_empty(&rcu_torture_freelist),
 817                       atomic_read(&n_rcu_torture_alloc),
 818                       atomic_read(&n_rcu_torture_alloc_fail),
 819                       atomic_read(&n_rcu_torture_free),
 820                       atomic_read(&n_rcu_torture_mberror),
 821                       n_rcu_torture_timers);
 822        if (atomic_read(&n_rcu_torture_mberror) != 0)
 823                cnt += sprintf(&page[cnt], " !!!");
 824        cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 825        if (i > 1) {
 826                cnt += sprintf(&page[cnt], "!!! ");
 827                atomic_inc(&n_rcu_torture_error);
 828                WARN_ON_ONCE(1);
 829        }
 830        cnt += sprintf(&page[cnt], "Reader Pipe: ");
 831        for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 832                cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 833        cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 834        cnt += sprintf(&page[cnt], "Reader Batch: ");
 835        for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 836                cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 837        cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 838        cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 839        for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 840                cnt += sprintf(&page[cnt], " %d",
 841                               atomic_read(&rcu_torture_wcount[i]));
 842        }
 843        cnt += sprintf(&page[cnt], "\n");
 844        if (cur_ops->stats)
 845                cnt += cur_ops->stats(&page[cnt]);
 846        return cnt;
 847}
 848
 849/*
 850 * Print torture statistics.  Caller must ensure that there is only
 851 * one call to this function at a given time!!!  This is normally
 852 * accomplished by relying on the module system to only have one copy
 853 * of the module loaded, and then by giving the rcu_torture_stats
 854 * kthread full control (or the init/cleanup functions when rcu_torture_stats
 855 * thread is not running).
 856 */
 857static void
 858rcu_torture_stats_print(void)
 859{
 860        int cnt;
 861
 862        cnt = rcu_torture_printk(printk_buf);
 863        printk(KERN_ALERT "%s", printk_buf);
 864}
 865
 866/*
 867 * Periodically prints torture statistics, if periodic statistics printing
 868 * was specified via the stat_interval module parameter.
 869 *
 870 * No need to worry about fullstop here, since this one doesn't reference
 871 * volatile state or register callbacks.
 872 */
 873static int
 874rcu_torture_stats(void *arg)
 875{
 876        VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 877        do {
 878                schedule_timeout_interruptible(stat_interval * HZ);
 879                rcu_torture_stats_print();
 880                rcutorture_shutdown_absorb("rcu_torture_stats");
 881        } while (!kthread_should_stop());
 882        VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 883        return 0;
 884}
 885
 886static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 887
 888/* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 889 * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 890 */
 891static void rcu_torture_shuffle_tasks(void)
 892{
 893        int i;
 894
 895        cpumask_setall(shuffle_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                cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
 906
 907        set_cpus_allowed_ptr(current, shuffle_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                                                     shuffle_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                                                     shuffle_tmp_mask);
 921        }
 922
 923        if (writer_task)
 924                set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
 925
 926        if (stats_task)
 927                set_cpus_allowed_ptr(stats_task, shuffle_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 */
 941static int
 942rcu_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 */
 957static int
 958rcu_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
 973static inline void
 974rcu_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
 985static struct notifier_block rcutorture_nb = {
 986        .notifier_call = rcutorture_shutdown_notify,
 987};
 988
 989static void
 990rcu_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                free_cpumask_var(shuffle_tmp_mask);
1016        }
1017        shuffler_task = NULL;
1018
1019        if (writer_task) {
1020                VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1021                kthread_stop(writer_task);
1022        }
1023        writer_task = NULL;
1024
1025        if (reader_tasks) {
1026                for (i = 0; i < nrealreaders; i++) {
1027                        if (reader_tasks[i]) {
1028                                VERBOSE_PRINTK_STRING(
1029                                        "Stopping rcu_torture_reader task");
1030                                kthread_stop(reader_tasks[i]);
1031                        }
1032                        reader_tasks[i] = NULL;
1033                }
1034                kfree(reader_tasks);
1035                reader_tasks = NULL;
1036        }
1037        rcu_torture_current = NULL;
1038
1039        if (fakewriter_tasks) {
1040                for (i = 0; i < nfakewriters; i++) {
1041                        if (fakewriter_tasks[i]) {
1042                                VERBOSE_PRINTK_STRING(
1043                                        "Stopping rcu_torture_fakewriter task");
1044                                kthread_stop(fakewriter_tasks[i]);
1045                        }
1046                        fakewriter_tasks[i] = NULL;
1047                }
1048                kfree(fakewriter_tasks);
1049                fakewriter_tasks = NULL;
1050        }
1051
1052        if (stats_task) {
1053                VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1054                kthread_stop(stats_task);
1055        }
1056        stats_task = NULL;
1057
1058        /* Wait for all RCU callbacks to fire.  */
1059
1060        if (cur_ops->cb_barrier != NULL)
1061                cur_ops->cb_barrier();
1062
1063        rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1064
1065        if (cur_ops->cleanup)
1066                cur_ops->cleanup();
1067        if (atomic_read(&n_rcu_torture_error))
1068                rcu_torture_print_module_parms("End of test: FAILURE");
1069        else
1070                rcu_torture_print_module_parms("End of test: SUCCESS");
1071}
1072
1073static int __init
1074rcu_torture_init(void)
1075{
1076        int i;
1077        int cpu;
1078        int firsterr = 0;
1079        static struct rcu_torture_ops *torture_ops[] =
1080                { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
1081                  &srcu_ops, &sched_ops, &sched_ops_sync, };
1082
1083        mutex_lock(&fullstop_mutex);
1084
1085        /* Process args and tell the world that the torturer is on the job. */
1086        for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1087                cur_ops = torture_ops[i];
1088                if (strcmp(torture_type, cur_ops->name) == 0)
1089                        break;
1090        }
1091        if (i == ARRAY_SIZE(torture_ops)) {
1092                printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
1093                       torture_type);
1094                mutex_unlock(&fullstop_mutex);
1095                return (-EINVAL);
1096        }
1097        if (cur_ops->init)
1098                cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1099
1100        if (nreaders >= 0)
1101                nrealreaders = nreaders;
1102        else
1103                nrealreaders = 2 * num_online_cpus();
1104        rcu_torture_print_module_parms("Start of test");
1105        fullstop = FULLSTOP_DONTSTOP;
1106
1107        /* Set up the freelist. */
1108
1109        INIT_LIST_HEAD(&rcu_torture_freelist);
1110        for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1111                rcu_tortures[i].rtort_mbtest = 0;
1112                list_add_tail(&rcu_tortures[i].rtort_free,
1113                              &rcu_torture_freelist);
1114        }
1115
1116        /* Initialize the statistics so that each run gets its own numbers. */
1117
1118        rcu_torture_current = NULL;
1119        rcu_torture_current_version = 0;
1120        atomic_set(&n_rcu_torture_alloc, 0);
1121        atomic_set(&n_rcu_torture_alloc_fail, 0);
1122        atomic_set(&n_rcu_torture_free, 0);
1123        atomic_set(&n_rcu_torture_mberror, 0);
1124        atomic_set(&n_rcu_torture_error, 0);
1125        for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1126                atomic_set(&rcu_torture_wcount[i], 0);
1127        for_each_possible_cpu(cpu) {
1128                for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1129                        per_cpu(rcu_torture_count, cpu)[i] = 0;
1130                        per_cpu(rcu_torture_batch, cpu)[i] = 0;
1131                }
1132        }
1133
1134        /* Start up the kthreads. */
1135
1136        VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1137        writer_task = kthread_run(rcu_torture_writer, NULL,
1138                                  "rcu_torture_writer");
1139        if (IS_ERR(writer_task)) {
1140                firsterr = PTR_ERR(writer_task);
1141                VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1142                writer_task = NULL;
1143                goto unwind;
1144        }
1145        fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1146                                   GFP_KERNEL);
1147        if (fakewriter_tasks == NULL) {
1148                VERBOSE_PRINTK_ERRSTRING("out of memory");
1149                firsterr = -ENOMEM;
1150                goto unwind;
1151        }
1152        for (i = 0; i < nfakewriters; i++) {
1153                VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1154                fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1155                                                  "rcu_torture_fakewriter");
1156                if (IS_ERR(fakewriter_tasks[i])) {
1157                        firsterr = PTR_ERR(fakewriter_tasks[i]);
1158                        VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1159                        fakewriter_tasks[i] = NULL;
1160                        goto unwind;
1161                }
1162        }
1163        reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1164                               GFP_KERNEL);
1165        if (reader_tasks == NULL) {
1166                VERBOSE_PRINTK_ERRSTRING("out of memory");
1167                firsterr = -ENOMEM;
1168                goto unwind;
1169        }
1170        for (i = 0; i < nrealreaders; i++) {
1171                VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1172                reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1173                                              "rcu_torture_reader");
1174                if (IS_ERR(reader_tasks[i])) {
1175                        firsterr = PTR_ERR(reader_tasks[i]);
1176                        VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1177                        reader_tasks[i] = NULL;
1178                        goto unwind;
1179                }
1180        }
1181        if (stat_interval > 0) {
1182                VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1183                stats_task = kthread_run(rcu_torture_stats, NULL,
1184                                        "rcu_torture_stats");
1185                if (IS_ERR(stats_task)) {
1186                        firsterr = PTR_ERR(stats_task);
1187                        VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1188                        stats_task = NULL;
1189                        goto unwind;
1190                }
1191        }
1192        if (test_no_idle_hz) {
1193                rcu_idle_cpu = num_online_cpus() - 1;
1194
1195                if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1196                        firsterr = -ENOMEM;
1197                        VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1198                        goto unwind;
1199                }
1200
1201                /* Create the shuffler thread */
1202                shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1203                                          "rcu_torture_shuffle");
1204                if (IS_ERR(shuffler_task)) {
1205                        free_cpumask_var(shuffle_tmp_mask);
1206                        firsterr = PTR_ERR(shuffler_task);
1207                        VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1208                        shuffler_task = NULL;
1209                        goto unwind;
1210                }
1211        }
1212        if (stutter < 0)
1213                stutter = 0;
1214        if (stutter) {
1215                /* Create the stutter thread */
1216                stutter_task = kthread_run(rcu_torture_stutter, NULL,
1217                                          "rcu_torture_stutter");
1218                if (IS_ERR(stutter_task)) {
1219                        firsterr = PTR_ERR(stutter_task);
1220                        VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1221                        stutter_task = NULL;
1222                        goto unwind;
1223                }
1224        }
1225        register_reboot_notifier(&rcutorture_nb);
1226        mutex_unlock(&fullstop_mutex);
1227        return 0;
1228
1229unwind:
1230        mutex_unlock(&fullstop_mutex);
1231        rcu_torture_cleanup();
1232        return firsterr;
1233}
1234
1235module_init(rcu_torture_init);
1236module_exit(rcu_torture_cleanup);
1237