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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
  19  *
  20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  21  *
  22  * See also:  Documentation/RCU/torture.txt
  23  */
  24 #include <linux/types.h>
  25 #include <linux/kernel.h>
  26 #include <linux/init.h>
  27 #include <linux/module.h>
  28 #include <linux/kthread.h>
  29 #include <linux/err.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/smp.h>
  32 #include <linux/rcupdate.h>
  33 #include <linux/interrupt.h>
  34 #include <linux/sched.h>
  35 #include <asm/atomic.h>
  36 #include <linux/bitops.h>
  37 #include <linux/module.h>
  38 #include <linux/completion.h>
  39 #include <linux/moduleparam.h>
  40 #include <linux/percpu.h>
  41 #include <linux/notifier.h>
  42 #include <linux/cpu.h>
  43 #include <linux/random.h>
  44 #include <linux/delay.h>
  45 #include <linux/byteorder/swabb.h>
  46 #include <linux/stat.h>
  47
  48 MODULE_LICENSE("GPL");
  49
  50 static int nreaders = -1;       /* # reader threads, defaults to 4*ncpus */
  51 static int stat_interval;       /* Interval between stats, in seconds. */
  52                                 /*  Defaults to "only at end of test". */
  53 static int verbose;             /* Print more debug info. */
  54 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
  55 static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
  56 static char *torture_type = "rcu"; /* What to torture. */
  57
  58 module_param(nreaders, int, 0);
  59 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  60 module_param(stat_interval, int, 0);
  61 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  62 module_param(verbose, bool, 0);
  63 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  64 module_param(test_no_idle_hz, bool, 0);
  65 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  66 module_param(shuffle_interval, int, 0);
  67 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  68 module_param(torture_type, charp, 0);
  69 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu)");
  70
  71 #define TORTURE_FLAG "-torture:"
  72 #define PRINTK_STRING(s) \
  73         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  74 #define VERBOSE_PRINTK_STRING(s) \
  75         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  76 #define VERBOSE_PRINTK_ERRSTRING(s) \
  77         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
  78
  79 static char printk_buf[4096];
  80
  81 static int nrealreaders;
  82 static struct task_struct *writer_task;
  83 static struct task_struct **reader_tasks;
  84 static struct task_struct *stats_task;
  85 static struct task_struct *shuffler_task;
  86
  87 #define RCU_TORTURE_PIPE_LEN 10
  88
  89 struct rcu_torture {
  90         struct rcu_head rtort_rcu;
  91         int rtort_pipe_count;
  92         struct list_head rtort_free;
  93         int rtort_mbtest;
  94 };
  95
  96 static int fullstop = 0;        /* stop generating callbacks at test end. */
  97 static LIST_HEAD(rcu_torture_freelist);
  98 static struct rcu_torture *rcu_torture_current = NULL;
  99 static long rcu_torture_current_version = 0;
 100 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 101 static DEFINE_SPINLOCK(rcu_torture_lock);
 102 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
 103         { 0 };
 104 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
 105         { 0 };
 106 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 107 atomic_t n_rcu_torture_alloc;
 108 atomic_t n_rcu_torture_alloc_fail;
 109 atomic_t n_rcu_torture_free;
 110 atomic_t n_rcu_torture_mberror;
 111 atomic_t n_rcu_torture_error;
 112
 113 /*
 114  * Allocate an element from the rcu_tortures pool.
 115  */
 116 static struct rcu_torture *
 117 rcu_torture_alloc(void)
 118 {
 119         struct list_head *p;
 120
 121         spin_lock_bh(&rcu_torture_lock);
 122         if (list_empty(&rcu_torture_freelist)) {
 123                 atomic_inc(&n_rcu_torture_alloc_fail);
 124                 spin_unlock_bh(&rcu_torture_lock);
 125                 return NULL;
 126         }
 127         atomic_inc(&n_rcu_torture_alloc);
 128         p = rcu_torture_freelist.next;
 129         list_del_init(p);
 130         spin_unlock_bh(&rcu_torture_lock);
 131         return container_of(p, struct rcu_torture, rtort_free);
 132 }
 133
 134 /*
 135  * Free an element to the rcu_tortures pool.
 136  */
 137 static void
 138 rcu_torture_free(struct rcu_torture *p)
 139 {
 140         atomic_inc(&n_rcu_torture_free);
 141         spin_lock_bh(&rcu_torture_lock);
 142         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 143         spin_unlock_bh(&rcu_torture_lock);
 144 }
 145
 146 struct rcu_random_state {
 147         unsigned long rrs_state;
 148         unsigned long rrs_count;
 149 };
 150
 151 #define RCU_RANDOM_MULT 39916801  /* prime */
 152 #define RCU_RANDOM_ADD  479001701 /* prime */
 153 #define RCU_RANDOM_REFRESH 10000
 154
 155 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 156
 157 /*
 158  * Crude but fast random-number generator.  Uses a linear congruential
 159  * generator, with occasional help from get_random_bytes().
 160  */
 161 static long
 162 rcu_random(struct rcu_random_state *rrsp)
 163 {
 164         long refresh;
 165
 166         if (--rrsp->rrs_count < 0) {
 167                 get_random_bytes(&refresh, sizeof(refresh));
 168                 rrsp->rrs_state += refresh;
 169                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 170         }
 171         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 172         return swahw32(rrsp->rrs_state);
 173 }
 174
 175 /*
 176  * Operations vector for selecting different types of tests.
 177  */
 178
 179 struct rcu_torture_ops {
 180         void (*init)(void);
 181         void (*cleanup)(void);
 182         int (*readlock)(void);
 183         void (*readunlock)(int idx);
 184         int (*completed)(void);
 185         void (*deferredfree)(struct rcu_torture *p);
 186         int (*stats)(char *page);
 187         char *name;
 188 };
 189 static struct rcu_torture_ops *cur_ops = NULL;
 190
 191 /*
 192  * Definitions for rcu torture testing.
 193  */
 194
 195 static int rcu_torture_read_lock(void)
 196 {
 197         rcu_read_lock();
 198         return 0;
 199 }
 200
 201 static void rcu_torture_read_unlock(int idx)
 202 {
 203         rcu_read_unlock();
 204 }
 205
 206 static int rcu_torture_completed(void)
 207 {
 208         return rcu_batches_completed();
 209 }
 210
 211 static void
 212 rcu_torture_cb(struct rcu_head *p)
 213 {
 214         int i;
 215         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 216
 217         if (fullstop) {
 218                 /* Test is ending, just drop callbacks on the floor. */
 219                 /* The next initialization will pick up the pieces. */
 220                 return;
 221         }
 222         i = rp->rtort_pipe_count;
 223         if (i > RCU_TORTURE_PIPE_LEN)
 224                 i = RCU_TORTURE_PIPE_LEN;
 225         atomic_inc(&rcu_torture_wcount[i]);
 226         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 227                 rp->rtort_mbtest = 0;
 228                 rcu_torture_free(rp);
 229         } else
 230                 cur_ops->deferredfree(rp);
 231 }
 232
 233 static void rcu_torture_deferred_free(struct rcu_torture *p)
 234 {
 235         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 236 }
 237
 238 static struct rcu_torture_ops rcu_ops = {
 239         .init = NULL,
 240         .cleanup = NULL,
 241         .readlock = rcu_torture_read_lock,
 242         .readunlock = rcu_torture_read_unlock,
 243         .completed = rcu_torture_completed,
 244         .deferredfree = rcu_torture_deferred_free,
 245         .stats = NULL,
 246         .name = "rcu"
 247 };
 248
 249 static struct rcu_torture_ops *torture_ops[] =
 250         { &rcu_ops, NULL };
 251
 252 /*
 253  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 254  * for that pointed to by rcu_torture_current, freeing the old structure
 255  * after a series of grace periods (the "pipeline").
 256  */
 257 static int
 258 rcu_torture_writer(void *arg)
 259 {
 260         int i;
 261         long oldbatch = rcu_batches_completed();
 262         struct rcu_torture *rp;
 263         struct rcu_torture *old_rp;
 264         static DEFINE_RCU_RANDOM(rand);
 265
 266         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 267         set_user_nice(current, 19);
 268
 269         do {
 270                 schedule_timeout_uninterruptible(1);
 271                 if ((rp = rcu_torture_alloc()) == NULL)
 272                         continue;
 273                 rp->rtort_pipe_count = 0;
 274                 udelay(rcu_random(&rand) & 0x3ff);
 275                 old_rp = rcu_torture_current;
 276                 rp->rtort_mbtest = 1;
 277                 rcu_assign_pointer(rcu_torture_current, rp);
 278                 smp_wmb();
 279                 if (old_rp != NULL) {
 280                         i = old_rp->rtort_pipe_count;
 281                         if (i > RCU_TORTURE_PIPE_LEN)
 282                                 i = RCU_TORTURE_PIPE_LEN;
 283                         atomic_inc(&rcu_torture_wcount[i]);
 284                         old_rp->rtort_pipe_count++;
 285                         cur_ops->deferredfree(old_rp);
 286                 }
 287                 rcu_torture_current_version++;
 288                 oldbatch = cur_ops->completed();
 289         } while (!kthread_should_stop() && !fullstop);
 290         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 291         while (!kthread_should_stop())
 292                 schedule_timeout_uninterruptible(1);
 293         return 0;
 294 }
 295
 296 /*
 297  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 298  * incrementing the corresponding element of the pipeline array.  The
 299  * counter in the element should never be greater than 1, otherwise, the
 300  * RCU implementation is broken.
 301  */
 302 static int
 303 rcu_torture_reader(void *arg)
 304 {
 305         int completed;
 306         int idx;
 307         DEFINE_RCU_RANDOM(rand);
 308         struct rcu_torture *p;
 309         int pipe_count;
 310
 311         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 312         set_user_nice(current, 19);
 313
 314         do {
 315                 idx = cur_ops->readlock();
 316                 completed = cur_ops->completed();
 317                 p = rcu_dereference(rcu_torture_current);
 318                 if (p == NULL) {
 319                         /* Wait for rcu_torture_writer to get underway */
 320                         cur_ops->readunlock(idx);
 321                         schedule_timeout_interruptible(HZ);
 322                         continue;
 323                 }
 324                 if (p->rtort_mbtest == 0)
 325                         atomic_inc(&n_rcu_torture_mberror);
 326                 udelay(rcu_random(&rand) & 0x7f);
 327                 preempt_disable();
 328                 pipe_count = p->rtort_pipe_count;
 329                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 330                         /* Should not happen, but... */
 331                         pipe_count = RCU_TORTURE_PIPE_LEN;
 332                 }
 333                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 334                 completed = cur_ops->completed() - completed;
 335                 if (completed > RCU_TORTURE_PIPE_LEN) {
 336                         /* Should not happen, but... */
 337                         completed = RCU_TORTURE_PIPE_LEN;
 338                 }
 339                 ++__get_cpu_var(rcu_torture_batch)[completed];
 340                 preempt_enable();
 341                 cur_ops->readunlock(idx);
 342                 schedule();
 343         } while (!kthread_should_stop() && !fullstop);
 344         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 345         while (!kthread_should_stop())
 346                 schedule_timeout_uninterruptible(1);
 347         return 0;
 348 }
 349
 350 /*
 351  * Create an RCU-torture statistics message in the specified buffer.
 352  */
 353 static int
 354 rcu_torture_printk(char *page)
 355 {
 356         int cnt = 0;
 357         int cpu;
 358         int i;
 359         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 360         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 361
 362         for_each_possible_cpu(cpu) {
 363                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 364                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 365                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 366                 }
 367         }
 368         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 369                 if (pipesummary[i] != 0)
 370                         break;
 371         }
 372         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
 373         cnt += sprintf(&page[cnt],
 374                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 375                        "rtmbe: %d",
 376                        rcu_torture_current,
 377                        rcu_torture_current_version,
 378                        list_empty(&rcu_torture_freelist),
 379                        atomic_read(&n_rcu_torture_alloc),
 380                        atomic_read(&n_rcu_torture_alloc_fail),
 381                        atomic_read(&n_rcu_torture_free),
 382                        atomic_read(&n_rcu_torture_mberror));
 383         if (atomic_read(&n_rcu_torture_mberror) != 0)
 384                 cnt += sprintf(&page[cnt], " !!!");
 385         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 386         if (i > 1) {
 387                 cnt += sprintf(&page[cnt], "!!! ");
 388                 atomic_inc(&n_rcu_torture_error);
 389         }
 390         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 391         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 392                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 393         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 394         cnt += sprintf(&page[cnt], "Reader Batch: ");
 395         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 396                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 397         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
 398         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 399         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 400                 cnt += sprintf(&page[cnt], " %d",
 401                                atomic_read(&rcu_torture_wcount[i]));
 402         }
 403         cnt += sprintf(&page[cnt], "\n");
 404         if (cur_ops->stats != NULL)
 405                 cnt += cur_ops->stats(&page[cnt]);
 406         return cnt;
 407 }
 408
 409 /*
 410  * Print torture statistics.  Caller must ensure that there is only
 411  * one call to this function at a given time!!!  This is normally
 412  * accomplished by relying on the module system to only have one copy
 413  * of the module loaded, and then by giving the rcu_torture_stats
 414  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 415  * thread is not running).
 416  */
 417 static void
 418 rcu_torture_stats_print(void)
 419 {
 420         int cnt;
 421
 422         cnt = rcu_torture_printk(printk_buf);
 423         printk(KERN_ALERT "%s", printk_buf);
 424 }
 425
 426 /*
 427  * Periodically prints torture statistics, if periodic statistics printing
 428  * was specified via the stat_interval module parameter.
 429  *
 430  * No need to worry about fullstop here, since this one doesn't reference
 431  * volatile state or register callbacks.
 432  */
 433 static int
 434 rcu_torture_stats(void *arg)
 435 {
 436         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 437         do {
 438                 schedule_timeout_interruptible(stat_interval * HZ);
 439                 rcu_torture_stats_print();
 440         } while (!kthread_should_stop());
 441         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 442         return 0;
 443 }
 444
 445 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 446
 447 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
 448  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
 449  */
 450 void rcu_torture_shuffle_tasks(void)
 451 {
 452         cpumask_t tmp_mask = CPU_MASK_ALL;
 453         int i;
 454
 455         lock_cpu_hotplug();
 456
 457         /* No point in shuffling if there is only one online CPU (ex: UP) */
 458         if (num_online_cpus() == 1) {
 459                 unlock_cpu_hotplug();
 460                 return;
 461         }
 462
 463         if (rcu_idle_cpu != -1)
 464                 cpu_clear(rcu_idle_cpu, tmp_mask);
 465
 466         set_cpus_allowed(current, tmp_mask);
 467
 468         if (reader_tasks != NULL) {
 469                 for (i = 0; i < nrealreaders; i++)
 470                         if (reader_tasks[i])
 471                                 set_cpus_allowed(reader_tasks[i], tmp_mask);
 472         }
 473
 474         if (writer_task)
 475                 set_cpus_allowed(writer_task, tmp_mask);
 476
 477         if (stats_task)
 478                 set_cpus_allowed(stats_task, tmp_mask);
 479
 480         if (rcu_idle_cpu == -1)
 481                 rcu_idle_cpu = num_online_cpus() - 1;
 482         else
 483                 rcu_idle_cpu--;
 484
 485         unlock_cpu_hotplug();
 486 }
 487
 488 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 489  * system to become idle at a time and cut off its timer ticks. This is meant
 490  * to test the support for such tickless idle CPU in RCU.
 491  */
 492 static int
 493 rcu_torture_shuffle(void *arg)
 494 {
 495         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
 496         do {
 497                 schedule_timeout_interruptible(shuffle_interval * HZ);
 498                 rcu_torture_shuffle_tasks();
 499         } while (!kthread_should_stop());
 500         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
 501         return 0;
 502 }
 503
 504 static inline void
 505 rcu_torture_print_module_parms(char *tag)
 506 {
 507         printk(KERN_ALERT "%s" TORTURE_FLAG "--- %s: nreaders=%d "
 508                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
 509                 "shuffle_interval = %d\n",
 510                 torture_type, tag, nrealreaders, stat_interval, verbose,
 511                 test_no_idle_hz, shuffle_interval);
 512 }
 513
 514 static void
 515 rcu_torture_cleanup(void)
 516 {
 517         int i;
 518
 519         fullstop = 1;
 520         if (shuffler_task != NULL) {
 521                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
 522                 kthread_stop(shuffler_task);
 523         }
 524         shuffler_task = NULL;
 525
 526         if (writer_task != NULL) {
 527                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
 528                 kthread_stop(writer_task);
 529         }
 530         writer_task = NULL;
 531
 532         if (reader_tasks != NULL) {
 533                 for (i = 0; i < nrealreaders; i++) {
 534                         if (reader_tasks[i] != NULL) {
 535                                 VERBOSE_PRINTK_STRING(
 536                                         "Stopping rcu_torture_reader task");
 537                                 kthread_stop(reader_tasks[i]);
 538                         }
 539                         reader_tasks[i] = NULL;
 540                 }
 541                 kfree(reader_tasks);
 542                 reader_tasks = NULL;
 543         }
 544         rcu_torture_current = NULL;
 545
 546         if (stats_task != NULL) {
 547                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
 548                 kthread_stop(stats_task);
 549         }
 550         stats_task = NULL;
 551
 552         /* Wait for all RCU callbacks to fire.  */
 553         rcu_barrier();
 554
 555         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 556
 557         if (cur_ops->cleanup != NULL)
 558                 cur_ops->cleanup();
 559         if (atomic_read(&n_rcu_torture_error))
 560                 rcu_torture_print_module_parms("End of test: FAILURE");
 561         else
 562                 rcu_torture_print_module_parms("End of test: SUCCESS");
 563 }
 564
 565 static int
 566 rcu_torture_init(void)
 567 {
 568         int i;
 569         int cpu;
 570         int firsterr = 0;
 571
 572         /* Process args and tell the world that the torturer is on the job. */
 573
 574         for (i = 0; cur_ops = torture_ops[i], cur_ops != NULL; i++) {
 575                 cur_ops = torture_ops[i];
 576                 if (strcmp(torture_type, cur_ops->name) == 0) {
 577                         break;
 578                 }
 579         }
 580         if (cur_ops == NULL) {
 581                 printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
 582                        torture_type);
 583                 return (-EINVAL);
 584         }
 585         if (cur_ops->init != NULL)
 586                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
 587
 588         if (nreaders >= 0)
 589                 nrealreaders = nreaders;
 590         else
 591                 nrealreaders = 2 * num_online_cpus();
 592         rcu_torture_print_module_parms("Start of test");
 593         fullstop = 0;
 594
 595         /* Set up the freelist. */
 596
 597         INIT_LIST_HEAD(&rcu_torture_freelist);
 598         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
 599                 rcu_tortures[i].rtort_mbtest = 0;
 600                 list_add_tail(&rcu_tortures[i].rtort_free,
 601                               &rcu_torture_freelist);
 602         }
 603
 604         /* Initialize the statistics so that each run gets its own numbers. */
 605
 606         rcu_torture_current = NULL;
 607         rcu_torture_current_version = 0;
 608         atomic_set(&n_rcu_torture_alloc, 0);
 609         atomic_set(&n_rcu_torture_alloc_fail, 0);
 610         atomic_set(&n_rcu_torture_free, 0);
 611         atomic_set(&n_rcu_torture_mberror, 0);
 612         atomic_set(&n_rcu_torture_error, 0);
 613         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 614                 atomic_set(&rcu_torture_wcount[i], 0);
 615         for_each_possible_cpu(cpu) {
 616                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 617                         per_cpu(rcu_torture_count, cpu)[i] = 0;
 618                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
 619                 }
 620         }
 621
 622         /* Start up the kthreads. */
 623
 624         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
 625         writer_task = kthread_run(rcu_torture_writer, NULL,
 626                                   "rcu_torture_writer");
 627         if (IS_ERR(writer_task)) {
 628                 firsterr = PTR_ERR(writer_task);
 629                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
 630                 writer_task = NULL;
 631                 goto unwind;
 632         }
 633         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
 634                                GFP_KERNEL);
 635         if (reader_tasks == NULL) {
 636                 VERBOSE_PRINTK_ERRSTRING("out of memory");
 637                 firsterr = -ENOMEM;
 638                 goto unwind;
 639         }
 640         for (i = 0; i < nrealreaders; i++) {
 641                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
 642                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
 643                                               "rcu_torture_reader");
 644                 if (IS_ERR(reader_tasks[i])) {
 645                         firsterr = PTR_ERR(reader_tasks[i]);
 646                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
 647                         reader_tasks[i] = NULL;
 648                         goto unwind;
 649                 }
 650         }
 651         if (stat_interval > 0) {
 652                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
 653                 stats_task = kthread_run(rcu_torture_stats, NULL,
 654                                         "rcu_torture_stats");
 655                 if (IS_ERR(stats_task)) {
 656                         firsterr = PTR_ERR(stats_task);
 657                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
 658                         stats_task = NULL;
 659                         goto unwind;
 660                 }
 661         }
 662         if (test_no_idle_hz) {
 663                 rcu_idle_cpu = num_online_cpus() - 1;
 664                 /* Create the shuffler thread */
 665                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
 666                                           "rcu_torture_shuffle");
 667                 if (IS_ERR(shuffler_task)) {
 668                         firsterr = PTR_ERR(shuffler_task);
 669                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
 670                         shuffler_task = NULL;
 671                         goto unwind;
 672                 }
 673         }
 674         return 0;
 675
 676 unwind:
 677         rcu_torture_cleanup();
 678         return firsterr;
 679 }
 680
 681 module_init(rcu_torture_init);
 682 module_exit(rcu_torture_cleanup);