kernel/rcutorture.c

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