SAFE public projects git trees. - safe/jmp/linux-2.6/blob - kernel/rcutorture.c

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