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/reboot.h>
  43 #include <linux/freezer.h>
  44 #include <linux/cpu.h>
  45 #include <linux/delay.h>
  46 #include <linux/stat.h>
  47 #include <linux/srcu.h>
  48 #include <linux/slab.h>
  49 #include <asm/byteorder.h>
  50
  51 MODULE_LICENSE("GPL");
  52 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
  53               "Josh Triplett <josh@freedesktop.org>");
  54
  55 static int nreaders = -1;       /* # reader threads, defaults to 2*ncpus */
  56 static int nfakewriters = 4;    /* # fake writer threads */
  57 static int stat_interval;       /* Interval between stats, in seconds. */
  58                                 /*  Defaults to "only at end of test". */
  59 static int verbose;             /* Print more debug info. */
  60 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
  61 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
  62 static int stutter = 5;         /* Start/stop testing interval (in sec) */
  63 static int irqreader = 1;       /* RCU readers from irq (timers). */
  64 static int fqs_duration = 0;    /* Duration of bursts (us), 0 to disable. */
  65 static int fqs_holdoff = 0;     /* Hold time within burst (us). */
  66 static int fqs_stutter = 3;     /* Wait time between bursts (s). */
  67 static int test_boost = 1;      /* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
  68 static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
  69 static int test_boost_duration = 4; /* Duration of each boost test, seconds. */
  70 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
  71
  72 module_param(nreaders, int, 0444);
  73 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  74 module_param(nfakewriters, int, 0444);
  75 MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
  76 module_param(stat_interval, int, 0444);
  77 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  78 module_param(verbose, bool, 0444);
  79 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  80 module_param(test_no_idle_hz, bool, 0444);
  81 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  82 module_param(shuffle_interval, int, 0444);
  83 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  84 module_param(stutter, int, 0444);
  85 MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
  86 module_param(irqreader, int, 0444);
  87 MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
  88 module_param(fqs_duration, int, 0444);
  89 MODULE_PARM_DESC(fqs_duration, "Duration of fqs bursts (us)");
  90 module_param(fqs_holdoff, int, 0444);
  91 MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
  92 module_param(fqs_stutter, int, 0444);
  93 MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
  94 module_param(test_boost, int, 0444);
  95 MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
  96 module_param(test_boost_interval, int, 0444);
  97 MODULE_PARM_DESC(test_boost_interval, "Interval between boost tests, seconds.");
  98 module_param(test_boost_duration, int, 0444);
  99 MODULE_PARM_DESC(test_boost_duration, "Duration of each boost test, seconds.");
 100 module_param(torture_type, charp, 0444);
 101 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
 102
 103 #define TORTURE_FLAG "-torture:"
 104 #define PRINTK_STRING(s) \
 105         do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 106 #define VERBOSE_PRINTK_STRING(s) \
 107         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 108 #define VERBOSE_PRINTK_ERRSTRING(s) \
 109         do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
 110
 111 static char printk_buf[4096];
 112
 113 static int nrealreaders;
 114 static struct task_struct *writer_task;
 115 static struct task_struct **fakewriter_tasks;
 116 static struct task_struct **reader_tasks;
 117 static struct task_struct *stats_task;
 118 static struct task_struct *shuffler_task;
 119 static struct task_struct *stutter_task;
 120 static struct task_struct *fqs_task;
 121 static struct task_struct *boost_tasks[NR_CPUS];
 122
 123 #define RCU_TORTURE_PIPE_LEN 10
 124
 125 struct rcu_torture {
 126         struct rcu_head rtort_rcu;
 127         int rtort_pipe_count;
 128         struct list_head rtort_free;
 129         int rtort_mbtest;
 130 };
 131
 132 static LIST_HEAD(rcu_torture_freelist);
 133 static struct rcu_torture __rcu *rcu_torture_current;
 134 static long rcu_torture_current_version;
 135 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 136 static DEFINE_SPINLOCK(rcu_torture_lock);
 137 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
 138         { 0 };
 139 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
 140         { 0 };
 141 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 142 static atomic_t n_rcu_torture_alloc;
 143 static atomic_t n_rcu_torture_alloc_fail;
 144 static atomic_t n_rcu_torture_free;
 145 static atomic_t n_rcu_torture_mberror;
 146 static atomic_t n_rcu_torture_error;
 147 static long n_rcu_torture_boost_ktrerror;
 148 static long n_rcu_torture_boost_rterror;
 149 static long n_rcu_torture_boost_allocerror;
 150 static long n_rcu_torture_boost_afferror;
 151 static long n_rcu_torture_boost_failure;
 152 static long n_rcu_torture_boosts;
 153 static long n_rcu_torture_timers;
 154 static struct list_head rcu_torture_removed;
 155 static cpumask_var_t shuffle_tmp_mask;
 156
 157 static int stutter_pause_test;
 158
 159 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 160 #define RCUTORTURE_RUNNABLE_INIT 1
 161 #else
 162 #define RCUTORTURE_RUNNABLE_INIT 0
 163 #endif
 164 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 165
 166 #ifdef CONFIG_RCU_BOOST
 167 #define rcu_can_boost() 1
 168 #else /* #ifdef CONFIG_RCU_BOOST */
 169 #define rcu_can_boost() 0
 170 #endif /* #else #ifdef CONFIG_RCU_BOOST */
 171
 172 static unsigned long boost_starttime;   /* jiffies of next boost test start. */
 173 DEFINE_MUTEX(boost_mutex);              /* protect setting boost_starttime */
 174                                         /*  and boost task create/destroy. */
 175
 176 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
 177
 178 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
 179 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with rcutorture running. */
 180 #define FULLSTOP_RMMOD    2     /* Normal rmmod of rcutorture. */
 181 static int fullstop = FULLSTOP_RMMOD;
 182 /*
 183  * Protect fullstop transitions and spawning of kthreads.
 184  */
 185 static DEFINE_MUTEX(fullstop_mutex);
 186
 187 /*
 188  * Detect and respond to a system shutdown.
 189  */
 190 static int
 191 rcutorture_shutdown_notify(struct notifier_block *unused1,
 192                            unsigned long unused2, void *unused3)
 193 {
 194         mutex_lock(&fullstop_mutex);
 195         if (fullstop == FULLSTOP_DONTSTOP)
 196                 fullstop = FULLSTOP_SHUTDOWN;
 197         else
 198                 printk(KERN_WARNING /* but going down anyway, so... */
 199                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 200         mutex_unlock(&fullstop_mutex);
 201         return NOTIFY_DONE;
 202 }
 203
 204 /*
 205  * Absorb kthreads into a kernel function that won't return, so that
 206  * they won't ever access module text or data again.
 207  */
 208 static void rcutorture_shutdown_absorb(char *title)
 209 {
 210         if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 211                 printk(KERN_NOTICE
 212                        "rcutorture thread %s parking due to system shutdown\n",
 213                        title);
 214                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 215         }
 216 }
 217
 218 /*
 219  * Allocate an element from the rcu_tortures pool.
 220  */
 221 static struct rcu_torture *
 222 rcu_torture_alloc(void)
 223 {
 224         struct list_head *p;
 225
 226         spin_lock_bh(&rcu_torture_lock);
 227         if (list_empty(&rcu_torture_freelist)) {
 228                 atomic_inc(&n_rcu_torture_alloc_fail);
 229                 spin_unlock_bh(&rcu_torture_lock);
 230                 return NULL;
 231         }
 232         atomic_inc(&n_rcu_torture_alloc);
 233         p = rcu_torture_freelist.next;
 234         list_del_init(p);
 235         spin_unlock_bh(&rcu_torture_lock);
 236         return container_of(p, struct rcu_torture, rtort_free);
 237 }
 238
 239 /*
 240  * Free an element to the rcu_tortures pool.
 241  */
 242 static void
 243 rcu_torture_free(struct rcu_torture *p)
 244 {
 245         atomic_inc(&n_rcu_torture_free);
 246         spin_lock_bh(&rcu_torture_lock);
 247         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 248         spin_unlock_bh(&rcu_torture_lock);
 249 }
 250
 251 struct rcu_random_state {
 252         unsigned long rrs_state;
 253         long rrs_count;
 254 };
 255
 256 #define RCU_RANDOM_MULT 39916801  /* prime */
 257 #define RCU_RANDOM_ADD  479001701 /* prime */
 258 #define RCU_RANDOM_REFRESH 10000
 259
 260 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 261
 262 /*
 263  * Crude but fast random-number generator.  Uses a linear congruential
 264  * generator, with occasional help from cpu_clock().
 265  */
 266 static unsigned long
 267 rcu_random(struct rcu_random_state *rrsp)
 268 {
 269         if (--rrsp->rrs_count < 0) {
 270                 rrsp->rrs_state += (unsigned long)local_clock();
 271                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 272         }
 273         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 274         return swahw32(rrsp->rrs_state);
 275 }
 276
 277 static void
 278 rcu_stutter_wait(char *title)
 279 {
 280         while (stutter_pause_test || !rcutorture_runnable) {
 281                 if (rcutorture_runnable)
 282                         schedule_timeout_interruptible(1);
 283                 else
 284                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 285                 rcutorture_shutdown_absorb(title);
 286         }
 287 }
 288
 289 /*
 290  * Operations vector for selecting different types of tests.
 291  */
 292
 293 struct rcu_torture_ops {
 294         void (*init)(void);
 295         void (*cleanup)(void);
 296         int (*readlock)(void);
 297         void (*read_delay)(struct rcu_random_state *rrsp);
 298         void (*readunlock)(int idx);
 299         int (*completed)(void);
 300         void (*deferred_free)(struct rcu_torture *p);
 301         void (*sync)(void);
 302         void (*cb_barrier)(void);
 303         void (*fqs)(void);
 304         int (*stats)(char *page);
 305         int irq_capable;
 306         int can_boost;
 307         char *name;
 308 };
 309
 310 static struct rcu_torture_ops *cur_ops;
 311
 312 /*
 313  * Definitions for rcu torture testing.
 314  */
 315
 316 static int rcu_torture_read_lock(void) __acquires(RCU)
 317 {
 318         rcu_read_lock();
 319         return 0;
 320 }
 321
 322 static void rcu_read_delay(struct rcu_random_state *rrsp)
 323 {
 324         const unsigned long shortdelay_us = 200;
 325         const unsigned long longdelay_ms = 50;
 326
 327         /* We want a short delay sometimes to make a reader delay the grace
 328          * period, and we want a long delay occasionally to trigger
 329          * force_quiescent_state. */
 330
 331         if (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
 332                 mdelay(longdelay_ms);
 333         if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
 334                 udelay(shortdelay_us);
 335 #ifdef CONFIG_PREEMPT
 336         if (!preempt_count() && !(rcu_random(rrsp) % (nrealreaders * 20000)))
 337                 preempt_schedule();  /* No QS if preempt_disable() in effect */
 338 #endif
 339 }
 340
 341 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 342 {
 343         rcu_read_unlock();
 344 }
 345
 346 static int rcu_torture_completed(void)
 347 {
 348         return rcu_batches_completed();
 349 }
 350
 351 static void
 352 rcu_torture_cb(struct rcu_head *p)
 353 {
 354         int i;
 355         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 356
 357         if (fullstop != FULLSTOP_DONTSTOP) {
 358                 /* Test is ending, just drop callbacks on the floor. */
 359                 /* The next initialization will pick up the pieces. */
 360                 return;
 361         }
 362         i = rp->rtort_pipe_count;
 363         if (i > RCU_TORTURE_PIPE_LEN)
 364                 i = RCU_TORTURE_PIPE_LEN;
 365         atomic_inc(&rcu_torture_wcount[i]);
 366         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 367                 rp->rtort_mbtest = 0;
 368                 rcu_torture_free(rp);
 369         } else
 370                 cur_ops->deferred_free(rp);
 371 }
 372
 373 static int rcu_no_completed(void)
 374 {
 375         return 0;
 376 }
 377
 378 static void rcu_torture_deferred_free(struct rcu_torture *p)
 379 {
 380         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 381 }
 382
 383 static struct rcu_torture_ops rcu_ops = {
 384         .init           = NULL,
 385         .cleanup        = NULL,
 386         .readlock       = rcu_torture_read_lock,
 387         .read_delay     = rcu_read_delay,
 388         .readunlock     = rcu_torture_read_unlock,
 389         .completed      = rcu_torture_completed,
 390         .deferred_free  = rcu_torture_deferred_free,
 391         .sync           = synchronize_rcu,
 392         .cb_barrier     = rcu_barrier,
 393         .fqs            = rcu_force_quiescent_state,
 394         .stats          = NULL,
 395         .irq_capable    = 1,
 396         .can_boost      = rcu_can_boost(),
 397         .name           = "rcu"
 398 };
 399
 400 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 401 {
 402         int i;
 403         struct rcu_torture *rp;
 404         struct rcu_torture *rp1;
 405
 406         cur_ops->sync();
 407         list_add(&p->rtort_free, &rcu_torture_removed);
 408         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 409                 i = rp->rtort_pipe_count;
 410                 if (i > RCU_TORTURE_PIPE_LEN)
 411                         i = RCU_TORTURE_PIPE_LEN;
 412                 atomic_inc(&rcu_torture_wcount[i]);
 413                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 414                         rp->rtort_mbtest = 0;
 415                         list_del(&rp->rtort_free);
 416                         rcu_torture_free(rp);
 417                 }
 418         }
 419 }
 420
 421 static void rcu_sync_torture_init(void)
 422 {
 423         INIT_LIST_HEAD(&rcu_torture_removed);
 424 }
 425
 426 static struct rcu_torture_ops rcu_sync_ops = {
 427         .init           = rcu_sync_torture_init,
 428         .cleanup        = NULL,
 429         .readlock       = rcu_torture_read_lock,
 430         .read_delay     = rcu_read_delay,
 431         .readunlock     = rcu_torture_read_unlock,
 432         .completed      = rcu_torture_completed,
 433         .deferred_free  = rcu_sync_torture_deferred_free,
 434         .sync           = synchronize_rcu,
 435         .cb_barrier     = NULL,
 436         .fqs            = rcu_force_quiescent_state,
 437         .stats          = NULL,
 438         .irq_capable    = 1,
 439         .can_boost      = rcu_can_boost(),
 440         .name           = "rcu_sync"
 441 };
 442
 443 static struct rcu_torture_ops rcu_expedited_ops = {
 444         .init           = rcu_sync_torture_init,
 445         .cleanup        = NULL,
 446         .readlock       = rcu_torture_read_lock,
 447         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 448         .readunlock     = rcu_torture_read_unlock,
 449         .completed      = rcu_no_completed,
 450         .deferred_free  = rcu_sync_torture_deferred_free,
 451         .sync           = synchronize_rcu_expedited,
 452         .cb_barrier     = NULL,
 453         .fqs            = rcu_force_quiescent_state,
 454         .stats          = NULL,
 455         .irq_capable    = 1,
 456         .can_boost      = rcu_can_boost(),
 457         .name           = "rcu_expedited"
 458 };
 459
 460 /*
 461  * Definitions for rcu_bh torture testing.
 462  */
 463
 464 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 465 {
 466         rcu_read_lock_bh();
 467         return 0;
 468 }
 469
 470 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 471 {
 472         rcu_read_unlock_bh();
 473 }
 474
 475 static int rcu_bh_torture_completed(void)
 476 {
 477         return rcu_batches_completed_bh();
 478 }
 479
 480 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 481 {
 482         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 483 }
 484
 485 struct rcu_bh_torture_synchronize {
 486         struct rcu_head head;
 487         struct completion completion;
 488 };
 489
 490 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 491 {
 492         struct rcu_bh_torture_synchronize *rcu;
 493
 494         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
 495         complete(&rcu->completion);
 496 }
 497
 498 static void rcu_bh_torture_synchronize(void)
 499 {
 500         struct rcu_bh_torture_synchronize rcu;
 501
 502         init_rcu_head_on_stack(&rcu.head);
 503         init_completion(&rcu.completion);
 504         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
 505         wait_for_completion(&rcu.completion);
 506         destroy_rcu_head_on_stack(&rcu.head);
 507 }
 508
 509 static struct rcu_torture_ops rcu_bh_ops = {
 510         .init           = NULL,
 511         .cleanup        = NULL,
 512         .readlock       = rcu_bh_torture_read_lock,
 513         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 514         .readunlock     = rcu_bh_torture_read_unlock,
 515         .completed      = rcu_bh_torture_completed,
 516         .deferred_free  = rcu_bh_torture_deferred_free,
 517         .sync           = rcu_bh_torture_synchronize,
 518         .cb_barrier     = rcu_barrier_bh,
 519         .fqs            = rcu_bh_force_quiescent_state,
 520         .stats          = NULL,
 521         .irq_capable    = 1,
 522         .name           = "rcu_bh"
 523 };
 524
 525 static struct rcu_torture_ops rcu_bh_sync_ops = {
 526         .init           = rcu_sync_torture_init,
 527         .cleanup        = NULL,
 528         .readlock       = rcu_bh_torture_read_lock,
 529         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 530         .readunlock     = rcu_bh_torture_read_unlock,
 531         .completed      = rcu_bh_torture_completed,
 532         .deferred_free  = rcu_sync_torture_deferred_free,
 533         .sync           = rcu_bh_torture_synchronize,
 534         .cb_barrier     = NULL,
 535         .fqs            = rcu_bh_force_quiescent_state,
 536         .stats          = NULL,
 537         .irq_capable    = 1,
 538         .name           = "rcu_bh_sync"
 539 };
 540
 541 /*
 542  * Definitions for srcu torture testing.
 543  */
 544
 545 static struct srcu_struct srcu_ctl;
 546
 547 static void srcu_torture_init(void)
 548 {
 549         init_srcu_struct(&srcu_ctl);
 550         rcu_sync_torture_init();
 551 }
 552
 553 static void srcu_torture_cleanup(void)
 554 {
 555         synchronize_srcu(&srcu_ctl);
 556         cleanup_srcu_struct(&srcu_ctl);
 557 }
 558
 559 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 560 {
 561         return srcu_read_lock(&srcu_ctl);
 562 }
 563
 564 static void srcu_read_delay(struct rcu_random_state *rrsp)
 565 {
 566         long delay;
 567         const long uspertick = 1000000 / HZ;
 568         const long longdelay = 10;
 569
 570         /* We want there to be long-running readers, but not all the time. */
 571
 572         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
 573         if (!delay)
 574                 schedule_timeout_interruptible(longdelay);
 575         else
 576                 rcu_read_delay(rrsp);
 577 }
 578
 579 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 580 {
 581         srcu_read_unlock(&srcu_ctl, idx);
 582 }
 583
 584 static int srcu_torture_completed(void)
 585 {
 586         return srcu_batches_completed(&srcu_ctl);
 587 }
 588
 589 static void srcu_torture_synchronize(void)
 590 {
 591         synchronize_srcu(&srcu_ctl);
 592 }
 593
 594 static int srcu_torture_stats(char *page)
 595 {
 596         int cnt = 0;
 597         int cpu;
 598         int idx = srcu_ctl.completed & 0x1;
 599
 600         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
 601                        torture_type, TORTURE_FLAG, idx);
 602         for_each_possible_cpu(cpu) {
 603                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
 604                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
 605                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
 606         }
 607         cnt += sprintf(&page[cnt], "\n");
 608         return cnt;
 609 }
 610
 611 static struct rcu_torture_ops srcu_ops = {
 612         .init           = srcu_torture_init,
 613         .cleanup        = srcu_torture_cleanup,
 614         .readlock       = srcu_torture_read_lock,
 615         .read_delay     = srcu_read_delay,
 616         .readunlock     = srcu_torture_read_unlock,
 617         .completed      = srcu_torture_completed,
 618         .deferred_free  = rcu_sync_torture_deferred_free,
 619         .sync           = srcu_torture_synchronize,
 620         .cb_barrier     = NULL,
 621         .stats          = srcu_torture_stats,
 622         .name           = "srcu"
 623 };
 624
 625 static void srcu_torture_synchronize_expedited(void)
 626 {
 627         synchronize_srcu_expedited(&srcu_ctl);
 628 }
 629
 630 static struct rcu_torture_ops srcu_expedited_ops = {
 631         .init           = srcu_torture_init,
 632         .cleanup        = srcu_torture_cleanup,
 633         .readlock       = srcu_torture_read_lock,
 634         .read_delay     = srcu_read_delay,
 635         .readunlock     = srcu_torture_read_unlock,
 636         .completed      = srcu_torture_completed,
 637         .deferred_free  = rcu_sync_torture_deferred_free,
 638         .sync           = srcu_torture_synchronize_expedited,
 639         .cb_barrier     = NULL,
 640         .stats          = srcu_torture_stats,
 641         .name           = "srcu_expedited"
 642 };
 643
 644 /*
 645  * Definitions for sched torture testing.
 646  */
 647
 648 static int sched_torture_read_lock(void)
 649 {
 650         preempt_disable();
 651         return 0;
 652 }
 653
 654 static void sched_torture_read_unlock(int idx)
 655 {
 656         preempt_enable();
 657 }
 658
 659 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 660 {
 661         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 662 }
 663
 664 static void sched_torture_synchronize(void)
 665 {
 666         synchronize_sched();
 667 }
 668
 669 static struct rcu_torture_ops sched_ops = {
 670         .init           = rcu_sync_torture_init,
 671         .cleanup        = NULL,
 672         .readlock       = sched_torture_read_lock,
 673         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 674         .readunlock     = sched_torture_read_unlock,
 675         .completed      = rcu_no_completed,
 676         .deferred_free  = rcu_sched_torture_deferred_free,
 677         .sync           = sched_torture_synchronize,
 678         .cb_barrier     = rcu_barrier_sched,
 679         .fqs            = rcu_sched_force_quiescent_state,
 680         .stats          = NULL,
 681         .irq_capable    = 1,
 682         .name           = "sched"
 683 };
 684
 685 static struct rcu_torture_ops sched_sync_ops = {
 686         .init           = rcu_sync_torture_init,
 687         .cleanup        = NULL,
 688         .readlock       = sched_torture_read_lock,
 689         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 690         .readunlock     = sched_torture_read_unlock,
 691         .completed      = rcu_no_completed,
 692         .deferred_free  = rcu_sync_torture_deferred_free,
 693         .sync           = sched_torture_synchronize,
 694         .cb_barrier     = NULL,
 695         .fqs            = rcu_sched_force_quiescent_state,
 696         .stats          = NULL,
 697         .name           = "sched_sync"
 698 };
 699
 700 static struct rcu_torture_ops sched_expedited_ops = {
 701         .init           = rcu_sync_torture_init,
 702         .cleanup        = NULL,
 703         .readlock       = sched_torture_read_lock,
 704         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 705         .readunlock     = sched_torture_read_unlock,
 706         .completed      = rcu_no_completed,
 707         .deferred_free  = rcu_sync_torture_deferred_free,
 708         .sync           = synchronize_sched_expedited,
 709         .cb_barrier     = NULL,
 710         .fqs            = rcu_sched_force_quiescent_state,
 711         .stats          = NULL,
 712         .irq_capable    = 1,
 713         .name           = "sched_expedited"
 714 };
 715
 716 /*
 717  * RCU torture priority-boost testing.  Runs one real-time thread per
 718  * CPU for moderate bursts, repeatedly registering RCU callbacks and
 719  * spinning waiting for them to be invoked.  If a given callback takes
 720  * too long to be invoked, we assume that priority inversion has occurred.
 721  */
 722
 723 struct rcu_boost_inflight {
 724         struct rcu_head rcu;
 725         int inflight;
 726 };
 727
 728 static void rcu_torture_boost_cb(struct rcu_head *head)
 729 {
 730         struct rcu_boost_inflight *rbip =
 731                 container_of(head, struct rcu_boost_inflight, rcu);
 732
 733         smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */
 734         rbip->inflight = 0;
 735 }
 736
 737 static int rcu_torture_boost(void *arg)
 738 {
 739         unsigned long call_rcu_time;
 740         unsigned long endtime;
 741         unsigned long oldstarttime;
 742         struct rcu_boost_inflight rbi = { .inflight = 0 };
 743         struct sched_param sp;
 744
 745         VERBOSE_PRINTK_STRING("rcu_torture_boost started");
 746
 747         /* Set real-time priority. */
 748         sp.sched_priority = 1;
 749         if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
 750                 VERBOSE_PRINTK_STRING("rcu_torture_boost RT prio failed!");
 751                 n_rcu_torture_boost_rterror++;
 752         }
 753
 754         /* Each pass through the following loop does one boost-test cycle. */
 755         do {
 756                 /* Wait for the next test interval. */
 757                 oldstarttime = boost_starttime;
 758                 while (jiffies - oldstarttime > ULONG_MAX / 2) {
 759                         schedule_timeout_uninterruptible(1);
 760                         rcu_stutter_wait("rcu_torture_boost");
 761                         if (kthread_should_stop() ||
 762                             fullstop != FULLSTOP_DONTSTOP)
 763                                 goto checkwait;
 764                 }
 765
 766                 /* Do one boost-test interval. */
 767                 endtime = oldstarttime + test_boost_duration * HZ;
 768                 call_rcu_time = jiffies;
 769                 while (jiffies - endtime > ULONG_MAX / 2) {
 770                         /* If we don't have a callback in flight, post one. */
 771                         if (!rbi.inflight) {
 772                                 smp_mb(); /* RCU core before ->inflight = 1. */
 773                                 rbi.inflight = 1;
 774                                 call_rcu(&rbi.rcu, rcu_torture_boost_cb);
 775                                 if (jiffies - call_rcu_time >
 776                                          test_boost_duration * HZ - HZ / 2) {
 777                                         VERBOSE_PRINTK_STRING("rcu_torture_boost boosting failed");
 778                                         n_rcu_torture_boost_failure++;
 779                                 }
 780                                 call_rcu_time = jiffies;
 781                         }
 782                         cond_resched();
 783                         rcu_stutter_wait("rcu_torture_boost");
 784                         if (kthread_should_stop() ||
 785                             fullstop != FULLSTOP_DONTSTOP)
 786                                 goto checkwait;
 787                 }
 788
 789                 /*
 790                  * Set the start time of the next test interval.
 791                  * Yes, this is vulnerable to long delays, but such
 792                  * delays simply cause a false negative for the next
 793                  * interval.  Besides, we are running at RT priority,
 794                  * so delays should be relatively rare.
 795                  */
 796                 while (oldstarttime == boost_starttime) {
 797                         if (mutex_trylock(&boost_mutex)) {
 798                                 boost_starttime = jiffies +
 799                                                   test_boost_interval * HZ;
 800                                 n_rcu_torture_boosts++;
 801                                 mutex_unlock(&boost_mutex);
 802                                 break;
 803                         }
 804                         schedule_timeout_uninterruptible(1);
 805                 }
 806
 807                 /* Go do the stutter. */
 808 checkwait:      rcu_stutter_wait("rcu_torture_boost");
 809         } while (!kthread_should_stop() && fullstop  == FULLSTOP_DONTSTOP);
 810
 811         /* Clean up and exit. */
 812         VERBOSE_PRINTK_STRING("rcu_torture_boost task stopping");
 813         rcutorture_shutdown_absorb("rcu_torture_boost");
 814         while (!kthread_should_stop() || rbi.inflight)
 815                 schedule_timeout_uninterruptible(1);
 816         smp_mb(); /* order accesses to ->inflight before stack-frame death. */
 817         return 0;
 818 }
 819
 820 /*
 821  * RCU torture force-quiescent-state kthread.  Repeatedly induces
 822  * bursts of calls to force_quiescent_state(), increasing the probability
 823  * of occurrence of some important types of race conditions.
 824  */
 825 static int
 826 rcu_torture_fqs(void *arg)
 827 {
 828         unsigned long fqs_resume_time;
 829         int fqs_burst_remaining;
 830
 831         VERBOSE_PRINTK_STRING("rcu_torture_fqs task started");
 832         do {
 833                 fqs_resume_time = jiffies + fqs_stutter * HZ;
 834                 while (jiffies - fqs_resume_time > LONG_MAX) {
 835                         schedule_timeout_interruptible(1);
 836                 }
 837                 fqs_burst_remaining = fqs_duration;
 838                 while (fqs_burst_remaining > 0) {
 839                         cur_ops->fqs();
 840                         udelay(fqs_holdoff);
 841                         fqs_burst_remaining -= fqs_holdoff;
 842                 }
 843                 rcu_stutter_wait("rcu_torture_fqs");
 844         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 845         VERBOSE_PRINTK_STRING("rcu_torture_fqs task stopping");
 846         rcutorture_shutdown_absorb("rcu_torture_fqs");
 847         while (!kthread_should_stop())
 848                 schedule_timeout_uninterruptible(1);
 849         return 0;
 850 }
 851
 852 /*
 853  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 854  * for that pointed to by rcu_torture_current, freeing the old structure
 855  * after a series of grace periods (the "pipeline").
 856  */
 857 static int
 858 rcu_torture_writer(void *arg)
 859 {
 860         int i;
 861         long oldbatch = rcu_batches_completed();
 862         struct rcu_torture *rp;
 863         struct rcu_torture *old_rp;
 864         static DEFINE_RCU_RANDOM(rand);
 865
 866         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 867         set_user_nice(current, 19);
 868
 869         do {
 870                 schedule_timeout_uninterruptible(1);
 871                 rp = rcu_torture_alloc();
 872                 if (rp == NULL)
 873                         continue;
 874                 rp->rtort_pipe_count = 0;
 875                 udelay(rcu_random(&rand) & 0x3ff);
 876                 old_rp = rcu_dereference_check(rcu_torture_current,
 877                                                current == writer_task);
 878                 rp->rtort_mbtest = 1;
 879                 rcu_assign_pointer(rcu_torture_current, rp);
 880                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
 881                 if (old_rp) {
 882                         i = old_rp->rtort_pipe_count;
 883                         if (i > RCU_TORTURE_PIPE_LEN)
 884                                 i = RCU_TORTURE_PIPE_LEN;
 885                         atomic_inc(&rcu_torture_wcount[i]);
 886                         old_rp->rtort_pipe_count++;
 887                         cur_ops->deferred_free(old_rp);
 888                 }
 889                 rcu_torture_current_version++;
 890                 oldbatch = cur_ops->completed();
 891                 rcu_stutter_wait("rcu_torture_writer");
 892         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 893         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 894         rcutorture_shutdown_absorb("rcu_torture_writer");
 895         while (!kthread_should_stop())
 896                 schedule_timeout_uninterruptible(1);
 897         return 0;
 898 }
 899
 900 /*
 901  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 902  * delay between calls.
 903  */
 904 static int
 905 rcu_torture_fakewriter(void *arg)
 906 {
 907         DEFINE_RCU_RANDOM(rand);
 908
 909         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
 910         set_user_nice(current, 19);
 911
 912         do {
 913                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
 914                 udelay(rcu_random(&rand) & 0x3ff);
 915                 cur_ops->sync();
 916                 rcu_stutter_wait("rcu_torture_fakewriter");
 917         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 918
 919         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
 920         rcutorture_shutdown_absorb("rcu_torture_fakewriter");
 921         while (!kthread_should_stop())
 922                 schedule_timeout_uninterruptible(1);
 923         return 0;
 924 }
 925
 926 /*
 927  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
 928  * incrementing the corresponding element of the pipeline array.  The
 929  * counter in the element should never be greater than 1, otherwise, the
 930  * RCU implementation is broken.
 931  */
 932 static void rcu_torture_timer(unsigned long unused)
 933 {
 934         int idx;
 935         int completed;
 936         static DEFINE_RCU_RANDOM(rand);
 937         static DEFINE_SPINLOCK(rand_lock);
 938         struct rcu_torture *p;
 939         int pipe_count;
 940
 941         idx = cur_ops->readlock();
 942         completed = cur_ops->completed();
 943         p = rcu_dereference_check(rcu_torture_current,
 944                                   rcu_read_lock_held() ||
 945                                   rcu_read_lock_bh_held() ||
 946                                   rcu_read_lock_sched_held() ||
 947                                   srcu_read_lock_held(&srcu_ctl));
 948         if (p == NULL) {
 949                 /* Leave because rcu_torture_writer is not yet underway */
 950                 cur_ops->readunlock(idx);
 951                 return;
 952         }
 953         if (p->rtort_mbtest == 0)
 954                 atomic_inc(&n_rcu_torture_mberror);
 955         spin_lock(&rand_lock);
 956         cur_ops->read_delay(&rand);
 957         n_rcu_torture_timers++;
 958         spin_unlock(&rand_lock);
 959         preempt_disable();
 960         pipe_count = p->rtort_pipe_count;
 961         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 962                 /* Should not happen, but... */
 963                 pipe_count = RCU_TORTURE_PIPE_LEN;
 964         }
 965         __this_cpu_inc(rcu_torture_count[pipe_count]);
 966         completed = cur_ops->completed() - completed;
 967         if (completed > RCU_TORTURE_PIPE_LEN) {
 968                 /* Should not happen, but... */
 969                 completed = RCU_TORTURE_PIPE_LEN;
 970         }
 971         __this_cpu_inc(rcu_torture_batch[completed]);
 972         preempt_enable();
 973         cur_ops->readunlock(idx);
 974 }
 975
 976 /*
 977  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 978  * incrementing the corresponding element of the pipeline array.  The
 979  * counter in the element should never be greater than 1, otherwise, the
 980  * RCU implementation is broken.
 981  */
 982 static int
 983 rcu_torture_reader(void *arg)
 984 {
 985         int completed;
 986         int idx;
 987         DEFINE_RCU_RANDOM(rand);
 988         struct rcu_torture *p;
 989         int pipe_count;
 990         struct timer_list t;
 991
 992         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 993         set_user_nice(current, 19);
 994         if (irqreader && cur_ops->irq_capable)
 995                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
 996
 997         do {
 998                 if (irqreader && cur_ops->irq_capable) {
 999                         if (!timer_pending(&t))
1000                                 mod_timer(&t, jiffies + 1);
1001                 }
1002                 idx = cur_ops->readlock();
1003                 completed = cur_ops->completed();
1004                 p = rcu_dereference_check(rcu_torture_current,
1005                                           rcu_read_lock_held() ||
1006                                           rcu_read_lock_bh_held() ||
1007                                           rcu_read_lock_sched_held() ||
1008                                           srcu_read_lock_held(&srcu_ctl));
1009                 if (p == NULL) {
1010                         /* Wait for rcu_torture_writer to get underway */
1011                         cur_ops->readunlock(idx);
1012                         schedule_timeout_interruptible(HZ);
1013                         continue;
1014                 }
1015                 if (p->rtort_mbtest == 0)
1016                         atomic_inc(&n_rcu_torture_mberror);
1017                 cur_ops->read_delay(&rand);
1018                 preempt_disable();
1019                 pipe_count = p->rtort_pipe_count;
1020                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1021                         /* Should not happen, but... */
1022                         pipe_count = RCU_TORTURE_PIPE_LEN;
1023                 }
1024                 __this_cpu_inc(rcu_torture_count[pipe_count]);
1025                 completed = cur_ops->completed() - completed;
1026                 if (completed > RCU_TORTURE_PIPE_LEN) {
1027                         /* Should not happen, but... */
1028                         completed = RCU_TORTURE_PIPE_LEN;
1029                 }
1030                 __this_cpu_inc(rcu_torture_batch[completed]);
1031                 preempt_enable();
1032                 cur_ops->readunlock(idx);
1033                 schedule();
1034                 rcu_stutter_wait("rcu_torture_reader");
1035         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
1036         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
1037         rcutorture_shutdown_absorb("rcu_torture_reader");
1038         if (irqreader && cur_ops->irq_capable)
1039                 del_timer_sync(&t);
1040         while (!kthread_should_stop())
1041                 schedule_timeout_uninterruptible(1);
1042         return 0;
1043 }
1044
1045 /*
1046  * Create an RCU-torture statistics message in the specified buffer.
1047  */
1048 static int
1049 rcu_torture_printk(char *page)
1050 {
1051         int cnt = 0;
1052         int cpu;
1053         int i;
1054         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1055         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1056
1057         for_each_possible_cpu(cpu) {
1058                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1059                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
1060                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
1061                 }
1062         }
1063         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1064                 if (pipesummary[i] != 0)
1065                         break;
1066         }
1067         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
1068         cnt += sprintf(&page[cnt],
1069                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
1070                        "rtmbe: %d rtbke: %ld rtbre: %ld rtbae: %ld rtbafe: %ld "
1071                        "rtbf: %ld rtb: %ld nt: %ld",
1072                        rcu_torture_current,
1073                        rcu_torture_current_version,
1074                        list_empty(&rcu_torture_freelist),
1075                        atomic_read(&n_rcu_torture_alloc),
1076                        atomic_read(&n_rcu_torture_alloc_fail),
1077                        atomic_read(&n_rcu_torture_free),
1078                        atomic_read(&n_rcu_torture_mberror),
1079                        n_rcu_torture_boost_ktrerror,
1080                        n_rcu_torture_boost_rterror,
1081                        n_rcu_torture_boost_allocerror,
1082                        n_rcu_torture_boost_afferror,
1083                        n_rcu_torture_boost_failure,
1084                        n_rcu_torture_boosts,
1085                        n_rcu_torture_timers);
1086         if (atomic_read(&n_rcu_torture_mberror) != 0 ||
1087             n_rcu_torture_boost_ktrerror != 0 ||
1088             n_rcu_torture_boost_rterror != 0 ||
1089             n_rcu_torture_boost_allocerror != 0 ||
1090             n_rcu_torture_boost_afferror != 0 ||
1091             n_rcu_torture_boost_failure != 0)
1092                 cnt += sprintf(&page[cnt], " !!!");
1093         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
1094         if (i > 1) {
1095                 cnt += sprintf(&page[cnt], "!!! ");
1096                 atomic_inc(&n_rcu_torture_error);
1097                 WARN_ON_ONCE(1);
1098         }
1099         cnt += sprintf(&page[cnt], "Reader Pipe: ");
1100         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1101                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
1102         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
1103         cnt += sprintf(&page[cnt], "Reader Batch: ");
1104         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1105                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
1106         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
1107         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
1108         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1109                 cnt += sprintf(&page[cnt], " %d",
1110                                atomic_read(&rcu_torture_wcount[i]));
1111         }
1112         cnt += sprintf(&page[cnt], "\n");
1113         if (cur_ops->stats)
1114                 cnt += cur_ops->stats(&page[cnt]);
1115         return cnt;
1116 }
1117
1118 /*
1119  * Print torture statistics.  Caller must ensure that there is only
1120  * one call to this function at a given time!!!  This is normally
1121  * accomplished by relying on the module system to only have one copy
1122  * of the module loaded, and then by giving the rcu_torture_stats
1123  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1124  * thread is not running).
1125  */
1126 static void
1127 rcu_torture_stats_print(void)
1128 {
1129         int cnt;
1130
1131         cnt = rcu_torture_printk(printk_buf);
1132         printk(KERN_ALERT "%s", printk_buf);
1133 }
1134
1135 /*
1136  * Periodically prints torture statistics, if periodic statistics printing
1137  * was specified via the stat_interval module parameter.
1138  *
1139  * No need to worry about fullstop here, since this one doesn't reference
1140  * volatile state or register callbacks.
1141  */
1142 static int
1143 rcu_torture_stats(void *arg)
1144 {
1145         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
1146         do {
1147                 schedule_timeout_interruptible(stat_interval * HZ);
1148                 rcu_torture_stats_print();
1149                 rcutorture_shutdown_absorb("rcu_torture_stats");
1150         } while (!kthread_should_stop());
1151         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
1152         return 0;
1153 }
1154
1155 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
1156
1157 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
1158  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
1159  */
1160 static void rcu_torture_shuffle_tasks(void)
1161 {
1162         int i;
1163
1164         cpumask_setall(shuffle_tmp_mask);
1165         get_online_cpus();
1166
1167         /* No point in shuffling if there is only one online CPU (ex: UP) */
1168         if (num_online_cpus() == 1) {
1169                 put_online_cpus();
1170                 return;
1171         }
1172
1173         if (rcu_idle_cpu != -1)
1174                 cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
1175
1176         set_cpus_allowed_ptr(current, shuffle_tmp_mask);
1177
1178         if (reader_tasks) {
1179                 for (i = 0; i < nrealreaders; i++)
1180                         if (reader_tasks[i])
1181                                 set_cpus_allowed_ptr(reader_tasks[i],
1182                                                      shuffle_tmp_mask);
1183         }
1184
1185         if (fakewriter_tasks) {
1186                 for (i = 0; i < nfakewriters; i++)
1187                         if (fakewriter_tasks[i])
1188                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
1189                                                      shuffle_tmp_mask);
1190         }
1191
1192         if (writer_task)
1193                 set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
1194
1195         if (stats_task)
1196                 set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
1197
1198         if (rcu_idle_cpu == -1)
1199                 rcu_idle_cpu = num_online_cpus() - 1;
1200         else
1201                 rcu_idle_cpu--;
1202
1203         put_online_cpus();
1204 }
1205
1206 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
1207  * system to become idle at a time and cut off its timer ticks. This is meant
1208  * to test the support for such tickless idle CPU in RCU.
1209  */
1210 static int
1211 rcu_torture_shuffle(void *arg)
1212 {
1213         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
1214         do {
1215                 schedule_timeout_interruptible(shuffle_interval * HZ);
1216                 rcu_torture_shuffle_tasks();
1217                 rcutorture_shutdown_absorb("rcu_torture_shuffle");
1218         } while (!kthread_should_stop());
1219         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
1220         return 0;
1221 }
1222
1223 /* Cause the rcutorture test to "stutter", starting and stopping all
1224  * threads periodically.
1225  */
1226 static int
1227 rcu_torture_stutter(void *arg)
1228 {
1229         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
1230         do {
1231                 schedule_timeout_interruptible(stutter * HZ);
1232                 stutter_pause_test = 1;
1233                 if (!kthread_should_stop())
1234                         schedule_timeout_interruptible(stutter * HZ);
1235                 stutter_pause_test = 0;
1236                 rcutorture_shutdown_absorb("rcu_torture_stutter");
1237         } while (!kthread_should_stop());
1238         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
1239         return 0;
1240 }
1241
1242 static inline void
1243 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
1244 {
1245         printk(KERN_ALERT "%s" TORTURE_FLAG
1246                 "--- %s: nreaders=%d nfakewriters=%d "
1247                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1248                 "shuffle_interval=%d stutter=%d irqreader=%d "
1249                 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1250                 "test_boost=%d/%d test_boost_interval=%d "
1251                 "test_boost_duration=%d\n",
1252                 torture_type, tag, nrealreaders, nfakewriters,
1253                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1254                 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1255                 test_boost, cur_ops->can_boost,
1256                 test_boost_interval, test_boost_duration);
1257 }
1258
1259 static struct notifier_block rcutorture_shutdown_nb = {
1260         .notifier_call = rcutorture_shutdown_notify,
1261 };
1262
1263 static void rcutorture_booster_cleanup(int cpu)
1264 {
1265         struct task_struct *t;
1266
1267         if (boost_tasks[cpu] == NULL)
1268                 return;
1269         mutex_lock(&boost_mutex);
1270         VERBOSE_PRINTK_STRING("Stopping rcu_torture_boost task");
1271         t = boost_tasks[cpu];
1272         boost_tasks[cpu] = NULL;
1273         mutex_unlock(&boost_mutex);
1274
1275         /* This must be outside of the mutex, otherwise deadlock! */
1276         kthread_stop(t);
1277 }
1278
1279 static int rcutorture_booster_init(int cpu)
1280 {
1281         int retval;
1282
1283         if (boost_tasks[cpu] != NULL)
1284                 return 0;  /* Already created, nothing more to do. */
1285
1286         /* Don't allow time recalculation while creating a new task. */
1287         mutex_lock(&boost_mutex);
1288         VERBOSE_PRINTK_STRING("Creating rcu_torture_boost task");
1289         boost_tasks[cpu] = kthread_create(rcu_torture_boost, NULL,
1290                                           "rcu_torture_boost");
1291         if (IS_ERR(boost_tasks[cpu])) {
1292                 retval = PTR_ERR(boost_tasks[cpu]);
1293                 VERBOSE_PRINTK_STRING("rcu_torture_boost task create failed");
1294                 n_rcu_torture_boost_ktrerror++;
1295                 boost_tasks[cpu] = NULL;
1296                 mutex_unlock(&boost_mutex);
1297                 return retval;
1298         }
1299         kthread_bind(boost_tasks[cpu], cpu);
1300         wake_up_process(boost_tasks[cpu]);
1301         mutex_unlock(&boost_mutex);
1302         return 0;
1303 }
1304
1305 static int rcutorture_cpu_notify(struct notifier_block *self,
1306                                  unsigned long action, void *hcpu)
1307 {
1308         long cpu = (long)hcpu;
1309
1310         switch (action) {
1311         case CPU_ONLINE:
1312         case CPU_DOWN_FAILED:
1313                 (void)rcutorture_booster_init(cpu);
1314                 break;
1315         case CPU_DOWN_PREPARE:
1316                 rcutorture_booster_cleanup(cpu);
1317                 break;
1318         default:
1319                 break;
1320         }
1321         return NOTIFY_OK;
1322 }
1323
1324 static struct notifier_block rcutorture_cpu_nb = {
1325         .notifier_call = rcutorture_cpu_notify,
1326 };
1327
1328 static void
1329 rcu_torture_cleanup(void)
1330 {
1331         int i;
1332
1333         mutex_lock(&fullstop_mutex);
1334         if (fullstop == FULLSTOP_SHUTDOWN) {
1335                 printk(KERN_WARNING /* but going down anyway, so... */
1336                        "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
1337                 mutex_unlock(&fullstop_mutex);
1338                 schedule_timeout_uninterruptible(10);
1339                 if (cur_ops->cb_barrier != NULL)
1340                         cur_ops->cb_barrier();
1341                 return;
1342         }
1343         fullstop = FULLSTOP_RMMOD;
1344         mutex_unlock(&fullstop_mutex);
1345         unregister_reboot_notifier(&rcutorture_shutdown_nb);
1346         if (stutter_task) {
1347                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
1348                 kthread_stop(stutter_task);
1349         }
1350         stutter_task = NULL;
1351         if (shuffler_task) {
1352                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
1353                 kthread_stop(shuffler_task);
1354                 free_cpumask_var(shuffle_tmp_mask);
1355         }
1356         shuffler_task = NULL;
1357
1358         if (writer_task) {
1359                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
1360                 kthread_stop(writer_task);
1361         }
1362         writer_task = NULL;
1363
1364         if (reader_tasks) {
1365                 for (i = 0; i < nrealreaders; i++) {
1366                         if (reader_tasks[i]) {
1367                                 VERBOSE_PRINTK_STRING(
1368                                         "Stopping rcu_torture_reader task");
1369                                 kthread_stop(reader_tasks[i]);
1370                         }
1371                         reader_tasks[i] = NULL;
1372                 }
1373                 kfree(reader_tasks);
1374                 reader_tasks = NULL;
1375         }
1376         rcu_torture_current = NULL;
1377
1378         if (fakewriter_tasks) {
1379                 for (i = 0; i < nfakewriters; i++) {
1380                         if (fakewriter_tasks[i]) {
1381                                 VERBOSE_PRINTK_STRING(
1382                                         "Stopping rcu_torture_fakewriter task");
1383                                 kthread_stop(fakewriter_tasks[i]);
1384                         }
1385                         fakewriter_tasks[i] = NULL;
1386                 }
1387                 kfree(fakewriter_tasks);
1388                 fakewriter_tasks = NULL;
1389         }
1390
1391         if (stats_task) {
1392                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
1393                 kthread_stop(stats_task);
1394         }
1395         stats_task = NULL;
1396
1397         if (fqs_task) {
1398                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_fqs task");
1399                 kthread_stop(fqs_task);
1400         }
1401         fqs_task = NULL;
1402         if ((test_boost == 1 && cur_ops->can_boost) ||
1403             test_boost == 2) {
1404                 unregister_cpu_notifier(&rcutorture_cpu_nb);
1405                 for_each_possible_cpu(i)
1406                         rcutorture_booster_cleanup(i);
1407         }
1408
1409         /* Wait for all RCU callbacks to fire.  */
1410
1411         if (cur_ops->cb_barrier != NULL)
1412                 cur_ops->cb_barrier();
1413
1414         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1415
1416         if (cur_ops->cleanup)
1417                 cur_ops->cleanup();
1418         if (atomic_read(&n_rcu_torture_error))
1419                 rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
1420         else
1421                 rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
1422 }
1423
1424 static int __init
1425 rcu_torture_init(void)
1426 {
1427         int i;
1428         int cpu;
1429         int firsterr = 0;
1430         static struct rcu_torture_ops *torture_ops[] =
1431                 { &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
1432                   &rcu_bh_ops, &rcu_bh_sync_ops,
1433                   &srcu_ops, &srcu_expedited_ops,
1434                   &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
1435
1436         mutex_lock(&fullstop_mutex);
1437
1438         /* Process args and tell the world that the torturer is on the job. */
1439         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1440                 cur_ops = torture_ops[i];
1441                 if (strcmp(torture_type, cur_ops->name) == 0)
1442                         break;
1443         }
1444         if (i == ARRAY_SIZE(torture_ops)) {
1445                 printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
1446                        torture_type);
1447                 printk(KERN_ALERT "rcu-torture types:");
1448                 for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
1449                         printk(KERN_ALERT " %s", torture_ops[i]->name);
1450                 printk(KERN_ALERT "\n");
1451                 mutex_unlock(&fullstop_mutex);
1452                 return -EINVAL;
1453         }
1454         if (cur_ops->fqs == NULL && fqs_duration != 0) {
1455                 printk(KERN_ALERT "rcu-torture: ->fqs NULL and non-zero "
1456                                   "fqs_duration, fqs disabled.\n");
1457                 fqs_duration = 0;
1458         }
1459         if (cur_ops->init)
1460                 cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1461
1462         if (nreaders >= 0)
1463                 nrealreaders = nreaders;
1464         else
1465                 nrealreaders = 2 * num_online_cpus();
1466         rcu_torture_print_module_parms(cur_ops, "Start of test");
1467         fullstop = FULLSTOP_DONTSTOP;
1468
1469         /* Set up the freelist. */
1470
1471         INIT_LIST_HEAD(&rcu_torture_freelist);
1472         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1473                 rcu_tortures[i].rtort_mbtest = 0;
1474                 list_add_tail(&rcu_tortures[i].rtort_free,
1475                               &rcu_torture_freelist);
1476         }
1477
1478         /* Initialize the statistics so that each run gets its own numbers. */
1479
1480         rcu_torture_current = NULL;
1481         rcu_torture_current_version = 0;
1482         atomic_set(&n_rcu_torture_alloc, 0);
1483         atomic_set(&n_rcu_torture_alloc_fail, 0);
1484         atomic_set(&n_rcu_torture_free, 0);
1485         atomic_set(&n_rcu_torture_mberror, 0);
1486         atomic_set(&n_rcu_torture_error, 0);
1487         n_rcu_torture_boost_ktrerror = 0;
1488         n_rcu_torture_boost_rterror = 0;
1489         n_rcu_torture_boost_allocerror = 0;
1490         n_rcu_torture_boost_afferror = 0;
1491         n_rcu_torture_boost_failure = 0;
1492         n_rcu_torture_boosts = 0;
1493         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1494                 atomic_set(&rcu_torture_wcount[i], 0);
1495         for_each_possible_cpu(cpu) {
1496                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1497                         per_cpu(rcu_torture_count, cpu)[i] = 0;
1498                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
1499                 }
1500         }
1501
1502         /* Start up the kthreads. */
1503
1504         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
1505         writer_task = kthread_run(rcu_torture_writer, NULL,
1506                                   "rcu_torture_writer");
1507         if (IS_ERR(writer_task)) {
1508                 firsterr = PTR_ERR(writer_task);
1509                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
1510                 writer_task = NULL;
1511                 goto unwind;
1512         }
1513         fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1514                                    GFP_KERNEL);
1515         if (fakewriter_tasks == NULL) {
1516                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1517                 firsterr = -ENOMEM;
1518                 goto unwind;
1519         }
1520         for (i = 0; i < nfakewriters; i++) {
1521                 VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
1522                 fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
1523                                                   "rcu_torture_fakewriter");
1524                 if (IS_ERR(fakewriter_tasks[i])) {
1525                         firsterr = PTR_ERR(fakewriter_tasks[i]);
1526                         VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
1527                         fakewriter_tasks[i] = NULL;
1528                         goto unwind;
1529                 }
1530         }
1531         reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1532                                GFP_KERNEL);
1533         if (reader_tasks == NULL) {
1534                 VERBOSE_PRINTK_ERRSTRING("out of memory");
1535                 firsterr = -ENOMEM;
1536                 goto unwind;
1537         }
1538         for (i = 0; i < nrealreaders; i++) {
1539                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
1540                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
1541                                               "rcu_torture_reader");
1542                 if (IS_ERR(reader_tasks[i])) {
1543                         firsterr = PTR_ERR(reader_tasks[i]);
1544                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
1545                         reader_tasks[i] = NULL;
1546                         goto unwind;
1547                 }
1548         }
1549         if (stat_interval > 0) {
1550                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
1551                 stats_task = kthread_run(rcu_torture_stats, NULL,
1552                                         "rcu_torture_stats");
1553                 if (IS_ERR(stats_task)) {
1554                         firsterr = PTR_ERR(stats_task);
1555                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
1556                         stats_task = NULL;
1557                         goto unwind;
1558                 }
1559         }
1560         if (test_no_idle_hz) {
1561                 rcu_idle_cpu = num_online_cpus() - 1;
1562
1563                 if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
1564                         firsterr = -ENOMEM;
1565                         VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
1566                         goto unwind;
1567                 }
1568
1569                 /* Create the shuffler thread */
1570                 shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
1571                                           "rcu_torture_shuffle");
1572                 if (IS_ERR(shuffler_task)) {
1573                         free_cpumask_var(shuffle_tmp_mask);
1574                         firsterr = PTR_ERR(shuffler_task);
1575                         VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
1576                         shuffler_task = NULL;
1577                         goto unwind;
1578                 }
1579         }
1580         if (stutter < 0)
1581                 stutter = 0;
1582         if (stutter) {
1583                 /* Create the stutter thread */
1584                 stutter_task = kthread_run(rcu_torture_stutter, NULL,
1585                                           "rcu_torture_stutter");
1586                 if (IS_ERR(stutter_task)) {
1587                         firsterr = PTR_ERR(stutter_task);
1588                         VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
1589                         stutter_task = NULL;
1590                         goto unwind;
1591                 }
1592         }
1593         if (fqs_duration < 0)
1594                 fqs_duration = 0;
1595         if (fqs_duration) {
1596                 /* Create the stutter thread */
1597                 fqs_task = kthread_run(rcu_torture_fqs, NULL,
1598                                        "rcu_torture_fqs");
1599                 if (IS_ERR(fqs_task)) {
1600                         firsterr = PTR_ERR(fqs_task);
1601                         VERBOSE_PRINTK_ERRSTRING("Failed to create fqs");
1602                         fqs_task = NULL;
1603                         goto unwind;
1604                 }
1605         }
1606         if (test_boost_interval < 1)
1607                 test_boost_interval = 1;
1608         if (test_boost_duration < 2)
1609                 test_boost_duration = 2;
1610         if ((test_boost == 1 && cur_ops->can_boost) ||
1611             test_boost == 2) {
1612                 int retval;
1613
1614                 boost_starttime = jiffies + test_boost_interval * HZ;
1615                 register_cpu_notifier(&rcutorture_cpu_nb);
1616                 for_each_possible_cpu(i) {
1617                         if (cpu_is_offline(i))
1618                                 continue;  /* Heuristic: CPU can go offline. */
1619                         retval = rcutorture_booster_init(i);
1620                         if (retval < 0) {
1621                                 firsterr = retval;
1622                                 goto unwind;
1623                         }
1624                 }
1625         }
1626         register_reboot_notifier(&rcutorture_shutdown_nb);
1627         mutex_unlock(&fullstop_mutex);
1628         return 0;
1629
1630 unwind:
1631         mutex_unlock(&fullstop_mutex);
1632         rcu_torture_cleanup();
1633         return firsterr;
1634 }
1635
1636 module_init(rcu_torture_init);
1637 module_exit(rcu_torture_cleanup);