kernel/rcutorture.c

   1 /*
   2  * Read-Copy Update /proc-based torture test facility
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2005
  19  *
  20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  21  *
  22  * See also:  Documentation/RCU/torture.txt
  23  */
  24 #include <linux/types.h>
  25 #include <linux/kernel.h>
  26 #include <linux/init.h>
  27 #include <linux/module.h>
  28 #include <linux/kthread.h>
  29 #include <linux/err.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/smp.h>
  32 #include <linux/rcupdate.h>
  33 #include <linux/interrupt.h>
  34 #include <linux/sched.h>
  35 #include <asm/atomic.h>
  36 #include <linux/bitops.h>
  37 #include <linux/module.h>
  38 #include <linux/completion.h>
  39 #include <linux/moduleparam.h>
  40 #include <linux/percpu.h>
  41 #include <linux/notifier.h>
  42 #include <linux/rcuref.h>
  43 #include <linux/cpu.h>
  44 #include <linux/random.h>
  45 #include <linux/delay.h>
  46 #include <linux/byteorder/swabb.h>
  47 #include <linux/stat.h>
  48
  49 MODULE_LICENSE("GPL");
  50
  51 static int nreaders = -1;       /* # reader threads, defaults to 4*ncpus */
  52 static int stat_interval = 0;   /* Interval between stats, in seconds. */
  53                                 /*  Defaults to "only at end of test". */
  54 static int verbose = 0;         /* Print more debug info. */
  55
  56 MODULE_PARM(nreaders, "i");
  57 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  58 MODULE_PARM(stat_interval, "i");
  59 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  60 MODULE_PARM(verbose, "i");
  61 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  62 #define TORTURE_FLAG "rcutorture: "
  63 #define PRINTK_STRING(s) \
  64         do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
  65 #define VERBOSE_PRINTK_STRING(s) \
  66         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
  67 #define VERBOSE_PRINTK_ERRSTRING(s) \
  68         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
  69
  70 static char printk_buf[4096];
  71
  72 static int nrealreaders;
  73 static struct task_struct *writer_task;
  74 static struct task_struct **reader_tasks;
  75 static struct task_struct *stats_task;
  76
  77 #define RCU_TORTURE_PIPE_LEN 10
  78
  79 struct rcu_torture {
  80         struct rcu_head rtort_rcu;
  81         int rtort_pipe_count;
  82         struct list_head rtort_free;
  83         int rtort_mbtest;
  84 };
  85
  86 static int fullstop = 0;        /* stop generating callbacks at test end. */
  87 static LIST_HEAD(rcu_torture_freelist);
  88 static struct rcu_torture *rcu_torture_current = NULL;
  89 static long rcu_torture_current_version = 0;
  90 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
  91 static DEFINE_SPINLOCK(rcu_torture_lock);
  92 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
  93         { 0 };
  94 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
  95         { 0 };
  96 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
  97 atomic_t n_rcu_torture_alloc;
  98 atomic_t n_rcu_torture_alloc_fail;
  99 atomic_t n_rcu_torture_free;
 100 atomic_t n_rcu_torture_mberror;
 101 atomic_t n_rcu_torture_error;
 102
 103 /*
 104  * Allocate an element from the rcu_tortures pool.
 105  */
 106 struct rcu_torture *
 107 rcu_torture_alloc(void)
 108 {
 109         struct list_head *p;
 110
 111         spin_lock(&rcu_torture_lock);
 112         if (list_empty(&rcu_torture_freelist)) {
 113                 atomic_inc(&n_rcu_torture_alloc_fail);
 114                 spin_unlock(&rcu_torture_lock);
 115                 return NULL;
 116         }
 117         atomic_inc(&n_rcu_torture_alloc);
 118         p = rcu_torture_freelist.next;
 119         list_del_init(p);
 120         spin_unlock(&rcu_torture_lock);
 121         return container_of(p, struct rcu_torture, rtort_free);
 122 }
 123
 124 /*
 125  * Free an element to the rcu_tortures pool.
 126  */
 127 static void
 128 rcu_torture_free(struct rcu_torture *p)
 129 {
 130         atomic_inc(&n_rcu_torture_free);
 131         spin_lock(&rcu_torture_lock);
 132         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 133         spin_unlock(&rcu_torture_lock);
 134 }
 135
 136 static void
 137 rcu_torture_cb(struct rcu_head *p)
 138 {
 139         int i;
 140         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 141
 142         if (fullstop) {
 143                 /* Test is ending, just drop callbacks on the floor. */
 144                 /* The next initialization will pick up the pieces. */
 145                 return;
 146         }
 147         i = rp->rtort_pipe_count;
 148         if (i > RCU_TORTURE_PIPE_LEN)
 149                 i = RCU_TORTURE_PIPE_LEN;
 150         atomic_inc(&rcu_torture_wcount[i]);
 151         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 152                 rp->rtort_mbtest = 0;
 153                 rcu_torture_free(rp);
 154         } else
 155                 call_rcu(p, rcu_torture_cb);
 156 }
 157
 158 struct rcu_random_state {
 159         unsigned long rrs_state;
 160         unsigned long rrs_count;
 161 };
 162
 163 #define RCU_RANDOM_MULT 39916801  /* prime */
 164 #define RCU_RANDOM_ADD  479001701 /* prime */
 165 #define RCU_RANDOM_REFRESH 10000
 166
 167 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 168
 169 /*
 170  * Crude but fast random-number generator.  Uses a linear congruential
 171  * generator, with occasional help from get_random_bytes().
 172  */
 173 static long
 174 rcu_random(struct rcu_random_state *rrsp)
 175 {
 176         long refresh;
 177
 178         if (--rrsp->rrs_count < 0) {
 179                 get_random_bytes(&refresh, sizeof(refresh));
 180                 rrsp->rrs_state += refresh;
 181                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
 182         }
 183         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
 184         return swahw32(rrsp->rrs_state);
 185 }
 186
 187 /*
 188  * RCU torture writer kthread.  Repeatedly substitutes a new structure
 189  * for that pointed to by rcu_torture_current, freeing the old structure
 190  * after a series of grace periods (the "pipeline").
 191  */
 192 static int
 193 rcu_torture_writer(void *arg)
 194 {
 195         int i;
 196         long oldbatch = rcu_batches_completed();
 197         struct rcu_torture *rp;
 198         struct rcu_torture *old_rp;
 199         static DEFINE_RCU_RANDOM(rand);
 200
 201         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
 202         set_user_nice(current, 19);
 203
 204         do {
 205                 schedule_timeout_uninterruptible(1);
 206                 if (rcu_batches_completed() == oldbatch)
 207                         continue;
 208                 if ((rp = rcu_torture_alloc()) == NULL)
 209                         continue;
 210                 rp->rtort_pipe_count = 0;
 211                 udelay(rcu_random(&rand) & 0x3ff);
 212                 old_rp = rcu_torture_current;
 213                 rp->rtort_mbtest = 1;
 214                 rcu_assign_pointer(rcu_torture_current, rp);
 215                 smp_wmb();
 216                 if (old_rp != NULL) {
 217                         i = old_rp->rtort_pipe_count;
 218                         if (i > RCU_TORTURE_PIPE_LEN)
 219                                 i = RCU_TORTURE_PIPE_LEN;
 220                         atomic_inc(&rcu_torture_wcount[i]);
 221                         old_rp->rtort_pipe_count++;
 222                         call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
 223                 }
 224                 rcu_torture_current_version++;
 225                 oldbatch = rcu_batches_completed();
 226         } while (!kthread_should_stop() && !fullstop);
 227         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
 228         while (!kthread_should_stop())
 229                 schedule_timeout_uninterruptible(1);
 230         return 0;
 231 }
 232
 233 /*
 234  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 235  * incrementing the corresponding element of the pipeline array.  The
 236  * counter in the element should never be greater than 1, otherwise, the
 237  * RCU implementation is broken.
 238  */
 239 static int
 240 rcu_torture_reader(void *arg)
 241 {
 242         int completed;
 243         DEFINE_RCU_RANDOM(rand);
 244         struct rcu_torture *p;
 245         int pipe_count;
 246
 247         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
 248         set_user_nice(current, 19);
 249
 250         do {
 251                 rcu_read_lock();
 252                 completed = rcu_batches_completed();
 253                 p = rcu_dereference(rcu_torture_current);
 254                 if (p == NULL) {
 255                         /* Wait for rcu_torture_writer to get underway */
 256                         rcu_read_unlock();
 257                         schedule_timeout_interruptible(HZ);
 258                         continue;
 259                 }
 260                 if (p->rtort_mbtest == 0)
 261                         atomic_inc(&n_rcu_torture_mberror);
 262                 udelay(rcu_random(&rand) & 0x7f);
 263                 preempt_disable();
 264                 pipe_count = p->rtort_pipe_count;
 265                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
 266                         /* Should not happen, but... */
 267                         pipe_count = RCU_TORTURE_PIPE_LEN;
 268                 }
 269                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
 270                 completed = rcu_batches_completed() - completed;
 271                 if (completed > RCU_TORTURE_PIPE_LEN) {
 272                         /* Should not happen, but... */
 273                         completed = RCU_TORTURE_PIPE_LEN;
 274                 }
 275                 ++__get_cpu_var(rcu_torture_batch)[completed];
 276                 preempt_enable();
 277                 rcu_read_unlock();
 278                 schedule();
 279         } while (!kthread_should_stop() && !fullstop);
 280         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
 281         while (!kthread_should_stop())
 282                 schedule_timeout_uninterruptible(1);
 283         return 0;
 284 }
 285
 286 /*
 287  * Create an RCU-torture statistics message in the specified buffer.
 288  */
 289 static int
 290 rcu_torture_printk(char *page)
 291 {
 292         int cnt = 0;
 293         int cpu;
 294         int i;
 295         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 296         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 297
 298         for_each_cpu(cpu) {
 299                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 300                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
 301                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
 302                 }
 303         }
 304         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
 305                 if (pipesummary[i] != 0)
 306                         break;
 307         }
 308         cnt += sprintf(&page[cnt], "rcutorture: ");
 309         cnt += sprintf(&page[cnt],
 310                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
 311                        "rtmbe: %d",
 312                        rcu_torture_current,
 313                        rcu_torture_current_version,
 314                        list_empty(&rcu_torture_freelist),
 315                        atomic_read(&n_rcu_torture_alloc),
 316                        atomic_read(&n_rcu_torture_alloc_fail),
 317                        atomic_read(&n_rcu_torture_free),
 318                        atomic_read(&n_rcu_torture_mberror));
 319         if (atomic_read(&n_rcu_torture_mberror) != 0)
 320                 cnt += sprintf(&page[cnt], " !!!");
 321         cnt += sprintf(&page[cnt], "\nrcutorture: ");
 322         if (i > 1) {
 323                 cnt += sprintf(&page[cnt], "!!! ");
 324                 atomic_inc(&n_rcu_torture_error);
 325         }
 326         cnt += sprintf(&page[cnt], "Reader Pipe: ");
 327         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 328                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
 329         cnt += sprintf(&page[cnt], "\nrcutorture: ");
 330         cnt += sprintf(&page[cnt], "Reader Batch: ");
 331         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
 332                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
 333         cnt += sprintf(&page[cnt], "\nrcutorture: ");
 334         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
 335         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 336                 cnt += sprintf(&page[cnt], " %d",
 337                                atomic_read(&rcu_torture_wcount[i]));
 338         }
 339         cnt += sprintf(&page[cnt], "\n");
 340         return cnt;
 341 }
 342
 343 /*
 344  * Print torture statistics.  Caller must ensure that there is only
 345  * one call to this function at a given time!!!  This is normally
 346  * accomplished by relying on the module system to only have one copy
 347  * of the module loaded, and then by giving the rcu_torture_stats
 348  * kthread full control (or the init/cleanup functions when rcu_torture_stats
 349  * thread is not running).
 350  */
 351 static void
 352 rcu_torture_stats_print(void)
 353 {
 354         int cnt;
 355
 356         cnt = rcu_torture_printk(printk_buf);
 357         printk(KERN_ALERT "%s", printk_buf);
 358 }
 359
 360 /*
 361  * Periodically prints torture statistics, if periodic statistics printing
 362  * was specified via the stat_interval module parameter.
 363  *
 364  * No need to worry about fullstop here, since this one doesn't reference
 365  * volatile state or register callbacks.
 366  */
 367 static int
 368 rcu_torture_stats(void *arg)
 369 {
 370         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
 371         do {
 372                 schedule_timeout_interruptible(stat_interval * HZ);
 373                 rcu_torture_stats_print();
 374         } while (!kthread_should_stop());
 375         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
 376         return 0;
 377 }
 378
 379 static void
 380 rcu_torture_cleanup(void)
 381 {
 382         int i;
 383
 384         fullstop = 1;
 385         if (writer_task != NULL) {
 386                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
 387                 kthread_stop(writer_task);
 388         }
 389         writer_task = NULL;
 390
 391         if (reader_tasks != NULL) {
 392                 for (i = 0; i < nrealreaders; i++) {
 393                         if (reader_tasks[i] != NULL) {
 394                                 VERBOSE_PRINTK_STRING(
 395                                         "Stopping rcu_torture_reader task");
 396                                 kthread_stop(reader_tasks[i]);
 397                         }
 398                         reader_tasks[i] = NULL;
 399                 }
 400                 kfree(reader_tasks);
 401                 reader_tasks = NULL;
 402         }
 403         rcu_torture_current = NULL;
 404
 405         if (stats_task != NULL) {
 406                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
 407                 kthread_stop(stats_task);
 408         }
 409         stats_task = NULL;
 410
 411         /* Wait for all RCU callbacks to fire.  */
 412         rcu_barrier();
 413
 414         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 415         printk(KERN_ALERT TORTURE_FLAG
 416                "--- End of test: %s\n",
 417                atomic_read(&n_rcu_torture_error) == 0 ? "SUCCESS" : "FAILURE");
 418 }
 419
 420 static int
 421 rcu_torture_init(void)
 422 {
 423         int i;
 424         int cpu;
 425         int firsterr = 0;
 426
 427         /* Process args and tell the world that the torturer is on the job. */
 428
 429         if (nreaders >= 0)
 430                 nrealreaders = nreaders;
 431         else
 432                 nrealreaders = 2 * num_online_cpus();
 433         printk(KERN_ALERT TORTURE_FLAG
 434                "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
 435                nrealreaders, stat_interval, verbose);
 436         fullstop = 0;
 437
 438         /* Set up the freelist. */
 439
 440         INIT_LIST_HEAD(&rcu_torture_freelist);
 441         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
 442                 rcu_tortures[i].rtort_mbtest = 0;
 443                 list_add_tail(&rcu_tortures[i].rtort_free,
 444                               &rcu_torture_freelist);
 445         }
 446
 447         /* Initialize the statistics so that each run gets its own numbers. */
 448
 449         rcu_torture_current = NULL;
 450         rcu_torture_current_version = 0;
 451         atomic_set(&n_rcu_torture_alloc, 0);
 452         atomic_set(&n_rcu_torture_alloc_fail, 0);
 453         atomic_set(&n_rcu_torture_free, 0);
 454         atomic_set(&n_rcu_torture_mberror, 0);
 455         atomic_set(&n_rcu_torture_error, 0);
 456         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
 457                 atomic_set(&rcu_torture_wcount[i], 0);
 458         for_each_cpu(cpu) {
 459                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
 460                         per_cpu(rcu_torture_count, cpu)[i] = 0;
 461                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
 462                 }
 463         }
 464
 465         /* Start up the kthreads. */
 466
 467         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
 468         writer_task = kthread_run(rcu_torture_writer, NULL,
 469                                   "rcu_torture_writer");
 470         if (IS_ERR(writer_task)) {
 471                 firsterr = PTR_ERR(writer_task);
 472                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
 473                 writer_task = NULL;
 474                 goto unwind;
 475         }
 476         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
 477                                GFP_KERNEL);
 478         if (reader_tasks == NULL) {
 479                 VERBOSE_PRINTK_ERRSTRING("out of memory");
 480                 firsterr = -ENOMEM;
 481                 goto unwind;
 482         }
 483         for (i = 0; i < nrealreaders; i++) {
 484                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
 485                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
 486                                               "rcu_torture_reader");
 487                 if (IS_ERR(reader_tasks[i])) {
 488                         firsterr = PTR_ERR(reader_tasks[i]);
 489                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
 490                         reader_tasks[i] = NULL;
 491                         goto unwind;
 492                 }
 493         }
 494         if (stat_interval > 0) {
 495                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
 496                 stats_task = kthread_run(rcu_torture_stats, NULL,
 497                                         "rcu_torture_stats");
 498                 if (IS_ERR(stats_task)) {
 499                         firsterr = PTR_ERR(stats_task);
 500                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
 501                         stats_task = NULL;
 502                         goto unwind;
 503                 }
 504         }
 505         return 0;
 506
 507 unwind:
 508         rcu_torture_cleanup();
 509         return firsterr;
 510 }
 511
 512 module_init(rcu_torture_init);
 513 module_exit(rcu_torture_cleanup);