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