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