kernel/rcu/rcuperf.c

   1 /*
   2  * Read-Copy Update module-based performance-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, you can access it online at
  16  * http://www.gnu.org/licenses/gpl-2.0.html.
  17  *
  18  * Copyright (C) IBM Corporation, 2015
  19  *
  20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  21  */
  22 #include <linux/types.h>
  23 #include <linux/kernel.h>
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/kthread.h>
  27 #include <linux/err.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/smp.h>
  30 #include <linux/rcupdate.h>
  31 #include <linux/interrupt.h>
  32 #include <linux/sched.h>
  33 #include <linux/atomic.h>
  34 #include <linux/bitops.h>
  35 #include <linux/completion.h>
  36 #include <linux/moduleparam.h>
  37 #include <linux/percpu.h>
  38 #include <linux/notifier.h>
  39 #include <linux/reboot.h>
  40 #include <linux/freezer.h>
  41 #include <linux/cpu.h>
  42 #include <linux/delay.h>
  43 #include <linux/stat.h>
  44 #include <linux/srcu.h>
  45 #include <linux/slab.h>
  46 #include <asm/byteorder.h>
  47 #include <linux/torture.h>
  48 #include <linux/vmalloc.h>
  49
  50 MODULE_LICENSE("GPL");
  51 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>");
  52
  53 #define PERF_FLAG "-perf:"
  54 #define PERFOUT_STRING(s) \
  55         pr_alert("%s" PERF_FLAG s "\n", perf_type)
  56 #define VERBOSE_PERFOUT_STRING(s) \
  57         do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
  58 #define VERBOSE_PERFOUT_ERRSTRING(s) \
  59         do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
  60
  61 torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
  62 torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
  63 torture_param(int, nreaders, -1, "Number of RCU reader threads");
  64 torture_param(int, nwriters, -1, "Number of RCU updater threads");
  65 torture_param(bool, shutdown, false, "Shutdown at end of performance tests.");
  66 torture_param(bool, verbose, true, "Enable verbose debugging printk()s");
  67
  68 static char *perf_type = "rcu";
  69 module_param(perf_type, charp, 0444);
  70 MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
  71
  72 static int nrealreaders;
  73 static int nrealwriters;
  74 static struct task_struct **writer_tasks;
  75 static struct task_struct **reader_tasks;
  76 static struct task_struct *shutdown_task;
  77
  78 static u64 **writer_durations;
  79 static int *writer_n_durations;
  80 static atomic_t n_rcu_perf_reader_started;
  81 static atomic_t n_rcu_perf_writer_started;
  82 static atomic_t n_rcu_perf_writer_finished;
  83 static wait_queue_head_t shutdown_wq;
  84 static u64 t_rcu_perf_writer_started;
  85 static u64 t_rcu_perf_writer_finished;
  86 static unsigned long b_rcu_perf_writer_started;
  87 static unsigned long b_rcu_perf_writer_finished;
  88
  89 static int rcu_perf_writer_state;
  90 #define RTWS_INIT               0
  91 #define RTWS_EXP_SYNC           1
  92 #define RTWS_SYNC               2
  93 #define RTWS_IDLE               2
  94 #define RTWS_STOPPING           3
  95
  96 #define MAX_MEAS 10000
  97 #define MIN_MEAS 100
  98
  99 #if defined(MODULE) || defined(CONFIG_RCU_PERF_TEST_RUNNABLE)
 100 #define RCUPERF_RUNNABLE_INIT 1
 101 #else
 102 #define RCUPERF_RUNNABLE_INIT 0
 103 #endif
 104 static int perf_runnable = RCUPERF_RUNNABLE_INIT;
 105 module_param(perf_runnable, int, 0444);
 106 MODULE_PARM_DESC(perf_runnable, "Start rcuperf at boot");
 107
 108 /*
 109  * Operations vector for selecting different types of tests.
 110  */
 111
 112 struct rcu_perf_ops {
 113         int ptype;
 114         void (*init)(void);
 115         void (*cleanup)(void);
 116         int (*readlock)(void);
 117         void (*readunlock)(int idx);
 118         unsigned long (*started)(void);
 119         unsigned long (*completed)(void);
 120         unsigned long (*exp_completed)(void);
 121         void (*sync)(void);
 122         void (*exp_sync)(void);
 123         const char *name;
 124 };
 125
 126 static struct rcu_perf_ops *cur_ops;
 127
 128 /*
 129  * Definitions for rcu perf testing.
 130  */
 131
 132 static int rcu_perf_read_lock(void) __acquires(RCU)
 133 {
 134         rcu_read_lock();
 135         return 0;
 136 }
 137
 138 static void rcu_perf_read_unlock(int idx) __releases(RCU)
 139 {
 140         rcu_read_unlock();
 141 }
 142
 143 static unsigned long __maybe_unused rcu_no_completed(void)
 144 {
 145         return 0;
 146 }
 147
 148 static void rcu_sync_perf_init(void)
 149 {
 150 }
 151
 152 static struct rcu_perf_ops rcu_ops = {
 153         .ptype          = RCU_FLAVOR,
 154         .init           = rcu_sync_perf_init,
 155         .readlock       = rcu_perf_read_lock,
 156         .readunlock     = rcu_perf_read_unlock,
 157         .started        = rcu_batches_started,
 158         .completed      = rcu_batches_completed,
 159         .exp_completed  = rcu_exp_batches_completed,
 160         .sync           = synchronize_rcu,
 161         .exp_sync       = synchronize_rcu_expedited,
 162         .name           = "rcu"
 163 };
 164
 165 /*
 166  * Definitions for rcu_bh perf testing.
 167  */
 168
 169 static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH)
 170 {
 171         rcu_read_lock_bh();
 172         return 0;
 173 }
 174
 175 static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH)
 176 {
 177         rcu_read_unlock_bh();
 178 }
 179
 180 static struct rcu_perf_ops rcu_bh_ops = {
 181         .ptype          = RCU_BH_FLAVOR,
 182         .init           = rcu_sync_perf_init,
 183         .readlock       = rcu_bh_perf_read_lock,
 184         .readunlock     = rcu_bh_perf_read_unlock,
 185         .started        = rcu_batches_started_bh,
 186         .completed      = rcu_batches_completed_bh,
 187         .exp_completed  = rcu_exp_batches_completed_sched,
 188         .sync           = synchronize_rcu_bh,
 189         .exp_sync       = synchronize_rcu_bh_expedited,
 190         .name           = "rcu_bh"
 191 };
 192
 193 /*
 194  * Definitions for srcu perf testing.
 195  */
 196
 197 DEFINE_STATIC_SRCU(srcu_ctl_perf);
 198 static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
 199
 200 static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
 201 {
 202         return srcu_read_lock(srcu_ctlp);
 203 }
 204
 205 static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
 206 {
 207         srcu_read_unlock(srcu_ctlp, idx);
 208 }
 209
 210 static unsigned long srcu_perf_completed(void)
 211 {
 212         return srcu_batches_completed(srcu_ctlp);
 213 }
 214
 215 static void srcu_perf_synchronize(void)
 216 {
 217         synchronize_srcu(srcu_ctlp);
 218 }
 219
 220 static void srcu_perf_synchronize_expedited(void)
 221 {
 222         synchronize_srcu_expedited(srcu_ctlp);
 223 }
 224
 225 static struct rcu_perf_ops srcu_ops = {
 226         .ptype          = SRCU_FLAVOR,
 227         .init           = rcu_sync_perf_init,
 228         .readlock       = srcu_perf_read_lock,
 229         .readunlock     = srcu_perf_read_unlock,
 230         .started        = NULL,
 231         .completed      = srcu_perf_completed,
 232         .exp_completed  = srcu_perf_completed,
 233         .sync           = srcu_perf_synchronize,
 234         .exp_sync       = srcu_perf_synchronize_expedited,
 235         .name           = "srcu"
 236 };
 237
 238 /*
 239  * Definitions for sched perf testing.
 240  */
 241
 242 static int sched_perf_read_lock(void)
 243 {
 244         preempt_disable();
 245         return 0;
 246 }
 247
 248 static void sched_perf_read_unlock(int idx)
 249 {
 250         preempt_enable();
 251 }
 252
 253 static struct rcu_perf_ops sched_ops = {
 254         .ptype          = RCU_SCHED_FLAVOR,
 255         .init           = rcu_sync_perf_init,
 256         .readlock       = sched_perf_read_lock,
 257         .readunlock     = sched_perf_read_unlock,
 258         .started        = rcu_batches_started_sched,
 259         .completed      = rcu_batches_completed_sched,
 260         .exp_completed  = rcu_exp_batches_completed_sched,
 261         .sync           = synchronize_sched,
 262         .exp_sync       = synchronize_sched_expedited,
 263         .name           = "sched"
 264 };
 265
 266 #ifdef CONFIG_TASKS_RCU
 267
 268 /*
 269  * Definitions for RCU-tasks perf testing.
 270  */
 271
 272 static int tasks_perf_read_lock(void)
 273 {
 274         return 0;
 275 }
 276
 277 static void tasks_perf_read_unlock(int idx)
 278 {
 279 }
 280
 281 static struct rcu_perf_ops tasks_ops = {
 282         .ptype          = RCU_TASKS_FLAVOR,
 283         .init           = rcu_sync_perf_init,
 284         .readlock       = tasks_perf_read_lock,
 285         .readunlock     = tasks_perf_read_unlock,
 286         .started        = rcu_no_completed,
 287         .completed      = rcu_no_completed,
 288         .sync           = synchronize_rcu_tasks,
 289         .exp_sync       = synchronize_rcu_tasks,
 290         .name           = "tasks"
 291 };
 292
 293 #define RCUPERF_TASKS_OPS &tasks_ops,
 294
 295 static bool __maybe_unused torturing_tasks(void)
 296 {
 297         return cur_ops == &tasks_ops;
 298 }
 299
 300 #else /* #ifdef CONFIG_TASKS_RCU */
 301
 302 #define RCUPERF_TASKS_OPS
 303
 304 static bool __maybe_unused torturing_tasks(void)
 305 {
 306         return false;
 307 }
 308
 309 #endif /* #else #ifdef CONFIG_TASKS_RCU */
 310
 311 /*
 312  * If performance tests complete, wait for shutdown to commence.
 313  */
 314 static void rcu_perf_wait_shutdown(void)
 315 {
 316         cond_resched_rcu_qs();
 317         if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
 318                 return;
 319         while (!torture_must_stop())
 320                 schedule_timeout_uninterruptible(1);
 321 }
 322
 323 /*
 324  * RCU perf reader kthread.  Repeatedly does empty RCU read-side
 325  * critical section, minimizing update-side interference.
 326  */
 327 static int
 328 rcu_perf_reader(void *arg)
 329 {
 330         unsigned long flags;
 331         int idx;
 332         long me = (long)arg;
 333
 334         VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
 335         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 336         set_user_nice(current, MAX_NICE);
 337         atomic_inc(&n_rcu_perf_reader_started);
 338
 339         do {
 340                 local_irq_save(flags);
 341                 idx = cur_ops->readlock();
 342                 cur_ops->readunlock(idx);
 343                 local_irq_restore(flags);
 344                 rcu_perf_wait_shutdown();
 345         } while (!torture_must_stop());
 346         torture_kthread_stopping("rcu_perf_reader");
 347         return 0;
 348 }
 349
 350 /*
 351  * RCU perf writer kthread.  Repeatedly does a grace period.
 352  */
 353 static int
 354 rcu_perf_writer(void *arg)
 355 {
 356         int i = 0;
 357         int i_max;
 358         long me = (long)arg;
 359         struct sched_param sp;
 360         bool started = false, done = false, alldone = false;
 361         u64 t;
 362         u64 *wdp;
 363         u64 *wdpp = writer_durations[me];
 364
 365         VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
 366         WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
 367         WARN_ON(rcu_gp_is_normal() && gp_exp);
 368         WARN_ON(!wdpp);
 369         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 370         sp.sched_priority = 1;
 371         sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
 372
 373         if (holdoff)
 374                 schedule_timeout_uninterruptible(holdoff * HZ);
 375
 376         t = ktime_get_mono_fast_ns();
 377         if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
 378                 t_rcu_perf_writer_started = t;
 379                 if (gp_exp) {
 380                         b_rcu_perf_writer_started =
 381                                 cur_ops->exp_completed() / 2;
 382                 } else {
 383                         b_rcu_perf_writer_started =
 384                                 cur_ops->completed();
 385                 }
 386         }
 387
 388         do {
 389                 wdp = &wdpp[i];
 390                 *wdp = ktime_get_mono_fast_ns();
 391                 if (gp_exp) {
 392                         rcu_perf_writer_state = RTWS_EXP_SYNC;
 393                         cur_ops->exp_sync();
 394                 } else {
 395                         rcu_perf_writer_state = RTWS_SYNC;
 396                         cur_ops->sync();
 397                 }
 398                 rcu_perf_writer_state = RTWS_IDLE;
 399                 t = ktime_get_mono_fast_ns();
 400                 *wdp = t - *wdp;
 401                 i_max = i;
 402                 if (!started &&
 403                     atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
 404                         started = true;
 405                 if (!done && i >= MIN_MEAS) {
 406                         done = true;
 407                         sp.sched_priority = 0;
 408                         sched_setscheduler_nocheck(current,
 409                                                    SCHED_NORMAL, &sp);
 410                         pr_alert("%s" PERF_FLAG
 411                                  "rcu_perf_writer %ld has %d measurements\n",
 412                                  perf_type, me, MIN_MEAS);
 413                         if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
 414                             nrealwriters) {
 415                                 schedule_timeout_interruptible(10);
 416                                 rcu_ftrace_dump(DUMP_ALL);
 417                                 PERFOUT_STRING("Test complete");
 418                                 t_rcu_perf_writer_finished = t;
 419                                 if (gp_exp) {
 420                                         b_rcu_perf_writer_finished =
 421                                                 cur_ops->exp_completed() / 2;
 422                                 } else {
 423                                         b_rcu_perf_writer_finished =
 424                                                 cur_ops->completed();
 425                                 }
 426                                 if (shutdown) {
 427                                         smp_mb(); /* Assign before wake. */
 428                                         wake_up(&shutdown_wq);
 429                                 }
 430                         }
 431                 }
 432                 if (done && !alldone &&
 433                     atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
 434                         alldone = true;
 435                 if (started && !alldone && i < MAX_MEAS - 1)
 436                         i++;
 437                 rcu_perf_wait_shutdown();
 438         } while (!torture_must_stop());
 439         rcu_perf_writer_state = RTWS_STOPPING;
 440         writer_n_durations[me] = i_max;
 441         torture_kthread_stopping("rcu_perf_writer");
 442         return 0;
 443 }
 444
 445 static inline void
 446 rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
 447 {
 448         pr_alert("%s" PERF_FLAG
 449                  "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
 450                  perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
 451 }
 452
 453 static void
 454 rcu_perf_cleanup(void)
 455 {
 456         int i;
 457         int j;
 458         int ngps = 0;
 459         u64 *wdp;
 460         u64 *wdpp;
 461
 462         if (torture_cleanup_begin())
 463                 return;
 464
 465         if (reader_tasks) {
 466                 for (i = 0; i < nrealreaders; i++)
 467                         torture_stop_kthread(rcu_perf_reader,
 468                                              reader_tasks[i]);
 469                 kfree(reader_tasks);
 470         }
 471
 472         if (writer_tasks) {
 473                 for (i = 0; i < nrealwriters; i++) {
 474                         torture_stop_kthread(rcu_perf_writer,
 475                                              writer_tasks[i]);
 476                         if (!writer_n_durations)
 477                                 continue;
 478                         j = writer_n_durations[i];
 479                         pr_alert("%s%s writer %d gps: %d\n",
 480                                  perf_type, PERF_FLAG, i, j);
 481                         ngps += j;
 482                 }
 483                 pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
 484                          perf_type, PERF_FLAG,
 485                          t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
 486                          t_rcu_perf_writer_finished -
 487                          t_rcu_perf_writer_started,
 488                          ngps,
 489                          b_rcu_perf_writer_finished -
 490                          b_rcu_perf_writer_started);
 491                 for (i = 0; i < nrealwriters; i++) {
 492                         if (!writer_durations)
 493                                 break;
 494                         if (!writer_n_durations)
 495                                 continue;
 496                         wdpp = writer_durations[i];
 497                         if (!wdpp)
 498                                 continue;
 499                         for (j = 0; j <= writer_n_durations[i]; j++) {
 500                                 wdp = &wdpp[j];
 501                                 pr_alert("%s%s %4d writer-duration: %5d %llu\n",
 502                                         perf_type, PERF_FLAG,
 503                                         i, j, *wdp);
 504                                 if (j % 100 == 0)
 505                                         schedule_timeout_uninterruptible(1);
 506                         }
 507                         kfree(writer_durations[i]);
 508                 }
 509                 kfree(writer_tasks);
 510                 kfree(writer_durations);
 511                 kfree(writer_n_durations);
 512         }
 513
 514         /* Do flavor-specific cleanup operations.  */
 515         if (cur_ops->cleanup != NULL)
 516                 cur_ops->cleanup();
 517
 518         torture_cleanup_end();
 519 }
 520
 521 /*
 522  * Return the number if non-negative.  If -1, the number of CPUs.
 523  * If less than -1, that much less than the number of CPUs, but
 524  * at least one.
 525  */
 526 static int compute_real(int n)
 527 {
 528         int nr;
 529
 530         if (n >= 0) {
 531                 nr = n;
 532         } else {
 533                 nr = num_online_cpus() + 1 + n;
 534                 if (nr <= 0)
 535                         nr = 1;
 536         }
 537         return nr;
 538 }
 539
 540 /*
 541  * RCU perf shutdown kthread.  Just waits to be awakened, then shuts
 542  * down system.
 543  */
 544 static int
 545 rcu_perf_shutdown(void *arg)
 546 {
 547         do {
 548                 wait_event(shutdown_wq,
 549                            atomic_read(&n_rcu_perf_writer_finished) >=
 550                            nrealwriters);
 551         } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
 552         smp_mb(); /* Wake before output. */
 553         rcu_perf_cleanup();
 554         kernel_power_off();
 555         return -EINVAL;
 556 }
 557
 558 static int __init
 559 rcu_perf_init(void)
 560 {
 561         long i;
 562         int firsterr = 0;
 563         static struct rcu_perf_ops *perf_ops[] = {
 564                 &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
 565                 RCUPERF_TASKS_OPS
 566         };
 567
 568         if (!torture_init_begin(perf_type, verbose, &perf_runnable))
 569                 return -EBUSY;
 570
 571         /* Process args and tell the world that the perf'er is on the job. */
 572         for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
 573                 cur_ops = perf_ops[i];
 574                 if (strcmp(perf_type, cur_ops->name) == 0)
 575                         break;
 576         }
 577         if (i == ARRAY_SIZE(perf_ops)) {
 578                 pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
 579                          perf_type);
 580                 pr_alert("rcu-perf types:");
 581                 for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
 582                         pr_alert(" %s", perf_ops[i]->name);
 583                 pr_alert("\n");
 584                 firsterr = -EINVAL;
 585                 goto unwind;
 586         }
 587         if (cur_ops->init)
 588                 cur_ops->init();
 589
 590         nrealwriters = compute_real(nwriters);
 591         nrealreaders = compute_real(nreaders);
 592         atomic_set(&n_rcu_perf_reader_started, 0);
 593         atomic_set(&n_rcu_perf_writer_started, 0);
 594         atomic_set(&n_rcu_perf_writer_finished, 0);
 595         rcu_perf_print_module_parms(cur_ops, "Start of test");
 596
 597         /* Start up the kthreads. */
 598
 599         if (shutdown) {
 600                 init_waitqueue_head(&shutdown_wq);
 601                 firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
 602                                                   shutdown_task);
 603                 if (firsterr)
 604                         goto unwind;
 605                 schedule_timeout_uninterruptible(1);
 606         }
 607         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
 608                                GFP_KERNEL);
 609         if (reader_tasks == NULL) {
 610                 VERBOSE_PERFOUT_ERRSTRING("out of memory");
 611                 firsterr = -ENOMEM;
 612                 goto unwind;
 613         }
 614         for (i = 0; i < nrealreaders; i++) {
 615                 firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
 616                                                   reader_tasks[i]);
 617                 if (firsterr)
 618                         goto unwind;
 619         }
 620         while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
 621                 schedule_timeout_uninterruptible(1);
 622         writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
 623                                GFP_KERNEL);
 624         writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
 625                                    GFP_KERNEL);
 626         writer_n_durations =
 627                 kcalloc(nrealwriters, sizeof(*writer_n_durations),
 628                         GFP_KERNEL);
 629         if (!writer_tasks || !writer_durations || !writer_n_durations) {
 630                 VERBOSE_PERFOUT_ERRSTRING("out of memory");
 631                 firsterr = -ENOMEM;
 632                 goto unwind;
 633         }
 634         for (i = 0; i < nrealwriters; i++) {
 635                 writer_durations[i] =
 636                         kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
 637                                 GFP_KERNEL);
 638                 if (!writer_durations[i])
 639                         goto unwind;
 640                 firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
 641                                                   writer_tasks[i]);
 642                 if (firsterr)
 643                         goto unwind;
 644         }
 645         torture_init_end();
 646         return 0;
 647
 648 unwind:
 649         torture_init_end();
 650         rcu_perf_cleanup();
 651         return firsterr;
 652 }
 653
 654 module_init(rcu_perf_init);
 655 module_exit(rcu_perf_cleanup);