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
  23 #define pr_fmt(fmt) fmt
  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 <uapi/linux/sched/types.h>
  37 #include <linux/atomic.h>
  38 #include <linux/bitops.h>
  39 #include <linux/completion.h>
  40 #include <linux/moduleparam.h>
  41 #include <linux/percpu.h>
  42 #include <linux/notifier.h>
  43 #include <linux/reboot.h>
  44 #include <linux/freezer.h>
  45 #include <linux/cpu.h>
  46 #include <linux/delay.h>
  47 #include <linux/stat.h>
  48 #include <linux/srcu.h>
  49 #include <linux/slab.h>
  50 #include <asm/byteorder.h>
  51 #include <linux/torture.h>
  52 #include <linux/vmalloc.h>
  53
  54 #include "rcu.h"
  55
  56 MODULE_LICENSE("GPL");
  57 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>");
  58
  59 #define PERF_FLAG "-perf:"
  60 #define PERFOUT_STRING(s) \
  61         pr_alert("%s" PERF_FLAG " %s\n", perf_type, s)
  62 #define VERBOSE_PERFOUT_STRING(s) \
  63         do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
  64 #define VERBOSE_PERFOUT_ERRSTRING(s) \
  65         do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
  66
  67 /*
  68  * The intended use cases for the nreaders and nwriters module parameters
  69  * are as follows:
  70  *
  71  * 1.   Specify only the nr_cpus kernel boot parameter.  This will
  72  *      set both nreaders and nwriters to the value specified by
  73  *      nr_cpus for a mixed reader/writer test.
  74  *
  75  * 2.   Specify the nr_cpus kernel boot parameter, but set
  76  *      rcuperf.nreaders to zero.  This will set nwriters to the
  77  *      value specified by nr_cpus for an update-only test.
  78  *
  79  * 3.   Specify the nr_cpus kernel boot parameter, but set
  80  *      rcuperf.nwriters to zero.  This will set nreaders to the
  81  *      value specified by nr_cpus for a read-only test.
  82  *
  83  * Various other use cases may of course be specified.
  84  */
  85
  86 torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives");
  87 torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader");
  88 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
  89 torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
  90 torture_param(int, nreaders, -1, "Number of RCU reader threads");
  91 torture_param(int, nwriters, -1, "Number of RCU updater threads");
  92 torture_param(bool, shutdown, !IS_ENABLED(MODULE),
  93               "Shutdown at end of performance tests.");
  94 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
  95 torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
  96
  97 static char *perf_type = "rcu";
  98 module_param(perf_type, charp, 0444);
  99 MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
 100
 101 static int nrealreaders;
 102 static int nrealwriters;
 103 static struct task_struct **writer_tasks;
 104 static struct task_struct **reader_tasks;
 105 static struct task_struct *shutdown_task;
 106
 107 static u64 **writer_durations;
 108 static int *writer_n_durations;
 109 static atomic_t n_rcu_perf_reader_started;
 110 static atomic_t n_rcu_perf_writer_started;
 111 static atomic_t n_rcu_perf_writer_finished;
 112 static wait_queue_head_t shutdown_wq;
 113 static u64 t_rcu_perf_writer_started;
 114 static u64 t_rcu_perf_writer_finished;
 115 static unsigned long b_rcu_perf_writer_started;
 116 static unsigned long b_rcu_perf_writer_finished;
 117 static DEFINE_PER_CPU(atomic_t, n_async_inflight);
 118
 119 static int rcu_perf_writer_state;
 120 #define RTWS_INIT               0
 121 #define RTWS_ASYNC              1
 122 #define RTWS_BARRIER            2
 123 #define RTWS_EXP_SYNC           3
 124 #define RTWS_SYNC               4
 125 #define RTWS_IDLE               5
 126 #define RTWS_STOPPING           6
 127
 128 #define MAX_MEAS 10000
 129 #define MIN_MEAS 100
 130
 131 /*
 132  * Operations vector for selecting different types of tests.
 133  */
 134
 135 struct rcu_perf_ops {
 136         int ptype;
 137         void (*init)(void);
 138         void (*cleanup)(void);
 139         int (*readlock)(void);
 140         void (*readunlock)(int idx);
 141         unsigned long (*get_gp_seq)(void);
 142         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 143         unsigned long (*exp_completed)(void);
 144         void (*async)(struct rcu_head *head, rcu_callback_t func);
 145         void (*gp_barrier)(void);
 146         void (*sync)(void);
 147         void (*exp_sync)(void);
 148         const char *name;
 149 };
 150
 151 static struct rcu_perf_ops *cur_ops;
 152
 153 /*
 154  * Definitions for rcu perf testing.
 155  */
 156
 157 static int rcu_perf_read_lock(void) __acquires(RCU)
 158 {
 159         rcu_read_lock();
 160         return 0;
 161 }
 162
 163 static void rcu_perf_read_unlock(int idx) __releases(RCU)
 164 {
 165         rcu_read_unlock();
 166 }
 167
 168 static unsigned long __maybe_unused rcu_no_completed(void)
 169 {
 170         return 0;
 171 }
 172
 173 static void rcu_sync_perf_init(void)
 174 {
 175 }
 176
 177 static struct rcu_perf_ops rcu_ops = {
 178         .ptype          = RCU_FLAVOR,
 179         .init           = rcu_sync_perf_init,
 180         .readlock       = rcu_perf_read_lock,
 181         .readunlock     = rcu_perf_read_unlock,
 182         .get_gp_seq     = rcu_get_gp_seq,
 183         .gp_diff        = rcu_seq_diff,
 184         .exp_completed  = rcu_exp_batches_completed,
 185         .async          = call_rcu,
 186         .gp_barrier     = rcu_barrier,
 187         .sync           = synchronize_rcu,
 188         .exp_sync       = synchronize_rcu_expedited,
 189         .name           = "rcu"
 190 };
 191
 192 /*
 193  * Definitions for srcu perf testing.
 194  */
 195
 196 DEFINE_STATIC_SRCU(srcu_ctl_perf);
 197 static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
 198
 199 static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
 200 {
 201         return srcu_read_lock(srcu_ctlp);
 202 }
 203
 204 static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
 205 {
 206         srcu_read_unlock(srcu_ctlp, idx);
 207 }
 208
 209 static unsigned long srcu_perf_completed(void)
 210 {
 211         return srcu_batches_completed(srcu_ctlp);
 212 }
 213
 214 static void srcu_call_rcu(struct rcu_head *head, rcu_callback_t func)
 215 {
 216         call_srcu(srcu_ctlp, head, func);
 217 }
 218
 219 static void srcu_rcu_barrier(void)
 220 {
 221         srcu_barrier(srcu_ctlp);
 222 }
 223
 224 static void srcu_perf_synchronize(void)
 225 {
 226         synchronize_srcu(srcu_ctlp);
 227 }
 228
 229 static void srcu_perf_synchronize_expedited(void)
 230 {
 231         synchronize_srcu_expedited(srcu_ctlp);
 232 }
 233
 234 static struct rcu_perf_ops srcu_ops = {
 235         .ptype          = SRCU_FLAVOR,
 236         .init           = rcu_sync_perf_init,
 237         .readlock       = srcu_perf_read_lock,
 238         .readunlock     = srcu_perf_read_unlock,
 239         .get_gp_seq     = srcu_perf_completed,
 240         .gp_diff        = rcu_seq_diff,
 241         .exp_completed  = srcu_perf_completed,
 242         .async          = srcu_call_rcu,
 243         .gp_barrier     = srcu_rcu_barrier,
 244         .sync           = srcu_perf_synchronize,
 245         .exp_sync       = srcu_perf_synchronize_expedited,
 246         .name           = "srcu"
 247 };
 248
 249 static struct srcu_struct srcud;
 250
 251 static void srcu_sync_perf_init(void)
 252 {
 253         srcu_ctlp = &srcud;
 254         init_srcu_struct(srcu_ctlp);
 255 }
 256
 257 static void srcu_sync_perf_cleanup(void)
 258 {
 259         cleanup_srcu_struct(srcu_ctlp);
 260 }
 261
 262 static struct rcu_perf_ops srcud_ops = {
 263         .ptype          = SRCU_FLAVOR,
 264         .init           = srcu_sync_perf_init,
 265         .cleanup        = srcu_sync_perf_cleanup,
 266         .readlock       = srcu_perf_read_lock,
 267         .readunlock     = srcu_perf_read_unlock,
 268         .get_gp_seq     = srcu_perf_completed,
 269         .gp_diff        = rcu_seq_diff,
 270         .exp_completed  = srcu_perf_completed,
 271         .async          = srcu_call_rcu,
 272         .gp_barrier     = srcu_rcu_barrier,
 273         .sync           = srcu_perf_synchronize,
 274         .exp_sync       = srcu_perf_synchronize_expedited,
 275         .name           = "srcud"
 276 };
 277
 278 /*
 279  * Definitions for RCU-tasks perf testing.
 280  */
 281
 282 static int tasks_perf_read_lock(void)
 283 {
 284         return 0;
 285 }
 286
 287 static void tasks_perf_read_unlock(int idx)
 288 {
 289 }
 290
 291 static struct rcu_perf_ops tasks_ops = {
 292         .ptype          = RCU_TASKS_FLAVOR,
 293         .init           = rcu_sync_perf_init,
 294         .readlock       = tasks_perf_read_lock,
 295         .readunlock     = tasks_perf_read_unlock,
 296         .get_gp_seq     = rcu_no_completed,
 297         .gp_diff        = rcu_seq_diff,
 298         .async          = call_rcu_tasks,
 299         .gp_barrier     = rcu_barrier_tasks,
 300         .sync           = synchronize_rcu_tasks,
 301         .exp_sync       = synchronize_rcu_tasks,
 302         .name           = "tasks"
 303 };
 304
 305 static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
 306 {
 307         if (!cur_ops->gp_diff)
 308                 return new - old;
 309         return cur_ops->gp_diff(new, old);
 310 }
 311
 312 /*
 313  * If performance tests complete, wait for shutdown to commence.
 314  */
 315 static void rcu_perf_wait_shutdown(void)
 316 {
 317         cond_resched_tasks_rcu_qs();
 318         if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
 319                 return;
 320         while (!torture_must_stop())
 321                 schedule_timeout_uninterruptible(1);
 322 }
 323
 324 /*
 325  * RCU perf reader kthread.  Repeatedly does empty RCU read-side
 326  * critical section, minimizing update-side interference.
 327  */
 328 static int
 329 rcu_perf_reader(void *arg)
 330 {
 331         unsigned long flags;
 332         int idx;
 333         long me = (long)arg;
 334
 335         VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
 336         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 337         set_user_nice(current, MAX_NICE);
 338         atomic_inc(&n_rcu_perf_reader_started);
 339
 340         do {
 341                 local_irq_save(flags);
 342                 idx = cur_ops->readlock();
 343                 cur_ops->readunlock(idx);
 344                 local_irq_restore(flags);
 345                 rcu_perf_wait_shutdown();
 346         } while (!torture_must_stop());
 347         torture_kthread_stopping("rcu_perf_reader");
 348         return 0;
 349 }
 350
 351 /*
 352  * Callback function for asynchronous grace periods from rcu_perf_writer().
 353  */
 354 static void rcu_perf_async_cb(struct rcu_head *rhp)
 355 {
 356         atomic_dec(this_cpu_ptr(&n_async_inflight));
 357         kfree(rhp);
 358 }
 359
 360 /*
 361  * RCU perf writer kthread.  Repeatedly does a grace period.
 362  */
 363 static int
 364 rcu_perf_writer(void *arg)
 365 {
 366         int i = 0;
 367         int i_max;
 368         long me = (long)arg;
 369         struct rcu_head *rhp = NULL;
 370         struct sched_param sp;
 371         bool started = false, done = false, alldone = false;
 372         u64 t;
 373         u64 *wdp;
 374         u64 *wdpp = writer_durations[me];
 375
 376         VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
 377         WARN_ON(!wdpp);
 378         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 379         sp.sched_priority = 1;
 380         sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
 381
 382         if (holdoff)
 383                 schedule_timeout_uninterruptible(holdoff * HZ);
 384
 385         t = ktime_get_mono_fast_ns();
 386         if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
 387                 t_rcu_perf_writer_started = t;
 388                 if (gp_exp) {
 389                         b_rcu_perf_writer_started =
 390                                 cur_ops->exp_completed() / 2;
 391                 } else {
 392                         b_rcu_perf_writer_started = cur_ops->get_gp_seq();
 393                 }
 394         }
 395
 396         do {
 397                 if (writer_holdoff)
 398                         udelay(writer_holdoff);
 399                 wdp = &wdpp[i];
 400                 *wdp = ktime_get_mono_fast_ns();
 401                 if (gp_async) {
 402 retry:
 403                         if (!rhp)
 404                                 rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
 405                         if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) {
 406                                 rcu_perf_writer_state = RTWS_ASYNC;
 407                                 atomic_inc(this_cpu_ptr(&n_async_inflight));
 408                                 cur_ops->async(rhp, rcu_perf_async_cb);
 409                                 rhp = NULL;
 410                         } else if (!kthread_should_stop()) {
 411                                 rcu_perf_writer_state = RTWS_BARRIER;
 412                                 cur_ops->gp_barrier();
 413                                 goto retry;
 414                         } else {
 415                                 kfree(rhp); /* Because we are stopping. */
 416                         }
 417                 } else if (gp_exp) {
 418                         rcu_perf_writer_state = RTWS_EXP_SYNC;
 419                         cur_ops->exp_sync();
 420                 } else {
 421                         rcu_perf_writer_state = RTWS_SYNC;
 422                         cur_ops->sync();
 423                 }
 424                 rcu_perf_writer_state = RTWS_IDLE;
 425                 t = ktime_get_mono_fast_ns();
 426                 *wdp = t - *wdp;
 427                 i_max = i;
 428                 if (!started &&
 429                     atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
 430                         started = true;
 431                 if (!done && i >= MIN_MEAS) {
 432                         done = true;
 433                         sp.sched_priority = 0;
 434                         sched_setscheduler_nocheck(current,
 435                                                    SCHED_NORMAL, &sp);
 436                         pr_alert("%s%s rcu_perf_writer %ld has %d measurements\n",
 437                                  perf_type, PERF_FLAG, me, MIN_MEAS);
 438                         if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
 439                             nrealwriters) {
 440                                 schedule_timeout_interruptible(10);
 441                                 rcu_ftrace_dump(DUMP_ALL);
 442                                 PERFOUT_STRING("Test complete");
 443                                 t_rcu_perf_writer_finished = t;
 444                                 if (gp_exp) {
 445                                         b_rcu_perf_writer_finished =
 446                                                 cur_ops->exp_completed() / 2;
 447                                 } else {
 448                                         b_rcu_perf_writer_finished =
 449                                                 cur_ops->get_gp_seq();
 450                                 }
 451                                 if (shutdown) {
 452                                         smp_mb(); /* Assign before wake. */
 453                                         wake_up(&shutdown_wq);
 454                                 }
 455                         }
 456                 }
 457                 if (done && !alldone &&
 458                     atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
 459                         alldone = true;
 460                 if (started && !alldone && i < MAX_MEAS - 1)
 461                         i++;
 462                 rcu_perf_wait_shutdown();
 463         } while (!torture_must_stop());
 464         if (gp_async) {
 465                 rcu_perf_writer_state = RTWS_BARRIER;
 466                 cur_ops->gp_barrier();
 467         }
 468         rcu_perf_writer_state = RTWS_STOPPING;
 469         writer_n_durations[me] = i_max;
 470         torture_kthread_stopping("rcu_perf_writer");
 471         return 0;
 472 }
 473
 474 static void
 475 rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
 476 {
 477         pr_alert("%s" PERF_FLAG
 478                  "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
 479                  perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
 480 }
 481
 482 static void
 483 rcu_perf_cleanup(void)
 484 {
 485         int i;
 486         int j;
 487         int ngps = 0;
 488         u64 *wdp;
 489         u64 *wdpp;
 490
 491         /*
 492          * Would like warning at start, but everything is expedited
 493          * during the mid-boot phase, so have to wait till the end.
 494          */
 495         if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp)
 496                 VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
 497         if (rcu_gp_is_normal() && gp_exp)
 498                 VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
 499         if (gp_exp && gp_async)
 500                 VERBOSE_PERFOUT_ERRSTRING("No expedited async GPs, so went with async!");
 501
 502         if (torture_cleanup_begin())
 503                 return;
 504
 505         if (reader_tasks) {
 506                 for (i = 0; i < nrealreaders; i++)
 507                         torture_stop_kthread(rcu_perf_reader,
 508                                              reader_tasks[i]);
 509                 kfree(reader_tasks);
 510         }
 511
 512         if (writer_tasks) {
 513                 for (i = 0; i < nrealwriters; i++) {
 514                         torture_stop_kthread(rcu_perf_writer,
 515                                              writer_tasks[i]);
 516                         if (!writer_n_durations)
 517                                 continue;
 518                         j = writer_n_durations[i];
 519                         pr_alert("%s%s writer %d gps: %d\n",
 520                                  perf_type, PERF_FLAG, i, j);
 521                         ngps += j;
 522                 }
 523                 pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
 524                          perf_type, PERF_FLAG,
 525                          t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
 526                          t_rcu_perf_writer_finished -
 527                          t_rcu_perf_writer_started,
 528                          ngps,
 529                          rcuperf_seq_diff(b_rcu_perf_writer_finished,
 530                                           b_rcu_perf_writer_started));
 531                 for (i = 0; i < nrealwriters; i++) {
 532                         if (!writer_durations)
 533                                 break;
 534                         if (!writer_n_durations)
 535                                 continue;
 536                         wdpp = writer_durations[i];
 537                         if (!wdpp)
 538                                 continue;
 539                         for (j = 0; j <= writer_n_durations[i]; j++) {
 540                                 wdp = &wdpp[j];
 541                                 pr_alert("%s%s %4d writer-duration: %5d %llu\n",
 542                                         perf_type, PERF_FLAG,
 543                                         i, j, *wdp);
 544                                 if (j % 100 == 0)
 545                                         schedule_timeout_uninterruptible(1);
 546                         }
 547                         kfree(writer_durations[i]);
 548                 }
 549                 kfree(writer_tasks);
 550                 kfree(writer_durations);
 551                 kfree(writer_n_durations);
 552         }
 553
 554         /* Do torture-type-specific cleanup operations.  */
 555         if (cur_ops->cleanup != NULL)
 556                 cur_ops->cleanup();
 557
 558         torture_cleanup_end();
 559 }
 560
 561 /*
 562  * Return the number if non-negative.  If -1, the number of CPUs.
 563  * If less than -1, that much less than the number of CPUs, but
 564  * at least one.
 565  */
 566 static int compute_real(int n)
 567 {
 568         int nr;
 569
 570         if (n >= 0) {
 571                 nr = n;
 572         } else {
 573                 nr = num_online_cpus() + 1 + n;
 574                 if (nr <= 0)
 575                         nr = 1;
 576         }
 577         return nr;
 578 }
 579
 580 /*
 581  * RCU perf shutdown kthread.  Just waits to be awakened, then shuts
 582  * down system.
 583  */
 584 static int
 585 rcu_perf_shutdown(void *arg)
 586 {
 587         do {
 588                 wait_event(shutdown_wq,
 589                            atomic_read(&n_rcu_perf_writer_finished) >=
 590                            nrealwriters);
 591         } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
 592         smp_mb(); /* Wake before output. */
 593         rcu_perf_cleanup();
 594         kernel_power_off();
 595         return -EINVAL;
 596 }
 597
 598 static int __init
 599 rcu_perf_init(void)
 600 {
 601         long i;
 602         int firsterr = 0;
 603         static struct rcu_perf_ops *perf_ops[] = {
 604                 &rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops,
 605         };
 606
 607         if (!torture_init_begin(perf_type, verbose))
 608                 return -EBUSY;
 609
 610         /* Process args and tell the world that the perf'er is on the job. */
 611         for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
 612                 cur_ops = perf_ops[i];
 613                 if (strcmp(perf_type, cur_ops->name) == 0)
 614                         break;
 615         }
 616         if (i == ARRAY_SIZE(perf_ops)) {
 617                 pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type);
 618                 pr_alert("rcu-perf types:");
 619                 for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
 620                         pr_cont(" %s", perf_ops[i]->name);
 621                 pr_cont("\n");
 622                 WARN_ON(!IS_MODULE(CONFIG_RCU_PERF_TEST));
 623                 firsterr = -EINVAL;
 624                 goto unwind;
 625         }
 626         if (cur_ops->init)
 627                 cur_ops->init();
 628
 629         nrealwriters = compute_real(nwriters);
 630         nrealreaders = compute_real(nreaders);
 631         atomic_set(&n_rcu_perf_reader_started, 0);
 632         atomic_set(&n_rcu_perf_writer_started, 0);
 633         atomic_set(&n_rcu_perf_writer_finished, 0);
 634         rcu_perf_print_module_parms(cur_ops, "Start of test");
 635
 636         /* Start up the kthreads. */
 637
 638         if (shutdown) {
 639                 init_waitqueue_head(&shutdown_wq);
 640                 firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
 641                                                   shutdown_task);
 642                 if (firsterr)
 643                         goto unwind;
 644                 schedule_timeout_uninterruptible(1);
 645         }
 646         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
 647                                GFP_KERNEL);
 648         if (reader_tasks == NULL) {
 649                 VERBOSE_PERFOUT_ERRSTRING("out of memory");
 650                 firsterr = -ENOMEM;
 651                 goto unwind;
 652         }
 653         for (i = 0; i < nrealreaders; i++) {
 654                 firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
 655                                                   reader_tasks[i]);
 656                 if (firsterr)
 657                         goto unwind;
 658         }
 659         while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
 660                 schedule_timeout_uninterruptible(1);
 661         writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
 662                                GFP_KERNEL);
 663         writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
 664                                    GFP_KERNEL);
 665         writer_n_durations =
 666                 kcalloc(nrealwriters, sizeof(*writer_n_durations),
 667                         GFP_KERNEL);
 668         if (!writer_tasks || !writer_durations || !writer_n_durations) {
 669                 VERBOSE_PERFOUT_ERRSTRING("out of memory");
 670                 firsterr = -ENOMEM;
 671                 goto unwind;
 672         }
 673         for (i = 0; i < nrealwriters; i++) {
 674                 writer_durations[i] =
 675                         kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
 676                                 GFP_KERNEL);
 677                 if (!writer_durations[i]) {
 678                         firsterr = -ENOMEM;
 679                         goto unwind;
 680                 }
 681                 firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
 682                                                   writer_tasks[i]);
 683                 if (firsterr)
 684                         goto unwind;
 685         }
 686         torture_init_end();
 687         return 0;
 688
 689 unwind:
 690         torture_init_end();
 691         rcu_perf_cleanup();
 692         return firsterr;
 693 }
 694
 695 module_init(rcu_perf_init);
 696 module_exit(rcu_perf_cleanup);