kernel/rcu/rcuscale.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Read-Copy Update module-based scalability-test facility
   4  *
   5  * Copyright (C) IBM Corporation, 2015
   6  *
   7  * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
   8  */
   9
  10 #define pr_fmt(fmt) fmt
  11
  12 #include <linux/types.h>
  13 #include <linux/kernel.h>
  14 #include <linux/init.h>
  15 #include <linux/mm.h>
  16 #include <linux/module.h>
  17 #include <linux/kthread.h>
  18 #include <linux/err.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/smp.h>
  21 #include <linux/rcupdate.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/sched.h>
  24 #include <uapi/linux/sched/types.h>
  25 #include <linux/atomic.h>
  26 #include <linux/bitops.h>
  27 #include <linux/completion.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/percpu.h>
  30 #include <linux/notifier.h>
  31 #include <linux/reboot.h>
  32 #include <linux/freezer.h>
  33 #include <linux/cpu.h>
  34 #include <linux/delay.h>
  35 #include <linux/stat.h>
  36 #include <linux/srcu.h>
  37 #include <linux/slab.h>
  38 #include <asm/byteorder.h>
  39 #include <linux/torture.h>
  40 #include <linux/vmalloc.h>
  41 #include <linux/rcupdate_trace.h>
  42 #include <linux/sched/debug.h>
  43
  44 #include "rcu.h"
  45
  46 MODULE_DESCRIPTION("Read-Copy Update module-based scalability-test facility");
  47 MODULE_LICENSE("GPL");
  48 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
  49
  50 #define SCALE_FLAG "-scale:"
  51 #define SCALEOUT_STRING(s) \
  52         pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s)
  53 #define VERBOSE_SCALEOUT_STRING(s) \
  54         do { if (verbose) pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s); } while (0)
  55 #define SCALEOUT_ERRSTRING(s) \
  56         pr_alert("%s" SCALE_FLAG "!!! %s\n", scale_type, s)
  57
  58 /*
  59  * The intended use cases for the nreaders and nwriters module parameters
  60  * are as follows:
  61  *
  62  * 1.   Specify only the nr_cpus kernel boot parameter.  This will
  63  *      set both nreaders and nwriters to the value specified by
  64  *      nr_cpus for a mixed reader/writer test.
  65  *
  66  * 2.   Specify the nr_cpus kernel boot parameter, but set
  67  *      rcuscale.nreaders to zero.  This will set nwriters to the
  68  *      value specified by nr_cpus for an update-only test.
  69  *
  70  * 3.   Specify the nr_cpus kernel boot parameter, but set
  71  *      rcuscale.nwriters to zero.  This will set nreaders to the
  72  *      value specified by nr_cpus for a read-only test.
  73  *
  74  * Various other use cases may of course be specified.
  75  *
  76  * Note that this test's readers are intended only as a test load for
  77  * the writers.  The reader scalability statistics will be overly
  78  * pessimistic due to the per-critical-section interrupt disabling,
  79  * test-end checks, and the pair of calls through pointers.
  80  */
  81
  82 #ifdef MODULE
  83 # define RCUSCALE_SHUTDOWN 0
  84 #else
  85 # define RCUSCALE_SHUTDOWN 1
  86 #endif
  87
  88 torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives");
  89 torture_param(int, gp_async_max, 1000, "Max # outstanding waits per writer");
  90 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
  91 torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
  92 torture_param(int, minruntime, 0, "Minimum run time (s)");
  93 torture_param(int, nreaders, -1, "Number of RCU reader threads");
  94 torture_param(int, nwriters, -1, "Number of RCU updater threads");
  95 torture_param(bool, shutdown, RCUSCALE_SHUTDOWN,
  96               "Shutdown at end of scalability tests.");
  97 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
  98 torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
  99 torture_param(int, writer_holdoff_jiffies, 0, "Holdoff (jiffies) between GPs, zero to disable");
 100 torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?");
 101 torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
 102 torture_param(int, kfree_by_call_rcu, 0, "Use call_rcu() to emulate kfree_rcu()?");
 103
 104 static char *scale_type = "rcu";
 105 module_param(scale_type, charp, 0444);
 106 MODULE_PARM_DESC(scale_type, "Type of RCU to scalability-test (rcu, srcu, ...)");
 107
 108 // Structure definitions for custom fixed-per-task allocator.
 109 struct writer_mblock {
 110         struct rcu_head wmb_rh;
 111         struct llist_node wmb_node;
 112         struct writer_freelist *wmb_wfl;
 113 };
 114
 115 struct writer_freelist {
 116         struct llist_head ws_lhg;
 117         atomic_t ws_inflight;
 118         struct llist_head ____cacheline_internodealigned_in_smp ws_lhp;
 119         struct writer_mblock *ws_mblocks;
 120 };
 121
 122 static int nrealreaders;
 123 static int nrealwriters;
 124 static struct task_struct **writer_tasks;
 125 static struct task_struct **reader_tasks;
 126 static struct task_struct *shutdown_task;
 127
 128 static u64 **writer_durations;
 129 static bool *writer_done;
 130 static struct writer_freelist *writer_freelists;
 131 static int *writer_n_durations;
 132 static atomic_t n_rcu_scale_reader_started;
 133 static atomic_t n_rcu_scale_writer_started;
 134 static atomic_t n_rcu_scale_writer_finished;
 135 static wait_queue_head_t shutdown_wq;
 136 static u64 t_rcu_scale_writer_started;
 137 static u64 t_rcu_scale_writer_finished;
 138 static unsigned long b_rcu_gp_test_started;
 139 static unsigned long b_rcu_gp_test_finished;
 140
 141 #define MAX_MEAS 10000
 142 #define MIN_MEAS 100
 143
 144 /*
 145  * Operations vector for selecting different types of tests.
 146  */
 147
 148 struct rcu_scale_ops {
 149         int ptype;
 150         void (*init)(void);
 151         void (*cleanup)(void);
 152         int (*readlock)(void);
 153         void (*readunlock)(int idx);
 154         unsigned long (*get_gp_seq)(void);
 155         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 156         unsigned long (*exp_completed)(void);
 157         void (*async)(struct rcu_head *head, rcu_callback_t func);
 158         void (*gp_barrier)(void);
 159         void (*sync)(void);
 160         void (*exp_sync)(void);
 161         struct task_struct *(*rso_gp_kthread)(void);
 162         void (*stats)(void);
 163         const char *name;
 164 };
 165
 166 static struct rcu_scale_ops *cur_ops;
 167
 168 /*
 169  * Definitions for rcu scalability testing.
 170  */
 171
 172 static int rcu_scale_read_lock(void) __acquires(RCU)
 173 {
 174         rcu_read_lock();
 175         return 0;
 176 }
 177
 178 static void rcu_scale_read_unlock(int idx) __releases(RCU)
 179 {
 180         rcu_read_unlock();
 181 }
 182
 183 static unsigned long __maybe_unused rcu_no_completed(void)
 184 {
 185         return 0;
 186 }
 187
 188 static void rcu_sync_scale_init(void)
 189 {
 190 }
 191
 192 static struct rcu_scale_ops rcu_ops = {
 193         .ptype          = RCU_FLAVOR,
 194         .init           = rcu_sync_scale_init,
 195         .readlock       = rcu_scale_read_lock,
 196         .readunlock     = rcu_scale_read_unlock,
 197         .get_gp_seq     = rcu_get_gp_seq,
 198         .gp_diff        = rcu_seq_diff,
 199         .exp_completed  = rcu_exp_batches_completed,
 200         .async          = call_rcu_hurry,
 201         .gp_barrier     = rcu_barrier,
 202         .sync           = synchronize_rcu,
 203         .exp_sync       = synchronize_rcu_expedited,
 204         .name           = "rcu"
 205 };
 206
 207 /*
 208  * Definitions for srcu scalability testing.
 209  */
 210
 211 DEFINE_STATIC_SRCU(srcu_ctl_scale);
 212 static struct srcu_struct *srcu_ctlp = &srcu_ctl_scale;
 213
 214 static int srcu_scale_read_lock(void) __acquires(srcu_ctlp)
 215 {
 216         return srcu_read_lock(srcu_ctlp);
 217 }
 218
 219 static void srcu_scale_read_unlock(int idx) __releases(srcu_ctlp)
 220 {
 221         srcu_read_unlock(srcu_ctlp, idx);
 222 }
 223
 224 static unsigned long srcu_scale_completed(void)
 225 {
 226         return srcu_batches_completed(srcu_ctlp);
 227 }
 228
 229 static void srcu_call_rcu(struct rcu_head *head, rcu_callback_t func)
 230 {
 231         call_srcu(srcu_ctlp, head, func);
 232 }
 233
 234 static void srcu_rcu_barrier(void)
 235 {
 236         srcu_barrier(srcu_ctlp);
 237 }
 238
 239 static void srcu_scale_synchronize(void)
 240 {
 241         synchronize_srcu(srcu_ctlp);
 242 }
 243
 244 static void srcu_scale_stats(void)
 245 {
 246         srcu_torture_stats_print(srcu_ctlp, scale_type, SCALE_FLAG);
 247 }
 248
 249 static void srcu_scale_synchronize_expedited(void)
 250 {
 251         synchronize_srcu_expedited(srcu_ctlp);
 252 }
 253
 254 static struct rcu_scale_ops srcu_ops = {
 255         .ptype          = SRCU_FLAVOR,
 256         .init           = rcu_sync_scale_init,
 257         .readlock       = srcu_scale_read_lock,
 258         .readunlock     = srcu_scale_read_unlock,
 259         .get_gp_seq     = srcu_scale_completed,
 260         .gp_diff        = rcu_seq_diff,
 261         .exp_completed  = srcu_scale_completed,
 262         .async          = srcu_call_rcu,
 263         .gp_barrier     = srcu_rcu_barrier,
 264         .sync           = srcu_scale_synchronize,
 265         .exp_sync       = srcu_scale_synchronize_expedited,
 266         .stats          = srcu_scale_stats,
 267         .name           = "srcu"
 268 };
 269
 270 static struct srcu_struct srcud;
 271
 272 static void srcu_sync_scale_init(void)
 273 {
 274         srcu_ctlp = &srcud;
 275         init_srcu_struct(srcu_ctlp);
 276 }
 277
 278 static void srcu_sync_scale_cleanup(void)
 279 {
 280         cleanup_srcu_struct(srcu_ctlp);
 281 }
 282
 283 static struct rcu_scale_ops srcud_ops = {
 284         .ptype          = SRCU_FLAVOR,
 285         .init           = srcu_sync_scale_init,
 286         .cleanup        = srcu_sync_scale_cleanup,
 287         .readlock       = srcu_scale_read_lock,
 288         .readunlock     = srcu_scale_read_unlock,
 289         .get_gp_seq     = srcu_scale_completed,
 290         .gp_diff        = rcu_seq_diff,
 291         .exp_completed  = srcu_scale_completed,
 292         .async          = srcu_call_rcu,
 293         .gp_barrier     = srcu_rcu_barrier,
 294         .sync           = srcu_scale_synchronize,
 295         .exp_sync       = srcu_scale_synchronize_expedited,
 296         .stats          = srcu_scale_stats,
 297         .name           = "srcud"
 298 };
 299
 300 #ifdef CONFIG_TASKS_RCU
 301
 302 /*
 303  * Definitions for RCU-tasks scalability testing.
 304  */
 305
 306 static int tasks_scale_read_lock(void)
 307 {
 308         return 0;
 309 }
 310
 311 static void tasks_scale_read_unlock(int idx)
 312 {
 313 }
 314
 315 static void rcu_tasks_scale_stats(void)
 316 {
 317         rcu_tasks_torture_stats_print(scale_type, SCALE_FLAG);
 318 }
 319
 320 static struct rcu_scale_ops tasks_ops = {
 321         .ptype          = RCU_TASKS_FLAVOR,
 322         .init           = rcu_sync_scale_init,
 323         .readlock       = tasks_scale_read_lock,
 324         .readunlock     = tasks_scale_read_unlock,
 325         .get_gp_seq     = rcu_no_completed,
 326         .gp_diff        = rcu_seq_diff,
 327         .async          = call_rcu_tasks,
 328         .gp_barrier     = rcu_barrier_tasks,
 329         .sync           = synchronize_rcu_tasks,
 330         .exp_sync       = synchronize_rcu_tasks,
 331         .rso_gp_kthread = get_rcu_tasks_gp_kthread,
 332         .stats          = IS_ENABLED(CONFIG_TINY_RCU) ? NULL : rcu_tasks_scale_stats,
 333         .name           = "tasks"
 334 };
 335
 336 #define TASKS_OPS &tasks_ops,
 337
 338 #else // #ifdef CONFIG_TASKS_RCU
 339
 340 #define TASKS_OPS
 341
 342 #endif // #else // #ifdef CONFIG_TASKS_RCU
 343
 344 #ifdef CONFIG_TASKS_RUDE_RCU
 345
 346 /*
 347  * Definitions for RCU-tasks-rude scalability testing.
 348  */
 349
 350 static int tasks_rude_scale_read_lock(void)
 351 {
 352         return 0;
 353 }
 354
 355 static void tasks_rude_scale_read_unlock(int idx)
 356 {
 357 }
 358
 359 static void rcu_tasks_rude_scale_stats(void)
 360 {
 361         rcu_tasks_rude_torture_stats_print(scale_type, SCALE_FLAG);
 362 }
 363
 364 static struct rcu_scale_ops tasks_rude_ops = {
 365         .ptype          = RCU_TASKS_RUDE_FLAVOR,
 366         .init           = rcu_sync_scale_init,
 367         .readlock       = tasks_rude_scale_read_lock,
 368         .readunlock     = tasks_rude_scale_read_unlock,
 369         .get_gp_seq     = rcu_no_completed,
 370         .gp_diff        = rcu_seq_diff,
 371         .sync           = synchronize_rcu_tasks_rude,
 372         .exp_sync       = synchronize_rcu_tasks_rude,
 373         .rso_gp_kthread = get_rcu_tasks_rude_gp_kthread,
 374         .stats          = IS_ENABLED(CONFIG_TINY_RCU) ? NULL : rcu_tasks_rude_scale_stats,
 375         .name           = "tasks-rude"
 376 };
 377
 378 #define TASKS_RUDE_OPS &tasks_rude_ops,
 379
 380 #else // #ifdef CONFIG_TASKS_RUDE_RCU
 381
 382 #define TASKS_RUDE_OPS
 383
 384 #endif // #else // #ifdef CONFIG_TASKS_RUDE_RCU
 385
 386 #ifdef CONFIG_TASKS_TRACE_RCU
 387
 388 /*
 389  * Definitions for RCU-tasks-trace scalability testing.
 390  */
 391
 392 static int tasks_trace_scale_read_lock(void)
 393 {
 394         rcu_read_lock_trace();
 395         return 0;
 396 }
 397
 398 static void tasks_trace_scale_read_unlock(int idx)
 399 {
 400         rcu_read_unlock_trace();
 401 }
 402
 403 static void rcu_tasks_trace_scale_stats(void)
 404 {
 405         rcu_tasks_trace_torture_stats_print(scale_type, SCALE_FLAG);
 406 }
 407
 408 static struct rcu_scale_ops tasks_tracing_ops = {
 409         .ptype          = RCU_TASKS_FLAVOR,
 410         .init           = rcu_sync_scale_init,
 411         .readlock       = tasks_trace_scale_read_lock,
 412         .readunlock     = tasks_trace_scale_read_unlock,
 413         .get_gp_seq     = rcu_no_completed,
 414         .gp_diff        = rcu_seq_diff,
 415         .async          = call_rcu_tasks_trace,
 416         .gp_barrier     = rcu_barrier_tasks_trace,
 417         .sync           = synchronize_rcu_tasks_trace,
 418         .exp_sync       = synchronize_rcu_tasks_trace,
 419         .rso_gp_kthread = get_rcu_tasks_trace_gp_kthread,
 420         .stats          = IS_ENABLED(CONFIG_TINY_RCU) ? NULL : rcu_tasks_trace_scale_stats,
 421         .name           = "tasks-tracing"
 422 };
 423
 424 #define TASKS_TRACING_OPS &tasks_tracing_ops,
 425
 426 #else // #ifdef CONFIG_TASKS_TRACE_RCU
 427
 428 #define TASKS_TRACING_OPS
 429
 430 #endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU
 431
 432 static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
 433 {
 434         if (!cur_ops->gp_diff)
 435                 return new - old;
 436         return cur_ops->gp_diff(new, old);
 437 }
 438
 439 /*
 440  * If scalability tests complete, wait for shutdown to commence.
 441  */
 442 static void rcu_scale_wait_shutdown(void)
 443 {
 444         cond_resched_tasks_rcu_qs();
 445         if (atomic_read(&n_rcu_scale_writer_finished) < nrealwriters)
 446                 return;
 447         while (!torture_must_stop())
 448                 schedule_timeout_uninterruptible(1);
 449 }
 450
 451 /*
 452  * RCU scalability reader kthread.  Repeatedly does empty RCU read-side
 453  * critical section, minimizing update-side interference.  However, the
 454  * point of this test is not to evaluate reader scalability, but instead
 455  * to serve as a test load for update-side scalability testing.
 456  */
 457 static int
 458 rcu_scale_reader(void *arg)
 459 {
 460         unsigned long flags;
 461         int idx;
 462         long me = (long)arg;
 463
 464         VERBOSE_SCALEOUT_STRING("rcu_scale_reader task started");
 465         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 466         set_user_nice(current, MAX_NICE);
 467         atomic_inc(&n_rcu_scale_reader_started);
 468
 469         do {
 470                 local_irq_save(flags);
 471                 idx = cur_ops->readlock();
 472                 cur_ops->readunlock(idx);
 473                 local_irq_restore(flags);
 474                 rcu_scale_wait_shutdown();
 475         } while (!torture_must_stop());
 476         torture_kthread_stopping("rcu_scale_reader");
 477         return 0;
 478 }
 479
 480 /*
 481  * Allocate a writer_mblock structure for the specified rcu_scale_writer
 482  * task.
 483  */
 484 static struct writer_mblock *rcu_scale_alloc(long me)
 485 {
 486         struct llist_node *llnp;
 487         struct writer_freelist *wflp;
 488         struct writer_mblock *wmbp;
 489
 490         if (WARN_ON_ONCE(!writer_freelists))
 491                 return NULL;
 492         wflp = &writer_freelists[me];
 493         if (llist_empty(&wflp->ws_lhp)) {
 494                 // ->ws_lhp is private to its rcu_scale_writer task.
 495                 wmbp = container_of(llist_del_all(&wflp->ws_lhg), struct writer_mblock, wmb_node);
 496                 wflp->ws_lhp.first = &wmbp->wmb_node;
 497         }
 498         llnp = llist_del_first(&wflp->ws_lhp);
 499         if (!llnp)
 500                 return NULL;
 501         return container_of(llnp, struct writer_mblock, wmb_node);
 502 }
 503
 504 /*
 505  * Free a writer_mblock structure to its rcu_scale_writer task.
 506  */
 507 static void rcu_scale_free(struct writer_mblock *wmbp)
 508 {
 509         struct writer_freelist *wflp;
 510
 511         if (!wmbp)
 512                 return;
 513         wflp = wmbp->wmb_wfl;
 514         llist_add(&wmbp->wmb_node, &wflp->ws_lhg);
 515 }
 516
 517 /*
 518  * Callback function for asynchronous grace periods from rcu_scale_writer().
 519  */
 520 static void rcu_scale_async_cb(struct rcu_head *rhp)
 521 {
 522         struct writer_mblock *wmbp = container_of(rhp, struct writer_mblock, wmb_rh);
 523         struct writer_freelist *wflp = wmbp->wmb_wfl;
 524
 525         atomic_dec(&wflp->ws_inflight);
 526         rcu_scale_free(wmbp);
 527 }
 528
 529 /*
 530  * RCU scale writer kthread.  Repeatedly does a grace period.
 531  */
 532 static int
 533 rcu_scale_writer(void *arg)
 534 {
 535         int i = 0;
 536         int i_max;
 537         unsigned long jdone;
 538         long me = (long)arg;
 539         bool selfreport = false;
 540         bool started = false, done = false, alldone = false;
 541         u64 t;
 542         DEFINE_TORTURE_RANDOM(tr);
 543         u64 *wdp;
 544         u64 *wdpp = writer_durations[me];
 545         struct writer_freelist *wflp = &writer_freelists[me];
 546         struct writer_mblock *wmbp = NULL;
 547
 548         VERBOSE_SCALEOUT_STRING("rcu_scale_writer task started");
 549         WARN_ON(!wdpp);
 550         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 551         current->flags |= PF_NO_SETAFFINITY;
 552         sched_set_fifo_low(current);
 553
 554         if (holdoff)
 555                 schedule_timeout_idle(holdoff * HZ);
 556
 557         /*
 558          * Wait until rcu_end_inkernel_boot() is called for normal GP tests
 559          * so that RCU is not always expedited for normal GP tests.
 560          * The system_state test is approximate, but works well in practice.
 561          */
 562         while (!gp_exp && system_state != SYSTEM_RUNNING)
 563                 schedule_timeout_uninterruptible(1);
 564
 565         t = ktime_get_mono_fast_ns();
 566         if (atomic_inc_return(&n_rcu_scale_writer_started) >= nrealwriters) {
 567                 t_rcu_scale_writer_started = t;
 568                 if (gp_exp) {
 569                         b_rcu_gp_test_started =
 570                                 cur_ops->exp_completed() / 2;
 571                 } else {
 572                         b_rcu_gp_test_started = cur_ops->get_gp_seq();
 573                 }
 574         }
 575
 576         jdone = jiffies + minruntime * HZ;
 577         do {
 578                 bool gp_succeeded = false;
 579
 580                 if (writer_holdoff)
 581                         udelay(writer_holdoff);
 582                 if (writer_holdoff_jiffies)
 583                         schedule_timeout_idle(torture_random(&tr) % writer_holdoff_jiffies + 1);
 584                 wdp = &wdpp[i];
 585                 *wdp = ktime_get_mono_fast_ns();
 586                 if (gp_async && !WARN_ON_ONCE(!cur_ops->async)) {
 587                         if (!wmbp)
 588                                 wmbp = rcu_scale_alloc(me);
 589                         if (wmbp && atomic_read(&wflp->ws_inflight) < gp_async_max) {
 590                                 atomic_inc(&wflp->ws_inflight);
 591                                 cur_ops->async(&wmbp->wmb_rh, rcu_scale_async_cb);
 592                                 wmbp = NULL;
 593                                 gp_succeeded = true;
 594                         } else if (!kthread_should_stop()) {
 595                                 cur_ops->gp_barrier();
 596                         } else {
 597                                 rcu_scale_free(wmbp); /* Because we are stopping. */
 598                                 wmbp = NULL;
 599                         }
 600                 } else if (gp_exp) {
 601                         cur_ops->exp_sync();
 602                         gp_succeeded = true;
 603                 } else {
 604                         cur_ops->sync();
 605                         gp_succeeded = true;
 606                 }
 607                 t = ktime_get_mono_fast_ns();
 608                 *wdp = t - *wdp;
 609                 i_max = i;
 610                 if (!started &&
 611                     atomic_read(&n_rcu_scale_writer_started) >= nrealwriters)
 612                         started = true;
 613                 if (!done && i >= MIN_MEAS && time_after(jiffies, jdone)) {
 614                         done = true;
 615                         WRITE_ONCE(writer_done[me], true);
 616                         sched_set_normal(current, 0);
 617                         pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n",
 618                                  scale_type, SCALE_FLAG, me, MIN_MEAS);
 619                         if (atomic_inc_return(&n_rcu_scale_writer_finished) >=
 620                             nrealwriters) {
 621                                 schedule_timeout_interruptible(10);
 622                                 rcu_ftrace_dump(DUMP_ALL);
 623                                 SCALEOUT_STRING("Test complete");
 624                                 t_rcu_scale_writer_finished = t;
 625                                 if (gp_exp) {
 626                                         b_rcu_gp_test_finished =
 627                                                 cur_ops->exp_completed() / 2;
 628                                 } else {
 629                                         b_rcu_gp_test_finished =
 630                                                 cur_ops->get_gp_seq();
 631                                 }
 632                                 if (shutdown) {
 633                                         smp_mb(); /* Assign before wake. */
 634                                         wake_up(&shutdown_wq);
 635                                 }
 636                         }
 637                 }
 638                 if (done && !alldone &&
 639                     atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters)
 640                         alldone = true;
 641                 if (done && !alldone && time_after(jiffies, jdone + HZ * 60)) {
 642                         static atomic_t dumped;
 643                         int i;
 644
 645                         if (!atomic_xchg(&dumped, 1)) {
 646                                 for (i = 0; i < nrealwriters; i++) {
 647                                         if (writer_done[i])
 648                                                 continue;
 649                                         pr_info("%s: Task %ld flags writer %d:\n", __func__, me, i);
 650                                         sched_show_task(writer_tasks[i]);
 651                                 }
 652                                 if (cur_ops->stats)
 653                                         cur_ops->stats();
 654                         }
 655                 }
 656                 if (!selfreport && time_after(jiffies, jdone + HZ * (70 + me))) {
 657                         pr_info("%s: Writer %ld self-report: started %d done %d/%d->%d i %d jdone %lu.\n",
 658                                 __func__, me, started, done, writer_done[me], atomic_read(&n_rcu_scale_writer_finished), i, jiffies - jdone);
 659                         selfreport = true;
 660                 }
 661                 if (gp_succeeded && started && !alldone && i < MAX_MEAS - 1)
 662                         i++;
 663                 rcu_scale_wait_shutdown();
 664         } while (!torture_must_stop());
 665         if (gp_async && cur_ops->async) {
 666                 rcu_scale_free(wmbp);
 667                 cur_ops->gp_barrier();
 668         }
 669         writer_n_durations[me] = i_max + 1;
 670         torture_kthread_stopping("rcu_scale_writer");
 671         return 0;
 672 }
 673
 674 static void
 675 rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
 676 {
 677         pr_alert("%s" SCALE_FLAG
 678                  "--- %s: gp_async=%d gp_async_max=%d gp_exp=%d holdoff=%d minruntime=%d nreaders=%d nwriters=%d writer_holdoff=%d writer_holdoff_jiffies=%d verbose=%d shutdown=%d\n",
 679                  scale_type, tag, gp_async, gp_async_max, gp_exp, holdoff, minruntime, nrealreaders, nrealwriters, writer_holdoff, writer_holdoff_jiffies, verbose, shutdown);
 680 }
 681
 682 /*
 683  * Return the number if non-negative.  If -1, the number of CPUs.
 684  * If less than -1, that much less than the number of CPUs, but
 685  * at least one.
 686  */
 687 static int compute_real(int n)
 688 {
 689         int nr;
 690
 691         if (n >= 0) {
 692                 nr = n;
 693         } else {
 694                 nr = num_online_cpus() + 1 + n;
 695                 if (nr <= 0)
 696                         nr = 1;
 697         }
 698         return nr;
 699 }
 700
 701 /*
 702  * kfree_rcu() scalability tests: Start a kfree_rcu() loop on all CPUs for number
 703  * of iterations and measure total time and number of GP for all iterations to complete.
 704  */
 705
 706 torture_param(int, kfree_nthreads, -1, "Number of threads running loops of kfree_rcu().");
 707 torture_param(int, kfree_alloc_num, 8000, "Number of allocations and frees done in an iteration.");
 708 torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num allocations and frees.");
 709 torture_param(bool, kfree_rcu_test_double, false, "Do we run a kfree_rcu() double-argument scale test?");
 710 torture_param(bool, kfree_rcu_test_single, false, "Do we run a kfree_rcu() single-argument scale test?");
 711
 712 static struct task_struct **kfree_reader_tasks;
 713 static int kfree_nrealthreads;
 714 static atomic_t n_kfree_scale_thread_started;
 715 static atomic_t n_kfree_scale_thread_ended;
 716 static struct task_struct *kthread_tp;
 717 static u64 kthread_stime;
 718
 719 struct kfree_obj {
 720         char kfree_obj[8];
 721         struct rcu_head rh;
 722 };
 723
 724 /* Used if doing RCU-kfree'ing via call_rcu(). */
 725 static void kfree_call_rcu(struct rcu_head *rh)
 726 {
 727         struct kfree_obj *obj = container_of(rh, struct kfree_obj, rh);
 728
 729         kfree(obj);
 730 }
 731
 732 static int
 733 kfree_scale_thread(void *arg)
 734 {
 735         int i, loop = 0;
 736         long me = (long)arg;
 737         struct kfree_obj *alloc_ptr;
 738         u64 start_time, end_time;
 739         long long mem_begin, mem_during = 0;
 740         bool kfree_rcu_test_both;
 741         DEFINE_TORTURE_RANDOM(tr);
 742
 743         VERBOSE_SCALEOUT_STRING("kfree_scale_thread task started");
 744         set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 745         set_user_nice(current, MAX_NICE);
 746         kfree_rcu_test_both = (kfree_rcu_test_single == kfree_rcu_test_double);
 747
 748         start_time = ktime_get_mono_fast_ns();
 749
 750         if (atomic_inc_return(&n_kfree_scale_thread_started) >= kfree_nrealthreads) {
 751                 if (gp_exp)
 752                         b_rcu_gp_test_started = cur_ops->exp_completed() / 2;
 753                 else
 754                         b_rcu_gp_test_started = cur_ops->get_gp_seq();
 755         }
 756
 757         do {
 758                 if (!mem_during) {
 759                         mem_during = mem_begin = si_mem_available();
 760                 } else if (loop % (kfree_loops / 4) == 0) {
 761                         mem_during = (mem_during + si_mem_available()) / 2;
 762                 }
 763
 764                 for (i = 0; i < kfree_alloc_num; i++) {
 765                         alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
 766                         if (!alloc_ptr)
 767                                 return -ENOMEM;
 768
 769                         if (kfree_by_call_rcu) {
 770                                 call_rcu(&(alloc_ptr->rh), kfree_call_rcu);
 771                                 continue;
 772                         }
 773
 774                         // By default kfree_rcu_test_single and kfree_rcu_test_double are
 775                         // initialized to false. If both have the same value (false or true)
 776                         // both are randomly tested, otherwise only the one with value true
 777                         // is tested.
 778                         if ((kfree_rcu_test_single && !kfree_rcu_test_double) ||
 779                                         (kfree_rcu_test_both && torture_random(&tr) & 0x800))
 780                                 kfree_rcu_mightsleep(alloc_ptr);
 781                         else
 782                                 kfree_rcu(alloc_ptr, rh);
 783                 }
 784
 785                 cond_resched();
 786         } while (!torture_must_stop() && ++loop < kfree_loops);
 787
 788         if (atomic_inc_return(&n_kfree_scale_thread_ended) >= kfree_nrealthreads) {
 789                 end_time = ktime_get_mono_fast_ns();
 790
 791                 if (gp_exp)
 792                         b_rcu_gp_test_finished = cur_ops->exp_completed() / 2;
 793                 else
 794                         b_rcu_gp_test_finished = cur_ops->get_gp_seq();
 795
 796                 pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
 797                        (unsigned long long)(end_time - start_time), kfree_loops,
 798                        rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
 799                        (mem_begin - mem_during) >> (20 - PAGE_SHIFT));
 800
 801                 if (shutdown) {
 802                         smp_mb(); /* Assign before wake. */
 803                         wake_up(&shutdown_wq);
 804                 }
 805         }
 806
 807         torture_kthread_stopping("kfree_scale_thread");
 808         return 0;
 809 }
 810
 811 static void
 812 kfree_scale_cleanup(void)
 813 {
 814         int i;
 815
 816         if (torture_cleanup_begin())
 817                 return;
 818
 819         if (kfree_reader_tasks) {
 820                 for (i = 0; i < kfree_nrealthreads; i++)
 821                         torture_stop_kthread(kfree_scale_thread,
 822                                              kfree_reader_tasks[i]);
 823                 kfree(kfree_reader_tasks);
 824                 kfree_reader_tasks = NULL;
 825         }
 826
 827         torture_cleanup_end();
 828 }
 829
 830 /*
 831  * shutdown kthread.  Just waits to be awakened, then shuts down system.
 832  */
 833 static int
 834 kfree_scale_shutdown(void *arg)
 835 {
 836         wait_event_idle(shutdown_wq,
 837                         atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
 838
 839         smp_mb(); /* Wake before output. */
 840
 841         kfree_scale_cleanup();
 842         kernel_power_off();
 843         return -EINVAL;
 844 }
 845
 846 // Used if doing RCU-kfree'ing via call_rcu().
 847 static unsigned long jiffies_at_lazy_cb;
 848 static struct rcu_head lazy_test1_rh;
 849 static int rcu_lazy_test1_cb_called;
 850 static void call_rcu_lazy_test1(struct rcu_head *rh)
 851 {
 852         jiffies_at_lazy_cb = jiffies;
 853         WRITE_ONCE(rcu_lazy_test1_cb_called, 1);
 854 }
 855
 856 static int __init
 857 kfree_scale_init(void)
 858 {
 859         int firsterr = 0;
 860         long i;
 861         unsigned long jif_start;
 862         unsigned long orig_jif;
 863
 864         pr_alert("%s" SCALE_FLAG
 865                  "--- kfree_rcu_test: kfree_mult=%d kfree_by_call_rcu=%d kfree_nthreads=%d kfree_alloc_num=%d kfree_loops=%d kfree_rcu_test_double=%d kfree_rcu_test_single=%d\n",
 866                  scale_type, kfree_mult, kfree_by_call_rcu, kfree_nthreads, kfree_alloc_num, kfree_loops, kfree_rcu_test_double, kfree_rcu_test_single);
 867
 868         // Also, do a quick self-test to ensure laziness is as much as
 869         // expected.
 870         if (kfree_by_call_rcu && !IS_ENABLED(CONFIG_RCU_LAZY)) {
 871                 pr_alert("CONFIG_RCU_LAZY is disabled, falling back to kfree_rcu() for delayed RCU kfree'ing\n");
 872                 kfree_by_call_rcu = 0;
 873         }
 874
 875         if (kfree_by_call_rcu) {
 876                 /* do a test to check the timeout. */
 877                 orig_jif = rcu_get_jiffies_lazy_flush();
 878
 879                 rcu_set_jiffies_lazy_flush(2 * HZ);
 880                 rcu_barrier();
 881
 882                 jif_start = jiffies;
 883                 jiffies_at_lazy_cb = 0;
 884                 call_rcu(&lazy_test1_rh, call_rcu_lazy_test1);
 885
 886                 smp_cond_load_relaxed(&rcu_lazy_test1_cb_called, VAL == 1);
 887
 888                 rcu_set_jiffies_lazy_flush(orig_jif);
 889
 890                 if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
 891                         pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
 892                         WARN_ON_ONCE(1);
 893                         return -1;
 894                 }
 895
 896                 if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) {
 897                         pr_alert("ERROR: call_rcu() CBs are being too lazy!\n");
 898                         WARN_ON_ONCE(1);
 899                         return -1;
 900                 }
 901         }
 902
 903         kfree_nrealthreads = compute_real(kfree_nthreads);
 904         /* Start up the kthreads. */
 905         if (shutdown) {
 906                 init_waitqueue_head(&shutdown_wq);
 907                 firsterr = torture_create_kthread(kfree_scale_shutdown, NULL,
 908                                                   shutdown_task);
 909                 if (torture_init_error(firsterr))
 910                         goto unwind;
 911                 schedule_timeout_uninterruptible(1);
 912         }
 913
 914         pr_alert("kfree object size=%zu, kfree_by_call_rcu=%d\n",
 915                         kfree_mult * sizeof(struct kfree_obj),
 916                         kfree_by_call_rcu);
 917
 918         kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]),
 919                                GFP_KERNEL);
 920         if (kfree_reader_tasks == NULL) {
 921                 firsterr = -ENOMEM;
 922                 goto unwind;
 923         }
 924
 925         for (i = 0; i < kfree_nrealthreads; i++) {
 926                 firsterr = torture_create_kthread(kfree_scale_thread, (void *)i,
 927                                                   kfree_reader_tasks[i]);
 928                 if (torture_init_error(firsterr))
 929                         goto unwind;
 930         }
 931
 932         while (atomic_read(&n_kfree_scale_thread_started) < kfree_nrealthreads)
 933                 schedule_timeout_uninterruptible(1);
 934
 935         torture_init_end();
 936         return 0;
 937
 938 unwind:
 939         torture_init_end();
 940         kfree_scale_cleanup();
 941         return firsterr;
 942 }
 943
 944 static void
 945 rcu_scale_cleanup(void)
 946 {
 947         int i;
 948         int j;
 949         int ngps = 0;
 950         u64 *wdp;
 951         u64 *wdpp;
 952
 953         /*
 954          * Would like warning at start, but everything is expedited
 955          * during the mid-boot phase, so have to wait till the end.
 956          */
 957         if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp)
 958                 SCALEOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
 959         if (rcu_gp_is_normal() && gp_exp)
 960                 SCALEOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
 961         if (gp_exp && gp_async)
 962                 SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");
 963
 964         // If built-in, just report all of the GP kthread's CPU time.
 965         if (IS_BUILTIN(CONFIG_RCU_SCALE_TEST) && !kthread_tp && cur_ops->rso_gp_kthread)
 966                 kthread_tp = cur_ops->rso_gp_kthread();
 967         if (kthread_tp) {
 968                 u32 ns;
 969                 u64 us;
 970
 971                 kthread_stime = kthread_tp->stime - kthread_stime;
 972                 us = div_u64_rem(kthread_stime, 1000, &ns);
 973                 pr_info("rcu_scale: Grace-period kthread CPU time: %llu.%03u us\n", us, ns);
 974                 show_rcu_gp_kthreads();
 975         }
 976         if (kfree_rcu_test) {
 977                 kfree_scale_cleanup();
 978                 return;
 979         }
 980
 981         if (torture_cleanup_begin())
 982                 return;
 983         if (!cur_ops) {
 984                 torture_cleanup_end();
 985                 return;
 986         }
 987
 988         if (reader_tasks) {
 989                 for (i = 0; i < nrealreaders; i++)
 990                         torture_stop_kthread(rcu_scale_reader,
 991                                              reader_tasks[i]);
 992                 kfree(reader_tasks);
 993                 reader_tasks = NULL;
 994         }
 995
 996         if (writer_tasks) {
 997                 for (i = 0; i < nrealwriters; i++) {
 998                         torture_stop_kthread(rcu_scale_writer,
 999                                              writer_tasks[i]);
1000                         if (!writer_n_durations)
1001                                 continue;
1002                         j = writer_n_durations[i];
1003                         pr_alert("%s%s writer %d gps: %d\n",
1004                                  scale_type, SCALE_FLAG, i, j);
1005                         ngps += j;
1006                 }
1007                 pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
1008                          scale_type, SCALE_FLAG,
1009                          t_rcu_scale_writer_started, t_rcu_scale_writer_finished,
1010                          t_rcu_scale_writer_finished -
1011                          t_rcu_scale_writer_started,
1012                          ngps,
1013                          rcuscale_seq_diff(b_rcu_gp_test_finished,
1014                                            b_rcu_gp_test_started));
1015                 for (i = 0; i < nrealwriters; i++) {
1016                         if (!writer_durations)
1017                                 break;
1018                         if (!writer_n_durations)
1019                                 continue;
1020                         wdpp = writer_durations[i];
1021                         if (!wdpp)
1022                                 continue;
1023                         for (j = 0; j < writer_n_durations[i]; j++) {
1024                                 wdp = &wdpp[j];
1025                                 pr_alert("%s%s %4d writer-duration: %5d %llu\n",
1026                                         scale_type, SCALE_FLAG,
1027                                         i, j, *wdp);
1028                                 if (j % 100 == 0)
1029                                         schedule_timeout_uninterruptible(1);
1030                         }
1031                         kfree(writer_durations[i]);
1032                         if (writer_freelists) {
1033                                 int ctr = 0;
1034                                 struct llist_node *llnp;
1035                                 struct writer_freelist *wflp = &writer_freelists[i];
1036
1037                                 if (wflp->ws_mblocks) {
1038                                         llist_for_each(llnp, wflp->ws_lhg.first)
1039                                                 ctr++;
1040                                         llist_for_each(llnp, wflp->ws_lhp.first)
1041                                                 ctr++;
1042                                         WARN_ONCE(ctr != gp_async_max,
1043                                                   "%s: ctr = %d gp_async_max = %d\n",
1044                                                   __func__, ctr, gp_async_max);
1045                                         kfree(wflp->ws_mblocks);
1046                                 }
1047                         }
1048                 }
1049                 kfree(writer_tasks);
1050                 writer_tasks = NULL;
1051                 kfree(writer_durations);
1052                 writer_durations = NULL;
1053                 kfree(writer_n_durations);
1054                 writer_n_durations = NULL;
1055                 kfree(writer_done);
1056                 writer_done = NULL;
1057                 kfree(writer_freelists);
1058                 writer_freelists = NULL;
1059         }
1060
1061         /* Do torture-type-specific cleanup operations.  */
1062         if (cur_ops->cleanup != NULL)
1063                 cur_ops->cleanup();
1064
1065         torture_cleanup_end();
1066 }
1067
1068 /*
1069  * RCU scalability shutdown kthread.  Just waits to be awakened, then shuts
1070  * down system.
1071  */
1072 static int
1073 rcu_scale_shutdown(void *arg)
1074 {
1075         wait_event_idle(shutdown_wq, atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
1076         smp_mb(); /* Wake before output. */
1077         rcu_scale_cleanup();
1078         kernel_power_off();
1079         return -EINVAL;
1080 }
1081
1082 static int __init
1083 rcu_scale_init(void)
1084 {
1085         int firsterr = 0;
1086         long i;
1087         long j;
1088         static struct rcu_scale_ops *scale_ops[] = {
1089                 &rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
1090         };
1091
1092         if (!torture_init_begin(scale_type, verbose))
1093                 return -EBUSY;
1094
1095         /* Process args and announce that the scalability'er is on the job. */
1096         for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
1097                 cur_ops = scale_ops[i];
1098                 if (strcmp(scale_type, cur_ops->name) == 0)
1099                         break;
1100         }
1101         if (i == ARRAY_SIZE(scale_ops)) {
1102                 pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
1103                 pr_alert("rcu-scale types:");
1104                 for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
1105                         pr_cont(" %s", scale_ops[i]->name);
1106                 pr_cont("\n");
1107                 firsterr = -EINVAL;
1108                 cur_ops = NULL;
1109                 goto unwind;
1110         }
1111         if (cur_ops->init)
1112                 cur_ops->init();
1113
1114         if (cur_ops->rso_gp_kthread) {
1115                 kthread_tp = cur_ops->rso_gp_kthread();
1116                 if (kthread_tp)
1117                         kthread_stime = kthread_tp->stime;
1118         }
1119         if (kfree_rcu_test)
1120                 return kfree_scale_init();
1121
1122         nrealwriters = compute_real(nwriters);
1123         nrealreaders = compute_real(nreaders);
1124         atomic_set(&n_rcu_scale_reader_started, 0);
1125         atomic_set(&n_rcu_scale_writer_started, 0);
1126         atomic_set(&n_rcu_scale_writer_finished, 0);
1127         rcu_scale_print_module_parms(cur_ops, "Start of test");
1128
1129         /* Start up the kthreads. */
1130
1131         if (shutdown) {
1132                 init_waitqueue_head(&shutdown_wq);
1133                 firsterr = torture_create_kthread(rcu_scale_shutdown, NULL,
1134                                                   shutdown_task);
1135                 if (torture_init_error(firsterr))
1136                         goto unwind;
1137                 schedule_timeout_uninterruptible(1);
1138         }
1139         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
1140                                GFP_KERNEL);
1141         if (reader_tasks == NULL) {
1142                 SCALEOUT_ERRSTRING("out of memory");
1143                 firsterr = -ENOMEM;
1144                 goto unwind;
1145         }
1146         for (i = 0; i < nrealreaders; i++) {
1147                 firsterr = torture_create_kthread(rcu_scale_reader, (void *)i,
1148                                                   reader_tasks[i]);
1149                 if (torture_init_error(firsterr))
1150                         goto unwind;
1151         }
1152         while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders)
1153                 schedule_timeout_uninterruptible(1);
1154         writer_tasks = kcalloc(nrealwriters, sizeof(writer_tasks[0]), GFP_KERNEL);
1155         writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations), GFP_KERNEL);
1156         writer_n_durations = kcalloc(nrealwriters, sizeof(*writer_n_durations), GFP_KERNEL);
1157         writer_done = kcalloc(nrealwriters, sizeof(writer_done[0]), GFP_KERNEL);
1158         if (gp_async) {
1159                 if (gp_async_max <= 0) {
1160                         pr_warn("%s: gp_async_max = %d must be greater than zero.\n",
1161                                 __func__, gp_async_max);
1162                         WARN_ON_ONCE(IS_BUILTIN(CONFIG_RCU_TORTURE_TEST));
1163                         firsterr = -EINVAL;
1164                         goto unwind;
1165                 }
1166                 writer_freelists = kcalloc(nrealwriters, sizeof(writer_freelists[0]), GFP_KERNEL);
1167         }
1168         if (!writer_tasks || !writer_durations || !writer_n_durations || !writer_done ||
1169             (gp_async && !writer_freelists)) {
1170                 SCALEOUT_ERRSTRING("out of memory");
1171                 firsterr = -ENOMEM;
1172                 goto unwind;
1173         }
1174         for (i = 0; i < nrealwriters; i++) {
1175                 writer_durations[i] =
1176                         kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
1177                                 GFP_KERNEL);
1178                 if (!writer_durations[i]) {
1179                         firsterr = -ENOMEM;
1180                         goto unwind;
1181                 }
1182                 if (writer_freelists) {
1183                         struct writer_freelist *wflp = &writer_freelists[i];
1184
1185                         init_llist_head(&wflp->ws_lhg);
1186                         init_llist_head(&wflp->ws_lhp);
1187                         wflp->ws_mblocks = kcalloc(gp_async_max, sizeof(wflp->ws_mblocks[0]),
1188                                                    GFP_KERNEL);
1189                         if (!wflp->ws_mblocks) {
1190                                 firsterr = -ENOMEM;
1191                                 goto unwind;
1192                         }
1193                         for (j = 0; j < gp_async_max; j++) {
1194                                 struct writer_mblock *wmbp = &wflp->ws_mblocks[j];
1195
1196                                 wmbp->wmb_wfl = wflp;
1197                                 llist_add(&wmbp->wmb_node, &wflp->ws_lhp);
1198                         }
1199                 }
1200                 firsterr = torture_create_kthread(rcu_scale_writer, (void *)i,
1201                                                   writer_tasks[i]);
1202                 if (torture_init_error(firsterr))
1203                         goto unwind;
1204         }
1205         torture_init_end();
1206         return 0;
1207
1208 unwind:
1209         torture_init_end();
1210         rcu_scale_cleanup();
1211         if (shutdown) {
1212                 WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
1213                 kernel_power_off();
1214         }
1215         return firsterr;
1216 }
1217
1218 module_init(rcu_scale_init);
1219 module_exit(rcu_scale_cleanup);