kernel/scftorture.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 //
   3 // Torture test for smp_call_function() and friends.
   4 //
   5 // Copyright (C) Facebook, 2020.
   6 //
   7 // Author: Paul E. McKenney <paulmck@kernel.org>
   8
   9 #define pr_fmt(fmt) fmt
  10
  11 #include <linux/atomic.h>
  12 #include <linux/bitops.h>
  13 #include <linux/completion.h>
  14 #include <linux/cpu.h>
  15 #include <linux/delay.h>
  16 #include <linux/err.h>
  17 #include <linux/init.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/kthread.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/module.h>
  23 #include <linux/moduleparam.h>
  24 #include <linux/notifier.h>
  25 #include <linux/percpu.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/rcupdate_trace.h>
  28 #include <linux/reboot.h>
  29 #include <linux/sched.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/smp.h>
  32 #include <linux/stat.h>
  33 #include <linux/srcu.h>
  34 #include <linux/slab.h>
  35 #include <linux/torture.h>
  36 #include <linux/types.h>
  37
  38 #define SCFTORT_STRING "scftorture"
  39 #define SCFTORT_FLAG SCFTORT_STRING ": "
  40
  41 #define SCFTORTOUT(s, x...) \
  42         pr_alert(SCFTORT_FLAG s, ## x)
  43
  44 #define VERBOSE_SCFTORTOUT(s, x...) \
  45         do { if (verbose) pr_alert(SCFTORT_FLAG s, ## x); } while (0)
  46
  47 #define VERBOSE_SCFTORTOUT_ERRSTRING(s, x...) \
  48         do { if (verbose) pr_alert(SCFTORT_FLAG "!!! " s, ## x); } while (0)
  49
  50 MODULE_LICENSE("GPL");
  51 MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>");
  52
  53 // Wait until there are multiple CPUs before starting test.
  54 torture_param(int, holdoff, IS_BUILTIN(CONFIG_SCF_TORTURE_TEST) ? 10 : 0,
  55               "Holdoff time before test start (s)");
  56 torture_param(int, longwait, 0, "Include ridiculously long waits? (seconds)");
  57 torture_param(int, nthreads, -1, "# threads, defaults to -1 for all CPUs.");
  58 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
  59 torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (s), 0=disable");
  60 torture_param(int, shutdown_secs, 0, "Shutdown time (ms), <= zero to disable.");
  61 torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s.");
  62 torture_param(int, stutter_cpus, 5, "Number of jiffies to change CPUs under test, 0=disable");
  63 torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU hotplug.");
  64 torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
  65 torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
  66 torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
  67 torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
  68 torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
  69 torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
  70 torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");
  71
  72 char *torture_type = "";
  73
  74 #ifdef MODULE
  75 # define SCFTORT_SHUTDOWN 0
  76 #else
  77 # define SCFTORT_SHUTDOWN 1
  78 #endif
  79
  80 torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test.");
  81
  82 struct scf_statistics {
  83         struct task_struct *task;
  84         int cpu;
  85         long long n_single;
  86         long long n_single_ofl;
  87         long long n_single_wait;
  88         long long n_single_wait_ofl;
  89         long long n_many;
  90         long long n_many_wait;
  91         long long n_all;
  92         long long n_all_wait;
  93 };
  94
  95 static struct scf_statistics *scf_stats_p;
  96 static struct task_struct *scf_torture_stats_task;
  97 static DEFINE_PER_CPU(long long, scf_invoked_count);
  98
  99 // Data for random primitive selection
 100 #define SCF_PRIM_SINGLE         0
 101 #define SCF_PRIM_MANY           1
 102 #define SCF_PRIM_ALL            2
 103 #define SCF_NPRIMS              (2 * 3) // Need wait and no-wait versions of each.
 104
 105 static char *scf_prim_name[] = {
 106         "smp_call_function_single",
 107         "smp_call_function_many",
 108         "smp_call_function",
 109 };
 110
 111 struct scf_selector {
 112         unsigned long scfs_weight;
 113         int scfs_prim;
 114         bool scfs_wait;
 115 };
 116 static struct scf_selector scf_sel_array[SCF_NPRIMS];
 117 static int scf_sel_array_len;
 118 static unsigned long scf_sel_totweight;
 119
 120 // Communicate between caller and handler.
 121 struct scf_check {
 122         bool scfc_in;
 123         bool scfc_out;
 124         int scfc_cpu; // -1 for not _single().
 125         bool scfc_wait;
 126 };
 127
 128 // Use to wait for all threads to start.
 129 static atomic_t n_started;
 130 static atomic_t n_errs;
 131 static atomic_t n_mb_in_errs;
 132 static atomic_t n_mb_out_errs;
 133 static atomic_t n_alloc_errs;
 134 static bool scfdone;
 135 static char *bangstr = "";
 136
 137 static DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);
 138
 139 // Print torture statistics.  Caller must ensure serialization.
 140 static void scf_torture_stats_print(void)
 141 {
 142         int cpu;
 143         int i;
 144         long long invoked_count = 0;
 145         bool isdone = READ_ONCE(scfdone);
 146         struct scf_statistics scfs = {};
 147
 148         for_each_possible_cpu(cpu)
 149                 invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
 150         for (i = 0; i < nthreads; i++) {
 151                 scfs.n_single += scf_stats_p[i].n_single;
 152                 scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
 153                 scfs.n_single_wait += scf_stats_p[i].n_single_wait;
 154                 scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
 155                 scfs.n_many += scf_stats_p[i].n_many;
 156                 scfs.n_many_wait += scf_stats_p[i].n_many_wait;
 157                 scfs.n_all += scf_stats_p[i].n_all;
 158                 scfs.n_all_wait += scf_stats_p[i].n_all_wait;
 159         }
 160         if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
 161             atomic_read(&n_mb_out_errs) ||
 162             (!IS_ENABLED(CONFIG_KASAN) && atomic_read(&n_alloc_errs)))
 163                 bangstr = "!!! ";
 164         pr_alert("%s %sscf_invoked_count %s: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
 165                  SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count,
 166                  scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
 167                  scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
 168         torture_onoff_stats();
 169         pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
 170                 atomic_read(&n_mb_in_errs), atomic_read(&n_mb_out_errs),
 171                 atomic_read(&n_alloc_errs));
 172 }
 173
 174 // Periodically prints torture statistics, if periodic statistics printing
 175 // was specified via the stat_interval module parameter.
 176 static int
 177 scf_torture_stats(void *arg)
 178 {
 179         VERBOSE_TOROUT_STRING("scf_torture_stats task started");
 180         do {
 181                 schedule_timeout_interruptible(stat_interval * HZ);
 182                 scf_torture_stats_print();
 183                 torture_shutdown_absorb("scf_torture_stats");
 184         } while (!torture_must_stop());
 185         torture_kthread_stopping("scf_torture_stats");
 186         return 0;
 187 }
 188
 189 // Add a primitive to the scf_sel_array[].
 190 static void scf_sel_add(unsigned long weight, int prim, bool wait)
 191 {
 192         struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
 193
 194         // If no weight, if array would overflow, if computing three-place
 195         // percentages would overflow, or if the scf_prim_name[] array would
 196         // overflow, don't bother.  In the last three two cases, complain.
 197         if (!weight ||
 198             WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
 199             WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
 200             WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
 201                 return;
 202         scf_sel_totweight += weight;
 203         scfsp->scfs_weight = scf_sel_totweight;
 204         scfsp->scfs_prim = prim;
 205         scfsp->scfs_wait = wait;
 206         scf_sel_array_len++;
 207 }
 208
 209 // Dump out weighting percentages for scf_prim_name[] array.
 210 static void scf_sel_dump(void)
 211 {
 212         int i;
 213         unsigned long oldw = 0;
 214         struct scf_selector *scfsp;
 215         unsigned long w;
 216
 217         for (i = 0; i < scf_sel_array_len; i++) {
 218                 scfsp = &scf_sel_array[i];
 219                 w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
 220                 pr_info("%s: %3lu.%03lu %s(%s)\n", __func__, w / 1000, w % 1000,
 221                         scf_prim_name[scfsp->scfs_prim],
 222                         scfsp->scfs_wait ? "wait" : "nowait");
 223                 oldw = scfsp->scfs_weight;
 224         }
 225 }
 226
 227 // Randomly pick a primitive and wait/nowait, based on weightings.
 228 static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
 229 {
 230         int i;
 231         unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
 232
 233         for (i = 0; i < scf_sel_array_len; i++)
 234                 if (scf_sel_array[i].scfs_weight >= w)
 235                         return &scf_sel_array[i];
 236         WARN_ON_ONCE(1);
 237         return &scf_sel_array[0];
 238 }
 239
 240 // Update statistics and occasionally burn up mass quantities of CPU time,
 241 // if told to do so via scftorture.longwait.  Otherwise, occasionally burn
 242 // a little bit.
 243 static void scf_handler(void *scfc_in)
 244 {
 245         int i;
 246         int j;
 247         unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));
 248         struct scf_check *scfcp = scfc_in;
 249
 250         if (likely(scfcp)) {
 251                 WRITE_ONCE(scfcp->scfc_out, false); // For multiple receivers.
 252                 if (WARN_ON_ONCE(unlikely(!READ_ONCE(scfcp->scfc_in))))
 253                         atomic_inc(&n_mb_in_errs);
 254         }
 255         this_cpu_inc(scf_invoked_count);
 256         if (longwait <= 0) {
 257                 if (!(r & 0xffc0)) {
 258                         udelay(r & 0x3f);
 259                         goto out;
 260                 }
 261         }
 262         if (r & 0xfff)
 263                 goto out;
 264         r = (r >> 12);
 265         if (longwait <= 0) {
 266                 udelay((r & 0xff) + 1);
 267                 goto out;
 268         }
 269         r = r % longwait + 1;
 270         for (i = 0; i < r; i++) {
 271                 for (j = 0; j < 1000; j++) {
 272                         udelay(1000);
 273                         cpu_relax();
 274                 }
 275         }
 276 out:
 277         if (unlikely(!scfcp))
 278                 return;
 279         if (scfcp->scfc_wait)
 280                 WRITE_ONCE(scfcp->scfc_out, true);
 281         else
 282                 kfree(scfcp);
 283 }
 284
 285 // As above, but check for correct CPU.
 286 static void scf_handler_1(void *scfc_in)
 287 {
 288         struct scf_check *scfcp = scfc_in;
 289
 290         if (likely(scfcp) && WARN_ONCE(smp_processor_id() != scfcp->scfc_cpu, "%s: Wanted CPU %d got CPU %d\n", __func__, scfcp->scfc_cpu, smp_processor_id())) {
 291                 atomic_inc(&n_errs);
 292         }
 293         scf_handler(scfcp);
 294 }
 295
 296 // Randomly do an smp_call_function*() invocation.
 297 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
 298 {
 299         uintptr_t cpu;
 300         int ret = 0;
 301         struct scf_check *scfcp = NULL;
 302         struct scf_selector *scfsp = scf_sel_rand(trsp);
 303
 304         if (use_cpus_read_lock)
 305                 cpus_read_lock();
 306         else
 307                 preempt_disable();
 308         if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
 309                 scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
 310                 if (!scfcp) {
 311                         WARN_ON_ONCE(!IS_ENABLED(CONFIG_KASAN));
 312                         atomic_inc(&n_alloc_errs);
 313                 } else {
 314                         scfcp->scfc_cpu = -1;
 315                         scfcp->scfc_wait = scfsp->scfs_wait;
 316                         scfcp->scfc_out = false;
 317                 }
 318         }
 319         switch (scfsp->scfs_prim) {
 320         case SCF_PRIM_SINGLE:
 321                 cpu = torture_random(trsp) % nr_cpu_ids;
 322                 if (scfsp->scfs_wait)
 323                         scfp->n_single_wait++;
 324                 else
 325                         scfp->n_single++;
 326                 if (scfcp) {
 327                         scfcp->scfc_cpu = cpu;
 328                         barrier(); // Prevent race-reduction compiler optimizations.
 329                         scfcp->scfc_in = true;
 330                 }
 331                 ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);
 332                 if (ret) {
 333                         if (scfsp->scfs_wait)
 334                                 scfp->n_single_wait_ofl++;
 335                         else
 336                                 scfp->n_single_ofl++;
 337                         kfree(scfcp);
 338                         scfcp = NULL;
 339                 }
 340                 break;
 341         case SCF_PRIM_MANY:
 342                 if (scfsp->scfs_wait)
 343                         scfp->n_many_wait++;
 344                 else
 345                         scfp->n_many++;
 346                 if (scfcp) {
 347                         barrier(); // Prevent race-reduction compiler optimizations.
 348                         scfcp->scfc_in = true;
 349                 }
 350                 smp_call_function_many(cpu_online_mask, scf_handler, scfcp, scfsp->scfs_wait);
 351                 break;
 352         case SCF_PRIM_ALL:
 353                 if (scfsp->scfs_wait)
 354                         scfp->n_all_wait++;
 355                 else
 356                         scfp->n_all++;
 357                 if (scfcp) {
 358                         barrier(); // Prevent race-reduction compiler optimizations.
 359                         scfcp->scfc_in = true;
 360                 }
 361                 smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);
 362                 break;
 363         default:
 364                 WARN_ON_ONCE(1);
 365                 if (scfcp)
 366                         scfcp->scfc_out = true;
 367         }
 368         if (scfcp && scfsp->scfs_wait) {
 369                 if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
 370                                  !scfcp->scfc_out))
 371                         atomic_inc(&n_mb_out_errs); // Leak rather than trash!
 372                 else
 373                         kfree(scfcp);
 374                 barrier(); // Prevent race-reduction compiler optimizations.
 375         }
 376         if (use_cpus_read_lock)
 377                 cpus_read_unlock();
 378         else
 379                 preempt_enable();
 380         if (!(torture_random(trsp) & 0xfff))
 381                 schedule_timeout_uninterruptible(1);
 382 }
 383
 384 // SCF test kthread.  Repeatedly does calls to members of the
 385 // smp_call_function() family of functions.
 386 static int scftorture_invoker(void *arg)
 387 {
 388         int cpu;
 389         DEFINE_TORTURE_RANDOM(rand);
 390         struct scf_statistics *scfp = (struct scf_statistics *)arg;
 391         bool was_offline = false;
 392
 393         VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
 394         cpu = scfp->cpu % nr_cpu_ids;
 395         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 396         set_user_nice(current, MAX_NICE);
 397         if (holdoff)
 398                 schedule_timeout_interruptible(holdoff * HZ);
 399
 400         VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
 401
 402         // Make sure that the CPU is affinitized appropriately during testing.
 403         WARN_ON_ONCE(smp_processor_id() != scfp->cpu);
 404
 405         if (!atomic_dec_return(&n_started))
 406                 while (atomic_read_acquire(&n_started)) {
 407                         if (torture_must_stop()) {
 408                                 VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
 409                                 goto end;
 410                         }
 411                         schedule_timeout_uninterruptible(1);
 412                 }
 413
 414         VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);
 415
 416         do {
 417                 scftorture_invoke_one(scfp, &rand);
 418                 while (cpu_is_offline(cpu) && !torture_must_stop()) {
 419                         schedule_timeout_interruptible(HZ / 5);
 420                         was_offline = true;
 421                 }
 422                 if (was_offline) {
 423                         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 424                         was_offline = false;
 425                 }
 426                 cond_resched();
 427         } while (!torture_must_stop());
 428
 429         VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
 430 end:
 431         torture_kthread_stopping("scftorture_invoker");
 432         return 0;
 433 }
 434
 435 static void
 436 scftorture_print_module_parms(const char *tag)
 437 {
 438         pr_alert(SCFTORT_FLAG
 439                  "--- %s:  verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
 440                  verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
 441 }
 442
 443 static void scf_cleanup_handler(void *unused)
 444 {
 445 }
 446
 447 static void scf_torture_cleanup(void)
 448 {
 449         int i;
 450
 451         if (torture_cleanup_begin())
 452                 return;
 453
 454         WRITE_ONCE(scfdone, true);
 455         if (nthreads)
 456                 for (i = 0; i < nthreads; i++)
 457                         torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
 458         else
 459                 goto end;
 460         smp_call_function(scf_cleanup_handler, NULL, 0);
 461         torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
 462         scf_torture_stats_print();  // -After- the stats thread is stopped!
 463         kfree(scf_stats_p);  // -After- the last stats print has completed!
 464         scf_stats_p = NULL;
 465
 466         if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) || atomic_read(&n_mb_out_errs))
 467                 scftorture_print_module_parms("End of test: FAILURE");
 468         else if (torture_onoff_failures())
 469                 scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
 470         else
 471                 scftorture_print_module_parms("End of test: SUCCESS");
 472
 473 end:
 474         torture_cleanup_end();
 475 }
 476
 477 static int __init scf_torture_init(void)
 478 {
 479         long i;
 480         int firsterr = 0;
 481         unsigned long weight_single1 = weight_single;
 482         unsigned long weight_single_wait1 = weight_single_wait;
 483         unsigned long weight_many1 = weight_many;
 484         unsigned long weight_many_wait1 = weight_many_wait;
 485         unsigned long weight_all1 = weight_all;
 486         unsigned long weight_all_wait1 = weight_all_wait;
 487
 488         if (!torture_init_begin(SCFTORT_STRING, verbose))
 489                 return -EBUSY;
 490
 491         scftorture_print_module_parms("Start of test");
 492
 493         if (weight_single == -1 && weight_single_wait == -1 &&
 494             weight_many == -1 && weight_many_wait == -1 &&
 495             weight_all == -1 && weight_all_wait == -1) {
 496                 weight_single1 = 2 * nr_cpu_ids;
 497                 weight_single_wait1 = 2 * nr_cpu_ids;
 498                 weight_many1 = 2;
 499                 weight_many_wait1 = 2;
 500                 weight_all1 = 1;
 501                 weight_all_wait1 = 1;
 502         } else {
 503                 if (weight_single == -1)
 504                         weight_single1 = 0;
 505                 if (weight_single_wait == -1)
 506                         weight_single_wait1 = 0;
 507                 if (weight_many == -1)
 508                         weight_many1 = 0;
 509                 if (weight_many_wait == -1)
 510                         weight_many_wait1 = 0;
 511                 if (weight_all == -1)
 512                         weight_all1 = 0;
 513                 if (weight_all_wait == -1)
 514                         weight_all_wait1 = 0;
 515         }
 516         if (weight_single1 == 0 && weight_single_wait1 == 0 &&
 517             weight_many1 == 0 && weight_many_wait1 == 0 &&
 518             weight_all1 == 0 && weight_all_wait1 == 0) {
 519                 VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
 520                 firsterr = -EINVAL;
 521                 goto unwind;
 522         }
 523         scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
 524         scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
 525         scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
 526         scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
 527         scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
 528         scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
 529         scf_sel_dump();
 530
 531         if (onoff_interval > 0) {
 532                 firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
 533                 if (firsterr)
 534                         goto unwind;
 535         }
 536         if (shutdown_secs > 0) {
 537                 firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
 538                 if (firsterr)
 539                         goto unwind;
 540         }
 541
 542         // Worker tasks invoking smp_call_function().
 543         if (nthreads < 0)
 544                 nthreads = num_online_cpus();
 545         scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
 546         if (!scf_stats_p) {
 547                 VERBOSE_SCFTORTOUT_ERRSTRING("out of memory");
 548                 firsterr = -ENOMEM;
 549                 goto unwind;
 550         }
 551
 552         VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads\n", nthreads);
 553
 554         atomic_set(&n_started, nthreads);
 555         for (i = 0; i < nthreads; i++) {
 556                 scf_stats_p[i].cpu = i;
 557                 firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
 558                                                   scf_stats_p[i].task);
 559                 if (firsterr)
 560                         goto unwind;
 561         }
 562         if (stat_interval > 0) {
 563                 firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
 564                 if (firsterr)
 565                         goto unwind;
 566         }
 567
 568         torture_init_end();
 569         return 0;
 570
 571 unwind:
 572         torture_init_end();
 573         scf_torture_cleanup();
 574         return firsterr;
 575 }
 576
 577 module_init(scf_torture_init);
 578 module_exit(scf_torture_cleanup);