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, 5, "Number of jiffies to run/halt 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_resched, -1, "Testing weight for resched_cpu() operations.");
  66 torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
  67 torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
  68 torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
  69 torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
  70 torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
  71 torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");
  72
  73 char *torture_type = "";
  74
  75 #ifdef MODULE
  76 # define SCFTORT_SHUTDOWN 0
  77 #else
  78 # define SCFTORT_SHUTDOWN 1
  79 #endif
  80
  81 torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test.");
  82
  83 struct scf_statistics {
  84         struct task_struct *task;
  85         int cpu;
  86         long long n_resched;
  87         long long n_single;
  88         long long n_single_ofl;
  89         long long n_single_wait;
  90         long long n_single_wait_ofl;
  91         long long n_many;
  92         long long n_many_wait;
  93         long long n_all;
  94         long long n_all_wait;
  95 };
  96
  97 static struct scf_statistics *scf_stats_p;
  98 static struct task_struct *scf_torture_stats_task;
  99 static DEFINE_PER_CPU(long long, scf_invoked_count);
 100
 101 // Data for random primitive selection
 102 #define SCF_PRIM_RESCHED        0
 103 #define SCF_PRIM_SINGLE         1
 104 #define SCF_PRIM_MANY           2
 105 #define SCF_PRIM_ALL            3
 106 #define SCF_NPRIMS              7 // Need wait and no-wait versions of each,
 107                                   //  except for SCF_PRIM_RESCHED.
 108
 109 static char *scf_prim_name[] = {
 110         "resched_cpu",
 111         "smp_call_function_single",
 112         "smp_call_function_many",
 113         "smp_call_function",
 114 };
 115
 116 struct scf_selector {
 117         unsigned long scfs_weight;
 118         int scfs_prim;
 119         bool scfs_wait;
 120 };
 121 static struct scf_selector scf_sel_array[SCF_NPRIMS];
 122 static int scf_sel_array_len;
 123 static unsigned long scf_sel_totweight;
 124
 125 // Communicate between caller and handler.
 126 struct scf_check {
 127         bool scfc_in;
 128         bool scfc_out;
 129         int scfc_cpu; // -1 for not _single().
 130         bool scfc_wait;
 131 };
 132
 133 // Use to wait for all threads to start.
 134 static atomic_t n_started;
 135 static atomic_t n_errs;
 136 static atomic_t n_mb_in_errs;
 137 static atomic_t n_mb_out_errs;
 138 static atomic_t n_alloc_errs;
 139 static bool scfdone;
 140 static char *bangstr = "";
 141
 142 static DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);
 143
 144 extern void resched_cpu(int cpu); // An alternative IPI vector.
 145
 146 // Print torture statistics.  Caller must ensure serialization.
 147 static void scf_torture_stats_print(void)
 148 {
 149         int cpu;
 150         int i;
 151         long long invoked_count = 0;
 152         bool isdone = READ_ONCE(scfdone);
 153         struct scf_statistics scfs = {};
 154
 155         for_each_possible_cpu(cpu)
 156                 invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
 157         for (i = 0; i < nthreads; i++) {
 158                 scfs.n_resched += scf_stats_p[i].n_resched;
 159                 scfs.n_single += scf_stats_p[i].n_single;
 160                 scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
 161                 scfs.n_single_wait += scf_stats_p[i].n_single_wait;
 162                 scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
 163                 scfs.n_many += scf_stats_p[i].n_many;
 164                 scfs.n_many_wait += scf_stats_p[i].n_many_wait;
 165                 scfs.n_all += scf_stats_p[i].n_all;
 166                 scfs.n_all_wait += scf_stats_p[i].n_all_wait;
 167         }
 168         if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
 169             atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
 170                 bangstr = "!!! ";
 171         pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
 172                  SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
 173                  scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
 174                  scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
 175         torture_onoff_stats();
 176         pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
 177                 atomic_read(&n_mb_in_errs), atomic_read(&n_mb_out_errs),
 178                 atomic_read(&n_alloc_errs));
 179 }
 180
 181 // Periodically prints torture statistics, if periodic statistics printing
 182 // was specified via the stat_interval module parameter.
 183 static int
 184 scf_torture_stats(void *arg)
 185 {
 186         VERBOSE_TOROUT_STRING("scf_torture_stats task started");
 187         do {
 188                 schedule_timeout_interruptible(stat_interval * HZ);
 189                 scf_torture_stats_print();
 190                 torture_shutdown_absorb("scf_torture_stats");
 191         } while (!torture_must_stop());
 192         torture_kthread_stopping("scf_torture_stats");
 193         return 0;
 194 }
 195
 196 // Add a primitive to the scf_sel_array[].
 197 static void scf_sel_add(unsigned long weight, int prim, bool wait)
 198 {
 199         struct scf_selector *scfsp = &scf_sel_array[scf_sel_array_len];
 200
 201         // If no weight, if array would overflow, if computing three-place
 202         // percentages would overflow, or if the scf_prim_name[] array would
 203         // overflow, don't bother.  In the last three two cases, complain.
 204         if (!weight ||
 205             WARN_ON_ONCE(scf_sel_array_len >= ARRAY_SIZE(scf_sel_array)) ||
 206             WARN_ON_ONCE(0 - 100000 * weight <= 100000 * scf_sel_totweight) ||
 207             WARN_ON_ONCE(prim >= ARRAY_SIZE(scf_prim_name)))
 208                 return;
 209         scf_sel_totweight += weight;
 210         scfsp->scfs_weight = scf_sel_totweight;
 211         scfsp->scfs_prim = prim;
 212         scfsp->scfs_wait = wait;
 213         scf_sel_array_len++;
 214 }
 215
 216 // Dump out weighting percentages for scf_prim_name[] array.
 217 static void scf_sel_dump(void)
 218 {
 219         int i;
 220         unsigned long oldw = 0;
 221         struct scf_selector *scfsp;
 222         unsigned long w;
 223
 224         for (i = 0; i < scf_sel_array_len; i++) {
 225                 scfsp = &scf_sel_array[i];
 226                 w = (scfsp->scfs_weight - oldw) * 100000 / scf_sel_totweight;
 227                 pr_info("%s: %3lu.%03lu %s(%s)\n", __func__, w / 1000, w % 1000,
 228                         scf_prim_name[scfsp->scfs_prim],
 229                         scfsp->scfs_wait ? "wait" : "nowait");
 230                 oldw = scfsp->scfs_weight;
 231         }
 232 }
 233
 234 // Randomly pick a primitive and wait/nowait, based on weightings.
 235 static struct scf_selector *scf_sel_rand(struct torture_random_state *trsp)
 236 {
 237         int i;
 238         unsigned long w = torture_random(trsp) % (scf_sel_totweight + 1);
 239
 240         for (i = 0; i < scf_sel_array_len; i++)
 241                 if (scf_sel_array[i].scfs_weight >= w)
 242                         return &scf_sel_array[i];
 243         WARN_ON_ONCE(1);
 244         return &scf_sel_array[0];
 245 }
 246
 247 // Update statistics and occasionally burn up mass quantities of CPU time,
 248 // if told to do so via scftorture.longwait.  Otherwise, occasionally burn
 249 // a little bit.
 250 static void scf_handler(void *scfc_in)
 251 {
 252         int i;
 253         int j;
 254         unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));
 255         struct scf_check *scfcp = scfc_in;
 256
 257         if (likely(scfcp)) {
 258                 WRITE_ONCE(scfcp->scfc_out, false); // For multiple receivers.
 259                 if (WARN_ON_ONCE(unlikely(!READ_ONCE(scfcp->scfc_in))))
 260                         atomic_inc(&n_mb_in_errs);
 261         }
 262         this_cpu_inc(scf_invoked_count);
 263         if (longwait <= 0) {
 264                 if (!(r & 0xffc0))
 265                         udelay(r & 0x3f);
 266                 goto out;
 267         }
 268         if (r & 0xfff)
 269                 goto out;
 270         r = (r >> 12);
 271         if (longwait <= 0) {
 272                 udelay((r & 0xff) + 1);
 273                 goto out;
 274         }
 275         r = r % longwait + 1;
 276         for (i = 0; i < r; i++) {
 277                 for (j = 0; j < 1000; j++) {
 278                         udelay(1000);
 279                         cpu_relax();
 280                 }
 281         }
 282 out:
 283         if (unlikely(!scfcp))
 284                 return;
 285         if (scfcp->scfc_wait)
 286                 WRITE_ONCE(scfcp->scfc_out, true);
 287         else
 288                 kfree(scfcp);
 289 }
 290
 291 // As above, but check for correct CPU.
 292 static void scf_handler_1(void *scfc_in)
 293 {
 294         struct scf_check *scfcp = scfc_in;
 295
 296         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())) {
 297                 atomic_inc(&n_errs);
 298         }
 299         scf_handler(scfcp);
 300 }
 301
 302 // Randomly do an smp_call_function*() invocation.
 303 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
 304 {
 305         uintptr_t cpu;
 306         int ret = 0;
 307         struct scf_check *scfcp = NULL;
 308         struct scf_selector *scfsp = scf_sel_rand(trsp);
 309
 310         if (use_cpus_read_lock)
 311                 cpus_read_lock();
 312         else
 313                 preempt_disable();
 314         if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
 315                 scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
 316                 if (WARN_ON_ONCE(!scfcp)) {
 317                         atomic_inc(&n_alloc_errs);
 318                 } else {
 319                         scfcp->scfc_cpu = -1;
 320                         scfcp->scfc_wait = scfsp->scfs_wait;
 321                         scfcp->scfc_out = false;
 322                 }
 323         }
 324         switch (scfsp->scfs_prim) {
 325         case SCF_PRIM_RESCHED:
 326                 if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
 327                         cpu = torture_random(trsp) % nr_cpu_ids;
 328                         scfp->n_resched++;
 329                         resched_cpu(cpu);
 330                 }
 331                 break;
 332         case SCF_PRIM_SINGLE:
 333                 cpu = torture_random(trsp) % nr_cpu_ids;
 334                 if (scfsp->scfs_wait)
 335                         scfp->n_single_wait++;
 336                 else
 337                         scfp->n_single++;
 338                 if (scfcp) {
 339                         scfcp->scfc_cpu = cpu;
 340                         barrier(); // Prevent race-reduction compiler optimizations.
 341                         scfcp->scfc_in = true;
 342                 }
 343                 ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, scfsp->scfs_wait);
 344                 if (ret) {
 345                         if (scfsp->scfs_wait)
 346                                 scfp->n_single_wait_ofl++;
 347                         else
 348                                 scfp->n_single_ofl++;
 349                         kfree(scfcp);
 350                         scfcp = NULL;
 351                 }
 352                 break;
 353         case SCF_PRIM_MANY:
 354                 if (scfsp->scfs_wait)
 355                         scfp->n_many_wait++;
 356                 else
 357                         scfp->n_many++;
 358                 if (scfcp) {
 359                         barrier(); // Prevent race-reduction compiler optimizations.
 360                         scfcp->scfc_in = true;
 361                 }
 362                 smp_call_function_many(cpu_online_mask, scf_handler, scfcp, scfsp->scfs_wait);
 363                 break;
 364         case SCF_PRIM_ALL:
 365                 if (scfsp->scfs_wait)
 366                         scfp->n_all_wait++;
 367                 else
 368                         scfp->n_all++;
 369                 if (scfcp) {
 370                         barrier(); // Prevent race-reduction compiler optimizations.
 371                         scfcp->scfc_in = true;
 372                 }
 373                 smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);
 374                 break;
 375         default:
 376                 WARN_ON_ONCE(1);
 377                 if (scfcp)
 378                         scfcp->scfc_out = true;
 379         }
 380         if (scfcp && scfsp->scfs_wait) {
 381                 if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
 382                                  !scfcp->scfc_out))
 383                         atomic_inc(&n_mb_out_errs); // Leak rather than trash!
 384                 else
 385                         kfree(scfcp);
 386                 barrier(); // Prevent race-reduction compiler optimizations.
 387         }
 388         if (use_cpus_read_lock)
 389                 cpus_read_unlock();
 390         else
 391                 preempt_enable();
 392         if (!(torture_random(trsp) & 0xfff))
 393                 schedule_timeout_uninterruptible(1);
 394 }
 395
 396 // SCF test kthread.  Repeatedly does calls to members of the
 397 // smp_call_function() family of functions.
 398 static int scftorture_invoker(void *arg)
 399 {
 400         int cpu;
 401         int curcpu;
 402         DEFINE_TORTURE_RANDOM(rand);
 403         struct scf_statistics *scfp = (struct scf_statistics *)arg;
 404         bool was_offline = false;
 405
 406         VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
 407         cpu = scfp->cpu % nr_cpu_ids;
 408         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 409         set_user_nice(current, MAX_NICE);
 410         if (holdoff)
 411                 schedule_timeout_interruptible(holdoff * HZ);
 412
 413         VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
 414
 415         // Make sure that the CPU is affinitized appropriately during testing.
 416         curcpu = smp_processor_id();
 417         WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
 418                   "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
 419                   __func__, scfp->cpu, curcpu, nr_cpu_ids);
 420
 421         if (!atomic_dec_return(&n_started))
 422                 while (atomic_read_acquire(&n_started)) {
 423                         if (torture_must_stop()) {
 424                                 VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
 425                                 goto end;
 426                         }
 427                         schedule_timeout_uninterruptible(1);
 428                 }
 429
 430         VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);
 431
 432         do {
 433                 scftorture_invoke_one(scfp, &rand);
 434                 while (cpu_is_offline(cpu) && !torture_must_stop()) {
 435                         schedule_timeout_interruptible(HZ / 5);
 436                         was_offline = true;
 437                 }
 438                 if (was_offline) {
 439                         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 440                         was_offline = false;
 441                 }
 442                 cond_resched();
 443                 stutter_wait("scftorture_invoker");
 444         } while (!torture_must_stop());
 445
 446         VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
 447 end:
 448         torture_kthread_stopping("scftorture_invoker");
 449         return 0;
 450 }
 451
 452 static void
 453 scftorture_print_module_parms(const char *tag)
 454 {
 455         pr_alert(SCFTORT_FLAG
 456                  "--- %s:  verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
 457                  verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
 458 }
 459
 460 static void scf_cleanup_handler(void *unused)
 461 {
 462 }
 463
 464 static void scf_torture_cleanup(void)
 465 {
 466         int i;
 467
 468         if (torture_cleanup_begin())
 469                 return;
 470
 471         WRITE_ONCE(scfdone, true);
 472         if (nthreads)
 473                 for (i = 0; i < nthreads; i++)
 474                         torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
 475         else
 476                 goto end;
 477         smp_call_function(scf_cleanup_handler, NULL, 0);
 478         torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
 479         scf_torture_stats_print();  // -After- the stats thread is stopped!
 480         kfree(scf_stats_p);  // -After- the last stats print has completed!
 481         scf_stats_p = NULL;
 482
 483         if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) || atomic_read(&n_mb_out_errs))
 484                 scftorture_print_module_parms("End of test: FAILURE");
 485         else if (torture_onoff_failures())
 486                 scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
 487         else
 488                 scftorture_print_module_parms("End of test: SUCCESS");
 489
 490 end:
 491         torture_cleanup_end();
 492 }
 493
 494 static int __init scf_torture_init(void)
 495 {
 496         long i;
 497         int firsterr = 0;
 498         unsigned long weight_resched1 = weight_resched;
 499         unsigned long weight_single1 = weight_single;
 500         unsigned long weight_single_wait1 = weight_single_wait;
 501         unsigned long weight_many1 = weight_many;
 502         unsigned long weight_many_wait1 = weight_many_wait;
 503         unsigned long weight_all1 = weight_all;
 504         unsigned long weight_all_wait1 = weight_all_wait;
 505
 506         if (!torture_init_begin(SCFTORT_STRING, verbose))
 507                 return -EBUSY;
 508
 509         scftorture_print_module_parms("Start of test");
 510
 511         if (weight_resched == -1 && weight_single == -1 && weight_single_wait == -1 &&
 512             weight_many == -1 && weight_many_wait == -1 &&
 513             weight_all == -1 && weight_all_wait == -1) {
 514                 weight_resched1 = 2 * nr_cpu_ids;
 515                 weight_single1 = 2 * nr_cpu_ids;
 516                 weight_single_wait1 = 2 * nr_cpu_ids;
 517                 weight_many1 = 2;
 518                 weight_many_wait1 = 2;
 519                 weight_all1 = 1;
 520                 weight_all_wait1 = 1;
 521         } else {
 522                 if (weight_resched == -1)
 523                         weight_resched1 = 0;
 524                 if (weight_single == -1)
 525                         weight_single1 = 0;
 526                 if (weight_single_wait == -1)
 527                         weight_single_wait1 = 0;
 528                 if (weight_many == -1)
 529                         weight_many1 = 0;
 530                 if (weight_many_wait == -1)
 531                         weight_many_wait1 = 0;
 532                 if (weight_all == -1)
 533                         weight_all1 = 0;
 534                 if (weight_all_wait == -1)
 535                         weight_all_wait1 = 0;
 536         }
 537         if (weight_single1 == 0 && weight_single_wait1 == 0 &&
 538             weight_many1 == 0 && weight_many_wait1 == 0 &&
 539             weight_all1 == 0 && weight_all_wait1 == 0) {
 540                 VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
 541                 firsterr = -EINVAL;
 542                 goto unwind;
 543         }
 544         if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST))
 545                 scf_sel_add(weight_resched1, SCF_PRIM_RESCHED, false);
 546         else if (weight_resched1)
 547                 VERBOSE_SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
 548         scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
 549         scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
 550         scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
 551         scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
 552         scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
 553         scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
 554         scf_sel_dump();
 555
 556         if (onoff_interval > 0) {
 557                 firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
 558                 if (firsterr)
 559                         goto unwind;
 560         }
 561         if (shutdown_secs > 0) {
 562                 firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
 563                 if (firsterr)
 564                         goto unwind;
 565         }
 566         if (stutter > 0) {
 567                 firsterr = torture_stutter_init(stutter, stutter);
 568                 if (firsterr)
 569                         goto unwind;
 570         }
 571
 572         // Worker tasks invoking smp_call_function().
 573         if (nthreads < 0)
 574                 nthreads = num_online_cpus();
 575         scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
 576         if (!scf_stats_p) {
 577                 VERBOSE_SCFTORTOUT_ERRSTRING("out of memory");
 578                 firsterr = -ENOMEM;
 579                 goto unwind;
 580         }
 581
 582         VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads\n", nthreads);
 583
 584         atomic_set(&n_started, nthreads);
 585         for (i = 0; i < nthreads; i++) {
 586                 scf_stats_p[i].cpu = i;
 587                 firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
 588                                                   scf_stats_p[i].task);
 589                 if (firsterr)
 590                         goto unwind;
 591         }
 592         if (stat_interval > 0) {
 593                 firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
 594                 if (firsterr)
 595                         goto unwind;
 596         }
 597
 598         torture_init_end();
 599         return 0;
 600
 601 unwind:
 602         torture_init_end();
 603         scf_torture_cleanup();
 604         return firsterr;
 605 }
 606
 607 module_init(scf_torture_init);
 608 module_exit(scf_torture_cleanup);