kernel/torture.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Common functions for in-kernel torture tests.
   4  *
   5  * Copyright (C) IBM Corporation, 2014
   6  *
   7  * Author: Paul E. McKenney <paulmck@linux.ibm.com>
   8  *      Based on kernel/rcu/torture.c.
   9  */
  10
  11 #define pr_fmt(fmt) fmt
  12
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.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/interrupt.h>
  22 #include <linux/sched.h>
  23 #include <linux/sched/clock.h>
  24 #include <linux/atomic.h>
  25 #include <linux/bitops.h>
  26 #include <linux/completion.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/percpu.h>
  29 #include <linux/notifier.h>
  30 #include <linux/reboot.h>
  31 #include <linux/freezer.h>
  32 #include <linux/cpu.h>
  33 #include <linux/delay.h>
  34 #include <linux/stat.h>
  35 #include <linux/slab.h>
  36 #include <linux/trace_clock.h>
  37 #include <linux/ktime.h>
  38 #include <asm/byteorder.h>
  39 #include <linux/torture.h>
  40 #include "rcu/rcu.h"
  41
  42 MODULE_LICENSE("GPL");
  43 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
  44
  45 static bool disable_onoff_at_boot;
  46 module_param(disable_onoff_at_boot, bool, 0444);
  47
  48 static char *torture_type;
  49 static int verbose;
  50
  51 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
  52 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
  53 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with torture running. */
  54 #define FULLSTOP_RMMOD    2     /* Normal rmmod of torture. */
  55 static int fullstop = FULLSTOP_RMMOD;
  56 static DEFINE_MUTEX(fullstop_mutex);
  57
  58 #ifdef CONFIG_HOTPLUG_CPU
  59
  60 /*
  61  * Variables for online-offline handling.  Only present if CPU hotplug
  62  * is enabled, otherwise does nothing.
  63  */
  64
  65 static struct task_struct *onoff_task;
  66 static long onoff_holdoff;
  67 static long onoff_interval;
  68 static torture_ofl_func *onoff_f;
  69 static long n_offline_attempts;
  70 static long n_offline_successes;
  71 static unsigned long sum_offline;
  72 static int min_offline = -1;
  73 static int max_offline;
  74 static long n_online_attempts;
  75 static long n_online_successes;
  76 static unsigned long sum_online;
  77 static int min_online = -1;
  78 static int max_online;
  79
  80 /*
  81  * Attempt to take a CPU offline.  Return false if the CPU is already
  82  * offline or if it is not subject to CPU-hotplug operations.  The
  83  * caller can detect other failures by looking at the statistics.
  84  */
  85 bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
  86                      unsigned long *sum_offl, int *min_offl, int *max_offl)
  87 {
  88         unsigned long delta;
  89         int ret;
  90         char *s;
  91         unsigned long starttime;
  92
  93         if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
  94                 return false;
  95         if (num_online_cpus() <= 1)
  96                 return false;  /* Can't offline the last CPU. */
  97
  98         if (verbose > 1)
  99                 pr_alert("%s" TORTURE_FLAG
 100                          "torture_onoff task: offlining %d\n",
 101                          torture_type, cpu);
 102         starttime = jiffies;
 103         (*n_offl_attempts)++;
 104         ret = remove_cpu(cpu);
 105         if (ret) {
 106                 s = "";
 107                 if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
 108                         // PCI probe frequently disables hotplug during boot.
 109                         (*n_offl_attempts)--;
 110                         s = " (-EBUSY forgiven during boot)";
 111                 }
 112                 if (verbose)
 113                         pr_alert("%s" TORTURE_FLAG
 114                                  "torture_onoff task: offline %d failed%s: errno %d\n",
 115                                  torture_type, cpu, s, ret);
 116         } else {
 117                 if (verbose > 1)
 118                         pr_alert("%s" TORTURE_FLAG
 119                                  "torture_onoff task: offlined %d\n",
 120                                  torture_type, cpu);
 121                 if (onoff_f)
 122                         onoff_f();
 123                 (*n_offl_successes)++;
 124                 delta = jiffies - starttime;
 125                 *sum_offl += delta;
 126                 if (*min_offl < 0) {
 127                         *min_offl = delta;
 128                         *max_offl = delta;
 129                 }
 130                 if (*min_offl > delta)
 131                         *min_offl = delta;
 132                 if (*max_offl < delta)
 133                         *max_offl = delta;
 134         }
 135
 136         return true;
 137 }
 138 EXPORT_SYMBOL_GPL(torture_offline);
 139
 140 /*
 141  * Attempt to bring a CPU online.  Return false if the CPU is already
 142  * online or if it is not subject to CPU-hotplug operations.  The
 143  * caller can detect other failures by looking at the statistics.
 144  */
 145 bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
 146                     unsigned long *sum_onl, int *min_onl, int *max_onl)
 147 {
 148         unsigned long delta;
 149         int ret;
 150         char *s;
 151         unsigned long starttime;
 152
 153         if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
 154                 return false;
 155
 156         if (verbose > 1)
 157                 pr_alert("%s" TORTURE_FLAG
 158                          "torture_onoff task: onlining %d\n",
 159                          torture_type, cpu);
 160         starttime = jiffies;
 161         (*n_onl_attempts)++;
 162         ret = add_cpu(cpu);
 163         if (ret) {
 164                 s = "";
 165                 if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
 166                         // PCI probe frequently disables hotplug during boot.
 167                         (*n_onl_attempts)--;
 168                         s = " (-EBUSY forgiven during boot)";
 169                 }
 170                 if (verbose)
 171                         pr_alert("%s" TORTURE_FLAG
 172                                  "torture_onoff task: online %d failed%s: errno %d\n",
 173                                  torture_type, cpu, s, ret);
 174         } else {
 175                 if (verbose > 1)
 176                         pr_alert("%s" TORTURE_FLAG
 177                                  "torture_onoff task: onlined %d\n",
 178                                  torture_type, cpu);
 179                 (*n_onl_successes)++;
 180                 delta = jiffies - starttime;
 181                 *sum_onl += delta;
 182                 if (*min_onl < 0) {
 183                         *min_onl = delta;
 184                         *max_onl = delta;
 185                 }
 186                 if (*min_onl > delta)
 187                         *min_onl = delta;
 188                 if (*max_onl < delta)
 189                         *max_onl = delta;
 190         }
 191
 192         return true;
 193 }
 194 EXPORT_SYMBOL_GPL(torture_online);
 195
 196 /*
 197  * Execute random CPU-hotplug operations at the interval specified
 198  * by the onoff_interval.
 199  */
 200 static int
 201 torture_onoff(void *arg)
 202 {
 203         int cpu;
 204         int maxcpu = -1;
 205         DEFINE_TORTURE_RANDOM(rand);
 206         int ret;
 207
 208         VERBOSE_TOROUT_STRING("torture_onoff task started");
 209         for_each_online_cpu(cpu)
 210                 maxcpu = cpu;
 211         WARN_ON(maxcpu < 0);
 212         if (!IS_MODULE(CONFIG_TORTURE_TEST)) {
 213                 for_each_possible_cpu(cpu) {
 214                         if (cpu_online(cpu))
 215                                 continue;
 216                         ret = add_cpu(cpu);
 217                         if (ret && verbose) {
 218                                 pr_alert("%s" TORTURE_FLAG
 219                                          "%s: Initial online %d: errno %d\n",
 220                                          __func__, torture_type, cpu, ret);
 221                         }
 222                 }
 223         }
 224
 225         if (maxcpu == 0) {
 226                 VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
 227                 goto stop;
 228         }
 229
 230         if (onoff_holdoff > 0) {
 231                 VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
 232                 schedule_timeout_interruptible(onoff_holdoff);
 233                 VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
 234         }
 235         while (!torture_must_stop()) {
 236                 if (disable_onoff_at_boot && !rcu_inkernel_boot_has_ended()) {
 237                         schedule_timeout_interruptible(HZ / 10);
 238                         continue;
 239                 }
 240                 cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
 241                 if (!torture_offline(cpu,
 242                                      &n_offline_attempts, &n_offline_successes,
 243                                      &sum_offline, &min_offline, &max_offline))
 244                         torture_online(cpu,
 245                                        &n_online_attempts, &n_online_successes,
 246                                        &sum_online, &min_online, &max_online);
 247                 schedule_timeout_interruptible(onoff_interval);
 248         }
 249
 250 stop:
 251         torture_kthread_stopping("torture_onoff");
 252         return 0;
 253 }
 254
 255 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 256
 257 /*
 258  * Initiate online-offline handling.
 259  */
 260 int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f)
 261 {
 262 #ifdef CONFIG_HOTPLUG_CPU
 263         onoff_holdoff = ooholdoff;
 264         onoff_interval = oointerval;
 265         onoff_f = f;
 266         if (onoff_interval <= 0)
 267                 return 0;
 268         return torture_create_kthread(torture_onoff, NULL, onoff_task);
 269 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 270         return 0;
 271 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 272 }
 273 EXPORT_SYMBOL_GPL(torture_onoff_init);
 274
 275 /*
 276  * Clean up after online/offline testing.
 277  */
 278 static void torture_onoff_cleanup(void)
 279 {
 280 #ifdef CONFIG_HOTPLUG_CPU
 281         if (onoff_task == NULL)
 282                 return;
 283         VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
 284         kthread_stop(onoff_task);
 285         onoff_task = NULL;
 286 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 287 }
 288
 289 /*
 290  * Print online/offline testing statistics.
 291  */
 292 void torture_onoff_stats(void)
 293 {
 294 #ifdef CONFIG_HOTPLUG_CPU
 295         pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
 296                 n_online_successes, n_online_attempts,
 297                 n_offline_successes, n_offline_attempts,
 298                 min_online, max_online,
 299                 min_offline, max_offline,
 300                 sum_online, sum_offline, HZ);
 301 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 302 }
 303 EXPORT_SYMBOL_GPL(torture_onoff_stats);
 304
 305 /*
 306  * Were all the online/offline operations successful?
 307  */
 308 bool torture_onoff_failures(void)
 309 {
 310 #ifdef CONFIG_HOTPLUG_CPU
 311         return n_online_successes != n_online_attempts ||
 312                n_offline_successes != n_offline_attempts;
 313 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 314         return false;
 315 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 316 }
 317 EXPORT_SYMBOL_GPL(torture_onoff_failures);
 318
 319 #define TORTURE_RANDOM_MULT     39916801  /* prime */
 320 #define TORTURE_RANDOM_ADD      479001701 /* prime */
 321 #define TORTURE_RANDOM_REFRESH  10000
 322
 323 /*
 324  * Crude but fast random-number generator.  Uses a linear congruential
 325  * generator, with occasional help from cpu_clock().
 326  */
 327 unsigned long
 328 torture_random(struct torture_random_state *trsp)
 329 {
 330         if (--trsp->trs_count < 0) {
 331                 trsp->trs_state += (unsigned long)local_clock();
 332                 trsp->trs_count = TORTURE_RANDOM_REFRESH;
 333         }
 334         trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
 335                 TORTURE_RANDOM_ADD;
 336         return swahw32(trsp->trs_state);
 337 }
 338 EXPORT_SYMBOL_GPL(torture_random);
 339
 340 /*
 341  * Variables for shuffling.  The idea is to ensure that each CPU stays
 342  * idle for an extended period to test interactions with dyntick idle,
 343  * as well as interactions with any per-CPU variables.
 344  */
 345 struct shuffle_task {
 346         struct list_head st_l;
 347         struct task_struct *st_t;
 348 };
 349
 350 static long shuffle_interval;   /* In jiffies. */
 351 static struct task_struct *shuffler_task;
 352 static cpumask_var_t shuffle_tmp_mask;
 353 static int shuffle_idle_cpu;    /* Force all torture tasks off this CPU */
 354 static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
 355 static DEFINE_MUTEX(shuffle_task_mutex);
 356
 357 /*
 358  * Register a task to be shuffled.  If there is no memory, just splat
 359  * and don't bother registering.
 360  */
 361 void torture_shuffle_task_register(struct task_struct *tp)
 362 {
 363         struct shuffle_task *stp;
 364
 365         if (WARN_ON_ONCE(tp == NULL))
 366                 return;
 367         stp = kmalloc(sizeof(*stp), GFP_KERNEL);
 368         if (WARN_ON_ONCE(stp == NULL))
 369                 return;
 370         stp->st_t = tp;
 371         mutex_lock(&shuffle_task_mutex);
 372         list_add(&stp->st_l, &shuffle_task_list);
 373         mutex_unlock(&shuffle_task_mutex);
 374 }
 375 EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
 376
 377 /*
 378  * Unregister all tasks, for example, at the end of the torture run.
 379  */
 380 static void torture_shuffle_task_unregister_all(void)
 381 {
 382         struct shuffle_task *stp;
 383         struct shuffle_task *p;
 384
 385         mutex_lock(&shuffle_task_mutex);
 386         list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
 387                 list_del(&stp->st_l);
 388                 kfree(stp);
 389         }
 390         mutex_unlock(&shuffle_task_mutex);
 391 }
 392
 393 /* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 394  * A special case is when shuffle_idle_cpu = -1, in which case we allow
 395  * the tasks to run on all CPUs.
 396  */
 397 static void torture_shuffle_tasks(void)
 398 {
 399         struct shuffle_task *stp;
 400
 401         cpumask_setall(shuffle_tmp_mask);
 402         get_online_cpus();
 403
 404         /* No point in shuffling if there is only one online CPU (ex: UP) */
 405         if (num_online_cpus() == 1) {
 406                 put_online_cpus();
 407                 return;
 408         }
 409
 410         /* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
 411         shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 412         if (shuffle_idle_cpu >= nr_cpu_ids)
 413                 shuffle_idle_cpu = -1;
 414         else
 415                 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
 416
 417         mutex_lock(&shuffle_task_mutex);
 418         list_for_each_entry(stp, &shuffle_task_list, st_l)
 419                 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
 420         mutex_unlock(&shuffle_task_mutex);
 421
 422         put_online_cpus();
 423 }
 424
 425 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 426  * system to become idle at a time and cut off its timer ticks. This is meant
 427  * to test the support for such tickless idle CPU in RCU.
 428  */
 429 static int torture_shuffle(void *arg)
 430 {
 431         VERBOSE_TOROUT_STRING("torture_shuffle task started");
 432         do {
 433                 schedule_timeout_interruptible(shuffle_interval);
 434                 torture_shuffle_tasks();
 435                 torture_shutdown_absorb("torture_shuffle");
 436         } while (!torture_must_stop());
 437         torture_kthread_stopping("torture_shuffle");
 438         return 0;
 439 }
 440
 441 /*
 442  * Start the shuffler, with shuffint in jiffies.
 443  */
 444 int torture_shuffle_init(long shuffint)
 445 {
 446         shuffle_interval = shuffint;
 447
 448         shuffle_idle_cpu = -1;
 449
 450         if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
 451                 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
 452                 return -ENOMEM;
 453         }
 454
 455         /* Create the shuffler thread */
 456         return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 457 }
 458 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 459
 460 /*
 461  * Stop the shuffling.
 462  */
 463 static void torture_shuffle_cleanup(void)
 464 {
 465         torture_shuffle_task_unregister_all();
 466         if (shuffler_task) {
 467                 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
 468                 kthread_stop(shuffler_task);
 469                 free_cpumask_var(shuffle_tmp_mask);
 470         }
 471         shuffler_task = NULL;
 472 }
 473
 474 /*
 475  * Variables for auto-shutdown.  This allows "lights out" torture runs
 476  * to be fully scripted.
 477  */
 478 static struct task_struct *shutdown_task;
 479 static ktime_t shutdown_time;           /* time to system shutdown. */
 480 static void (*torture_shutdown_hook)(void);
 481
 482 /*
 483  * Absorb kthreads into a kernel function that won't return, so that
 484  * they won't ever access module text or data again.
 485  */
 486 void torture_shutdown_absorb(const char *title)
 487 {
 488         while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 489                 pr_notice("torture thread %s parking due to system shutdown\n",
 490                           title);
 491                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 492         }
 493 }
 494 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 495
 496 /*
 497  * Cause the torture test to shutdown the system after the test has
 498  * run for the time specified by the shutdown_secs parameter.
 499  */
 500 static int torture_shutdown(void *arg)
 501 {
 502         ktime_t ktime_snap;
 503
 504         VERBOSE_TOROUT_STRING("torture_shutdown task started");
 505         ktime_snap = ktime_get();
 506         while (ktime_before(ktime_snap, shutdown_time) &&
 507                !torture_must_stop()) {
 508                 if (verbose)
 509                         pr_alert("%s" TORTURE_FLAG
 510                                  "torture_shutdown task: %llu ms remaining\n",
 511                                  torture_type,
 512                                  ktime_ms_delta(shutdown_time, ktime_snap));
 513                 set_current_state(TASK_INTERRUPTIBLE);
 514                 schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
 515                 ktime_snap = ktime_get();
 516         }
 517         if (torture_must_stop()) {
 518                 torture_kthread_stopping("torture_shutdown");
 519                 return 0;
 520         }
 521
 522         /* OK, shut down the system. */
 523
 524         VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
 525         shutdown_task = NULL;   /* Avoid self-kill deadlock. */
 526         if (torture_shutdown_hook)
 527                 torture_shutdown_hook();
 528         else
 529                 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 530         rcu_ftrace_dump(DUMP_ALL);
 531         kernel_power_off();     /* Shut down the system. */
 532         return 0;
 533 }
 534
 535 /*
 536  * Start up the shutdown task.
 537  */
 538 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 539 {
 540         torture_shutdown_hook = cleanup;
 541         if (ssecs > 0) {
 542                 shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
 543                 return torture_create_kthread(torture_shutdown, NULL,
 544                                              shutdown_task);
 545         }
 546         return 0;
 547 }
 548 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 549
 550 /*
 551  * Detect and respond to a system shutdown.
 552  */
 553 static int torture_shutdown_notify(struct notifier_block *unused1,
 554                                    unsigned long unused2, void *unused3)
 555 {
 556         mutex_lock(&fullstop_mutex);
 557         if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
 558                 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
 559                 WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
 560         } else {
 561                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 562         }
 563         mutex_unlock(&fullstop_mutex);
 564         return NOTIFY_DONE;
 565 }
 566
 567 static struct notifier_block torture_shutdown_nb = {
 568         .notifier_call = torture_shutdown_notify,
 569 };
 570
 571 /*
 572  * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 573  * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 574  */
 575 static void torture_shutdown_cleanup(void)
 576 {
 577         unregister_reboot_notifier(&torture_shutdown_nb);
 578         if (shutdown_task != NULL) {
 579                 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
 580                 kthread_stop(shutdown_task);
 581         }
 582         shutdown_task = NULL;
 583 }
 584
 585 /*
 586  * Variables for stuttering, which means to periodically pause and
 587  * restart testing in order to catch bugs that appear when load is
 588  * suddenly applied to or removed from the system.
 589  */
 590 static struct task_struct *stutter_task;
 591 static int stutter_pause_test;
 592 static int stutter;
 593 static int stutter_gap;
 594
 595 /*
 596  * Block until the stutter interval ends.  This must be called periodically
 597  * by all running kthreads that need to be subject to stuttering.
 598  */
 599 bool stutter_wait(const char *title)
 600 {
 601         int spt;
 602         bool ret = false;
 603
 604         cond_resched_tasks_rcu_qs();
 605         spt = READ_ONCE(stutter_pause_test);
 606         for (; spt; spt = READ_ONCE(stutter_pause_test)) {
 607                 ret = true;
 608                 if (spt == 1) {
 609                         schedule_timeout_interruptible(1);
 610                 } else if (spt == 2) {
 611                         while (READ_ONCE(stutter_pause_test))
 612                                 cond_resched();
 613                 } else {
 614                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 615                 }
 616                 torture_shutdown_absorb(title);
 617         }
 618         return ret;
 619 }
 620 EXPORT_SYMBOL_GPL(stutter_wait);
 621
 622 /*
 623  * Cause the torture test to "stutter", starting and stopping all
 624  * threads periodically.
 625  */
 626 static int torture_stutter(void *arg)
 627 {
 628         int wtime;
 629
 630         VERBOSE_TOROUT_STRING("torture_stutter task started");
 631         do {
 632                 if (!torture_must_stop() && stutter > 1) {
 633                         wtime = stutter;
 634                         if (stutter > HZ + 1) {
 635                                 WRITE_ONCE(stutter_pause_test, 1);
 636                                 wtime = stutter - HZ - 1;
 637                                 schedule_timeout_interruptible(wtime);
 638                                 wtime = HZ + 1;
 639                         }
 640                         WRITE_ONCE(stutter_pause_test, 2);
 641                         schedule_timeout_interruptible(wtime);
 642                 }
 643                 WRITE_ONCE(stutter_pause_test, 0);
 644                 if (!torture_must_stop())
 645                         schedule_timeout_interruptible(stutter_gap);
 646                 torture_shutdown_absorb("torture_stutter");
 647         } while (!torture_must_stop());
 648         torture_kthread_stopping("torture_stutter");
 649         return 0;
 650 }
 651
 652 /*
 653  * Initialize and kick off the torture_stutter kthread.
 654  */
 655 int torture_stutter_init(const int s, const int sgap)
 656 {
 657         stutter = s;
 658         stutter_gap = sgap;
 659         return torture_create_kthread(torture_stutter, NULL, stutter_task);
 660 }
 661 EXPORT_SYMBOL_GPL(torture_stutter_init);
 662
 663 /*
 664  * Cleanup after the torture_stutter kthread.
 665  */
 666 static void torture_stutter_cleanup(void)
 667 {
 668         if (!stutter_task)
 669                 return;
 670         VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
 671         kthread_stop(stutter_task);
 672         stutter_task = NULL;
 673 }
 674
 675 /*
 676  * Initialize torture module.  Please note that this is -not- invoked via
 677  * the usual module_init() mechanism, but rather by an explicit call from
 678  * the client torture module.  This call must be paired with a later
 679  * torture_init_end().
 680  *
 681  * The runnable parameter points to a flag that controls whether or not
 682  * the test is currently runnable.  If there is no such flag, pass in NULL.
 683  */
 684 bool torture_init_begin(char *ttype, int v)
 685 {
 686         mutex_lock(&fullstop_mutex);
 687         if (torture_type != NULL) {
 688                 pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 689                          ttype, torture_type);
 690                 pr_alert("torture_init_begin: One torture test at a time!\n");
 691                 mutex_unlock(&fullstop_mutex);
 692                 return false;
 693         }
 694         torture_type = ttype;
 695         verbose = v;
 696         fullstop = FULLSTOP_DONTSTOP;
 697         return true;
 698 }
 699 EXPORT_SYMBOL_GPL(torture_init_begin);
 700
 701 /*
 702  * Tell the torture module that initialization is complete.
 703  */
 704 void torture_init_end(void)
 705 {
 706         mutex_unlock(&fullstop_mutex);
 707         register_reboot_notifier(&torture_shutdown_nb);
 708 }
 709 EXPORT_SYMBOL_GPL(torture_init_end);
 710
 711 /*
 712  * Clean up torture module.  Please note that this is -not- invoked via
 713  * the usual module_exit() mechanism, but rather by an explicit call from
 714  * the client torture module.  Returns true if a race with system shutdown
 715  * is detected, otherwise, all kthreads started by functions in this file
 716  * will be shut down.
 717  *
 718  * This must be called before the caller starts shutting down its own
 719  * kthreads.
 720  *
 721  * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 722  * in order to correctly perform the cleanup. They are separated because
 723  * threads can still need to reference the torture_type type, thus nullify
 724  * only after completing all other relevant calls.
 725  */
 726 bool torture_cleanup_begin(void)
 727 {
 728         mutex_lock(&fullstop_mutex);
 729         if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 730                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 731                 mutex_unlock(&fullstop_mutex);
 732                 schedule_timeout_uninterruptible(10);
 733                 return true;
 734         }
 735         WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
 736         mutex_unlock(&fullstop_mutex);
 737         torture_shutdown_cleanup();
 738         torture_shuffle_cleanup();
 739         torture_stutter_cleanup();
 740         torture_onoff_cleanup();
 741         return false;
 742 }
 743 EXPORT_SYMBOL_GPL(torture_cleanup_begin);
 744
 745 void torture_cleanup_end(void)
 746 {
 747         mutex_lock(&fullstop_mutex);
 748         torture_type = NULL;
 749         mutex_unlock(&fullstop_mutex);
 750 }
 751 EXPORT_SYMBOL_GPL(torture_cleanup_end);
 752
 753 /*
 754  * Is it time for the current torture test to stop?
 755  */
 756 bool torture_must_stop(void)
 757 {
 758         return torture_must_stop_irq() || kthread_should_stop();
 759 }
 760 EXPORT_SYMBOL_GPL(torture_must_stop);
 761
 762 /*
 763  * Is it time for the current torture test to stop?  This is the irq-safe
 764  * version, hence no check for kthread_should_stop().
 765  */
 766 bool torture_must_stop_irq(void)
 767 {
 768         return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 769 }
 770 EXPORT_SYMBOL_GPL(torture_must_stop_irq);
 771
 772 /*
 773  * Each kthread must wait for kthread_should_stop() before returning from
 774  * its top-level function, otherwise segfaults ensue.  This function
 775  * prints a "stopping" message and waits for kthread_should_stop(), and
 776  * should be called from all torture kthreads immediately prior to
 777  * returning.
 778  */
 779 void torture_kthread_stopping(char *title)
 780 {
 781         char buf[128];
 782
 783         snprintf(buf, sizeof(buf), "Stopping %s", title);
 784         VERBOSE_TOROUT_STRING(buf);
 785         while (!kthread_should_stop()) {
 786                 torture_shutdown_absorb(title);
 787                 schedule_timeout_uninterruptible(1);
 788         }
 789 }
 790 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
 791
 792 /*
 793  * Create a generic torture kthread that is immediately runnable.  If you
 794  * need the kthread to be stopped so that you can do something to it before
 795  * it starts, you will need to open-code your own.
 796  */
 797 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 798                             char *f, struct task_struct **tp)
 799 {
 800         int ret = 0;
 801
 802         VERBOSE_TOROUT_STRING(m);
 803         *tp = kthread_run(fn, arg, "%s", s);
 804         if (IS_ERR(*tp)) {
 805                 ret = PTR_ERR(*tp);
 806                 VERBOSE_TOROUT_ERRSTRING(f);
 807                 *tp = NULL;
 808         }
 809         torture_shuffle_task_register(*tp);
 810         return ret;
 811 }
 812 EXPORT_SYMBOL_GPL(_torture_create_kthread);
 813
 814 /*
 815  * Stop a generic kthread, emitting a message.
 816  */
 817 void _torture_stop_kthread(char *m, struct task_struct **tp)
 818 {
 819         if (*tp == NULL)
 820                 return;
 821         VERBOSE_TOROUT_STRING(m);
 822         kthread_stop(*tp);
 823         *tp = NULL;
 824 }
 825 EXPORT_SYMBOL_GPL(_torture_stop_kthread);