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 = cpu_down(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 = cpu_up(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 = cpu_up(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         if (maxcpu == 0) {
 225                 VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
 226                 goto stop;
 227         }
 228
 229         if (onoff_holdoff > 0) {
 230                 VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
 231                 schedule_timeout_interruptible(onoff_holdoff);
 232                 VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
 233         }
 234         while (!torture_must_stop()) {
 235                 if (disable_onoff_at_boot && !rcu_inkernel_boot_has_ended()) {
 236                         schedule_timeout_interruptible(HZ / 10);
 237                         continue;
 238                 }
 239                 cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
 240                 if (!torture_offline(cpu,
 241                                      &n_offline_attempts, &n_offline_successes,
 242                                      &sum_offline, &min_offline, &max_offline))
 243                         torture_online(cpu,
 244                                        &n_online_attempts, &n_online_successes,
 245                                        &sum_online, &min_online, &max_online);
 246                 schedule_timeout_interruptible(onoff_interval);
 247         }
 248
 249 stop:
 250         torture_kthread_stopping("torture_onoff");
 251         return 0;
 252 }
 253
 254 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 255
 256 /*
 257  * Initiate online-offline handling.
 258  */
 259 int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f)
 260 {
 261 #ifdef CONFIG_HOTPLUG_CPU
 262         onoff_holdoff = ooholdoff;
 263         onoff_interval = oointerval;
 264         onoff_f = f;
 265         if (onoff_interval <= 0)
 266                 return 0;
 267         return torture_create_kthread(torture_onoff, NULL, onoff_task);
 268 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 269         return 0;
 270 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 271 }
 272 EXPORT_SYMBOL_GPL(torture_onoff_init);
 273
 274 /*
 275  * Clean up after online/offline testing.
 276  */
 277 static void torture_onoff_cleanup(void)
 278 {
 279 #ifdef CONFIG_HOTPLUG_CPU
 280         if (onoff_task == NULL)
 281                 return;
 282         VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
 283         kthread_stop(onoff_task);
 284         onoff_task = NULL;
 285 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 286 }
 287
 288 /*
 289  * Print online/offline testing statistics.
 290  */
 291 void torture_onoff_stats(void)
 292 {
 293 #ifdef CONFIG_HOTPLUG_CPU
 294         pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
 295                 n_online_successes, n_online_attempts,
 296                 n_offline_successes, n_offline_attempts,
 297                 min_online, max_online,
 298                 min_offline, max_offline,
 299                 sum_online, sum_offline, HZ);
 300 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 301 }
 302 EXPORT_SYMBOL_GPL(torture_onoff_stats);
 303
 304 /*
 305  * Were all the online/offline operations successful?
 306  */
 307 bool torture_onoff_failures(void)
 308 {
 309 #ifdef CONFIG_HOTPLUG_CPU
 310         return n_online_successes != n_online_attempts ||
 311                n_offline_successes != n_offline_attempts;
 312 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 313         return false;
 314 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 315 }
 316 EXPORT_SYMBOL_GPL(torture_onoff_failures);
 317
 318 #define TORTURE_RANDOM_MULT     39916801  /* prime */
 319 #define TORTURE_RANDOM_ADD      479001701 /* prime */
 320 #define TORTURE_RANDOM_REFRESH  10000
 321
 322 /*
 323  * Crude but fast random-number generator.  Uses a linear congruential
 324  * generator, with occasional help from cpu_clock().
 325  */
 326 unsigned long
 327 torture_random(struct torture_random_state *trsp)
 328 {
 329         if (--trsp->trs_count < 0) {
 330                 trsp->trs_state += (unsigned long)local_clock();
 331                 trsp->trs_count = TORTURE_RANDOM_REFRESH;
 332         }
 333         trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
 334                 TORTURE_RANDOM_ADD;
 335         return swahw32(trsp->trs_state);
 336 }
 337 EXPORT_SYMBOL_GPL(torture_random);
 338
 339 /*
 340  * Variables for shuffling.  The idea is to ensure that each CPU stays
 341  * idle for an extended period to test interactions with dyntick idle,
 342  * as well as interactions with any per-CPU variables.
 343  */
 344 struct shuffle_task {
 345         struct list_head st_l;
 346         struct task_struct *st_t;
 347 };
 348
 349 static long shuffle_interval;   /* In jiffies. */
 350 static struct task_struct *shuffler_task;
 351 static cpumask_var_t shuffle_tmp_mask;
 352 static int shuffle_idle_cpu;    /* Force all torture tasks off this CPU */
 353 static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
 354 static DEFINE_MUTEX(shuffle_task_mutex);
 355
 356 /*
 357  * Register a task to be shuffled.  If there is no memory, just splat
 358  * and don't bother registering.
 359  */
 360 void torture_shuffle_task_register(struct task_struct *tp)
 361 {
 362         struct shuffle_task *stp;
 363
 364         if (WARN_ON_ONCE(tp == NULL))
 365                 return;
 366         stp = kmalloc(sizeof(*stp), GFP_KERNEL);
 367         if (WARN_ON_ONCE(stp == NULL))
 368                 return;
 369         stp->st_t = tp;
 370         mutex_lock(&shuffle_task_mutex);
 371         list_add(&stp->st_l, &shuffle_task_list);
 372         mutex_unlock(&shuffle_task_mutex);
 373 }
 374 EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
 375
 376 /*
 377  * Unregister all tasks, for example, at the end of the torture run.
 378  */
 379 static void torture_shuffle_task_unregister_all(void)
 380 {
 381         struct shuffle_task *stp;
 382         struct shuffle_task *p;
 383
 384         mutex_lock(&shuffle_task_mutex);
 385         list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
 386                 list_del(&stp->st_l);
 387                 kfree(stp);
 388         }
 389         mutex_unlock(&shuffle_task_mutex);
 390 }
 391
 392 /* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 393  * A special case is when shuffle_idle_cpu = -1, in which case we allow
 394  * the tasks to run on all CPUs.
 395  */
 396 static void torture_shuffle_tasks(void)
 397 {
 398         struct shuffle_task *stp;
 399
 400         cpumask_setall(shuffle_tmp_mask);
 401         get_online_cpus();
 402
 403         /* No point in shuffling if there is only one online CPU (ex: UP) */
 404         if (num_online_cpus() == 1) {
 405                 put_online_cpus();
 406                 return;
 407         }
 408
 409         /* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
 410         shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 411         if (shuffle_idle_cpu >= nr_cpu_ids)
 412                 shuffle_idle_cpu = -1;
 413         else
 414                 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
 415
 416         mutex_lock(&shuffle_task_mutex);
 417         list_for_each_entry(stp, &shuffle_task_list, st_l)
 418                 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
 419         mutex_unlock(&shuffle_task_mutex);
 420
 421         put_online_cpus();
 422 }
 423
 424 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 425  * system to become idle at a time and cut off its timer ticks. This is meant
 426  * to test the support for such tickless idle CPU in RCU.
 427  */
 428 static int torture_shuffle(void *arg)
 429 {
 430         VERBOSE_TOROUT_STRING("torture_shuffle task started");
 431         do {
 432                 schedule_timeout_interruptible(shuffle_interval);
 433                 torture_shuffle_tasks();
 434                 torture_shutdown_absorb("torture_shuffle");
 435         } while (!torture_must_stop());
 436         torture_kthread_stopping("torture_shuffle");
 437         return 0;
 438 }
 439
 440 /*
 441  * Start the shuffler, with shuffint in jiffies.
 442  */
 443 int torture_shuffle_init(long shuffint)
 444 {
 445         shuffle_interval = shuffint;
 446
 447         shuffle_idle_cpu = -1;
 448
 449         if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
 450                 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
 451                 return -ENOMEM;
 452         }
 453
 454         /* Create the shuffler thread */
 455         return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 456 }
 457 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 458
 459 /*
 460  * Stop the shuffling.
 461  */
 462 static void torture_shuffle_cleanup(void)
 463 {
 464         torture_shuffle_task_unregister_all();
 465         if (shuffler_task) {
 466                 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
 467                 kthread_stop(shuffler_task);
 468                 free_cpumask_var(shuffle_tmp_mask);
 469         }
 470         shuffler_task = NULL;
 471 }
 472
 473 /*
 474  * Variables for auto-shutdown.  This allows "lights out" torture runs
 475  * to be fully scripted.
 476  */
 477 static struct task_struct *shutdown_task;
 478 static ktime_t shutdown_time;           /* time to system shutdown. */
 479 static void (*torture_shutdown_hook)(void);
 480
 481 /*
 482  * Absorb kthreads into a kernel function that won't return, so that
 483  * they won't ever access module text or data again.
 484  */
 485 void torture_shutdown_absorb(const char *title)
 486 {
 487         while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 488                 pr_notice("torture thread %s parking due to system shutdown\n",
 489                           title);
 490                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 491         }
 492 }
 493 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 494
 495 /*
 496  * Cause the torture test to shutdown the system after the test has
 497  * run for the time specified by the shutdown_secs parameter.
 498  */
 499 static int torture_shutdown(void *arg)
 500 {
 501         ktime_t ktime_snap;
 502
 503         VERBOSE_TOROUT_STRING("torture_shutdown task started");
 504         ktime_snap = ktime_get();
 505         while (ktime_before(ktime_snap, shutdown_time) &&
 506                !torture_must_stop()) {
 507                 if (verbose)
 508                         pr_alert("%s" TORTURE_FLAG
 509                                  "torture_shutdown task: %llu ms remaining\n",
 510                                  torture_type,
 511                                  ktime_ms_delta(shutdown_time, ktime_snap));
 512                 set_current_state(TASK_INTERRUPTIBLE);
 513                 schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
 514                 ktime_snap = ktime_get();
 515         }
 516         if (torture_must_stop()) {
 517                 torture_kthread_stopping("torture_shutdown");
 518                 return 0;
 519         }
 520
 521         /* OK, shut down the system. */
 522
 523         VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
 524         shutdown_task = NULL;   /* Avoid self-kill deadlock. */
 525         if (torture_shutdown_hook)
 526                 torture_shutdown_hook();
 527         else
 528                 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 529         rcu_ftrace_dump(DUMP_ALL);
 530         kernel_power_off();     /* Shut down the system. */
 531         return 0;
 532 }
 533
 534 /*
 535  * Start up the shutdown task.
 536  */
 537 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 538 {
 539         torture_shutdown_hook = cleanup;
 540         if (ssecs > 0) {
 541                 shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
 542                 return torture_create_kthread(torture_shutdown, NULL,
 543                                              shutdown_task);
 544         }
 545         return 0;
 546 }
 547 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 548
 549 /*
 550  * Detect and respond to a system shutdown.
 551  */
 552 static int torture_shutdown_notify(struct notifier_block *unused1,
 553                                    unsigned long unused2, void *unused3)
 554 {
 555         mutex_lock(&fullstop_mutex);
 556         if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
 557                 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
 558                 WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
 559         } else {
 560                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 561         }
 562         mutex_unlock(&fullstop_mutex);
 563         return NOTIFY_DONE;
 564 }
 565
 566 static struct notifier_block torture_shutdown_nb = {
 567         .notifier_call = torture_shutdown_notify,
 568 };
 569
 570 /*
 571  * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 572  * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 573  */
 574 static void torture_shutdown_cleanup(void)
 575 {
 576         unregister_reboot_notifier(&torture_shutdown_nb);
 577         if (shutdown_task != NULL) {
 578                 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
 579                 kthread_stop(shutdown_task);
 580         }
 581         shutdown_task = NULL;
 582 }
 583
 584 /*
 585  * Variables for stuttering, which means to periodically pause and
 586  * restart testing in order to catch bugs that appear when load is
 587  * suddenly applied to or removed from the system.
 588  */
 589 static struct task_struct *stutter_task;
 590 static int stutter_pause_test;
 591 static int stutter;
 592 static int stutter_gap;
 593
 594 /*
 595  * Block until the stutter interval ends.  This must be called periodically
 596  * by all running kthreads that need to be subject to stuttering.
 597  */
 598 bool stutter_wait(const char *title)
 599 {
 600         int spt;
 601         bool ret = false;
 602
 603         cond_resched_tasks_rcu_qs();
 604         spt = READ_ONCE(stutter_pause_test);
 605         for (; spt; spt = READ_ONCE(stutter_pause_test)) {
 606                 ret = true;
 607                 if (spt == 1) {
 608                         schedule_timeout_interruptible(1);
 609                 } else if (spt == 2) {
 610                         while (READ_ONCE(stutter_pause_test))
 611                                 cond_resched();
 612                 } else {
 613                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 614                 }
 615                 torture_shutdown_absorb(title);
 616         }
 617         return ret;
 618 }
 619 EXPORT_SYMBOL_GPL(stutter_wait);
 620
 621 /*
 622  * Cause the torture test to "stutter", starting and stopping all
 623  * threads periodically.
 624  */
 625 static int torture_stutter(void *arg)
 626 {
 627         int wtime;
 628
 629         VERBOSE_TOROUT_STRING("torture_stutter task started");
 630         do {
 631                 if (!torture_must_stop() && stutter > 1) {
 632                         wtime = stutter;
 633                         if (stutter > HZ + 1) {
 634                                 WRITE_ONCE(stutter_pause_test, 1);
 635                                 wtime = stutter - HZ - 1;
 636                                 schedule_timeout_interruptible(wtime);
 637                                 wtime = HZ + 1;
 638                         }
 639                         WRITE_ONCE(stutter_pause_test, 2);
 640                         schedule_timeout_interruptible(wtime);
 641                 }
 642                 WRITE_ONCE(stutter_pause_test, 0);
 643                 if (!torture_must_stop())
 644                         schedule_timeout_interruptible(stutter_gap);
 645                 torture_shutdown_absorb("torture_stutter");
 646         } while (!torture_must_stop());
 647         torture_kthread_stopping("torture_stutter");
 648         return 0;
 649 }
 650
 651 /*
 652  * Initialize and kick off the torture_stutter kthread.
 653  */
 654 int torture_stutter_init(const int s, const int sgap)
 655 {
 656         stutter = s;
 657         stutter_gap = sgap;
 658         return torture_create_kthread(torture_stutter, NULL, stutter_task);
 659 }
 660 EXPORT_SYMBOL_GPL(torture_stutter_init);
 661
 662 /*
 663  * Cleanup after the torture_stutter kthread.
 664  */
 665 static void torture_stutter_cleanup(void)
 666 {
 667         if (!stutter_task)
 668                 return;
 669         VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
 670         kthread_stop(stutter_task);
 671         stutter_task = NULL;
 672 }
 673
 674 /*
 675  * Initialize torture module.  Please note that this is -not- invoked via
 676  * the usual module_init() mechanism, but rather by an explicit call from
 677  * the client torture module.  This call must be paired with a later
 678  * torture_init_end().
 679  *
 680  * The runnable parameter points to a flag that controls whether or not
 681  * the test is currently runnable.  If there is no such flag, pass in NULL.
 682  */
 683 bool torture_init_begin(char *ttype, int v)
 684 {
 685         mutex_lock(&fullstop_mutex);
 686         if (torture_type != NULL) {
 687                 pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 688                          ttype, torture_type);
 689                 pr_alert("torture_init_begin: One torture test at a time!\n");
 690                 mutex_unlock(&fullstop_mutex);
 691                 return false;
 692         }
 693         torture_type = ttype;
 694         verbose = v;
 695         fullstop = FULLSTOP_DONTSTOP;
 696         return true;
 697 }
 698 EXPORT_SYMBOL_GPL(torture_init_begin);
 699
 700 /*
 701  * Tell the torture module that initialization is complete.
 702  */
 703 void torture_init_end(void)
 704 {
 705         mutex_unlock(&fullstop_mutex);
 706         register_reboot_notifier(&torture_shutdown_nb);
 707 }
 708 EXPORT_SYMBOL_GPL(torture_init_end);
 709
 710 /*
 711  * Clean up torture module.  Please note that this is -not- invoked via
 712  * the usual module_exit() mechanism, but rather by an explicit call from
 713  * the client torture module.  Returns true if a race with system shutdown
 714  * is detected, otherwise, all kthreads started by functions in this file
 715  * will be shut down.
 716  *
 717  * This must be called before the caller starts shutting down its own
 718  * kthreads.
 719  *
 720  * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 721  * in order to correctly perform the cleanup. They are separated because
 722  * threads can still need to reference the torture_type type, thus nullify
 723  * only after completing all other relevant calls.
 724  */
 725 bool torture_cleanup_begin(void)
 726 {
 727         mutex_lock(&fullstop_mutex);
 728         if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 729                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 730                 mutex_unlock(&fullstop_mutex);
 731                 schedule_timeout_uninterruptible(10);
 732                 return true;
 733         }
 734         WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
 735         mutex_unlock(&fullstop_mutex);
 736         torture_shutdown_cleanup();
 737         torture_shuffle_cleanup();
 738         torture_stutter_cleanup();
 739         torture_onoff_cleanup();
 740         return false;
 741 }
 742 EXPORT_SYMBOL_GPL(torture_cleanup_begin);
 743
 744 void torture_cleanup_end(void)
 745 {
 746         mutex_lock(&fullstop_mutex);
 747         torture_type = NULL;
 748         mutex_unlock(&fullstop_mutex);
 749 }
 750 EXPORT_SYMBOL_GPL(torture_cleanup_end);
 751
 752 /*
 753  * Is it time for the current torture test to stop?
 754  */
 755 bool torture_must_stop(void)
 756 {
 757         return torture_must_stop_irq() || kthread_should_stop();
 758 }
 759 EXPORT_SYMBOL_GPL(torture_must_stop);
 760
 761 /*
 762  * Is it time for the current torture test to stop?  This is the irq-safe
 763  * version, hence no check for kthread_should_stop().
 764  */
 765 bool torture_must_stop_irq(void)
 766 {
 767         return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 768 }
 769 EXPORT_SYMBOL_GPL(torture_must_stop_irq);
 770
 771 /*
 772  * Each kthread must wait for kthread_should_stop() before returning from
 773  * its top-level function, otherwise segfaults ensue.  This function
 774  * prints a "stopping" message and waits for kthread_should_stop(), and
 775  * should be called from all torture kthreads immediately prior to
 776  * returning.
 777  */
 778 void torture_kthread_stopping(char *title)
 779 {
 780         char buf[128];
 781
 782         snprintf(buf, sizeof(buf), "Stopping %s", title);
 783         VERBOSE_TOROUT_STRING(buf);
 784         while (!kthread_should_stop()) {
 785                 torture_shutdown_absorb(title);
 786                 schedule_timeout_uninterruptible(1);
 787         }
 788 }
 789 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
 790
 791 /*
 792  * Create a generic torture kthread that is immediately runnable.  If you
 793  * need the kthread to be stopped so that you can do something to it before
 794  * it starts, you will need to open-code your own.
 795  */
 796 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 797                             char *f, struct task_struct **tp)
 798 {
 799         int ret = 0;
 800
 801         VERBOSE_TOROUT_STRING(m);
 802         *tp = kthread_run(fn, arg, "%s", s);
 803         if (IS_ERR(*tp)) {
 804                 ret = PTR_ERR(*tp);
 805                 VERBOSE_TOROUT_ERRSTRING(f);
 806                 *tp = NULL;
 807         }
 808         torture_shuffle_task_register(*tp);
 809         return ret;
 810 }
 811 EXPORT_SYMBOL_GPL(_torture_create_kthread);
 812
 813 /*
 814  * Stop a generic kthread, emitting a message.
 815  */
 816 void _torture_stop_kthread(char *m, struct task_struct **tp)
 817 {
 818         if (*tp == NULL)
 819                 return;
 820         VERBOSE_TOROUT_STRING(m);
 821         kthread_stop(*tp);
 822         *tp = NULL;
 823 }
 824 EXPORT_SYMBOL_GPL(_torture_stop_kthread);