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