kernel/torture.c

   1 /*
   2  * Common functions for in-kernel torture tests.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, you can access it online at
  16  * http://www.gnu.org/licenses/gpl-2.0.html.
  17  *
  18  * Copyright (C) IBM Corporation, 2014
  19  *
  20  * Author: Paul E. McKenney <paulmck@us.ibm.com>
  21  *      Based on kernel/rcu/torture.c.
  22  */
  23
  24 #define pr_fmt(fmt) fmt
  25
  26 #include <linux/types.h>
  27 #include <linux/kernel.h>
  28 #include <linux/init.h>
  29 #include <linux/module.h>
  30 #include <linux/kthread.h>
  31 #include <linux/err.h>
  32 #include <linux/spinlock.h>
  33 #include <linux/smp.h>
  34 #include <linux/interrupt.h>
  35 #include <linux/sched.h>
  36 #include <linux/sched/clock.h>
  37 #include <linux/atomic.h>
  38 #include <linux/bitops.h>
  39 #include <linux/completion.h>
  40 #include <linux/moduleparam.h>
  41 #include <linux/percpu.h>
  42 #include <linux/notifier.h>
  43 #include <linux/reboot.h>
  44 #include <linux/freezer.h>
  45 #include <linux/cpu.h>
  46 #include <linux/delay.h>
  47 #include <linux/stat.h>
  48 #include <linux/slab.h>
  49 #include <linux/trace_clock.h>
  50 #include <linux/ktime.h>
  51 #include <asm/byteorder.h>
  52 #include <linux/torture.h>
  53 #include "rcu/rcu.h"
  54
  55 MODULE_LICENSE("GPL");
  56 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");
  57
  58 static char *torture_type;
  59 static int verbose;
  60
  61 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
  62 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
  63 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with torture running. */
  64 #define FULLSTOP_RMMOD    2     /* Normal rmmod of torture. */
  65 static int fullstop = FULLSTOP_RMMOD;
  66 static DEFINE_MUTEX(fullstop_mutex);
  67
  68 #ifdef CONFIG_HOTPLUG_CPU
  69
  70 /*
  71  * Variables for online-offline handling.  Only present if CPU hotplug
  72  * is enabled, otherwise does nothing.
  73  */
  74
  75 static struct task_struct *onoff_task;
  76 static long onoff_holdoff;
  77 static long onoff_interval;
  78 static long n_offline_attempts;
  79 static long n_offline_successes;
  80 static unsigned long sum_offline;
  81 static int min_offline = -1;
  82 static int max_offline;
  83 static long n_online_attempts;
  84 static long n_online_successes;
  85 static unsigned long sum_online;
  86 static int min_online = -1;
  87 static int max_online;
  88
  89 /*
  90  * Attempt to take a CPU offline.  Return false if the CPU is already
  91  * offline or if it is not subject to CPU-hotplug operations.  The
  92  * caller can detect other failures by looking at the statistics.
  93  */
  94 bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
  95                      unsigned long *sum_offl, int *min_offl, int *max_offl)
  96 {
  97         unsigned long delta;
  98         int ret;
  99         unsigned long starttime;
 100
 101         if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
 102                 return false;
 103
 104         if (verbose > 1)
 105                 pr_alert("%s" TORTURE_FLAG
 106                          "torture_onoff task: offlining %d\n",
 107                          torture_type, cpu);
 108         starttime = jiffies;
 109         (*n_offl_attempts)++;
 110         ret = cpu_down(cpu);
 111         if (ret) {
 112                 if (verbose)
 113                         pr_alert("%s" TORTURE_FLAG
 114                                  "torture_onoff task: offline %d failed: errno %d\n",
 115                                  torture_type, cpu, 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                 (*n_offl_successes)++;
 122                 delta = jiffies - starttime;
 123                 *sum_offl += delta;
 124                 if (*min_offl < 0) {
 125                         *min_offl = delta;
 126                         *max_offl = delta;
 127                 }
 128                 if (*min_offl > delta)
 129                         *min_offl = delta;
 130                 if (*max_offl < delta)
 131                         *max_offl = delta;
 132         }
 133
 134         return true;
 135 }
 136 EXPORT_SYMBOL_GPL(torture_offline);
 137
 138 /*
 139  * Attempt to bring a CPU online.  Return false if the CPU is already
 140  * online or if it is not subject to CPU-hotplug operations.  The
 141  * caller can detect other failures by looking at the statistics.
 142  */
 143 bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
 144                     unsigned long *sum_onl, int *min_onl, int *max_onl)
 145 {
 146         unsigned long delta;
 147         int ret;
 148         unsigned long starttime;
 149
 150         if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
 151                 return false;
 152
 153         if (verbose > 1)
 154                 pr_alert("%s" TORTURE_FLAG
 155                          "torture_onoff task: onlining %d\n",
 156                          torture_type, cpu);
 157         starttime = jiffies;
 158         (*n_onl_attempts)++;
 159         ret = cpu_up(cpu);
 160         if (ret) {
 161                 if (verbose)
 162                         pr_alert("%s" TORTURE_FLAG
 163                                  "torture_onoff task: online %d failed: errno %d\n",
 164                                  torture_type, cpu, ret);
 165         } else {
 166                 if (verbose > 1)
 167                         pr_alert("%s" TORTURE_FLAG
 168                                  "torture_onoff task: onlined %d\n",
 169                                  torture_type, cpu);
 170                 (*n_onl_successes)++;
 171                 delta = jiffies - starttime;
 172                 *sum_onl += delta;
 173                 if (*min_onl < 0) {
 174                         *min_onl = delta;
 175                         *max_onl = delta;
 176                 }
 177                 if (*min_onl > delta)
 178                         *min_onl = delta;
 179                 if (*max_onl < delta)
 180                         *max_onl = delta;
 181         }
 182
 183         return true;
 184 }
 185 EXPORT_SYMBOL_GPL(torture_online);
 186
 187 /*
 188  * Execute random CPU-hotplug operations at the interval specified
 189  * by the onoff_interval.
 190  */
 191 static int
 192 torture_onoff(void *arg)
 193 {
 194         int cpu;
 195         int maxcpu = -1;
 196         DEFINE_TORTURE_RANDOM(rand);
 197
 198         VERBOSE_TOROUT_STRING("torture_onoff task started");
 199         for_each_online_cpu(cpu)
 200                 maxcpu = cpu;
 201         WARN_ON(maxcpu < 0);
 202
 203         if (maxcpu == 0) {
 204                 VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
 205                 goto stop;
 206         }
 207
 208         if (onoff_holdoff > 0) {
 209                 VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
 210                 schedule_timeout_interruptible(onoff_holdoff);
 211                 VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
 212         }
 213         while (!torture_must_stop()) {
 214                 cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
 215                 if (!torture_offline(cpu,
 216                                      &n_offline_attempts, &n_offline_successes,
 217                                      &sum_offline, &min_offline, &max_offline))
 218                         torture_online(cpu,
 219                                        &n_online_attempts, &n_online_successes,
 220                                        &sum_online, &min_online, &max_online);
 221                 schedule_timeout_interruptible(onoff_interval);
 222         }
 223
 224 stop:
 225         torture_kthread_stopping("torture_onoff");
 226         return 0;
 227 }
 228
 229 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 230
 231 /*
 232  * Initiate online-offline handling.
 233  */
 234 int torture_onoff_init(long ooholdoff, long oointerval)
 235 {
 236         int ret = 0;
 237
 238 #ifdef CONFIG_HOTPLUG_CPU
 239         onoff_holdoff = ooholdoff;
 240         onoff_interval = oointerval;
 241         if (onoff_interval <= 0)
 242                 return 0;
 243         ret = torture_create_kthread(torture_onoff, NULL, onoff_task);
 244 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 245         return ret;
 246 }
 247 EXPORT_SYMBOL_GPL(torture_onoff_init);
 248
 249 /*
 250  * Clean up after online/offline testing.
 251  */
 252 static void torture_onoff_cleanup(void)
 253 {
 254 #ifdef CONFIG_HOTPLUG_CPU
 255         if (onoff_task == NULL)
 256                 return;
 257         VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
 258         kthread_stop(onoff_task);
 259         onoff_task = NULL;
 260 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 261 }
 262 EXPORT_SYMBOL_GPL(torture_onoff_cleanup);
 263
 264 /*
 265  * Print online/offline testing statistics.
 266  */
 267 void torture_onoff_stats(void)
 268 {
 269 #ifdef CONFIG_HOTPLUG_CPU
 270         pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
 271                 n_online_successes, n_online_attempts,
 272                 n_offline_successes, n_offline_attempts,
 273                 min_online, max_online,
 274                 min_offline, max_offline,
 275                 sum_online, sum_offline, HZ);
 276 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 277 }
 278 EXPORT_SYMBOL_GPL(torture_onoff_stats);
 279
 280 /*
 281  * Were all the online/offline operations successful?
 282  */
 283 bool torture_onoff_failures(void)
 284 {
 285 #ifdef CONFIG_HOTPLUG_CPU
 286         return n_online_successes != n_online_attempts ||
 287                n_offline_successes != n_offline_attempts;
 288 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 289         return false;
 290 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 291 }
 292 EXPORT_SYMBOL_GPL(torture_onoff_failures);
 293
 294 #define TORTURE_RANDOM_MULT     39916801  /* prime */
 295 #define TORTURE_RANDOM_ADD      479001701 /* prime */
 296 #define TORTURE_RANDOM_REFRESH  10000
 297
 298 /*
 299  * Crude but fast random-number generator.  Uses a linear congruential
 300  * generator, with occasional help from cpu_clock().
 301  */
 302 unsigned long
 303 torture_random(struct torture_random_state *trsp)
 304 {
 305         if (--trsp->trs_count < 0) {
 306                 trsp->trs_state += (unsigned long)local_clock();
 307                 trsp->trs_count = TORTURE_RANDOM_REFRESH;
 308         }
 309         trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
 310                 TORTURE_RANDOM_ADD;
 311         return swahw32(trsp->trs_state);
 312 }
 313 EXPORT_SYMBOL_GPL(torture_random);
 314
 315 /*
 316  * Variables for shuffling.  The idea is to ensure that each CPU stays
 317  * idle for an extended period to test interactions with dyntick idle,
 318  * as well as interactions with any per-CPU variables.
 319  */
 320 struct shuffle_task {
 321         struct list_head st_l;
 322         struct task_struct *st_t;
 323 };
 324
 325 static long shuffle_interval;   /* In jiffies. */
 326 static struct task_struct *shuffler_task;
 327 static cpumask_var_t shuffle_tmp_mask;
 328 static int shuffle_idle_cpu;    /* Force all torture tasks off this CPU */
 329 static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
 330 static DEFINE_MUTEX(shuffle_task_mutex);
 331
 332 /*
 333  * Register a task to be shuffled.  If there is no memory, just splat
 334  * and don't bother registering.
 335  */
 336 void torture_shuffle_task_register(struct task_struct *tp)
 337 {
 338         struct shuffle_task *stp;
 339
 340         if (WARN_ON_ONCE(tp == NULL))
 341                 return;
 342         stp = kmalloc(sizeof(*stp), GFP_KERNEL);
 343         if (WARN_ON_ONCE(stp == NULL))
 344                 return;
 345         stp->st_t = tp;
 346         mutex_lock(&shuffle_task_mutex);
 347         list_add(&stp->st_l, &shuffle_task_list);
 348         mutex_unlock(&shuffle_task_mutex);
 349 }
 350 EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
 351
 352 /*
 353  * Unregister all tasks, for example, at the end of the torture run.
 354  */
 355 static void torture_shuffle_task_unregister_all(void)
 356 {
 357         struct shuffle_task *stp;
 358         struct shuffle_task *p;
 359
 360         mutex_lock(&shuffle_task_mutex);
 361         list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
 362                 list_del(&stp->st_l);
 363                 kfree(stp);
 364         }
 365         mutex_unlock(&shuffle_task_mutex);
 366 }
 367
 368 /* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 369  * A special case is when shuffle_idle_cpu = -1, in which case we allow
 370  * the tasks to run on all CPUs.
 371  */
 372 static void torture_shuffle_tasks(void)
 373 {
 374         struct shuffle_task *stp;
 375
 376         cpumask_setall(shuffle_tmp_mask);
 377         get_online_cpus();
 378
 379         /* No point in shuffling if there is only one online CPU (ex: UP) */
 380         if (num_online_cpus() == 1) {
 381                 put_online_cpus();
 382                 return;
 383         }
 384
 385         /* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
 386         shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 387         if (shuffle_idle_cpu >= nr_cpu_ids)
 388                 shuffle_idle_cpu = -1;
 389         else
 390                 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
 391
 392         mutex_lock(&shuffle_task_mutex);
 393         list_for_each_entry(stp, &shuffle_task_list, st_l)
 394                 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
 395         mutex_unlock(&shuffle_task_mutex);
 396
 397         put_online_cpus();
 398 }
 399
 400 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 401  * system to become idle at a time and cut off its timer ticks. This is meant
 402  * to test the support for such tickless idle CPU in RCU.
 403  */
 404 static int torture_shuffle(void *arg)
 405 {
 406         VERBOSE_TOROUT_STRING("torture_shuffle task started");
 407         do {
 408                 schedule_timeout_interruptible(shuffle_interval);
 409                 torture_shuffle_tasks();
 410                 torture_shutdown_absorb("torture_shuffle");
 411         } while (!torture_must_stop());
 412         torture_kthread_stopping("torture_shuffle");
 413         return 0;
 414 }
 415
 416 /*
 417  * Start the shuffler, with shuffint in jiffies.
 418  */
 419 int torture_shuffle_init(long shuffint)
 420 {
 421         shuffle_interval = shuffint;
 422
 423         shuffle_idle_cpu = -1;
 424
 425         if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
 426                 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
 427                 return -ENOMEM;
 428         }
 429
 430         /* Create the shuffler thread */
 431         return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 432 }
 433 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 434
 435 /*
 436  * Stop the shuffling.
 437  */
 438 static void torture_shuffle_cleanup(void)
 439 {
 440         torture_shuffle_task_unregister_all();
 441         if (shuffler_task) {
 442                 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
 443                 kthread_stop(shuffler_task);
 444                 free_cpumask_var(shuffle_tmp_mask);
 445         }
 446         shuffler_task = NULL;
 447 }
 448 EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
 449
 450 /*
 451  * Variables for auto-shutdown.  This allows "lights out" torture runs
 452  * to be fully scripted.
 453  */
 454 static struct task_struct *shutdown_task;
 455 static ktime_t shutdown_time;           /* time to system shutdown. */
 456 static void (*torture_shutdown_hook)(void);
 457
 458 /*
 459  * Absorb kthreads into a kernel function that won't return, so that
 460  * they won't ever access module text or data again.
 461  */
 462 void torture_shutdown_absorb(const char *title)
 463 {
 464         while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 465                 pr_notice("torture thread %s parking due to system shutdown\n",
 466                           title);
 467                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 468         }
 469 }
 470 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 471
 472 /*
 473  * Cause the torture test to shutdown the system after the test has
 474  * run for the time specified by the shutdown_secs parameter.
 475  */
 476 static int torture_shutdown(void *arg)
 477 {
 478         ktime_t ktime_snap;
 479
 480         VERBOSE_TOROUT_STRING("torture_shutdown task started");
 481         ktime_snap = ktime_get();
 482         while (ktime_before(ktime_snap, shutdown_time) &&
 483                !torture_must_stop()) {
 484                 if (verbose)
 485                         pr_alert("%s" TORTURE_FLAG
 486                                  "torture_shutdown task: %llu ms remaining\n",
 487                                  torture_type,
 488                                  ktime_ms_delta(shutdown_time, ktime_snap));
 489                 set_current_state(TASK_INTERRUPTIBLE);
 490                 schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
 491                 ktime_snap = ktime_get();
 492         }
 493         if (torture_must_stop()) {
 494                 torture_kthread_stopping("torture_shutdown");
 495                 return 0;
 496         }
 497
 498         /* OK, shut down the system. */
 499
 500         VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
 501         shutdown_task = NULL;   /* Avoid self-kill deadlock. */
 502         if (torture_shutdown_hook)
 503                 torture_shutdown_hook();
 504         else
 505                 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 506         rcu_ftrace_dump(DUMP_ALL);
 507         kernel_power_off();     /* Shut down the system. */
 508         return 0;
 509 }
 510
 511 /*
 512  * Start up the shutdown task.
 513  */
 514 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 515 {
 516         int ret = 0;
 517
 518         torture_shutdown_hook = cleanup;
 519         if (ssecs > 0) {
 520                 shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
 521                 ret = torture_create_kthread(torture_shutdown, NULL,
 522                                              shutdown_task);
 523         }
 524         return ret;
 525 }
 526 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 527
 528 /*
 529  * Detect and respond to a system shutdown.
 530  */
 531 static int torture_shutdown_notify(struct notifier_block *unused1,
 532                                    unsigned long unused2, void *unused3)
 533 {
 534         mutex_lock(&fullstop_mutex);
 535         if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
 536                 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
 537                 WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
 538         } else {
 539                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 540         }
 541         mutex_unlock(&fullstop_mutex);
 542         return NOTIFY_DONE;
 543 }
 544
 545 static struct notifier_block torture_shutdown_nb = {
 546         .notifier_call = torture_shutdown_notify,
 547 };
 548
 549 /*
 550  * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 551  * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 552  */
 553 static void torture_shutdown_cleanup(void)
 554 {
 555         unregister_reboot_notifier(&torture_shutdown_nb);
 556         if (shutdown_task != NULL) {
 557                 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
 558                 kthread_stop(shutdown_task);
 559         }
 560         shutdown_task = NULL;
 561 }
 562
 563 /*
 564  * Variables for stuttering, which means to periodically pause and
 565  * restart testing in order to catch bugs that appear when load is
 566  * suddenly applied to or removed from the system.
 567  */
 568 static struct task_struct *stutter_task;
 569 static int stutter_pause_test;
 570 static int stutter;
 571
 572 /*
 573  * Block until the stutter interval ends.  This must be called periodically
 574  * by all running kthreads that need to be subject to stuttering.
 575  */
 576 void stutter_wait(const char *title)
 577 {
 578         int spt;
 579
 580         cond_resched_tasks_rcu_qs();
 581         spt = READ_ONCE(stutter_pause_test);
 582         for (; spt; spt = READ_ONCE(stutter_pause_test)) {
 583                 if (spt == 1) {
 584                         schedule_timeout_interruptible(1);
 585                 } else if (spt == 2) {
 586                         while (READ_ONCE(stutter_pause_test))
 587                                 cond_resched();
 588                 } else {
 589                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 590                 }
 591                 torture_shutdown_absorb(title);
 592         }
 593 }
 594 EXPORT_SYMBOL_GPL(stutter_wait);
 595
 596 /*
 597  * Cause the torture test to "stutter", starting and stopping all
 598  * threads periodically.
 599  */
 600 static int torture_stutter(void *arg)
 601 {
 602         VERBOSE_TOROUT_STRING("torture_stutter task started");
 603         do {
 604                 if (!torture_must_stop() && stutter > 1) {
 605                         WRITE_ONCE(stutter_pause_test, 1);
 606                         schedule_timeout_interruptible(stutter - 1);
 607                         WRITE_ONCE(stutter_pause_test, 2);
 608                         schedule_timeout_interruptible(1);
 609                 }
 610                 WRITE_ONCE(stutter_pause_test, 0);
 611                 if (!torture_must_stop())
 612                         schedule_timeout_interruptible(stutter);
 613                 torture_shutdown_absorb("torture_stutter");
 614         } while (!torture_must_stop());
 615         torture_kthread_stopping("torture_stutter");
 616         return 0;
 617 }
 618
 619 /*
 620  * Initialize and kick off the torture_stutter kthread.
 621  */
 622 int torture_stutter_init(int s)
 623 {
 624         int ret;
 625
 626         stutter = s;
 627         ret = torture_create_kthread(torture_stutter, NULL, stutter_task);
 628         return ret;
 629 }
 630 EXPORT_SYMBOL_GPL(torture_stutter_init);
 631
 632 /*
 633  * Cleanup after the torture_stutter kthread.
 634  */
 635 static void torture_stutter_cleanup(void)
 636 {
 637         if (!stutter_task)
 638                 return;
 639         VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
 640         kthread_stop(stutter_task);
 641         stutter_task = NULL;
 642 }
 643
 644 /*
 645  * Initialize torture module.  Please note that this is -not- invoked via
 646  * the usual module_init() mechanism, but rather by an explicit call from
 647  * the client torture module.  This call must be paired with a later
 648  * torture_init_end().
 649  *
 650  * The runnable parameter points to a flag that controls whether or not
 651  * the test is currently runnable.  If there is no such flag, pass in NULL.
 652  */
 653 bool torture_init_begin(char *ttype, int v)
 654 {
 655         mutex_lock(&fullstop_mutex);
 656         if (torture_type != NULL) {
 657                 pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 658                          ttype, torture_type);
 659                 pr_alert("torture_init_begin: One torture test at a time!\n");
 660                 mutex_unlock(&fullstop_mutex);
 661                 return false;
 662         }
 663         torture_type = ttype;
 664         verbose = v;
 665         fullstop = FULLSTOP_DONTSTOP;
 666         return true;
 667 }
 668 EXPORT_SYMBOL_GPL(torture_init_begin);
 669
 670 /*
 671  * Tell the torture module that initialization is complete.
 672  */
 673 void torture_init_end(void)
 674 {
 675         mutex_unlock(&fullstop_mutex);
 676         register_reboot_notifier(&torture_shutdown_nb);
 677 }
 678 EXPORT_SYMBOL_GPL(torture_init_end);
 679
 680 /*
 681  * Clean up torture module.  Please note that this is -not- invoked via
 682  * the usual module_exit() mechanism, but rather by an explicit call from
 683  * the client torture module.  Returns true if a race with system shutdown
 684  * is detected, otherwise, all kthreads started by functions in this file
 685  * will be shut down.
 686  *
 687  * This must be called before the caller starts shutting down its own
 688  * kthreads.
 689  *
 690  * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 691  * in order to correctly perform the cleanup. They are separated because
 692  * threads can still need to reference the torture_type type, thus nullify
 693  * only after completing all other relevant calls.
 694  */
 695 bool torture_cleanup_begin(void)
 696 {
 697         mutex_lock(&fullstop_mutex);
 698         if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 699                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 700                 mutex_unlock(&fullstop_mutex);
 701                 schedule_timeout_uninterruptible(10);
 702                 return true;
 703         }
 704         WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
 705         mutex_unlock(&fullstop_mutex);
 706         torture_shutdown_cleanup();
 707         torture_shuffle_cleanup();
 708         torture_stutter_cleanup();
 709         torture_onoff_cleanup();
 710         return false;
 711 }
 712 EXPORT_SYMBOL_GPL(torture_cleanup_begin);
 713
 714 void torture_cleanup_end(void)
 715 {
 716         mutex_lock(&fullstop_mutex);
 717         torture_type = NULL;
 718         mutex_unlock(&fullstop_mutex);
 719 }
 720 EXPORT_SYMBOL_GPL(torture_cleanup_end);
 721
 722 /*
 723  * Is it time for the current torture test to stop?
 724  */
 725 bool torture_must_stop(void)
 726 {
 727         return torture_must_stop_irq() || kthread_should_stop();
 728 }
 729 EXPORT_SYMBOL_GPL(torture_must_stop);
 730
 731 /*
 732  * Is it time for the current torture test to stop?  This is the irq-safe
 733  * version, hence no check for kthread_should_stop().
 734  */
 735 bool torture_must_stop_irq(void)
 736 {
 737         return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 738 }
 739 EXPORT_SYMBOL_GPL(torture_must_stop_irq);
 740
 741 /*
 742  * Each kthread must wait for kthread_should_stop() before returning from
 743  * its top-level function, otherwise segfaults ensue.  This function
 744  * prints a "stopping" message and waits for kthread_should_stop(), and
 745  * should be called from all torture kthreads immediately prior to
 746  * returning.
 747  */
 748 void torture_kthread_stopping(char *title)
 749 {
 750         char buf[128];
 751
 752         snprintf(buf, sizeof(buf), "Stopping %s", title);
 753         VERBOSE_TOROUT_STRING(buf);
 754         while (!kthread_should_stop()) {
 755                 torture_shutdown_absorb(title);
 756                 schedule_timeout_uninterruptible(1);
 757         }
 758 }
 759 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
 760
 761 /*
 762  * Create a generic torture kthread that is immediately runnable.  If you
 763  * need the kthread to be stopped so that you can do something to it before
 764  * it starts, you will need to open-code your own.
 765  */
 766 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 767                             char *f, struct task_struct **tp)
 768 {
 769         int ret = 0;
 770
 771         VERBOSE_TOROUT_STRING(m);
 772         *tp = kthread_run(fn, arg, "%s", s);
 773         if (IS_ERR(*tp)) {
 774                 ret = PTR_ERR(*tp);
 775                 VERBOSE_TOROUT_ERRSTRING(f);
 776                 *tp = NULL;
 777         }
 778         torture_shuffle_task_register(*tp);
 779         return ret;
 780 }
 781 EXPORT_SYMBOL_GPL(_torture_create_kthread);
 782
 783 /*
 784  * Stop a generic kthread, emitting a message.
 785  */
 786 void _torture_stop_kthread(char *m, struct task_struct **tp)
 787 {
 788         if (*tp == NULL)
 789                 return;
 790         VERBOSE_TOROUT_STRING(m);
 791         kthread_stop(*tp);
 792         *tp = NULL;
 793 }
 794 EXPORT_SYMBOL_GPL(_torture_stop_kthread);