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