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