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