kernel/torture.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Common functions for in-kernel torture tests.
   4  *
   5  * Copyright (C) IBM Corporation, 2014
   6  *
   7  * Author: Paul E. McKenney <paulmck@linux.ibm.com>
   8  *      Based on kernel/rcu/torture.c.
   9  */
  10
  11 #define pr_fmt(fmt) fmt
  12
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/module.h>
  17 #include <linux/kthread.h>
  18 #include <linux/err.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/smp.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/sched.h>
  23 #include <linux/sched/clock.h>
  24 #include <linux/atomic.h>
  25 #include <linux/bitops.h>
  26 #include <linux/completion.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/percpu.h>
  29 #include <linux/notifier.h>
  30 #include <linux/reboot.h>
  31 #include <linux/freezer.h>
  32 #include <linux/cpu.h>
  33 #include <linux/delay.h>
  34 #include <linux/stat.h>
  35 #include <linux/slab.h>
  36 #include <linux/trace_clock.h>
  37 #include <linux/ktime.h>
  38 #include <asm/byteorder.h>
  39 #include <linux/torture.h>
  40 #include "rcu/rcu.h"
  41
  42 MODULE_LICENSE("GPL");
  43 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
  44
  45 static bool disable_onoff_at_boot;
  46 module_param(disable_onoff_at_boot, bool, 0444);
  47
  48 static bool ftrace_dump_at_shutdown;
  49 module_param(ftrace_dump_at_shutdown, bool, 0444);
  50
  51 static char *torture_type;
  52 static int verbose;
  53
  54 /* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
  55 #define FULLSTOP_DONTSTOP 0     /* Normal operation. */
  56 #define FULLSTOP_SHUTDOWN 1     /* System shutdown with torture running. */
  57 #define FULLSTOP_RMMOD    2     /* Normal rmmod of torture. */
  58 static int fullstop = FULLSTOP_RMMOD;
  59 static DEFINE_MUTEX(fullstop_mutex);
  60
  61 #ifdef CONFIG_HOTPLUG_CPU
  62
  63 /*
  64  * Variables for online-offline handling.  Only present if CPU hotplug
  65  * is enabled, otherwise does nothing.
  66  */
  67
  68 static struct task_struct *onoff_task;
  69 static long onoff_holdoff;
  70 static long onoff_interval;
  71 static torture_ofl_func *onoff_f;
  72 static long n_offline_attempts;
  73 static long n_offline_successes;
  74 static unsigned long sum_offline;
  75 static int min_offline = -1;
  76 static int max_offline;
  77 static long n_online_attempts;
  78 static long n_online_successes;
  79 static unsigned long sum_online;
  80 static int min_online = -1;
  81 static int max_online;
  82
  83 /*
  84  * Attempt to take a CPU offline.  Return false if the CPU is already
  85  * offline or if it is not subject to CPU-hotplug operations.  The
  86  * caller can detect other failures by looking at the statistics.
  87  */
  88 bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
  89                      unsigned long *sum_offl, int *min_offl, int *max_offl)
  90 {
  91         unsigned long delta;
  92         int ret;
  93         char *s;
  94         unsigned long starttime;
  95
  96         if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
  97                 return false;
  98         if (num_online_cpus() <= 1)
  99                 return false;  /* Can't offline the last CPU. */
 100
 101         if (verbose > 1)
 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 = remove_cpu(cpu);
 108         if (ret) {
 109                 s = "";
 110                 if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
 111                         // PCI probe frequently disables hotplug during boot.
 112                         (*n_offl_attempts)--;
 113                         s = " (-EBUSY forgiven during boot)";
 114                 }
 115                 if (verbose)
 116                         pr_alert("%s" TORTURE_FLAG
 117                                  "torture_onoff task: offline %d failed%s: errno %d\n",
 118                                  torture_type, cpu, s, ret);
 119         } else {
 120                 if (verbose > 1)
 121                         pr_alert("%s" TORTURE_FLAG
 122                                  "torture_onoff task: offlined %d\n",
 123                                  torture_type, cpu);
 124                 if (onoff_f)
 125                         onoff_f();
 126                 (*n_offl_successes)++;
 127                 delta = jiffies - starttime;
 128                 *sum_offl += delta;
 129                 if (*min_offl < 0) {
 130                         *min_offl = delta;
 131                         *max_offl = delta;
 132                 }
 133                 if (*min_offl > delta)
 134                         *min_offl = delta;
 135                 if (*max_offl < delta)
 136                         *max_offl = delta;
 137         }
 138
 139         return true;
 140 }
 141 EXPORT_SYMBOL_GPL(torture_offline);
 142
 143 /*
 144  * Attempt to bring a CPU online.  Return false if the CPU is already
 145  * online or if it is not subject to CPU-hotplug operations.  The
 146  * caller can detect other failures by looking at the statistics.
 147  */
 148 bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
 149                     unsigned long *sum_onl, int *min_onl, int *max_onl)
 150 {
 151         unsigned long delta;
 152         int ret;
 153         char *s;
 154         unsigned long starttime;
 155
 156         if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
 157                 return false;
 158
 159         if (verbose > 1)
 160                 pr_alert("%s" TORTURE_FLAG
 161                          "torture_onoff task: onlining %d\n",
 162                          torture_type, cpu);
 163         starttime = jiffies;
 164         (*n_onl_attempts)++;
 165         ret = add_cpu(cpu);
 166         if (ret) {
 167                 s = "";
 168                 if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
 169                         // PCI probe frequently disables hotplug during boot.
 170                         (*n_onl_attempts)--;
 171                         s = " (-EBUSY forgiven during boot)";
 172                 }
 173                 if (verbose)
 174                         pr_alert("%s" TORTURE_FLAG
 175                                  "torture_onoff task: online %d failed%s: errno %d\n",
 176                                  torture_type, cpu, s, ret);
 177         } else {
 178                 if (verbose > 1)
 179                         pr_alert("%s" TORTURE_FLAG
 180                                  "torture_onoff task: onlined %d\n",
 181                                  torture_type, cpu);
 182                 (*n_onl_successes)++;
 183                 delta = jiffies - starttime;
 184                 *sum_onl += delta;
 185                 if (*min_onl < 0) {
 186                         *min_onl = delta;
 187                         *max_onl = delta;
 188                 }
 189                 if (*min_onl > delta)
 190                         *min_onl = delta;
 191                 if (*max_onl < delta)
 192                         *max_onl = delta;
 193         }
 194
 195         return true;
 196 }
 197 EXPORT_SYMBOL_GPL(torture_online);
 198
 199 /*
 200  * Execute random CPU-hotplug operations at the interval specified
 201  * by the onoff_interval.
 202  */
 203 static int
 204 torture_onoff(void *arg)
 205 {
 206         int cpu;
 207         int maxcpu = -1;
 208         DEFINE_TORTURE_RANDOM(rand);
 209         int ret;
 210
 211         VERBOSE_TOROUT_STRING("torture_onoff task started");
 212         for_each_online_cpu(cpu)
 213                 maxcpu = cpu;
 214         WARN_ON(maxcpu < 0);
 215         if (!IS_MODULE(CONFIG_TORTURE_TEST)) {
 216                 for_each_possible_cpu(cpu) {
 217                         if (cpu_online(cpu))
 218                                 continue;
 219                         ret = add_cpu(cpu);
 220                         if (ret && verbose) {
 221                                 pr_alert("%s" TORTURE_FLAG
 222                                          "%s: Initial online %d: errno %d\n",
 223                                          __func__, torture_type, cpu, ret);
 224                         }
 225                 }
 226         }
 227
 228         if (maxcpu == 0) {
 229                 VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
 230                 goto stop;
 231         }
 232
 233         if (onoff_holdoff > 0) {
 234                 VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
 235                 schedule_timeout_interruptible(onoff_holdoff);
 236                 VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
 237         }
 238         while (!torture_must_stop()) {
 239                 if (disable_onoff_at_boot && !rcu_inkernel_boot_has_ended()) {
 240                         schedule_timeout_interruptible(HZ / 10);
 241                         continue;
 242                 }
 243                 cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
 244                 if (!torture_offline(cpu,
 245                                      &n_offline_attempts, &n_offline_successes,
 246                                      &sum_offline, &min_offline, &max_offline))
 247                         torture_online(cpu,
 248                                        &n_online_attempts, &n_online_successes,
 249                                        &sum_online, &min_online, &max_online);
 250                 schedule_timeout_interruptible(onoff_interval);
 251         }
 252
 253 stop:
 254         torture_kthread_stopping("torture_onoff");
 255         return 0;
 256 }
 257
 258 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 259
 260 /*
 261  * Initiate online-offline handling.
 262  */
 263 int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f)
 264 {
 265 #ifdef CONFIG_HOTPLUG_CPU
 266         onoff_holdoff = ooholdoff;
 267         onoff_interval = oointerval;
 268         onoff_f = f;
 269         if (onoff_interval <= 0)
 270                 return 0;
 271         return torture_create_kthread(torture_onoff, NULL, onoff_task);
 272 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 273         return 0;
 274 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 275 }
 276 EXPORT_SYMBOL_GPL(torture_onoff_init);
 277
 278 /*
 279  * Clean up after online/offline testing.
 280  */
 281 static void torture_onoff_cleanup(void)
 282 {
 283 #ifdef CONFIG_HOTPLUG_CPU
 284         if (onoff_task == NULL)
 285                 return;
 286         VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
 287         kthread_stop(onoff_task);
 288         onoff_task = NULL;
 289 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 290 }
 291
 292 /*
 293  * Print online/offline testing statistics.
 294  */
 295 void torture_onoff_stats(void)
 296 {
 297 #ifdef CONFIG_HOTPLUG_CPU
 298         pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
 299                 n_online_successes, n_online_attempts,
 300                 n_offline_successes, n_offline_attempts,
 301                 min_online, max_online,
 302                 min_offline, max_offline,
 303                 sum_online, sum_offline, HZ);
 304 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 305 }
 306 EXPORT_SYMBOL_GPL(torture_onoff_stats);
 307
 308 /*
 309  * Were all the online/offline operations successful?
 310  */
 311 bool torture_onoff_failures(void)
 312 {
 313 #ifdef CONFIG_HOTPLUG_CPU
 314         return n_online_successes != n_online_attempts ||
 315                n_offline_successes != n_offline_attempts;
 316 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 317         return false;
 318 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 319 }
 320 EXPORT_SYMBOL_GPL(torture_onoff_failures);
 321
 322 #define TORTURE_RANDOM_MULT     39916801  /* prime */
 323 #define TORTURE_RANDOM_ADD      479001701 /* prime */
 324 #define TORTURE_RANDOM_REFRESH  10000
 325
 326 /*
 327  * Crude but fast random-number generator.  Uses a linear congruential
 328  * generator, with occasional help from cpu_clock().
 329  */
 330 unsigned long
 331 torture_random(struct torture_random_state *trsp)
 332 {
 333         if (--trsp->trs_count < 0) {
 334                 trsp->trs_state += (unsigned long)local_clock();
 335                 trsp->trs_count = TORTURE_RANDOM_REFRESH;
 336         }
 337         trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
 338                 TORTURE_RANDOM_ADD;
 339         return swahw32(trsp->trs_state);
 340 }
 341 EXPORT_SYMBOL_GPL(torture_random);
 342
 343 /*
 344  * Variables for shuffling.  The idea is to ensure that each CPU stays
 345  * idle for an extended period to test interactions with dyntick idle,
 346  * as well as interactions with any per-CPU variables.
 347  */
 348 struct shuffle_task {
 349         struct list_head st_l;
 350         struct task_struct *st_t;
 351 };
 352
 353 static long shuffle_interval;   /* In jiffies. */
 354 static struct task_struct *shuffler_task;
 355 static cpumask_var_t shuffle_tmp_mask;
 356 static int shuffle_idle_cpu;    /* Force all torture tasks off this CPU */
 357 static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
 358 static DEFINE_MUTEX(shuffle_task_mutex);
 359
 360 /*
 361  * Register a task to be shuffled.  If there is no memory, just splat
 362  * and don't bother registering.
 363  */
 364 void torture_shuffle_task_register(struct task_struct *tp)
 365 {
 366         struct shuffle_task *stp;
 367
 368         if (WARN_ON_ONCE(tp == NULL))
 369                 return;
 370         stp = kmalloc(sizeof(*stp), GFP_KERNEL);
 371         if (WARN_ON_ONCE(stp == NULL))
 372                 return;
 373         stp->st_t = tp;
 374         mutex_lock(&shuffle_task_mutex);
 375         list_add(&stp->st_l, &shuffle_task_list);
 376         mutex_unlock(&shuffle_task_mutex);
 377 }
 378 EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
 379
 380 /*
 381  * Unregister all tasks, for example, at the end of the torture run.
 382  */
 383 static void torture_shuffle_task_unregister_all(void)
 384 {
 385         struct shuffle_task *stp;
 386         struct shuffle_task *p;
 387
 388         mutex_lock(&shuffle_task_mutex);
 389         list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
 390                 list_del(&stp->st_l);
 391                 kfree(stp);
 392         }
 393         mutex_unlock(&shuffle_task_mutex);
 394 }
 395
 396 /* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 397  * A special case is when shuffle_idle_cpu = -1, in which case we allow
 398  * the tasks to run on all CPUs.
 399  */
 400 static void torture_shuffle_tasks(void)
 401 {
 402         struct shuffle_task *stp;
 403
 404         cpumask_setall(shuffle_tmp_mask);
 405         get_online_cpus();
 406
 407         /* No point in shuffling if there is only one online CPU (ex: UP) */
 408         if (num_online_cpus() == 1) {
 409                 put_online_cpus();
 410                 return;
 411         }
 412
 413         /* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
 414         shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 415         if (shuffle_idle_cpu >= nr_cpu_ids)
 416                 shuffle_idle_cpu = -1;
 417         else
 418                 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
 419
 420         mutex_lock(&shuffle_task_mutex);
 421         list_for_each_entry(stp, &shuffle_task_list, st_l)
 422                 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
 423         mutex_unlock(&shuffle_task_mutex);
 424
 425         put_online_cpus();
 426 }
 427
 428 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 429  * system to become idle at a time and cut off its timer ticks. This is meant
 430  * to test the support for such tickless idle CPU in RCU.
 431  */
 432 static int torture_shuffle(void *arg)
 433 {
 434         VERBOSE_TOROUT_STRING("torture_shuffle task started");
 435         do {
 436                 schedule_timeout_interruptible(shuffle_interval);
 437                 torture_shuffle_tasks();
 438                 torture_shutdown_absorb("torture_shuffle");
 439         } while (!torture_must_stop());
 440         torture_kthread_stopping("torture_shuffle");
 441         return 0;
 442 }
 443
 444 /*
 445  * Start the shuffler, with shuffint in jiffies.
 446  */
 447 int torture_shuffle_init(long shuffint)
 448 {
 449         shuffle_interval = shuffint;
 450
 451         shuffle_idle_cpu = -1;
 452
 453         if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
 454                 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
 455                 return -ENOMEM;
 456         }
 457
 458         /* Create the shuffler thread */
 459         return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 460 }
 461 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 462
 463 /*
 464  * Stop the shuffling.
 465  */
 466 static void torture_shuffle_cleanup(void)
 467 {
 468         torture_shuffle_task_unregister_all();
 469         if (shuffler_task) {
 470                 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
 471                 kthread_stop(shuffler_task);
 472                 free_cpumask_var(shuffle_tmp_mask);
 473         }
 474         shuffler_task = NULL;
 475 }
 476
 477 /*
 478  * Variables for auto-shutdown.  This allows "lights out" torture runs
 479  * to be fully scripted.
 480  */
 481 static struct task_struct *shutdown_task;
 482 static ktime_t shutdown_time;           /* time to system shutdown. */
 483 static void (*torture_shutdown_hook)(void);
 484
 485 /*
 486  * Absorb kthreads into a kernel function that won't return, so that
 487  * they won't ever access module text or data again.
 488  */
 489 void torture_shutdown_absorb(const char *title)
 490 {
 491         while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 492                 pr_notice("torture thread %s parking due to system shutdown\n",
 493                           title);
 494                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 495         }
 496 }
 497 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 498
 499 /*
 500  * Cause the torture test to shutdown the system after the test has
 501  * run for the time specified by the shutdown_secs parameter.
 502  */
 503 static int torture_shutdown(void *arg)
 504 {
 505         ktime_t ktime_snap;
 506
 507         VERBOSE_TOROUT_STRING("torture_shutdown task started");
 508         ktime_snap = ktime_get();
 509         while (ktime_before(ktime_snap, shutdown_time) &&
 510                !torture_must_stop()) {
 511                 if (verbose)
 512                         pr_alert("%s" TORTURE_FLAG
 513                                  "torture_shutdown task: %llu ms remaining\n",
 514                                  torture_type,
 515                                  ktime_ms_delta(shutdown_time, ktime_snap));
 516                 set_current_state(TASK_INTERRUPTIBLE);
 517                 schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
 518                 ktime_snap = ktime_get();
 519         }
 520         if (torture_must_stop()) {
 521                 torture_kthread_stopping("torture_shutdown");
 522                 return 0;
 523         }
 524
 525         /* OK, shut down the system. */
 526
 527         VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
 528         shutdown_task = NULL;   /* Avoid self-kill deadlock. */
 529         if (torture_shutdown_hook)
 530                 torture_shutdown_hook();
 531         else
 532                 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 533         if (ftrace_dump_at_shutdown)
 534                 rcu_ftrace_dump(DUMP_ALL);
 535         kernel_power_off();     /* Shut down the system. */
 536         return 0;
 537 }
 538
 539 /*
 540  * Start up the shutdown task.
 541  */
 542 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 543 {
 544         torture_shutdown_hook = cleanup;
 545         if (ssecs > 0) {
 546                 shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
 547                 return torture_create_kthread(torture_shutdown, NULL,
 548                                              shutdown_task);
 549         }
 550         return 0;
 551 }
 552 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 553
 554 /*
 555  * Detect and respond to a system shutdown.
 556  */
 557 static int torture_shutdown_notify(struct notifier_block *unused1,
 558                                    unsigned long unused2, void *unused3)
 559 {
 560         mutex_lock(&fullstop_mutex);
 561         if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
 562                 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
 563                 WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
 564         } else {
 565                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 566         }
 567         mutex_unlock(&fullstop_mutex);
 568         return NOTIFY_DONE;
 569 }
 570
 571 static struct notifier_block torture_shutdown_nb = {
 572         .notifier_call = torture_shutdown_notify,
 573 };
 574
 575 /*
 576  * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 577  * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 578  */
 579 static void torture_shutdown_cleanup(void)
 580 {
 581         unregister_reboot_notifier(&torture_shutdown_nb);
 582         if (shutdown_task != NULL) {
 583                 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
 584                 kthread_stop(shutdown_task);
 585         }
 586         shutdown_task = NULL;
 587 }
 588
 589 /*
 590  * Variables for stuttering, which means to periodically pause and
 591  * restart testing in order to catch bugs that appear when load is
 592  * suddenly applied to or removed from the system.
 593  */
 594 static struct task_struct *stutter_task;
 595 static int stutter_pause_test;
 596 static int stutter;
 597 static int stutter_gap;
 598
 599 /*
 600  * Block until the stutter interval ends.  This must be called periodically
 601  * by all running kthreads that need to be subject to stuttering.
 602  */
 603 bool stutter_wait(const char *title)
 604 {
 605         int spt;
 606         bool ret = false;
 607
 608         cond_resched_tasks_rcu_qs();
 609         spt = READ_ONCE(stutter_pause_test);
 610         for (; spt; spt = READ_ONCE(stutter_pause_test)) {
 611                 ret = true;
 612                 if (spt == 1) {
 613                         schedule_timeout_interruptible(1);
 614                 } else if (spt == 2) {
 615                         while (READ_ONCE(stutter_pause_test))
 616                                 cond_resched();
 617                 } else {
 618                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 619                 }
 620                 torture_shutdown_absorb(title);
 621         }
 622         return ret;
 623 }
 624 EXPORT_SYMBOL_GPL(stutter_wait);
 625
 626 /*
 627  * Cause the torture test to "stutter", starting and stopping all
 628  * threads periodically.
 629  */
 630 static int torture_stutter(void *arg)
 631 {
 632         int wtime;
 633
 634         VERBOSE_TOROUT_STRING("torture_stutter task started");
 635         do {
 636                 if (!torture_must_stop() && stutter > 1) {
 637                         wtime = stutter;
 638                         if (stutter > HZ + 1) {
 639                                 WRITE_ONCE(stutter_pause_test, 1);
 640                                 wtime = stutter - HZ - 1;
 641                                 schedule_timeout_interruptible(wtime);
 642                                 wtime = HZ + 1;
 643                         }
 644                         WRITE_ONCE(stutter_pause_test, 2);
 645                         schedule_timeout_interruptible(wtime);
 646                 }
 647                 WRITE_ONCE(stutter_pause_test, 0);
 648                 if (!torture_must_stop())
 649                         schedule_timeout_interruptible(stutter_gap);
 650                 torture_shutdown_absorb("torture_stutter");
 651         } while (!torture_must_stop());
 652         torture_kthread_stopping("torture_stutter");
 653         return 0;
 654 }
 655
 656 /*
 657  * Initialize and kick off the torture_stutter kthread.
 658  */
 659 int torture_stutter_init(const int s, const int sgap)
 660 {
 661         stutter = s;
 662         stutter_gap = sgap;
 663         return torture_create_kthread(torture_stutter, NULL, stutter_task);
 664 }
 665 EXPORT_SYMBOL_GPL(torture_stutter_init);
 666
 667 /*
 668  * Cleanup after the torture_stutter kthread.
 669  */
 670 static void torture_stutter_cleanup(void)
 671 {
 672         if (!stutter_task)
 673                 return;
 674         VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
 675         kthread_stop(stutter_task);
 676         stutter_task = NULL;
 677 }
 678
 679 /*
 680  * Initialize torture module.  Please note that this is -not- invoked via
 681  * the usual module_init() mechanism, but rather by an explicit call from
 682  * the client torture module.  This call must be paired with a later
 683  * torture_init_end().
 684  *
 685  * The runnable parameter points to a flag that controls whether or not
 686  * the test is currently runnable.  If there is no such flag, pass in NULL.
 687  */
 688 bool torture_init_begin(char *ttype, int v)
 689 {
 690         mutex_lock(&fullstop_mutex);
 691         if (torture_type != NULL) {
 692                 pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 693                          ttype, torture_type);
 694                 pr_alert("torture_init_begin: One torture test at a time!\n");
 695                 mutex_unlock(&fullstop_mutex);
 696                 return false;
 697         }
 698         torture_type = ttype;
 699         verbose = v;
 700         fullstop = FULLSTOP_DONTSTOP;
 701         return true;
 702 }
 703 EXPORT_SYMBOL_GPL(torture_init_begin);
 704
 705 /*
 706  * Tell the torture module that initialization is complete.
 707  */
 708 void torture_init_end(void)
 709 {
 710         mutex_unlock(&fullstop_mutex);
 711         register_reboot_notifier(&torture_shutdown_nb);
 712 }
 713 EXPORT_SYMBOL_GPL(torture_init_end);
 714
 715 /*
 716  * Clean up torture module.  Please note that this is -not- invoked via
 717  * the usual module_exit() mechanism, but rather by an explicit call from
 718  * the client torture module.  Returns true if a race with system shutdown
 719  * is detected, otherwise, all kthreads started by functions in this file
 720  * will be shut down.
 721  *
 722  * This must be called before the caller starts shutting down its own
 723  * kthreads.
 724  *
 725  * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 726  * in order to correctly perform the cleanup. They are separated because
 727  * threads can still need to reference the torture_type type, thus nullify
 728  * only after completing all other relevant calls.
 729  */
 730 bool torture_cleanup_begin(void)
 731 {
 732         mutex_lock(&fullstop_mutex);
 733         if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 734                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 735                 mutex_unlock(&fullstop_mutex);
 736                 schedule_timeout_uninterruptible(10);
 737                 return true;
 738         }
 739         WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
 740         mutex_unlock(&fullstop_mutex);
 741         torture_shutdown_cleanup();
 742         torture_shuffle_cleanup();
 743         torture_stutter_cleanup();
 744         torture_onoff_cleanup();
 745         return false;
 746 }
 747 EXPORT_SYMBOL_GPL(torture_cleanup_begin);
 748
 749 void torture_cleanup_end(void)
 750 {
 751         mutex_lock(&fullstop_mutex);
 752         torture_type = NULL;
 753         mutex_unlock(&fullstop_mutex);
 754 }
 755 EXPORT_SYMBOL_GPL(torture_cleanup_end);
 756
 757 /*
 758  * Is it time for the current torture test to stop?
 759  */
 760 bool torture_must_stop(void)
 761 {
 762         return torture_must_stop_irq() || kthread_should_stop();
 763 }
 764 EXPORT_SYMBOL_GPL(torture_must_stop);
 765
 766 /*
 767  * Is it time for the current torture test to stop?  This is the irq-safe
 768  * version, hence no check for kthread_should_stop().
 769  */
 770 bool torture_must_stop_irq(void)
 771 {
 772         return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 773 }
 774 EXPORT_SYMBOL_GPL(torture_must_stop_irq);
 775
 776 /*
 777  * Each kthread must wait for kthread_should_stop() before returning from
 778  * its top-level function, otherwise segfaults ensue.  This function
 779  * prints a "stopping" message and waits for kthread_should_stop(), and
 780  * should be called from all torture kthreads immediately prior to
 781  * returning.
 782  */
 783 void torture_kthread_stopping(char *title)
 784 {
 785         char buf[128];
 786
 787         snprintf(buf, sizeof(buf), "Stopping %s", title);
 788         VERBOSE_TOROUT_STRING(buf);
 789         while (!kthread_should_stop()) {
 790                 torture_shutdown_absorb(title);
 791                 schedule_timeout_uninterruptible(1);
 792         }
 793 }
 794 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
 795
 796 /*
 797  * Create a generic torture kthread that is immediately runnable.  If you
 798  * need the kthread to be stopped so that you can do something to it before
 799  * it starts, you will need to open-code your own.
 800  */
 801 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 802                             char *f, struct task_struct **tp)
 803 {
 804         int ret = 0;
 805
 806         VERBOSE_TOROUT_STRING(m);
 807         *tp = kthread_run(fn, arg, "%s", s);
 808         if (IS_ERR(*tp)) {
 809                 ret = PTR_ERR(*tp);
 810                 VERBOSE_TOROUT_ERRSTRING(f);
 811                 *tp = NULL;
 812         }
 813         torture_shuffle_task_register(*tp);
 814         return ret;
 815 }
 816 EXPORT_SYMBOL_GPL(_torture_create_kthread);
 817
 818 /*
 819  * Stop a generic kthread, emitting a message.
 820  */
 821 void _torture_stop_kthread(char *m, struct task_struct **tp)
 822 {
 823         if (*tp == NULL)
 824                 return;
 825         VERBOSE_TOROUT_STRING(m);
 826         kthread_stop(*tp);
 827         *tp = NULL;
 828 }
 829 EXPORT_SYMBOL_GPL(_torture_stop_kthread);