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         int ret = 0;
 184
 185 #ifdef CONFIG_HOTPLUG_CPU
 186         onoff_holdoff = ooholdoff;
 187         onoff_interval = oointerval;
 188         if (onoff_interval <= 0)
 189                 return 0;
 190         ret = torture_create_kthread(torture_onoff, NULL, onoff_task);
 191 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 192         return ret;
 193 }
 194 EXPORT_SYMBOL_GPL(torture_onoff_init);
 195
 196 /*
 197  * Clean up after online/offline testing.
 198  */
 199 static void torture_onoff_cleanup(void)
 200 {
 201 #ifdef CONFIG_HOTPLUG_CPU
 202         if (onoff_task == NULL)
 203                 return;
 204         VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
 205         kthread_stop(onoff_task);
 206         onoff_task = NULL;
 207 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 208 }
 209 EXPORT_SYMBOL_GPL(torture_onoff_cleanup);
 210
 211 /*
 212  * Print online/offline testing statistics.
 213  */
 214 void torture_onoff_stats(void)
 215 {
 216 #ifdef CONFIG_HOTPLUG_CPU
 217         pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
 218                 n_online_successes, n_online_attempts,
 219                 n_offline_successes, n_offline_attempts,
 220                 min_online, max_online,
 221                 min_offline, max_offline,
 222                 sum_online, sum_offline, HZ);
 223 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 224 }
 225 EXPORT_SYMBOL_GPL(torture_onoff_stats);
 226
 227 /*
 228  * Were all the online/offline operations successful?
 229  */
 230 bool torture_onoff_failures(void)
 231 {
 232 #ifdef CONFIG_HOTPLUG_CPU
 233         return n_online_successes != n_online_attempts ||
 234                n_offline_successes != n_offline_attempts;
 235 #else /* #ifdef CONFIG_HOTPLUG_CPU */
 236         return false;
 237 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 238 }
 239 EXPORT_SYMBOL_GPL(torture_onoff_failures);
 240
 241 #define TORTURE_RANDOM_MULT     39916801  /* prime */
 242 #define TORTURE_RANDOM_ADD      479001701 /* prime */
 243 #define TORTURE_RANDOM_REFRESH  10000
 244
 245 /*
 246  * Crude but fast random-number generator.  Uses a linear congruential
 247  * generator, with occasional help from cpu_clock().
 248  */
 249 unsigned long
 250 torture_random(struct torture_random_state *trsp)
 251 {
 252         if (--trsp->trs_count < 0) {
 253                 trsp->trs_state += (unsigned long)local_clock();
 254                 trsp->trs_count = TORTURE_RANDOM_REFRESH;
 255         }
 256         trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
 257                 TORTURE_RANDOM_ADD;
 258         return swahw32(trsp->trs_state);
 259 }
 260 EXPORT_SYMBOL_GPL(torture_random);
 261
 262 /*
 263  * Variables for shuffling.  The idea is to ensure that each CPU stays
 264  * idle for an extended period to test interactions with dyntick idle,
 265  * as well as interactions with any per-CPU varibles.
 266  */
 267 struct shuffle_task {
 268         struct list_head st_l;
 269         struct task_struct *st_t;
 270 };
 271
 272 static long shuffle_interval;   /* In jiffies. */
 273 static struct task_struct *shuffler_task;
 274 static cpumask_var_t shuffle_tmp_mask;
 275 static int shuffle_idle_cpu;    /* Force all torture tasks off this CPU */
 276 static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
 277 static DEFINE_MUTEX(shuffle_task_mutex);
 278
 279 /*
 280  * Register a task to be shuffled.  If there is no memory, just splat
 281  * and don't bother registering.
 282  */
 283 void torture_shuffle_task_register(struct task_struct *tp)
 284 {
 285         struct shuffle_task *stp;
 286
 287         if (WARN_ON_ONCE(tp == NULL))
 288                 return;
 289         stp = kmalloc(sizeof(*stp), GFP_KERNEL);
 290         if (WARN_ON_ONCE(stp == NULL))
 291                 return;
 292         stp->st_t = tp;
 293         mutex_lock(&shuffle_task_mutex);
 294         list_add(&stp->st_l, &shuffle_task_list);
 295         mutex_unlock(&shuffle_task_mutex);
 296 }
 297 EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
 298
 299 /*
 300  * Unregister all tasks, for example, at the end of the torture run.
 301  */
 302 static void torture_shuffle_task_unregister_all(void)
 303 {
 304         struct shuffle_task *stp;
 305         struct shuffle_task *p;
 306
 307         mutex_lock(&shuffle_task_mutex);
 308         list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
 309                 list_del(&stp->st_l);
 310                 kfree(stp);
 311         }
 312         mutex_unlock(&shuffle_task_mutex);
 313 }
 314
 315 /* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 316  * A special case is when shuffle_idle_cpu = -1, in which case we allow
 317  * the tasks to run on all CPUs.
 318  */
 319 static void torture_shuffle_tasks(void)
 320 {
 321         struct shuffle_task *stp;
 322
 323         cpumask_setall(shuffle_tmp_mask);
 324         get_online_cpus();
 325
 326         /* No point in shuffling if there is only one online CPU (ex: UP) */
 327         if (num_online_cpus() == 1) {
 328                 put_online_cpus();
 329                 return;
 330         }
 331
 332         /* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
 333         shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
 334         if (shuffle_idle_cpu >= nr_cpu_ids)
 335                 shuffle_idle_cpu = -1;
 336         else
 337                 cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
 338
 339         mutex_lock(&shuffle_task_mutex);
 340         list_for_each_entry(stp, &shuffle_task_list, st_l)
 341                 set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
 342         mutex_unlock(&shuffle_task_mutex);
 343
 344         put_online_cpus();
 345 }
 346
 347 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 348  * system to become idle at a time and cut off its timer ticks. This is meant
 349  * to test the support for such tickless idle CPU in RCU.
 350  */
 351 static int torture_shuffle(void *arg)
 352 {
 353         VERBOSE_TOROUT_STRING("torture_shuffle task started");
 354         do {
 355                 schedule_timeout_interruptible(shuffle_interval);
 356                 torture_shuffle_tasks();
 357                 torture_shutdown_absorb("torture_shuffle");
 358         } while (!torture_must_stop());
 359         torture_kthread_stopping("torture_shuffle");
 360         return 0;
 361 }
 362
 363 /*
 364  * Start the shuffler, with shuffint in jiffies.
 365  */
 366 int torture_shuffle_init(long shuffint)
 367 {
 368         shuffle_interval = shuffint;
 369
 370         shuffle_idle_cpu = -1;
 371
 372         if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
 373                 VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
 374                 return -ENOMEM;
 375         }
 376
 377         /* Create the shuffler thread */
 378         return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 379 }
 380 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 381
 382 /*
 383  * Stop the shuffling.
 384  */
 385 static void torture_shuffle_cleanup(void)
 386 {
 387         torture_shuffle_task_unregister_all();
 388         if (shuffler_task) {
 389                 VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
 390                 kthread_stop(shuffler_task);
 391                 free_cpumask_var(shuffle_tmp_mask);
 392         }
 393         shuffler_task = NULL;
 394 }
 395 EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
 396
 397 /*
 398  * Variables for auto-shutdown.  This allows "lights out" torture runs
 399  * to be fully scripted.
 400  */
 401 static int shutdown_secs;               /* desired test duration in seconds. */
 402 static struct task_struct *shutdown_task;
 403 static unsigned long shutdown_time;     /* jiffies to system shutdown. */
 404 static void (*torture_shutdown_hook)(void);
 405
 406 /*
 407  * Absorb kthreads into a kernel function that won't return, so that
 408  * they won't ever access module text or data again.
 409  */
 410 void torture_shutdown_absorb(const char *title)
 411 {
 412         while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 413                 pr_notice("torture thread %s parking due to system shutdown\n",
 414                           title);
 415                 schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 416         }
 417 }
 418 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 419
 420 /*
 421  * Cause the torture test to shutdown the system after the test has
 422  * run for the time specified by the shutdown_secs parameter.
 423  */
 424 static int torture_shutdown(void *arg)
 425 {
 426         long delta;
 427         unsigned long jiffies_snap;
 428
 429         VERBOSE_TOROUT_STRING("torture_shutdown task started");
 430         jiffies_snap = jiffies;
 431         while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
 432                !torture_must_stop()) {
 433                 delta = shutdown_time - jiffies_snap;
 434                 if (verbose)
 435                         pr_alert("%s" TORTURE_FLAG
 436                                  "torture_shutdown task: %lu jiffies remaining\n",
 437                                  torture_type, delta);
 438                 schedule_timeout_interruptible(delta);
 439                 jiffies_snap = jiffies;
 440         }
 441         if (torture_must_stop()) {
 442                 torture_kthread_stopping("torture_shutdown");
 443                 return 0;
 444         }
 445
 446         /* OK, shut down the system. */
 447
 448         VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
 449         shutdown_task = NULL;   /* Avoid self-kill deadlock. */
 450         if (torture_shutdown_hook)
 451                 torture_shutdown_hook();
 452         else
 453                 VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 454         ftrace_dump(DUMP_ALL);
 455         kernel_power_off();     /* Shut down the system. */
 456         return 0;
 457 }
 458
 459 /*
 460  * Start up the shutdown task.
 461  */
 462 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 463 {
 464         int ret = 0;
 465
 466         shutdown_secs = ssecs;
 467         torture_shutdown_hook = cleanup;
 468         if (shutdown_secs > 0) {
 469                 shutdown_time = jiffies + shutdown_secs * HZ;
 470                 ret = torture_create_kthread(torture_shutdown, NULL,
 471                                              shutdown_task);
 472         }
 473         return ret;
 474 }
 475 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 476
 477 /*
 478  * Detect and respond to a system shutdown.
 479  */
 480 static int torture_shutdown_notify(struct notifier_block *unused1,
 481                                    unsigned long unused2, void *unused3)
 482 {
 483         mutex_lock(&fullstop_mutex);
 484         if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
 485                 VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
 486                 WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
 487         } else {
 488                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 489         }
 490         mutex_unlock(&fullstop_mutex);
 491         return NOTIFY_DONE;
 492 }
 493
 494 static struct notifier_block torture_shutdown_nb = {
 495         .notifier_call = torture_shutdown_notify,
 496 };
 497
 498 /*
 499  * Shut down the shutdown task.  Say what???  Heh!  This can happen if
 500  * the torture module gets an rmmod before the shutdown time arrives.  ;-)
 501  */
 502 static void torture_shutdown_cleanup(void)
 503 {
 504         unregister_reboot_notifier(&torture_shutdown_nb);
 505         if (shutdown_task != NULL) {
 506                 VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
 507                 kthread_stop(shutdown_task);
 508         }
 509         shutdown_task = NULL;
 510 }
 511
 512 /*
 513  * Variables for stuttering, which means to periodically pause and
 514  * restart testing in order to catch bugs that appear when load is
 515  * suddenly applied to or removed from the system.
 516  */
 517 static struct task_struct *stutter_task;
 518 static int stutter_pause_test;
 519 static int stutter;
 520
 521 /*
 522  * Block until the stutter interval ends.  This must be called periodically
 523  * by all running kthreads that need to be subject to stuttering.
 524  */
 525 void stutter_wait(const char *title)
 526 {
 527         cond_resched_rcu_qs();
 528         while (READ_ONCE(stutter_pause_test) ||
 529                (torture_runnable && !READ_ONCE(*torture_runnable))) {
 530                 if (stutter_pause_test)
 531                         if (READ_ONCE(stutter_pause_test) == 1)
 532                                 schedule_timeout_interruptible(1);
 533                         else
 534                                 while (READ_ONCE(stutter_pause_test))
 535                                         cond_resched();
 536                 else
 537                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 538                 torture_shutdown_absorb(title);
 539         }
 540 }
 541 EXPORT_SYMBOL_GPL(stutter_wait);
 542
 543 /*
 544  * Cause the torture test to "stutter", starting and stopping all
 545  * threads periodically.
 546  */
 547 static int torture_stutter(void *arg)
 548 {
 549         VERBOSE_TOROUT_STRING("torture_stutter task started");
 550         do {
 551                 if (!torture_must_stop()) {
 552                         if (stutter > 1) {
 553                                 schedule_timeout_interruptible(stutter - 1);
 554                                 WRITE_ONCE(stutter_pause_test, 2);
 555                         }
 556                         schedule_timeout_interruptible(1);
 557                         WRITE_ONCE(stutter_pause_test, 1);
 558                 }
 559                 if (!torture_must_stop())
 560                         schedule_timeout_interruptible(stutter);
 561                 WRITE_ONCE(stutter_pause_test, 0);
 562                 torture_shutdown_absorb("torture_stutter");
 563         } while (!torture_must_stop());
 564         torture_kthread_stopping("torture_stutter");
 565         return 0;
 566 }
 567
 568 /*
 569  * Initialize and kick off the torture_stutter kthread.
 570  */
 571 int torture_stutter_init(int s)
 572 {
 573         int ret;
 574
 575         stutter = s;
 576         ret = torture_create_kthread(torture_stutter, NULL, stutter_task);
 577         return ret;
 578 }
 579 EXPORT_SYMBOL_GPL(torture_stutter_init);
 580
 581 /*
 582  * Cleanup after the torture_stutter kthread.
 583  */
 584 static void torture_stutter_cleanup(void)
 585 {
 586         if (!stutter_task)
 587                 return;
 588         VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
 589         kthread_stop(stutter_task);
 590         stutter_task = NULL;
 591 }
 592
 593 /*
 594  * Initialize torture module.  Please note that this is -not- invoked via
 595  * the usual module_init() mechanism, but rather by an explicit call from
 596  * the client torture module.  This call must be paired with a later
 597  * torture_init_end().
 598  *
 599  * The runnable parameter points to a flag that controls whether or not
 600  * the test is currently runnable.  If there is no such flag, pass in NULL.
 601  */
 602 bool torture_init_begin(char *ttype, bool v, int *runnable)
 603 {
 604         mutex_lock(&fullstop_mutex);
 605         if (torture_type != NULL) {
 606                 pr_alert("torture_init_begin: Refusing %s init: %s running.\n",
 607                          ttype, torture_type);
 608                 pr_alert("torture_init_begin: One torture test at a time!\n");
 609                 mutex_unlock(&fullstop_mutex);
 610                 return false;
 611         }
 612         torture_type = ttype;
 613         verbose = v;
 614         torture_runnable = runnable;
 615         fullstop = FULLSTOP_DONTSTOP;
 616         return true;
 617 }
 618 EXPORT_SYMBOL_GPL(torture_init_begin);
 619
 620 /*
 621  * Tell the torture module that initialization is complete.
 622  */
 623 void torture_init_end(void)
 624 {
 625         mutex_unlock(&fullstop_mutex);
 626         register_reboot_notifier(&torture_shutdown_nb);
 627 }
 628 EXPORT_SYMBOL_GPL(torture_init_end);
 629
 630 /*
 631  * Clean up torture module.  Please note that this is -not- invoked via
 632  * the usual module_exit() mechanism, but rather by an explicit call from
 633  * the client torture module.  Returns true if a race with system shutdown
 634  * is detected, otherwise, all kthreads started by functions in this file
 635  * will be shut down.
 636  *
 637  * This must be called before the caller starts shutting down its own
 638  * kthreads.
 639  *
 640  * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
 641  * in order to correctly perform the cleanup. They are separated because
 642  * threads can still need to reference the torture_type type, thus nullify
 643  * only after completing all other relevant calls.
 644  */
 645 bool torture_cleanup_begin(void)
 646 {
 647         mutex_lock(&fullstop_mutex);
 648         if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
 649                 pr_warn("Concurrent rmmod and shutdown illegal!\n");
 650                 mutex_unlock(&fullstop_mutex);
 651                 schedule_timeout_uninterruptible(10);
 652                 return true;
 653         }
 654         WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
 655         mutex_unlock(&fullstop_mutex);
 656         torture_shutdown_cleanup();
 657         torture_shuffle_cleanup();
 658         torture_stutter_cleanup();
 659         torture_onoff_cleanup();
 660         return false;
 661 }
 662 EXPORT_SYMBOL_GPL(torture_cleanup_begin);
 663
 664 void torture_cleanup_end(void)
 665 {
 666         mutex_lock(&fullstop_mutex);
 667         torture_type = NULL;
 668         mutex_unlock(&fullstop_mutex);
 669 }
 670 EXPORT_SYMBOL_GPL(torture_cleanup_end);
 671
 672 /*
 673  * Is it time for the current torture test to stop?
 674  */
 675 bool torture_must_stop(void)
 676 {
 677         return torture_must_stop_irq() || kthread_should_stop();
 678 }
 679 EXPORT_SYMBOL_GPL(torture_must_stop);
 680
 681 /*
 682  * Is it time for the current torture test to stop?  This is the irq-safe
 683  * version, hence no check for kthread_should_stop().
 684  */
 685 bool torture_must_stop_irq(void)
 686 {
 687         return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 688 }
 689 EXPORT_SYMBOL_GPL(torture_must_stop_irq);
 690
 691 /*
 692  * Each kthread must wait for kthread_should_stop() before returning from
 693  * its top-level function, otherwise segfaults ensue.  This function
 694  * prints a "stopping" message and waits for kthread_should_stop(), and
 695  * should be called from all torture kthreads immediately prior to
 696  * returning.
 697  */
 698 void torture_kthread_stopping(char *title)
 699 {
 700         char buf[128];
 701
 702         snprintf(buf, sizeof(buf), "Stopping %s", title);
 703         VERBOSE_TOROUT_STRING(buf);
 704         while (!kthread_should_stop()) {
 705                 torture_shutdown_absorb(title);
 706                 schedule_timeout_uninterruptible(1);
 707         }
 708 }
 709 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
 710
 711 /*
 712  * Create a generic torture kthread that is immediately runnable.  If you
 713  * need the kthread to be stopped so that you can do something to it before
 714  * it starts, you will need to open-code your own.
 715  */
 716 int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
 717                             char *f, struct task_struct **tp)
 718 {
 719         int ret = 0;
 720
 721         VERBOSE_TOROUT_STRING(m);
 722         *tp = kthread_run(fn, arg, "%s", s);
 723         if (IS_ERR(*tp)) {
 724                 ret = PTR_ERR(*tp);
 725                 VERBOSE_TOROUT_ERRSTRING(f);
 726                 *tp = NULL;
 727         }
 728         torture_shuffle_task_register(*tp);
 729         return ret;
 730 }
 731 EXPORT_SYMBOL_GPL(_torture_create_kthread);
 732
 733 /*
 734  * Stop a generic kthread, emitting a message.
 735  */
 736 void _torture_stop_kthread(char *m, struct task_struct **tp)
 737 {
 738         if (*tp == NULL)
 739                 return;
 740         VERBOSE_TOROUT_STRING(m);
 741         kthread_stop(*tp);
 742         *tp = NULL;
 743 }
 744 EXPORT_SYMBOL_GPL(_torture_stop_kthread);