libcfs/libcfs/watchdog.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.gnu.org/licenses/gpl-2.0.html
  19  *
  20  * GPL HEADER END
  21  */
  22 /*
  23  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  24  * Use is subject to license terms.
  25  *
  26  * Copyright (c) 2012, 2014, Intel Corporation.
  27  */
  28 /*
  29  * This file is part of Lustre, http://www.lustre.org/
  30  * Lustre is a trademark of Sun Microsystems, Inc.
  31  *
  32  * libcfs/libcfs/watchdog.c
  33  *
  34  * Author: Jacob Berkman <jacob@clusterfs.com>
  35  */
  36
  37 #define DEBUG_SUBSYSTEM S_LNET
  38
  39 #include <linux/kthread.h>
  40 #include <libcfs/libcfs.h>
  41 #include "tracefile.h"
  42
  43 struct lc_watchdog {
  44         spinlock_t              lcw_lock;       /* check or change lcw_list */
  45         int                     lcw_refcount;   /* must hold lcw_pending_timers_lock */
  46         struct timer_list       lcw_timer;      /* kernel timer */
  47         struct list_head        lcw_list;       /* chain on pending list */
  48         ktime_t                 lcw_last_touched;/* last touched stamp */
  49         struct task_struct     *lcw_task;       /* owner task */
  50         void                    (*lcw_callback)(pid_t, void *);
  51         void                    *lcw_data;
  52
  53         pid_t                   lcw_pid;
  54
  55         enum {
  56                 LC_WATCHDOG_DISABLED,
  57                 LC_WATCHDOG_ENABLED,
  58                 LC_WATCHDOG_EXPIRED
  59         } lcw_state;
  60 };
  61
  62 #ifdef WITH_WATCHDOG
  63 /*
  64  * The dispatcher will complete lcw_start_completion when it starts,
  65  * and lcw_stop_completion when it exits.
  66  * Wake lcw_event_waitq to signal timer callback dispatches.
  67  */
  68 static struct completion lcw_start_completion;
  69 static struct completion  lcw_stop_completion;
  70 static wait_queue_head_t lcw_event_waitq;
  71
  72 /*
  73  * Set this and wake lcw_event_waitq to stop the dispatcher.
  74  */
  75 enum {
  76         LCW_FLAG_STOP = 0
  77 };
  78 static unsigned long lcw_flags = 0;
  79
  80 /*
  81  * Number of outstanding watchdogs.
  82  * When it hits 1, we start the dispatcher.
  83  * When it hits 0, we stop the dispatcher.
  84  */
  85 static __u32         lcw_refcount = 0;
  86 static DEFINE_MUTEX(lcw_refcount_mutex);
  87
  88 /*
  89  * List of timers that have fired that need their callbacks run by the
  90  * dispatcher.
  91  */
  92 /* BH lock! */
  93 static DEFINE_SPINLOCK(lcw_pending_timers_lock);
  94 static struct list_head lcw_pending_timers = LIST_HEAD_INIT(lcw_pending_timers);
  95
  96 /* Last time a watchdog expired */
  97 static time64_t lcw_last_watchdog_time;
  98 static int lcw_recent_watchdog_count;
  99
 100 static void
 101 lcw_dump(struct lc_watchdog *lcw)
 102 {
 103         ENTRY;
 104         rcu_read_lock();
 105        if (lcw->lcw_task == NULL) {
 106                 LCONSOLE_WARN("Process %d was not found in the task "
 107                               "list; watchdog callback may be incomplete\n",
 108                               (int)lcw->lcw_pid);
 109         } else {
 110                 libcfs_debug_dumpstack(lcw->lcw_task);
 111         }
 112
 113         rcu_read_unlock();
 114         EXIT;
 115 }
 116
 117 static void lcw_cb(uintptr_t data)
 118 {
 119         struct lc_watchdog *lcw = (struct lc_watchdog *)data;
 120         ENTRY;
 121
 122         if (lcw->lcw_state != LC_WATCHDOG_ENABLED) {
 123                 EXIT;
 124                 return;
 125         }
 126
 127         lcw->lcw_state = LC_WATCHDOG_EXPIRED;
 128
 129         spin_lock_bh(&lcw->lcw_lock);
 130         LASSERT(list_empty(&lcw->lcw_list));
 131
 132         spin_lock_bh(&lcw_pending_timers_lock);
 133         lcw->lcw_refcount++; /* +1 for pending list */
 134         list_add(&lcw->lcw_list, &lcw_pending_timers);
 135         wake_up(&lcw_event_waitq);
 136
 137         spin_unlock_bh(&lcw_pending_timers_lock);
 138         spin_unlock_bh(&lcw->lcw_lock);
 139         EXIT;
 140 }
 141
 142 static int is_watchdog_fired(void)
 143 {
 144         int rc;
 145
 146         if (test_bit(LCW_FLAG_STOP, &lcw_flags))
 147                 return 1;
 148
 149         spin_lock_bh(&lcw_pending_timers_lock);
 150         rc = !list_empty(&lcw_pending_timers);
 151         spin_unlock_bh(&lcw_pending_timers_lock);
 152         return rc;
 153 }
 154
 155 static void lcw_dump_stack(struct lc_watchdog *lcw)
 156 {
 157         time64_t current_time = ktime_get_seconds();
 158         struct timespec64 timediff;
 159         time64_t delta_time;
 160
 161         timediff = ktime_to_timespec64(ktime_sub(ktime_get(),
 162                                        lcw->lcw_last_touched));
 163
 164         /* LU-9235: Don't dump stack if the thread is just touched. */
 165         if (timediff.tv_sec == 0)
 166                 return;
 167
 168         /*
 169          * Check to see if we should throttle the watchdog timer to avoid
 170          * too many dumps going to the console thus triggering an NMI.
 171          */
 172         delta_time = current_time - lcw_last_watchdog_time;
 173         if (delta_time < libcfs_watchdog_ratelimit &&
 174             lcw_recent_watchdog_count > 3) {
 175                 LCONSOLE_WARN("Service thread pid %u was inactive for %lu.%.02lus. Watchdog stack traces are limited to 3 per %d seconds, skipping this one.\n",
 176                               (int)lcw->lcw_pid,
 177                               timediff.tv_sec,
 178                               timediff.tv_nsec / (NSEC_PER_SEC / 100),
 179                               libcfs_watchdog_ratelimit);
 180         } else {
 181                 if (delta_time < libcfs_watchdog_ratelimit) {
 182                         lcw_recent_watchdog_count++;
 183                 } else {
 184                         memcpy(&lcw_last_watchdog_time, &current_time,
 185                                sizeof(current_time));
 186                         lcw_recent_watchdog_count = 0;
 187                 }
 188
 189                 LCONSOLE_WARN("Service thread pid %u was inactive for %lu.%.02lus. The thread might be hung, or it might only be slow and will resume later. Dumping the stack trace for debugging purposes:\n",
 190                               (int)lcw->lcw_pid,
 191                               timediff.tv_sec,
 192                               timediff.tv_nsec / (NSEC_PER_SEC / 100));
 193                 lcw_dump(lcw);
 194         }
 195 }
 196
 197 /*
 198  * Provided watchdog handlers
 199  */
 200
 201 static void lc_watchdog_dumplog(pid_t pid, void *data)
 202 {
 203         libcfs_debug_dumplog_internal((void *)((uintptr_t)pid));
 204 }
 205
 206 static int lcw_dispatch_main(void *data)
 207 {
 208         int                 rc = 0;
 209         struct lc_watchdog *lcw;
 210         struct list_head zombies = LIST_HEAD_INIT(zombies);
 211
 212         ENTRY;
 213
 214         complete(&lcw_start_completion);
 215
 216         while (1) {
 217                 int dumplog = 1;
 218
 219                 rc = wait_event_interruptible(lcw_event_waitq,
 220                                               is_watchdog_fired());
 221                 CDEBUG(D_INFO, "Watchdog got woken up...\n");
 222                 if (test_bit(LCW_FLAG_STOP, &lcw_flags)) {
 223                         CDEBUG(D_INFO, "LCW_FLAG_STOP set, shutting down...\n");
 224
 225                         spin_lock_bh(&lcw_pending_timers_lock);
 226                         rc = !list_empty(&lcw_pending_timers);
 227                         spin_unlock_bh(&lcw_pending_timers_lock);
 228                         if (rc) {
 229                                 CERROR("pending timers list was not empty at "
 230                                        "time of watchdog dispatch shutdown\n");
 231                         }
 232                         break;
 233                 }
 234
 235                 spin_lock_bh(&lcw_pending_timers_lock);
 236                 while (!list_empty(&lcw_pending_timers)) {
 237                         int is_dumplog;
 238
 239                         lcw = list_entry(lcw_pending_timers.next,
 240                                          struct lc_watchdog, lcw_list);
 241                         /* +1 ref for callback to make sure lwc wouldn't be
 242                          * deleted after releasing lcw_pending_timers_lock */
 243                         lcw->lcw_refcount++;
 244                         spin_unlock_bh(&lcw_pending_timers_lock);
 245
 246                         /* lock ordering */
 247                         spin_lock_bh(&lcw->lcw_lock);
 248                         spin_lock_bh(&lcw_pending_timers_lock);
 249
 250                         if (list_empty(&lcw->lcw_list)) {
 251                                 /* already removed from pending list */
 252                                 lcw->lcw_refcount--; /* -1 ref for callback */
 253                                 if (lcw->lcw_refcount == 0)
 254                                         list_add(&lcw->lcw_list, &zombies);
 255                                 spin_unlock_bh(&lcw->lcw_lock);
 256                                 /* still hold lcw_pending_timers_lock */
 257                                 continue;
 258                         }
 259
 260                         list_del_init(&lcw->lcw_list);
 261                         lcw->lcw_refcount--; /* -1 ref for pending list */
 262
 263                         spin_unlock_bh(&lcw_pending_timers_lock);
 264                         spin_unlock_bh(&lcw->lcw_lock);
 265
 266                         CDEBUG(D_INFO, "found lcw for pid %d\n",
 267                                lcw->lcw_pid);
 268                         lcw_dump_stack(lcw);
 269
 270                         is_dumplog = lcw->lcw_callback == lc_watchdog_dumplog;
 271                         if (lcw->lcw_state != LC_WATCHDOG_DISABLED &&
 272                             (dumplog || !is_dumplog)) {
 273                                 lcw->lcw_callback(lcw->lcw_pid, lcw->lcw_data);
 274                                 if (dumplog && is_dumplog)
 275                                         dumplog = 0;
 276                         }
 277
 278                         spin_lock_bh(&lcw_pending_timers_lock);
 279                         lcw->lcw_refcount--; /* -1 ref for callback */
 280                         if (lcw->lcw_refcount == 0)
 281                                 list_add(&lcw->lcw_list, &zombies);
 282                 }
 283                 spin_unlock_bh(&lcw_pending_timers_lock);
 284
 285                 while (!list_empty(&zombies)) {
 286                         lcw = list_entry(zombies.next,
 287                                              struct lc_watchdog, lcw_list);
 288                         list_del_init(&lcw->lcw_list);
 289                         LIBCFS_FREE(lcw, sizeof(*lcw));
 290                 }
 291         }
 292
 293         complete(&lcw_stop_completion);
 294
 295         RETURN(rc);
 296 }
 297
 298 static void lcw_dispatch_start(void)
 299 {
 300         struct task_struct *task;
 301
 302         ENTRY;
 303         LASSERT(lcw_refcount == 1);
 304
 305         init_completion(&lcw_stop_completion);
 306         init_completion(&lcw_start_completion);
 307         init_waitqueue_head(&lcw_event_waitq);
 308
 309         CDEBUG(D_INFO, "starting dispatch thread\n");
 310         task = kthread_run(lcw_dispatch_main, NULL, "lc_watchdogd");
 311         if (IS_ERR(task)) {
 312                 CERROR("error spawning watchdog dispatch thread: %ld\n",
 313                         PTR_ERR(task));
 314                 EXIT;
 315                 return;
 316         }
 317         wait_for_completion(&lcw_start_completion);
 318         CDEBUG(D_INFO, "watchdog dispatcher initialization complete.\n");
 319
 320         EXIT;
 321 }
 322
 323 static void lcw_dispatch_stop(void)
 324 {
 325         ENTRY;
 326         LASSERT(lcw_refcount == 0);
 327
 328         CDEBUG(D_INFO, "trying to stop watchdog dispatcher.\n");
 329
 330         set_bit(LCW_FLAG_STOP, &lcw_flags);
 331         wake_up(&lcw_event_waitq);
 332
 333         wait_for_completion(&lcw_stop_completion);
 334
 335         CDEBUG(D_INFO, "watchdog dispatcher has shut down.\n");
 336
 337         EXIT;
 338 }
 339
 340 struct lc_watchdog *lc_watchdog_add(int timeout,
 341                                     void (*callback)(pid_t, void *),
 342                                     void *data)
 343 {
 344         struct lc_watchdog *lcw = NULL;
 345         ENTRY;
 346
 347         LIBCFS_ALLOC(lcw, sizeof(*lcw));
 348         if (lcw == NULL) {
 349                 CDEBUG(D_INFO, "Could not allocate new lc_watchdog\n");
 350                 RETURN(ERR_PTR(-ENOMEM));
 351         }
 352
 353         spin_lock_init(&lcw->lcw_lock);
 354         lcw->lcw_refcount = 1; /* refcount for owner */
 355         lcw->lcw_task     = current;
 356         lcw->lcw_pid      = current_pid();
 357         lcw->lcw_callback = (callback != NULL) ? callback : lc_watchdog_dumplog;
 358         lcw->lcw_data     = data;
 359         lcw->lcw_state    = LC_WATCHDOG_DISABLED;
 360
 361         INIT_LIST_HEAD(&lcw->lcw_list);
 362         setup_timer(&lcw->lcw_timer, lcw_cb, (unsigned long)lcw);
 363
 364         mutex_lock(&lcw_refcount_mutex);
 365         if (++lcw_refcount == 1)
 366                 lcw_dispatch_start();
 367         mutex_unlock(&lcw_refcount_mutex);
 368
 369         /* Keep this working in case we enable them by default */
 370         if (lcw->lcw_state == LC_WATCHDOG_ENABLED) {
 371                 lcw->lcw_last_touched = ktime_get();
 372                 mod_timer(&lcw->lcw_timer, cfs_time_seconds(timeout) +
 373                           jiffies);
 374         }
 375
 376         RETURN(lcw);
 377 }
 378 EXPORT_SYMBOL(lc_watchdog_add);
 379
 380 static void lcw_update_time(struct lc_watchdog *lcw, const char *message)
 381 {
 382         ktime_t newtime = ktime_get();
 383
 384         if (lcw->lcw_state == LC_WATCHDOG_EXPIRED) {
 385                 ktime_t lapse = ktime_sub(newtime, lcw->lcw_last_touched);
 386                 struct timespec64 timediff;
 387
 388                 timediff = ktime_to_timespec64(lapse);
 389                 LCONSOLE_WARN("Service thread pid %u %s after %lu.%.02lus. This indicates the system was overloaded (too many service threads, or there were not enough hardware resources).\n",
 390                               lcw->lcw_pid, message,
 391                               timediff.tv_sec,
 392                               timediff.tv_nsec / (NSEC_PER_SEC / 100));
 393         }
 394         lcw->lcw_last_touched = newtime;
 395 }
 396
 397 static void lc_watchdog_del_pending(struct lc_watchdog *lcw)
 398 {
 399         spin_lock_bh(&lcw->lcw_lock);
 400         if (unlikely(!list_empty(&lcw->lcw_list))) {
 401                 spin_lock_bh(&lcw_pending_timers_lock);
 402                 list_del_init(&lcw->lcw_list);
 403                 lcw->lcw_refcount--; /* -1 ref for pending list */
 404                 spin_unlock_bh(&lcw_pending_timers_lock);
 405         }
 406
 407         spin_unlock_bh(&lcw->lcw_lock);
 408 }
 409
 410 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
 411 {
 412         ENTRY;
 413         LASSERT(lcw != NULL);
 414
 415         lc_watchdog_del_pending(lcw);
 416
 417         lcw_update_time(lcw, "resumed");
 418
 419         mod_timer(&lcw->lcw_timer, jiffies + cfs_time_seconds(timeout));
 420         lcw->lcw_state = LC_WATCHDOG_ENABLED;
 421
 422         EXIT;
 423 }
 424 EXPORT_SYMBOL(lc_watchdog_touch);
 425
 426 void lc_watchdog_disable(struct lc_watchdog *lcw)
 427 {
 428         ENTRY;
 429         LASSERT(lcw != NULL);
 430
 431         lc_watchdog_del_pending(lcw);
 432
 433         lcw_update_time(lcw, "completed");
 434         lcw->lcw_state = LC_WATCHDOG_DISABLED;
 435
 436         EXIT;
 437 }
 438 EXPORT_SYMBOL(lc_watchdog_disable);
 439
 440 void lc_watchdog_delete(struct lc_watchdog *lcw)
 441 {
 442         int dead;
 443
 444         ENTRY;
 445         LASSERT(lcw != NULL);
 446
 447         del_timer(&lcw->lcw_timer);
 448
 449         lcw_update_time(lcw, "stopped");
 450
 451         spin_lock_bh(&lcw->lcw_lock);
 452         spin_lock_bh(&lcw_pending_timers_lock);
 453         if (unlikely(!list_empty(&lcw->lcw_list))) {
 454                 list_del_init(&lcw->lcw_list);
 455                 lcw->lcw_refcount--; /* -1 ref for pending list */
 456         }
 457
 458         lcw->lcw_refcount--; /* -1 ref for owner */
 459         dead = lcw->lcw_refcount == 0;
 460         spin_unlock_bh(&lcw_pending_timers_lock);
 461         spin_unlock_bh(&lcw->lcw_lock);
 462
 463         if (dead)
 464                 LIBCFS_FREE(lcw, sizeof(*lcw));
 465
 466         mutex_lock(&lcw_refcount_mutex);
 467         if (--lcw_refcount == 0)
 468                 lcw_dispatch_stop();
 469         mutex_unlock(&lcw_refcount_mutex);
 470
 471         EXIT;
 472 }
 473 EXPORT_SYMBOL(lc_watchdog_delete);
 474
 475 #else   /* !defined(WITH_WATCHDOG) */
 476
 477 struct lc_watchdog *lc_watchdog_add(int timeout,
 478                                     void (*callback)(pid_t pid, void *),
 479                                     void *data)
 480 {
 481         static struct lc_watchdog      watchdog;
 482         return &watchdog;
 483 }
 484 EXPORT_SYMBOL(lc_watchdog_add);
 485
 486 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
 487 {
 488 }
 489 EXPORT_SYMBOL(lc_watchdog_touch);
 490
 491 void lc_watchdog_disable(struct lc_watchdog *lcw)
 492 {
 493 }
 494 EXPORT_SYMBOL(lc_watchdog_disable);
 495
 496 void lc_watchdog_delete(struct lc_watchdog *lcw)
 497 {
 498 }
 499 EXPORT_SYMBOL(lc_watchdog_delete);
 500
 501 #endif