libcfs/libcfs/watchdog.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * GPL HEADER START
   5  *
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License version 2 for more details (a copy is included
  16  * in the LICENSE file that accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * version 2 along with this program; If not, see
  20  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  25  *
  26  * GPL HEADER END
  27  */
  28 /*
  29  * Copyright  2008 Sun Microsystems, Inc. All rights reserved
  30  * Use is subject to license terms.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * libcfs/libcfs/watchdog.c
  37  *
  38  * Author: Jacob Berkman <jacob@clusterfs.com>
  39  */
  40
  41 #define DEBUG_SUBSYSTEM S_LNET
  42
  43 #include <libcfs/libcfs.h>
  44 #include "tracefile.h"
  45
  46 struct lc_watchdog {
  47         cfs_timer_t       lcw_timer; /* kernel timer */
  48         struct list_head  lcw_list;
  49         cfs_time_t        lcw_last_touched;
  50         cfs_task_t       *lcw_task;
  51
  52         void            (*lcw_callback)(pid_t, void *);
  53         void             *lcw_data;
  54
  55         pid_t             lcw_pid;
  56
  57         enum {
  58                 LC_WATCHDOG_DISABLED,
  59                 LC_WATCHDOG_ENABLED,
  60                 LC_WATCHDOG_EXPIRED
  61         } lcw_state;
  62 };
  63
  64 #ifdef WITH_WATCHDOG
  65 /*
  66  * The dispatcher will complete lcw_start_completion when it starts,
  67  * and lcw_stop_completion when it exits.
  68  * Wake lcw_event_waitq to signal timer callback dispatches.
  69  */
  70 static struct completion lcw_start_completion;
  71 static struct completion lcw_stop_completion;
  72 static cfs_waitq_t lcw_event_waitq;
  73
  74 /*
  75  * Set this and wake lcw_event_waitq to stop the dispatcher.
  76  */
  77 enum {
  78         LCW_FLAG_STOP = 0
  79 };
  80 static unsigned long lcw_flags = 0;
  81
  82 /*
  83  * Number of outstanding watchdogs.
  84  * When it hits 1, we start the dispatcher.
  85  * When it hits 0, we stop the distpatcher.
  86  */
  87 static __u32         lcw_refcount = 0;
  88 static DECLARE_MUTEX(lcw_refcount_sem);
  89
  90 /*
  91  * List of timers that have fired that need their callbacks run by the
  92  * dispatcher.
  93  */
  94 static spinlock_t lcw_pending_timers_lock = SPIN_LOCK_UNLOCKED; /* BH lock! */
  95 static struct list_head lcw_pending_timers = \
  96         CFS_LIST_HEAD_INIT(lcw_pending_timers);
  97
  98 /* Last time a watchdog expired */
  99 static cfs_time_t lcw_last_watchdog_time;
 100 static int lcw_recent_watchdog_count;
 101 static spinlock_t lcw_last_watchdog_lock = SPIN_LOCK_UNLOCKED;
 102
 103 static void
 104 lcw_dump(struct lc_watchdog *lcw)
 105 {
 106         ENTRY;
 107 #if defined(HAVE_TASKLIST_LOCK)
 108         read_lock(&tasklist_lock);
 109 #elif defined(HAVE_TASK_RCU)
 110         rcu_read_lock();
 111 #else
 112         CERROR("unable to dump stack because of missing export\n");
 113         RETURN_EXIT;
 114 #endif
 115        if (lcw->lcw_task == NULL) {
 116                 LCONSOLE_WARN("Process " LPPID " was not found in the task "
 117                               "list; watchdog callback may be incomplete\n",
 118                               (int)lcw->lcw_pid);
 119         } else {
 120                 libcfs_debug_dumpstack(lcw->lcw_task);
 121         }
 122
 123 #if defined(HAVE_TASKLIST_LOCK)
 124         read_unlock(&tasklist_lock);
 125 #elif defined(HAVE_TASK_RCU)
 126         rcu_read_unlock();
 127 #endif
 128         EXIT;
 129 }
 130
 131 static void lcw_cb(ulong_ptr_t data)
 132 {
 133         struct lc_watchdog *lcw = (struct lc_watchdog *)data;
 134         cfs_time_t current_time;
 135         cfs_duration_t delta_time;
 136         struct timeval timediff;
 137
 138         ENTRY;
 139
 140         if (lcw->lcw_state != LC_WATCHDOG_ENABLED) {
 141                 EXIT;
 142                 return;
 143         }
 144
 145         lcw->lcw_state = LC_WATCHDOG_EXPIRED;
 146         current_time = cfs_time_current();
 147
 148         delta_time = cfs_time_sub(current_time, lcw->lcw_last_touched);
 149         cfs_duration_usec(delta_time, &timediff);
 150
 151         /* Check to see if we should throttle the watchdog timer to avoid
 152          * too many dumps going to the console thus triggering an NMI.
 153          * Normally we would not hold the spin lock over the CWARN but in
 154          * this case we hold it to ensure non ratelimited lcw_dumps are not
 155          * interleaved on the console making them hard to read. */
 156         spin_lock_bh(&lcw_last_watchdog_lock);
 157         delta_time = cfs_duration_sec(cfs_time_sub(current_time,
 158                                                    lcw_last_watchdog_time));
 159
 160         if (delta_time < libcfs_watchdog_ratelimit &&
 161             lcw_recent_watchdog_count > 3) {
 162                 LCONSOLE_WARN("Service thread pid %u was inactive for "
 163                               "%lu.%.02lus. Watchdog stack traces are limited "
 164                               "to 3 per %d seconds, skipping this one.\n",
 165                               (int)lcw->lcw_pid,
 166                               timediff.tv_sec,
 167                               timediff.tv_usec / 10000,
 168                               libcfs_watchdog_ratelimit);
 169         } else {
 170                 if (delta_time < libcfs_watchdog_ratelimit) {
 171                         lcw_recent_watchdog_count++;
 172                 } else {
 173                         memcpy(&lcw_last_watchdog_time, &current_time,
 174                                sizeof(current_time));
 175                         lcw_recent_watchdog_count = 0;
 176                 }
 177
 178                 /* This warning should appear on the console, but may not get
 179                  * into the logs since we're running in a softirq handler */
 180                 LCONSOLE_WARN("Service thread pid %u was inactive for "
 181                               "%lu.%.02lus. The thread might be hung, or it "
 182                               "might only be slow and will resume later. "
 183                               "Dumping the stack trace for debugging purposes:"
 184                               "\n",
 185                               (int)lcw->lcw_pid,
 186                               timediff.tv_sec,
 187                               timediff.tv_usec / 10000);
 188                 lcw_dump(lcw);
 189         }
 190
 191         spin_unlock_bh(&lcw_last_watchdog_lock);
 192         spin_lock_bh(&lcw_pending_timers_lock);
 193
 194         if (list_empty(&lcw->lcw_list)) {
 195                 list_add(&lcw->lcw_list, &lcw_pending_timers);
 196                 cfs_waitq_signal(&lcw_event_waitq);
 197         }
 198
 199         spin_unlock_bh(&lcw_pending_timers_lock);
 200
 201         EXIT;
 202 }
 203
 204 static int is_watchdog_fired(void)
 205 {
 206         int rc;
 207
 208         if (test_bit(LCW_FLAG_STOP, &lcw_flags))
 209                 return 1;
 210
 211         spin_lock_bh(&lcw_pending_timers_lock);
 212         rc = !list_empty(&lcw_pending_timers);
 213         spin_unlock_bh(&lcw_pending_timers_lock);
 214         return rc;
 215 }
 216
 217 static int lcw_dispatch_main(void *data)
 218 {
 219         int                 rc = 0;
 220         unsigned long       flags;
 221         struct lc_watchdog *lcw;
 222
 223         ENTRY;
 224
 225         cfs_daemonize("lc_watchdogd");
 226
 227         SIGNAL_MASK_LOCK(current, flags);
 228         sigfillset(&current->blocked);
 229         RECALC_SIGPENDING;
 230         SIGNAL_MASK_UNLOCK(current, flags);
 231
 232         complete(&lcw_start_completion);
 233
 234         while (1) {
 235                 cfs_wait_event_interruptible(lcw_event_waitq, is_watchdog_fired(), rc);
 236                 CDEBUG(D_INFO, "Watchdog got woken up...\n");
 237                 if (test_bit(LCW_FLAG_STOP, &lcw_flags)) {
 238                         CDEBUG(D_INFO, "LCW_FLAG_STOP was set, shutting down...\n");
 239
 240                         spin_lock_bh(&lcw_pending_timers_lock);
 241                         rc = !list_empty(&lcw_pending_timers);
 242                         spin_unlock_bh(&lcw_pending_timers_lock);
 243                         if (rc) {
 244                                 CERROR("pending timers list was not empty at "
 245                                        "time of watchdog dispatch shutdown\n");
 246                         }
 247                         break;
 248                 }
 249
 250                 spin_lock_bh(&lcw_pending_timers_lock);
 251                 while (!list_empty(&lcw_pending_timers)) {
 252
 253                         lcw = list_entry(lcw_pending_timers.next,
 254                                          struct lc_watchdog,
 255                                          lcw_list);
 256                         list_del_init(&lcw->lcw_list);
 257                         spin_unlock_bh(&lcw_pending_timers_lock);
 258
 259                         CDEBUG(D_INFO, "found lcw for pid " LPPID "\n", lcw->lcw_pid);
 260
 261                         if (lcw->lcw_state != LC_WATCHDOG_DISABLED)
 262                                 lcw->lcw_callback(lcw->lcw_pid, lcw->lcw_data);
 263
 264                         spin_lock_bh(&lcw_pending_timers_lock);
 265                 }
 266                 spin_unlock_bh(&lcw_pending_timers_lock);
 267         }
 268
 269         complete(&lcw_stop_completion);
 270
 271         RETURN(rc);
 272 }
 273
 274 static void lcw_dispatch_start(void)
 275 {
 276         int rc;
 277
 278         ENTRY;
 279         LASSERT(lcw_refcount == 1);
 280
 281         init_completion(&lcw_stop_completion);
 282         init_completion(&lcw_start_completion);
 283         cfs_waitq_init(&lcw_event_waitq);
 284
 285         CDEBUG(D_INFO, "starting dispatch thread\n");
 286         rc = kernel_thread(lcw_dispatch_main, NULL, 0);
 287         if (rc < 0) {
 288                 CERROR("error spawning watchdog dispatch thread: %d\n", rc);
 289                 EXIT;
 290                 return;
 291         }
 292         wait_for_completion(&lcw_start_completion);
 293         CDEBUG(D_INFO, "watchdog dispatcher initialization complete.\n");
 294
 295         EXIT;
 296 }
 297
 298 static void lcw_dispatch_stop(void)
 299 {
 300         ENTRY;
 301         LASSERT(lcw_refcount == 0);
 302
 303         CDEBUG(D_INFO, "trying to stop watchdog dispatcher.\n");
 304
 305         set_bit(LCW_FLAG_STOP, &lcw_flags);
 306         cfs_waitq_signal(&lcw_event_waitq);
 307
 308         wait_for_completion(&lcw_stop_completion);
 309
 310         CDEBUG(D_INFO, "watchdog dispatcher has shut down.\n");
 311
 312         EXIT;
 313 }
 314
 315 struct lc_watchdog *lc_watchdog_add(int timeout,
 316                                     void (*callback)(pid_t, void *),
 317                                     void *data)
 318 {
 319         struct lc_watchdog *lcw = NULL;
 320         ENTRY;
 321
 322         LIBCFS_ALLOC(lcw, sizeof(*lcw));
 323         if (lcw == NULL) {
 324                 CDEBUG(D_INFO, "Could not allocate new lc_watchdog\n");
 325                 RETURN(ERR_PTR(-ENOMEM));
 326         }
 327
 328         lcw->lcw_task     = cfs_current();
 329         lcw->lcw_pid      = cfs_curproc_pid();
 330         lcw->lcw_callback = (callback != NULL) ? callback : lc_watchdog_dumplog;
 331         lcw->lcw_data     = data;
 332         lcw->lcw_state    = LC_WATCHDOG_DISABLED;
 333
 334         CFS_INIT_LIST_HEAD(&lcw->lcw_list);
 335         cfs_timer_init(&lcw->lcw_timer, lcw_cb, lcw);
 336
 337         down(&lcw_refcount_sem);
 338         if (++lcw_refcount == 1)
 339                 lcw_dispatch_start();
 340         up(&lcw_refcount_sem);
 341
 342         /* Keep this working in case we enable them by default */
 343         if (lcw->lcw_state == LC_WATCHDOG_ENABLED) {
 344                 lcw->lcw_last_touched = cfs_time_current();
 345                 cfs_timer_arm(&lcw->lcw_timer, cfs_time_seconds(timeout) +
 346                               cfs_time_current());
 347         }
 348
 349         RETURN(lcw);
 350 }
 351 EXPORT_SYMBOL(lc_watchdog_add);
 352
 353 static void lcw_update_time(struct lc_watchdog *lcw, const char *message)
 354 {
 355         cfs_time_t newtime = cfs_time_current();;
 356
 357         if (lcw->lcw_state == LC_WATCHDOG_EXPIRED) {
 358                 struct timeval timediff;
 359                 cfs_time_t delta_time = cfs_time_sub(newtime,
 360                                                      lcw->lcw_last_touched);
 361                 cfs_duration_usec(delta_time, &timediff);
 362
 363                 LCONSOLE_WARN("Service thread pid %u %s after %lu.%.02lus. "
 364                               "This indicates the system was overloaded (too "
 365                               "many service threads, or there were not enough "
 366                               "hardware resources).\n",
 367                               lcw->lcw_pid,
 368                               message,
 369                               timediff.tv_sec,
 370                               timediff.tv_usec / 10000);
 371         }
 372         lcw->lcw_last_touched = newtime;
 373 }
 374
 375 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
 376 {
 377         ENTRY;
 378         LASSERT(lcw != NULL);
 379
 380         spin_lock_bh(&lcw_pending_timers_lock);
 381         list_del_init(&lcw->lcw_list);
 382         spin_unlock_bh(&lcw_pending_timers_lock);
 383
 384         lcw_update_time(lcw, "resumed");
 385         lcw->lcw_state = LC_WATCHDOG_ENABLED;
 386
 387         cfs_timer_arm(&lcw->lcw_timer, cfs_time_current() +
 388                       cfs_time_seconds(timeout));
 389
 390         EXIT;
 391 }
 392 EXPORT_SYMBOL(lc_watchdog_touch);
 393
 394 void lc_watchdog_disable(struct lc_watchdog *lcw)
 395 {
 396         ENTRY;
 397         LASSERT(lcw != NULL);
 398
 399         spin_lock_bh(&lcw_pending_timers_lock);
 400         if (!list_empty(&lcw->lcw_list))
 401                 list_del_init(&lcw->lcw_list);
 402         spin_unlock_bh(&lcw_pending_timers_lock);
 403
 404         lcw_update_time(lcw, "completed");
 405         lcw->lcw_state = LC_WATCHDOG_DISABLED;
 406
 407         EXIT;
 408 }
 409 EXPORT_SYMBOL(lc_watchdog_disable);
 410
 411 void lc_watchdog_delete(struct lc_watchdog *lcw)
 412 {
 413         ENTRY;
 414         LASSERT(lcw != NULL);
 415
 416         cfs_timer_disarm(&lcw->lcw_timer);
 417
 418         lcw_update_time(lcw, "stopped");
 419
 420         spin_lock_bh(&lcw_pending_timers_lock);
 421         if (!list_empty(&lcw->lcw_list))
 422                 list_del_init(&lcw->lcw_list);
 423         spin_unlock_bh(&lcw_pending_timers_lock);
 424
 425         down(&lcw_refcount_sem);
 426         if (--lcw_refcount == 0)
 427                 lcw_dispatch_stop();
 428         up(&lcw_refcount_sem);
 429
 430         LIBCFS_FREE(lcw, sizeof(*lcw));
 431
 432         EXIT;
 433 }
 434 EXPORT_SYMBOL(lc_watchdog_delete);
 435
 436 /*
 437  * Provided watchdog handlers
 438  */
 439
 440 void lc_watchdog_dumplog(pid_t pid, void *data)
 441 {
 442         libcfs_debug_dumplog_internal((void *)((long_ptr_t)pid));
 443 }
 444 EXPORT_SYMBOL(lc_watchdog_dumplog);
 445
 446 #else   /* !defined(WITH_WATCHDOG) */
 447
 448 struct lc_watchdog *lc_watchdog_add(int timeout,
 449                                     void (*callback)(pid_t pid, void *),
 450                                     void *data)
 451 {
 452         static struct lc_watchdog      watchdog;
 453         return &watchdog;
 454 }
 455 EXPORT_SYMBOL(lc_watchdog_add);
 456
 457 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
 458 {
 459 }
 460 EXPORT_SYMBOL(lc_watchdog_touch);
 461
 462 void lc_watchdog_disable(struct lc_watchdog *lcw)
 463 {
 464 }
 465 EXPORT_SYMBOL(lc_watchdog_disable);
 466
 467 void lc_watchdog_delete(struct lc_watchdog *lcw)
 468 {
 469 }
 470 EXPORT_SYMBOL(lc_watchdog_delete);
 471
 472 #endif