lnet/libcfs/watchdog.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * Copyright (C) 2004 Cluster File Systems, Inc.
   5  *   Author: Jacob Berkman <jacob@clusterfs.com>
   6  *
   7  *   This file is part of Lustre, http://www.lustre.org.
   8  *
   9  *   Lustre is free software; you can redistribute it and/or
  10  *   modify it under the terms of version 2 of the GNU General Public
  11  *   License as published by the Free Software Foundation.
  12  *
  13  *   Lustre is distributed in the hope that it will be useful,
  14  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *   GNU General Public License for more details.
  17  *
  18  *   You should have received a copy of the GNU General Public License
  19  *   along with Lustre; if not, write to the Free Software
  20  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #define DEBUG_SUBSYSTEM S_LNET
  24
  25 #include <libcfs/kp30.h>
  26 #include <libcfs/libcfs.h>
  27 #include "tracefile.h"
  28
  29 struct lc_watchdog {
  30         cfs_timer_t       lcw_timer; /* kernel timer */
  31         struct list_head  lcw_list;
  32         struct timeval    lcw_last_touched;
  33         cfs_task_t       *lcw_task;
  34
  35         void            (*lcw_callback)(pid_t, void *);
  36         void             *lcw_data;
  37
  38         pid_t             lcw_pid;
  39         int               lcw_time; /* time until watchdog fires, in ms */
  40
  41         enum {
  42                 LC_WATCHDOG_DISABLED,
  43                 LC_WATCHDOG_ENABLED,
  44                 LC_WATCHDOG_EXPIRED
  45         } lcw_state;
  46 };
  47
  48 #ifdef WITH_WATCHDOG
  49 /*
  50  * The dispatcher will complete lcw_start_completion when it starts,
  51  * and lcw_stop_completion when it exits.
  52  * Wake lcw_event_waitq to signal timer callback dispatches.
  53  */
  54 static struct completion lcw_start_completion;
  55 static struct completion lcw_stop_completion;
  56 static wait_queue_head_t lcw_event_waitq;
  57
  58 /*
  59  * Set this and wake lcw_event_waitq to stop the dispatcher.
  60  */
  61 enum {
  62         LCW_FLAG_STOP = 0
  63 };
  64 static unsigned long lcw_flags = 0;
  65
  66 /*
  67  * Number of outstanding watchdogs.
  68  * When it hits 1, we start the dispatcher.
  69  * When it hits 0, we stop the distpatcher.
  70  */
  71 static __u32         lcw_refcount = 0;
  72 static DECLARE_MUTEX(lcw_refcount_sem);
  73
  74 /*
  75  * List of timers that have fired that need their callbacks run by the
  76  * dispatcher.
  77  */
  78 static spinlock_t lcw_pending_timers_lock = SPIN_LOCK_UNLOCKED; /* BH lock! */
  79 static struct list_head lcw_pending_timers = \
  80         LIST_HEAD_INIT(lcw_pending_timers);
  81
  82 #ifdef HAVE_TASKLIST_LOCK
  83 static void
  84 lcw_dump(struct lc_watchdog *lcw)
  85 {
  86         cfs_task_t *tsk;
  87         ENTRY;
  88
  89         read_lock(&tasklist_lock);
  90         tsk = find_task_by_pid(lcw->lcw_pid);
  91
  92         if (tsk == NULL) {
  93                 CWARN("Process %d was not found in the task list; "
  94                       "watchdog callback may be incomplete\n", (int)lcw->lcw_pid);
  95         } else if (tsk != lcw->lcw_task) {
  96                 CWARN("The current process %d did not set the watchdog; "
  97                       "watchdog callback may be incomplete\n", (int)lcw->lcw_pid);
  98         } else {
  99                 libcfs_debug_dumpstack(tsk);
 100         }
 101
 102         read_unlock(&tasklist_lock);
 103         EXIT;
 104 }
 105 #else
 106 static void
 107 lcw_dump(struct lc_watchdog *lcw)
 108 {
 109         CERROR("unable to dump stack because of missing export\n");
 110 }
 111 #endif
 112
 113 static void lcw_cb(unsigned long data)
 114 {
 115         struct lc_watchdog *lcw = (struct lc_watchdog *)data;
 116
 117         ENTRY;
 118
 119         if (lcw->lcw_state != LC_WATCHDOG_ENABLED) {
 120                 EXIT;
 121                 return;
 122         }
 123
 124         lcw->lcw_state = LC_WATCHDOG_EXPIRED;
 125
 126         /* NB this warning should appear on the console, but may not get into
 127          * the logs since we're running in a softirq handler */
 128
 129         CWARN("Watchdog triggered for pid %d: it was inactive for %ldms\n",
 130               (int)lcw->lcw_pid, cfs_duration_sec(lcw->lcw_time) * 1000);
 131         lcw_dump(lcw);
 132
 133         spin_lock_bh(&lcw_pending_timers_lock);
 134
 135         if (list_empty(&lcw->lcw_list)) {
 136                 list_add(&lcw->lcw_list, &lcw_pending_timers);
 137                 wake_up(&lcw_event_waitq);
 138         }
 139
 140         spin_unlock_bh(&lcw_pending_timers_lock);
 141
 142         EXIT;
 143 }
 144
 145 static int is_watchdog_fired(void)
 146 {
 147         int rc;
 148
 149         if (test_bit(LCW_FLAG_STOP, &lcw_flags))
 150                 return 1;
 151
 152         spin_lock_bh(&lcw_pending_timers_lock);
 153         rc = !list_empty(&lcw_pending_timers);
 154         spin_unlock_bh(&lcw_pending_timers_lock);
 155         return rc;
 156 }
 157
 158 static int lcw_dispatch_main(void *data)
 159 {
 160         int                 rc = 0;
 161         unsigned long       flags;
 162         struct lc_watchdog *lcw;
 163
 164         ENTRY;
 165
 166         cfs_daemonize("lc_watchdogd");
 167
 168         SIGNAL_MASK_LOCK(current, flags);
 169         sigfillset(&current->blocked);
 170         RECALC_SIGPENDING;
 171         SIGNAL_MASK_UNLOCK(current, flags);
 172
 173         complete(&lcw_start_completion);
 174
 175         while (1) {
 176                 wait_event_interruptible(lcw_event_waitq, is_watchdog_fired());
 177                 CDEBUG(D_INFO, "Watchdog got woken up...\n");
 178                 if (test_bit(LCW_FLAG_STOP, &lcw_flags)) {
 179                         CDEBUG(D_INFO, "LCW_FLAG_STOP was set, shutting down...\n");
 180
 181                         spin_lock_bh(&lcw_pending_timers_lock);
 182                         rc = !list_empty(&lcw_pending_timers);
 183                         spin_unlock_bh(&lcw_pending_timers_lock);
 184                         if (rc) {
 185                                 CERROR("pending timers list was not empty at "
 186                                        "time of watchdog dispatch shutdown\n");
 187                         }
 188                         break;
 189                 }
 190
 191                 spin_lock_bh(&lcw_pending_timers_lock);
 192                 while (!list_empty(&lcw_pending_timers)) {
 193
 194                         lcw = list_entry(lcw_pending_timers.next,
 195                                          struct lc_watchdog,
 196                                          lcw_list);
 197                         list_del_init(&lcw->lcw_list);
 198                         spin_unlock_bh(&lcw_pending_timers_lock);
 199
 200                         CDEBUG(D_INFO, "found lcw for pid %d: inactive for %ldms\n",
 201                                (int)lcw->lcw_pid, cfs_duration_sec(lcw->lcw_time) * 1000);
 202
 203                         if (lcw->lcw_state != LC_WATCHDOG_DISABLED)
 204                                 lcw->lcw_callback(lcw->lcw_pid, lcw->lcw_data);
 205
 206                         spin_lock_bh(&lcw_pending_timers_lock);
 207                 }
 208                 spin_unlock_bh(&lcw_pending_timers_lock);
 209         }
 210
 211         complete(&lcw_stop_completion);
 212
 213         RETURN(rc);
 214 }
 215
 216 static void lcw_dispatch_start(void)
 217 {
 218         int rc;
 219
 220         ENTRY;
 221         LASSERT(lcw_refcount == 1);
 222
 223         init_completion(&lcw_stop_completion);
 224         init_completion(&lcw_start_completion);
 225         init_waitqueue_head(&lcw_event_waitq);
 226
 227         CDEBUG(D_INFO, "starting dispatch thread\n");
 228         rc = kernel_thread(lcw_dispatch_main, NULL, 0);
 229         if (rc < 0) {
 230                 CERROR("error spawning watchdog dispatch thread: %d\n", rc);
 231                 EXIT;
 232                 return;
 233         }
 234         wait_for_completion(&lcw_start_completion);
 235         CDEBUG(D_INFO, "watchdog dispatcher initialization complete.\n");
 236
 237         EXIT;
 238 }
 239
 240 static void lcw_dispatch_stop(void)
 241 {
 242         ENTRY;
 243         LASSERT(lcw_refcount == 0);
 244
 245         CDEBUG(D_INFO, "trying to stop watchdog dispatcher.\n");
 246
 247         set_bit(LCW_FLAG_STOP, &lcw_flags);
 248         wake_up(&lcw_event_waitq);
 249
 250         wait_for_completion(&lcw_stop_completion);
 251
 252         CDEBUG(D_INFO, "watchdog dispatcher has shut down.\n");
 253
 254         EXIT;
 255 }
 256
 257 struct lc_watchdog *lc_watchdog_add(int timeout_ms,
 258                                     void (*callback)(pid_t, void *),
 259                                     void *data)
 260 {
 261         struct lc_watchdog *lcw = NULL;
 262         ENTRY;
 263
 264         LIBCFS_ALLOC(lcw, sizeof(*lcw));
 265         if (lcw == NULL) {
 266                 CDEBUG(D_INFO, "Could not allocate new lc_watchdog\n");
 267                 RETURN(ERR_PTR(-ENOMEM));
 268         }
 269
 270         lcw->lcw_task     = cfs_current();
 271         lcw->lcw_pid      = cfs_curproc_pid();
 272         lcw->lcw_time     = cfs_time_seconds(timeout_ms) / 1000;
 273         lcw->lcw_callback = (callback != NULL) ? callback : lc_watchdog_dumplog;
 274         lcw->lcw_data     = data;
 275         lcw->lcw_state    = LC_WATCHDOG_DISABLED;
 276
 277         INIT_LIST_HEAD(&lcw->lcw_list);
 278
 279         lcw->lcw_timer.function = lcw_cb;
 280         lcw->lcw_timer.data = (unsigned long)lcw;
 281         lcw->lcw_timer.expires = jiffies + lcw->lcw_time;
 282         init_timer(&lcw->lcw_timer);
 283
 284         down(&lcw_refcount_sem);
 285         if (++lcw_refcount == 1)
 286                 lcw_dispatch_start();
 287         up(&lcw_refcount_sem);
 288
 289         /* Keep this working in case we enable them by default */
 290         if (lcw->lcw_state == LC_WATCHDOG_ENABLED) {
 291                 do_gettimeofday(&lcw->lcw_last_touched);
 292                 add_timer(&lcw->lcw_timer);
 293         }
 294
 295         RETURN(lcw);
 296 }
 297 EXPORT_SYMBOL(lc_watchdog_add);
 298
 299 static void lcw_update_time(struct lc_watchdog *lcw, const char *message)
 300 {
 301         struct timeval newtime;
 302         struct timeval timediff;
 303
 304         do_gettimeofday(&newtime);
 305         if (lcw->lcw_state == LC_WATCHDOG_EXPIRED) {
 306                 cfs_timeval_sub(&newtime, &lcw->lcw_last_touched, &timediff);
 307                 CWARN("Expired watchdog for pid %d %s after %lu.%.4lus\n",
 308                       lcw->lcw_pid,
 309                       message,
 310                       timediff.tv_sec,
 311                       timediff.tv_usec / 100);
 312         }
 313         lcw->lcw_last_touched = newtime;
 314 }
 315
 316 void lc_watchdog_touch(struct lc_watchdog *lcw)
 317 {
 318         ENTRY;
 319         LASSERT(lcw != NULL);
 320
 321         spin_lock_bh(&lcw_pending_timers_lock);
 322         list_del_init(&lcw->lcw_list);
 323         spin_unlock_bh(&lcw_pending_timers_lock);
 324
 325         lcw_update_time(lcw, "touched");
 326         lcw->lcw_state = LC_WATCHDOG_ENABLED;
 327
 328         mod_timer(&lcw->lcw_timer, jiffies + lcw->lcw_time);
 329
 330         EXIT;
 331 }
 332 EXPORT_SYMBOL(lc_watchdog_touch);
 333
 334 void lc_watchdog_disable(struct lc_watchdog *lcw)
 335 {
 336         ENTRY;
 337         LASSERT(lcw != NULL);
 338
 339         spin_lock_bh(&lcw_pending_timers_lock);
 340         if (!list_empty(&lcw->lcw_list))
 341                 list_del_init(&lcw->lcw_list);
 342         spin_unlock_bh(&lcw_pending_timers_lock);
 343
 344         lcw_update_time(lcw, "disabled");
 345         lcw->lcw_state = LC_WATCHDOG_DISABLED;
 346
 347         EXIT;
 348 }
 349 EXPORT_SYMBOL(lc_watchdog_disable);
 350
 351 void lc_watchdog_delete(struct lc_watchdog *lcw)
 352 {
 353         ENTRY;
 354         LASSERT(lcw != NULL);
 355
 356         del_timer(&lcw->lcw_timer);
 357
 358         lcw_update_time(lcw, "deleted");
 359
 360         spin_lock_bh(&lcw_pending_timers_lock);
 361         if (!list_empty(&lcw->lcw_list))
 362                 list_del_init(&lcw->lcw_list);
 363         spin_unlock_bh(&lcw_pending_timers_lock);
 364
 365         down(&lcw_refcount_sem);
 366         if (--lcw_refcount == 0)
 367                 lcw_dispatch_stop();
 368         up(&lcw_refcount_sem);
 369
 370         LIBCFS_FREE(lcw, sizeof(*lcw));
 371
 372         EXIT;
 373 }
 374 EXPORT_SYMBOL(lc_watchdog_delete);
 375
 376 /*
 377  * Provided watchdog handlers
 378  */
 379
 380 void lc_watchdog_dumplog(pid_t pid, void *data)
 381 {
 382         libcfs_debug_dumplog_internal((void *)((unsigned long)pid));
 383 }
 384 EXPORT_SYMBOL(lc_watchdog_dumplog);
 385
 386 #else   /* !defined(WITH_WATCHDOG) */
 387
 388 struct lc_watchdog *lc_watchdog_add(int timeout_ms,
 389                                     void (*callback)(pid_t pid, void *),
 390                                     void *data)
 391 {
 392         static struct lc_watchdog      watchdog;
 393         return &watchdog;
 394 }
 395 EXPORT_SYMBOL(lc_watchdog_add);
 396
 397 void lc_watchdog_touch(struct lc_watchdog *lcw)
 398 {
 399 }
 400 EXPORT_SYMBOL(lc_watchdog_touch);
 401
 402 void lc_watchdog_disable(struct lc_watchdog *lcw)
 403 {
 404 }
 405 EXPORT_SYMBOL(lc_watchdog_disable);
 406
 407 void lc_watchdog_delete(struct lc_watchdog *lcw)
 408 {
 409 }
 410 EXPORT_SYMBOL(lc_watchdog_delete);
 411
 412 #endif
 413