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32 * libcfs/libcfs/watchdog.c
34 * Author: Jacob Berkman <jacob@clusterfs.com>
37 #define DEBUG_SUBSYSTEM S_LNET
39 #include <linux/kthread.h>
40 #include <libcfs/libcfs.h>
41 #include "tracefile.h"
48 spinlock_t lcw_lock; /* check or change lcw_list */
49 int lcw_refcount; /* must hold lcw_pending_timers_lock */
50 struct timer_list lcw_timer; /* kernel timer */
51 struct list_head lcw_list; /* chain on pending list */
52 ktime_t lcw_last_touched;/* last touched stamp */
53 struct task_struct *lcw_task; /* owner task */
54 void (*lcw_callback)(pid_t, void *);
68 * The dispatcher will complete lcw_start_completion when it starts,
69 * and lcw_stop_completion when it exits.
70 * Wake lcw_event_waitq to signal timer callback dispatches.
72 static struct completion lcw_start_completion;
73 static struct completion lcw_stop_completion;
74 static wait_queue_head_t lcw_event_waitq;
77 * Set this and wake lcw_event_waitq to stop the dispatcher.
82 static unsigned long lcw_flags = 0;
85 * Number of outstanding watchdogs.
86 * When it hits 1, we start the dispatcher.
87 * When it hits 0, we stop the dispatcher.
89 static __u32 lcw_refcount = 0;
90 static DEFINE_MUTEX(lcw_refcount_mutex);
93 * List of timers that have fired that need their callbacks run by the
97 static DEFINE_SPINLOCK(lcw_pending_timers_lock);
98 static struct list_head lcw_pending_timers = LIST_HEAD_INIT(lcw_pending_timers);
100 /* Last time a watchdog expired */
101 static time64_t lcw_last_watchdog_time;
102 static int lcw_recent_watchdog_count;
105 lcw_dump(struct lc_watchdog *lcw)
109 if (lcw->lcw_task == NULL) {
110 LCONSOLE_WARN("Process %d was not found in the task "
111 "list; watchdog callback may be incomplete\n",
114 libcfs_debug_dumpstack(lcw->lcw_task);
121 static void lcw_cb(cfs_timer_cb_arg_t data)
123 struct lc_watchdog *lcw = cfs_from_timer(lcw, data, lcw_timer);
126 if (lcw->lcw_state != LC_WATCHDOG_ENABLED) {
131 lcw->lcw_state = LC_WATCHDOG_EXPIRED;
133 spin_lock_bh(&lcw->lcw_lock);
134 LASSERT(list_empty(&lcw->lcw_list));
136 spin_lock_bh(&lcw_pending_timers_lock);
137 lcw->lcw_refcount++; /* +1 for pending list */
138 list_add(&lcw->lcw_list, &lcw_pending_timers);
139 wake_up(&lcw_event_waitq);
141 spin_unlock_bh(&lcw_pending_timers_lock);
142 spin_unlock_bh(&lcw->lcw_lock);
146 static int is_watchdog_fired(void)
150 if (test_bit(LCW_FLAG_STOP, &lcw_flags))
153 spin_lock_bh(&lcw_pending_timers_lock);
154 rc = !list_empty(&lcw_pending_timers);
155 spin_unlock_bh(&lcw_pending_timers_lock);
159 static void lcw_dump_stack(struct lc_watchdog *lcw)
161 time64_t current_time = ktime_get_seconds();
162 struct timespec64 timediff;
165 timediff = ktime_to_timespec64(ktime_sub(ktime_get(),
166 lcw->lcw_last_touched));
168 /* LU-9235: Don't dump stack if the thread is just touched. */
169 if (timediff.tv_sec == 0)
173 * Check to see if we should throttle the watchdog timer to avoid
174 * too many dumps going to the console thus triggering an NMI.
176 delta_time = current_time - lcw_last_watchdog_time;
177 if (delta_time < libcfs_watchdog_ratelimit &&
178 lcw_recent_watchdog_count > 3) {
179 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",
182 timediff.tv_nsec / (NSEC_PER_SEC / 100),
183 libcfs_watchdog_ratelimit);
185 if (delta_time < libcfs_watchdog_ratelimit) {
186 lcw_recent_watchdog_count++;
188 memcpy(&lcw_last_watchdog_time, ¤t_time,
189 sizeof(current_time));
190 lcw_recent_watchdog_count = 0;
193 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",
196 timediff.tv_nsec / (NSEC_PER_SEC / 100));
202 * Provided watchdog handlers
205 static void lc_watchdog_dumplog(pid_t pid, void *data)
207 libcfs_debug_dumplog_internal((void *)((uintptr_t)pid));
210 static int lcw_dispatch_main(void *data)
213 struct lc_watchdog *lcw;
214 struct list_head zombies = LIST_HEAD_INIT(zombies);
218 complete(&lcw_start_completion);
223 rc = wait_event_interruptible(lcw_event_waitq,
224 is_watchdog_fired());
225 CDEBUG(D_INFO, "Watchdog got woken up...\n");
226 if (test_bit(LCW_FLAG_STOP, &lcw_flags)) {
227 CDEBUG(D_INFO, "LCW_FLAG_STOP set, shutting down...\n");
229 spin_lock_bh(&lcw_pending_timers_lock);
230 rc = !list_empty(&lcw_pending_timers);
231 spin_unlock_bh(&lcw_pending_timers_lock);
233 CERROR("pending timers list was not empty at "
234 "time of watchdog dispatch shutdown\n");
239 spin_lock_bh(&lcw_pending_timers_lock);
240 while (!list_empty(&lcw_pending_timers)) {
243 lcw = list_entry(lcw_pending_timers.next,
244 struct lc_watchdog, lcw_list);
245 /* +1 ref for callback to make sure lwc wouldn't be
246 * deleted after releasing lcw_pending_timers_lock */
248 spin_unlock_bh(&lcw_pending_timers_lock);
251 spin_lock_bh(&lcw->lcw_lock);
252 spin_lock_bh(&lcw_pending_timers_lock);
254 if (list_empty(&lcw->lcw_list)) {
255 /* already removed from pending list */
256 lcw->lcw_refcount--; /* -1 ref for callback */
257 if (lcw->lcw_refcount == 0)
258 list_add(&lcw->lcw_list, &zombies);
259 spin_unlock_bh(&lcw->lcw_lock);
260 /* still hold lcw_pending_timers_lock */
264 list_del_init(&lcw->lcw_list);
265 lcw->lcw_refcount--; /* -1 ref for pending list */
267 spin_unlock_bh(&lcw_pending_timers_lock);
268 spin_unlock_bh(&lcw->lcw_lock);
270 CDEBUG(D_INFO, "found lcw for pid %d\n",
274 is_dumplog = lcw->lcw_callback == lc_watchdog_dumplog;
275 if (lcw->lcw_state != LC_WATCHDOG_DISABLED &&
276 (dumplog || !is_dumplog)) {
277 lcw->lcw_callback(lcw->lcw_pid, lcw->lcw_data);
278 if (dumplog && is_dumplog)
282 spin_lock_bh(&lcw_pending_timers_lock);
283 lcw->lcw_refcount--; /* -1 ref for callback */
284 if (lcw->lcw_refcount == 0)
285 list_add(&lcw->lcw_list, &zombies);
287 spin_unlock_bh(&lcw_pending_timers_lock);
289 while (!list_empty(&zombies)) {
290 lcw = list_entry(zombies.next,
291 struct lc_watchdog, lcw_list);
292 list_del_init(&lcw->lcw_list);
293 LIBCFS_FREE(lcw, sizeof(*lcw));
297 complete(&lcw_stop_completion);
302 static void lcw_dispatch_start(void)
304 struct task_struct *task;
307 LASSERT(lcw_refcount == 1);
309 init_completion(&lcw_stop_completion);
310 init_completion(&lcw_start_completion);
311 init_waitqueue_head(&lcw_event_waitq);
313 CDEBUG(D_INFO, "starting dispatch thread\n");
314 task = kthread_run(lcw_dispatch_main, NULL, "lc_watchdogd");
316 CERROR("error spawning watchdog dispatch thread: %ld\n",
321 wait_for_completion(&lcw_start_completion);
322 CDEBUG(D_INFO, "watchdog dispatcher initialization complete.\n");
327 static void lcw_dispatch_stop(void)
330 LASSERT(lcw_refcount == 0);
332 CDEBUG(D_INFO, "trying to stop watchdog dispatcher.\n");
334 set_bit(LCW_FLAG_STOP, &lcw_flags);
335 wake_up(&lcw_event_waitq);
337 wait_for_completion(&lcw_stop_completion);
338 clear_bit(LCW_FLAG_STOP, &lcw_flags);
340 CDEBUG(D_INFO, "watchdog dispatcher has shut down.\n");
345 struct lc_watchdog *lc_watchdog_add(int timeout,
346 void (*callback)(pid_t, void *),
349 struct lc_watchdog *lcw = NULL;
352 LIBCFS_ALLOC(lcw, sizeof(*lcw));
354 CDEBUG(D_INFO, "Could not allocate new lc_watchdog\n");
355 RETURN(ERR_PTR(-ENOMEM));
358 spin_lock_init(&lcw->lcw_lock);
359 lcw->lcw_refcount = 1; /* refcount for owner */
360 lcw->lcw_task = current;
361 lcw->lcw_pid = current_pid();
362 lcw->lcw_callback = (callback != NULL) ? callback : lc_watchdog_dumplog;
363 lcw->lcw_data = data;
364 lcw->lcw_state = LC_WATCHDOG_DISABLED;
366 INIT_LIST_HEAD(&lcw->lcw_list);
367 cfs_timer_setup(&lcw->lcw_timer, lcw_cb, (unsigned long)lcw, 0);
369 mutex_lock(&lcw_refcount_mutex);
370 if (++lcw_refcount == 1)
371 lcw_dispatch_start();
372 mutex_unlock(&lcw_refcount_mutex);
374 /* Keep this working in case we enable them by default */
375 if (lcw->lcw_state == LC_WATCHDOG_ENABLED) {
376 lcw->lcw_last_touched = ktime_get();
377 mod_timer(&lcw->lcw_timer, cfs_time_seconds(timeout) +
383 EXPORT_SYMBOL(lc_watchdog_add);
385 static void lcw_update_time(struct lc_watchdog *lcw, const char *message)
387 ktime_t newtime = ktime_get();
389 if (lcw->lcw_state == LC_WATCHDOG_EXPIRED) {
390 ktime_t lapse = ktime_sub(newtime, lcw->lcw_last_touched);
391 struct timespec64 timediff;
393 timediff = ktime_to_timespec64(lapse);
394 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",
395 lcw->lcw_pid, message,
397 timediff.tv_nsec / (NSEC_PER_SEC / 100));
399 lcw->lcw_last_touched = newtime;
402 static void lc_watchdog_del_pending(struct lc_watchdog *lcw)
404 spin_lock_bh(&lcw->lcw_lock);
405 if (unlikely(!list_empty(&lcw->lcw_list))) {
406 spin_lock_bh(&lcw_pending_timers_lock);
407 list_del_init(&lcw->lcw_list);
408 lcw->lcw_refcount--; /* -1 ref for pending list */
409 spin_unlock_bh(&lcw_pending_timers_lock);
412 spin_unlock_bh(&lcw->lcw_lock);
415 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
418 LASSERT(lcw != NULL);
420 lc_watchdog_del_pending(lcw);
422 lcw_update_time(lcw, "resumed");
424 mod_timer(&lcw->lcw_timer, jiffies + cfs_time_seconds(timeout));
425 lcw->lcw_state = LC_WATCHDOG_ENABLED;
429 EXPORT_SYMBOL(lc_watchdog_touch);
431 void lc_watchdog_disable(struct lc_watchdog *lcw)
434 LASSERT(lcw != NULL);
436 lc_watchdog_del_pending(lcw);
438 lcw_update_time(lcw, "completed");
439 lcw->lcw_state = LC_WATCHDOG_DISABLED;
443 EXPORT_SYMBOL(lc_watchdog_disable);
445 void lc_watchdog_delete(struct lc_watchdog *lcw)
450 LASSERT(lcw != NULL);
452 del_timer(&lcw->lcw_timer);
454 lcw_update_time(lcw, "stopped");
456 spin_lock_bh(&lcw->lcw_lock);
457 spin_lock_bh(&lcw_pending_timers_lock);
458 if (unlikely(!list_empty(&lcw->lcw_list))) {
459 list_del_init(&lcw->lcw_list);
460 lcw->lcw_refcount--; /* -1 ref for pending list */
463 lcw->lcw_refcount--; /* -1 ref for owner */
464 dead = lcw->lcw_refcount == 0;
465 spin_unlock_bh(&lcw_pending_timers_lock);
466 spin_unlock_bh(&lcw->lcw_lock);
469 LIBCFS_FREE(lcw, sizeof(*lcw));
471 mutex_lock(&lcw_refcount_mutex);
472 if (--lcw_refcount == 0)
474 mutex_unlock(&lcw_refcount_mutex);
478 EXPORT_SYMBOL(lc_watchdog_delete);
480 #else /* !defined(WITH_WATCHDOG) */
482 struct lc_watchdog *lc_watchdog_add(int timeout,
483 void (*callback)(pid_t pid, void *),
486 static struct lc_watchdog watchdog;
489 EXPORT_SYMBOL(lc_watchdog_add);
491 void lc_watchdog_touch(struct lc_watchdog *lcw, int timeout)
494 EXPORT_SYMBOL(lc_watchdog_touch);
496 void lc_watchdog_disable(struct lc_watchdog *lcw)
499 EXPORT_SYMBOL(lc_watchdog_disable);
501 void lc_watchdog_delete(struct lc_watchdog *lcw)
504 EXPORT_SYMBOL(lc_watchdog_delete);