kernel/time/clocksource.c

111  * Maximum permissible delay between two readouts of the watchdog
132 static struct clocksource *watchdog;
165 	 * If kthread_run fails the next watchdog scan over the
194  * clocksource_mark_unstable - mark clocksource unstable via watchdog
231 		*wdnow = watchdog->read(watchdog);
233 		wd_end = watchdog->read(watchdog);
234 		wd_end2 = watchdog->read(watchdog);
237 		wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
238 		wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
239 					      watchdog->shift);
242 				pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
243 					smp_processor_id(), watchdog->name, nretries);
249 		 * Now compute delay in consecutive watchdog read to see if
251 		 * significant delay in reading both clocksource and watchdog.
254 		 * report system busy, reinit the watchdog and skip the current
255 		 * watchdog test.
257 		wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
258 		wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
263 	pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd excessive read-back delay of %lldns vs. limit of %ldns, wd-wd read-back delay only %lldns, attempt %d, marking %s unstable\n",
268 	pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
269 		smp_processor_id(), watchdog->name, wd_seq_delay);
435 		 * watchdog/clocksource is very big, and affect the accuracy of
436 		 * watchdog check. So give system some space and suspend the
437 		 * watchdog check for 5 minutes.
441 			 * As the watchdog timer will be suspended, and
459 		delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
460 		wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
461 					     watchdog->shift);
476 		 * manner), which causes the watchdog interval to stretch.
477 		 * Skew detection may fail for longer watchdog intervals
480 		 * watchdog intervals longer than a few seconds.
487 				pr_warn("Long readout interval, skipping watchdog check: cs_nsec: %lld wd_nsec: %lld\n",
494 		/* Check the deviation from the watchdog clocksource. */
495 		md = cs->uncertainty_margin + watchdog->uncertainty_margin;
501 			pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
504 				watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
509 			pr_warn("                      Clocksource '%s' skewed %lld ns (%lld ms) over watchdog '%s' interval of %lld ns (%lld ms)\n",
510 				cs->name, cs_nsec - wd_nsec, cs_wd_msec, watchdog->name, wd_nsec, wd_msec);
526 		    (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
539 			 * the watchdog thread reselect it. Due to the
583 	if (watchdog_running || !watchdog || list_empty(&watchdog_list))
593 	if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
613 		/* cs is a watchdog. */
625 	/* save current watchdog */
626 	old_wd = watchdog;
628 		watchdog = NULL;
639 		/* Pick the best watchdog. */
640 		if (!watchdog || cs->rating > watchdog->rating)
641 			watchdog = cs;
644 	if (!watchdog)
645 		watchdog = old_wd;
647 	/* If we changed the watchdog we need to reset cycles. */
648 	if (watchdog != old_wd)
651 	/* Check if the watchdog timer needs to be started. */
658 	if (cs != watchdog) {
662 			/* Check if the watchdog timer needs to be stopped. */
692 	/* Check if the watchdog timer needs to be stopped. */
710 	return cs == watchdog;
894  * clocksource_touch_watchdog - Update watchdog
896  * Update the watchdog after exception contexts such as kgdb so as not
897  * to incorrectly trip the watchdog. This might fail when the kernel
1033 				 * Deferring to let the watchdog check.
1082 	 * Run the watchdog first to eliminate unstable clock sources
1277 		/* Select and try to install a replacement watchdog. */