Merge branch 'clocksource.2022.10.18c' into HEAD

clocksource.2022.10.18c: Clocksource watchdog updates

Author: paulmckrcu

kernel/time/clocksource.c

@@ -386,7 +386,7 @@ EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
 
 static void clocksource_watchdog(struct timer_list *unused)
 {
-	u64 csnow, wdnow, cslast, wdlast, delta;
+	u64 csnow, wdnow, cslast, wdlast, delta, wdi;
 	int next_cpu, reset_pending;
 	int64_t wd_nsec, cs_nsec;
 	struct clocksource *cs;
@@ -440,6 +440,17 @@ static void clocksource_watchdog(struct timer_list *unused)
 		if (atomic_read(&watchdog_reset_pending))
 			continue;
 
+		/* Check for bogus measurements. */
+		wdi = jiffies_to_nsecs(WATCHDOG_INTERVAL);
+		if (wd_nsec < (wdi >> 2)) {
+			pr_warn("timekeeping watchdog on CPU%d: Watchdog clocksource '%s' advanced only %lld ns during %d-jiffy time interval, skipping watchdog check.\n", smp_processor_id(), watchdog->name, wd_nsec, WATCHDOG_INTERVAL);
+			continue;
+		}
+		if (wd_nsec > (wdi << 2)) {
+			pr_warn("timekeeping watchdog on CPU%d: Watchdog clocksource '%s' advanced an excessive %lld ns during %d-jiffy time interval, probable CPU overutilization, skipping watchdog check.\n", smp_processor_id(), watchdog->name, wd_nsec, WATCHDOG_INTERVAL);
+			continue;
+		}
+
 		/* Check the deviation from the watchdog clocksource. */
 		md = cs->uncertainty_margin + watchdog->uncertainty_margin;
 		if (abs(cs_nsec - wd_nsec) > md) {