softlockup: fix watchdog task wakeup frequency

Updating the timestamp more often is pointless as we print the warnings
only if we exceed the threshold.  And the check for hung tasks relies on
the last timestamp, so it will keep working correctly, too.
Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/softlockup.c

@@ -130,8 +130,11 @@ void softlockup_tick(void)
 
 	now = get_timestamp(this_cpu);
 
-	/* Wake up the high-prio watchdog task every second: */
-	if (now > (touch_timestamp + 1))
+	/*
+	 * Wake up the high-prio watchdog task twice per
+	 * threshold timespan.
+	 */
+	if (now > touch_timestamp + softlockup_thresh/2)
 		wake_up_process(per_cpu(watchdog_task, this_cpu));
 
 	/* Warn about unreasonable delays: */