softlockup: Stop spurious softlockup messages due to overflow

commit 8c2eb480 upstream.

Ensure additions on touch_ts do not overflow.  This can occur
when the top 32 bits of the TSC reach 0xffffffff causing
additions to touch_ts to overflow and this in turn generates
spurious softlockup warnings.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
LKML-Reference: <1268994482.1798.6.camel@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kernel/softlockup.c

@@ -140,11 +140,11 @@ void softlockup_tick(void)
 	 * Wake up the high-prio watchdog task twice per
 	 * threshold timespan.
 	 */
-	if (now > touch_timestamp + softlockup_thresh/2)
+	if (time_after(now - softlockup_thresh/2, touch_timestamp))
 		wake_up_process(per_cpu(watchdog_task, this_cpu));
 
 	/* Warn about unreasonable delays: */
-	if (now <= (touch_timestamp + softlockup_thresh))
+	if (time_before_eq(now - softlockup_thresh, touch_timestamp))
 		return;
 
 	per_cpu(print_timestamp, this_cpu) = touch_timestamp;