[PATCH 1/1] UBUNTU: softlockup: Stop spurious softlockup messages due to overflow

[Colin King]

BugLink: http://bugs.launchpad.net/bugs/551068

Stop spurious sotlock messages due to math overflow when TSC
warps coming out of S3.

This is a backport of the upstream commit
8c2eb4805d422bdbf60ba00ff233c794d23c3c00 - the posting states:

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.

Cc: Peter Zijlstra <a.p.zijlstra at chello.nl>
Cc: Eric Dumazet <eric.dumazet at gmail.com>
Cc: <stable at kernel.org>
LKML-Reference: <1268994482.1798.6.camel at lenovo>
Signed-off-by: Ingo Molnar <mingo at elte.hu>
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 kernel/softlockup.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index 88796c3..db592e0 100644
--- a/kernel/softlockup.c
+++ b/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;
-- 
1.6.3.3