linux-kernel - [091/116] softlockup: Stop spurious softlockup messages due to overflow

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Date:	Tue, 30 Mar 2010 15:56:09 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Colin Ian King <colin.king@...onical.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [091/116] softlockup: Stop spurious softlockup messages due to overflow

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Colin Ian King <colin.king@...onical.com>

commit 8c2eb4805d422bdbf60ba00ff233c794d23c3c00 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@...onical.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Eric Dumazet <eric.dumazet@...il.com>
LKML-Reference: <1268994482.1798.6.camel@...ovo>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/softlockup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 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;


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