linux-kernel - [tip:perf/urgent] watchdog: Fix rounding bug in get_sample

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Message-ID: <tip-824c6b7f6294101f30e141117def224a56c203e6@git.kernel.org>
Date:	Mon, 23 May 2011 11:12:17 GMT
From:	tip-bot for Mandeep Singh Baines <msb@...omium.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, msb@...omium.org, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, marcin.slusarz@...il.com,
	fweisbec@...il.com, tglx@...utronix.de, mingo@...e.hu,
	dzickus@...hat.com
Subject: [tip:perf/urgent] watchdog: Fix rounding bug in get_sample_period()

Commit-ID:  824c6b7f6294101f30e141117def224a56c203e6
Gitweb:     http://git.kernel.org/tip/824c6b7f6294101f30e141117def224a56c203e6
Author:     Mandeep Singh Baines <msb@...omium.org>
AuthorDate: Sun, 22 May 2011 22:10:20 -0700
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Mon, 23 May 2011 11:58:58 +0200

watchdog: Fix rounding bug in get_sample_period()

In get_sample_period(), softlockup_thresh is integer divided by
5 before the multiplication by NSEC_PER_SEC. This results in
softlockup_thresh being rounded down to the nearest integer
multiple of 5.

For example, a softlockup_thresh of 4 rounds down to 0.

Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
Cc: Marcin Slusarz <marcin.slusarz@...il.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Link: http://lkml.kernel.org/r/1306127423-3347-1-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/watchdog.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 14733d4..a06972d 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -110,7 +110,7 @@ static unsigned long get_sample_period(void)
 	 * increment before the hardlockup detector generates
 	 * a warning
 	 */
-	return softlockup_thresh / 5 * NSEC_PER_SEC;
+	return softlockup_thresh * (NSEC_PER_SEC / 5);
 }
 
 /* Commands for resetting the watchdog */
--
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