linux-kernel - [51/85] timer: Fix jiffies wrap behavior of round_jiffies

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Message-ID: <lsq.1374674565.40666954@decadent.org.uk>
Date:	Wed, 24 Jul 2013 15:02:45 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Arjan van de Ven" <arjan@...radead.org>,
	"Bart Van Assche" <bvanassche@....org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Stephen Rothwell" <sfr@...b.auug.org.au>,
	"Bart Van Assche" <bart.vanassche@...il.com>
Subject: [51/85] timer: Fix jiffies wrap behavior of round_jiffies_common()

3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Bart Van Assche <bart.vanassche@...il.com>

commit 9e04d3804d3ac97d8c03a41d78d0f0674b5d01e1 upstream.

Direct compare of jiffies related values does not work in the wrap
around case. Replace it with time_is_after_jiffies().

Signed-off-by: Bart Van Assche <bvanassche@....org>
Cc: Arjan van de Ven <arjan@...radead.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Link: http://lkml.kernel.org/r/519BC066.5080600@acm.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/timer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -145,9 +145,11 @@ static unsigned long round_jiffies_commo
 	/* now that we have rounded, subtract the extra skew again */
 	j -= cpu * 3;
 
-	if (j <= jiffies) /* rounding ate our timeout entirely; */
-		return original;
-	return j;
+	/*
+	 * Make sure j is still in the future. Otherwise return the
+	 * unmodified value.
+	 */
+	return time_is_after_jiffies(j) ? j : original;
 }
 
 /**

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