[ 3.8.y.z extended stable ] Patch "timer: Fix jiffies wrap behavior of round_jiffies_common()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    timer: Fix jiffies wrap behavior of round_jiffies_common()

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 83c0ca53ac34e613b4e57011d1c0b2f13033091b Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bart.vanassche at gmail.com>
Date: Tue, 21 May 2013 20:43:50 +0200
Subject: [PATCH] timer: Fix jiffies wrap behavior of round_jiffies_common()

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 at acm.org>
Cc: Arjan van de Ven <arjan at infradead.org>
Cc: Stephen Rothwell <sfr at canb.auug.org.au>
Link: http://lkml.kernel.org/r/519BC066.5080600@acm.org
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/timer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/timer.c b/kernel/timer.c
index 18f6b85..1f8a6bd 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -147,9 +147,11 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu,
 	/* 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;
 }

 /**
--
1.8.1.2