linux-kernel - [tip:timers/core] timer: Fix jiffies wrap behavior of round_jiffies

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Message-ID: <tip-9e04d3804d3ac97d8c03a41d78d0f0674b5d01e1@git.kernel.org>
Date:	Fri, 28 Jun 2013 08:12:35 -0700
From:	tip-bot for Bart Van Assche <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	arjan@...radead.org, bvanassche@....org, tglx@...utronix.de,
	sfr@...b.auug.org.au, bart.vanassche@...il.com
Subject: [tip:timers/core] timer:
  Fix jiffies wrap behavior of round_jiffies_common()

Commit-ID:  9e04d3804d3ac97d8c03a41d78d0f0674b5d01e1
Gitweb:     http://git.kernel.org/tip/9e04d3804d3ac97d8c03a41d78d0f0674b5d01e1
Author:     Bart Van Assche <bart.vanassche@...il.com>
AuthorDate: Tue, 21 May 2013 20:43:50 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 28 Jun 2013 17:10:11 +0200

timer: Fix jiffies wrap behavior of round_jiffies_common()

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
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/timer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/timer.c b/kernel/timer.c
index 15ffdb3..15bc1b4 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -149,9 +149,11 @@ 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;
 }
 
 /**
--
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