linux-kernel - [ 27/38] timer: Fix jiffies wrap behavior of round_jiffies

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Message-Id: <20130719052049.733140406@linuxfoundation.org>
Date:	Thu, 18 Jul 2013 22:21:43 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
	Arjan van de Ven <arjan@...radead.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [ 27/38] timer: Fix jiffies wrap behavior of round_jiffies_common()

3.9-stable 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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/timer.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -148,9 +148,11 @@ 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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