[3.11.y.z extended stable] Patch "hrtimer: Set expiry time before switch_hrtimer_base()" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Fri May 30 09:28:48 UTC 2014

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

    hrtimer: Set expiry time before switch_hrtimer_base()

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:


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

For more information about the 3.11.y.z tree, see



>From bbe1a6ec07f62a0a8990187a0dd7622cce772ed5 Mon Sep 17 00:00:00 2001
From: Viresh Kumar <viresh.kumar at linaro.org>
Date: Mon, 12 May 2014 13:42:29 +0530
Subject: hrtimer: Set expiry time before switch_hrtimer_base()

commit 84ea7fe37908254c3bd90910921f6e1045c1747a upstream.

switch_hrtimer_base() calls hrtimer_check_target() which ensures that
we do not migrate a timer to a remote cpu if the timer expires before
the current programmed expiry time on that remote cpu.

But __hrtimer_start_range_ns() calls switch_hrtimer_base() before the
new expiry time is set. So the sanity check in hrtimer_check_target()
is operating on stale or even uninitialized data.

Update expiry time before calling switch_hrtimer_base().

[ tglx: Rewrote changelog once again ]

Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
Cc: linaro-kernel at lists.linaro.org
Cc: linaro-networking at linaro.org
Cc: fweisbec at gmail.com
Cc: arvind.chauhan at arm.com
Link: http://lkml.kernel.org/r/81999e148745fc51bbcd0615823fbab9b2e87e23.1399882253.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 kernel/hrtimer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6de65d8a70e2..aa149222cd8e 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1002,11 +1002,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 	/* Remove an active timer from the queue: */
 	ret = remove_hrtimer(timer, base);

-	/* Switch the timer base, if necessary: */
-	new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
 	if (mode & HRTIMER_MODE_REL) {
-		tim = ktime_add_safe(tim, new_base->get_time());
+		tim = ktime_add_safe(tim, base->get_time());
 		 * CONFIG_TIME_LOW_RES is a temporary way for architectures
 		 * to signal that they simply return xtime in
@@ -1021,6 +1018,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

 	hrtimer_set_expires_range_ns(timer, tim, delta_ns);

+	/* Switch the timer base, if necessary: */
+	new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);

 	leftmost = enqueue_hrtimer(timer, new_base);

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