linux-kernel - [PATCH 3.2 64/92] hrtimer: Set expiry time before switch_hrtimer

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Date:	Sat, 07 Jun 2014 02:26:29 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, arvind.chauhan@....com,
	"Viresh Kumar" <viresh.kumar@...aro.org>,
	linaro-networking@...aro.org,
	"Thomas Gleixner" <tglx@...utronix.de>, fweisbec@...il.com,
	linaro-kernel@...ts.linaro.org
Subject: [PATCH 3.2 64/92] hrtimer: Set expiry time before switch_hrtimer_base()

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

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

From: Viresh Kumar <viresh.kumar@...aro.org>

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@...aro.org>
Cc: linaro-kernel@...ts.linaro.org
Cc: linaro-networking@...aro.org
Cc: fweisbec@...il.com
Cc: arvind.chauhan@....com
Link: http://lkml.kernel.org/r/81999e148745fc51bbcd0615823fbab9b2e87e23.1399882253.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/hrtimer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -980,11 +980,8 @@ int __hrtimer_start_range_ns(struct hrti
 	/* 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
@@ -999,6 +996,9 @@ int __hrtimer_start_range_ns(struct hrti
 
 	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);
+
 	timer_stats_hrtimer_set_start_info(timer);
 
 	leftmost = enqueue_hrtimer(timer, new_base);

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