linux-kernel - [tip:timers/urgent] hrtimer: Set expiry time before switch_hrtimer

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Message-ID: <tip-84ea7fe37908254c3bd90910921f6e1045c1747a@git.kernel.org>
Date:	Mon, 12 May 2014 01:51:58 -0700
From:	tip-bot for Viresh Kumar <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	viresh.kumar@...aro.org, tglx@...utronix.de
Subject: [tip:timers/urgent] hrtimer:
  Set expiry time before switch_hrtimer_base()

Commit-ID:  84ea7fe37908254c3bd90910921f6e1045c1747a
Gitweb:     http://git.kernel.org/tip/84ea7fe37908254c3bd90910921f6e1045c1747a
Author:     Viresh Kumar <viresh.kumar@...aro.org>
AuthorDate: Mon, 12 May 2014 13:42:29 +0530
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 12 May 2014 10:47:39 +0200

hrtimer: Set expiry time before switch_hrtimer_base()

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
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/hrtimer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6b715c0..e0501fe 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -990,11 +990,8 @@ 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
@@ -1009,6 +1006,9 @@ 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);
+
 	timer_stats_hrtimer_set_start_info(timer);
 
 	leftmost = enqueue_hrtimer(timer, new_base);
--
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