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Old 07-23-2012, 05:24 PM
Luis Henriques
Default 2.6.32.x: hrtimers: Move lock held region in hrtimer_interrupt()

From: Thomas Gleixner <tglx@linutronix.de>

BugLink: http://bugs.launchpad.net/bugs/1020285

This is a backport of 196951e91262fccda81147d2bcf7fdab08668b40

We need to update the base offsets from this code and we need to do
that under base->lock. Move the lock held region around the
ktime_get() calls. The ktime_get() calls are going to be replaced with
a function which gets the time and the offsets atomically.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/1341960205-56738-6-git-send-email-johnstul@us.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
kernel/hrtimer.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c4acec7..8ba6d31 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1263,11 +1263,10 @@ void hrtimer_interrupt(struct clock_event_device *dev)
dev->next_event.tv64 = KTIME_MAX;

+ spin_lock(&cpu_base->lock);
entry_time = now = ktime_get();
expires_next.tv64 = KTIME_MAX;
- spin_lock(&cpu_base->lock);
* We set expires_next to KTIME_MAX here with cpu_base->lock
* held to prevent that a timer is enqueued in our queue via
@@ -1342,6 +1341,7 @@ retry:
* interrupt routine. We give it 3 attempts to avoid
* overreacting on some spurious event.
+ spin_lock(&cpu_base->lock);
now = ktime_get();
if (++retries < 3)
@@ -1354,6 +1354,7 @@ retry:
cpu_base->hang_detected = 1;
+ spin_unlock(&cpu_base->lock);
delta = ktime_sub(now, entry_time);
if (delta.tv64 > cpu_base->max_hang_time.tv64)
cpu_base->max_hang_time = delta;

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