From: Richard Larocque <rlarocque@google.com>
Date: Wed, 10 Sep 2014 01:31:05 +0000 (-0700)
Subject: alarmtimer: Lock k_itimer during timer callback
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=3c47864204b4df3e0d506c5a53cc7f1111467411;p=linux-edison.git

alarmtimer: Lock k_itimer during timer callback

commit 474e941bed9262f5fa2394f9a4a67e24499e5926 upstream.

Locks the k_itimer's it_lock member when handling the alarm timer's
expiry callback.

The regular posix timers defined in posix-timers.c have this lock held
during timout processing because their callbacks are routed through
posix_timer_fn().  The alarm timers follow a different path, so they
ought to grab the lock somewhere else.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: Richard Larocque <rlarocque@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index a2d2a480701..7d19fca0617 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -419,8 +419,12 @@ static enum alarmtimer_type clock2alarm(clockid_t clockid)
 static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
 							ktime_t now)
 {
+	unsigned long flags;
 	struct k_itimer *ptr = container_of(alarm, struct k_itimer,
 						it.alarm.alarmtimer);
+	enum alarmtimer_restart result = ALARMTIMER_NORESTART;
+
+	spin_lock_irqsave(&ptr->it_lock, flags);
 	if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) {
 		if (posix_timer_event(ptr, 0) != 0)
 			ptr->it_overrun++;
@@ -430,9 +434,11 @@ static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
 	if (ptr->it.alarm.interval.tv64) {
 		ptr->it_overrun += alarm_forward(alarm, now,
 						ptr->it.alarm.interval);
-		return ALARMTIMER_RESTART;
+		result = ALARMTIMER_RESTART;
 	}
-	return ALARMTIMER_NORESTART;
+	spin_unlock_irqrestore(&ptr->it_lock, flags);
+
+	return result;
 }
 
 /**