alarmtimers: Add try_to_cancel functionality

There's a number of edge cases when cancelling a alarm, so
to be sure we accurately do so, introduce try_to_cancel, which
returns proper failure errors if it cannot. Also modify cancel
to spin until the alarm is properly disabled.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/alarmtimer.h b/include/linux/alarmtimer.h
index 304124a6c98..975009e1cbe 100644
--- a/include/linux/alarmtimer.h
+++ b/include/linux/alarmtimer.h
@@ -44,7 +44,8 @@ struct alarm {
 void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
                 enum alarmtimer_restart (*function)(struct alarm *, ktime_t));
 void alarm_start(struct alarm *alarm, ktime_t start);
-void alarm_cancel(struct alarm *alarm);
+int alarm_try_to_cancel(struct alarm *alarm);
+int alarm_cancel(struct alarm *alarm);
 
 u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval);