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Commit 9082c465 authored by John Stultz's avatar John Stultz
Browse files

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: default avatarJohn Stultz <john.stultz@linaro.org>
parent a28cde81

include/linux/alarmtimer.h

+2 −1
Original line number Diff line number Diff line
@@ -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);

kernel/time/alarmtimer.c

+37 −6
Original line number Diff line number Diff line
@@ -336,21 +336,49 @@ void alarm_start(struct alarm *alarm, ktime_t start) 
}



/**

 * alarm_cancel - Tries to cancel an alarm timer

 * alarm_try_to_cancel - Tries to cancel an alarm timer

 * @alarm: ptr to alarm to be canceled

 *

 * Returns 1 if the timer was canceled, 0 if it was not running,

 * and -1 if the callback was running

 */

void alarm_cancel(struct alarm *alarm)

int alarm_try_to_cancel(struct alarm *alarm)

{

	struct alarm_base *base = &alarm_bases[alarm->type];

	unsigned long flags;



	int ret = -1;

	spin_lock_irqsave(&base->lock, flags);

	if (alarmtimer_is_queued(alarm))



	if (alarmtimer_callback_running(alarm))

		goto out;



	if (alarmtimer_is_queued(alarm)) {

		alarmtimer_remove(base, alarm);

		ret = 1;

	} else

		ret = 0;

out:

	spin_unlock_irqrestore(&base->lock, flags);

	return ret;

}





/**

 * alarm_cancel - Spins trying to cancel an alarm timer until it is done

 * @alarm: ptr to alarm to be canceled

 *

 * Returns 1 if the timer was canceled, 0 if it was not active.

 */

int alarm_cancel(struct alarm *alarm)

{

	for (;;) {

		int ret = alarm_try_to_cancel(alarm);

		if (ret >= 0)

			return ret;

		cpu_relax();

	}

}





u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval)

{
@@ -510,7 +538,9 @@ static int alarm_timer_del(struct k_itimer *timr) 
	if (!rtcdev)

		return -ENOTSUPP;



	alarm_cancel(&timr->it.alarm.alarmtimer);

	if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)

		return TIMER_RETRY;



	return 0;

}
@@ -534,7 +564,8 @@ static int alarm_timer_set(struct k_itimer *timr, int flags, 
		alarm_timer_get(timr, old_setting);



	/* If the timer was already set, cancel it */

	alarm_cancel(&timr->it.alarm.alarmtimer);

	if (alarm_try_to_cancel(&timr->it.alarm.alarmtimer) < 0)

		return TIMER_RETRY;



	/* start the timer */

	timr->it.alarm.interval = timespec_to_ktime(new_setting->it_interval);