rtc: Expire alarms after the time is set.

If the alarm time programming in the rtc is ever in the past, it won't fire,
and any other alarm will be queued after it so they won't fire either.

So any time that the alarm might be in the past, we need to trigger
the irq handler to ensure the old alarm is cleared and the timer queue
is fully in the future.

This can happen:
 - when we first initialise the alarm
 - when we set the time in the rtc.

so follow both of these by scheduling the timer work function.

CC: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
[Also catch set_mmss case -jstultz]
Signed-off-by: John Stultz <john.stultz@linaro.org>

drivers/rtc/interface.c

@@ -73,6 +73,8 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
 		err = -EINVAL;
 
 	mutex_unlock(&rtc->ops_lock);
+	/* A timer might have just expired */
+	schedule_work(&rtc->irqwork);
 	return err;
 }
 EXPORT_SYMBOL_GPL(rtc_set_time);
@@ -112,6 +114,8 @@ int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs)
 		err = -EINVAL;
 
 	mutex_unlock(&rtc->ops_lock);
+	/* A timer might have just expired */
+	schedule_work(&rtc->irqwork);
 
 	return err;
 }
@@ -403,6 +407,8 @@ int rtc_initialize_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 		timerqueue_add(&rtc->timerqueue, &rtc->aie_timer.node);
 	}
 	mutex_unlock(&rtc->ops_lock);
+	/* maybe that was in the past.*/
+	schedule_work(&rtc->irqwork);
 	return err;
 }
 EXPORT_SYMBOL_GPL(rtc_initialize_alarm);