alarmtimers: Add more refined alarm state tracking

In order to allow for functionality like try_to_cancel, add
more refined  state tracking (similar to hrtimers).

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

include/linux/alarmtimer.h

@@ -18,6 +18,11 @@ enum alarmtimer_restart {
 	ALARMTIMER_RESTART,
 };
 
+
+#define ALARMTIMER_STATE_INACTIVE	0x00
+#define ALARMTIMER_STATE_ENQUEUED	0x01
+#define ALARMTIMER_STATE_CALLBACK	0x02
+
 /**
  * struct alarm - Alarm timer structure
  * @node:	timerqueue node for adding to the event list this value
@@ -32,7 +37,7 @@ struct alarm {
 	struct timerqueue_node	node;
 	enum alarmtimer_restart	(*function)(struct alarm *, ktime_t now);
 	enum alarmtimer_type	type;
-	bool			enabled;
+	int			state;
 	void			*data;
 };
 
@@ -43,4 +48,31 @@ void alarm_cancel(struct alarm *alarm);
 
 u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval);
 
+/*
+ * A alarmtimer is active, when it is enqueued into timerqueue or the
+ * callback function is running.
+ */
+static inline int alarmtimer_active(const struct alarm *timer)
+{
+	return timer->state != ALARMTIMER_STATE_INACTIVE;
+}
+
+/*
+ * Helper function to check, whether the timer is on one of the queues
+ */
+static inline int alarmtimer_is_queued(struct alarm *timer)
+{
+	return timer->state & ALARMTIMER_STATE_ENQUEUED;
+}
+
+/*
+ * Helper function to check, whether the timer is running the callback
+ * function
+ */
+static inline int alarmtimer_callback_running(struct alarm *timer)
+{
+	return timer->state & ALARMTIMER_STATE_CALLBACK;
+}
+
+
 #endif

kernel/time/alarmtimer.c

@@ -126,6 +126,8 @@ static struct rtc_device *alarmtimer_get_rtcdev(void)
 static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
 {
 	timerqueue_add(&base->timerqueue, &alarm->node);
+	alarm->state |= ALARMTIMER_STATE_ENQUEUED;
+
 	if (&alarm->node == timerqueue_getnext(&base->timerqueue)) {
 		hrtimer_try_to_cancel(&base->timer);
 		hrtimer_start(&base->timer, alarm->node.expires,
@@ -147,7 +149,12 @@ static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
 {
 	struct timerqueue_node *next = timerqueue_getnext(&base->timerqueue);
 
+	if (!(alarm->state & ALARMTIMER_STATE_ENQUEUED))
+		return;
+
 	timerqueue_del(&base->timerqueue, &alarm->node);
+	alarm->state &= ~ALARMTIMER_STATE_ENQUEUED;
+
 	if (next == &alarm->node) {
 		hrtimer_try_to_cancel(&base->timer);
 		next = timerqueue_getnext(&base->timerqueue);
@@ -188,16 +195,18 @@ static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
 		alarm = container_of(next, struct alarm, node);
 
 		timerqueue_del(&base->timerqueue, &alarm->node);
-		alarm->enabled = 0;
+		alarm->state &= ~ALARMTIMER_STATE_ENQUEUED;
 
+		alarm->state |= ALARMTIMER_STATE_CALLBACK;
 		spin_unlock_irqrestore(&base->lock, flags);
 		if (alarm->function)
 			restart = alarm->function(alarm, now);
 		spin_lock_irqsave(&base->lock, flags);
+		alarm->state &= ~ALARMTIMER_STATE_CALLBACK;
 
 		if (restart != ALARMTIMER_NORESTART) {
 			timerqueue_add(&base->timerqueue, &alarm->node);
-			alarm->enabled = 1;
+			alarm->state |= ALARMTIMER_STATE_ENQUEUED;
 		}
 	}
 
@@ -305,7 +314,7 @@ void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
 	timerqueue_init(&alarm->node);
 	alarm->function = function;
 	alarm->type = type;
-	alarm->enabled = 0;
+	alarm->state = ALARMTIMER_STATE_INACTIVE;
 }
 
 /**
@@ -319,11 +328,10 @@ void alarm_start(struct alarm *alarm, ktime_t start)
 	unsigned long flags;
 
 	spin_lock_irqsave(&base->lock, flags);
-	if (alarm->enabled)
+	if (alarmtimer_active(alarm))
 		alarmtimer_remove(base, alarm);
 	alarm->node.expires = start;
 	alarmtimer_enqueue(base, alarm);
-	alarm->enabled = 1;
 	spin_unlock_irqrestore(&base->lock, flags);
 }
 
@@ -337,9 +345,8 @@ void alarm_cancel(struct alarm *alarm)
 	unsigned long flags;
 
 	spin_lock_irqsave(&base->lock, flags);
-	if (alarm->enabled)
+	if (alarmtimer_is_queued(alarm))
 		alarmtimer_remove(base, alarm);
-	alarm->enabled = 0;
 	spin_unlock_irqrestore(&base->lock, flags);
 }