clockevents: prevent endless loop in periodic broadcast handler

The reprogramming of the periodic broadcast handler was broken, when the first programming returned -ETIME. The clockevents code stores the new expiry value in the clock events device next_event field only when the programming time has not been elapsed yet. The loop in question calculates the new expiry value from the next_event value and therefor never increases. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>

clockevents: prevent endless loop in periodic broadcast handler
The reprogramming of the periodic broadcast handler was broken, when the first programming returned -ETIME. The clockevents code stores the new expiry value in the clock events device next_event field only when the programming time has not been elapsed yet. The loop in question calculates the new expiry value from the next_event value and therefor never increases. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Thomas Gleixner
1 parent 7c1e768974
Showing 1 changed file with 8 additions and 3 deletions Side-by-side Diff
kernel/time/tick-broadcast.c
@@ -175,6 +175,8 @@
  */
 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 {
+	ktime_t next;
+
 	tick_do_periodic_broadcast();
  
 	/*
  
@@ -185,10 +187,13 @@
  
 	/*
 	 * Setup the next period for devices, which do not have
-	 * periodic mode:
+	 * periodic mode. We read dev->next_event first and add to it
+	 * when the event alrady expired. clockevents_program_event()
+	 * sets dev->next_event only when the event is really
+	 * programmed to the device.
 	 */
-	for (;;) {
-		ktime_t next = ktime_add(dev->next_event, tick_period);
+	for (next = dev->next_event; ;) {
+		next = ktime_add(next, tick_period);
  
 		if (!clockevents_program_event(dev, next, ktime_get()))
 			return;
...	...	@@ -175,6 +175,8 @@
175	175	*/
176	176	static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
177	177	{
	178	+ ktime_t next;
	179	+
178	180	tick_do_periodic_broadcast();
179	181
180	182	/*
181	183
...	...	@@ -185,10 +187,13 @@
185	187
186	188	/*
187	189	* Setup the next period for devices, which do not have
188		- * periodic mode:
	190	+ * periodic mode. We read dev->next_event first and add to it
	191	+ * when the event alrady expired. clockevents_program_event()
	192	+ * sets dev->next_event only when the event is really
	193	+ * programmed to the device.
189	194	*/
190		- for (;;) {
191		- ktime_t next = ktime_add(dev->next_event, tick_period);
	195	+ for (next = dev->next_event; ;) {
	196	+ next = ktime_add(next, tick_period);
192	197
193	198	if (!clockevents_program_event(dev, next, ktime_get()))
194	199	return;