clockevents: make device shutdown robust

The device shut down does not cleanup the next_event variable of the
clock event device. So when the device is reactivated the possible
stale next_event value can prevent the device to be reprogrammed as it
claims to wait on a event already.

This is the root cause of the resurfacing suspend/resume problem,
where systems need key press to come back to life.

Fix this by setting next_event to KTIME_MAX when the device is shut
down. Use a separate function for shutdown which takes care of that
and only keep the direct set mode call in the broadcast code, where we
can not touch the next_event value.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/time/clockevents.c

@@ -71,6 +71,16 @@ void clockevents_set_mode(struct clock_event_device *dev,
 	}
 }
 
+/**
+ * clockevents_shutdown - shutdown the device and clear next_event
+ * @dev:	device to shutdown
+ */
+void clockevents_shutdown(struct clock_event_device *dev)
+{
+	clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
+	dev->next_event.tv64 = KTIME_MAX;
+}
+
 /**
  * clockevents_program_event - Reprogram the clock event device.
  * @expires:	absolute expiry time (monotonic clock)
@@ -206,7 +216,7 @@ void clockevents_exchange_device(struct clock_event_device *old,
 
 	if (new) {
 		BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
-		clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
+		clockevents_shutdown(new);
 	}
 	local_irq_restore(flags);
 }

kernel/time/tick-broadcast.c

@@ -236,8 +236,7 @@ static void tick_do_broadcast_on_off(void *why)
 		if (!cpu_isset(cpu, tick_broadcast_mask)) {
 			cpu_set(cpu, tick_broadcast_mask);
 			if (td->mode == TICKDEV_MODE_PERIODIC)
-				clockevents_set_mode(dev,
-						     CLOCK_EVT_MODE_SHUTDOWN);
+				clockevents_shutdown(dev);
 		}
 		if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 			tick_broadcast_force = 1;
@@ -254,7 +253,7 @@ static void tick_do_broadcast_on_off(void *why)
 
 	if (cpus_empty(tick_broadcast_mask)) {
 		if (!bc_stopped)
-			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
+			clockevents_shutdown(bc);
 	} else if (bc_stopped) {
 		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 			tick_broadcast_start_periodic(bc);
@@ -306,7 +305,7 @@ void tick_shutdown_broadcast(unsigned int *cpup)
 
 	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 		if (bc && cpus_empty(tick_broadcast_mask))
-			clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
+			clockevents_shutdown(bc);
 	}
 
 	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
@@ -321,7 +320,7 @@ void tick_suspend_broadcast(void)
 
 	bc = tick_broadcast_device.evtdev;
 	if (bc)
-		clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
+		clockevents_shutdown(bc);
 
 	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }

kernel/time/tick-common.c

@@ -249,7 +249,7 @@ static int tick_check_new_device(struct clock_event_device *newdev)
 	 * not give it back to the clockevents layer !
 	 */
 	if (tick_is_broadcast_device(curdev)) {
-		clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
+		clockevents_shutdown(curdev);
 		curdev = NULL;
 	}
 	clockevents_exchange_device(curdev, newdev);
@@ -311,7 +311,7 @@ static void tick_suspend(void)
 	unsigned long flags;
 
 	spin_lock_irqsave(&tick_device_lock, flags);
-	clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
+	clockevents_shutdown(td->evtdev);
 	spin_unlock_irqrestore(&tick_device_lock, flags);
 }
 

kernel/time/tick-internal.h

@@ -10,6 +10,8 @@ extern int tick_do_timer_cpu __read_mostly;
 extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
 extern void tick_handle_periodic(struct clock_event_device *dev);
 
+extern void clockevents_shutdown(struct clock_event_device *dev);
+
 /*
  * NO_HZ / high resolution timer shared code
  */