PM / Sleep: Prevent waiting forever on asynchronous suspend after abort

commit 1f758b23 upstream.

__device_suspend() must always send a completion. Otherwise, parent
devices will wait forever.

Commit 1e2ef05b, "PM: Limit race conditions between runtime PM and
system sleep (v2)", introduced a regression by short-circuiting the
complete_all() for certain error cases.

This patch fixes the bug by always signalling a completion.

Addresses http://crosbug.com/31972

Tested by injecting an abort.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/base/power/main.c

@@ -869,7 +869,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	dpm_wait_for_children(dev, async);
 
 	if (async_error)
-		return 0;
+		goto Complete;
 
 	pm_runtime_get_noresume(dev);
 	if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
@@ -878,7 +878,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	if (pm_wakeup_pending()) {
 		pm_runtime_put_sync(dev);
 		async_error = -EBUSY;
-		return 0;
+		goto Complete;
 	}
 
 	device_lock(dev);
@@ -926,6 +926,8 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 	}
 
 	device_unlock(dev);
+
+ Complete:
 	complete_all(&dev->power.completion);
 
 	if (error) {