PM / Runtime: don't forget to wake up waitqueue on failure

This patch (as1535) fixes a bug in the runtime PM core.  When a
runtime suspend attempt completes, whether successfully or not, the
device's power.wait_queue is supposed to be signalled.  But this
doesn't happen in the failure pathway of rpm_suspend() when another
autosuspend attempt is rescheduled.  As a result, a task can get stuck
indefinitely on the wait queue (I have seen this happen in testing).

The patch fixes the problem by moving the wake_up_all() call up near
the start of the failure code.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

drivers/base/power/runtime.c

@@ -532,6 +532,8 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 	dev->power.suspend_time = ktime_set(0, 0);
 	dev->power.max_time_suspended_ns = -1;
 	dev->power.deferred_resume = false;
+	wake_up_all(&dev->power.wait_queue);
+
 	if (retval == -EAGAIN || retval == -EBUSY) {
 		dev->power.runtime_error = 0;
 
@@ -547,7 +549,6 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 	} else {
 		pm_runtime_cancel_pending(dev);
 	}
-	wake_up_all(&dev->power.wait_queue);
 	goto out;
 }