Input: atkbd - fix canceling event_work in disconnect

We need to first unregister input device and only then cancel event work
since events can arrive (and cause event work to get scheduled again)
until input_unregister_device() returns.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/keyboard/atkbd.c

@@ -855,10 +855,16 @@ static void atkbd_disconnect(struct serio *serio)
 
 	atkbd_disable(atkbd);
 
-	/* make sure we don't have a command in flight */
+	input_unregister_device(atkbd->dev);
+
+	/*
+	 * Make sure we don't have a command in flight.
+	 * Note that since atkbd->enabled is false event work will keep
+	 * rescheduling itself until it gets canceled and will not try
+	 * accessing freed input device or serio port.
+	 */
 	cancel_delayed_work_sync(&atkbd->event_work);
 
-	input_unregister_device(atkbd->dev);
 	serio_close(serio);
 	serio_set_drvdata(serio, NULL);
 	kfree(atkbd);