add explanatory comment

diff --git a/libs/ardour/port_manager.cc b/libs/ardour/port_manager.cc
index ec8e3024eafd668fc9027ead4b44c6f0eba4e795..10c19a9c67547f4cd07aecbdec4f05185a06e50e 100644 (file)
--- a/libs/ardour/port_manager.cc
+++ b/libs/ardour/port_manager.cc
@@ -353,6 +353,12 @@ PortManager::register_output_port (DataType type, const string& portname, bool a
 int
 PortManager::unregister_port (boost::shared_ptr<Port> port)
 {
+       /* This is a little subtle. We do not call the backend's port
+        * unregistration code from here. That is left for the Port
+        * destructor. We are trying to drop references to the Port object
+        * here, so that its destructor will run and it will unregister itself.
+        */
+
        /* caller must hold process lock */
 
        {