LISTENER WAS HANG AND WAS NOT ALLOWING NEW CONNECTIONS

This issue occurred last friday as well. Listener was hung and was not allowing connections. When you attempt to connect
via the listener or check the listener status it would hang the connection and
not respond. I identified the listener and killed the process. I was logged in
as the oracle account so I was then able to start the listener:

I have do some change as Note 340091.1:
1.add the parameter to listener.ora
SUBSCRIBE_FOR_NODE_DOWN_EVENT_LISTENER=OFF
2. Locate the ons.config file in the 10g(rdbms) home and rename it to something else.
For example:
cd $ORACLE_HOME/opmn/conf
mv ons.config ons.config.orig
restart listener .