When using a standalone client to make EJB calls to EAP it seems that those threads can get stuck in an indefinite wait state. This occurs when the client hits invocation.timeout. The server continues processes the request and that thread lingers waiting to return a respond to the client, which is no longer listening. This looks similar to EJBCLIENT-42, but not quite the same. I will attach a reproducer which was created from a quickstart. Note that when the client is killed, the server side throws various exceptions for all threads, including the writes closed exception.
Setting to MODIFIED since should be solved by ejb-client 1.0.26 upgrade (https://bugzilla.redhat.com/show_bug.cgi?id=1104257)
Verified in EAP 6.4.0.DR1.1 / ejb client 1.0.26.Final-redhat-1