When stop operation with waittime=0 is called on a mod_cluster node, it wait indefinitely until all sessions time out. However, following line appears in log:

INFO  [org.jboss.modcluster] (management-handler-thread - 1) MODCLUSTER000046: Starting to drain 1 active sessions from default-host:/karel in 0 seconds.

This could confuse someone looking into the log – they would then think,that this operation killed sessions even when it didn't.

Suggestion: Replace this message with more accurate one.