The command executor thread is expected to be running for any signal processing to happen in async environment.
There is no configuration required to run it. AFAIK.
Can you specify which version of jbpm are you using?
I'm using Jbpm3.1.
I found that log4j.xml in Jboss need to change to TRACE level, so that the CommandExecutorThread can print the output in console.
The JbpmThreadsServlet and JbpmContextFilter are also required in the web.xml