The Barracuda code is protected by one single lock, the SoDisp mutex. Callback functions, running in the context of the SoDisp or from a thread in the HttpCmdThreadPool, have this mutex locked. The HttpDir and HttpPage service functions are examples of callback functions running in a context of the dispatcher. These callback functions or any code running in the context of the dispatcher need normally not be concerned about the SoDisp mutex. However, any code running from other threads or from the thread running the dispatcher itself must explicitly set this lock prior to calling any Barracuda functions.