Using TNonblockingServer, when the number of IO threads is > 1, there is race condition in which stop() does not properly unblock serve().
The problem manifests itself when stop() is called (obviously from a different thread) soon after serve().
The core issue is that, event_base_loopbreak() is called within the stop() sequence without checking whether the IO thread has actually entered its event loop. The documentation of event_base_loopbreak() says (http://www.wangafu.net/~nickm/libevent-book/Ref3_eventloop.html)
Note also that event_base_loopexit(base,NULL) and event_base_loopbreak(base) act differently when no event loop is running: loopexit schedules the next instance of the event loop to stop right after the next round of callbacks are run (as if it had been invoked with EVLOOP_ONCE) whereas loopbreak only stops a currently running loop, and has no effect if the event loop isn’t running.
Attached is a patch (against the released 0.9.3 version of the codebase).