[jboss-jira] [JBoss JIRA] Closed: (JGRP-750) Deadlock between GroupRequest and FLUSH during concurrent startup.

Deadlock between GroupRequest and FLUSH during concurrent startup. ------------------------------------------------------------------ Key: JGRP-750 URL: http://jira.jboss.com/jira/browse/JGRP-750 Project: JGroups Issue Type: Bug Affects Versions: 2.6.3 Environment: Debian etch (i386), Java HotSpot(TM) Server VM (build 1.6.0-b105, mixed mode) Reporter: Robert Newson Assigned To: Bela Ban Fix For: 2.6.3, 2.7 Attachments: ConcurrentStartupWithGroupRequestTest.java, ConcurrentStartupWithGroupRequestTest.java, stacktrace.txt We've been having more trouble with concurrent start up and now think we've isolated a deadlock between FLUSH and GroupRequest during concurrent startup. We have four boxes that join a channel and use MessageDispatcher immediately after connecting. This frequently blocks indefinitely. GroupRequest.execute() obtains a lock, then a subsequent view change comes in which does likewise. The upshot is that we can see all Incoming threads are blocked for the lock and the only way it can be released is for a stop_flush message to occur. With all incoming threads blocked, that never happens. In the attached unit test if you add this after the call to connect("A"), it passes, implying a deadlock; if (j ==0) { Thread.sleep(500); } Additionally, and this is more speculative, it seems the wait/notify code in pbcast does not account for the spurious wakeup case. I don't know under what circumstances they happen, and I don't believe we're seeing spurious wakes at this time, but it should be fixed at some stage.