Thread safety issues and race conditions in VERIFY_SUSPECT ---------------------------------------------------------- Key: JGRP-2287 URL: https://issues.jboss.org/browse/JGRP-2287 Project: JGroups Issue Type: Bug Affects Versions: 4.0.13 Reporter: Paul Ferraro Assignee: Bela Ban Priority: Critical Fix For: 4.0.16 While addressing JGRP-2286, I noticed a number of thread safety issues and race conditions in VERIFY_SUSPECT, e.g. 1. "suspects" DelayQueue is accessed concurrently within synchronized block by most of the code, however, the run() method calls isEmpty(), size(), and most notably, drainTo(...) without sufficient exclusivity. drainTo is particularly problematic in the case of concurrent modifications. 2. "timer" Thread is non-volatile, but its reference is set by multiple threads. 3. The startTimer() method only creates a new thread if Thread.isAlive() returns false. However, if the thread is just completing (i.e. exiting its loop), this method can return true, and the verification of suspected members can be delayed until the next suspect event.