[jboss-jira] [JBoss JIRA] (JGRP-1918) ConcurrentModificationException in Locking notification

ConcurrentModificationException in Locking notification ------------------------------------------------------- Key: JGRP-1918 URL: https://issues.jboss.org/browse/JGRP-1918 Project: JGroups Issue Type: Bug Affects Versions: 3.6.2 Environment: JUnit text running in Eclipse on Windows Reporter: Paul Illingworth Assignee: Bela Ban Fix For: 3.6.3 I have code which unregisters a lock listener whilst a lock notification event is being fired leading to java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextEntry(HashMap.java:926) at java.util.HashMap$KeyIterator.next(HashMap.java:960) at org.jgroups.protocols.Locking.notifyUnlocked(Locking.java:581) at org.jgroups.protocols.Locking$ServerLock.setOwner(Locking.java:767) at org.jgroups.protocols.Locking$ServerLock.handleRequest(Locking.java:655) at org.jgroups.protocols.Locking.handleLockRequest(Locking.java:393) at org.jgroups.protocols.Locking.up(Locking.java:226) at org.jgroups.stack.Protocol.up(Protocol.java:412) at org.jgroups.protocols.FORK.up(FORK.java:139) at org.jgroups.protocols.FRAG2.up(FRAG2.java:182) at org.jgroups.protocols.FlowControl.up(FlowControl.java:447) at org.jgroups.protocols.FlowControl.up(FlowControl.java:447) at org.jgroups.stack.Protocol.up(Protocol.java:420) at org.jgroups.protocols.pbcast.STABLE.up(STABLE.java:294) at org.jgroups.protocols.UNICAST3.deliverBatch(UNICAST3.java:1087) at org.jgroups.protocols.UNICAST3.removeAndDeliver(UNICAST3.java:886) at org.jgroups.protocols.UNICAST3.handleDataReceivedFromSelf(UNICAST3.java:821) at org.jgroups.protocols.UNICAST3.up(UNICAST3.java:424) at org.jgroups.protocols.pbcast.NAKACK2.up(NAKACK2.java:652) at org.jgroups.protocols.VERIFY_SUSPECT.up(VERIFY_SUSPECT.java:155) at org.jgroups.protocols.FD.up(FD.java:253) at org.jgroups.protocols.FD_SOCK.up(FD_SOCK.java:297) at org.jgroups.protocols.MERGE3.up(MERGE3.java:288) at org.jgroups.protocols.Discovery.up(Discovery.java:291) at org.jgroups.protocols.TP$ProtocolAdapter.up(TP.java:2842) at org.jgroups.protocols.TP.passMessageUp(TP.java:1577) at org.jgroups.protocols.TP$3.run(TP.java:1511) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:724) The org.jgroups.protocols.Locking#lock_listeners is simple a HashSet which gets iterated over, This needs to be synchronised is some way.