Two PrepareCommands in parallel cause ConcurrentModificationException --------------------------------------------------------------------- Key: ISPN-2578 URL: https://issues.jboss.org/browse/ISPN-2578 Project: Infinispan Issue Type: Bug Affects Versions: 5.2.0.Beta5 Reporter: Radim Vansa Assignee: Adrian Nistor Priority: Critical Fix For: 5.2.0.Final Situation: 1) Node A broadcasts PrepareCommand to nodes B, C 2) Node A leaves cluster, causing new topology to be installed 3) The command arrives to B and C, with lower topology than the current one 4) Both B and C forward the command to node D 5) D executes the two commands in parallel and finds out that A has left, therefore executing RollbackCommand In {{AbstractTxLockingInterceptor.visitRollbackCommand}} we call {{LockManagerImpl.unlockAll}} which iterates over the keys and unlocks them. As these two prepares aren't synchronized over the {{lockedKeys}} set, one may unlock and remove these keys while the other is iterating through them, causing {{ConcurrentModificationException}}.