[jboss-jira] [JBoss JIRA] Closed: (JBMESSAGING-1793) Non-atomic increment operation on volatile field lastReceivedCommandID in class ChannelImpl

Non-atomic increment operation on volatile field lastReceivedCommandID in class ChannelImpl ------------------------------------------------------------------------------------------- Key: JBMESSAGING-1793 URL: https://jira.jboss.org/jira/browse/JBMESSAGING-1793 Project: JBoss Messaging Issue Type: Bug Components: Messaging Core Affects Versions: 2.0.0.beta4 Environment: OS: Redhat-5 Linux 2.6.18-92.el5 JDK: java version "1.6.0" Java(TM) SE Runtime Environment (build pxi3260sr4-20090219_01(SR4)) IBM J9 VM (build 2.4, J2RE 1.6.0 IBM J9 2.4 Linux x86-32 jvmxi3260-20090215_29883 (JIT enabled, AOT enabled) J9VM - 20090215_029883_lHdSMr JIT - r9_20090213_2028 GC - 20090213_AA) JCL - 20090218_01 Reporter: Daniel Luo Original Estimate: 15 minutes Remaining Estimate: 15 minutes In class ChannelImpl, field "lastReceivedCommandID" is declared as volatile int, in method confirm(xxx), lastReceivedCommandID++; is seen, which is a three-step (read->modify->write) non-atomic operation. Volatile keyword only guarantees variable visibility, but not atomicity, so statement "lastReceivedCommandID++;" invoked by multiple threads can result to race condition and incorrect result. It's suggested to use synchronized block to protect "lastReceivedCommandID++;" or AtomicInteger class from java.util.concurrent package to do atomic increment operation.