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Sangjin Lee commented on MAPREDUCE-5861: ---------------------------------------- It was made volatile as part of MAPREDUCE-5841. However, before that patch the subtask runner was single-threaded. So, I don't think volatile was necessary then (it is now). > LocalContainerLauncher does not atomically update volatile variable > finishedSubMaps > ----------------------------------------------------------------------------------- > > Key: MAPREDUCE-5861 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-5861 > Project: Hadoop Map/Reduce > Issue Type: Bug > Reporter: Ted Yu > Priority: Minor > > Around line 374: > {code} > if (++finishedSubMaps == numMapTasks) { > doneWithMaps = true; > } > {code} > The increment of finishedSubMaps is not atomic. > See the answer to > http://stackoverflow.com/questions/9749746/what-is-the-difference-of-atomic-volatile-synchronize > . > AtomicInteger can be used to achieve atomicity. -- This message was sent by Atlassian JIRA (v6.2#6252)