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https://issues.apache.org/jira/browse/HDFS-1257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12887506#action_12887506
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Hairong Kuang commented on HDFS-1257:
-------------------------------------
RecentInvalidateSets were protected by FSNamesystem lock. It seems to me that
the ConcurrentModificationException might be caused by computeInvalidateWork
accessing recentInvalidateSets without holding FsNamesystem lock. The following
code should be surrounded by "synchronized (this)".
{code}
int numOfNodes = recentInvalidateSets.size();
nodesToProcess = Math.min(numOfNodes, nodesToProcess);
// get an array of the keys
ArrayList<String> keyArray =
new ArrayList<String>(recentInvalidateSets.keySet());
{code}
> Race condition introduced by HADOOP-5124
> ----------------------------------------
>
> Key: HDFS-1257
> URL: https://issues.apache.org/jira/browse/HDFS-1257
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: Ramkumar Vadali
>
> HADOOP-5124 provided some improvements to FSNamesystem#recentInvalidateSets.
> But it introduced unprotected access to the data structure
> recentInvalidateSets. Specifically, FSNamesystem.computeInvalidateWork
> accesses recentInvalidateSets without read-lock protection. If there is
> concurrent activity (like reducing replication on a file) that adds to
> recentInvalidateSets, the name-node crashes with a
> ConcurrentModificationException.
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