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https://issues.apache.org/jira/browse/HADOOP-9748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13853538#comment-13853538
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Todd Lipcon commented on HADOOP-9748:
-------------------------------------
It's probably really really hard to trigger, but I think this double-checked
locking isn't quite correct -- the initialize() function is free to make the
conf member visible to other threads before the object is fully initialized. I
think to make it safe you need to do a write to a volatile variable in
initialize to ensure memory ordering. Thoughts?
> Reduce blocking on UGI.ensureInitialized
> ----------------------------------------
>
> Key: HADOOP-9748
> URL: https://issues.apache.org/jira/browse/HADOOP-9748
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: security
> Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Priority: Critical
> Fix For: 3.0.0, 2.4.0, 0.23.10
>
> Attachments: HADOOP-9748.branch-23.patch,
> HADOOP-9748.branch-23.patch, HADOOP-9748.patch, HADOOP-9748.patch
>
>
> EnsureInitialized is always sync'ed on the class, when it should only sync if
> it actually has to initialize.
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