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https://issues.apache.org/jira/browse/KYLIN-2874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16196017#comment-16196017
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liyang commented on KYLIN-2874:
-------------------------------
ref http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
> Ineffective check in CubeDesc#getInitialCuboidScheduler
> -------------------------------------------------------
>
> Key: KYLIN-2874
> URL: https://issues.apache.org/jira/browse/KYLIN-2874
> Project: Kylin
> Issue Type: Bug
> Reporter: Ted Yu
>
> {code}
> public CuboidScheduler getInitialCuboidScheduler() {
> if (cuboidScheduler != null)
> return cuboidScheduler;
> synchronized (this) {
> if (cuboidScheduler == null) {
> cuboidScheduler = CuboidScheduler.getInstance(this);
> }
> {code}
> Suppose thread 1 obtains the lock and modifies cuboidScheduler.
> This modification can be re-ordered with other correlated field assignments
> within this critical section at runtime. Thus, checking the value of
> cuboidScheduler is not an effective test that the critical section has
> completed unless the guarding lock is held while checking.
> When cuboidScheduler is assigned a newly constructed value, the JVM is
> allowed to reorder the assignment of the new reference to cuboidScheduler
> before any field assignments that may occur in the constructor.
> If thread 2 comes and read cuboidScheduler, it may use partially initialized
> object.
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