Ted Yu created KYLIN-2874:
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Summary: 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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