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https://issues.apache.org/jira/browse/OGNL-20?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13108221#comment-13108221
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Adrian Crum commented on OGNL-20:
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That pattern (DCL) should not be used:
http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
The safest thing to do is use ConcurrentHashMap. The other two cache
implementations have concurrency issues. If you can't see what those issues
are, then perhaps it is time to re-read that book.
> Performance - Replace synchronized blocks with ReentrantReadWriteLock
> ---------------------------------------------------------------------
>
> Key: OGNL-20
> URL: https://issues.apache.org/jira/browse/OGNL-20
> Project: OGNL
> Issue Type: Improvement
> Environment: ALL
> Reporter: Greg Lively
> Attachments: Bench Results.txt, Caching_Mechanism_Benchmarks.patch
>
>
> I've noticed a lot of synchronized blocks of code in OGNL. For the most part,
> these synchronized blocks are controlling access to HashMaps, etc. I believe
> this could be done far better using ReentrantReadWriteLocks.
> ReentrantReadWriteLock allows unlimited concurrent access, and single threads
> only for writes. Perfect in an environment where the ratio of reads is far
> higher than writes; which is typically the scenario for caching. Plus the
> access control can be tuned for reads and writes; not just a big
> synchronized{} wrapping a bunch of code.
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