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https://issues.apache.org/jira/browse/IGNITE-6736?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16292218#comment-16292218
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Andrey Kuznetsov commented on IGNITE-6736:
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Choosing ReentrantLock approach. See [1].
[1]
http://apache-ignite-developers.2346864.n4.nabble.com/Separate-code-paths-for-Java-8-and-Java-9-tp25289p25291.html
> Java 9: rework GridCacheMapEntry synchronization logic to avoid
> Unsafe.monitor* methods
> ---------------------------------------------------------------------------------------
>
> Key: IGNITE-6736
> URL: https://issues.apache.org/jira/browse/IGNITE-6736
> Project: Ignite
> Issue Type: Task
> Components: cache
> Reporter: Vladimir Ozerov
> Fix For: 2.4
>
>
> {{GridCacheMapEntry}} class rely on {{synchronized}} on itself heavily. In
> {{ATOMIC}} caches we lock multiple entries at once using
> {{Unsafe.monitorEnter/Exit}} methods. Unfortunately these methods were
> removed in Java 9. Recursion is not an option, as it would cause stack
> overflow for {{putAll}} operations with multiple entries.
> Possible fixes:
> 1) Rework {{synchronized}} to {{ReentrantLock}}. Easy, but may cause
> additional memory pressure.
> 2) Have different implementations for Java 8 ({{synchronzied}}) and Java 9
> ({{ReentrantLock}}) - much more complex solution, because we will require
> separate module for Java 8 and Java 9.
> 3) Rework {{ATOMIC}} caches, so that {{putAll}} operation updates entries
> one-by-one. As a side effect it will eliminate deadlocks.
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