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https://issues.apache.org/jira/browse/POOL-149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12746738#action_12746738
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shuyang.zhou commented on POOL-149:
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And this bug should be called resource leak, not deadlock. My bad.
Finally all threads try to borrow objects from the empty pool will block
indefinitely.
> A serious concurrent bug can cause deadlock when Pool exhausted and borrowed
> objects are invalid
> ------------------------------------------------------------------------------------------------
>
> Key: POOL-149
> URL: https://issues.apache.org/jira/browse/POOL-149
> Project: Commons Pool
> Issue Type: Bug
> Reporter: shuyang.zhou
> Priority: Critical
> Attachments: BugTest.java
>
>
> This bug will happen when the pool is in exhausted state and the borrowed
> object are invalid.
> Let's go through a simple scenario:
> 1)A GenericObjectPool with _maxActive==1,
> whenExhaustedAction==WHEN_EXHAUSTED_BLOCK
> 2)Two threads using that pool, called thread1 and thread2
> Here is error path:
> 1)thread1 calls pool.borrowObject() to get the object out of the pool
> //now the pool is exhausted
> 2)thread2 calls pool.borrowObject(), adds a new latch to the
> _allocationQueue, but before it enters the synchronized block for
> WHEN_EXHAUSTED_BLOCK(GenericObjectPool line 1099 revision 806215),
> context-switch happens
> 3)thread1 checks the object from pool, and decides to invalidate it. So it
> calls pool.invalidateObject(), which calls allocate(), then calls
> latch.notify(), but currently no thread is waiting on this latch.(thread2 has
> not enter the wait synchronized block yet).
> 4)Then thread2 will wait there for ever.(it just missed the notify)
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