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https://issues.apache.org/jira/browse/HTTPCORE-331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13556867#comment-13556867
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Scott Stanton commented on HTTPCORE-331:
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Digging through the stacks, this is what happened in each thread:
agent-004
inputReady catches exception
HttpAsyncRequestExecutor.exception gets handler(1) from connection
closehandler calls handler(1).failed
future.failed locks (0x00000007c76d23c8)
failed calls pool release, blocks on 0x00000007363b3050
statemachine-4367
wants to send a request
calls lease on pool (acquires lock 0x00000007363b3050)
pool acquires pool lock
calls processPendingRequests
calls completed on future
calls completed on callback (locks 0x00000007c76d2508)
doExecute on a new BasicAsyncRequestExecutionHandler(1)
handler gets attached to connection
connection is not open
calls handler(1).failed
future.failed (blocks on 0x00000007c76d23c8)
statemachine-4425
blocked on lock pool for lease 0x00000007363b3050
I think the handler leaked from statemachine-4367 to agent-004 by way of the
HTTP_HANDLER on the connection.
I'm not sure why both threads are operating on the same connection, but the
locking is not ordered, so in one case the pool lock is grabbed before the
handler and in the other case the reverse is true, hence the deadlock. I think
the fact that the handlers can call into the pool and vice versa is a recipe
for deadlock. I have no idea how to resolve any of this, though.
> deadlock in AbstractNIOConnPool
> -------------------------------
>
> Key: HTTPCORE-331
> URL: https://issues.apache.org/jira/browse/HTTPCORE-331
> Project: HttpComponents HttpCore
> Issue Type: Bug
> Components: HttpCore NIO
> Affects Versions: 4.2.4
> Environment: jjdk 1.7.0_u10
> Reporter: Scott Stanton
> Priority: Blocker
> Attachments: stacks
>
>
> I have run into a deadlock in the AbstractNIOConnPool. I have attached the
> deadlock stacks. I'm not entirely sure what's going on yet, but it appears
> that nested futures are causing lock ordering problems.
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