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https://issues.apache.org/jira/browse/ZOOKEEPER-763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12864429#action_12864429
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Henry Robinson commented on ZOOKEEPER-763:
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Hi Kapil -
As seems to be the norm for me this week, I'm struggling to reproduce :) It
does seem like your python script explicitly waits for a completion to be
called before closing a handle. Is this enough to leave an outstanding
completion on the queue?
Can you capture the stacktrace for the completion thread? I think it must be
getting stuck in process_completions but it would be very valuable to know
where - if it's stuck on the callback into zkpython then that means the
deadlock is in the python bindings and not solely in C-land.
cheers,
Henry
> Deadlock on close w/ zkpython / c client
> ----------------------------------------
>
> Key: ZOOKEEPER-763
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-763
> Project: Zookeeper
> Issue Type: Bug
> Components: c client, contrib-bindings
> Affects Versions: 3.3.0
> Environment: ubuntu 10.04, zookeeper 3.3.0 and trunk
> Reporter: Kapil Thangavelu
> Assignee: Mahadev konar
> Fix For: 3.4.0
>
> Attachments: deadlock.py, stack-trace-deadlock.txt
>
>
> deadlocks occur if we attempt to close a handle while there are any
> outstanding async requests (aget, acreate, etc). Normally on close both the
> io thread terminates and the completion thread are terminated and joined,
> however w\ith outstanding async requests, the completion thread won't be in a
> joinable state, and we effectively hang when the main thread does the join.
> afaics ideal behavior would be on close of a handle, to effectively clear out
> any remaining callbacks and let the completion thread terminate.
> i've tried adding some bookkeeping to within a python client to guard against
> closing while there is an outstanding async completion request, but its an
> imperfect solution since even after the python callback is executed there is
> still a window for deadlock before the completion thread finishes the
> callback.
> a simple example to reproduce the deadlock is attached.
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