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https://issues.apache.org/jira/browse/AMQ-4935?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Yara updated AMQ-4935:
------------------------------

    Component/s:     (was: activemq-pool)
                 Broker

> Deadlock caused by Re-entrant lock with no locking thread
> ---------------------------------------------------------
>
>                 Key: AMQ-4935
>                 URL: https://issues.apache.org/jira/browse/AMQ-4935
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.9.0
>         Environment: Oracle JRE 1.7.0 update 45
>            Reporter: Michael Yara
>
> We have a distributed application that uses ActiveMQ for communication 
> between nodes. We are currently using ActiveMQ 5.9.0 running with Oracle JRE 
> 1.7.0 update 45. 
> We are seeing some strange deadlock behavior in the ActiveMQ 
> ThreadPoolExecutor when trying to serialize instances of ConcurrentHashMap. 
> The thread dump can be seen at the following link:
> http://pastebin.com/wmNxSF4p
> We can see that there are two threads that are blocked waiting for a lock on 
> some of the segments in a ConcurrentHashMap yet the thread dump does not 
> indicate any threads that currently hold a lock on those objects. This lock 
> does not occur all the time and can take around 5-10 messages before the 
> deadlock occurs. I have been able to recreate this issue on two different 
> physical machines.
> Our test environment that generated this thread dump is as follows. Node A is 
> the instance that thread dump was taken from. For testing both nodes are on 
> the same physical machine.
> Node A:
> * In its own JVM instance.
> * Runs an embedded ActiveMQ broker.
> * Performs communication via vm transport and sends ObjectMessages via a 
> TopicConnection.
> * Has copyMessageOnSend=false
> * Has ObjectMessageSerializationDefered=true
> Node B:
> * In its own JVM instance.
> * Connects to Node A's broker via tcp transport.
> * Sends BytesMessages serialized with Kryo and sent via a TopicConnection.
> * Has copyMessageOnSend=false
> * Has ObjectMessageSerializationDefered=false
> Both nodes are set up to detect the type of incoming messages and deserialize 
> them appropriately with kryo if it receives a BytesMessage or default 
> serialization if it receives an ObjectMessage (handled by ActiveMQ).
> The only thing I have found resembling this issue is the following link. I am 
> no sure if it is related to this exact problem or not.
> http://appcrawler.com/wordpress/2013/05/06/one-way-to-tell-if-a-thread-pool-is-hung/



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