Issue

Potential for deadlock when duplicates read in from store for DLQ destination itself and another producer is trying to send messages from the DLQ destination.
It can result with threads in following state

Found one Java-level deadlock:
=============================
"ActiveMQ Transport: tcp:///127.0.0.1:59885@59875":
  waiting for ownable synchronizer 0x00000007f6188490, (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync),
  which is held by "ActiveMQ BrokerService[localhost] Task-1"
"ActiveMQ BrokerService[localhost] Task-1":
  waiting for ownable synchronizer 0x00000007f6190cf8, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
  which is held by "ActiveMQ Transport: tcp:///127.0.0.1:59885@59875"

Java stack information for the threads listed above:
===================================================
"ActiveMQ Transport: tcp:///127.0.0.1:59885@59875":
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x00000007f6188490> (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(AbstractQueuedSynchronizer.java:964)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1282)
    at java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:731)
    at org.apache.activemq.broker.region.Queue.toString(Queue.java:937)
    at org.apache.activemq.broker.region.Queue.doMessageSend(Queue.java:830)
    at org.apache.activemq.broker.region.Queue.send(Queue.java:728)
    at org.apache.activemq.broker.region.AbstractRegion.send(AbstractRegion.java:390)
    at org.apache.activemq.broker.region.RegionBroker.send(RegionBroker.java:455)
    at org.apache.activemq.broker.jmx.ManagedRegionBroker.send(ManagedRegionBroker.java:297)
    at org.apache.activemq.broker.CompositeDestinationBroker.send(CompositeDestinationBroker.java:96)
    at org.apache.activemq.broker.TransactionBroker.send(TransactionBroker.java:307)
    at org.apache.activemq.broker.MutableBrokerFilter.send(MutableBrokerFilter.java:157)
    at org.apache.activemq.broker.TransportConnection.processMessage(TransportConnection.java:541)
    at org.apache.activemq.command.ActiveMQMessage.visit(ActiveMQMessage.java:756)
    at org.apache.activemq.broker.TransportConnection.service(TransportConnection.java:334)
    at org.apache.activemq.broker.TransportConnection$1.onCommand(TransportConnection.java:188)
    at org.apache.activemq.transport.MutexTransport.onCommand(MutexTransport.java:50)
    at org.apache.activemq.transport.WireFormatNegotiator.onCommand(WireFormatNegotiator.java:113)
    at org.apache.activemq.transport.AbstractInactivityMonitor.onCommand(AbstractInactivityMonitor.java:270)
    at org.apache.activemq.transport.TransportSupport.doConsume(TransportSupport.java:83)
    at org.apache.activemq.transport.tcp.TcpTransport.doRun(TcpTransport.java:214)
    at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:196)
    at java.lang.Thread.run(Thread.java:722)
"ActiveMQ BrokerService[localhost] Task-1":
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x00000007f6190cf8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:894)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1221)
    at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:340)
    at org.apache.activemq.broker.region.Queue.doMessageSend(Queue.java:828)
    at org.apache.activemq.broker.region.Queue.send(Queue.java:728)
    at org.apache.activemq.broker.region.AbstractRegion.send(AbstractRegion.java:390)
    at org.apache.activemq.broker.region.RegionBroker.send(RegionBroker.java:455)
    at org.apache.activemq.broker.jmx.ManagedRegionBroker.send(ManagedRegionBroker.java:297)
    at org.apache.activemq.broker.CompositeDestinationBroker.send(CompositeDestinationBroker.java:96)
    at org.apache.activemq.broker.TransactionBroker.send(TransactionBroker.java:307)
    at org.apache.activemq.broker.MutableBrokerFilter.send(MutableBrokerFilter.java:157)
    at org.apache.activemq.util.BrokerSupport.doResend(BrokerSupport.java:68)
    at org.apache.activemq.util.BrokerSupport.resendNoCopy(BrokerSupport.java:38)
    at org.apache.activemq.broker.region.RegionBroker.sendToDeadLetterQueue(RegionBroker.java:762)
    at org.apache.activemq.broker.BrokerFilter.sendToDeadLetterQueue(BrokerFilter.java:318)
    at org.apache.activemq.broker.BrokerFilter.sendToDeadLetterQueue(BrokerFilter.java:318)
    at org.apache.activemq.broker.MutableBrokerFilter.sendToDeadLetterQueue(MutableBrokerFilter.java:330)
    at org.apache.activemq.broker.region.BaseDestination.duplicateFromStore(BaseDestination.java:801)
    at org.apache.activemq.broker.region.cursors.AbstractStoreCursor.dealWithDuplicates(AbstractStoreCursor.java:134)
    at org.apache.activemq.broker.region.cursors.QueueStorePrefetch.doFillBatch(QueueStorePrefetch.java:110)
    at org.apache.activemq.broker.region.cursors.AbstractStoreCursor.fillBatch(AbstractStoreCursor.java:385)
    - locked <0x00000007f6188550> (a org.apache.activemq.broker.region.cursors.QueueStorePrefetch)
    at org.apache.activemq.broker.region.cursors.AbstractStoreCursor.reset(AbstractStoreCursor.java:142)
    - locked <0x00000007f6188550> (a org.apache.activemq.broker.region.cursors.QueueStorePrefetch)
    at org.apache.activemq.broker.region.cursors.StoreQueueCursor.reset(StoreQueueCursor.java:159)
    - locked <0x00000007f61885a8> (a org.apache.activemq.broker.region.cursors.StoreQueueCursor)
    at org.apache.activemq.broker.region.Queue.doPageInForDispatch(Queue.java:1906)
    at org.apache.activemq.broker.region.Queue.pageInMessages(Queue.java:2127)
    at org.apache.activemq.broker.region.Queue.iterate(Queue.java:1608)
    - locked <0x00000007f61885f8> (a java.lang.Object)
    at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:133)
    at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:48)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

Found 1 deadlock.