Found one Java-level deadlock:
=============================
"MQTTInactivityMonitor Async Task: java.util.concurrent.ThreadPoolExecutor$Worker@7e51223f[State = -1, empty queue]":
  waiting to lock monitor 0x00007fd54c06d268 (object 0x00000003f63c3d50, a org.apache.activemq.broker.jmx.ManagedTransportConnection),
  which is held by "ActiveMQ BrokerService[AMQ2] Task-38733"
"ActiveMQ BrokerService[AMQ2] Task-38733":
  waiting for ownable synchronizer 0x0000000436d5d458, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
  which is held by "MQTTInactivityMonitor Async Task: java.util.concurrent.ThreadPoolExecutor$Worker@7e51223f[State = -1, empty queue]"

Java stack information for the threads listed above:
===================================================
"MQTTInactivityMonitor Async Task: java.util.concurrent.ThreadPoolExecutor$Worker@7e51223f[State = -1, empty queue]":
	at org.apache.activemq.broker.TransportConnection.processRemoveConnection(TransportConnection.java:870)
	- waiting to lock <0x00000003f63c3d50> (a org.apache.activemq.broker.jmx.ManagedTransportConnection)
	at org.apache.activemq.command.RemoveInfo.visit(RemoveInfo.java:73)
	at org.apache.activemq.broker.TransportConnection.service(TransportConnection.java:326)
	at org.apache.activemq.broker.TransportConnection$1.onCommand(TransportConnection.java:190)
	at org.apache.activemq.transport.MutexTransport.onCommand(MutexTransport.java:45)
	at org.apache.activemq.transport.mqtt.MQTTInactivityMonitor.onCommand(MQTTInactivityMonitor.java:162)
	at org.apache.activemq.transport.mqtt.MQTTTransportFilter.sendToActiveMQ(MQTTTransportFilter.java:106)
	at org.apache.activemq.transport.mqtt.MQTTProtocolConverter.sendToActiveMQ(MQTTProtocolConverter.java:181)
	at org.apache.activemq.transport.mqtt.MQTTProtocolConverter.onTransportError(MQTTProtocolConverter.java:650)
	at org.apache.activemq.transport.mqtt.MQTTInactivityMonitor.onException(MQTTInactivityMonitor.java:194)
	at org.apache.activemq.transport.mqtt.MQTTInactivityMonitor$2$1.run(MQTTInactivityMonitor.java:128)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
"ActiveMQ BrokerService[AMQ2] Task-38733":
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x0000000436d5d458> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
	at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
	at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
	at org.apache.activemq.transport.MutexTransport.onCommand(MutexTransport.java:43)
	at org.apache.activemq.transport.mqtt.MQTTInactivityMonitor.onCommand(MQTTInactivityMonitor.java:162)
	at org.apache.activemq.transport.mqtt.MQTTTransportFilter.sendToActiveMQ(MQTTTransportFilter.java:106)
	at org.apache.activemq.transport.mqtt.MQTTProtocolConverter.sendToActiveMQ(MQTTProtocolConverter.java:181)
	at org.apache.activemq.transport.mqtt.MQTTProtocolConverter.onTransportError(MQTTProtocolConverter.java:650)
	at org.apache.activemq.transport.mqtt.MQTTTransportFilter.onException(MQTTTransportFilter.java:206)
	at org.apache.activemq.transport.TransportSupport.onException(TransportSupport.java:96)
	at org.apache.activemq.transport.nio.NIOSSLTransport.serviceRead(NIOSSLTransport.java:225)
	at org.apache.activemq.transport.mqtt.MQTTNIOSSLTransport.initializeStreams(MQTTNIOSSLTransport.java:48)
	at org.apache.activemq.transport.tcp.TcpTransport.connect(TcpTransport.java:519)
	at org.apache.activemq.transport.nio.NIOTransport.doStart(NIOTransport.java:160)
	at org.apache.activemq.transport.nio.NIOSSLTransport.doStart(NIOSSLTransport.java:412)
	at org.apache.activemq.util.ServiceSupport.start(ServiceSupport.java:55)
	at org.apache.activemq.transport.TransportFilter.start(TransportFilter.java:58)
	at org.apache.activemq.transport.mqtt.MQTTTransportFilter.start(MQTTTransportFilter.java:157)
	at org.apache.activemq.transport.mqtt.MQTTInactivityMonitor.start(MQTTInactivityMonitor.java:148)
	at org.apache.activemq.transport.TransportFilter.start(TransportFilter.java:58)
	at org.apache.activemq.broker.TransportConnection.start(TransportConnection.java:1066)
	- locked <0x00000003f63c3d50> (a org.apache.activemq.broker.jmx.ManagedTransportConnection)
	at org.apache.activemq.broker.TransportConnector$1$1.run(TransportConnector.java:218)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)