Found one Java-level deadlock:
=============================
"pool-1-thread-3":
  waiting to lock monitor 0x0000000000d12970 (object 0x0000000784a00fc0, a org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer),
  which is held by "Thread-2"
"Thread-2":
  waiting for ownable synchronizer 0x0000000784a4ac68, (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync),
  which is held by "pool-1-thread-3"

Java stack information for the threads listed above:
===================================================
"pool-1-thread-3":
        at org.jenkinsci.remoting.protocol.FilterLayer.onRecvRemoved(FilterLayer.java:134)
        - waiting to lock <0x0000000784a00fc0> (a org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.getNextRecv(ProtocolStack.java:929)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.onRecv(ProtocolStack.java:663)
        at org.jenkinsci.remoting.protocol.impl.SSLEngineFilterLayer.processRead(SSLEngineFilterLayer.java:369)
        at org.jenkinsci.remoting.protocol.impl.SSLEngineFilterLayer.onRecv(SSLEngineFilterLayer.java:117)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.onRecv(ProtocolStack.java:669)
        at org.jenkinsci.remoting.protocol.NetworkLayer.onRead(NetworkLayer.java:136)
        at org.jenkinsci.remoting.protocol.impl.BIONetworkLayer.access$2200(BIONetworkLayer.java:48)
        at org.jenkinsci.remoting.protocol.impl.BIONetworkLayer$Reader.run(BIONetworkLayer.java:283)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at hudson.remoting.Engine$1.lambda$newThread$0(Engine.java:93)
        at hudson.remoting.Engine$1$$Lambda$5/613009671.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
"Thread-2":
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x0000000784a4ac68> (a java.util.concurrent.locks.ReentrantReadWriteLock$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.doAcquireShared(AbstractQueuedSynchronizer.java:967)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1283)
        at java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:727)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.remove(ProtocolStack.java:755)
        at org.jenkinsci.remoting.protocol.FilterLayer.completed(FilterLayer.java:108)
        - locked <0x0000000784a00fc0> (a org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer)
        at org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer.complete(ConnectionHeadersFilterLayer.java:363)
        at org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer.doSend(ConnectionHeadersFilterLayer.java:499)
        - locked <0x0000000784a00fc0> (a org.jenkinsci.remoting.protocol.impl.ConnectionHeadersFilterLayer)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Ptr.doSend(ProtocolStack.java:692)
        at org.jenkinsci.remoting.protocol.ApplicationLayer.write(ApplicationLayer.java:157)
        at org.jenkinsci.remoting.protocol.impl.ChannelApplicationLayer.start(ChannelApplicationLayer.java:230)
        at org.jenkinsci.remoting.protocol.ProtocolStack.init(ProtocolStack.java:201)
        at org.jenkinsci.remoting.protocol.ProtocolStack.access$700(ProtocolStack.java:106)
        at org.jenkinsci.remoting.protocol.ProtocolStack$Builder.build(ProtocolStack.java:554)
        at org.jenkinsci.remoting.engine.JnlpProtocol4Handler.connect(JnlpProtocol4Handler.java:179)
        at org.jenkinsci.remoting.engine.JnlpProtocolHandler.connect(JnlpProtocolHandler.java:157)
        at hudson.remoting.Engine.innerRun(Engine.java:573)
        at hudson.remoting.Engine.run(Engine.java:474)

Found 1 deadlock.