Found one Java-level deadlock:
=============================
"undertow-worker task-129":
  waiting to lock monitor 0x00007f1e64096aa8 (object 0x00000006d7b200e8, a io.undertow.protocols.http2.Http2Channel),
  which is held by "undertow-worker I/O-7"
"undertow-worker I/O-7":
  waiting to lock monitor 0x00007f1e20039e38 (object 0x00000006d7b21670, a java.lang.Object),
  which is held by "undertow-worker task-129"

Java stack information for the threads listed above:
===================================================
"undertow-worker task-129":
        at io.undertow.server.protocol.framed.AbstractFramedChannel$1.freed(AbstractFramedChannel.java:146)
        - waiting to lock <0x00000006d7b200e8> (a io.undertow.protocols.http2.Http2Channel)
        at io.undertow.util.ReferenceCountedPooled.freeInternal(ReferenceCountedPooled.java:96)
        at io.undertow.util.ReferenceCountedPooled.access$000(ReferenceCountedPooled.java:37)
        at io.undertow.util.ReferenceCountedPooled$1.close(ReferenceCountedPooled.java:123)
        at io.undertow.server.protocol.framed.AbstractFramedStreamSourceChannel.beforeRead(AbstractFramedStreamSourceChannel.java:548)
        - locked <0x00000006d7b21670> (a java.lang.Object)
        at io.undertow.server.protocol.framed.AbstractFramedStreamSourceChannel.read(AbstractFramedStreamSourceChannel.java:502)
        at io.undertow.protocols.http2.Http2StreamSourceChannel.read(Http2StreamSourceChannel.java:147)
        at org.xnio.conduits.StreamSourceChannelWrappingConduit.read(StreamSourceChannelWrappingConduit.java:43)
        at org.xnio.conduits.ConduitStreamSourceChannel.read(ConduitStreamSourceChannel.java:127)
        at io.undertow.channels.DetachableStreamSourceChannel.read(DetachableStreamSourceChannel.java:209)
        at io.undertow.server.HttpServerExchange$ReadDispatchChannel.read(HttpServerExchange.java:2337)
        at org.xnio.channels.Channels.readBlocking(Channels.java:294)
        at io.undertow.servlet.spec.ServletInputStreamImpl.readIntoBuffer(ServletInputStreamImpl.java:192)
        at io.undertow.servlet.spec.ServletInputStreamImpl.read(ServletInputStreamImpl.java:168)
        at java.io.FilterInputStream.read(FilterInputStream.java:133)
        at java.io.PushbackInputStream.read(PushbackInputStream.java:186)
        at java.io.DataInputStream.read(DataInputStream.java:149)
        at com.google.common.io.ByteStreams$LimitedInputStream.read(ByteStreams.java:677)
        at com.google.protobuf.CodedInputStream$StreamDecoder.tryRefillBuffer(CodedInputStream.java:2814)
        at com.google.protobuf.CodedInputStream$StreamDecoder.isAtEnd(CodedInputStream.java:2737)
        at com.google.protobuf.CodedInputStream$StreamDecoder.readTag(CodedInputStream.java:2088)

...etc...

        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:706)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:791)
        at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
        at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
        at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:67)
        at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
        at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:132)
        at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
        at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
        at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
        at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
        at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
        at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
        at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
        at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
        at io.undertow.server.handlers.encoding.EncodingHandler.handleRequest(EncodingHandler.java:72)
        at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
        at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
        at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
        at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
        at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
        at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
        at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
        at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
        at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
        at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
        at io.undertow.server.Connectors.executeRootHandler(Connectors.java:360)
        at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
"undertow-worker I/O-7":
        at io.undertow.server.protocol.framed.AbstractFramedStreamSourceChannel.dataReady(AbstractFramedStreamSourceChannel.java:379)
        - waiting to lock <0x00000006d7b21670> (a java.lang.Object)
        at io.undertow.server.protocol.framed.AbstractFramedChannel.receive(AbstractFramedChannel.java:393)
        - locked <0x00000006d7b200e8> (a io.undertow.protocols.http2.Http2Channel)
        at io.undertow.server.protocol.http2.Http2ReceiveListener.handleEvent(Http2ReceiveListener.java:111)
        at io.undertow.server.protocol.http2.Http2ReceiveListener.handleEvent(Http2ReceiveListener.java:60)
        at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92)
        at io.undertow.server.protocol.framed.AbstractFramedChannel$FrameReadListener.handleEvent(AbstractFramedChannel.java:942)
        at io.undertow.server.protocol.framed.AbstractFramedChannel$FrameReadListener.handleEvent(AbstractFramedChannel.java:923)
        at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92)
        at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66)
        at io.undertow.protocols.ssl.SslConduit$SslReadReadyHandler.readReady(SslConduit.java:1161)
        at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:89)
        at org.xnio.nio.WorkerThread.run(WorkerThread.java:591)

Found 1 deadlock.