NullPointerException/IllegalArgumentException can happen at channel.write(buffer) because of a race condition inside AsyncSenderImpl in JBoss EAP 7

Issue

The following NullPointerException or IllegalArgumentException happened. This happened very raraly. What caused this issue?

ERROR [org.xnio.listener] (default I/O-3) XNIO001007: A channel event listener threw an exception: java.lang.NullPointerException
    at org.xnio.conduits.ConduitStreamSinkChannel.write(ConduitStreamSinkChannel.java:154) [xnio-api-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]
    at io.undertow.channels.DetachableStreamSinkChannel.write(DetachableStreamSinkChannel.java:187)
    at io.undertow.server.HttpServerExchange$WriteDispatchChannel.write(HttpServerExchange.java:2011)
    at io.undertow.io.AsyncSenderImpl.invokeOnComplete(AsyncSenderImpl.java:398)
    at io.undertow.io.AsyncSenderImpl.access$400(AsyncSenderImpl.java:41)
    at io.undertow.io.AsyncSenderImpl$3.handleEvent(AsyncSenderImpl.java:454)
    at io.undertow.io.AsyncSenderImpl$3.handleEvent(AsyncSenderImpl.java:440)
    at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) [xnio-api-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]
    at io.undertow.channels.DetachableStreamSinkChannel$SetterDelegatingListener.handleEvent(DetachableStreamSinkChannel.java:285)
    at io.undertow.channels.DetachableStreamSinkChannel$SetterDelegatingListener.handleEvent(DetachableStreamSinkChannel.java:272)
    at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) [xnio-api-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]
    at org.xnio.conduits.WriteReadyHandler$ChannelListenerHandler.writeReady(WriteReadyHandler.java:65) [xnio-api-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]
    at io.undertow.server.protocol.ajp.AjpServerResponseConduit$AjpServerWriteReadyHandler.writeReady(AjpServerResponseConduit.java:496)
    at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:94) [xnio-nio-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]
    at org.xnio.nio.WorkerThread.run(WorkerThread.java:571) [xnio-nio-3.4.7.Final-redhat-1.jar:3.4.7.Final-redhat-1]

or

ERROR [stderr] (default task-4) Exception in thread "default task-44" java.lang.NullPointerException
ERROR [stderr] (default task-4)    at org.xnio.conduits.ConduitStreamSinkChannel.write(ConduitStreamSinkChannel.java:154)
ERROR [stderr] (default task-4)    at io.undertow.channels.DetachableStreamSinkChannel.write(DetachableStreamSinkChannel.java:187)
ERROR [stderr] (default task-4)    at io.undertow.server.HttpServerExchange$WriteDispatchChannel.write(HttpServerExchange.java:2011)
ERROR [stderr] (default task-4)    at io.undertow.io.AsyncSenderImpl.invokeOnComplete(AsyncSenderImpl.java:398)
ERROR [stderr] (default task-4)    at io.undertow.io.AsyncSenderImpl.send(AsyncSenderImpl.java:162)
ERROR [stderr] (default task-4)    at io.undertow.server.handlers.resource.PathResource$1ServerTask.run(PathResource.java:178)
ERROR [stderr] (default task-4)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
ERROR [stderr] (default task-4)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
ERROR [stderr] (default task-4)    at java.lang.Thread.run(Thread.java:748)

or

ERROR [stderr] (default task-13) Exception in thread "default task-13" java.lang.IllegalArgumentException
ERROR [stderr] (default task-13)    at java.nio.Buffer.position(Buffer.java:244)
ERROR [stderr] (default task-13)    at sun.nio.ch.IOUtil.write(IOUtil.java:158)
ERROR [stderr] (default task-13)    at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:504)
ERROR [stderr] (default task-13)    at org.xnio.nio.NioSocketConduit.write(NioSocketConduit.java:162)
ERROR [stderr] (default task-13)    at io.undertow.conduits.BytesSentStreamSinkConduit.write(BytesSentStreamSinkConduit.java:70)
ERROR [stderr] (default task-13)    at io.undertow.conduits.AbstractFramedStreamSinkConduit.doWrite(AbstractFramedStreamSinkConduit.java:140)
ERROR [stderr] (default task-13)    at io.undertow.conduits.AbstractFramedStreamSinkConduit.write(AbstractFramedStreamSinkConduit.java:108)
ERROR [stderr] (default task-13)    at io.undertow.server.protocol.ajp.AjpServerResponseConduit.write(AjpServerResponseConduit.java:298)
ERROR [stderr] (default task-13)    at io.undertow.server.protocol.ajp.AjpServerResponseConduit.write(AjpServerResponseConduit.java:357)
ERROR [stderr] (default task-13)    at org.xnio.conduits.ConduitStreamSinkChannel.write(ConduitStreamSinkChannel.java:154)
ERROR [stderr] (default task-13)    at io.undertow.channels.DetachableStreamSinkChannel.write(DetachableStreamSinkChannel.java:187)
ERROR [stderr] (default task-13)    at io.undertow.server.HttpServerExchange$WriteDispatchChannel.write(HttpServerExchange.java:2011)
ERROR [stderr] (default task-13)    at io.undertow.io.AsyncSenderImpl.invokeOnComplete(AsyncSenderImpl.java:398)
ERROR [stderr] (default task-13)    at io.undertow.io.AsyncSenderImpl.send(AsyncSenderImpl.java:162)
ERROR [stderr] (default task-13)    at io.undertow.server.handlers.resource.PathResource$1ServerTask.run(PathResource.java:178)
ERROR [stderr] (default task-13)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
ERROR [stderr] (default task-13)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
ERROR [stderr] (default task-13)    at java.lang.Thread.run(Thread.java:748)