High CPU in XNIO accept thread

Environment

• JBoss Enterprise Application Platform (EAP) 7.0.x

Issue

• We see high CPU in EAP 7's XNIO accept threads:

"default Accept" #125 prio=5 os_prio=0 tid=0x00007fc6e81ee000 nid=0xbcea runnable [0x00007fc6ed7d8000]
   java.lang.Thread.State: RUNNABLE
	at java.lang.Throwable.fillInStackTrace(Native Method)
	at java.lang.Throwable.fillInStackTrace(Throwable.java:783)
	- locked <0x00000007170b0b00> (a java.io.IOException)
	at java.lang.Throwable.(Throwable.java:265)
	at java.lang.Exception.(Exception.java:66)
	at java.io.IOException.(IOException.java:58)
	at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method)
	at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:422)
	at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:250)
	- locked <0x00000005c222d048> (a java.lang.Object)
	at org.xnio.nio.QueuedNioTcpServer.handleReady(QueuedNioTcpServer.java:466)
	at org.xnio.nio.QueuedNioTcpServerHandle.handleReady(QueuedNioTcpServerHandle.java:38)
	at org.xnio.nio.WorkerThread.run(WorkerThread.java:567)

Resolution

• Upgrade to EAP 7.0.6+

Root Cause

• Content from issues.jboss.org is not included.XNIO-279
• Exceptions raised during the accept call were not properly handled, leading to high CPU loops

Diagnostic Steps

• Check thread dumps and logs for exceptions raised from the accept threads

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