EAP failed to start up because 2 threads were instantiating Xnio instance at exactly the same time.

~~~
09:23:08,823 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-10) MSC000001: Failed to start service jboss.remoting.endpoint.subsystem: org.jboss.msc.service.StartException in service jboss.remoting.endpoint.subsystem: Failed to start service
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1767) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_75]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_75]
	at java.lang.Thread.run(Thread.java:745) [rt.jar:1.7.0_75]
Caused by: java.util.ServiceConfigurationError: org.xnio.XnioProvider: Provider org.xnio.nio.NioXnioProvider could not be instantiated
	at java.util.ServiceLoader.fail(ServiceLoader.java:224) [rt.jar:1.7.0_75]
	at java.util.ServiceLoader.access$100(ServiceLoader.java:181) [rt.jar:1.7.0_75]
	at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:377) [rt.jar:1.7.0_75]
	at java.util.ServiceLoader$1.next(ServiceLoader.java:445) [rt.jar:1.7.0_75]
	at org.xnio.Xnio.doGetInstance(Xnio.java:187) [xnio-api-3.0.10.GA-redhat-1.jar:3.0.10.GA-redhat-1]
	at org.xnio.Xnio.getInstance(Xnio.java:146) [xnio-api-3.0.10.GA-redhat-1.jar:3.0.10.GA-redhat-1]
	at org.jboss.remoting3.Remoting.createEndpoint(Remoting.java:73) [jboss-remoting-3.2.19.GA-redhat-1.jar:3.2.19.GA-redhat-1]
	at org.jboss.as.remoting.EndpointService.start(EndpointService.java:71) [jboss-as-remoting-7.3.4.Final-redhat-1.jar:7.3.4.Final-redhat-1]
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
	... 3 more
Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.xnio.nio.NioXnioProvider
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) [rt.jar:1.7.0_75]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) [rt.jar:1.7.0_75]
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) [rt.jar:1.7.0_75]
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526) [rt.jar:1.7.0_75]
	at java.lang.Class.newInstance(Class.java:379) [rt.jar:1.7.0_75]
	at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:373) [rt.jar:1.7.0_75]
	... 10 more

09:23:08,823 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-3) MSC000001: Failed to start service jboss.remoting.endpoint.management: org.jboss.msc.service.StartException in service jboss.remoting.endpoint.management: Failed to start service
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1767) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_75]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_75]
        at java.lang.Thread.run(Thread.java:745) [rt.jar:1.7.0_75]
Caused by: java.util.ServiceConfigurationError: org.xnio.XnioProvider: Provider org.xnio.nio.NioXnioProvider could not be instantiated
        at java.util.ServiceLoader.fail(ServiceLoader.java:224) [rt.jar:1.7.0_75]
        at java.util.ServiceLoader.access$100(ServiceLoader.java:181) [rt.jar:1.7.0_75]
        at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:377) [rt.jar:1.7.0_75]
        at java.util.ServiceLoader$1.next(ServiceLoader.java:445) [rt.jar:1.7.0_75]
        at org.xnio.Xnio.doGetInstance(Xnio.java:187)
        at org.xnio.Xnio.getInstance(Xnio.java:146)
        at org.jboss.remoting3.Remoting.createEndpoint(Remoting.java:73)
        at org.jboss.as.remoting.EndpointService.start(EndpointService.java:71)
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.4.GA-redhat-1.jar:1.0.4.GA-redhat-1]
        ... 3 more
Caused by: java.lang.ExceptionInInitializerError
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) [rt.jar:1.7.0_75]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) [rt.jar:1.7.0_75]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) [rt.jar:1.7.0_75]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526) [rt.jar:1.7.0_75]
        at java.lang.Class.newInstance(Class.java:379) [rt.jar:1.7.0_75]
        at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:373) [rt.jar:1.7.0_75]
        ... 10 more
Caused by: java.lang.IllegalStateException: No functional selector provider is available
        at org.xnio.nio.NioXnio$2.run(NioXnio.java:158)
        at org.xnio.nio.NioXnio$2.run(NioXnio.java:81)
        at java.security.AccessController.doPrivileged(Native Method) [rt.jar:1.7.0_75]
        at org.xnio.nio.NioXnio.<init>(NioXnio.java:80)
        at org.xnio.nio.NioXnioProvider.<clinit>(NioXnioProvider.java:34)
        ... 16 more
~~~

This happened only once in a customer's environment. EAP version is 6.2.4 (Xnio 3.0.10.GA-redhat-1).

It seems synchronizing "org.xnio.Xnio.doGetInstance()" can be a workaround. The current Xnio 3.x branch is still not synchronized. Or a proper service dependency can be defined in the container side.