EAP 7 performance issues with StuckThreadDetectionHandler enabled

Issue

• We enabled the StuckThreadDetectionHandler and started seeing degraded performance and increased CPU. Thread dumps show blocks like so:

"default I/O-5" #111 prio=5 os_prio=0 tid=0x0000000004cb5000 nid=0x1156 waiting for monitor entry [0x00007f92bf195000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at io.undertow.server.handlers.StuckThreadDetectionHandler$1.run(StuckThreadDetectionHandler.java:102)
    - waiting to lock <0x000000074fb03710> (a io.undertow.server.handlers.StuckThreadDetectionHandler)
    at org.xnio.nio.WorkerThread.safeRun(WorkerThread.java:612)
    at org.xnio.nio.WorkerThread.run(WorkerThread.java:479)