Concurrent access to WeakHashMap in ConcurrentCache causes infinite loop and 100% CPU in JBoss

Issue

• High CPU usage with threads stuck in java.util.WeakHashMap.put() and java.util.WeakHashMap.get(). For example:

  "ajp-146.215.106.42-8009-38" daemon prio=10 tid=0x00002aab6425d800 nid=0x135b runnable [0x0000000048c14000]
  java.lang.Thread.State: RUNNABLE
      at java.util.WeakHashMap.get(WeakHashMap.java:355)
      at org.apache.el.util.ConcurrentCache.get(ConcurrentCache.java:24)
      at org.apache.el.lang.ExpressionBuilder.createNodeInternal(ExpressionBuilder.java:90)
  
  "ajp-146.215.106.42-8009-18" daemon prio=10 tid=0x00002aab643ea000 nid=0x538d runnable [0x00000000458fd000]
  java.lang.Thread.State: RUNNABLE
      at java.util.WeakHashMap.put(WeakHashMap.java:405)
      at java.util.WeakHashMap.putAll(WeakHashMap.java:518)
  

• We are facing HIGH CPU utilization in one of the Application server nodes in production environment. We currently have two application server nodes running on jboss-eap-5.1. However we are seeing High CPU usage on only one node.