In order to apply this update to the 1.5 branch, I've broken this issue off from
it's original home in ICE-992.

The problem typically only occurs under heavy load but can be generated
synthetically by putting a long (20 sec) sleep in the correct location of the
PersistentFacesServlet.

A live thread dump + stack trace showing the deadlock from a clustered JBoss
instance (jboss2) running the ICEfaces.org site.

Found one Java-level deadlock:
=============================
"TP-Processor2326":
  waiting to lock monitor 0x089e5c34 (object 0x3565e8d8, a java.lang.String),
  which is held by "TP-Processor2603"
"TP-Processor2603":
  waiting to lock monitor 0x0839bd14 (object 0x332218e0, a
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager),
  which is held by "TP-Processor2326"

Java stack information for the threads listed above:
===================================================
"TP-Processor2326":
        at
com.icesoft.faces.webapp.xmlhttp.BlockingResponseState.<init>(BlockingResponseState.java:84)
        - waiting to lock <0x3565e8d8> (a java.lang.String)
        at
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager.createState(ResponseStateManager.java:120)
        at
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager.getState(ResponseStateManager.java:136)
        - locked <0x332218e0> (a
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager)
        at
com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:175)
        - locked <0x332f66a8> (a com.icesoft.faces.webapp.xmlhttp.BlockingServlet)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
        at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
        at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at
org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
        at
org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
        at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:199)
        at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:282)
        at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:754)
        at
org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:684)
        at
org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:876)
        at
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
        at java.lang.Thread.run(Thread.java:595)
"TP-Processor2603":
        at
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager.getState(ResponseStateManager.java:131)
        - waiting to lock <0x332218e0> (a
com.icesoft.faces.webapp.xmlhttp.ResponseStateManager)
        at
com.icesoft.faces.webapp.xmlhttp.PersistentFacesServlet.service(PersistentFacesServlet.java:402)
        - locked <0x3565e8d8> (a java.lang.String)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
        at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
        at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at
org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
        at
org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
        at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:199)
        at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:282)
        at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:754)
        at
org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:684)
        at
org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:876)
        at
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
        at java.lang.Thread.run(Thread.java:595)

Found 1 deadlock.