A dead log when one thread performed transient actions update, while second thread loaded transient actions (thread dump of these two threads is bellow).
Proposed patch which could solve the issue is attached.

"Handling GET /hudson/view/EAP5-HornetQ/job/hornetq-test-eap5-platforms/test/trend : http-0.0.0.0-8585-30" Id=37903 BLOCKED on java.util.Vector@285c638f owned by "Handling POST /hudson/view/EAP5-HornetQ/job/hornetq-test-eap5-platforms/configSubmit : http-0.0.0.0-8585-91" Id=46315
at java.util.Vector.toArray(Vector.java:643)

• blocked on java.util.Vector@285c638f
  at java.util.Vector.addAll(Vector.java:830)
• locked java.util.Vector@498c55fc
  at hudson.model.AbstractProject.getActions(AbstractProject.java:841)
• locked hudson.matrix.MatrixProject@41de3998
  at hudson.model.Job.getPermalinks(Job.java:839)
  at hudson.model.Job.getDynamic(Job.java:711)
  at hudson.matrix.MatrixProject.getDynamic(MatrixProject.java:610)
  at sun.reflect.GeneratedMethodAccessor391.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:185)
  at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
  at org.kohsuke.stapler.MetaClass$12.dispatch(MetaClass.java:316)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
  at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
  at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
  at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:35)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
  at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:113)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
  at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
  at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
  at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
  at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
  at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
  at java.lang.Thread.run(Thread.java:619)

Handling POST /hudson/view/EAP5-HornetQ/job/hornetq-test-eap5-platforms/configSubmit : http-0.0.0.0-8585-91

"Handling POST /hudson/view/EAP5-HornetQ/job/hornetq-test-eap5-platforms/configSubmit : http-0.0.0.0-8585-91" Id=46315 BLOCKED on hudson.matrix.MatrixProject@41de3998 owned by "Handling GET /hudson/view/EAP5-HornetQ/job/hornetq-test-eap5-platforms/test/trend : http-0.0.0.0-8585-30" Id=37903
at hudson.model.AbstractProject.getActions(AbstractProject.java:840)

• blocked on hudson.matrix.MatrixProject@41de3998
  at hudson.model.Actionable.getActions(Actionable.java:75)
  at hudson.plugins.jobConfigHistory.JobConfigHistoryActionFactory.createFor(JobConfigHistoryActionFactory.java:30)
  at hudson.model.AbstractProject.updateTransientActions(AbstractProject.java:494)
• locked java.util.Vector@285c638f
  at hudson.matrix.MatrixProject.updateTransientActions(MatrixProject.java:268)
• locked java.util.Vector@285c638f
  at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:527)
  at sun.reflect.GeneratedMethodAccessor2018.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:185)
  at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
  at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:54)
  at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:74)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:180)
  at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:519)
  at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
  at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
  at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
  at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:35)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
  at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:113)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
  at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
  at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
  at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
  at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
  at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
  at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
  at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
  at java.lang.Thread.run(Thread.java:619)