Fix (APAR): PI76509 Status: Fix Release: 16.0.0.4 Operating System: AIX,HP-UX,IBM i,Inspur K-UX,Linux,OS X,Solaris,Windows,iOS,z/OS Supersedes Fixes: CMVC Defect: xxxxxx Byte size of APAR: 1669148 Date: 2017-04-25 Abstract: Hang on org/apache/webbeans/context/sessioncontext.addchildrequest Description/symptom of problem: PI76509 resolves the following problem: ERROR DESCRIPTION: Hanging threads after applying fix pack 8.5.5.11 or liberty 16.0.0.4 or 17.0.0.1 SystemOut.log and Java cores show: [9-2-17 16:13:45:421 CET] 0000002f ThreadMonitor W WSVR0605W: Thread "WebContainer : 35" (0000011d) has been active for 697463 milliseconds and may be hung. There is/are 1 thread(s) in total in the server that may be hung. at java/util/HashMap.put(HashMap.java:506(Compiled Code)) at java/util/HashSet.add(HashSet.java:229(Compiled Code)) at org/apache/webbeans/context/SessionContext.addChildRequest(Sessi onContext.java:118(Compiled Code)) at org/apache/webbeans/web/context/WebContextsService.initRequestCo ntext(WebContextsService.java:550(Compiled Code)) at org/apache/webbeans/web/context/WebContextsService.startContext( WebContextsService.java:417(Compiled Code)) at com/ibm/ws/webbeans/services/JCDIWebListener.requestInitialized( JCDIWebListener.java:321(Compiled Code)) at com/ibm/ws/webcontainer/webapp/WebApp.notifyServletRequestCreate d(WebApp.java:1908(Compiled Code)) Additional symptoms: session invalidation threads begin to become blocked and an error similar to the following is logged in javacores Webcontainers 38,23,20,18 and 7 were blocked behind webcontainer 21 which was runnable and Owns Monitor Lock on com/ibm/ws/session/store/memory/MemorySession@0x000000000852C740 at java/util/HashMap$HashIterator.remove(HashMap.java:955(Compiled Code)) at org/apache/webbeans/context/SessionContext.isAnyRequestActive(Se ssionContext.java:137(Compiled Code)) at org/apache/webbeans/context/SessionContext.isAnyRequestActive(Se ssionContext.java:123(Compiled Code)) at org/apache/webbeans/web/context/WebContextsService.destroySessio nContext(WebContextsService.java:717(Compiled Code)) at org/apache/webbeans/web/context/WebContextsService.endContext(We bContextsService.java:269(Compiled Code)) at com/ibm/ws/webbeans/services/JCDIWebListener.sessionDestroyed(JC DIWebListener.java:397(Compiled Code)) at com/ibm/ws/session/http/HttpSessionObserver.sessionDestroyed(Htt pSessionObserver.java:180(Compiled Code)) at com/ibm/ws/session/SessionEventDispatcher.sessionDestroyed(Sessi onEventDispatcher.java:160(Compiled Code)) at com/ibm/ws/session/StoreCallback.sessionInvalidated(StoreCallbac k.java:126(Compiled Code)) at com/ibm/ws/session/store/memory/MemorySession.invalidate(MemoryS ession.java:232) at com/ibm/ws/session/store/memory/MemorySession.invalidate(MemoryS ession.java:878) LOCAL FIX: None PROBLEM SUMMARY USERS AFFECTED: All users of IBM WebSphere Application Server PROBLEM DESCRIPTION: Concurrent modification can corrupt a HashSet leading to hanging threads RECOMMENDATION: None A HashSet in the org.apache.webbeans.context.SessionContext was undergoing concurrent modification. A hanging thread with SessionContext on the stack is likely to be resolved by this APAR. PROBLEM CONCLUSION: The Set in question was updated to use a different Set implementation that can accept concurrent modification. The fix for this APAR is currently targeted for inclusion in fix packs 8.5.5.12, 8.0.0.14 and Liberty 17.0.0.2. Please refer to the Recommended Updates page for delivery information: http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980 Directions to apply fix: Install Fix to all WebSphere installations unless special instructions are included below. Special Instructions: None NOTE: The user must: * Logged in with the same authority level when unpacking a fix, fix pack or refresh pack. * Be at V1.8.5 or newer of the Installation Manager. Certain iFixes may require a newer version of the Installation Manager and the Installation Manager will inform you during the installation process if a newer version is required. The IBM Information Center can provide details, if needed, on the use of the Installation Manager to apply the iFixes. http://www.ibm.com/support/knowledgecenter/SSDV2W_1.8.5/com.ibm.cic.agent.ui.doc/helpindex_imic.html. Shutdown WebSphere Application Server before applying the iFixes. Restart WebSphere Application Server after applying the iFixes. Directions to remove fix: The IBM Information Center can provide details, if needed, on the use of the Installation Manager to remove the iFixes. http://www.ibm.com/support/knowledgecenter/SSDV2W_1.8.5/com.ibm.cic.agent.ui.doc/helpindex_imic.html. Shutdown WebSphere Application Server before removing the iFixes. Restart WebSphere Application Server after removing the iFixes. Directions to re-apply fix: 1) Shutdown WebSphere Application Server. 2) Follow the Fix instructions to apply the fix. 3) Restart WebSphere Application Server. Additional Information: