PI92979: HIGH CPU DUE TO THE CLASSLOADER STACK

9.0.0.8: WebSphere Application Server traditional V9.0 Fix Pack 8
8.5.5.14: WebSphere Application Server V8.5.5 Fix Pack 14
9.0.0.9: WebSphere Application Server traditional V9.0 Fix Pack 9
9.0.0.10: WebSphere Application Server traditional V9.0 Fix Pack 10
8.5.5.15: WebSphere Application Server V8.5.5 Fix Pack 15
9.0.0.11: WebSphere Application Server traditional V9.0 Fix Pack 11
9.0.5.0: WebSphere Application Server traditional Version 9.0.5 Refresh Pack
9.0.5.1: WebSphere Application Server traditional Version 9.0.5 Fix Pack 1
9.0.5.2: WebSphere Application Server traditional Version 9.0.5 Fix Pack 2
8.5.5.17: WebSphere Application Server V8.5.5 Fix Pack 17
9.0.5.3: WebSphere Application Server traditional Version 9.0.5 Fix Pack 3
9.0.5.4: WebSphere Application Server traditional Version 9.0.5 Fix Pack 4
9.0.5.5: WebSphere Application Server traditional Version 9.0.5 Fix Pack 5
WebSphere Application Server traditional 9.0.5.6
9.0.5.7: WebSphere Application Server traditional Version 9.0.5 Fix Pack 7
9.0.5.8: WebSphere Application Server traditional Version 9.0.5.8
8.5.5.20: WebSphere Application Server V8.5.5.20
8.5.5.18: WebSphere Application Server V8.5.5 Fix Pack 18
8.5.5.19: WebSphere Application Server V8.5.5 Fix Pack 19
9.0.5.9: WebSphere Application Server traditional Version 9.0.5.9
9.0.5.10: WebSphere Application Server traditional Version 9.0.5.10
8.5.5.16: WebSphere Application Server V8.5.5 Fix Pack 16
8.5.5.21: WebSphere Application Server V8.5.5.21
9.0.5.11: WebSphere Application Server traditional Version 9.0.5.11

APAR status

• Closed as program error.

Error description

• gh CPU due to the classloader stack
  

Local fix

• na
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server Hang Detection.                      *
  ****************************************************************
  * PROBLEM DESCRIPTION: The application server may              *
  *                      exhibit high CPU utilization when       *
  *                      Hang Detection is enabled.              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The Thread Monitor may loop indefinitely while determining
  the state of a managed thread.  When this problem occurs you
  will find a log containing an FFDC event like that shown below,
  where the failure call stack indicates a
  ConcurrentModificationException occurred while determining a
  managed thread is clear (no longer hung.)  A similar
  exception may occur while determining a managed thread is hung.
  FFDC Exception:java.util.ConcurrentModificationException
  SourceId:com.ibm.ws.runtime.component.ThreadMonitorImpl
  ProbeId:439
  ...
  java.util.ConcurrentModificationException
  at
  java.util.Vector$Itr.checkForComodification(Vector.java:1195)
  at
  java.util.Vector$Itr.next(Vector.java:1148)
  at
  com.ibm.ws.runtime.component.ThreadMonitorImpl.threadIsClear(Thr
  eadMonitorImpl.java:676)
  at
  com.ibm.ws.runtime.component.ThreadPoolMgrImpl$ThreadPoolMonitor
  Adapter.clearThread(ThreadPoolMgrImpl.java:988)
  at
  com.ibm.ws.util.ThreadPool$Worker.disableHungThreadDetection(Thr
  eadPool.java:1968)
  at
  com.ibm.ws.util.ThreadPool$Worker.threadReturned(ThreadPool.java
  :1940)
  at
  com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1907)
  The problem may be circumvented by disabling Hang Detection on
  the failing application server. Hang Detection is disabled
  whenever custom property
  "com.ibm.websphere.threadmonitor.interval" is set to zero (0)
  in the application server configuration.  Instructions to
  disable Hang Detection are provided in topic "Configuring the
  hang detection policy" of the WebSphere Application Server
  v8.5.5 Knowledge Center:
  https://www.ibm.com/support/knowledgecenter/en/SSAW57_8.5.5/com.
  ibm.websphere.nd.doc/ae/ttrb_confighangdet.html
  

Problem conclusion

• Apply APAR PI92979 to ensure the Thread Monitor of an
  application server does enter an infinite loop while
  detecting hung threads.
  
  The fix for this APAR is currently targeted for inclusion in
  fix packs 8.5.5.14 and 9.0.0.8.  Please refer to
  the Recommended Updates page for delivery information:
  http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WEBS APP SERV N

• Fixed component ID

  5724H8800

Applicable component levels

• R850 PSY

     UP

• R900 PSY

     UP