PH01768: DEADLOCK POTENTIAL EXISTS WITH ORM XML PROCESSING FOR OPENJPA

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
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
8.5.5.16: WebSphere Application Server V8.5.5 Fix Pack 16
8.5.5.21: WebSphere Application Server V8.5.5.21

APAR status

• Closed as program error.

Error description

• There exists the potential for deadlock with the ORM XML
  processing function in an environment with multiple threads.
  Xerces calls Thread.currentThread().getContextClassloader()
  during its execution to construct the SAXParser (via
  ObjectFactory.createObject()). This means that within the call
  to Xerces, a ClassLoader lock will be attempted on the
  Thread's ContextClassLoader. If there is already a lock with a
  ClassLoader higher in the heirarchy, and another thread with a
  lock on the same ContextClassLoader that is waiting to acquire
  a lock on a higher level ClassLoader, then a deadlock will
  occur. This issue was revealed in a Liberty build break:
  RTC238000, but we maintain common code with tWAS.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server - Java Persistence APA -             *
  *                  JPA 2.0 & OpenJPA                           *
  ****************************************************************
  * PROBLEM DESCRIPTION: There exists the potential for          *
  *                      deadlock with the ORM XMLprocessing     *
  *                      function in an environment with         *
  *                      multiple threads.                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  There exists the potential for deadlock with the ORM
  XMLprocessing function in an environment with multiple threads.
  Xerces calls Thread.currentThread().getContextClassloader()
  during its execution to construct the SAXParser (via
  ObjectFactory.createObject()). This means that within the call
  to Xerces, a ClassLoader lock will be attempted on the
  Thread's ContextClassLoader. If there is already a lock with a
  ClassLoader higher in the heirarchy, and another thread with a
  lock on the same ContextClassLoader that is waiting to acquire
  a lock on a higher level ClassLoader, then a deadlock will
  occur.
  Exception:
  00000036 SystemOut    O | DEADLOCK DETECTED BY THE JVM, thread
  details:
  00000036 SystemOut    O LargeThreadPool-thread-23 64 BLOCKED
  java.lang.ClassLoader.loadClass(ClassLoader.java:763)
  com.ibm.ws.classloading.internal.UnifiedClassLoader.loadClass0(U
  nifiedClassLoader.java:108)
  com.ibm.ws.classloading.internal.UnifiedClassLoader$Delegation.l
  oadClass(UnifiedClassLoader.java:79)
  com.ibm.ws.classloading.internal.UnifiedClassLoader.loadClass(Un
  ifiedClassLoader.java:103)
  com.ibm.ws.classloading.internal.ThreadContextClassLoader.loadCl
  ass(ThreadContextClassLoader.java:112)
  java.lang.ClassLoader.loadClass(ClassLoader.java:741)
  

Problem conclusion

• The fix for this APAR changes the OpenJPA implementation
  and involves an update to the thirdparty source. See
  https://issues.apache.org/jira/browse/OPENJPA-1993
  
  This fix is currently targeted for WebSphere Application
  Server 9.0.0.10, 8.5.5.15, and WebSphere Liberty 18.0.0.3.
  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

  WEBSPHERE APP S

• Fixed component ID

  5724J0800

Applicable component levels

• R850 PSY

     UP

• R900 PSY

     UP