PH41078: ISSUE IN CONTROL REGION WITH HANDLING CONNECTION WITH ASYNC WRITE OUTSTANDING

APAR status

• Closed as program error.

Error description

• There is a problem in the code in the management of the Flag
  that indicates an Async Write is outstanding.  This could cause
  an abend0C4 by allowing a Connection with an outstanding Async
  Write request to close and cleanup it's resources before the
  Async Write is completed.   The abend0C4 would occur when the
  Async Write drives its completed method on the cleaned up
  Connection.
  
  The control region joblog could show a GPF in JIT compiled
  method:
  com/ibm/ws/tcp/channel/impl/ZAioTCPChannel.writeCompleted(Lcom/
  ibm/ws/tcp/channel/impl/ZAioTCPConnLink
  
  with native traceback:
  ZAioTCPChannelCppUtilities::writeComplete
  CF_TCP_Request::sendComplete
  CF_TCP_Connection_Object_Manager::processAsyncSendComplete
  ACR_ExecutionThread::RemoveAndProcessWork
  ACR_ExecutionRoutine
  

Local fix

• Setting this JVM generic argument in the CR may stop the abend
  from happening:
  -Xjit:exclude={com/ibm/ws/tcp/channel/impl/ZAioTCPChannel.write
  Completed(*}
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server                                      *
  *                  on z/OS                                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: WebSphere Application Server for z/OS   *
  *                      ZAioTCPChannel.writeCompleted received  *
  *                      an ABENDS0C4                            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  During the processing of a request received over a channel chain
  with the ZAioTCPConnLink and XMemProxyCRInboundConnLink an
  asynchronous write request received an ABEND0C4 on the
  WriteComplete method calling from native code up to java.   The
  connection objects, which include the two ConnLink objects
  mentioned previously, have been released.  The cause of the
  ABEND
  0C4 is that these Connection objects were cleaned up and
  released
  while an outstanding asynchronous write was still pending
  completion.
  The state of asynchronous reads and writes are maintained in the
  java objects associated with the connection.  A path was found
  in
  the processing of a write request that would erroneously reset
  the outstanding request flag, thus allowing the connection to
  cleanup without taking the necessary actions required for an
  outstanding request.
  

Problem conclusion

• Code has been modified to not reset the write outstanding flag o
  an error path through the ZAioTCPWriteRequestContextImpl.
  
  The fix for this APAR is targeted for inclusion in fix pack
  8.5.5.21 and 9.0.5.11. For more information, see 'Recommended
  Updates for WebSphere Application Server':
  https://www.ibm.com/support/pages/node/715553
  

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 FOR Z

• Fixed component ID

  5655I3500

Applicable component levels