IC64483: ASYNCHRONOUS JMS CONSUMER HANGS WHEN STOPPING A CONNECTION WHEN AN EXCEPTION IS DELIVERED TO THE EXCEPTIONLISTENER

WebSphere MQ V7.0 Fix Pack 7.0.1.2
WebSphere MQ V7.0.1 for i5/OS Fix Pack 7.0.1.2

APAR status

• Closed as program error.

Error description

• A WebSphere MQ asynchronous Java Message Service (JMS) Message
  consumer using WebSphere MQ (WMQ) v7 client jars and connecting
  to a WebSphere MQ v6 queue manager hangs when it attempts to
  close a connection object using connection.close() if there was
  an exception delivered to ExceptionListener registered with the
  connection.
  
  .
  The following exception stack trace can be seen in the java
  cores indicating a hang in the waitForPaused method:
  .
  4XESTACKTRACE    at java/lang/Object.wait(Native Method)
  4XESTACKTRACE    at java/lang/Object.wait(Bytecode PC:3
  (Compiled Code))
  4XESTACKTRACE    at com/ibm/msg/client/wmq/v6/jms/internal/
  SessionAsyncHelper.waitForPaused
  (Bytecode PC:32)
  4XESTACKTRACE    at com/ibm/msg/client/wmq/v6/jms/internal/
  MQSession.stop(Bytecode PC:91)
  4XESTACKTRACE    at com/ibm/msg/client/jms/internal/JmsSession
  Impl.stop(Bytecode PC:256)
  4XESTACKTRACE    at com/ibm/msg/client/jms/internal/JmsSession
  Impl.stop(Bytecode PC:16)
  4XESTACKTRACE    at
  com/ibm/msg/client/jms/internal/JmsConnection
  Impl.stop(Bytecode PC:80)
  4XESTACKTRACE    at com/ibm/mq/jms/MQConnection.stop(Bytecode
  PC:20)
  4XESTACKTRACE    at com/ibm/micro/internal/bridge/connection/
  jms/common/JMSBridgeConnection.disconnect
  (Bytecode PC:43)
  4XESTACKTRACE    at com/ibm/micro/internal/bridge/connection/
  jms/common/JMSBridgeConnection.shutdown
  (Bytecode PC:46)
  4XESTACKTRACE    at com/ibm/micro/internal/bridge/Pipe.shutdown
  Receive(Bytecode PC:64)
  4XESTACKTRACE    at com/ibm/mqttdirect/core/Dispatcher.dispatch
  (Bytecode PC:329(Compiled Code))
  4XESTACKTRACE    at com/ibm/mqttdirect/core/Dispatcher.run
  (Bytecode PC:1(Compiled Code))
  4XESTACKTRACE    at java/lang/Thread.run(Bytecode PC:13)
  .
  This was seen when using the MicroBroker Bridge Dispatcher
  which uses WMQ JMS. The problem can also occur without
  the use of the MicroBroker.
  .
  KEY WORDS:
  MicroBroker Bridge Dispatcher
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affect users with a multi-threaded asynchronous JMS
  consumer application using WebSphere MQ v7 client jars to
  connect to WebSphere MQ v6 queue manager and which have an
  ExceptionListener registered with the connection.
  
  Platforms affected:
  All Distributed (iSeries, all Unix and Windows) +Java
  ****************************************************************
  PROBLEM SUMMARY:
  In a multi threaded environment, when the same connection object
  is shared across multiple threads, when an attempt is made to
  stop the connection by one thread and if an exception is
  delivered to the ExceptionListener registered with the
  connection at the same instance an hang can occur due to the
  same resource accessed by different threads.
  

Problem conclusion

• APAR IC64514 and IC61714 addressed issues related to avoiding
  hang situations when a connection broken event occurs. But under
  specific scenarios (primarily a thread timing issue) the same
  object is used by two or more threads using the same connection
  object. Hence, when the connection.stop() is invoked, the
  threads wait on each other for the object to be released and
  hence the hang.
  The code has been modified to ensure that once the exception is
  delivered to the ExceptionListener, the object held by the Async
  helper thread is released and the other waiting threads are
  notified about this thereby avoiding the hang situation.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
                     v7.0
  Platform           Fix Pack 7.0.1.2
  --------           --------------------
  Windows            U200316
  AIX                U829807
  HP-UX (PA-RISC)    U829678
  HP-UX (Itanium)    U829681
  Solaris (SPARC)    U829806
  Solaris (x86-64)   U829680
  iSeries            tbc_p700_0_1_2
  Linux (x86)        U829677
  Linux (x86-64)     U829676
  Linux (zSeries)    U829682
  Linux (Power)      U829679
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available, information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

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

  WMQ WINDOWS V7

• Fixed component ID

  5724H7220

Applicable component levels

• R700 PSY

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