IV15882: WEBSPHERE MQ CLASSES FOR JMS MAY HANG WHEN CREATING A JMS MESSAGE LISTENER ON A STARTED JMS CONNECTION

WebSphere MQ V7.0 Fix Pack 7.0.1.9

APAR status

• Closed as program error.

Error description

• The WebSphere MQ classes for JMS client libraries hang when
  using the the 7.0.1.7 version.  This occurred when a message
  listener was set on a JMS connection which has been started.
  
  Upon examination of a Java thread dump when the hang had
  occurred shows the following stack:
  
  at java/lang/Object.wait(Native Method)
  at java/lang/Object.wait(Bytecode PC:3(Compiled Code))
  at
  com/ibm/msg/client/commonservices/ReentrantMutex.acquire(Byteco
  de PC:175(Compiled Code))
  at
  com/ibm/msg/client/commonservices/ReentrantMutex.acquire(Byteco
  de PC:3(Compiled Code))
  at
  com/ibm/msg/client/jms/internal/JmsMessageProducerImpl.send_(By
  tecode PC:84)
  at
  com/ibm/msg/client/jms/internal/JmsMessageProducerImpl.send(Byt
  ecode PC:56)
  at
  com/ibm/rcp/integrator/queuedispatchersvc/impl/QueueDispatcherI
  nBoundMessageListener.handleFragmentedFileMessages(Bytecode PC:
  1086)
  at
  com/ibm/rcp/integrator/queuedispatchersvc/impl/QueueDispatcherI
  nBoundMessageListener.onMessage(Bytecode PC:619)
  at
  com/ibm/msg/client/jms/internal/JmsMessageConsumerImpl$JmsProvi
  derMessageListener.onMessage(Bytecode PC:246)
  at
  com/ibm/msg/client/mqtt/internal/ProviderMessageConsumerMqttImp
  l$MessageListener.messageArrived(Bytecode PC:18)
  at
  com/ibm/mqttclient/v4/internal/extended/MqttConsumerImpl.messag
  eArrived(Bytecode PC:42)
  at
  com/ibm/mqttclient/v4/internal/extended/MqttSessionImpl.run(Byt
  ecode PC:117)
  at java/lang/Thread.run(Bytecode PC:13)
  

Local fix

• None; use 7.0.1.6 JMS Client libraries.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users of message listeners in standalone applications using
  WebSphere MQ classes for JMS, including versions:
  
  v7.0.1.7
  v7.0.1.8
  
  Platforms affected:
  All Distributed (iSeries, all Unix and Windows) +Java +Java zOS
  ****************************************************************
  PROBLEM SUMMARY:
  This hang state occurred when the following sequence of events
  is used:
  
  1. A JMS Connection is created and started.
  
  2. A JMS Session is created from the Connection, and a
  MessageConsumer is created from this Session.
  
  3. The setMessageListener method is invoked on the
  MessageConsumer to create a message listener.
  
  3. The message listener's onMessage() method is invoked, during
  which the same Session that the MessageConsumer was created
  under is used.  For example, a message is sent to a Destination
  where the MessageProducer created from the Session.
  
  
  A lock on the Session object was acquired while setting the
  message listener which was not released when the Session
  switched from synchronous mode to asynchronous mode while
  setting the message listener.
  
  This subsequently led to a thread hang where a Object.wait()
  method call was called, with no other thread to notify and
  stop the wait() from being indefinite.
  
  This behaviour was introduced by the APAR IV00757, which was
  associated with changing the locking behaviour of
  MessageConsumers and Sessions to avoid a deadlock.  This APAR,
  IV00757, was included in the WebSphere MQ classes for JMS fix
  pack 7.0.1.7.
  

Problem conclusion

• The code was modified such that the lock is released when the
  method to set the message listener on the message consumer
  completes.  This means that when the Session is used within
  the onMessage() implementation, the lock can be acquired and the
  thread does not hang.
  
  
  
  | MDVREGR 7.0.1-WS-MQ-AixPPC64-FP0006       |
  | MDVREGR 7.0.1-WS-MQ-HpuxIA64-FP0006       |
  | MDVREGR 7.0.1-WS-MQ-HpuxPaRISC64-FP0006   |
  | MDVREGR 7.0.1-WS-MQ-LinuxIA32-FP0006      |
  | MDVREGR 7.0.1-WS-MQ-LinuxPPC64-FP0006     |
  | MDVREGR 7.0.1-WS-MQ-LinuxS390X-FP0006     |
  | MDVREGR 7.0.1-WS-MQ-LinuxX64-FP0006       |
  | MDVREGR 7.0.1-WS-MQ-SolarisSparc64-FP0006 |
  | MDVREGR 7.0.1-WS-MQ-SolarisX64-FP0006     |
  | MDVREGR 7.0.1-WS-MQ-Windows-FP0006        |
  
  | MDVREGR 7.0.1-WS-MQ-AixPPC64-FP0007       |
  | MDVREGR 7.0.1-WS-MQ-HpuxIA64-FP0007       |
  | MDVREGR 7.0.1-WS-MQ-HpuxPaRISC64-FP0007   |
  | MDVREGR 7.0.1-WS-MQ-LinuxIA32-FP0007      |
  | MDVREGR 7.0.1-WS-MQ-LinuxPPC64-FP0007     |
  | MDVREGR 7.0.1-WS-MQ-LinuxS390X-FP0007     |
  | MDVREGR 7.0.1-WS-MQ-LinuxX64-FP0007       |
  | MDVREGR 7.0.1-WS-MQ-SolarisSparc64-FP0007 |
  | MDVREGR 7.0.1-WS-MQ-SolarisX64-FP0007     |
  | MDVREGR 7.0.1-WS-MQ-Windows-FP0007        |
  
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.0       7.0.1.9
  
  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 AIX V7

• Fixed component ID

  5724H7221

Applicable component levels

• R701 PSY

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