IT43854: A MQ classes for JMS application reaches a deadlock condition when comparing MQDestination objects

APAR status

• Closed as program error.

Error description

• An MQ classes for JMS application reaches a deadlock condition
  when two (or more) threads are simultaneously comparing MQ
  classes for JMS Destination objects.
  This was observed within a Spring application prior to the
  application attempting to put a message to a queue.
  
  The JVM reported the following deadlock messages and thread
  stacks for the two threads:
  
  Thread ID[120] Deadlocked on
  Lock[java.util.Collections$SynchronizedMap@1fcfd9fb] held by
  Thread ID[121]:
  
  java.base@11.0.18.0.1/java.util.Collections$SynchronizedMap.get(
  Collections.java:2594)
  
  com.ibm.msg.client.jms.internal.JmsPropertyContextImpl.getObject
  Property(JmsPropertyContextImpl.java:582)
  
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.g
  etStringProperty(JmsReadablePropertyContextImpl.java:358)
  
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.c
  ompareContexts(JmsReadablePropertyContextImpl.java:924)
  
  com.ibm.msg.client.jms.admin.JmsDestinationImpl.equals(JmsDestin
  ationImpl.java:854)
  
  org.springframework.jms.connection.CachingConnectionFactory$Dest
  inationCacheKey.destinationEquals(CachingConnectionFactory.java:
  548)
   ... ... ...
  
  
  Thread ID[121] Deadlocked on
  Lock[java.util.Collections$SynchronizedMap@782351bc] held by
  Thread ID[120]:
  
  java.base@11.0.18.0.1/java.util.Collections$SynchronizedMap.get(
  Collections.java:2594)
  
  com.ibm.msg.client.jms.internal.JmsPropertyContextImpl.getObject
  Property(JmsPropertyContextImpl.java:582)
  
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.g
  etStringProperty(JmsReadablePropertyContextImpl.java:358)
  
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.c
  ompareContexts(JmsReadablePropertyContextImpl.java:924)
  
  com.ibm.msg.client.jms.admin.JmsDestinationImpl.equals(JmsDestin
  ationImpl.java:854)
  
  org.springframework.jms.connection.CachingConnectionFactory$Dest
  inationCacheKey.destinationEquals(CachingConnectionFactory.java:
  548)
   ... ... ...
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users of the MQ classes for JMS.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  An application utilising the MQ classes for JMS can compare two
  JMS Destination object instances, for example by calling the
  method:
  
  com.ibm.mq.jms.MQDestination.equals(
  com.ibm.mq.jms.MQDestination );
  
  APAR IT27638 reported a problem where this comparison could
  result in a deadlock condition if multiple threads were doing
  this comparison concurrently.  The code change associated with
  this deadlock (put into the MQ 9.0 and 9.1 LTS releases)
  resolved the problem by taking a snapshot of each object before
  comparing the objects.
  
  An alternative solution was used for the development release at
  the time (MQ 9.1 CD) which offered higher performance.  However
  this solution was then found to still reach the deadlock
  condition if the comparison was being performed by multiple
  threads in the same millisecond.
  
  To re-cap on the previous APAR, the conditions for this deadlock
  were:
  
  Two MQDestination object instances:
  
    com.ibm.mq.jms.MQDestination destination1
    com.ibm.mq.jms.MQDestination destination2
  
  Thread 1:
    destination1.equals(destination2)
  
  Thread 2:
    destination2.equals(destination1)
  
  which could result in two threads deadlocked against each other
  with the thread stacks:
  
  java.util.Collections$SynchronizedMap.get
  com.ibm.msg.client.jms.internal.JmsPropertyContextImpl.getObject
  Property
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.g
  etStringProperty
  com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.c
  ompareContexts
  com.ibm.msg.client.jms.admin.JmsDestinationImpl.equals
  

Problem conclusion

• The code solution associated with this APAR has updated the
  algorithm used internally to compare the two objects to ensure
  that the locks associated with each Destination object are taken
  in the same order, which prevents the possibility of the
  deadlock occurring.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.2 LTS   9.2.0.20
  v9.3 LTS   9.3.0.10
  v9.x CD    9.3.4
  
  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

  MQ APPL M2002 V

• Fixed component ID

  5737H4701

Applicable component levels