IT27849: MQ async consume client may hang during MQDISC

APAR status

• Closed as program error.

Error description

• The MQ asynchronous client thread can hang during an MQDISC if
  MQAPI calls are made in the callback function.
  
  A captured MQ trace will show following sequence of calls for
  the hanging thread.
  
  06:32:50.405760   5268.1      RSESS:000011 !! - MQDISC >>
  06:32:50.405762   5268.1      RSESS:000011 !! - Hconn:
  06:32:50.405770   5268.1      RSESS:000011 !! - MQI:MQDISC
  HConn=01000019
  06:32:50.405772   5268.1      RSESS:000011 (03)----{  rpqMQCTL
  ..
  06:32:50.405789   5268.1      RSESS:000011 (04)-----{
  reqReleaseConn
  06:32:50.405791   5268.1      RSESS:000011 (04)-----}
  reqReleaseConn (rc=OK)
  06:32:50.405793   5268.1      RSESS:000011 (04)-----{
  xcsPostThreadEvent
  06:32:50.405797   5268.1      RSESS:000011 (04)-----}
  xcsPostThreadEvent (rc=OK)
  06:32:50.405799   5268.1      RSESS:000011 (04)-----{
  xcsWaitThreadEvent
  
  Before the hang, a communication error happens on the dispatch
  thread.
  
  06:31:30.174188   5268.19     RSESS:000011 --------{  MQCMIT
  06:31:30.174193   5268.19     RSESS:000011 ---------{
  reqGetConn
  06:31:30.174195   5268.19     RSESS:000011 ----------{
  zutLookupGet
  06:31:30.174199   5268.19     RSESS:000011 hLook=6B9223F0
  Flags=0x00000001 Identifier=0x01000019 pUseCount=0B19F47C
  phEntry=0B19F524
  06:31:30.174203   5268.19     RSESS:000011 Data: 0x01000019
  ..
  06:31:30.174962   5268.19     RSESS:000011 (10)-----------}
  ccxSend
  (rc=OK)
  06:31:30.174974   5268.19     RSESS:000011 (10)-----------{
  ccxReceive
  06:31:46.156463   5268.19     RSESS:000011 (11)------------}!
  ccxReceiveAsync (rc=rrcE_COMMUNICATIONS_ERROR)
  06:31:46.156469   5268.19     RSESS:000011 (10)-----------}!
  ccxReceive
  (rc=rrcE_COMMUNICATIONS_ERROR)
  

Local fix

Problem summary

• ****************************************************************
  USERS AFFECTED:
  Users using the MQ client with asynchronous consume and call the
  MQAPI in its callback function.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  If the MQ async consume application calls the MQAPI in its
  callback function and receives a communication error, then some
  of the connection resources are freed too early. When an MQDISC
  is run from the main thread this hangs while it attempts to
  cleanup the associated dispatcher thread which performed the
  callback actions.
  

Problem conclusion

• The code causing the hang has been corrected to fix the issue.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v9.0 LTS   9.0.0.7
  v9.1 CD    9.1.3
  v9.1 LTS   9.1.0.3
  
  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

  IBM MQ BASE M/P

• Fixed component ID

  5724H7261

Applicable component levels