IT23566: Failures of asynchronous consume operations when machine is very overloaded

APAR status

• Closed as program error.

Error description

• Asynchronous consume operations fail.
  
  A queue manager agent process (amqzlaa0) might also fail
  completely, resulting in connection-broken or connection-hanging
  conditions in all other applications they were serving.
  
  FDCs appear with these details.
  - KN802020 kqiRemoveFromWaiterChainWait xecL_W_TIMEOUT
  - KN346080 kpiMQGETM
  - KN346100 kpiMQGETM
  
  And possibly also
  -  XC130004 xehExceptionHandler/xcsAllocateQuickCell SIGBUS or
  SIGSEGV
  -  XC307030 xlsRequestMutex xecL_W_SEM_OWNER_DIED
  -  ZX005035 zxcProcessChildren zrcX_AGENT_DEAD
  

Local fix

• If using a non-default OS scheduling mode, return to the default
  mode, as this might resolve the issue.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This has been seen only on a Solaris system when using a
  non-default operating system scheduling mode.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  If there are task scheduling anomalies, or if the machine is
  massively overloaded, then there is a timing window in which an
  asynchronous consume operation will abandon waiting for a post
  that was due to be received from the putter.  In this situation
  it will mark its block of memory accordingly.
  
  This is not the defect.  The defect is that a later part of the
  MQ code (running in a subsequent asynchronous consume operation)
  should have noticed that the block was marked, and taken
  specific actions as a result.  This code behaved as expected for
  the normal MQGET case, but was not correctly coded for the
  asynchronous consume case.
  

Problem conclusion

• The MQ code has been corrected so that the special case for
  asynchronous consume is now executed correctly.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v8.0       8.0.0.11
  v9.0 LTS   9.0.0.5
  
  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 MP

• Fixed component ID

  5724H7251

Applicable component levels