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PM79703: BROKER HANG TASK HUNG

A fix is available

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APAR status

  • Closed as program error.

Error description

  • Two tasks hung.
    WMB two flows at 2 different times stopped processing.
    .
    Additional keywords:
    CSQBLB46 CSQBBCMH CSQAGLCK
    Execution Group EG
    curdepth
    
    MQMSGPROP/K
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 7 *
    *                 Release 0 Modification 1 and Release 1       *
    *                 Modification 0.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: A multithreaded application using       *
    *                      message handles may encounter a hang    *
    *                      after issuing an MQDLTMH verb.          *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Multithreaded applications using MQCRTMH and MQDLTMH may
    encounter a hang.
    
    When MQDLTMH is issued to delete a message handle there is a
    concurrency problem with the serialisation of latches on the
    associated control blocks.
    
    If multiple threads go through this processing together, one
    gets the latch, and the others wait via a PAUSE until the latch
    is released by the first task.
    
    The waiting tasks each add a request block to the lock chained
    off of the ASABLOCK field so that the task currently holding the
    latch knows who to resume when the latch is freed.  There is a
    small window that can allow the first task to set the ASABLOCK
    value to zeros and subsequently fail to resume any of the
    waiting tasks.
    

Problem conclusion

  • The code has been changed prevent the zeroing of the ASABLOCK
    when there are tasks waiting to be resumed.
    010Y
    100Y
    CSQAFB31
    CSQAFRMN
    CSQAGTMN
    CSQASFIX
    CSQBCRMH
    CSQBPAPI
    

Temporary fix

Comments

APAR Information

  • APAR number

    PM79703

  • Reported component name

    WMQ Z/OS V7

  • Reported component ID

    5655R3600

  • Reported release

    010

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2012-12-24

  • Closed date

    2013-02-27

  • Last modified date

    2013-10-01

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

    UK92055 UK92056

Modules/Macros

  • CSQAFB31 CSQAFRMN CSQAGTMN CSQASFIX CSQBCRMH
    CSQBPAPI
    

Fix information

  • Fixed component name

    WMQ Z/OS V7

  • Fixed component ID

    5655R3600

Applicable component levels

  • R010 PSY UK92055

       UP13/04/04 P F304

  • R100 PSY UK92056

       UP13/04/04 P F304

Fix is available

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Document Information

Modified date:
01 October 2013