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IC97860: WEBSPHERE MQ V7.0.1 .NET APPLICATION CRASHING WITH ACCESS VIOLATION DURING ATTEMPT TO DISCONNECT

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APAR status

  • Closed as program error.

Error description

  • WebSphere MQ v7.0.1 .NET application intermittently crashes
    after several hours runtime.
    The application crashes with error message "Access Violation
    at address FFFFFFFFFFFFFFFF"
    
    A First Failure report is generated with the following:
     Probe Id :- XC130031
     Component :- xehExceptionHandler
     UserID :- USER1
     Major Errorcode :- xecF_E_UNEXPECTED_SYSTEM_RC
     Probe Description :- AMQ6109: An internal WebSphere MQ error
    has occurred.
     Comment1 :- Access Violation at address FFFFFFFFFFFFFFFF when
    reading
    
    Stack:
    xcsWaitThread
    ccxFreeConv
    reqFreeSess
    reqFreeConn
    rzstMQDISC
    tmzstMQDISC
    MQDISC
    
    Trace shows:
     System.AccessViolationException: Attempted to read or write
    protected memory. This is often an indication that other
    memory is corrupt.
     at IBM.WMQ.Nmqi.Native.MQDISC
     ...
     at IBM.WMQ.MQQueueManager.Disconnect()
    

Local fix

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    Users of MQ v7.0.1 .net client calling multiple
    connect/disconnect under high load.
    
    
    Platforms affected:
    Windows
    
    ****************************************************************
    PROBLEM SUMMARY:
    A dot net client crashes with an access violation exception
    during disconnect with a stack trace as below:
    System.AccessViolationException: Attempted to read or write
    protected memory. This is often an indication that other
    memory is corrupt.
       at IBM.WMQ.Nmqi.Native.MQDISC(Int32& hConn, Int32&
    compCode, Int32& reason)
       at IBM.WMQ.Nmqi.UnmanagedNmqiMQ.MQDISC(Phconn phconn,
    Int32& pCompCode, Int32& pReason)
       at IBM.WMQ.MQQueueManager.Disconnect()
    
    An FDC with probe ID XC130003 is generated reporting an access
    violation which causes the WebSphere MQ client application to
    crash. The client calls multiple connect and disconnect calls
    and sporadically encounters this exception under heavy load.
    
    The FDC has the following stack:
    
    MQQueueManager.Disconnect()1
    UnmanagedNmqiMQ.MQDISC(Phconn,out int,out int)
    MQDISC
    MQDISC
    reqFreeConn
    reqFreeSess
    ccxFreeConv
    xcsWaitThread
    xcsFFST
    
    This happens when the disconnect call is waiting for the
    receiver thread to end and the receiver thread is already ending
    and is waiting for a mutex which has been held by another
    thread.
    

Problem conclusion

  • The fix ensures that MQ checks to see if the thread is active
    before trying to close it in the xcsWaitThread method. Also
    the code change ensures that the thread locking the mutex
    required by the receive thread, performs its work without
    holding a lock on the mutex as its not required.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v7.0       7.0.1.12
    
    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 number

    IC97860

  • Reported component name

    WMQ WINDOWS V7

  • Reported component ID

    5724H7220

  • Reported release

    701

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-11-21

  • Closed date

    2013-12-04

  • Last modified date

    2013-12-04

  • 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 WINDOWS V7

  • Fixed component ID

    5724H7220

Applicable component levels

  • R701 PSY

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Document Information

Modified date:
04 December 2013