IBM Support

IC99364: LACK OF CHECKS ON RELOCKABLE MUTEX LOCK COUNT COULD LEAD TO NEGATIVE VALUES AND AN INDEFINITE WAIT

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APAR status

  • Closed as program error.

Error description

  • Relockable mutexes exist to allow a thread to lock and unlock
    access to a protected resource multiple times. In normal use the
    number of calls to lock the mutex shall equal the number of
    calls to unlock it. Once the lock count becomes zero the mutex
    is available to other threads to acquire and lock it. If a
    program logic error results in too many calls to unlock the
    mutex a situation could arise whereby another thread could
    successfully lock and unlock the mutex but leave it in a state
    where it is recorded as the owner of the mutex when in fact it
    is not. The result is that a third thread that tries to lock and
    acquire the mutex will wait indefinitely.
    
    The following extract from onstat -g wmx, collected from a
    customer system, demonstrates the problem:
    
    Mutexes with waiters:
    mid      addr             name               holder   lkcnt
    waiter   waittime
    5507     7000014e9378808  bld ref constraint 1006101  -1
    606382   56865
    
    687553   56865
    
    687476   56865
    
    687558   56865
    
    687530   56865
    
    606379   56865
    ...
    
    The thread that last locked the mutex, id 1006101, no longer
    existed when the problem was detected. Hence the other threads
    are forced to wait forever.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All users.                                                   *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Update to IDS-11.70.xC9                                      *
    ****************************************************************
    

Problem conclusion

  • Problem Fixed In IDS-11.70.xC9
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC99364

  • Reported component name

    INFORMIX SERVER

  • Reported component ID

    5725A3900

  • Reported release

    B70

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2014-02-13

  • Closed date

    2017-06-09

  • Last modified date

    2017-06-09

  • 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

    INFORMIX SERVER

  • Fixed component ID

    5725A3900

Applicable component levels

  • RB70 PSY

       UP

  • RC10 PSY

       UP

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Document Information

Modified date:
09 June 2017