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Problem Report 2124 Details

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Report 2124 Actions

    Problem Report Number 2124
    Submitter's Classification Test Suite problem
    State Resolved
    Resolution Test Suite Deficiency (TSD)
    Problem Resolution ID TSD.X.1089
    Raised 2001-02-07 08:00
    Updated 2003-03-13 08:00
    Published 2001-03-15 08:00
    Product Standard Internationalised System Calls and Libraries Extended V2 (UNIX 98)
    Certification Program The Open Brand certification program
    Test Suite VSTH version 5.2.1
    Test Identification PTHR.os/mutexattr_rt/pthread_mutexattr_setprotocol 5
    Problem Summary TSD5TH.00086 This is a resubmit of PG5TH.0001. The reason for the test failure is the test does a pthread_cond_broadcast() and then expects the threads waiting on the mutex to acquire it in priority order. Accordi...
    Problem Text
    This is a resubmit of PG5TH.0001.

    The reason for the test failure is the test does a
    pthread_cond_broadcast() and then expects the threads waiting on the
    mutex to acquire it in priority order.

    According to System Interfaces and Headers, Issue 5:

    "The pthread_cond_broadcast() call unblocks all threads currently
    blocked on the specified condition variable cond.

    If more than one thread is blocked on a condition variable, the
    scheduling policy determines the order in which threads are
    unblocked. When each unblocked as a result of pthread_cond_signal()
    or pthread_cond_broadcast() returns from its call to
    pthread_cond_wait() or pthread_cond_timedwait(), the threads owns the
    mutex with which it called pthread_cond_wait() or
    pthread_cond_timedwait(). The thread(s) that are unblocked contend
    for the mutex according to the scheduling policy (if applicable),
    and as if each had called pthread_mutex_lock()."

    According to POSIX.1c Standard Section 11.4.3.2:

    "pthread_cond_broadcast() unblocks all threads currently blocked , and if more
    that one thread is blocked on a condition variable, the scheduling policy
    determines the order in which threads are unblocked."

    Even if unblocked in priority order, on an machine with X processors,
    the top X priority threads could all be set running simultaneously
    and so a race condition to acquire the mutex occurs. The test assumes
    that the higher priority thread will run before the lower priority
    thread, and hence reach the mutex and acquire it before the other
    thread. This would be true on a uniprocessor or if the library only
    used one CPU. It is false on a multiprocessor when the library uses
    all available CPUs.

    The standard recognizes the existence of such race conditions, else it
    would not provide for a priority inheritence mutex protocol attribute
    (PTHREAD_PRIO_INHERIT) to deal with cases where it matters to the
    application.

    Test Output

    ************************************************************************
    /tset/PTHR.os/mutexattr_rt/pthread_mutexattr_setprotocol/T.pthread_mutex
    attr_setprotocol 5 Failed

    Test Information:
    When a thread owns a mutex whose protocol attribute
    has been set to a value of PTHREAD_PRIO_NONE,
    then its priority and scheduling are not affected by
    its mutex ownership.
    Posix Ref: Component PTHREAD_MUTEXATTR_SETPROTOCOL
    Assertion 9945-1:1996 13.6.1.2-5(A)

    ************************************************************************

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    A test suite deficiency is recommended

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Test Suite Deficiency (TSD)
    Review Conclusion

    Problem Reporting System Options:

     

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