VMS Help POSIX Threads, TIS routines, tis_cond_timedwait, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    If threads are not present, this function is equivalent to
    sleep().

    This routine causes a thread to wait until one of the following
    occurs:

    o  The specified condition variable is signaled or broadcast.

    o  The current system clock time is greater than or equal to the
       time specified by the abstime argument.

    This routine is identical to tis_cond_wait(), except that this
    routine can return before a condition variable is signaled or
    broadcast, specifically, when the specified time expires. For
    more information, see the tis_cond_wait() description.

    This routine atomically releases the mutex and causes the calling
    thread to wait on the condition. When the thread regains control
    after calling tis_cond_timedwait(), the mutex is locked and the
    thread is the owner. This is true regardless of why the wait
    ended. If general cancelability is enabled, the thread reacquires
    the mutex (blocking for it if necessary) before the cleanup
    handlers are run (or before the exception is raised).

    If the current time equals or exceeds the expiration time, this
    routine returns immediately, releasing and reacquiring the mutex.
    It might cause the calling thread to yield (see the sched_yield()
    description). Your code should check the return status whenever
    this routine returns and take the appropriate action. Otherwise,
    waiting on the condition variable can become a nonblocking loop.

    Call this routine after you have locked the mutex specified
    in mutex. The results of this routine are unpredictable if
    this routine is called without first locking the mutex. The
    only routines that are supported for use with asynchronous
    cancelability enabled are those that disable asynchronous
    cancelability.