Re: No timed lock on MacOS

[Jim Jagielski]

pthread_cond_timedwait() is available under OSX but neither
PTHREAD_CONDATTR_SETPSHARED or pthread_condattr_setpshared are.

Here's a version we can use for any that lack a real pthread_mutex_timedlock():

/*
 * A pthread_mutex_timedlock() impl for OSX/macOS, which lacks the
 * real thing.
 * NOTE: Unlike the real McCoy, won't return EOWNERDEAD, EDEADLK
 *       or EOWNERDEAD
 */
static int macos_pthread_mutex_timedlock(pthread_mutex_t *mutex, const struct 
timespec *abs_timeout)
{
    int rv;
    struct timespec remaining, slept, ts;

    remaining = *abs_timeout;
    while ((rv = pthread_mutex_trylock(mutex)) == EBUSY) {
        ts.tv_sec = 0;
        ts.tv_nsec = (remaining.tv_sec > 0 ? 10000000 : 
                     (remaining.tv_nsec < 10000000 ? remaining.tv_nsec : 
10000000));
        nanosleep(&ts, &slept);
        ts.tv_nsec -= slept.tv_nsec;
        if (ts.tv_nsec <= remaining.tv_nsec) {
            remaining.tv_nsec -= ts.tv_nsec;
        }
        else {
            remaining.tv_sec--;
            remaining.tv_nsec = (1000000 - (ts.tv_nsec - remaining.tv_nsec));
        }
        if (remaining.tv_sec < 0 || (!remaining.tv_sec && remaining.tv_nsec <= 
0)) {
            return ETIMEDOUT;
        }
    }

    return rv;
}