int
evthread_use_pthreads_with_flags(int flags)
{
        ...;

	pthread_mutex_lock(&once_init_lock); //HERE
	if (once_init == 1) {
		pthread_mutex_unlock(&once_init_lock);
		return 0;
	}

	if (pthread_mutexattr_init(&attr_default)) 
		goto error;

	/* Set ourselves up to get recursive locks. */
	if (pthread_mutexattr_init(&attr_recursive))
		goto error;
	if (pthread_mutexattr_settype(&attr_recursive, PTHREAD_MUTEX_RECURSIVE))
		goto error;

	if (flags & EVTHREAD_PTHREAD_PRIO_INHERIT) {
#ifdef EVENT__HAVE_PTHREAD_MUTEXATTR_SETPROTOCOL
		/* Set up priority inheritance */
		if (pthread_mutexattr_setprotocol(&attr_default, PTHREAD_PRIO_INHERIT))
			goto error;
		if (pthread_mutexattr_setprotocol(&attr_recursive, PTHREAD_PRIO_INHERIT))
			goto error;
#else
		goto error;
#endif
	}

	evthread_set_lock_callbacks(&cbs);
	evthread_set_condition_callbacks(&cond_cbs);
	evthread_set_id_callback(evthread_posix_get_id);
	once_init = 1;

	return 0;             // the lock onece_init_lock may be unreleased
error:
	pthread_mutex_unlock(&once_init_lock);
	return -1;
}