If an error condition occurs, this routine returns an integer
    value indicating the type of error. Possible return values are as
    follows:

    Return      Description

    0           Successful completion, the read-write lock object was
                acquired for read access.
    [EINVAL]    The value specified by rwlock is invalid, or the
                length in characters of name exceeds 31.
    [ENOMEM]    Insufficient memory to create a copy of the object
                name string.