setup_loginuid (gpointer data)
{
        const char *id = data;
        int fd;

        fd = open ("/proc/self/loginuid", O_WRONLY);
        write (fd, id, strlen (id));
        close (fd);
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.