struct mg_context {
    char        *options[NUM_OPTIONS];    /* Configured opions    */
    pthread_mutex_t    opt_mutex[NUM_OPTIONS];    /* Option protector    */
    int        max_threads;    /* Maximum number of threads    */
    int        num_threads;    /* Number of threads        */
    int        num_idle;    /* Number of idle threads    */
    pthread_mutex_t    thr_mutex;    /* Protects (max|num)_threads    */
    pthread_cond_t    thr_cond;
    pthread_mutex_t    bind_mutex;    /* Protects bind operations    */
};

以上，每一个变量都有对应的锁，假设有一个线程获得了opt_mutex[0],然后需要对
options[0]这个字符串进行修改，然后又有一个线程需要修改max_threads,
那这个线程可以成功获得thr_mutex锁吗？如果能的话，它能立即就修改max_threads吗？