原來 win32 pthread 的 mutex 預設是不能 recursive 的.
要多設定 pthread mutexattr 來打開 recursive 的功能.

程式如下:

    pthread_mutex_t      mutex;
    pthread_mutexattr_t mutexattr;

    pthread_mutexattr_init(&mutexattr);
    pthread_mutexattr_settype(&mutexattr,PTHREAD_MUTEX_RECURSIVE);
  
    pthread_mutex_init(&mutex,&mutexattr);
    pthread_mutexattr_destroy(&mutexattr);

    pthread_mutex_lock(&mutex);
    pthread_mutex_unlock(&mutex);

    pthread_mutex_destroy(&mutex);