2.4.3.3.1. Posix Mutex Interface
int pthread_mutex_init (pthread_mutex_t *mutex,
                        const pthread_mutex_attr_t *mutexattr);
int pthread_mutex_destroy (pthread_mutex_t *mutex);

int pthread_mutex_lock (pthread_mutex_t *mutex);
int pthread_mutex_trylock (pthread_mutex_t *mutex);
int pthread_mutex_timedlock (pthread_mutex_t *restrict mutex,
                             const struct timespec *abs_timeout);
int pthread_mutex_unlock (pthread_mutex_t *mutex);