The function int pthread_mutex_destroy(pthread_mutex_t *mutex); destroys the mutex referenced by 'mutex'; the mutex object now becomes becomes uninitialized. An implementation may cause pthread_mutex_destroy() to set the object referenced by 'mutex' to an invalid value. A destroyed mutex object can be reinitialized using pthread_mutex_init(); the results of referencing the object after it has been destroyed are undefined. Upon success, it returns a 0; pthread_mutex_destroy() may fail if: -[EBUSY] The implementation has detected an attempt to destroy the object referenced by 'mutex' while it is locked or referenced. -[EINVAL] The value specified by 'mutex' is invalid. It shall not return [EINTR] It shall be safe to destroy an initialized mutex that is unlocked.