A mutex attributes object allows you to specify values for mutex attributes other than the defaults when you create a mutex with the routine pthread_mutex_init( ).
The mutex type attribute specifies whether a mutex is fast, recursive, or nonrecursive. Set the mutex type attribute by calling the routine pthread_mutexattr_setkind_np( ). (Any routine with the _np suffix is a new primitive; see New Primitives.) If you do not use a mutex attributes object to select a mutex type, calling the pthread_mutex_init( ) routine creates a fast mutex by default.