ns_critsec create creates a critical section and returns a critical section ID.
ns_critsec destroy destroys the specified critical section. The csid argument is the critical section ID returned by ns_critsec create when the critical section was created.
ns_critsec enter enters the specified critical section. The csid argument is the critical section ID returned by ns_critsec create when the critical section was created.
ns_critsec leave leaves the specified critical section. The csid argument is the critical section ID returned by ns_critsec create when the critical section was created.