Where is new session creation in init-getty-login

[Михаил Кипа]

I can`t find the place in  the source where new session creates when I login via local terminal. 
There 
 is no call to setsid() after init forks in start_getty(session_t *sp) and no calls to that 
function in 
 getty and login. But when I login to the local terminal, exit and login again I will have 
different 
 session ID`s (pid numbers of session leader process). So I wan`t to know where login process 
become a 
 session leader?
 
 Mihail.