4.2 oddity -- SLOGIN flag in proc.h

[Robert Elz]

In article <607 at brl-tgr.ARPA>, scc%computer-lab.cambridge.ac.uk at ucl-cs.arpa (Stephen Crawley) writes:
> The <sys/proc.h> header file contains the following line :-
> 
> #define	SLOGIN	0x0800000	/* a login process (legit child of init) */
> 
> However, ps -axl indicates that this bit is not set for any processes.

Well, I hope its not set (on your, or any 4.2bsd or 4.3bsd system)
but I assure you that it is set on my system (Melbourne Australia).

> While making sure that the flag gets set would seem to be straight forward,
> I'm not convinced that it would be stunningly useful. 

Well, it has its uses on my system - its related to the scheduling
stuff that we have that requires the kernel to be able to detect
when a user logs out (so it can send data to a daemon process
waiting to record information about scheduling, so when he logs in
again, minutes/hours/days/months later, things can be restored to
their previous values (this is a gross simplification)).

The flag is retained in proc.h so that no-one else will "accidentally"
re-use the bit (or the name).  Someday, perhaps, in the distant future,
the Melbourne stuff might become a config option in 4.x bsd, just
like the disc quota stuff is at the minute.

Robert Elz			kre at munnari.oz			(Australia)
				seismo!munnari!kre		(uucp)
				kre%munnari.oz at seimso.css.gov	(arpa)
		(temporarily)	ucvbax!kre or kre at ucbvax.berkeley.edu

ps: I believe that I said much of this before, not very long ago...