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Date: Thu, 19 Sep 2002 11:25:11 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: William Lee Irwin III <wli@holomorphy.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [patch] generic-pidhash-2.5.36-D4, BK-curr
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On Wed, 18 Sep 2002, Linus Torvalds wrote:

> However:
> 
> >  	read_lock(&tasklist_lock);
> > - 	for_each_process(p) {
> > -		if ((tty->session > 0) && (p->session == tty->session) &&
> > -		    p->leader) {
> > -			send_sig(SIGHUP,p,1);
> > -			send_sig(SIGCONT,p,1);
[...]

> This looks a bit wrong. In particular, the old code used to set "p->tty"  
> to NULL if it matched any process, while the new code only does that for
> processes in the right session. Hmm?

i had this code changed back and forth twice already, because i was unsure
whether it's correct. It's true that it's not an equivalent
transformation, but after some thinking it looked correct to me. Isnt
there a 1:1 relationship between the tty and the session ID in this case?
Ie. the previous code was pessimistic and just scanned for matching
p->tty's outside of the tty->session == p->session space, but it should
not have done so.

i'll add some debugging code to the old code to print out cases when
p->tty == tty but p->session != tty->session and start up X, that should
prove or disprove this theory, right?

(i cant remember any other place where the code transformation was not
identity, but will double-check this again.)

William, you did the original transformation, was this optimization done
intentionally?

	Ingo

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