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Date: Wed, 20 Dec 2006 20:42:48 +0100 (CET)
From: Martin Blapp <mb@imp.ch>
To: Attilio Rao <attilio@freebsd.org>
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Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org
Subject: Re: cvs commit: src/sys/kern tty.c
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Hi,

>Ok, after a quick look at the patch (and this note) it makes more
>sense to me, but then would not be cleaner to do something like:
>
> sx_slock(&proctree_lock);
> if (tp->t_session && tp->t_session->s_leader) { ...
> }
> sx_sunlock(&proctree_lock);
>

You mean to restore rev. 1.258 ?

http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/kern/tty.c.diff?r1=1.257&r2=1.258

The answer is easy, rev. 1.258 costs more in the cases where tp->t_session is
already empty and we don't need to add a proctree lock and can just continue.
We need the proctree lock only if tp->t_session exists. You can call rev. 1.267
less invasive than rev. 1.258 :-)

--
Martin