From owner-freebsd-current  Sat Jul 20 21:50: 9 2002
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Date: Sun, 21 Jul 2002 14:54:00 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Bakul Shah <bakul@bitblocks.com>
Cc: current@FreeBSD.ORG, <ache@FreeBSD.ORG>
Subject: Re: suspend bug
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On Sun, 21 Jul 2002, Bruce Evans wrote:

> On Thu, 18 Jul 2002, Bakul Shah wrote:
>
> > Try this:
> >
> > $ csh
> > % su
> > Password:
> > % stop $$
> >
> > Suspended (signal)
> > %fg
> >
> > At which point you will lose you login shell.
> >
> > Prior to KSE one could switch between an su'ed shell and a
> > normal shell at will by using stop $$ and fg.
>
> Some more details:
> - this happens for csh but not for bash-1.
> - ktracing everything shows further strange behaviour.  ktrace causes a
>   kernel printf "Out of ktrace request objects.".  The login shell is
>   not lost immediately.  You get a shell prompt, but at least tty echo is
>   broken, and hitting return a few times causes all the shells to exit.
>
> > Is this breakage considered a bug or a feature?
>
> Bug.

The bug is actually in su.  It happens with a pre-KSEIII kernel.  Backing
out rev.1.54 of su.c (which was apparently supposed to fix a related bug
tcsh's fg command) fixes it.

Bruce


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