Date: Mon, 2 Jun 2008 09:10:16 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Willy Tarreau <w@1wt.eu>
Cc: Harald Dunkel <harald.dunkel@t-online.de>, Joe Peterson <joe@skyrush.com>,
       linux-kernel@vger.kernel.org, Alan Cox <alan@redhat.com>
Subject: Re: 2.6.25.3: su gets stuck for root
Message-ID: <20080602091016.571dda7c@core>
In-Reply-To: <20080602053256.GF5609@1wt.eu>
References: <48434D57.6030801@skyrush.com>
	<48438126.3080308@t-online.de>
	<20080602053256.GF5609@1wt.eu>
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> Guys, you should test if "kill -CONT $pid" wakes the process up.
> It might be possible that some obscure bug appeared in the tty
> code resulting in SIGTTOU sometimes being sent to the caller,
> although that seems rather strange :-/

Not really. The task would get suspended if it attempted to change the
tty settings while not being session leader. This is part of the POSIX
and BSD job control. A race (either kernel or in something like
sshd/bash) would do that and could have been caused by any of the timing
changes recently.

That would also explain why I can't duplicate it, and the sleep
observation.
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