linux-kernel - Re: 2.6.25.3: su gets stuck for root

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Message-ID: <20080602091016.571dda7c@core>
Date:	Mon, 2 Jun 2008 09:10:16 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Willy Tarreau <w@....eu>
Cc:	Harald Dunkel <harald.dunkel@...nline.de>,
	Joe Peterson <joe@...rush.com>, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...hat.com>
Subject: Re: 2.6.25.3: su gets stuck for root

> 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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