linux-kernel - Re: [Bug 10741] bug in `tty: BKL pushdown'?

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Message-ID: <87ve099yyt.fsf@saeurebad.de>
Date:	Mon, 16 Jun 2008 17:33:14 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Bug 10741] bug in `tty: BKL pushdown'?

Hi,

Alan Cox <alan@...rguk.ukuu.org.uk> writes:

> On Mon, 16 Jun 2008 11:33:13 +0100
> Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>
>> > The bug still exists, however, a bisect on another machine with the same
>> > userland leads to different commit
>> > (47f86834bbd4193139d61d659bebf9ab9d691e37 "redo locking of tty->pgrp"),
>> > so it is not all that clear and stable.
>> 
>> Now that would actually make a lot more sense as a root cause.
>
> Experiment time. In _proc_set_tty() in tty_io.c move the
>
> 	tty->session = get_pid(task_session(tsk));
>
> back inside the lock just before
>
> 	tty->pgrp = get_pid(task_pgrp(tsk));

Like this:?

spin_lock()
put_pid()
put_pid()
tty->session =
tty->pgrp =
spin_unlock()

That does not fix it.

	Hannes
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