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Date: Wed, 5 Feb 2003 09:51:14 +0000
From: Russell King <rmk@arm.linux.org.uk>
To: Rik van Riel <riel@conectiva.com.br>
Cc: Andrew Morton <akpm@digeo.com>, torvalds@transmeta.com,
       linux-kernel@vger.kernel.org, tytso@thunk.org, rddunlap@osdl.org
Subject: Re: [PATCH][RESEND 3] disassociate_ctty SMP fix
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In-Reply-To: <Pine.LNX.4.50L.0302042356580.32328-100000@imladris.surriel.com>; from riel@conectiva.com.br on Tue, Feb 04, 2003 at 11:58:52PM -0200
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On Tue, Feb 04, 2003 at 11:58:52PM -0200, Rik van Riel wrote:
> I guess it's time to fix the caller of this function then,
> since something strange is going on here:
> 
> http://bugme.osdl.org/show_bug.cgi?id=54

I don't think the tty is null there.  It'll be a filp->private_data
being null.

>From the trace, my guess is that a file descriptor is being left
with a null filp->private_data, yet its on the file descriptor list
for the tty, and its fops is set to tty_fops.

I'll see if I can reproduce it here and work out what's going on.
However, note the following (and I think this is the crux of the problem):
release_dev is _supposed_ to run under the BKL.  So how the fsck are we
getting into tty_do_hangup's BKL protected region while also being in
release_dev's BKL protected region?  Is it the BKL which has broken?

-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

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