linux-kernel - Re: [PATCH] fb: Rework locking to fix lock ordering on takeover

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Message-ID: <CA+5PVA5iQwYOcoSYtLOoRBHaTNJANdv+X-C78474n3SzZg_m9w@mail.gmail.com>
Date:	Tue, 18 Dec 2012 10:20:10 -0500
From:	Josh Boyer <jwboyer@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, florianschandinat@....de
Subject: Re: [PATCH] fb: Rework locking to fix lock ordering on takeover

On Wed, Nov 21, 2012 at 7:53 AM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Wed, 21 Nov 2012 07:45:45 -0500
> Josh Boyer <jwboyer@...il.com> wrote:
>
>> On Fri, Nov 16, 2012 at 2:27 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> >
>> > [The fb maintainer appears to be absent at the moment].
>> >
>> > This is needed to fix a pile of lockdep splats that now show up because console_lock()
>> > is being properly audited. Hugh Dickins and Sasha Levin have tested it and both reports
>> > all looks good. This is probably not the whole story - the entire fb layer has locking
>> > confusion problems that were previously hidden but it seems to get the ones people hit
>> > in testing. This hopefully explains a few of the weird fb hangs that have been floating
>> > around forever.
>> >
>> > From: Alan Cox <alan@...ux.intel.com>
>> >
>> > Adjust the console layer to allow a take over call where the caller already
>> > holds the locks. Make the fb layer lock in order.
>> >
>> > This s partly a band aid, the fb layer is terminally confused about the
>> > locking rules it uses for its notifiers it seems.
>> >
>> > Signed-off-by: Alan Cox <alan@...ux.intel.com>
>>
>> Should this eventually get into the stable trees?
>
> Thats a question I'm not sure about at this point. I think the bug is
> real but not caught by the lock checker in older trees but I've not
> investigated.

So... this patch seems to still be twisting in the wind.  It should
probably be headed into 3.8 at this point, shouldn't it?

josh
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