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Date: Wed, 23 Jan 2013 17:38:42 +0100
Message-ID: <s5hk3r3etwt.wl%tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fbdev-devel@lists.sourceforge.net,
        Alan Cox <alan@lxorguk.ukuu.org.uk>, Alan Cox <alan@linux.intel.com>
Subject: Re: [PATCH 1/2] fb: Rework locking to fix lock ordering on takeover
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References: <1358958309-5342-1-git-send-email-daniel.vetter@ffwll.ch>
	<1358958309-5342-2-git-send-email-daniel.vetter@ffwll.ch>
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At Wed, 23 Jan 2013 17:25:08 +0100,
Daniel Vetter wrote:
> 
> From: Alan Cox <alan@lxorguk.ukuu.org.uk>
> 
> 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@linux.intel.com>
> [danvet: Tiny whitespace cleanup.]
> Reported-and-tested-by: Hugh Dickins <hughd@google.com>
> Reported-and-tested-by: Sasha Levin <levinsasha928@gmail.com>
> References: https://lkml.org/lkml/2012/10/25/516
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

FYI, the latest patch of this is found in mm tree:
  http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover.patch

Also I hit the same problem in another code paths (for unbind and
unregister):
  http://marc.info/?t=135309396400003&r=1&w=2

My additional patch is found in mm tree, too:
  http://ozlabs.org/~akpm/mmots/broken-out/fb-yet-another-band-aid-for-fixing-lockdep-mess.patch


Takashi