Re: [PATCH 1/2] fb: Rework locking to fix lock ordering on takeover

Takashi Iwai <[email protected]> Wed, 23 Jan 2013 17:38:42 +0100

Newsgroups	gmane.linux.kernel,gmane.comp.freedesktop.xorg.drivers.intel,gmane.comp.video.dri.devel,gmane.linux.fbdev.devel
Message-ID	<s5hk3r3etwt.wl%[email protected]>

At Wed, 23 Jan 2013 17:25:08 +0100,
Daniel Vetter wrote:
> 
> From: Alan Cox <[email protected]>
> 
> 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 <[email protected]>
> [danvet: Tiny whitespace cleanup.]
> Reported-and-tested-by: Hugh Dickins <[email protected]>
> Reported-and-tested-by: Sasha Levin <[email protected]>
> References: https://lkml.org/lkml/2012/10/25/516
> Signed-off-by: Daniel Vetter <[email protected]>

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