linux-kernel - Re: 3.8-rc2 lockdep complains about console_lock vs. fb_notifier

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Message-ID: <s5hpq1531yn.wl%tiwai@suse.de>
Date:	Wed, 16 Jan 2013 10:35:12 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	sedat.dilek@...il.com
Cc:	Jiri Kosina <jkosina@...e.cz>, linux-fbdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, alan@...rguk.ukuu.org.uk,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: 3.8-rc2 lockdep complains about console_lock vs. fb_notifier_list.rwsem

At Wed, 16 Jan 2013 10:21:46 +0100,
Sedat Dilek wrote:
> 
> On Tue, Jan 15, 2013 at 3:25 PM, Takashi Iwai <tiwai@...e.de> wrote:
> > At Sat, 5 Jan 2013 13:13:27 +0100,
> > Sedat Dilek wrote:
> >>
> >> Hi Jiri,
> >>
> >> ...known issue (see thread in [1]), please feel free to test patches
> >> from Alan and Andrew (see [1], [2] and [3]) and report.
> >>
> >> Regards,
> >> - Sedat -
> >>
> >> [1] http://marc.info/?t=135309396400003&r=1&w=2
> >> [2] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover.patch
> >> [3] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover-fix.patch
> >> [4] http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover-fix-2.patch
> >
> > I've hit this bug and tried the patch [2] ([3] and [4] are gone).
> > Unfortunately the deadlock is still reported, as seen below.
> >
> > A similar fix for fbcon_unbind(), splitting an unlocked version of
> > unbind_con_driver() and call it?
> >
> > (BTW, the patch [2] contains strange characters in the comments, and
> >  has a few coding issues easily detected by checkpatch.pl.)
> >
> 
> [ CCing Rafael as he asked in another thread if I had sent a patch ]
> 
> I noticed also some these "strange" chars in the patch from Andrew and
> a patch of mine was sent as
> "fb-Rework-locking-to-fix-lock-ordering-on-takeover-fix-comments.patch"
> to the lists.
> 
> It is strange to me that Andrew or other maintainers himself did not
> check with "checkpatch.pl".
> This should be a common testcase!
> Hey, noone is perfect :-).
> ( /me has also not checked with that script - I just saw it. )
> 
> Just as a note to the issue in general:
> Andrew took over the patch from Alan which is very honest - he is not
> the active TTY maintainer!
> Didn't Greg takeover maintenance from Alan (after a dispute and blaming Alan)?
> If this is true, why the hell is Greg not CCed?

Let's do it :)

Greg, Jiri, this bug hits already quite a few people.

I can reproduce the bug easily on a machine with a radeon graphics.
It appears always at boot when lockdep is enabled.


> Thanks for the real patch in the followup of this thread!
> Who will take care of it :-)?

Either tty maintainer, or fb maintainer, or Andrew?

FWIW, Andrew took my patch in mm:
  http://ozlabs.org/~akpm/mmots/broken-out/fb-rework-locking-to-fix-lock-ordering-on-takeover.patch
  http://ozlabs.org/~akpm/mmots/broken-out/fb-yet-another-band-aid-for-fixing-lockdep-mess.patch


thanks,

Takashi
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