Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755411Ab1CVIhW (ORCPT ); Tue, 22 Mar 2011 04:37:22 -0400 Received: from linux-sh.org ([111.68.239.195]:54477 "EHLO linux-sh.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753875Ab1CVIhR (ORCPT ); Tue, 22 Mar 2011 04:37:17 -0400 Date: Tue, 22 Mar 2011 17:36:24 +0900 From: Paul Mundt To: Herton Ronaldo Krzesinski Cc: Anca Emanuel , Dave Airlie , Linus Torvalds , linux-fbdev@vger.kernel.org, Ben Skeggs , dri-devel@lists.freedesktop.org, Borislav Petkov , Linux Kernel Mailing List , Andy Whitcroft Subject: Re: Linux 2.6.38-rc6 Message-ID: <20110322083624.GH25925@linux-sh.org> References:

<1298596499.10585.27.camel@clockmaker-el6> <20110225144920.GA2337@herton-IdeaPad-Y430> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110225144920.GA2337@herton-IdeaPad-Y430> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2963 Lines: 69 On Fri, Feb 25, 2011 at 11:49:21AM -0300, Herton Ronaldo Krzesinski wrote: > On Fri, Feb 25, 2011 at 03:56:20AM +0200, Anca Emanuel wrote: > > On Fri, Feb 25, 2011 at 3:47 AM, Anca Emanuel wrote: > > > On Fri, Feb 25, 2011 at 3:14 AM, Dave Airlie wrote: > > >> On Thu, 2011-02-24 at 16:54 -0800, Linus Torvalds wrote: > > >>> On Thu, Feb 24, 2011 at 4:48 PM, Anca Emanuel wrote: > > >>> > > > >>> > diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c > > >>> > index e2bf953..e8f8925 100644 > > >>> > --- a/drivers/video/fbmem.c > > >>> > +++ b/drivers/video/fbmem.c > > >>> > @@ -1511,6 +1511,7 @@ void remove_conflicting_framebuffers(struct > > >>> > apertures_struct *a, > > >>> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? "%s vs %s - removing generic driver\n", > > >>> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? name, registered_fb[i]->fix.id); > > >>> > ? ? ? ? ? ? ? ? ? ? ? ?unregister_framebuffer(registered_fb[i]); > > >>> > + ? ? ? ? ? ? ? ? ? ? ? registered_fb[i] = NULL; > > >>> > > > >>> > Tested the patch, and now I get this: > > >>> > dmesg: http://pastebin.com/ieMNrA7C > > >>> > > > >>> > [ ? 12.252328] BUG: unable to handle kernel NULL pointer dereference > > >>> > at 00000000000003b8 > > >>> > [ ? 12.252342] IP: [] fb_mmap+0x58/0x1d0 > > >>> > > >>> Ok, goodie. > > >>> > > >>> Or not so goodie, but it does make it clear that yeah, the fb code > > >>> seems to be using stale pointers from that registered_fb[] array, and > > >>> the whole unregistration process is just racing with people using it. > > >>> > > >>> Herton had that much bigger patch, can you test it? > > >> > > >> I think Andy's patch worked, not sure why it fell between the cracks, > > >> either didn't appear on lkml or in my inbox at all. > > >> > > >> if we can get Herton to repost it properly + a tested by I'm happy for > > >> it to go in. > > >> > > >> Dave. > > >> > > >> > > > > > > Tested Andy's patch and it works ! > > > http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-natty.git;a=commit;h=c5a742b5f78e161d6a13853a7e3e6e1dfa429e69 > > > > > > Tested-by: Anca Emanuel > > > > > > > link to patch: http://is.gd/otIfGc > > Adding Andy on CC (btw he is away for today, may get some time to answer). > > Andy, can you repost the patch? > This is the first I've seen the patch as well, but fortunately patchwork caught it on the Cc. There's also an outstanding patch for fixing an AB-BA deadlock between the fb_info lock and the console lock which this will clash with. I'm happy to rework that patch on top of Andy's patch for Anca and/or Herton to test, though. I'll need to do some more testing locally as well.. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/