Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754997Ab1EYTEr (ORCPT ); Wed, 25 May 2011 15:04:47 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:55717 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753144Ab1EYTEq convert rfc822-to-8bit (ORCPT ); Wed, 25 May 2011 15:04:46 -0400 MIME-Version: 1.0 In-Reply-To: <20110525205707.12abc68c@neptune.home> References: <1306266871-12464-1-git-send-email-lxnay@sabayon.org> <20110524224545.08c53b1d@neptune.home> <20110525181917.12cf97b8@neptune.home> <20110525204648.58983270@neptune.home> <20110525205707.12abc68c@neptune.home> Date: Wed, 25 May 2011 21:04:45 +0200 X-Google-Sender-Auth: AjDD1fQ2SEB6Gol2zEVbsmKY35U Message-ID: Subject: Re: [PATCH] fbmem: fix race condition between register_framebuffer() and fb_open() From: Fabio Erculiani To: =?UTF-8?Q?Bruno_Pr=C3=A9mont?= Cc: linux-fbdev@vger.kernel.org, lethal@linux-sh.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2462 Lines: 63 On Wed, May 25, 2011 at 8:57 PM, Bruno Prémont wrote: > On Wed, 25 May 2011 Fabio Erculiani wrote: >> On Wed, May 25, 2011 at 8:46 PM, Bruno Prémont wrote: >> > On Wed, 25 May 2011 Fabio Erculiani wrote: >> >> I'm not a fbdev expert. So I leave the real fix to real men ( ;-) ). >> >> It is causing deadlock during boot, so I would consider it quite critical. >> >> Users using any fb driver will get into troubles. >> >> The workaround is to boot with vga=normal. >> > >> > What is your system doing during boot? I've never seen it here but maybe >> > my boot sequence is too simple. >> >> I'm using vesafb and vga=791. It is quite simple to reproduce. >> Also see: http://bugs.gentoo.org/show_bug.cgi?id=368109 > > Looks like gentoo kernel, might be splash is related to the hang Then, if you say so, it must be the fbsplash patch for sure, I keep forgetting of that :-/ > >> > Could you tell if it deadlocks before init gets started or afterwards, >> > which fb drivers (and extra kernel patches if any) are in use. >> >> Exactly when register_framebuffer() is called, in my case, early in >> the boot phase, before init. >> >> > >> > If you have the complete backtrace of the deadlocked processes it would >> > help getting a better idea of what is affected and how (and why just the >> > framebuffer's lock is not causing trouble with earlier kernel versions). >> >> Because that code got a HUGE rewrite in the latest cycle, where >> registration_lock has been introduce. >> Just make a diff between 2.6.38 and 2.6.39. It will be easy to see >> that SO MANY lines have changed ;-) >> Anyway, since I'm out of office these days, I won't be able to send >> you the traceback this week, but since so many people have run into >> it, I guess it's fairly simple to reproduce. > > Rewrite was not so huge, and I'm not affected here (running with KMS > compiled in though and vanilla kernel). > Probably the cause is related to one of the extra patches provided by > Gentoo and subscribing to framebuffer registration notifications. > > Will have a look. Thanks a lot, let me know if I can help out next week. > > Bruno > -- Fabio Erculiani -- 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/