From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933489Ab0HEPFQ (ORCPT ); Thu, 5 Aug 2010 11:05:16 -0400 Received: from mail-px0-f174.google.com ([209.85.212.174]:51738 "EHLO mail-px0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933414Ab0HEPFK (ORCPT ); Thu, 5 Aug 2010 11:05:10 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=q8FO63FaW151aZPgwseDSfq6Am3i+UocP9d7UrIlncGbVVraLvbZMoxCrz2IUzVu2D zhaZiCHSTKlT4EilITkFvDuHTRJnJWmdMOAQDidjzXu3gQdrlEqVrhoOefThc1QR43zW c3SXsDKkwhIe9yhxO9aFvlLGbIP/JVqvkEVp4= Date: Thu, 5 Aug 2010 22:59:40 +0800 From: Yong Zhang To: Peter Zijlstra Cc: Dave Airlie , Ingo Molnar , Jesse Barnes , LKML , "David S. Miller" Subject: Re: lockdep and oops_in_progress Message-ID: <20100805145940.GA8685@zhy> Reply-To: Yong Zhang References: <1280995849.1923.1515.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1280995849.1923.1515.camel@laptop> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 05, 2010 at 10:10:49AM +0200, Peter Zijlstra wrote: > On Thu, 2010-08-05 at 16:21 +1000, Dave Airlie wrote: > > Hi guys, > > > > I was debugging a wierd issue with suspend/resume and fbcon/X with > > some recent work Jesse and myself did to try and make sure a pinned > > fbcon always gets the text on it with a panic or oops occurs. > > > > It does this by testing the oops_in_progress flag, however once any > > lockdep issue occurs it looks to me that we leave this flag set > > forever, in most places I can see in oops code etc they call > > bust_spinlocks(1) then bust_spinlocks(0) to balance the > > oops_in_progress value, but lockdep never seems to reset it. > > > > I'm wondering if there is an inherent reason for this or if I whip up > > a patch to reset once the lockdep is printed if this would cause any > > issues? > > That's debug_locks_off(), right? I don't think there's a particular > reason we keep it set, cleaning that up might take a bit of work but > shouldn't be too hard. commit e0fdace10e75dac67d906213b780ff1b1a4cc360 Author: David Miller Date: Fri Aug 1 01:11:22 2008 -0700 debug_locks: set oops_in_progress if we will log messages. Otherwise lock debugging messages on runqueue locks can deadlock the system due to the wakeups performed by printk(). Signed-off-by: David S. Miller Signed-off-by: Ingo Molnar Seems we can revert that commit now because of 'robustify printk'. Dave, what do you think about it? Thanks, Yong > > Ingo, do you remember anything about that?, I think that bit comes from > before my time. > -- > 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/