From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] add mutex to fbdev for fb_mmap locking Date: Mon, 1 Jun 2009 22:45:51 +0200 Message-ID: <20090601204551.GA2702@elte.hu> References: <200905282134.n4SLYNwv027999@imap1.linux-foundation.org> <20090530121128.5f04179d.krzysztof.h1@poczta.fm> <20090531162453.dff458cb.krzysztof.h1@poczta.fm> <20090601222413.c2b57c9f.krzysztof.h1@poczta.fm> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sfi-mx-4.v28.ch3.sourceforge.com ([172.29.28.124] helo=mx.sourceforge.net) by 3yr0jf1.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1MBEOj-0001eO-1S for linux-fbdev-devel@lists.sourceforge.net; Mon, 01 Jun 2009 20:46:21 +0000 Received: from mx3.mail.elte.hu ([157.181.1.138]) by 1b2kzd1.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.69) id 1MBEOg-0000Q9-MD for linux-fbdev-devel@lists.sourceforge.net; Mon, 01 Jun 2009 20:46:21 +0000 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: Linus Torvalds Cc: krzysztof.h1@wp.pl, Linux-fbdev-devel , Peter Zijlstra , geert@linux-m68k.org, akpm@linux-foundation.org, righi.andrea@gmail.com * Linus Torvalds wrote: > On Mon, 1 Jun 2009, Krzysztof Helt wrote: > > > > I will fix it. > > Thanks. > > > If the revert to BKL is rejected this patch may wait till > > 2.6.31. > > Ahh, so this one helps clean up locking, but doesn't fix any > actual regressions? I was going to ask you about that. > > Btw - one thing you could try on the whole lockdep front - and I > realize that this is a _total_ hack - is to try the patch below. One thing that might be less obscure is to add: lockdep_off(); ... lockdep_on(); to around those user-copies. Those cause lockdep to totally ignore those dependencies. It's an ugly hack - but at least a readable hack IMO. With big red warning signs, a promise to fix this ASAP, etc. It's still much better than a big ugly revert back to the BKL (of course - and regardless of how late we are in the cycle) - and probably a bit better than the atomic-copy hack. Or am i missing something? Ingo ------------------------------------------------------------------------------ OpenSolaris 2009.06 is a cutting edge operating system for enterprises looking to deploy the next generation of Solaris that includes the latest innovations from Sun and the OpenSource community. Download a copy and enjoy capabilities such as Networking, Storage and Virtualization. Go to: http://p.sf.net/sfu/opensolaris-get