From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759412Ab3BJSzJ (ORCPT ); Sun, 10 Feb 2013 13:55:09 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:44888 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756010Ab3BJSzH (ORCPT ); Sun, 10 Feb 2013 13:55:07 -0500 Date: Sun, 10 Feb 2013 19:55:05 +0100 From: Pavel Machek To: "Rafael J. Wysocki" Cc: Miklos Szeredi , Goswin von Brederlow , Li Fei , len.brown@intel.com, mingo@redhat.com, peterz@infradead.org, biao.wang@intel.com, linux-pm@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, chuansheng.liu@intel.com Subject: Re: Getting rid of freezer for suspend [was Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads] Message-ID: <20130210185504.GA17268@amd.pavel.ucw.cz> References: <1360113112.17267.1.camel@fli24-HP-Compaq-8100-Elite-CMT-PC> <20130210103344.GA8888@amd.pavel.ucw.cz> <3538583.NDAkGLdQOZ@vostro.rjw.lan> <3938124.8eafYb16IB@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3938124.8eafYb16IB@vostro.rjw.lan> 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 Hi! > > > > The whole memory shrinking we do for hibernation is now done by allocating > > > > memory, so the freezer is not necessary for *that* and there's *zero* > > > > difference between suspend and hibernation with respect to why the freezer is > > > > used. > > > > > > Funny. Freezer was put there so that hibernation image was safe to > > > write out. You need disk subsystems in workable state for hibernation. > > > > I'm not really sure what you're talking about. Why do you think the freezer is > > necessary for that? Well, from freezer you need: 1) user process frozen. 2) essential locks _not_ held so that block devices are still functional. > > > mmap... what is problem with mmap? For suspend, memory is powered, so > > > you can permit people changing it. > > > > Suppose mmap is used to make the registers of some device available to user > > space. Yes, that can happen. "Don't do it, then". Yes, can happen, but hopefully is not too common these days. [And... freezer doing 1) but not 2) would be enough to handle that. Freezer doing 1) but not 2) would also be simpler...] > > Again, I'm not sure what you're talking about. Once the image has been > > created, it can be saved while user space is running just fine. > > Of course, we don't want random changes to be made to persistent storage after > the image has been created, because those changes might not be consistent with > the memory contents stored in the image, and that's why user space is still > frozen when we're saving the image. Yes. That's the reason 1) for freezer. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html