From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753071AbXGHXDa (ORCPT ); Sun, 8 Jul 2007 19:03:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756845AbXGHXDM (ORCPT ); Sun, 8 Jul 2007 19:03:12 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:32956 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752154AbXGHXDL (ORCPT ); Sun, 8 Jul 2007 19:03:11 -0400 Date: Mon, 9 Jul 2007 01:03:00 +0200 From: Pavel Machek To: "Rafael J. Wysocki" Cc: Benjamin Herrenschmidt , Alan Stern , Kyle Moffett , Nigel Cunningham , Matthew Garrett , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, Miklos Szeredi Subject: Re: hibernation/snapshot design [was Re: [PATCH] Remove process freezer from suspend to RAM pathway] Message-ID: <20070708230300.GI5401@elf.ucw.cz> References: <1183931688.3388.316.camel@localhost.localdomain> <20070708221315.GF5401@elf.ucw.cz> <200707090101.28832.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200707090101.28832.rjw@sisk.pl> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > Freezer is not needed for snapshot -- it is needed so that we can > > write out the snapshot to disk without the need for special > > drivers/block/simple-ide-for-suspend.c. (We are doing snapshot, then > > write to disk from userland code in uswsusp). > > Yes. > > BTW, this patch: > > http://www.sisk.pl/kernel/hibernation_and_suspend/2.6.22-rc7/patches/15-freezer-make-kernel-threads-nonfreezable-by-default.patch > > that's queued up in -mm contains a freezer documentation update, in which the > reasons of using it, as well as its limitations, are described. > > To summarize what was previously said in this thread: > > * Apparently, we agree that the freezer is _generally_ not needed for suspend > (ie. any transition to a system sleep state other than hibernation), but some > of us (eg. me) think that it wouldn't be reasonable to drop the freezer from > the suspend code path _right_ _now_ . > > * Some of us, including you, Nigel and me, think that the freezer is needed > for hibernation (please see the document in the patch above for details). > In the (very) long run this might be avoided too, but (IMO) certainly not at > this point. > > * We seem to agree that in order to remove the freezer from the suspend code > path some work needs to be done on device drivers, driver midlayers and the > PM core. We also need to do some work on the PM core in order to introduce > a separate hibernation framework and IMO it would be reasonable to > synchronize these efforts. > > * We are now to decide what to do so that the freezer can be safely removed > from the suspend code path and how to integrate that change with the > hibernation code path (if possible and reasonable). Nice summary, thanks. > * The freezer vs FUSE issue that started this thread remains unresolved, so > it would be desirable to provide a short-term fix (need not be very nice). Actually there are _2_ freezer vs FUSE issues, and one of them should be simple to solve, once we have sysrq-t of the deadlock. (Or did I miss it somewhere with discussion going on 10 lists in parallel?) Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html