From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761709AbXGCVZz (ORCPT ); Tue, 3 Jul 2007 17:25:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758400AbXGCVZd (ORCPT ); Tue, 3 Jul 2007 17:25:33 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:46533 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757998AbXGCVZb (ORCPT ); Tue, 3 Jul 2007 17:25:31 -0400 From: "Rafael J. Wysocki" To: Benjamin Herrenschmidt Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Tue, 3 Jul 2007 23:32:48 +0200 User-Agent: KMail/1.9.5 Cc: Nigel Cunningham , Matthew Garrett , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, Alan Stern , Pavel Machek References: <20070703042916.GA17240@srcf.ucam.org> <200707031456.40890.rjw@sisk.pl> <1183497290.3388.4.camel@localhost.localdomain> In-Reply-To: <1183497290.3388.4.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707032332.49694.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, 3 July 2007 23:14, Benjamin Herrenschmidt wrote: > > > > - For STR, don't do the freezer thing. > > > > In the long run, I agree. > > > > Still, can you please read this post from Alan Stern: > > > > https://lists.linux-foundation.org/pipermail/linux-pm/2007-June/012847.html > > > > ? I don't think I'm able to repeat the arguments given in there in a > > convincing way. > > That's the same crackpot I've been hearing for the past 3 years or > so ... > > Both Paulus and I think the freezer is just a way to try to put your > head in the sand and ignore the problem. It causes as many problems as > it solves on its own, and is just not a solution that will be of any use > once you start implementing dynamic PM schemes etc... > > In many cases, having proper support for "live" suspend of devices is > just a matter of having a couple of helpers in whatever subsystem those > drivers hookup with. In the case of network, for example, it's mostly > trivial (stop the queue). For block, it's not terribly hard neither, > though you want to have some orderign/atomicity between the blocking of > the incoming request queue and the sending of things like spindown & > flush commands to the disk. For old-style IDE, that was fairly easily > solved by piping suspend/resume command down the request queue itself > and have the queue block/unblbock itself after processing them. Some of > that logic could maybe be moved to the block layer for all block drivers > to benefit. > > But yes, overall, there is work to do on drivers and I'm doing the ones > I hit on the platforms I use. I don't think the freezer is any kind of > remotely good solution, just a way to continue avoiding the problem. Still, do you really think that we're ready to drop it _right_ _now_ (I'm referring to suspend only) and if so than on what basis (except that you don't like it, which falls short of being a techical argument)? Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth