Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757457AbZLFCFR (ORCPT ); Sat, 5 Dec 2009 21:05:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752870AbZLFCFN (ORCPT ); Sat, 5 Dec 2009 21:05:13 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:33117 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752811AbZLFCFM (ORCPT ); Sat, 5 Dec 2009 21:05:12 -0500 Date: Sat, 5 Dec 2009 18:05:14 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: "Rafael J. Wysocki" cc: LKML , ACPI Devel Maling List , pm list , Alan Stern Subject: Re: [GIT PULL] PM updates for 2.6.33 In-Reply-To: <200912060254.10081.rjw@sisk.pl> Message-ID: References: <200912052216.19540.rjw@sisk.pl> <200912060055.36130.rjw@sisk.pl> <200912060254.10081.rjw@sisk.pl> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2096 Lines: 49 On Sun, 6 Dec 2009, Rafael J. Wysocki wrote: > > While the current settings are probably unsafe (like enabling PCI devices > to be suspended asynchronously by default if there are not any direct > dependences between them), there are provisions to make eveything safe, if > we have enough information (which also is needed to put the required logic into > the drivers). I disagree. Think of a situation that we already handle pretty poorly: USB mass storage devices over a suspend/resume. > The device tree represents a good deal of the dependences > between devices and the other dependences may be represented as PM links > enforcing specific ordering of the PM callbacks. The device tree means nothing at all, because it may need to be entirely rebuilt at resume time. Optimally, what we _should_ be doing (and aren't) for suspend/resume of USB is to just tear down the whole topology and rebuild it and re-connect the things like mass storage devices. IOW, there would be no device tree to describe the topology, because we're finding it anew. And it's one of the things we _would_ want to do asynchronously with other things. We don't want to build up some irrelevant PM links and callbacks. We don't want to have some completely made-up new infrastructure for something that we _already_ want to handle totally differently for init time. IOW, I argue very strongly against making up something PM-specific, when there really doesn't seem to be much of an advantage. We're much better off trying to share the init code than making up something new. > I'd say if there's a worry that the same register may be accessed concurrently > from two different code paths, there should be some locking in place. Yeah. And I wish ACPI didn't exist at all. We don't know. And we want to _limit_ our exposure to these things. Linus -- 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/