Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762068Ab0HMTIU (ORCPT ); Fri, 13 Aug 2010 15:08:20 -0400 Received: from thunk.org ([69.25.196.29]:46260 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756540Ab0HMTIT (ORCPT ); Fri, 13 Aug 2010 15:08:19 -0400 Date: Fri, 13 Aug 2010 15:08:01 -0400 From: "Ted Ts'o" To: James Bottomley Cc: Felipe Contreras , paulmck@linux.vnet.ibm.com, david@lang.hm, peterz@infradead.org, Brian Swetland , linux-kernel@vger.kernel.org, galibert@pobox.com, florian@mickler.org, menage@google.com, linux-pm@lists.linux-foundation.org, swmike@swm.pp.se, tglx@linutronix.de, Alan Cox , arjan@infradead.org Subject: Re: [linux-pm] Attempted summary of suspend-blockers LKML thread, take three Message-ID: <20100813190801.GB26950@thunk.org> Mail-Followup-To: Ted Ts'o , James Bottomley , Felipe Contreras , paulmck@linux.vnet.ibm.com, david@lang.hm, peterz@infradead.org, Brian Swetland , linux-kernel@vger.kernel.org, galibert@pobox.com, florian@mickler.org, menage@google.com, linux-pm@lists.linux-foundation.org, swmike@swm.pp.se, tglx@linutronix.de, Alan Cox , arjan@infradead.org References:

<20100812174303.GD2524@linux.vnet.ibm.com> <20100813152254.GD2511@linux.vnet.ibm.com> <20100813155738.GA11507@isilmar-3.linta.de> <1281719489.8407.17.camel@mulgrave.site> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1281719489.8407.17.camel@mulgrave.site> User-Agent: Mutt/1.5.20 (2009-06-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2551 Lines: 48 On Fri, Aug 13, 2010 at 01:11:29PM -0400, James Bottomley wrote: > > The facts are that suspend blockers identifies a race within our suspend > to ram system that permeates from top to bottom (that's from server to > mobile). The problem is that resume events are racy with respect to > suspend and vice versa. This manifests itself most annoyingly on my > laptop in the "double suspend" case: where I suspend with a pending > suspend event, my laptop will resume and then immediately re-suspend > (leading me to kick myself and remind myself to check it stayed up > before pushing unsuspend and walking away). The other annoying case is > that if I accidentally close the lid before presenting, I have to wait > until the system is fully down before pressing resume. This is all true, but it's also only one aspect of the problem. I agree with you that this is the part of the problem which affects Linux at all scales, from Cloud servers in a data center that want to suspend themselves when there's no work to do (and then fail to respond to the WOL packet) to mobile platforms that are suspending much more frequently. However, it doesn't follow that this is the _only_ problem that the Android folks might be interested in solving. Opportunistic suspend is a different part of the problem space, which is generally believed by the Android developers as being far more efficient than a user-space suspend manager. Rafael has stated his complete unwillingness to deal with this part of the problem. OK, so that probably means that for Android, it will have to be an out-of-tree kernel patch. The question, then, is whether a solution which addresses the only part of the problem which Rafael is interested in dealing with at this point, is sufficient such that (a) the kernel-level opportunistic suspend can be done as an out-of-tree patch, while simultaneously (b) allowing device drivers for Android devices can utilize Rafael's interfaces to solve the race design bug currently found in our suspend subsystem, while (c) requiring minimal changes to the Android userspace, and (d) providing all of the statistics and debugging functionality required by the Android userspace. If we can engineer a solution which meets (a), (b), (c), and (d) above, then everyone will be happy. - Ted -- 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/