Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753819Ab0FIWEs (ORCPT ); Wed, 9 Jun 2010 18:04:48 -0400 Received: from cantor2.suse.de ([195.135.220.15]:53267 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751454Ab0FIWEr (ORCPT ); Wed, 9 Jun 2010 18:04:47 -0400 Date: Thu, 10 Jun 2010 08:04:25 +1000 From: Neil Brown To: "Rafael J. Wysocki" Cc: Felipe Contreras , Andrew Morton , Linus Torvalds , david@lang.hm, Florian Mickler , Vitaly Wool , Brian Swetland , Arve =?UTF-8?B?SGrDuG5uZXbDpWc=?= , Arjan van de Ven , tytso@mit.edu, Peter Zijlstra , "H. Peter Anvin" , LKML , James Bottomley , Alan Cox , Linux PM , Ingo Molnar , Linux OMAP Mailing List , Thomas Gleixner , Felipe Balbi Subject: Re: [linux-pm] suspend blockers & Android integration Message-ID: <20100610080425.6f005dbb@notabene.brown> In-Reply-To: <201006091140.28034.rjw@sisk.pl> References: <20100603193045.GA7188@elte.hu> <201006091140.28034.rjw@sisk.pl> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3843 Lines: 84 On Wed, 9 Jun 2010 11:40:27 +0200 "Rafael J. Wysocki" wrote: > On Wednesday 09 June 2010, Felipe Contreras wrote: > > On Wed, Jun 9, 2010 at 6:46 AM, Linus Torvalds > > wrote: > > > On Tue, 8 Jun 2010, david@lang.hm wrote: > > >> > > >> having suspend blockers inside the kernel adds significant complexity, it's > > >> worth it only if the complexity buys you enough. In this case the question is > > >> if the suspend blockers would extend the sleep time enough more to matter. As > > >> per my other e-mail, this is an area with rapidly diminishing returns as the > > >> sleep times get longer. > > > > > > Well, the counter-argument that nobody seems to have brought up is that > > > suspend blockers exist, are real code, and end up being shipped in a lot > > > of machines. > > > > > > That's a _big_ argument in favour of them. Certainly much bigger than > > > arguing against them based on some complexity-arguments for an alternative > > > that hasn't seen any testing at all. > > > > > > IOW, I would seriously hope that this discussion was more about real code > > > that _exists_ and does what people need. It seems to have degenerated into > > > something else. > > > > > > Because in the end, "code talks, bullshit walks". People can complain and > > > suggest alternatives all they want, but you can't just argue. At some > > > point you need to show the code that actually solves the problem. > > > > That's assuming there is an actual problem, which according to all the > > embedded people except android, there is not. > > Yes, there is, but they've decided to ignore it. > > > And if there is indeed such a problem (probably not big), it might be > > solved properly by the time suspend blockers are merged, or few > > releases after. > > Not quite. Have you followed all of the discussion, actually? > > > Whatever the solution (or workaround) is, it would be nice if it could > > be used by more than just android people, and it would also be nice to > > do it without introducing user-space API that *nobody* likes and might > > be quickly deprecated. > > I agree with Linus and I don't have that much of a problem with the API that > people seem to have. In fact the much-hated user space API is just a char > device driver with 3 ioctls (that can be extended in future if need be) and > the kernel API is acceptable to me. I think there is a little bit more to it than that. It seems there is a new ioctl for input/event devices to say "Any events queued here should be treated as wake-up events". There may be similar additions to other devices, but I know of no details. I wonder if we can get a complete statement of changes to the user-space API... > Yes, there is some overlap between it > and PM QoS, but IMhO that overlap may be reduced over time (eg. by > using PM QoS requirements to implement suspend blockers). > > To me, the question boils down to whether or not we're able to persuade the > Android people to use any other approach (eg. by demonstrating that something > else is actually better), because even if we invent a brilliant new approach, > but Android ends up using its old one anyway, the net result will be as though > we haven't done anything useful. Yes. There is no point unless we can meet somewhere in the middle. I think that would have to include a full suspend that freezes all processes. Solutions which reject that - while quite clever - would require too much change to Android user-space to be acceptable. NeilBrown > > Rafael -- 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/