Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933300Ab0FCGdY (ORCPT ); Thu, 3 Jun 2010 02:33:24 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57624 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932279Ab0FCGdW convert rfc822-to-8bit (ORCPT ); Thu, 3 Jun 2010 02:33:22 -0400 Date: Thu, 3 Jun 2010 16:33:07 +1000 From: Neil Brown To: Brian Swetland Cc: Arve =?UTF-8?B?SGrDuG5uZXbDpWc=?= , Thomas Gleixner , "Rafael J. Wysocki" , Alan Stern , Felipe Balbi , Peter Zijlstra , "Paul@smtp1.linux-foundation.org" , LKML , Florian Mickler , Linux OMAP Mailing List , Linux PM , Alan Cox , James Bottomley Subject: Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Message-ID: <20100603163307.721b1c23@notabene.brown> In-Reply-To: References: <201006010005.19554.rjw@sisk.pl> <20100601090023.788cabf4@notabene.brown> <201006010232.20263.rjw@sisk.pl> <20100601113309.609349fd@notabene.brown> <20100601122012.1edeaf48@notabene.brown> <20100602153235.340a7852@notabene.brown> <20100602180614.729246ea@notabene.brown> 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=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2489 Lines: 50 On Wed, 2 Jun 2010 11:05:18 -0700 Brian Swetland wrote: > On Wed, Jun 2, 2010 at 1:06 AM, Neil Brown wrote: > > On Wed, 2 Jun 2010 00:05:14 -0700 > > Arve Hjønnevåg wrote: > >> > The user-space suspend daemon avoids losing wake-events by using > >> > fcntl(F_OWNER) to ensure it gets a signal whenever any important wake-event > >> > is ready to be read by user-space.  This may involve: > >> >  - the one daemon processing all wake events > >> > >> Wake up events are not all processed by one daemon. > > > > Not with your current user-space code, no.  Are you saying that you are not > > open to any significant change in the Android user-space code?  That would > > make the situation a lot harder to resolve. > > There are many wakeup events possible in a typical system -- > keypresses or other input events, network traffic, telephony events, > media events (fill audio buffer, fill video decoder buffer, etc), and > I think requiring that all wakeup event processing bottleneck through > a single userspace process is non-optimal here. Just to be clear: I'm not suggesting all wake-events need to go through one process. That was just one example of how the interface I proposed could be used. There were two other examples. However one process would need to know about any wakeup event that happens. I don't think that needs to be a significant bottleneck, but I don't really know enough about all the requirement to try devising a demonstration. > > The current suspend-blocker proposal already involves userspace > changes (it's different than our existing wakelock interface), and > we're certainly not opposed to any/all userspace changes on principle, > but on the other hand we're not interested in significant reworks of > userspace unless they actually improve the situation somehow. I think > bottlenecking events through a central daemon would represent a step > backwards. I guess it becomes an question of economics for you then. Does the cost of whatever user-space changes are required exceed the value of using an upstream kernel? Both the cost and the value would be very hard to estimate in advance. I don't envy you the decision... NeilBrown -- 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/