From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: [PATCH] - race-free suspend. Was: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Date: Thu, 3 Jun 2010 16:33:07 +1000 Message-ID: <20100603163307.721b1c23@notabene.brown> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: 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 In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org 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 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 Hj=C3=B8nnev=C3=A5g 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. =C2=A0This may involve: > >> > =C2=A0- 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. =C2=A0Are you saying tha= t you are not > > open to any significant change in the Android user-space code? =C2=A0= That would > > make the situation a lot harder to resolve. >=20 > 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 cou= ld be used. There were two other examples. However one process would need to know about any wakeup event that happ= ens. I don't think that needs to be a significant bottleneck, but I don't re= ally know enough about all the requirement to try devising a demonstration. >=20 > 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 thin= k > bottlenecking events through a central daemon would represent a step > backwards. I guess it becomes an question of economics for you then. Does the cos= t of whatever user-space changes are required exceed the value of using an u= pstream 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-omap" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html