From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754628Ab0ESUjT (ORCPT ); Wed, 19 May 2010 16:39:19 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:48470 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754069Ab0ESUjS convert rfc822-to-8bit (ORCPT ); Wed, 19 May 2010 16:39:18 -0400 From: "Rafael J. Wysocki" To: Arve =?iso-8859-1?q?Hj=F8nnev=E5g?= Subject: Re: [PATCH 0/8] Suspend block api (version 7) Date: Wed, 19 May 2010 22:40:39 +0200 User-Agent: KMail/1.12.4 (Linux/2.6.34-rjw; KDE/4.3.5; x86_64; ; ) Cc: Brian Swetland , linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1273810273-3039-1-git-send-email-arve@android.com> <201005190056.36804.rjw@sisk.pl> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Message-Id: <201005192240.39803.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 19 May 2010, Arve Hjønnevåg wrote: > 2010/5/18 Rafael J. Wysocki : > > On Wednesday 19 May 2010, Arve Hjønnevåg wrote: > >> 2010/5/18 Rafael J. Wysocki : > >> > On Tuesday 18 May 2010, Arve Hjønnevåg wrote: > >> >> 2010/5/18 Rafael J. Wysocki : > >> >> > On Tuesday 18 May 2010, Arve Hjønnevåg wrote: > >> >> >> On Mon, May 17, 2010 at 2:44 PM, Rafael J. Wysocki wrote: > >> >> >> > On Monday 17 May 2010, Brian Swetland wrote: > >> >> >> >> On Mon, May 17, 2010 at 1:40 PM, Rafael J. Wysocki wrote: > >> >> >> >> > On Monday 17 May 2010, Arve Hjønnevåg wrote: > >> >> >> >> >> > >> > ... > >> >> > >> >> > Now, to make it more "user-friendly", we can simply use > >> >> > queue_delayed_work() with a reasonable delay instead of queue_work() to queue > >> >> > the suspend work (the delay may be configurable via sysfs). > >> >> > > >> >> > >> >> I can add a delay (and the timeout support code does add a delay as an > >> >> optimization) to the unknown wakeup case, but this does not fix the > >> >> problem of a user turning on opportunistic suspend with a user space > >> >> framework that does not use suspend blockers. If the kernel uses > >> >> suspend blockers to make sure the wakeup event makes it to user space, > >> >> but user space does not block suspend, then the system will suspend > >> >> before the event is processed. > >> > > >> > But the user can still manually write to /sys/power/state. :-) > >> > > >> > >> Does adding or removing a delay change this? It seems in only changes > >> how quickly the user can finish that write. > > > > Yes, but that should allow the user to avoid rebooting the system if he does > > the "wrong thing". > > > >> I'm not convinced adding a configurable delay here is necessary. > > > > No, it's not, but it would be useful in some cases IMO. Pretty much the same > > way your debug features are useful. > > > >> Once the driver that enabled the wakeup event has been updated to block > >> suspend until this event gets to user space, then this delay will > >> never be triggered. The kernel cannot tell the difference between a > >> user enabling opportunistic suspend but not wanting it and > >> opportunistic suspend aware user space code deciding that this wakeup > >> event should be ignored. > > > > The point is, if there's a delay, it may be too aggressive for some users and > > too conservative for some other users, so it makes sense to provide a means > > to adjust it to the user's needs. > > > > My point is that the delay will not be used at all if the driver uses > a suspend blocker (like it should). Why add a configuration option for > opportunistic suspend that only works when the driver does not support > opportunistic suspend. Because on many systems there are no such drivers (yet, at least). Rafael