From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753751Ab0ERWz3 (ORCPT ); Tue, 18 May 2010 18:55:29 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:43832 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752256Ab0ERWz2 convert rfc822-to-8bit (ORCPT ); Tue, 18 May 2010 18:55:28 -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 00:56:36 +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> <201005182314.08761.rjw@sisk.pl> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Message-Id: <201005190056.36804.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 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. Rafael