From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992989AbXDDQdi (ORCPT ); Wed, 4 Apr 2007 12:33:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2992992AbXDDQdi (ORCPT ); Wed, 4 Apr 2007 12:33:38 -0400 Received: from smtp105.sbc.mail.mud.yahoo.com ([68.142.198.204]:37088 "HELO smtp105.sbc.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S2992989AbXDDQdg (ORCPT ); Wed, 4 Apr 2007 12:33:36 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=pacbell.net; h=Received:X-YMail-OSG:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=YFxlzx9AmiildxHj6Iv2UEuloz56bEhdvJhjNWGP1+rttxS0z2So38mMMADsYzDtojhc3kPFD9tkAVBJOCd+KfsZZEzxqJM8+Io7ylRHoTeTt71Y/1DrZ07S7Dd2S2qjrx8Qvx2D98q+4UDB8I/WicrNdcrB6KQEwReHJ4SSL7Y= ; X-YMail-OSG: OBiEEFAVM1kRb3dlzS94dBBX7e3_t6_ls1y.i5TM1UKrBflxCcYyUeWPH4o3QmRkelg6D2G3Ow-- From: David Brownell To: Alan Stern Subject: Re: [linux-pm] [PATCH v2] Add suspend/resume for HPET Date: Wed, 4 Apr 2007 08:06:05 -0700 User-Agent: KMail/1.7.1 Cc: Maxim Levitsky , Ingo Molnar , Linus Torvalds , Greg KH , Thomas Gleixner , Kernel development list , Linux-pm mailing list References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704040806.06367.david-b@pacbell.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 02 April 2007 1:04 pm, Alan Stern wrote: > On Mon, 2 Apr 2007, David Brownell wrote: > > This is the kind of thing that the pm_parent relationship was (AFAICT) > > originally supposed to handle. Of course, it doesn't/can't, given the > > current implementation ... that relationship is never used. > > Just so. In fact, there almost certainly are other dependencies that > nobody is aware of, simply because they have never had a chance to bite. In any given system, yes there are bugs lurking. But I was more concerned with a provably wrong assumption made by the current framework. Such things cause cascading fragility. As Thomas mentioned, HPET isn't the only place where a "linear" model fails. > Such things can be rather difficult to pin down when they occur. I would > be happy enough to leave matters as they are, with a strict LIFO approach. I wouldn't. Much better to have a solid handle on the interdependencies than to need to cope, long term, with a framework that doesn't allow that. Remember also that a LIFO model assumes that there's only one sequence by which the hardware powers up/down ... i.e. that there's no runtime PM going on, whereby large chunks are regularly powered down/up based on usage. Better runtime PM becomes more important as system complexity rises. - Dave