From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932129AbXDIMIk (ORCPT ); Mon, 9 Apr 2007 08:08:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753138AbXDIMIk (ORCPT ); Mon, 9 Apr 2007 08:08:40 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:4237 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753132AbXDIMIj (ORCPT ); Mon, 9 Apr 2007 08:08:39 -0400 Date: Mon, 9 Apr 2007 14:03:52 +0000 From: Pavel Machek To: "Rafael J. Wysocki" Cc: LKML , Andrew Morton , Gautham R Shenoy , Srivatsa Vaddagiri , "Eric W. Biederman" , Oleg Nesterov Subject: Re: [RFD] CPU hotplug and suspend Message-ID: <20070409140352.GB3864@ucw.cz> References: <200704061732.32712.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200704061732.32712.rjw@sisk.pl> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > Currently, we use the CPU hotplug to disable nonboot CPUs in the suspend code > paths, but with the recent change of code ordering (ie. nonboot CPUs are > disabled after freezing tasks _and_ devices) it has become quite troublesome. > The reason of this is that there are some CPU hotplug notifiers registered and > called on each run of cpu_up()/cpu_down() that assume the system to be fully > functional, which is not the case during the suspend. Moreover, at least some > of them do things that are not really necessary for disabling or enabling the > nonboot CPUs. Right. > The advantage of using the CPU hotplug (in its current form) for suspending is > that if some CPUs don't reappear during the resume, we are safe. Still, I > think it would be more appropriate, and simpler in the long run, to notify the > interested subsystems _only_ if one (or more) CPUs are not functional after the > resume. I'm afraid that adding 'cpu not there so simulate unplug' path will make it complex, and prone to failure, as _noone_ is going to test it. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html