From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932079AbXDPHBq (ORCPT ); Mon, 16 Apr 2007 03:01:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754009AbXDPHBq (ORCPT ); Mon, 16 Apr 2007 03:01:46 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:46330 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753640AbXDPHBp (ORCPT ); Mon, 16 Apr 2007 03:01:45 -0400 Date: Mon, 16 Apr 2007 09:01:32 +0200 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: <20070416070132.GB1783@elf.ucw.cz> References: <200704061732.32712.rjw@sisk.pl> <20070409140352.GB3864@ucw.cz> <200704091514.56167.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200704091514.56167.rjw@sisk.pl> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 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. > > Does it mean you think we should stick with the current approach and sort out > all issues as they show up, or should we go for not using the CPU hotplug for > suspending without implementing the 'cpu not there so simulate unplug' path > at all (eg. we can fail the resume instead)? I'd fix the current approach, but... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html