Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763470AbYHEUEb (ORCPT ); Tue, 5 Aug 2008 16:04:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762167AbYHEUEM (ORCPT ); Tue, 5 Aug 2008 16:04:12 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:51471 "EHLO gprs189-60.eurotel.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762120AbYHEUEL (ORCPT ); Tue, 5 Aug 2008 16:04:11 -0400 Date: Tue, 5 Aug 2008 21:57:06 +0200 From: Pavel Machek To: Oleg Nesterov Cc: Zhang Rui , Gautham R Shenoy , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, harbour@sfinx.od.ua, rjw@sisk.pl Subject: Re: + pm-introduce-new-interfaces-schedule_work_on-and-queue_work_on.patch added to -mm tree Message-ID: <20080805195706.GD7939@elf.ucw.cz> References: <200807111846.m6BIkeTj031024@imap1.linux-foundation.org> <20080712162149.GD603@tv-sign.ru> <20080722161900.GA17601@in.ibm.com> <20080724124349.GA182@tv-sign.ru> <1216948649.2669.21.camel@rzhang-dt> <20080725094246.GA110@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080725094246.GA110@tv-sign.ru> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1759 Lines: 55 Hi! > > > This means that > > > > > > pm-schedule-sysrq-poweroff-on-boot-cpu.patch > > > > > > is not 100% right. It is still possible to hang/deadlock if we race > > > with cpu_down(first_cpu(cpu_online_map)). > > > > Yes, you're right. > > But then should we fix disable_nonboot_cpus as well? > > > > int disable_nonboot_cpus(void) > > { > > first_cpu = first_cpu(cpu_online_map); > > ... > > > > for_each_online_cpu(cpu) { > > if (cpu == first_cpu) > > continue; > > error = _cpu_down(cpu, 1); > > ... > > } > > ... > > } > > Note that disable_nonboot_cpus() does first_cpu = first_cpu() under > cpu_maps_update_begin(), so we can't race with cpu-hotplug. > > However, this afaics means that its name is wrong, and > printk("Disabling non-boot CPUs ...\n") is not right too. > What it does is disable_all_but_one_cpus(). I thought that first cpu is defined to be boot cpu? > And, it is not clear why disable_nonboot_cpus() assumes that > all but first_cpu(cpu_online_map) must have .hotpluggable == 1. Where does it assume that? It will fail if some CPUs can't be unplugged, and I'm afraid suspend can't work in such case... > And, if one of the callers really need to preserve the boot CPU, > I don't understand how it is guaranteed it must be first_cpu(). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/