From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263079AbUCaAhg (ORCPT ); Tue, 30 Mar 2004 19:37:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263083AbUCaAhd (ORCPT ); Tue, 30 Mar 2004 19:37:33 -0500 Received: from fw.osdl.org ([65.172.181.6]:36488 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S263079AbUCaAhX (ORCPT ); Tue, 30 Mar 2004 19:37:23 -0500 Date: Tue, 30 Mar 2004 16:39:28 -0800 From: Andrew Morton To: "Martin J. Bligh" Cc: rddunlap@osdl.org, hari@in.ibm.com, linux-kernel@vger.kernel.org, apw@shadowen.org Subject: Re: BUG_ON(!cpus_equal(cpumask, tmp)); Message-Id: <20040330163928.7cafae3d.akpm@osdl.org> In-Reply-To: <187940000.1080692555@flay> References: <006701c415a4$01df0770$d100000a@sbs2003.local> <20040329162123.4c57734d.akpm@osdl.org> <20040329162555.4227bc88.akpm@osdl.org> <20040330132832.GA5552@in.ibm.com> <20040330151729.1bd0c5d0.rddunlap@osdl.org> <187940000.1080692555@flay> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Martin J. Bligh" wrote: > > > I'll just say that kexec fails without this patch and works with > > it applied, so I'd like to see it merged. If this patch isn't > > acceptable, let's find out why and try to make one that is. > > > > Thanks for the patch, Hari. > > >From discussions with Andy, it seems this still has the same race as before > just smaller. I don't see how we can fix this properly without having some > locking on cpu_online_map .... probably RCU as it's massively read-biased > and we don't want to pay a spinlock cost to read it. We do want to avoid adding stuff to the IPI path. If the going-away CPU still responds to IPIs after it has gone away then do we actually need to do anything? For x86, at least?