From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262860AbTJJO7Z (ORCPT ); Fri, 10 Oct 2003 10:59:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262865AbTJJO7Z (ORCPT ); Fri, 10 Oct 2003 10:59:25 -0400 Received: from holomorphy.com ([66.224.33.161]:15489 "EHLO holomorphy") by vger.kernel.org with ESMTP id S262860AbTJJO7X (ORCPT ); Fri, 10 Oct 2003 10:59:23 -0400 Date: Fri, 10 Oct 2003 08:01:22 -0700 From: William Lee Irwin III To: Mark Mielke Cc: G?bor L?n?rt , Stuart Longland , Stephan von Krawczynski , Fabian.Frederick@prov-liege.be, linux-kernel@vger.kernel.org Subject: Re: 2.7 thoughts Message-ID: <20031010150122.GD727@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Mark Mielke , G?bor L?n?rt , Stuart Longland , Stephan von Krawczynski , Fabian.Frederick@prov-liege.be, linux-kernel@vger.kernel.org References: <20031009115809.GE8370@vega.digitel2002.hu> <20031009165723.43ae9cb5.skraw@ithnet.com> <3F864F82.4050509@longlandclan.hopto.org> <20031010125137.4080a13b.skraw@ithnet.com> <3F86BD0E.4060607@longlandclan.hopto.org> <20031010143529.GT5112@vega.digitel2002.hu> <20031010144723.GC727@holomorphy.com> <20031010144837.GB12134@mark.mielke.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031010144837.GB12134@mark.mielke.cc> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 10, 2003 at 10:48:37AM -0400, Mark Mielke wrote: > Perhaps I've naive here, but - with hot-pluggable CPU machines, do you not > de-activate the CPU through software first, before pulling the CPU out, at > which point it is not in use? Well, you deleted my reply, but never mind that. This obviously can't work unless the kernel gets some kind of warning. Userspace and kernel register state, once lost that way, can't be recovered, and if tasks are automatically suspended (e.g. cpu dumps to somewhere and a miracle occurs), you'll deadlock if the kernel was in a non-preemptible critical section at the time. What I suspect to be the case is some kind of warning is given to the kernel, and it has to respond within a certain time. Apparently it succeeds most of the time despite my naysaying if this actually works. -- wli