From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263133AbTJJSPe (ORCPT ); Fri, 10 Oct 2003 14:15:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263131AbTJJSPe (ORCPT ); Fri, 10 Oct 2003 14:15:34 -0400 Received: from hockin.org ([66.35.79.110]:22027 "EHLO www.hockin.org") by vger.kernel.org with ESMTP id S263133AbTJJSPc (ORCPT ); Fri, 10 Oct 2003 14:15:32 -0400 Date: Fri, 10 Oct 2003 11:03:20 -0700 From: Tim Hockin To: William Lee Irwin III , 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: <20031010180320.GA1995@hockin.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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031010144723.GC727@holomorphy.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 10, 2003 at 07:47:23AM -0700, William Lee Irwin III wrote: > You need at least enough warning to get out of critical sections (e.g. > holding a spinlock) and dump registers out to memory. i.e. as long as it > takes to schedule out whatever's currently running on the thing. I've got a patch against RedHat's 2.4.x kernel with some version of O(1) scheduler that migrates all processes off a CPU and makes it ineleigible to run new tasks. When the syscall returns, it is safe to remove the CPU. Processes that are running or sleeping and can be migrated elsewhere are migrated. Running processes that have set_cpus_allowed to ONLY the processor in question are marked TASK_UNRUNNABLE and moved off the runqueue. Sleeping processes that have set_cpus_allowed to ONLY the processor in question are left unmolested until they wake up, at which point they will be marked UNRUNNABLE. It was done to allow software to bring CPUs on/offline, but it should work for this. IRQs not done yet, either. -- Notice that as computers are becoming easier and easier to use, suddenly there's a big market for "Dummies" books. Cause and effect, or merely an ironic juxtaposition of unrelated facts?