From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753497AbbDADCs (ORCPT ); Tue, 31 Mar 2015 23:02:48 -0400 Received: from mail-qc0-f180.google.com ([209.85.216.180]:35448 "EHLO mail-qc0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751097AbbDADCp (ORCPT ); Tue, 31 Mar 2015 23:02:45 -0400 Date: Tue, 31 Mar 2015 23:02:42 -0400 From: Tejun Heo To: Kamezawa Hiroyuki Cc: Gu Zheng , linux-kernel@vger.kernel.org, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, tangchen@cn.fujitsu.com, izumi.taku@jp.fujitsu.com Subject: Re: [PATCH 0/2] workqueue: fix a bug when numa mapping is changed Message-ID: <20150401030242.GL9974@htj.duckdns.org> References: <1427336275-32066-1-git-send-email-guz.fnst@cn.fujitsu.com> <55137935.5080301@jp.fujitsu.com> <55139340.8070201@cn.fujitsu.com> <20150326151850.GD1953@htj.duckdns.org> <551436F2.5020804@jp.fujitsu.com> <55191C3D.8070800@cn.fujitsu.com> <551A3A01.7030707@jp.fujitsu.com> <20150331152822.GE9974@htj.duckdns.org> <551B5E0F.1020302@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <551B5E0F.1020302@jp.fujitsu.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 01, 2015 at 11:55:11AM +0900, Kamezawa Hiroyuki wrote: > Now, hot-added cpus will have the lowest free cpu id. > > Because of this, in most of systems which has only cpu-hot-add, cpu-ids are always > contiguous even after cpu hot add. > In enterprise, this would be considered as imcompatibility. > > determining cpuid <-> lapicid at boot will make cpuids sparse. That may corrupt > exisiting script or configuration/resource management software. Ugh... so, cpu number allocation on hot-add is part of userland interface that we're locked into? Tying hotplug and id allocation order together usually isn't a good idea. What if the cpu up fails while running the notifiers? The ID is already allocated and the next cpu being brought up will be after a hole anyway. Is this even actually gonna affect userland? -- tejun