From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759413Ab3JOSZI (ORCPT ); Tue, 15 Oct 2013 14:25:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31524 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751804Ab3JOSZG (ORCPT ); Tue, 15 Oct 2013 14:25:06 -0400 From: Jeff Moyer To: Jens Axboe Cc: linux-kernel@vger.kernel.org Subject: Re: blk_mq_update_queue_map makes an (invalid?) assumption about cpu ordering References: <20131015181403.GY541@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Tue, 15 Oct 2013 14:25:00 -0400 In-Reply-To: <20131015181403.GY541@kernel.dk> (Jens Axboe's message of "Tue, 15 Oct 2013 12:14:03 -0600") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: >> This assumes that the first_sibling is listed before any other siblings, >> which I don't believe is true. I don't think you get any guaranteed >> ordering in that cpu_possible_mask. >> >> ... or did I miss something? > > That's correct, it's assuming the first sibling is the lowest numbered > one. Are there cases where that would not be correct? I was sort of > assuming that was what "first" meant here. Yeah, you're right. I hadn't read down the call chain: static int get_first_sibling(unsigned int cpu) ret = cpumask_first(topology_thread_cpumask(cpu)); Nothing to see here, move along... -Jeff