From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754778AbdJIN6I (ORCPT ); Mon, 9 Oct 2017 09:58:08 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41890 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754217AbdJIMo6 (ORCPT ); Mon, 9 Oct 2017 08:44:58 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Mike Galbraith" , "Thomas Gleixner" , "Peter Zijlstra" , "Linus Torvalds" , "Ingo Molnar" Date: Mon, 09 Oct 2017 13:44:24 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 004/192] sched/topology: Fix building of overlapping sched-groups In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.49-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 0372dd2736e02672ac6e189c31f7d8c02ad543cd upstream. When building the overlapping groups, we very obviously should start with the previous domain of _this_ @cpu, not CPU-0. This can be readily demonstrated with a topology like: node 0 1 2 3 0: 10 20 30 20 1: 20 10 20 30 2: 30 20 10 20 3: 20 30 20 10 Where (for example) CPU1 ends up generating the following nonsensical groups: [] CPU1 attaching sched-domain: [] domain 0: span 0-2 level NUMA [] groups: 1 2 0 [] domain 1: span 0-3 level NUMA [] groups: 1-3 (cpu_capacity = 3072) 0-1,3 (cpu_capacity = 3072) Where the fact that domain 1 doesn't include a group with span 0-2 is the obvious fail. With patch this looks like: [] CPU1 attaching sched-domain: [] domain 0: span 0-2 level NUMA [] groups: 1 0 2 [] domain 1: span 0-3 level NUMA [] groups: 0-2 (cpu_capacity = 3072) 0,2-3 (cpu_capacity = 3072) Debugged-by: Lauro Ramos Venancio Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Fixes: e3589f6c81e4 ("sched: Allow for overlapping sched_domain spans") Signed-off-by: Ingo Molnar [bwh: Backported to 3.16: adjust filename] Signed-off-by: Ben Hutchings --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5854,7 +5854,7 @@ build_overlap_sched_groups(struct sched_ cpumask_clear(covered); - for_each_cpu(i, span) { + for_each_cpu_wrap(i, span, cpu) { struct cpumask *sg_span; if (cpumask_test_cpu(i, covered))