From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751717AbdJELpt (ORCPT ); Thu, 5 Oct 2017 07:45:49 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:44028 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751540AbdJELpm (ORCPT ); Thu, 5 Oct 2017 07:45:42 -0400 From: Brendan Jackman To: linux-kernel@vger.kernel.org, Peter Zijlstra Cc: Dietmar Eggemann , Vincent Guittot , Josef Bacik , Ingo Molnar , Morten Rasmussen Subject: [PATCH RESEND v3 4/5] sched/fair: Fix use of find_idlest_group when no groups are allowed Date: Thu, 5 Oct 2017 12:45:15 +0100 Message-Id: <20171005114516.18617-5-brendan.jackman@arm.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20171005114516.18617-1-brendan.jackman@arm.com> References: <20171005114516.18617-1-brendan.jackman@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When p is allowed on none of the CPUs in the sched_domain, we currently return NULL from find_idlest_group, and pointlessly continue the search on lower sched_domain levels (where p is also not allowed) before returning prev_cpu regardless (as we have not updated new_cpu). Add an explicit check for this case, and a comment to find_idlest_group. Now when find_idlest_group returns NULL, it always means that the local group is allowed and idlest. Signed-off-by: Brendan Jackman Cc: Dietmar Eggemann Cc: Vincent Guittot Cc: Josef Bacik Cc: Ingo Molnar Cc: Morten Rasmussen Cc: Peter Zijlstra Reviewed-by: Vincent Guittot Reviewed-by: Josef Bacik --- kernel/sched/fair.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 933f5c9d95d1..4a14ebca4d79 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5768,6 +5768,8 @@ static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) /* * find_idlest_group finds and returns the least busy CPU group within the * domain. + * + * Assumes p is allowed on at least one CPU in sd. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, @@ -5955,6 +5957,9 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p { int new_cpu = prev_cpu; + if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed)) + return prev_cpu; + while (sd) { struct sched_group *group; struct sched_domain *tmp; -- 2.14.1