From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751663AbdJELps (ORCPT ); Thu, 5 Oct 2017 07:45:48 -0400 Received: from foss.arm.com ([217.140.101.70]:44046 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751372AbdJELpp (ORCPT ); Thu, 5 Oct 2017 07:45:45 -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 5/5] sched/fair: Fix use of find_idlest_group when local group is idlest Date: Thu, 5 Oct 2017 12:45:16 +0100 Message-Id: <20171005114516.18617-6-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 find_idlest_group returns NULL when the local group is idlest. The caller then continues the find_idlest_group search at a lower level of the current CPU's sched_domain hierarchy. find_idlest_group_cpu is not consulted and, crucially, @new_cpu is not updated. This means the search is pointless and we return @prev_cpu from select_task_rq_fair. This is fixed by initialising @new_cpu to @cpu instead of @prev_cpu. 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: Josef Bacik Reviewed-by: Vincent Guittot --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4a14ebca4d79..82a8e206657f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5955,7 +5955,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p, int cpu, int prev_cpu, int sd_flag) { - int new_cpu = prev_cpu; + int new_cpu = cpu; if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed)) return prev_cpu; -- 2.14.1