From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 344BBC10F14 for ; Sat, 12 Oct 2019 06:52:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 161952089C for ; Sat, 12 Oct 2019 06:52:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728904AbfJLGwW (ORCPT ); Sat, 12 Oct 2019 02:52:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54390 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727115AbfJLGwV (ORCPT ); Sat, 12 Oct 2019 02:52:21 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3A81C6908D; Sat, 12 Oct 2019 06:52:21 +0000 (UTC) Received: from t460p.redhat.com (ovpn-117-172.phx2.redhat.com [10.3.117.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 64D8160A97; Sat, 12 Oct 2019 06:52:20 +0000 (UTC) From: Scott Wood To: Sebastian Andrzej Siewior Cc: Thomas Gleixner , Steven Rostedt , Peter Zijlstra , Juri Lelli , Waiman Long , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Scott Wood Subject: [PATCH RT v2 1/3] sched: migrate_enable: Use select_fallback_rq() Date: Sat, 12 Oct 2019 01:52:12 -0500 Message-Id: <20191012065214.28109-2-swood@redhat.com> In-Reply-To: <20191012065214.28109-1-swood@redhat.com> References: <20191012065214.28109-1-swood@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Sat, 12 Oct 2019 06:52:21 +0000 (UTC) Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org migrate_enable() currently open-codes a variant of select_fallback_rq(). However, it does not have the "No more Mr. Nice Guy" fallback and thus it will pass an invalid CPU to the migration thread if cpus_mask only contains a CPU that is !active. Signed-off-by: Scott Wood --- This scenario will be more likely after the next patch, since the migrate_disable_update check goes away. However, it could happen anyway if cpus_mask was updated to a CPU other than the one we were pinned to, and that CPU subsequently became inactive. --- kernel/sched/core.c | 25 ++++++++++--------------- 1 file changed, 10 insertions(+), 15 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 93b4ae1ecaff..bfd160e90797 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7405,6 +7405,7 @@ void migrate_enable(void) if (p->migrate_disable_update) { struct rq *rq; struct rq_flags rf; + int cpu = task_cpu(p); rq = task_rq_lock(p, &rf); update_rq_clock(rq); @@ -7414,21 +7415,15 @@ void migrate_enable(void) p->migrate_disable_update = 0; - WARN_ON(smp_processor_id() != task_cpu(p)); - if (!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) { - const struct cpumask *cpu_valid_mask = cpu_active_mask; - struct migration_arg arg; - unsigned int dest_cpu; - - if (p->flags & PF_KTHREAD) { - /* - * Kernel threads are allowed on online && !active CPUs - */ - cpu_valid_mask = cpu_online_mask; - } - dest_cpu = cpumask_any_and(cpu_valid_mask, &p->cpus_mask); - arg.task = p; - arg.dest_cpu = dest_cpu; + WARN_ON(smp_processor_id() != cpu); + if (!cpumask_test_cpu(cpu, &p->cpus_mask)) { + struct migration_arg arg = { p }; + struct rq_flags rf; + + rq = task_rq_lock(p, &rf); + update_rq_clock(rq); + arg.dest_cpu = select_fallback_rq(cpu, p); + task_rq_unlock(rq, p, &rf); unpin_current_cpu(); preempt_lazy_enable(); -- 1.8.3.1