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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AFFB6C432BE for ; Sat, 28 Aug 2021 13:55:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E6EB60ED3 for ; Sat, 28 Aug 2021 13:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234346AbhH1N4s (ORCPT ); Sat, 28 Aug 2021 09:56:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbhH1N4r (ORCPT ); Sat, 28 Aug 2021 09:56:47 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE15BC061756 for ; Sat, 28 Aug 2021 06:55:56 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1630158953; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=szT5lkD+YWto/0wcn5LngBYE8usayOdbrKOZ9uNLgNI=; b=csJu0jMX4yt4WEZoYCHowPRFviaigHrC4t5wJ2Z6nfuzYm2AHunep4zQhaoQCTVrWz2XvK 3mwfK424sBX93//QS9c4fDKB/bT8+40dg5Idr6Hl/GQy8S4KaHl09dqXFLiPHOg13e39Nd lESjSOscH5K3AHvhyVE2XOOTl9Zvi30DO9zs87tiY3lPSzZNBfZiiIGm7tJbSYMsG7bEpL TisAnRhToY/uLNalB9omnR/oOmoLruGLdMQm6RBbNFQ7yy9NYhrjQVdBfNbbR8x5S2fsFi B3wh2ytt6uZty4ZK7HeNQxQtRypho8ewv2ZvZVnkoG9o5IszrEJJObZ67BBkcg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1630158953; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=szT5lkD+YWto/0wcn5LngBYE8usayOdbrKOZ9uNLgNI=; b=t5sHQTMaI0H8e5OxYviLacK2pQTLScvYqMXthgFniEO3MH4hs5NEVBj4sPNCBrAbmS0z7r lsbqRurp0ZgRFaBA== To: LKML Cc: Peter Zijlstra , Valentin Schneider , Daniel Bristot de Oliveira , Juri Lelli , Vincent Guittot , Steven Rostedt , Ben Segall , Ingo Molnar , Mel Gorman , Dietmar Eggemann Subject: [PATCH V2] sched: Prevent balance_push() on remote runqueues In-Reply-To: <87eeae11cr.ffs@tglx> References: <87tujb0yn1.ffs@tglx> <87eeae11cr.ffs@tglx> Date: Sat, 28 Aug 2021 15:55:52 +0200 Message-ID: <87zgt1hdw7.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sched_setscheduler() and rt_mutex_setprio() invoke the run-queue balance callback after changing priorities or the scheduling class of a task. The run-queue for which the callback is invoked can be local or remote. That's not a problem for the regular rq::push_work which is serialized with a busy flag in the run-queue struct, but for the balance_push() work which is only valid to be invoked on the outgoing CPU that's wrong. It not only triggers the debug warning, but also leaves the per CPU variable push_work unprotected, which can result in double enqueues on the stop machine list. Remove the warning and validate that the function is invoked on the outgoing CPU. Fixes: ae7927023243 ("sched: Optimize finish_lock_switch()") Reported-by: Sebastian Siewior Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Cc: Juri Lelli Cc: Vincent Guittot Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Ben Segall Cc: Ingo Molnar Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Dietmar Eggemann --- V2: Use the correct check for the outgoing CPU --- kernel/sched/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8435,7 +8435,6 @@ static void balance_push(struct rq *rq) struct task_struct *push_task = rq->curr; lockdep_assert_rq_held(rq); - SCHED_WARN_ON(rq->cpu != smp_processor_id()); /* * Ensure the thing is persistent until balance_push_set(.on = false); @@ -8443,9 +8442,10 @@ static void balance_push(struct rq *rq) rq->balance_callback = &balance_push_callback; /* - * Only active while going offline. + * Only active while going offline and when invoked on the outgoing + * CPU. */ - if (!cpu_dying(rq->cpu)) + if (!cpu_dying(rq->cpu) || rq != this_rq()) return; /*