From nobody Fri Apr 17 22:32:16 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2173C43334 for ; Thu, 21 Jul 2022 08:45:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231738AbiGUIo5 (ORCPT ); Thu, 21 Jul 2022 04:44:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232513AbiGUIop (ORCPT ); Thu, 21 Jul 2022 04:44:45 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 750077E83E; Thu, 21 Jul 2022 01:44:43 -0700 (PDT) Date: Thu, 21 Jul 2022 08:44:40 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1658393082; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2/HxTgTi2hh26sKnEn3z6YHkmbekBR6IHKx5QyttQJk=; b=bRIH2TXWPrArPWnxq08UNTia3teOGOrYyg0G9NGGi75ei1OBfFF2WjS6kNM4Su4gywuiRX anwUsQ4mN0jbHmzWCT/b9ElT9IS4Wsdd59CeZI8sH4zO5JSxBR3JQfXPogBxmYQc5Zcb7c seuGncDQ+2Ya4M3CEEUlxJaaspUCDEdZprvHiEDnfcm9IiPNLQyXEawPe4bHz0WCjpbFfJ 4CeCRv3bodKby6yZcPNKrvn3v9618JvAyr5/jNNX5lcO6X0WH3ynJftLIBlJj2OKjL0r3f qffRyb6ggAlETVsUDj0/kJTqB74KonNuWJSY9gtQTScL/t7hB2uMFGIAN0fhvw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1658393082; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2/HxTgTi2hh26sKnEn3z6YHkmbekBR6IHKx5QyttQJk=; b=Z0f5Aj5JpN+x92QV+fBZK+ud7BDpZBUZhMqYmh2n4Zh69h1DUpyi5hJ4ShK2lHHwRK+XKS 6CRSOco1cznzL0AA== From: "tip-bot2 for Nicolas Saenz Julienne" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt() Cc: Nicolas Saenz Julienne , "Peter Zijlstra (Intel)" , Valentin Schneider , Phil Auld , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220628092259.330171-1-nsaenzju@redhat.com> References: <20220628092259.330171-1-nsaenzju@redhat.com> MIME-Version: 1.0 Message-ID: <165839308090.15455.9464474001123522013.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 5c66d1b9b30f737fcef85a0b75bfe0590e16b62a Gitweb: https://git.kernel.org/tip/5c66d1b9b30f737fcef85a0b75bfe0590= e16b62a Author: Nicolas Saenz Julienne AuthorDate: Tue, 28 Jun 2022 11:22:59 +02:00 Committer: Peter Zijlstra CommitterDate: Thu, 21 Jul 2022 10:39:38 +02:00 nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt() dequeue_task_rt() only decrements 'rt_rq->rt_nr_running' after having called sched_update_tick_dependency() preventing it from re-enabling the tick on systems that no longer have pending SCHED_RT tasks but have multiple runnable SCHED_OTHER tasks: dequeue_task_rt() dequeue_rt_entity() dequeue_rt_stack() dequeue_top_rt_rq() sub_nr_running() // decrements rq->nr_running sched_update_tick_dependency() sched_can_stop_tick() // checks rq->rt.rt_nr_running, ... __dequeue_rt_entity() dec_rt_tasks() // decrements rq->rt.rt_nr_running ... Every other scheduler class performs the operation in the opposite order, and sched_update_tick_dependency() expects the values to be updated as such. So avoid the misbehaviour by inverting the order in which the above operations are performed in the RT scheduler. Fixes: 76d92ac305f2 ("sched: Migrate sched to use new tick dependency mask = model") Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Reviewed-by: Phil Auld Link: https://lore.kernel.org/r/20220628092259.330171-1-nsaenzju@redhat.com --- kernel/sched/rt.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 8c9ed96..55f39c8 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -480,7 +480,7 @@ static inline void rt_queue_push_tasks(struct rq *rq) #endif /* CONFIG_SMP */ =20 static void enqueue_top_rt_rq(struct rt_rq *rt_rq); -static void dequeue_top_rt_rq(struct rt_rq *rt_rq); +static void dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count); =20 static inline int on_rt_rq(struct sched_rt_entity *rt_se) { @@ -601,7 +601,7 @@ static void sched_rt_rq_dequeue(struct rt_rq *rt_rq) rt_se =3D rt_rq->tg->rt_se[cpu]; =20 if (!rt_se) { - dequeue_top_rt_rq(rt_rq); + dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running); /* Kick cpufreq (see the comment in kernel/sched/sched.h). */ cpufreq_update_util(rq_of_rt_rq(rt_rq), 0); } @@ -687,7 +687,7 @@ static inline void sched_rt_rq_enqueue(struct rt_rq *rt= _rq) =20 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq) { - dequeue_top_rt_rq(rt_rq); + dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running); } =20 static inline int rt_rq_throttled(struct rt_rq *rt_rq) @@ -1089,7 +1089,7 @@ static void update_curr_rt(struct rq *rq) } =20 static void -dequeue_top_rt_rq(struct rt_rq *rt_rq) +dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count) { struct rq *rq =3D rq_of_rt_rq(rt_rq); =20 @@ -1100,7 +1100,7 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq) =20 BUG_ON(!rq->nr_running); =20 - sub_nr_running(rq, rt_rq->rt_nr_running); + sub_nr_running(rq, count); rt_rq->rt_queued =3D 0; =20 } @@ -1486,18 +1486,21 @@ static void __dequeue_rt_entity(struct sched_rt_ent= ity *rt_se, unsigned int flag static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int f= lags) { struct sched_rt_entity *back =3D NULL; + unsigned int rt_nr_running; =20 for_each_sched_rt_entity(rt_se) { rt_se->back =3D back; back =3D rt_se; } =20 - dequeue_top_rt_rq(rt_rq_of_se(back)); + rt_nr_running =3D rt_rq_of_se(back)->rt_nr_running; =20 for (rt_se =3D back; rt_se; rt_se =3D rt_se->back) { if (on_rt_rq(rt_se)) __dequeue_rt_entity(rt_se, flags); } + + dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running); } =20 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int = flags)