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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 648F1C35242 for ; Fri, 24 Jan 2020 09:39:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3885320838 for ; Fri, 24 Jan 2020 09:39:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579858754; bh=HdT58Yiqp0jmr/sDUj4BFGZyrgcM7XM5tIMrOuWTN1A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1i5jecGlcRIp36cD+WFijTyLMK8vpOrEUEsXgY/7nmkMQwZ0NE6s5oa++zerqLaIj /XAEfsiaNOaG1jXAZqKmo+1s5P0IKxQOGr5ldUE/ZDSCQQ12Fb8C5vggvEndZ4MggR DX9IZuZ7zuEC5UQJ3tSWQjrhUUbonjWYGlD9QKsk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729180AbgAXJjN (ORCPT ); Fri, 24 Jan 2020 04:39:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:36346 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729924AbgAXJjM (ORCPT ); Fri, 24 Jan 2020 04:39:12 -0500 Received: from localhost (unknown [145.15.244.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 748F920709; Fri, 24 Jan 2020 09:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579858751; bh=HdT58Yiqp0jmr/sDUj4BFGZyrgcM7XM5tIMrOuWTN1A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ABQgjvWt9UWEBfssCI/B24Za4PkOUZboMprP/QVtkTA0Zu/mKuEWVVPKMa4bCsbSm kbQGVuUHCN+acpwLI1M29eLEAmZim6cYpGcNq/RGdMsUQ0YYzdToYoMNTiCII7N210 dPj6V9j4Tkw3QyfpHSdlfUiqrFriaV6qaVqeWpcE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Linus Torvalds , Thomas Gleixner , bsegall@google.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, ktkhai@virtuozzo.com, mgorman@suse.de, qais.yousef@arm.com, qperret@google.com, rostedt@goodmis.org, valentin.schneider@arm.com, vincent.guittot@linaro.org, Ingo Molnar Subject: [PATCH 5.4 047/102] sched/core: Further clarify sched_class::set_next_task() Date: Fri, 24 Jan 2020 10:30:48 +0100 Message-Id: <20200124092813.389202154@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200124092806.004582306@linuxfoundation.org> References: <20200124092806.004582306@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Zijlstra commit a0e813f26ebcb25c0b5e504498fbd796cca1a4ba upstream. It turns out there really is something special to the first set_next_task() invocation. In specific the 'change' pattern really should not cause balance callbacks. Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: juri.lelli@redhat.com Cc: ktkhai@virtuozzo.com Cc: mgorman@suse.de Cc: qais.yousef@arm.com Cc: qperret@google.com Cc: rostedt@goodmis.org Cc: valentin.schneider@arm.com Cc: vincent.guittot@linaro.org Fixes: f95d4eaee6d0 ("sched/{rt,deadline}: Fix set_next_task vs pick_next_task") Link: https://lkml.kernel.org/r/20191108131909.775434698@infradead.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/sched/deadline.c | 7 +++++-- kernel/sched/fair.c | 2 +- kernel/sched/idle.c | 4 ++-- kernel/sched/rt.c | 7 +++++-- kernel/sched/sched.h | 4 ++-- kernel/sched/stop_task.c | 4 ++-- 6 files changed, 17 insertions(+), 11 deletions(-) --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1743,13 +1743,16 @@ static void start_hrtick_dl(struct rq *r } #endif -static void set_next_task_dl(struct rq *rq, struct task_struct *p) +static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first) { p->se.exec_start = rq_clock_task(rq); /* You can't push away the running task */ dequeue_pushable_dl_task(rq, p); + if (!first) + return; + if (hrtick_enabled(rq)) start_hrtick_dl(rq, p); @@ -1785,7 +1788,7 @@ pick_next_task_dl(struct rq *rq, struct dl_se = pick_next_dl_entity(rq, dl_rq); BUG_ON(!dl_se); p = dl_task_of(dl_se); - set_next_task_dl(rq, p); + set_next_task_dl(rq, p, true); return p; } --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10151,7 +10151,7 @@ static void switched_to_fair(struct rq * * This routine is mostly called to set cfs_rq->curr field when a task * migrates between groups/classes. */ -static void set_next_task_fair(struct rq *rq, struct task_struct *p) +static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) { struct sched_entity *se = &p->se; --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -385,7 +385,7 @@ static void put_prev_task_idle(struct rq { } -static void set_next_task_idle(struct rq *rq, struct task_struct *next) +static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first) { update_idle_core(rq); schedstat_inc(rq->sched_goidle); @@ -399,7 +399,7 @@ pick_next_task_idle(struct rq *rq, struc if (prev) put_prev_task(rq, prev); - set_next_task_idle(rq, next); + set_next_task_idle(rq, next, true); return next; } --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1515,13 +1515,16 @@ static void check_preempt_curr_rt(struct #endif } -static inline void set_next_task_rt(struct rq *rq, struct task_struct *p) +static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first) { p->se.exec_start = rq_clock_task(rq); /* The running task is never eligible for pushing */ dequeue_pushable_task(rq, p); + if (!first) + return; + /* * If prev task was rt, put_prev_task() has already updated the * utilization. We only care of the case where we start to schedule a @@ -1575,7 +1578,7 @@ pick_next_task_rt(struct rq *rq, struct return NULL; p = _pick_next_task_rt(rq); - set_next_task_rt(rq, p); + set_next_task_rt(rq, p, true); return p; } --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1728,7 +1728,7 @@ struct sched_class { struct task_struct *prev, struct rq_flags *rf); void (*put_prev_task)(struct rq *rq, struct task_struct *p); - void (*set_next_task)(struct rq *rq, struct task_struct *p); + void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first); #ifdef CONFIG_SMP int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); @@ -1780,7 +1780,7 @@ static inline void put_prev_task(struct static inline void set_next_task(struct rq *rq, struct task_struct *next) { WARN_ON_ONCE(rq->curr != next); - next->sched_class->set_next_task(rq, next); + next->sched_class->set_next_task(rq, next, false); } #ifdef CONFIG_SMP --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -29,7 +29,7 @@ check_preempt_curr_stop(struct rq *rq, s /* we're never preempted */ } -static void set_next_task_stop(struct rq *rq, struct task_struct *stop) +static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first) { stop->se.exec_start = rq_clock_task(rq); } @@ -42,7 +42,7 @@ pick_next_task_stop(struct rq *rq, struc if (!sched_stop_runnable(rq)) return NULL; - set_next_task_stop(rq, rq->stop); + set_next_task_stop(rq, rq->stop, true); return rq->stop; }