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=-20.8 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,MENTIONS_GIT_HOSTING,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 E9785C43333 for ; Fri, 22 Jan 2021 17:56:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CBC1B23A81 for ; Fri, 22 Jan 2021 17:56:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729871AbhAVRyH (ORCPT ); Fri, 22 Jan 2021 12:54:07 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:55700 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729244AbhAVRm1 (ORCPT ); Fri, 22 Jan 2021 12:42:27 -0500 Date: Fri, 22 Jan 2021 17:41:34 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1611337295; 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=/1vB1QUr1165eo6pyFtEfPYX+ErJNEqfinIUJxVvEKM=; b=FgFz+xSpdCwceSvwMneDofsr/4IGvBsvNSTtgt7M6OP3LYqtA/b64ByVj60QsI1jJwOVr9 jwUwoVcp34Oq6FCojfbVK7uKe/zxKOZbTUibtzPNEKtPHrPDh1qxU4TsNyCgWj8z4uQW5w hXTEHsGeohmwEEk7sd0NteIRT2PH53rdSfPujxlawt2ZPvIcxNhYJb10vzCQU0QIAuIgT2 5loVuKF3Uf6EAuDqKdio/qqdYtq9RmKEr8gSwzHqwtI3BC81/I9U/qKINTf2iIgrtsiHWn L683C1tma7Y1zCKEo5D9PaN0mZz7k1ycaQYEQaw3u/XMYaftg8c4GXqXETwo9A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1611337295; 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=/1vB1QUr1165eo6pyFtEfPYX+ErJNEqfinIUJxVvEKM=; b=aUEgvQPZmCkjbVtnI2Fs/Hi5NoGAUz6+y1WbwmHqgN5iySfuy1YvQeP4f8CKOA0+5MGcuy Nucw2zrX4f+zvtDw== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched: Prepare to use balance_push in ttwu() Cc: "Peter Zijlstra (Intel)" , Valentin Schneider , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210121103506.966069627@infradead.org> References: <20210121103506.966069627@infradead.org> MIME-Version: 1.0 Message-ID: <161133729464.414.3770602797973233529.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: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 975707f227b07a8212060f94447171d15d7a681b Gitweb: https://git.kernel.org/tip/975707f227b07a8212060f94447171d15d7a681b Author: Peter Zijlstra AuthorDate: Wed, 20 Jan 2021 15:05:41 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 22 Jan 2021 15:09:43 +01:00 sched: Prepare to use balance_push in ttwu() In preparation of using the balance_push state in ttwu() we need it to provide a reliable and consistent state. The immediate problem is that rq->balance_callback gets cleared every schedule() and then re-set in the balance_push_callback() itself. This is not a reliable signal, so add a variable that stays set during the entire time. Also move setting it before the synchronize_rcu() in sched_cpu_deactivate(), such that we get guaranteed visibility to ttwu(), which is a preempt-disable region. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Tested-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210121103506.966069627@infradead.org --- kernel/sched/core.c | 11 ++++++----- kernel/sched/sched.h | 1 + 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8da0fd7..16946b5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7320,6 +7320,7 @@ static void balance_push_set(int cpu, bool on) struct rq_flags rf; rq_lock_irqsave(rq, &rf); + rq->balance_push = on; if (on) { WARN_ON_ONCE(rq->balance_callback); rq->balance_callback = &balance_push_callback; @@ -7489,17 +7490,17 @@ int sched_cpu_deactivate(unsigned int cpu) int ret; set_cpu_active(cpu, false); + balance_push_set(cpu, true); + /* - * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU - * users of this state to go away such that all new such users will - * observe it. + * We've cleared cpu_active_mask / set balance_push, wait for all + * preempt-disabled and RCU users of this state to go away such that + * all new such users will observe it. * * Do sync before park smpboot threads to take care the rcu boost case. */ synchronize_rcu(); - balance_push_set(cpu, true); - rq_lock_irqsave(rq, &rf); if (rq->rd) { update_rq_clock(rq); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 12ada79..bb09988 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -975,6 +975,7 @@ struct rq { unsigned long cpu_capacity_orig; struct callback_head *balance_callback; + unsigned char balance_push; unsigned char nohz_idle_balance; unsigned char idle_balance;