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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53983E95A91 for ; Mon, 9 Oct 2023 13:41:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377353AbjJINl1 (ORCPT ); Mon, 9 Oct 2023 09:41:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377364AbjJINl0 (ORCPT ); Mon, 9 Oct 2023 09:41:26 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CDFFCF for ; Mon, 9 Oct 2023 06:41:24 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00789C433C7; Mon, 9 Oct 2023 13:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1696858883; bh=0G0hg7UukneNEO0Z4Kf+o1IoQs0+bZyYOKOyfcuM37E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0tBzNjCf+M7x/UqmQ2e3L7guiRrWlqPN+64wg/QBV6jXvEkx8aA5LaJOHlIWcNqwt CS/vwL/PAoA4UAS5aGtWleTeldWeYA4ci/7nyJCukTNpAWRkd83KECPG90ibcsOX7Z FHwtUURC+Ic18Kh7buUUwyl1iTNV0lzWns/peb78= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , Chengming Zhou , Ovidiu Panait , Sasha Levin Subject: [PATCH 5.10 131/226] sched/cpuacct: Optimize away RCU read lock Date: Mon, 9 Oct 2023 15:01:32 +0200 Message-ID: <20231009130130.186737130@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231009130126.697995596@linuxfoundation.org> References: <20231009130126.697995596@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chengming Zhou commit dc6e0818bc9a0336d9accf3ea35d146d72aa7a18 upstream. Since cpuacct_charge() is called from the scheduler update_curr(), we must already have rq lock held, then the RCU read lock can be optimized away. And do the same thing in it's wrapper cgroup_account_cputime(), but we can't use lockdep_assert_rq_held() there, which defined in kernel/sched/sched.h. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@bytedance.com [OP: adjusted lockdep_assert_rq_held() -> lockdep_assert_held()] Signed-off-by: Ovidiu Panait Signed-off-by: Sasha Levin --- include/linux/cgroup.h | 2 -- kernel/sched/cpuacct.c | 4 +--- 2 files changed, 1 insertion(+), 5 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 959b370733f09..7653f54189502 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -779,11 +779,9 @@ static inline void cgroup_account_cputime(struct task_struct *task, cpuacct_charge(task, delta_exec); - rcu_read_lock(); cgrp = task_dfl_cgroup(task); if (cgroup_parent(cgrp)) __cgroup_account_cputime(cgrp, delta_exec); - rcu_read_unlock(); } static inline void cgroup_account_cputime_field(struct task_struct *task, diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index 3c59c541dd314..8ee298321d78b 100644 --- a/kernel/sched/cpuacct.c +++ b/kernel/sched/cpuacct.c @@ -331,12 +331,10 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime) unsigned int cpu = task_cpu(tsk); struct cpuacct *ca; - rcu_read_lock(); + lockdep_assert_held(&cpu_rq(cpu)->lock); for (ca = task_ca(tsk); ca; ca = parent_ca(ca)) *per_cpu_ptr(ca->cpuusage, cpu) += cputime; - - rcu_read_unlock(); } /* -- 2.40.1