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 9A368E7C4E8 for ; Wed, 4 Oct 2023 18:08:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233618AbjJDSIK (ORCPT ); Wed, 4 Oct 2023 14:08:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243846AbjJDSIJ (ORCPT ); Wed, 4 Oct 2023 14:08:09 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23BECA7 for ; Wed, 4 Oct 2023 11:08:06 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6567CC433C7; Wed, 4 Oct 2023 18:08:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1696442885; bh=qLGAxQEpGIevENzEjZ/6um66IvzRzcgey47ENnRbTEU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zCtMG1RVAvcDRtLVPxYb6Kc5iiFQjZyhPZrHJyOLQr0tBcnuXMk9n++L3dZu5CjD3 ysUBnLe9/I+ql1l9dP/Z6J0Op02HpARUmZaqvfPK/65mw1XiQ35CQ5mi+BGtBx4O1C FkgZIFSJd8qOjAuRz0MpEy1qGSokmnK8AFDWX+Ow= 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 5.15 143/183] sched/cpuacct: Optimize away RCU read lock Date: Wed, 4 Oct 2023 19:56:14 +0200 Message-ID: <20231004175209.987491840@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231004175203.943277832@linuxfoundation.org> References: <20231004175203.943277832@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 5.15-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 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 45cdb12243e3f..f425389ce4bb2 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -792,11 +792,9 @@ 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 cacc2076ad214..f0af0fecde9d9 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_rq_held(cpu_rq(cpu)); for (ca = task_ca(tsk); ca; ca = parent_ca(ca)) *per_cpu_ptr(ca->cpuusage, cpu) += cputime; - - rcu_read_unlock(); } /* -- 2.40.1