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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 D541DC433EF for ; Thu, 16 Sep 2021 17:32:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C165B6023D for ; Thu, 16 Sep 2021 17:32:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353433AbhIPRdg (ORCPT ); Thu, 16 Sep 2021 13:33:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:46946 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348146AbhIPRX6 (ORCPT ); Thu, 16 Sep 2021 13:23:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8EE8961BD1; Thu, 16 Sep 2021 16:43:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631810620; bh=s/eE8MQCbRlB/JbAF45EWPTDmeJAF5NuQ61zEC913j8=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=Ha3kQcDSm0xzs+5Sf6sq84zgdcKeE8mziK5GvCAiLEafrYXOcSnITqmLtd6LfAidG 4Or/y6oX8N6gP5Pi6Dbf2gS+O7pNbFR4PSoyRsUO2CxZqlmfMafXchVfYRsID4ekzk K/lL/QWvD0fMduiTlZN+j9Hm5bPRMwkIybOdgznJYnhTCw+wN7GFKBhLstu/gUnVRT KOFziDKuRzqUfZhtVGUYq3x2seitW1EeTvkh7S+nGWccFpNvi75q3Yx0l5eNPSFDIN /5Epp9G9RB0HDpRRUvnHIboFcw6liRhpjBnJrwldnILsUt1CpPNev/NcTHGdkD+7sd 9eAPgqbVeeEqA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 584E35C028C; Thu, 16 Sep 2021 09:43:40 -0700 (PDT) Date: Thu, 16 Sep 2021 09:43:40 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: LKML , rcu@vger.kernel.org, urezki@gmail.com, boqun.feng@gmail.com, Neeraj Upadhyay , joel@joelfernandes.org Subject: Re: [PATCH 2/4] rcu: Remove useless WRITE_ONCE() on rcu_data.exp_deferred_qs Message-ID: <20210916164340.GF4156@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210916121048.36623-1-frederic@kernel.org> <20210916121048.36623-3-frederic@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210916121048.36623-3-frederic@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 16, 2021 at 02:10:46PM +0200, Frederic Weisbecker wrote: > This variable is never written nor read remotely. Remove this confusion. > > Signed-off-by: Frederic Weisbecker > --- > kernel/rcu/tree_exp.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h > index f3947c49eee7..4266610b4587 100644 > --- a/kernel/rcu/tree_exp.h > +++ b/kernel/rcu/tree_exp.h > @@ -255,7 +255,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_node *rnp, > */ > static void rcu_report_exp_rdp(struct rcu_data *rdp) > { > - WRITE_ONCE(rdp->exp_deferred_qs, false); > + rdp->exp_deferred_qs = false; Are you sure that this can never be invoked from an interrupt handler? And that rdp->exp_deferred_qs is never read from an interrupt handler? If either can happen, then the WRITE_ONCE() does play a role, right? Thanx, Paul > rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true); > } > > -- > 2.25.1 >