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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 C8D57C388F7 for ; Mon, 9 Nov 2020 12:21:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 768F7206D8 for ; Mon, 9 Nov 2020 12:21:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="pjhICHrM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729570AbgKIMV5 (ORCPT ); Mon, 9 Nov 2020 07:21:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729174AbgKIMV4 (ORCPT ); Mon, 9 Nov 2020 07:21:56 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98F78C0613CF; Mon, 9 Nov 2020 04:21:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=lo1/YZJ60PDURw//yTKYZnX3pdE1wM16etWDAmUtFRw=; b=pjhICHrM3eR4uIrNFE4t/28ZFK 1j9Du9Tq+OjnCR8k4XxcUymdhlaBzmdAPspUA8GbUuGGLSdUkAB2irMJ1Km5qy/3+1/AXtxD+VRyF AHeC1U7hmSElLZNKDc26GidSnfu01Y1n/qxp/PTGpadnToggGm7RpTrP/TirXts95aiSuqyFMtuFB kwGkT9cIg/DTx5nE6wqSReHOIMiMBFicrpneUhZA1dd8lpBteemH8HjobgVW9+VMuoEqjv3Nya9FO 1+Gt0m/4RW/PBYkYh9jsQdUs8x5GDPXIeU0eyIl9xzu6dFJdAjL7S0iYuI066QdrITasayx8HmDMq 1r2mk3uw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kc6Ax-0001RS-Kq; Mon, 09 Nov 2020 12:21:35 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 9FAA4306099; Mon, 9 Nov 2020 13:21:33 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4D993203C5333; Mon, 9 Nov 2020 13:21:33 +0100 (CET) Date: Mon, 9 Nov 2020 13:21:33 +0100 From: Peter Zijlstra To: paulmck@kernel.org Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org Subject: Re: [PATCH tip/core/rcu 1/4] doc: Present the role of READ_ONCE() Message-ID: <20201109122133.GL2594@hirez.programming.kicks-ass.net> References: <20201105230444.GA18574@paulmck-ThinkPad-P72> <20201105230510.18660-1-paulmck@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201105230510.18660-1-paulmck@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 05, 2020 at 03:05:07PM -0800, paulmck@kernel.org wrote: > From: "Paul E. McKenney" > > This commit adds an explanation of the special cases where READ_ONCE() > may be used in place of a member of the rcu_dereference() family. I am confused, there is no actual difference between rcu_dereference() and READ_ONCE() today. So we _may_ use READ_ONCE() at all times. Now granted, we probably don't want that, but that does leave me somewhat confused vs the wording here.