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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 3B89EC43461 for ; Fri, 4 Sep 2020 02:39:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BBC92075D for ; Fri, 4 Sep 2020 02:39:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599187198; bh=Gx4Q5qe+KCoxGI03EpDx33dmvhQFLS1/UkVjl6tbZqA=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=Gf6K02wd//YyrK30dWTcXEiT2QSGrADagp6TBXUQZYBv5od2gpaoo8C2T01n/ZPcK CL7IOHeIkr4X0T4Lr7DlSm+cplJU1yhS8cve5gIPo2cseIP/b3o0sCNRefWmSo9kOH bylp6ciwEC78CsYKBqfZWouZ+l54N1ivZ3dZGyGA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729498AbgIDCj5 (ORCPT ); Thu, 3 Sep 2020 22:39:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:36058 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728697AbgIDCj4 (ORCPT ); Thu, 3 Sep 2020 22:39:56 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F107D206D4; Fri, 4 Sep 2020 02:39:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599187196; bh=Gx4Q5qe+KCoxGI03EpDx33dmvhQFLS1/UkVjl6tbZqA=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=wHGTgWWNf47GLCUSRBQFUyHXongWWL7BkCHykoDAufFgTqmVlFN1LhAIcyF3GEK6J p8xMVBSwusMdjwHyLVfLczKGG/xX27XIPLZgloqJDGyEBpesVNJEGWmV70qHLseBcu /YoJRsXrkok85KPDZ643waxfvhPXCAp6Bl97Balo= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C8AB63522636; Thu, 3 Sep 2020 19:39:55 -0700 (PDT) Date: Thu, 3 Sep 2020 19:39:55 -0700 From: "Paul E. McKenney" To: Boqun Feng Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, stern@rowland.harvard.edu, parri.andrea@gmail.com, will@kernel.org, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com Subject: Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed Message-ID: <20200904023955.GX29330@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200831182012.GA1965@paulmck-ThinkPad-P72> <20200831182037.2034-6-paulmck@kernel.org> <20200902035448.GC49492@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> <20200902101412.GC1362448@hirez.programming.kicks-ass.net> <20200902123715.GD49492@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> <20200903233037.GW29330@paulmck-ThinkPad-P72> <20200904005921.GA7503@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200904005921.GA7503@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, Sep 04, 2020 at 08:59:21AM +0800, Boqun Feng wrote: > On Thu, Sep 03, 2020 at 04:30:37PM -0700, Paul E. McKenney wrote: [ . . . ] > > How about like this, adding "Relaxed" to the WRITE_ONCE() and READ_ONCE() > > rows and "RMW" to the "Relaxed operation" row? > > > > Much better now, thanks! However ... > > > The file contents are followed by a diff against the previous version. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ [ . . . ] > > Key: Relaxed: A relaxed operation is either a *_relaxed() RMW > > operation, an unsuccessful RMW operation, READ_ONCE(), > > WRITE_ONCE(), or one of the atomic_read() and > > atomic_set() family of operations. > > And: > a RMW operation that doesn't return any value (e.g > atomic_inc()), IOW it's a void Relaxed operation. Good point! Please see below. Thanx, Paul ------------------------------------------------------------------------ Prior Operation Subsequent Operation --------------- --------------------------- C Self R W RMW Self R W DR DW RMW SV -- ---- - - --- ---- - - -- -- --- -- Relaxed store Y Y Relaxed load Y Y Y Y Relaxed RMW operation Y Y Y Y rcu_dereference() Y Y Y Y Successful *_acquire() R Y Y Y Y Y Y Successful *_release() C Y Y Y W Y smp_rmb() Y R Y Y R smp_wmb() Y W Y Y W smp_mb() & synchronize_rcu() CP Y Y Y Y Y Y Y Y Successful full non-void RMW CP Y Y Y Y Y Y Y Y Y Y Y smp_mb__before_atomic() CP Y Y Y a a a a Y smp_mb__after_atomic() CP a a Y Y Y Y Y Y Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(), a *_relaxed() RMW operation, an unsuccessful RMW operation, a non-value-returning RMW operation such as atomic_inc(), or one of the atomic*_read() and atomic*_set() family of operations. C: Ordering is cumulative P: Ordering propagates R: Read, for example, READ_ONCE(), or read portion of RMW W: Write, for example, WRITE_ONCE(), or write portion of RMW Y: Provides ordering a: Provides ordering given intervening RMW atomic operation DR: Dependent read (address dependency) DW: Dependent write (address, data, or control dependency) RMW: Atomic read-modify-write operation SELF: Orders self, as opposed to accesses before and/or after SV: Orders later accesses to the same variable ------------------------------------------------------------------------ diff --git a/tools/memory-model/Documentation/cheatsheet.txt b/tools/memory-model/Documentation/cheatsheet.txt index 4146b8d..99d0087 100644 --- a/tools/memory-model/Documentation/cheatsheet.txt +++ b/tools/memory-model/Documentation/cheatsheet.txt @@ -17,10 +17,11 @@ smp_mb__before_atomic() CP Y Y Y a a a a Y smp_mb__after_atomic() CP a a Y Y Y Y Y Y -Key: Relaxed: A relaxed operation is either a *_relaxed() RMW - operation, an unsuccessful RMW operation, READ_ONCE(), - WRITE_ONCE(), or one of the atomic_read() and - atomic_set() family of operations. +Key: Relaxed: A relaxed operation is either READ_ONCE(), WRITE_ONCE(), + a *_relaxed() RMW operation, an unsuccessful RMW + operation, a non-value-returning RMW operation such + as atomic_inc(), or one of the atomic*_read() and + atomic*_set() family of operations. C: Ordering is cumulative P: Ordering propagates R: Read, for example, READ_ONCE(), or read portion of RMW