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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 7D26FC2D0A3 for ; Fri, 6 Nov 2020 18:04:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2234421D81 for ; Fri, 6 Nov 2020 18:04:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604685888; bh=h164DUbrltXAvgsRUwKtqAsftPyhoc7Fn/OhofvTlRk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=Yyn+b8tF/AakieX6LBph4lSY3PFi6P8VJMDYmImDaXGxfmHiI6K/xdajpw+dnJnQA gxkxn8FFt5GuN4z2H4hO0goEeWGVDC6SxY5lJBwKCtuHOLAJ0qaDJScivkwml9lTe3 jFOjZGel6e/78CMdvYu2oAfWkmYoUpxRfqgKxV/I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727069AbgKFSEr (ORCPT ); Fri, 6 Nov 2020 13:04:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:33736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727155AbgKFSEr (ORCPT ); Fri, 6 Nov 2020 13:04:47 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 52BA4206FA; Fri, 6 Nov 2020 18:04:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604685886; bh=h164DUbrltXAvgsRUwKtqAsftPyhoc7Fn/OhofvTlRk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=RA/8yJFvpnF0eIgV4Z5w4qpsGAfEKjHOGJXjICr6o+QHlDkMe7yG/Kn0rPv9OO0rh YCKzVzwRmPzqc3N9MLrrA7CQbq5aA0KVjcdMxeYTNjkafGr6i41xy78gXDGPzheqI6 bnf/EtHZkOLnvHV3aF20JZDM3krTPAdsTO/pX3LY= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 0A6E1352097B; Fri, 6 Nov 2020 10:04:46 -0800 (PST) Date: Fri, 6 Nov 2020 10:04:46 -0800 From: "Paul E. McKenney" To: Alan Stern Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, parri.andrea@gmail.com, will@kernel.org, peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com Subject: Re: [PATCH memory-model 5/8] tools/memory-model: Add a glossary of LKMM terms Message-ID: <20201106180445.GX3249@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201105215953.GA15309@paulmck-ThinkPad-P72> <20201105220017.15410-5-paulmck@kernel.org> <20201106165930.GC47039@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106165930.GC47039@rowland.harvard.edu> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, Nov 06, 2020 at 11:59:30AM -0500, Alan Stern wrote: > On Thu, Nov 05, 2020 at 02:00:14PM -0800, paulmck@kernel.org wrote: > > From: "Paul E. McKenney" > > > > Signed-off-by: Paul E. McKenney > > --- > > tools/memory-model/Documentation/glossary.txt | 155 ++++++++++++++++++++++++++ > > 1 file changed, 155 insertions(+) > > create mode 100644 tools/memory-model/Documentation/glossary.txt > > > > diff --git a/tools/memory-model/Documentation/glossary.txt b/tools/memory-model/Documentation/glossary.txt > > new file mode 100644 > > index 0000000..036fa28 > > --- /dev/null > > +++ b/tools/memory-model/Documentation/glossary.txt > > @@ -0,0 +1,155 @@ > > +This document contains brief definitions of LKMM-related terms. Like most > > +glossaries, it is not intended to be read front to back (except perhaps > > +as a way of confirming a diagnosis of OCD), but rather to be searched > > +for specific terms. > > + > > + > > +Address Dependency: When the address of a later memory access is computed > > + based on the value returned by an earlier load, an "address > > + dependency" extends from that load extending to the later access. > > + Address dependencies are quite common in RCU read-side critical > > + sections: > > + > > + 1 rcu_read_lock(); > > + 2 p = rcu_dereference(gp); > > + 3 do_something(p->a); > > + 4 rcu_read_unlock(); > > + > > + In this case, because the address of "p->a" on line 3 is computed > > + from the value returned by the rcu_dereference() on line 2, the > > + address dependency extends from that rcu_dereference() to that > > + "p->a". In rare cases, optimizing compilers can destroy address > > + dependencies. Please see Documentation/RCU/rcu_dereference.txt > > + for more information. > > + > > + See also "Control Dependency". > > There should also be an entry for "Data Dependency", linked from here > and from Control Dependency. > > > +Marked Access: An access to a variable that uses an special function or > > + macro such as "r1 = READ_ONCE()" or "smp_store_release(&a, 1)". > > How about "r1 = READ_ONCE(x)"? Good catches! I am planning to squash the commit below into the original. Does that cover it? Thanx, Paul ------------------------------------------------------------------------ commit 27c694f5a049d3edac1f258b888d02650cec936a Author: Paul E. McKenney Date: Fri Nov 6 10:02:41 2020 -0800 squash! tools/memory-model: Add a glossary of LKMM terms [ paulmck: Apply Alan Stern feedback. ] Signed-off-by: Paul E. McKenney diff --git a/tools/memory-model/Documentation/glossary.txt b/tools/memory-model/Documentation/glossary.txt index 383151b..471bf13 100644 --- a/tools/memory-model/Documentation/glossary.txt +++ b/tools/memory-model/Documentation/glossary.txt @@ -22,7 +22,7 @@ Address Dependency: When the address of a later memory access is computed dependencies. Please see Documentation/RCU/rcu_dereference.txt for more information. - See also "Control Dependency". + See also "Control Dependency" and "Data Dependency". Acquire: With respect to a lock, acquiring that lock, for example, using spin_lock(). With respect to a non-lock shared variable, @@ -109,7 +109,7 @@ Happens-Before (hb): A relation between two accesses in which LKMM section of explanation.txt. Marked Access: An access to a variable that uses an special function or - macro such as "r1 = READ_ONCE()" or "smp_store_release(&a, 1)". + macro such as "r1 = READ_ONCE(x)" or "smp_store_release(&a, 1)". See also "Unmarked Access".