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,URIBL_BLOCKED,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 3F674C433E7 for ; Thu, 8 Oct 2020 18:32:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D9F08221FC for ; Thu, 8 Oct 2020 18:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602181961; bh=/8fOwt/Qn5xe/dYjyUSsAHEDn2T/gSBbNJtdJH0G9q0=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=nRwBwyxi2+ef3CcCk6iK2mZAwyS6BjwSTWppfds3dmeI0n+QxuQ3wUvUF/ZGsy08c eFkSNu3vcGFoO7cRLyEVEYTDGRxAeFhc3lvw86onkovwvkew7AxRUt53nJo7ILgjRu nqwO5AT1FS/cBvXKoPVfJz6j6RopVjh/1dJB2zVY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728988AbgJHScl (ORCPT ); Thu, 8 Oct 2020 14:32:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:47786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728464AbgJHScl (ORCPT ); Thu, 8 Oct 2020 14:32:41 -0400 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 773602145D; Thu, 8 Oct 2020 18:32:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602181960; bh=/8fOwt/Qn5xe/dYjyUSsAHEDn2T/gSBbNJtdJH0G9q0=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=rekAvmMoqxdT8aLb8t4dTGfslNnoBg1qFhMCXA01qhfaDg8SGWsipwsjh447JaX7j wKltTDgCHKyhF1P+kUuW/sRiNOsWA4C7KSpQlgffnL0FXnC0JQISmDYI4xFWEaV8yL XnABhduU0dwhBjnixh+VVmUnHom1Yw0jSc/nuy88= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 1231235228D5; Thu, 8 Oct 2020 11:32:39 -0700 (PDT) Date: Thu, 8 Oct 2020 11:32:39 -0700 From: "Paul E. McKenney" To: Alan Stern Cc: Luc Maranget , Akira Yokosawa , 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, dlustig@nvidia.com, joel@joelfernandes.org, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: Bug in herd7 [Was: Re: Litmus test for question from Al Viro] Message-ID: <20201008183239.GZ29330@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201005191801.GF29330@paulmck-ThinkPad-P72> <20201005194834.GB389867@rowland.harvard.edu> <20201006163954.GM29330@paulmck-ThinkPad-P72> <20201006170525.GA423499@rowland.harvard.edu> <20201007175040.GQ29330@paulmck-ThinkPad-P72> <20201007194050.GC468921@rowland.harvard.edu> <20201007223851.GV29330@paulmck-ThinkPad-P72> <20201008022537.GA480405@rowland.harvard.edu> <20201008025025.GX29330@paulmck-ThinkPad-P72> <20201008140148.GA495091@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201008140148.GA495091@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 Thu, Oct 08, 2020 at 10:01:48AM -0400, Alan Stern wrote: > On Wed, Oct 07, 2020 at 07:50:25PM -0700, Paul E. McKenney wrote: > > There are some distractions at the moment. > > > > Please see below. If this is not exactly correct, I will use "git rm" > > and let you submit the patch as you wish. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit dc0119c24b64f9d541b94ba5d17eec0cbc265bfa > > Author: Alan Stern > > Date: Tue Oct 6 09:38:37 2020 -0700 > > > > manual/kernel: Add LB data dependency test with no intermediate variable > > > > Test whether herd7 can detect a data dependency when there is no > > intermediate local variable, as in WRITE_ONCE(*x, READ_ONCE(*y)). > > Commit 0f3f8188a326 in herdtools fixed an oversight which caused such > > dependencies to be missed. > > > > Signed-off-by: Alan Stern > > Signed-off-by: Paul E. McKenney > > > > diff --git a/manual/kernel/C-LB+mb+data.litmus b/manual/kernel/C-LB+mb+data.litmus > > new file mode 100644 > > index 0000000..e9e24e0 > > --- /dev/null > > +++ b/manual/kernel/C-LB+mb+data.litmus > > @@ -0,0 +1,27 @@ > > +C LB+mb+data > > +(* > > + * Result: Never > > + * > > + * Versions of herd7 prior to commit 0f3f8188a326 ("[herd] Fix dependency > > + * definition") recognize data dependencies only when they flow through > > + * an intermediate local variable. Since the dependency in P1 doesn't, > > + * those versions get the wrong answer for this test. > > + *) > > + > > +{} > > + > > +P0(int *x, int *y) > > +{ > > + int r1; > > + > > + r1 = READ_ONCE(*x); > > + smp_mb(); > > + WRITE_ONCE(*y, r1); > > +} > > + > > +P1(int *x, int *y) > > +{ > > + WRITE_ONCE(*x, READ_ONCE(*y)); > > +} > > + > > +exists (0:r1=1) > > Okay, that's exactly what it should be. :-) Whew!!! ;-) Thanx, Paul