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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C16B6ECAAD4 for ; Mon, 29 Aug 2022 12:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229484AbiH2MmH (ORCPT ); Mon, 29 Aug 2022 08:42:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230181AbiH2Ml2 (ORCPT ); Mon, 29 Aug 2022 08:41:28 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C5F4AA36D; Mon, 29 Aug 2022 05:25:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9008BB80F9A; Mon, 29 Aug 2022 12:25:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C1B6C433D7; Mon, 29 Aug 2022 12:25:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661775952; bh=3iB3FPdcSvm99iM6SmOB3c5yrDWVJ8azBbcMqlPGahU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=U9rc4Pl+o0ydfA3ZabupGKgLAeKFGa9VTdEKPzEQfZJGvjz5rf/x1+Pa6RMPxDiBC 9jqfx+lScrIMrvPA3riy7bAjy4iXqnOeiQ5RpXRLfKI7wATqiPdDv9jOfTtNr2h+Yq Wa20ghuu2acgEA3aLSs3uLf5wthIZ6qxjVhNb0qvfc8x3Zav6sSokUCAjA+A0+P5de bQNqtx2Zwz2+DaKO6sCI3kLAmL8NA46x3FcuUCCe0t5hFORtboJg0kbLnB+FUuI9EE UulxZQCkL5hNebcDXHpxCKz4XhYLZsSfE1TMqSUpfspvZpiyzGy3XWlxAXXfudtV4Q DnEHl86Tq6WOA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id D087A5C019C; Mon, 29 Aug 2022 05:25:51 -0700 (PDT) Date: Mon, 29 Aug 2022 05:25:51 -0700 From: "Paul E. McKenney" To: Andrea Parri Cc: stern@rowland.harvard.edu, 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, dlustig@nvidia.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: "Verifying and Optimizing Compact NUMA-Aware Locks on Weak Memory Models" Message-ID: <20220829122551.GL6159@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20220826124812.GA3007435@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Mon, Aug 29, 2022 at 04:33:23AM +0200, Andrea Parri wrote: > On Fri, Aug 26, 2022 at 05:48:12AM -0700, Paul E. McKenney wrote: > > Hello! > > > > I have not yet done more than glance at this one, but figured I should > > send it along sooner rather than later. > > > > "Verifying and Optimizing Compact NUMA-Aware Locks on Weak > > Memory Models", Antonio Paolillo, Hernán Ponce-de-León, Thomas > > Haas, Diogo Behrens, Rafael Chehab, Ming Fu, and Roland Meyer. > > https://arxiv.org/abs/2111.15240 > > > > The claim is that the queued spinlocks implementation with CNA violates > > LKMM but actually works on all architectures having a formal hardware > > memory model. > > > > Thoughts? > > Section 4 ends with a discussion about certain "spurious" data races. > Do we have litmus tests with them? (I could repro with Dartagnan...) Their Figure 5 clearly shows a data race, but agreed, their claim is that this race is prevented by other code not in this litmus test. Me, I currently suspect that the spurious data race might be due to the failure to guarantee mutual exclusion, though I have not yet read that paper carefully. That is scheduled for tomorrow morning. Thanx, Paul