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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 C2AFFC43A1D for ; Thu, 12 Jul 2018 09:44:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D81420BEC for ; Thu, 12 Jul 2018 09:44:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D81420BEC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726687AbeGLJxQ (ORCPT ); Thu, 12 Jul 2018 05:53:16 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:48864 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbeGLJxQ (ORCPT ); Thu, 12 Jul 2018 05:53:16 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CEAF980D; Thu, 12 Jul 2018 02:44:28 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 9F4353F589; Thu, 12 Jul 2018 02:44:28 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id EC3FD1AE53ED; Thu, 12 Jul 2018 10:45:10 +0100 (BST) Date: Thu, 12 Jul 2018 10:45:10 +0100 From: Will Deacon To: Peter Zijlstra Cc: Andrea Parri , Alan Stern , "Paul E. McKenney" , LKMM Maintainers -- Akira Yokosawa , Boqun Feng , Daniel Lustig , David Howells , Jade Alglave , Luc Maranget , Nicholas Piggin , Kernel development list Subject: Re: [PATCH v2] tools/memory-model: Add extra ordering for locks and remove it for ordinary release/acquire Message-ID: <20180712094510.GA23415@arm.com> References: <20180710093821.GA5414@andrea> <20180711094310.GA13963@arm.com> <20180711123421.GA9673@andrea> <20180712074040.GA4920@worktop.programming.kicks-ass.net> <20180712093432.GV2512@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180712093432.GV2512@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 12, 2018 at 11:34:32AM +0200, Peter Zijlstra wrote: > On Thu, Jul 12, 2018 at 09:40:40AM +0200, Peter Zijlstra wrote: > > And I think if we raise atomic*_acquire() to require TSO (but ideally > > raise it to RCsc) we're there. > > To clarify, just the RmW-acquire. Things like atomic_read_acquire() can > stay smp_load_acquire() and be RCpc. I don't have strong opinions about strengthening RmW atomics to TSO, so if it helps to unblock Alan's patch (which doesn't go near this!) then I'll go with it. The important part is that we continue to allow roach motel into the RmW for other accesses in the non-fully-ordered cases. Daniel -- your AMO instructions are cool with this, right? It's just the fence-based implementations that will need help? Will