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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 5BA1EC43382 for ; Thu, 27 Sep 2018 08:00:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA35E20666 for ; Thu, 27 Sep 2018 08:00:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WPmOmm42" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA35E20666 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1727249AbeI0ORn (ORCPT ); Thu, 27 Sep 2018 10:17:43 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:32908 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726708AbeI0ORn (ORCPT ); Thu, 27 Sep 2018 10:17:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=cj7KRNh9atNQpphncGWvDaQuTW0KZ7UuVq+Its9Pn7U=; b=WPmOmm42FH75ThdZM3aatjrnF KpkdCWUHNNUkXmiF0c3bltZsmYxLXqjRqsTh7RrjHnC4kSNlrM+hYBt3m2asK/pvGYD8QxxOk1lsa Z6/LBRXrhkVGmj9JYElc4Wsa4yDOgA/IgTHEj9dP0rnNnCRw7dYwDYG2kPvvdsqnwM9nmzVjqoUHU YWdag+BNF9VWggnjjxtC5dPUOhT/AgMEYSXjDXsr1MRejIMBIGxRh60u6m2zV3Pnbre/buOzhNc4T Us9zsuDD4mBBN46V1zTiS673HE8lE4EWcR6QWj70yQMdJ26jQPo+eafmr19bg6301CzZdu9zWgmcC HatALsaPg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1g5RDf-0007W7-4H; Thu, 27 Sep 2018 08:00:40 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 449E2205FF760; Thu, 27 Sep 2018 09:59:35 +0200 (CEST) Date: Thu, 27 Sep 2018 09:59:35 +0200 From: Peter Zijlstra To: Andrea Parri Cc: will.deacon@arm.com, mingo@kernel.org, linux-kernel@vger.kernel.org, longman@redhat.com, tglx@linutronix.de Subject: Re: [RFC][PATCH 3/3] locking/qspinlock: Optimize for x86 Message-ID: <20180927075935.GA4889@hirez.programming.kicks-ass.net> References: <20180926110117.405325143@infradead.org> <20180926111307.513429499@infradead.org> <20180926205208.GA4864@andrea> <20180927071747.GD5254@hirez.programming.kicks-ass.net> <20180927074748.GA7939@andrea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180927074748.GA7939@andrea> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 27, 2018 at 09:47:48AM +0200, Andrea Parri wrote: > > LKMM in particular does _NOT_ deal with mixed sized atomics _at_all_. > > True, but it is nothing conceptually new to deal with: there're Cat > models that handle mixed-size accesses, just give it time. Sure, but until that time I must not rely on (and thus not use) LKMM for qspinlock things. So while your argument about coherence might be true -- I'll have to think about it; litmus tests are out the window.