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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 901F4C433DF for ; Thu, 2 Jul 2020 08:28:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 601EC20720 for ; Thu, 2 Jul 2020 08:28:55 +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="Gw3bFkBi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728025AbgGBI2x (ORCPT ); Thu, 2 Jul 2020 04:28:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726042AbgGBI2v (ORCPT ); Thu, 2 Jul 2020 04:28:51 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49BFDC08C5C1; Thu, 2 Jul 2020 01:28:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=1j2DrlcbUugnfL/BNKwgbBGwdXe1p5YiDNDgH1lziiA=; b=Gw3bFkBiw7lSr8XB4zKQSY2gM3 tJk/ji3zgpfflj/zaSGFhyr7KMwLj+Oe+0Sm+KHfgrWViOHfPxx7b/QpCRZnd7QyWyLqPOjt5u4M+ VT2c7Tj/WbWZ13AD1/9R0UzoNtp4d+F1m8batuj5Xl7qdQTZYJNIcpd7a6z0ADN51FPDOud+x2inb vaWHcRWO38JcCO7v+Lm2XkFcXbg2GQMLv/ahw7WmAbTz34o8N8P/o1BFnXY9TMJge7Bqawg2gEdUW veyOYqGH2bZGaUNyWTxK59SurZc9DII4ezuMOTRrJmJ1ycOYDis9O0xqtG1x7WpxmweqV5UnoKy94 H7QDMhfg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jquaH-0000Gw-TV; Thu, 02 Jul 2020 08:28:42 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1CDA230015A; Thu, 2 Jul 2020 10:28:40 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0AA3620CC68A2; Thu, 2 Jul 2020 10:28:40 +0200 (CEST) Date: Thu, 2 Jul 2020 10:28:40 +0200 From: Peter Zijlstra To: Nicholas Piggin Cc: Will Deacon , Boqun Feng , Ingo Molnar , Waiman Long , Anton Blanchard , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 2/8] powerpc/pseries: use smp_rmb() in H_CONFER spin yield Message-ID: <20200702082840.GC4781@hirez.programming.kicks-ass.net> References: <20200702074839.1057733-1-npiggin@gmail.com> <20200702074839.1057733-3-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200702074839.1057733-3-npiggin@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 02, 2020 at 05:48:33PM +1000, Nicholas Piggin wrote: > There is no need for rmb(), this allows faster lwsync here. Since you determined this; I'm thinking you actually understand the ordering here. How about recording this understanding in a comment? Also, should the lock->slock load not use READ_ONCE() ?