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=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 94698C433DF for ; Thu, 2 Jul 2020 10:25:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70FF020747 for ; Thu, 2 Jul 2020 10:25:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fwrGZyQ5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728402AbgGBKZv (ORCPT ); Thu, 2 Jul 2020 06:25:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37714 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728332AbgGBKZu (ORCPT ); Thu, 2 Jul 2020 06:25:50 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E9A4C08C5C1; Thu, 2 Jul 2020 03:25:50 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id l6so9165309pjq.1; Thu, 02 Jul 2020 03:25:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :message-id:content-transfer-encoding; bh=2dEmOOaTKGF4Qlb49VhQf6A9PlFA3b36H9rV7z7cwEs=; b=fwrGZyQ5ZsT9XNpr3/IOWdRZ6ocaZNwfSU2kbuorYXlEEdLE5/x5p3TVpSz28QRp1G Rq97XWBtS9UIquZ9RJU/9RJJsvs3vSblV7P3bcy3AJKNZxupjf8CAIH6Vx5/rgUgktkk duzXAxjb/9SdEDlWvBSKLc74Js/6Hemi2omyXcEecBxTRXPd6QyrD+31gJzLltU6iW8n JF08jA85kpDrr4bA2nZyBfxoqXA5dQqxwaS7+++ll1ExbDrK2qXYBnMpcyDzOvT90egd caLSXaJhoRisXKEQ9uGYLW2o3jDa/MNsoH7QZe8RRqAZWZ+dpbslBRZd5PEW6CLytugN 5Hfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:message-id:content-transfer-encoding; bh=2dEmOOaTKGF4Qlb49VhQf6A9PlFA3b36H9rV7z7cwEs=; b=crHdoLsOAH+pib/GilJMwAx0lEpkC5C6Y6pFIE0yITds7lB7vvIU1greZXTVvOo9W9 jEW3QI8howa3FG28xGVNPNTjffb51lvho76Xy52kO8QdN3OLGLR7OpAVOTjYO02nZPJC gFjQE8HUzb9y2N9ESGYetjJB0anbFSXaclj+ocl1wICCGsMKNUEgr4pc6F/8Fc5U7QsA vg5kqCF/zYBNGUQFLM5tMHwRoRjOEA9FAjA4HKbZLpVgK8lb22M4Smnogsi2qEaAyGKZ AJVF+dnwtaMruhGdJkv6S8mKpaqPoyakHnuukq8n2hYa4q8FK5HXunXskXPAdbpyECuo fC2A== X-Gm-Message-State: AOAM531+lEe3SClN/nK0EerXq7b/drtz1hm9C+TYIgtW/eFAkVNUwCp3 GNBKxuewwkfxjzl3IVRqAQU= X-Google-Smtp-Source: ABdhPJx/3IphE9S504xPgr16qEBAcS0ylg8qERwwjyz6fVgDCXDiKIqknM6KTZc4U4Q2EmZZ4gfQeA== X-Received: by 2002:a17:90a:17ab:: with SMTP id q40mr29264299pja.152.1593685549611; Thu, 02 Jul 2020 03:25:49 -0700 (PDT) Received: from localhost (61-68-186-125.tpgi.com.au. [61.68.186.125]) by smtp.gmail.com with ESMTPSA id g18sm8571288pfk.40.2020.07.02.03.25.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jul 2020 03:25:48 -0700 (PDT) Date: Thu, 02 Jul 2020 20:25:43 +1000 From: Nicholas Piggin Subject: Re: [PATCH 5/8] powerpc/64s: implement queued spinlocks and rwlocks To: Will Deacon Cc: Anton Blanchard , Boqun Feng , kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Waiman Long , Ingo Molnar , Peter Zijlstra , virtualization@lists.linux-foundation.org References: <20200702074839.1057733-1-npiggin@gmail.com> <20200702074839.1057733-6-npiggin@gmail.com> <20200702080219.GB16113@willie-the-truck> In-Reply-To: <20200702080219.GB16113@willie-the-truck> MIME-Version: 1.0 Message-Id: <1593685459.r2tfxtfdp6.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Will Deacon's message of July 2, 2020 6:02 pm: > On Thu, Jul 02, 2020 at 05:48:36PM +1000, Nicholas Piggin wrote: >> diff --git a/arch/powerpc/include/asm/qspinlock.h b/arch/powerpc/include= /asm/qspinlock.h >> new file mode 100644 >> index 000000000000..f84da77b6bb7 >> --- /dev/null >> +++ b/arch/powerpc/include/asm/qspinlock.h >> @@ -0,0 +1,20 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _ASM_POWERPC_QSPINLOCK_H >> +#define _ASM_POWERPC_QSPINLOCK_H >> + >> +#include >> + >> +#define _Q_PENDING_LOOPS (1 << 9) /* not tuned */ >> + >> +#define smp_mb__after_spinlock() smp_mb() >> + >> +static __always_inline int queued_spin_is_locked(struct qspinlock *lock= ) >> +{ >> + smp_mb(); >> + return atomic_read(&lock->val); >> +} >=20 > Why do you need the smp_mb() here? A long and sad tale that ends here 51d7d5205d338 Should probably at least refer to that commit from here, since this one=20 is not going to git blame back there. I'll add something. Thanks, Nick