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[209.132.180.67]) by mx.google.com with ESMTP id k192-v6si5419023pgc.415.2018.09.28.13.19.53; Fri, 28 Sep 2018 13:20:21 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="ZVoZdb//"; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727016AbeI2CpJ (ORCPT + 99 others); Fri, 28 Sep 2018 22:45:09 -0400 Received: from mail-yb1-f196.google.com ([209.85.219.196]:34418 "EHLO mail-yb1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726789AbeI2CpJ (ORCPT ); Fri, 28 Sep 2018 22:45:09 -0400 Received: by mail-yb1-f196.google.com with SMTP id 184-v6so3212620ybg.1; Fri, 28 Sep 2018 13:19:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=HI4q73IG+mRuqdKI+/sZeNi41z3wIZxcUf28STytLfU=; b=ZVoZdb//8DGs7JIf7ZrA/XyuVRVrAj0d9zZU5FWy1g8EVdTyE6LpWXYxYW8GzQKdVf bgwV5gXKkySqW4G3BL5xYtUoWa0QU1o7BLaZ9kIGfy+AcUyiIWMLIhPLaZC+6imwU990 dyiIUyRKfTGdA6Dx24socgQhK4eH3uryl+wW3nilowBnpB+8A5k6IymH7BASqBEEMTSN bAj//Q8syoThFdqAsHFzDmMwpgl77bZ8Hwim+RcFs4XUirXZ2rGUnd5pq+0JKUQxUNzd dswBWbPEKEUInzCYkSRKFMn7Zz3v3AqzSHET6uiGPFx7t/HsZaIq1Mo0hcFSTc7NrYYy u0Ng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=HI4q73IG+mRuqdKI+/sZeNi41z3wIZxcUf28STytLfU=; b=XupvAWB1lm1G490OAXhLxCY3UGhC70TuziJy725u/KQFxUO3o0Agp707bZGj4i+cEI QeYLnwhAkRfWhqFwtUDeZD14B86mFZgq1NUc6S/inz751uQdXLoami7kTCzKHfBCO+Bf PrgoXCfzv3GU/w1s40N7BEcHyXC5K/nok5WfoDW5y7cG5C9NmZ1MYd5vGaBzv6pLHGzF 5Ny4VtBdRftKcnOf5WXaTaG3qJ+gv67AvoQEi4dYdE/8wAf66KVadmp+rWGx6bQNlVXn L3YaFE6zZO88vseKCpg5BZXpmvWCYUV9vzp1jMfNSDsJAgLk9SnH9UCvo+CTOsqU/7ZM xizA== X-Gm-Message-State: ABuFfogiwB8q4BVli0o/Ws1WXl6rwTKskZCPFD61Kg1A6VYRj7K5j7Tj 2O97zsDiRTEg5R7VWh08JjLPJIeeaP/yIx1c6RQ= X-Received: by 2002:a25:6788:: with SMTP id b130-v6mr182661ybc.84.1538165987277; Fri, 28 Sep 2018 13:19:47 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a5b:505:0:0:0:0:0 with HTTP; Fri, 28 Sep 2018 13:19:46 -0700 (PDT) In-Reply-To: References: <74fb6ce22f62e0fb48b91ca9918b74cedbcecaf1.1538096323.git.luto@kernel.org> <20180928103726.07761672@mschwideX1> <0B38810F-3E22-45A8-9D5D-EDEABD214148@amacapital.net> <20180928165321.0ddaf948@mschwideX1> From: Max Filippov Date: Fri, 28 Sep 2018 13:19:46 -0700 Message-ID: Subject: Re: [PATCH] futex: Set USER_DS for the futex_detect_cmpxchg() test To: Andy Lutomirski Cc: Martin Schwidefsky , Thomas Gleixner , Geert Uytterhoeven , Andrew Lutomirski , X86 ML , Peter Zijlstra , Ingo Molnar , Darren Hart , LKML , linux-s390 , Heiko Carstens , fthain@telegraphics.com.au Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 28, 2018 at 11:02 AM, Andy Lutomirski wrote: > There may be a much nicer solution. Unless I missed something, only > mips and xtensa even have the possibility of cmpxchg being missing. > We could just make those arches supply a futex-detecting helper. In case of xtensa availability of cmpxchg is known at build time. -- Thanks. -- Max