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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 96F7BC55186 for ; Wed, 22 Apr 2020 23:54:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AE37206ED for ; Wed, 22 Apr 2020 23:54:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ul4AvjVQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726271AbgDVXyG (ORCPT ); Wed, 22 Apr 2020 19:54:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726021AbgDVXyF (ORCPT ); Wed, 22 Apr 2020 19:54:05 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D060C03C1AA for ; Wed, 22 Apr 2020 16:54:04 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id y25so1977546pfn.5 for ; Wed, 22 Apr 2020 16:54:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9yta31YHLGTtMTc3kimrMC0tNHi4fPt9ZpXXfvJokHE=; b=ul4AvjVQXbGe+67+07L6i6vBhv+ePFHnNv5wOIO5OLBqKwlga7zXiy6xS1d0X/n/tF 6woOlNdImmOPZMJChQsUQyygz5ZseUPmnZAKczKpT7Y7lInJ6k/DDJqqloDP2VpGFDPw OFtrm1ALOx3/hCMPr/YQ3m1N7xm3tLJ/pl95K3DRTQoOWwlka1VKxTJhNX6t7x3uramm 2dyep6SUwSuJ79qzMc80b3OzgAHRlzEcC+sG84d0mATYPxu/tkZ16ivMuXJA1CHS9gCY zZTcPJxWLKTN7QTPUPa2eVcTdjKumsRqOxjD1k+RVCHPaHKtuxR9qW1L8MlMmMCCFv+Y LkDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9yta31YHLGTtMTc3kimrMC0tNHi4fPt9ZpXXfvJokHE=; b=Kp9KRfQHKrk3lixXqxj48TAv5F0eOFUQvn2G+UvzRYqbhXM5f5V9zPyL3fyBW7m92i Ju/4oB+SRzWyt3e/bRnoQYw9oz9/O0oOWU1imRUq+r60WRArg0se2lo7HahS5yxedu+e s7MbLe6DFQRi0Bt6qs7qx3n/L4zl9KuqKL95C94YrVPQyq0tO+5xl7yzcEUOsEjcXdzB Cm076VKjDBNbi7cMVdvbh2I270bOxaiSNysuVtDfEUy3CvRgD7VqjrJLSCv2ZrpJMXFp lwy9n5HgaUSAsKuWi/h1YDL2e7RmnGDRs+w/UJZZ69u6QMg6Ahni6ivTDYh5Si+dDgN1 oGYA== X-Gm-Message-State: AGi0PuZKsoa/fP11CdUM5/jN+JsE4/mAmAoQpuL27VlecfWfzhOhMHno GZY6Zq9c8sDUf9em6CE/uKsWnw== X-Google-Smtp-Source: APiQypIxgD2CWLnytM507AIaoaby+Reth9qe8JpsU5Egogw5Wrog+ZS/v8kJIWI3ShghE5eGkNfP8g== X-Received: by 2002:aa7:8118:: with SMTP id b24mr1011016pfi.321.1587599643609; Wed, 22 Apr 2020 16:54:03 -0700 (PDT) Received: from google.com ([2620:15c:201:2:ce90:ab18:83b0:619]) by smtp.gmail.com with ESMTPSA id d20sm360096pjs.12.2020.04.22.16.54.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2020 16:54:02 -0700 (PDT) Date: Wed, 22 Apr 2020 16:53:56 -0700 From: Sami Tolvanen To: Will Deacon Cc: Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Masami Hiramatsu , Nick Desaulniers , Jann Horn , Miguel Ojeda , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v12 03/12] scs: add support for stack usage debugging Message-ID: <20200422235356.GA128062@google.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20200421021453.198187-1-samitolvanen@google.com> <20200421021453.198187-4-samitolvanen@google.com> <20200422174602.GB3121@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200422174602.GB3121@willie-the-truck> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 22, 2020 at 06:46:02PM +0100, Will Deacon wrote: > > +static void scs_check_usage(struct task_struct *tsk) > > +{ > > + static unsigned long highest; > > + unsigned long used = __scs_used(tsk); > > + unsigned long prev; > > + unsigned long curr = highest; > > + > > + while (used > curr) { > > + prev = cmpxchg(&highest, curr, used); > > I think this can be cmpxchg_relaxed(), since we don't care about ordering > here afaict. Sure, I'll change this in v13. Thanks. Sami