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=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 12419CA90AF for ; Wed, 13 May 2020 13:21:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B582204EF for ; Wed, 13 May 2020 13:21:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387527AbgEMNVM convert rfc822-to-8bit (ORCPT ); Wed, 13 May 2020 09:21:12 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:28433 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726001AbgEMNVL (ORCPT ); Wed, 13 May 2020 09:21:11 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-142-s2aarvEZM1aeGjcTCVqdUA-1; Wed, 13 May 2020 14:21:07 +0100 X-MC-Unique: s2aarvEZM1aeGjcTCVqdUA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 13 May 2020 14:21:06 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Wed, 13 May 2020 14:21:06 +0100 From: David Laight To: 'Will Deacon' , Peter Zijlstra CC: Marco Elver , LKML , Thomas Gleixner , "Paul E. McKenney" , Ingo Molnar , Dmitry Vyukov Subject: RE: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Thread-Topic: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen Thread-Index: AQHWKSOwZor7e2JWdEKPvqldyEhGwKil/2ew Date: Wed, 13 May 2020 13:21:06 +0000 Message-ID: <9ba9552bd68a4461bb346dc3bae71d7a@AcuMS.aculab.com> References: <20200511204150.27858-1-will@kernel.org> <20200512081826.GE2978@hirez.programming.kicks-ass.net> <20200512190755.GL2957@hirez.programming.kicks-ass.net> <20200513111057.GN2957@hirez.programming.kicks-ass.net> <20200513123243.GO2957@hirez.programming.kicks-ass.net> <20200513124021.GB20278@willie-the-truck> In-Reply-To: <20200513124021.GB20278@willie-the-truck> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Will Deacon > Sent: 13 May 2020 13:40 > On Wed, May 13, 2020 at 02:32:43PM +0200, Peter Zijlstra wrote: > > On Wed, May 13, 2020 at 01:48:41PM +0200, Marco Elver wrote: > > > > > Disabling most instrumentation for arch/x86 is reasonable. Also fine > > > with the __READ_ONCE/__WRITE_ONCE changes (your improved > > > compiler-friendlier version). > > > > > > We likely can't have both: still instrument __READ_ONCE/__WRITE_ONCE > > > (as Will suggested) *and* avoid double-instrumentation in arch_atomic. > > > If most use-cases of __READ_ONCE/__WRITE_ONCE are likely to use > > > data_race() or KCSAN_SANITIZE := n anyway, I'd say it's reasonable for > > > now. > > I agree that Peter's patch is the right thing to do for now. I was hoping we > could instrument __{READ,WRITE}_ONCE(), but that we before I realised that > __no_sanitize_or_inline doesn't seem to do anything. Could something be done that put the addresses of the instructions into a separate segment and have KASAN check that table before reporting an actual error? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)