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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 114DFC43381 for ; Tue, 26 Feb 2019 15:04:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB9BA217F9 for ; Tue, 26 Feb 2019 15:04:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727506AbfBZPEk (ORCPT ); Tue, 26 Feb 2019 10:04:40 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:54418 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726151AbfBZPEk (ORCPT ); Tue, 26 Feb 2019 10:04:40 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1QF0UVw031147 for ; Tue, 26 Feb 2019 10:04:38 -0500 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0a-001b2d01.pphosted.com with ESMTP id 2qw6bb66ss-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 26 Feb 2019 10:04:37 -0500 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Feb 2019 15:04:29 -0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1QF4S1O14286850 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Feb 2019 15:04:28 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 32B5AB2068; Tue, 26 Feb 2019 15:04:28 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1278EB2065; Tue, 26 Feb 2019 15:04:28 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.188]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 26 Feb 2019 15:04:28 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id BEC1A16C3FCB; Tue, 26 Feb 2019 07:04:27 -0800 (PST) Date: Tue, 26 Feb 2019 07:04:27 -0800 From: "Paul E. McKenney" To: Akira Yokosawa Cc: Peter Zijlstra , Borislav Petkov , Andrea Parri , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Alan Stern , Will Deacon , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , Daniel Lustig Subject: Re: [RFC PATCH] tools/memory-model: Remove (dep ; rfi) from ppo Reply-To: paulmck@linux.ibm.com References: <20190225175517.GK4072@linux.ibm.com> <20190226093009.GS32477@hirez.programming.kicks-ass.net> <20190226104551.GF32534@hirez.programming.kicks-ass.net> <20190226112133.GG32534@hirez.programming.kicks-ass.net> <20190226112521.GH32534@hirez.programming.kicks-ass.net> <20190226113008.GI32534@hirez.programming.kicks-ass.net> <20190226113813.GA14753@zn.tnic> <20190226134906.GG32494@hirez.programming.kicks-ass.net> <20190226142845.GK4072@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19022615-0068-0000-0000-0000039A95F7 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010668; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000281; SDB=6.01166673; UDB=6.00609432; IPR=6.00947278; MB=3.00025748; MTD=3.00000008; XFM=3.00000015; UTC=2019-02-26 15:04:32 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022615-0069-0000-0000-000047A2EDFA Message-Id: <20190226150427.GM4072@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-26_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902260109 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 26, 2019 at 11:56:57PM +0900, Akira Yokosawa wrote: > Hi Paul, > > On Tue, 26 Feb 2019 06:28:45 -0800, Paul E. McKenney wrote: > > On Tue, Feb 26, 2019 at 02:49:06PM +0100, Peter Zijlstra wrote: > >> On Tue, Feb 26, 2019 at 12:38:13PM +0100, Borislav Petkov wrote: > >>> On Tue, Feb 26, 2019 at 12:30:08PM +0100, Peter Zijlstra wrote: > >>>> When I used the argc variant, gcc-8 'works', but with s/argc/1/ it is > >>>> still broken. > >>> > >>> As requested on IRC: > >> > >> What I asked was if you could get your GCC developer friends to have a > >> look at this :-) > > > > Yes, this all is a bit on the insane side from a kernel viewpoint. > > But the paper you found does not impose this; it has instead been there > > for about 20 years, back before C and C++ admitted to the existence > > of concurrency. > > By "it", do you mean the concept of "pointer provenance"? > > I'm asking because the paper's header reads: > > "ISO/IEC JTC1/SC22/WG14 N2311, 2018-11-09" > > Just wanted to make sure. This paper introduces neither pointer provenance nor indeterminate-on-free, but rather proposes modification. These things have been around for a few decades. Thanx, Paul > Thanks, Akira > > > But of course compilers are getting more aggressive, > > and yes, some of the problems show up in single-threaded code. > > > > The usual response is "then cast the pointers to intptr_t!" but of > > course that breaks type checking. > > > > There is an effort to claw back the concurrency pieces, and I would > > be happy to run the resulting paper past you guys. > > > > I must confess to not being all that sympathetic to code that takes > > advantage of happenstance stack-frame layout. Is there some reason > > we need that? > > > > Thanx, Paul > > >