From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [RFC PATCH] tools/memory-model: Remove (dep ; rfi) from ppo Date: Tue, 26 Feb 2019 07:04:27 -0800 Message-ID: <20190226150427.GM4072@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> Reply-To: paulmck@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-arch.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 > > > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45404 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726333AbfBZPEo (ORCPT ); Tue, 26 Feb 2019 10:04:44 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1QF01rb029061 for ; Tue, 26 Feb 2019 10:04:42 -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 2qw6g05mvx-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 26 Feb 2019 10:04:39 -0500 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 26 Feb 2019 15:04:33 -0000 Date: Tue, 26 Feb 2019 07:04:27 -0800 From: "Paul E. McKenney" 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: Message-ID: <20190226150427.GM4072@linux.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Message-ID: <20190226150427.MdcQ1q8n8Wer-3p1Aclt1EzJTq8HEG0EA1_Nh3ao9G4@z> 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 > > >