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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Feb 2019 14:28:47 -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 x1QESksT22675630 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Feb 2019 14:28:46 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 15A40B2064; Tue, 26 Feb 2019 14:28:46 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EBE0EB2065; Tue, 26 Feb 2019 14:28:45 +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 14:28:45 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 9E57316C2BF9; Tue, 26 Feb 2019 06:28:45 -0800 (PST) Date: Tue, 26 Feb 2019 06:28:45 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: 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 , Akira Yokosawa , Daniel Lustig Subject: Re: [RFC PATCH] tools/memory-model: Remove (dep ; rfi) from ppo Reply-To: paulmck@linux.ibm.com References: <20190222112128.GA7213@andrea> <20190222130014.GY32494@hirez.programming.kicks-ass.net> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190226134906.GG32494@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19022614-0052-0000-0000-000003911F05 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010668; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000281; SDB=6.01166661; UDB=6.00609424; IPR=6.00947266; MB=3.00025748; MTD=3.00000008; XFM=3.00000015; UTC=2019-02-26 14:28:50 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022614-0053-0000-0000-00005FFA06C1 Message-Id: <20190226142845.GK4072@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-26_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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-1902260105 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 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. 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