From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932210AbdJXNtu (ORCPT ); Tue, 24 Oct 2017 09:49:50 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36370 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723AbdJXNtq (ORCPT ); Tue, 24 Oct 2017 09:49:46 -0400 Date: Tue, 24 Oct 2017 06:49:39 -0700 From: "Paul E. McKenney" To: Ingo Molnar Cc: Johannes Berg , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "will.deacon@arm.com" , "mark.rutland@arm.com" , "snitzer@redhat.com" , "thor.thayer@linux.intel.com" , "viro@zeniv.linux.org.uk" , "davem@davemloft.net" , "shuah@kernel.org" , "mpe@ellerman.id.au" , "tj@kernel.org" , "torvalds@linux-foundation.org" Subject: Re: [PATCH 09/19] net: average: Kill off ACCESS_ONCE() Reply-To: paulmck@linux.vnet.ibm.com References: <20171023210408.GA2930@linux.vnet.ibm.com> <1508792849-3115-9-git-send-email-paulmck@linux.vnet.ibm.com> <1508824691.2639.26.camel@sipsolutions.net> <20171024093412.slvps6vmluzmteru@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171024093412.slvps6vmluzmteru@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17102413-0040-0000-0000-000003B72F09 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007945; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000239; SDB=6.00935788; UDB=6.00471499; IPR=6.00716054; BA=6.00005658; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017688; XFM=3.00000015; UTC=2017-10-24 13:49:43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17102413-0041-0000-0000-000007AC3AE7 Message-Id: <20171024134939.GY3659@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-24_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1710240193 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 24, 2017 at 11:34:13AM +0200, Ingo Molnar wrote: > > * Johannes Berg wrote: > > > On Mon, 2017-10-23 at 21:07 +0000, Paul E. McKenney wrote: > > > From: Mark Rutland > > > > > > For several reasons, it is desirable to use {READ,WRITE}_ONCE() in > > > preference to ACCESS_ONCE(), and new code is expected to use one of the > > > former. So far, there's been no reason to change most existing uses of > > > ACCESS_ONCE(), as these aren't currently harmful. > > > > > > However, for some features it is necessary to instrument reads and > > > writes separately, which is not possible with ACCESS_ONCE(). This > > > distinction is critical to correct operation. > > > > > > It's possible to transform the bulk of kernel code using the Coccinelle > > > script below. However, this doesn't pick up some uses, including those > > > in . As a preparatory step, this patch converts the > > > file to use {READ,WRITE}_ONCE() consistently. > > > > > > At the same time, this patch addds missing includes necessary for > > > {READ,WRITE}_ONCE(), *BUG_ON*(), and ilog2(). > > > > > > ---- > > > virtual patch > > > > > > @ depends on patch @ > > > expression E1, E2; > > > @@ > > > > > > - ACCESS_ONCE(E1) = E2 > > > + WRITE_ONCE(E1, E2) > > > > > > @ depends on patch @ > > > expression E; > > > @@ > > > > > > - ACCESS_ONCE(E) > > > + READ_ONCE(E) > > > ---- > > > > > > Signed-off-by: Mark Rutland > > > Cc: Johannes Berg > > > > Reviewed-by: Johannes Berg > > Thanks! > > > Let me know if you want me to apply this, since I seem to be the > > average.h maintainer :-) > > Would be nice to keep these patches together if possible, so that we can remove > ACCESS_ONCE() - or at least add a build warning. My goal is to remove it. After all, I am the guy who added it. ;-) Thanx, Paul