From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756419AbdKNWJG (ORCPT ); Tue, 14 Nov 2017 17:09:06 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:42848 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751736AbdKNWJA (ORCPT ); Tue, 14 Nov 2017 17:09:00 -0500 Date: Tue, 14 Nov 2017 14:08:55 -0800 From: "Paul E. McKenney" To: Mark Rutland Cc: linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH] perf mmap: Convert ACCESS_ONCE() to READ_ONCE() Reply-To: paulmck@linux.vnet.ibm.com References: <20171114103138.9931-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171114103138.9931-1-mark.rutland@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17111422-0056-0000-0000-000003E9D154 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008066; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000240; SDB=6.00945919; UDB=6.00477427; IPR=6.00726216; BA=6.00005690; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00018016; XFM=3.00000015; UTC=2017-11-14 22:08:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17111422-0057-0000-0000-00000820F021 Message-Id: <20171114220855.GE3624@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-14_12:,, 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 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1711140294 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 14, 2017 at 10:31:38AM +0000, Mark Rutland wrote: > Recently there was a treewide conversion of ACCESS_ONCE() to > {READ,WRITE}_ONCE(), but a new use was introduced concurrently by > commit: > > 1695849735752d2a ("perf mmap: Move perf_mmap and methods to separate mmap.[ch] files") > > Let's convert this over to READ_ONCE() so that we can remove the > ACCESS_ONCE() definitions in subsequent patches. > > Signed-off-by: Mark Rutland > Cc: Arnaldo Carvalho de Melo > Cc: Ingo Molnar > Cc: Paul E. McKenney > Cc: Peter Zijlstra Reviewed-by: Paul E. McKenney Woo-hoo! Good to see that your Coccinelle script has already done its magic! ;-) Thanx, Paul > --- > tools/perf/util/mmap.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Hi, > > Would it be possible for this to be taken as a fixup in an upcoming rc? That > way we should be able to remove the ACCESS_ONCE() definitions prior to v4.15. > > Thanks, > Mark. > > diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h > index efd78b827b05..3a5cb5a6e94a 100644 > --- a/tools/perf/util/mmap.h > +++ b/tools/perf/util/mmap.h > @@ -70,7 +70,7 @@ void perf_mmap__read_catchup(struct perf_mmap *md); > static inline u64 perf_mmap__read_head(struct perf_mmap *mm) > { > struct perf_event_mmap_page *pc = mm->base; > - u64 head = ACCESS_ONCE(pc->data_head); > + u64 head = READ_ONCE(pc->data_head); > rmb(); > return head; > } > -- > 2.11.0 >