From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752596AbdJDPik (ORCPT ); Wed, 4 Oct 2017 11:38:40 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56678 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752409AbdJDPij (ORCPT ); Wed, 4 Oct 2017 11:38:39 -0400 Date: Wed, 4 Oct 2017 08:38:29 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Steven Rostedt , pmladek@suse.com, sergey.senozhatsky@gmail.com, linux-kernel@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de Subject: Re: [PATCH 3/3] early_printk: Add simple serialization to early_vprintk() Reply-To: paulmck@linux.vnet.ibm.com References: <20170928121823.430053219@infradead.org> <20170928122513.431444176@infradead.org> <20171003182422.025d0a67@gandalf.local.home> <20171004090830.p5kwzu6ex2wimh4v@hirez.programming.kicks-ass.net> <20171004090401.3a5123a6@gandalf.local.home> <20171004141745.GH3521@linux.vnet.ibm.com> <20171004152423.pifhlr72y2uzq63r@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171004152423.pifhlr72y2uzq63r@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17100415-0048-0000-0000-000001EFC23E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007842; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000233; SDB=6.00926416; UDB=6.00466030; IPR=6.00706628; BA=6.00005620; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017391; XFM=3.00000015; UTC=2017-10-04 15:38:31 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17100415-0049-0000-0000-000042C3CC6C Message-Id: <20171004153829.GJ3521@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-04_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-1710040218 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 04, 2017 at 05:24:23PM +0200, Peter Zijlstra wrote: > On Wed, Oct 04, 2017 at 07:17:45AM -0700, Paul E. McKenney wrote: > > If you use READ_ONCE(), then all architectures I know of enforce > > full ordering for accesses to a single variable. (If you don't use > > READ_ONCE(), then in theory Itanium can reorder reads.) Me, I would > > argue for WRITE_ONCE() as well to prevent store tearing. > > Note that the stores are either cmpxchg() or smp_store_release() both of > which imply a WRITE_ONCE(). That works for me! ;-) Thanx, Paul