From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754792AbbKLPDD (ORCPT ); Thu, 12 Nov 2015 10:03:03 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:37311 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754519AbbKLPDB (ORCPT ); Thu, 12 Nov 2015 10:03:01 -0500 X-IBM-Helo: d03dlp03.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Thu, 12 Nov 2015 07:01:49 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Oleg Nesterov , Boqun Feng , mingo@kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, mhocko@kernel.org, dhowells@redhat.com, torvalds@linux-foundation.org, will.deacon@arm.com, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras Subject: Re: [PATCH 4/4] locking: Introduce smp_cond_acquire() Message-ID: <20151112150149.GY3972@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20151102132901.157178466@infradead.org> <20151102134941.005198372@infradead.org> <20151103175958.GA4800@redhat.com> <20151111093939.GA6314@fixme-laptop.cn.ibm.com> <20151111121232.GN17308@twins.programming.kicks-ass.net> <20151111193953.GA23515@redhat.com> <20151112070915.GC6314@fixme-laptop.cn.ibm.com> <20151112150058.GA30321@redhat.com> <20151112144004.GU3972@linux.vnet.ibm.com> <20151112145013.GB17308@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151112145013.GB17308@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15111215-0009-0000-0000-00000FB1686E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 12, 2015 at 03:50:13PM +0100, Peter Zijlstra wrote: > On Thu, Nov 12, 2015 at 06:40:04AM -0800, Paul E. McKenney wrote: > > I cannot resist suggesting that any lock that interacts with > > spin_unlock_wait() must have all relevant acquisitions followed by > > smp_mb__after_unlock_lock(). > > Ha! that would certainly help here. But it would mean that argh64v8 also > needs to define that, even though that is already RCsc. Maybe. It could also be that arm64 avoids the need somehow, for example via their RCsc behavior. Their memory model is similar to PPC, but not exactly the same. Will? Thanx, Paul