From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757196AbbAINuG (ORCPT ); Fri, 9 Jan 2015 08:50:06 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:53663 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbbAINuD (ORCPT ); Fri, 9 Jan 2015 08:50:03 -0500 Date: Fri, 9 Jan 2015 05:49:54 -0800 From: "Paul E. McKenney" To: Davidlohr Bueso Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless accesses with ACCESS_ONCE() Message-ID: <20150109134954.GO5280@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150107173215.GA897@linux.vnet.ibm.com> <1420651953-2651-1-git-send-email-paulmck@linux.vnet.ibm.com> <20150108094102.GD29390@twins.programming.kicks-ass.net> <20150108152230.GL5280@linux.vnet.ibm.com> <1420785714.25454.1.camel@stgolabs.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1420785714.25454.1.camel@stgolabs.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15010913-0013-0000-0000-000007C38AB4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 08, 2015 at 10:41:54PM -0800, Davidlohr Bueso wrote: > On Thu, 2015-01-08 at 07:22 -0800, Paul E. McKenney wrote: > > > Didn't we just obsolete ACCESS_ONCE with that {READ,WRITE}_ONCE stuff? > > > > Indeed we did! But that was after I did this commit back on October 29th. > > > > I am planning a bulk change to READ_ONCE() and ASSIGN_ONCE() either as > > the last patch for 3.20 or as the first one for 3.21. Probably as the > > first for 3.21 to minimize rebasing hassles with any needed 3.20 fixes. > > That reminds me, I think the new conversion for stores will most likely > introduce silly arg bugs: > > - ACCESS_ONCE(a) = b; > + ASSIGN_ONCE(b, a); I was planning to do mine by hand for this sort of reason. Or are you thinking of something more subtle than the case where "b" is an unparenthesized comma-separated expression? Thanx, Paul