From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [RFC][PATCH 0/5] arch: atomic rework Date: Thu, 20 Feb 2014 10:56:42 -0800 Message-ID: <20140220185642.GY4250@linux.vnet.ibm.com> References: <1392740258.18779.7732.camel@triegel.csb> <1392752867.18779.8120.camel@triegel.csb> <20140220040102.GM4250@linux.vnet.ibm.com> <20140220083032.GN4250@linux.vnet.ibm.com> <20140220181116.GT4250@linux.vnet.ibm.com> <1392921872.18779.10287.camel@triegel.csb> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:50492 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755378AbaBTS4r (ORCPT ); Thu, 20 Feb 2014 13:56:47 -0500 Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 20 Feb 2014 11:56:47 -0700 Content-Disposition: inline In-Reply-To: <1392921872.18779.10287.camel@triegel.csb> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Torvald Riegel Cc: Linus Torvalds , Will Deacon , Peter Zijlstra , Ramana Radhakrishnan , David Howells , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "mingo@kernel.org" , "gcc@gcc.gnu.org" On Thu, Feb 20, 2014 at 07:44:32PM +0100, Torvald Riegel wrote: > xagsmtp3.20140220184514.1789@bldgate.vnet.ibm.com > X-Xagent-Gateway: bldgate.vnet.ibm.com (XAGSMTP3 at BLDGATE) > > On Thu, 2014-02-20 at 10:11 -0800, Paul E. McKenney wrote: > > But yes, the compiler guys would be extremely happy to simply drop > > memory_order_consume from the standard, as it is the memory order > > that they most love to hate. > > > > Getting them to agree to any sort of peep-hole optimization semantics > > for memory_order_consume is likely problematic. > > I wouldn't be so pessimistic about that. If the transformations can be > shown to be always correct in terms of the semantics specified in the > standard, and if the performance win is sufficiently large, why not? Of > course, somebody has to volunteer to actually implement it :) I guess that there is only one way to find out. ;-) Thanx, Paul