Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752845AbaBJLsZ (ORCPT ); Mon, 10 Feb 2014 06:48:25 -0500 Received: from merlin.infradead.org ([205.233.59.134]:42968 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752684AbaBJLsV (ORCPT ); Mon, 10 Feb 2014 06:48:21 -0500 Date: Mon, 10 Feb 2014 12:48:13 +0100 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Will Deacon , Torvald Riegel , Ramana Radhakrishnan , David Howells , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "torvalds@linux-foundation.org" , "akpm@linux-foundation.org" , "mingo@kernel.org" , "gcc@gcc.gnu.org" Subject: Re: [RFC][PATCH 0/5] arch: atomic rework Message-ID: <20140210114813.GJ9987@twins.programming.kicks-ass.net> References: <20140206185910.GE27276@mudshark.cambridge.arm.com> <20140206192743.GH4250@linux.vnet.ibm.com> <1391721423.23421.3898.camel@triegel.csb> <20140206221117.GJ4250@linux.vnet.ibm.com> <1391730288.23421.4102.camel@triegel.csb> <20140207042051.GL4250@linux.vnet.ibm.com> <20140207074405.GM5002@laptop.programming.kicks-ass.net> <20140207165028.GO4250@linux.vnet.ibm.com> <20140207165548.GR5976@mudshark.cambridge.arm.com> <20140207180216.GP4250@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140207180216.GP4250@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 07, 2014 at 10:02:16AM -0800, Paul E. McKenney wrote: > As near as I can tell, compiler writers hate the idea of prohibiting > speculative-store optimizations because it requires them to introduce > both control and data dependency tracking into their compilers. Many of > them seem to hate dependency tracking with a purple passion. At least, > such a hatred would go a long way towards explaining the incomplete > and high-overhead implementations of memory_order_consume, the long > and successful use of idioms based on the memory_order_consume pattern > notwithstanding [*]. ;-) Just tell them that because the hardware provides control dependencies we actually use and rely on them. Not that I expect they care too much what we do, given the current state of things. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/