Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755139AbaKRUxi (ORCPT ); Tue, 18 Nov 2014 15:53:38 -0500 Received: from mail-vc0-f171.google.com ([209.85.220.171]:44048 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754237AbaKRUxf (ORCPT ); Tue, 18 Nov 2014 15:53:35 -0500 MIME-Version: 1.0 In-Reply-To: <20141118172644.26303.37688.stgit@ahduyck-server> References: <20141118172644.26303.37688.stgit@ahduyck-server> Date: Tue, 18 Nov 2014 12:53:34 -0800 X-Google-Sender-Auth: DZJIX3YjnVScXEKYANvo-VOHh-c Message-ID: Subject: Re: [PATCH v4 0/4] Add lightweight memory barriers for coherent memory access From: Linus Torvalds To: Alexander Duyck Cc: "linux-arch@vger.kernel.org" , Network Development , Linux Kernel Mailing List , Mathieu Desnoyers , Peter Zijlstra , Benjamin Herrenschmidt , Heiko Carstens , Ingo Molnar , Michael Neuling , Russell King - ARM Linux , donald.c.skidmore@intel.com, matthew.vick@intel.com, Geert Uytterhoeven , Jeff Kirsher , Francois Romieu , Paul McKenney , nic_swsd@realtek.com, Will Deacon , Michael Ellerman , Tony Luck , Oleg Nesterov , Martin Schwidefsky , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , David Miller Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 18, 2014 at 9:28 AM, Alexander Duyck wrote: > These patches introduce two new primitives for synchronizing cache coherent > memory writes and reads. These two new primitives are: > > coherent_rmb() > coherent_wmb() So I'm still not convinced about the name. I don't hate it, but if you ever want to do "read_acquire", then that whole "coherent_" thing does make for a big mouthful. I don't see why "dma" isn't simpler and more to the point, and has the advantage of lining up (in documentation etc) with "smp". Why would you ever use "coherent_xyz()" on something that isn't about dma? If it's cache-coherent memory without DMA, you'd use "smp_xyz()", so I really do prefer that whole "dma-vs-smp" issue, because it talks about what is actually the important issue. All sane memory is coherent, after all (and if it isn't, you have other issues than memory ordering). Linus -- 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/