Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752565AbbKKSlj (ORCPT ); Wed, 11 Nov 2015 13:41:39 -0500 Received: from casper.infradead.org ([85.118.1.10]:51799 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750781AbbKKSli (ORCPT ); Wed, 11 Nov 2015 13:41:38 -0500 Date: Wed, 11 Nov 2015 19:41:34 +0100 From: Peter Zijlstra To: Alexei Starovoitov Cc: David Miller , will.deacon@arm.com, daniel@iogearbox.net, arnd@arndb.de, yang.shi@linaro.org, linaro-kernel@lists.linaro.org, eric.dumazet@gmail.com, zlim.lnx@gmail.com, ast@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, xi.wang@gmail.com, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, yhs@plumgrid.com, bblanco@plumgrid.com Subject: Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction Message-ID: <20151111184134.GG11639@twins.programming.kicks-ass.net> References: <56436420.9090401@iogearbox.net> <20151111162341.GN9562@arm.com> <20151111172659.GA86334@ast-mbp.thefacebook.com> <20151111.123548.1039494689070388545.davem@davemloft.net> <20151111175741.GR17308@twins.programming.kicks-ass.net> <20151111181132.GA90947@ast-mbp.thefacebook.com> <20151111183128.GS17308@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151111183128.GS17308@twins.programming.kicks-ass.net> 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 Content-Length: 948 Lines: 21 On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > Adding new intrinsic to llvm is not a big deal. I'll add it as soon > > as I have time to work on it or if somebody beats me to it I would be > > glad to test it and apply it. > > This isn't a speed coding contest. You want to think about this > properly. That is, I don't think you want to go add LLVM intrinsics at all. You want to piggy back on the memory model work done by the C/C++11 people. What you want to think about is what the memory model of your virtual machine is and how many instructions you want to expose for that. Concurrency is a right pain, a little time and effort now will safe heaps of pain down the road. -- 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/