From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752550AbbKKTBv (ORCPT ); Wed, 11 Nov 2015 14:01:51 -0500 Received: from shards.monkeyblade.net ([149.20.54.216]:50116 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751350AbbKKTBu (ORCPT ); Wed, 11 Nov 2015 14:01:50 -0500 Date: Wed, 11 Nov 2015 14:01:47 -0500 (EST) Message-Id: <20151111.140147.946865774411167562.davem@davemloft.net> To: alexei.starovoitov@gmail.com Cc: peterz@infradead.org, 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 From: David Miller In-Reply-To: <20151111181132.GA90947@ast-mbp.thefacebook.com> References: <20151111.123548.1039494689070388545.davem@davemloft.net> <20151111175741.GR17308@twins.programming.kicks-ass.net> <20151111181132.GA90947@ast-mbp.thefacebook.com> X-Mailer: Mew version 6.6 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 11 Nov 2015 11:01:49 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexei Starovoitov Date: Wed, 11 Nov 2015 10:11:33 -0800 > bpf_xadd was never meant to be __sync_fetch_and_add equivalent. > From the day one it meant to be atomic_add() as kernel does it. +1 > I did piggy back on __sync in the llvm backend because it was the quick > and dirty way to move forward. > In retrospect I should have introduced a clean intrinstic for that instead, > but it's not too late to do it now. user space we can change at any time > unlike kernel. +1