Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934789AbcCOMoU (ORCPT ); Tue, 15 Mar 2016 08:44:20 -0400 Received: from [198.137.202.9] ([198.137.202.9]:39273 "EHLO bombadil.infradead.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S932564AbcCOMoH (ORCPT ); Tue, 15 Mar 2016 08:44:07 -0400 Date: Tue, 15 Mar 2016 13:42:44 +0100 From: Peter Zijlstra To: Ingo Molnar Cc: Linus Torvalds , Linux Kernel Mailing List , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Thomas Gleixner , Andrew Morton Subject: Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()' Message-ID: <20160315124244.GX6344@twins.programming.kicks-ass.net> References: <20160314123200.GA15971@gmail.com> <20160315093245.GA7943@gmail.com> <20160315105008.GT6344@twins.programming.kicks-ass.net> <20160315120835.GA3232@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160315120835.GA3232@gmail.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 Content-Length: 1048 Lines: 24 On Tue, Mar 15, 2016 at 01:08:35PM +0100, Ingo Molnar wrote: > * Peter Zijlstra wrote: > > > On Tue, Mar 15, 2016 at 10:32:45AM +0100, Ingo Molnar wrote: > > > 2) its naming sucks. "fetch_or()" does not really signal that it's a > > > fundamentally atomic operation, nor what API family it belongs to. > > > > I disagree there, the fetch-$op naming is widely used for atomic > > operations that return the previous value. See for example the C/C++11 > > atomic ops. > > The problem I see is that we don't really have the fetch_*() naming in the kernel > right now, while we do have the xchg_*() naming. The latter is 'obviously' an > atomic operation - while 'fetch' could be anything. We don't have xchg_*() naming, we have xchg() and that's about it. And yes, people know xchg() is an atomic op. But 'fetch (and) or' is also atomic, it has to be, it needs to do 2 operations in 1. Furthermore, the relevant wikipedia page is: https://en.wikipedia.org/wiki/Fetch-and-add So the naming is widely established.