From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754339Ab0K2Sdi (ORCPT ); Mon, 29 Nov 2010 13:33:38 -0500 Received: from mail.openrapids.net ([64.15.138.104]:56981 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751049Ab0K2Sdh (ORCPT ); Mon, 29 Nov 2010 13:33:37 -0500 Date: Mon, 29 Nov 2010 13:33:33 -0500 From: Mathieu Desnoyers To: Christoph Lameter Cc: akpm@linux-foundation.org, Pekka Enberg , linux-kernel@vger.kernel.org, Eric Dumazet , Tejun Heo Subject: Re: [thisops uV2 04/10] x86: Support for this_cpu_add,sub,dec,inc_return Message-ID: <20101129183333.GA25610@Krystal> References: <20101126210937.383047168@linux.com> <20101126210951.303044608@linux.com> <20101127150015.GE15365@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://www.efficios.com X-Operating-System: Linux/2.6.26-2-686 (i686) X-Uptime: 13:32:25 up 5 days, 23:35, 4 users, load average: 1.00, 1.02, 1.01 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Christoph Lameter (cl@linux.com) wrote: > On Sat, 27 Nov 2010, Mathieu Desnoyers wrote: > > > > +/* > > > + * Add return operation > > > + */ > > > +#define percpu_add_return_op(var, val) \ > > > +({ \ > > > + typedef typeof(var) pao_T__; \ > > > + typeof(var) pfo_ret__ = val; \ > > > + if (0) { \ > > > + pao_T__ pao_tmp__; \ > > > + pao_tmp__ = (val); \ > > > + (void)pao_tmp__; \ > > > + } \ > > > > OK, I'm dumb: why is the above needed ? > > Ensure that the compiler agrees that *var and val are compatible. Taken > over from percpu_add_op(). Isn't that the purpose of __builtin_types_compatible_p(t1, t2) ? Mathieu -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com