Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932266AbZJMCOq (ORCPT ); Mon, 12 Oct 2009 22:14:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758693AbZJMCOq (ORCPT ); Mon, 12 Oct 2009 22:14:46 -0400 Received: from hera.kernel.org ([140.211.167.34]:35785 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757450AbZJMCOp (ORCPT ); Mon, 12 Oct 2009 22:14:45 -0400 Message-ID: <4AD3E23B.8020103@kernel.org> Date: Tue, 13 Oct 2009 11:13:15 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Christoph Lameter CC: linux-kernel@vger.kernel.org, Pekka Enberg , Mel Gorman , Mathieu Desnoyers Subject: Re: [this_cpu_xx V6 3/7] Use this_cpu operations in slub References: <20091007211024.442168959@gentwo.org> <20091007211052.614790286@gentwo.org> <4AD302A8.4010409@kernel.org> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 13 Oct 2009 02:13:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1116 Lines: 28 Christoph Lameter wrote: > On Mon, 12 Oct 2009, Tejun Heo wrote: > >>> - c = get_cpu_slab(s, smp_processor_id()); >>> + c = __this_cpu_ptr(s->cpu_slab); >> Shouldn't this be this_cpu_ptr() without the double underscore? > > Interrupts are disabled so no concurrent fast path can occur. > The only difference between this_cpu_ptr() and __this_cpu_ptr() is the usage of my_cpu_offset and __my_cpu_offset which in turn are only different in whether they check preemption status to make sure the cpu is pinned down when called. The only places where the underbar prefixed versions should be used are places where cpu locality is nice but not critical and preemption debug check wouldn't work properly for whatever reason. The above is none of the two and the conversion is buried in a patch which is supposed to do something else. Am I missing something? -- tejun -- 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/