Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755780Ab3ICOps (ORCPT ); Tue, 3 Sep 2013 10:45:48 -0400 Received: from mail-la0-f54.google.com ([209.85.215.54]:33721 "EHLO mail-la0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754058Ab3ICOpq (ORCPT ); Tue, 3 Sep 2013 10:45:46 -0400 MIME-Version: 1.0 In-Reply-To: <00000140e4373c9e-ea44cb7f-985f-4d33-86ed-cfd54ec7327b-000000@email.amazonses.com> References: <20130828193457.140443630@linux.com> <00000140c67817eb-b582280a-f059-499f-a24c-a11f3d59b86e-000000@email.amazonses.com> <20130829075818.GW10002@twins.programming.kicks-ass.net> <20130829100143.GA29672@gmail.com> <00000140cb02576f-e106763c-d382-4b66-bb85-d7a9cb266b81-000000@email.amazonses.com> <20130829173256.GB6276@home.goodmis.org> <00000140cb49bdde-1279ffb0-5c49-400d-970c-a481d527e98a-000000@email.amazonses.com> <20130829143053.3fc2caa8@gandalf.local.home> <00000140e4373c9e-ea44cb7f-985f-4d33-86ed-cfd54ec7327b-000000@email.amazonses.com> Date: Tue, 3 Sep 2013 16:45:45 +0200 Message-ID: Subject: Re: [gcv v3 06/35] scheduler: Replace __get_cpu_var uses From: Frederic Weisbecker To: Christoph Lameter Cc: Steven Rostedt , Ingo Molnar , Peter Zijlstra , Tejun Heo , akpm@linuxfoundation.org, Ingo Molnar , linux-arch@vger.kernel.org, LKML , Thomas Gleixner Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1285 Lines: 27 2013/9/3 Christoph Lameter : > On Thu, 29 Aug 2013, Steven Rostedt wrote: > >> How many places use the this_cpu_*() without preemption disabled? I >> wouldn't think there's many. I never complained about another variant, >> so you need to ask those that have. The tough question for me is what >> that variant name should be ;-) > > Tried to add preemption checks but the basic issue is that many of the > checks themselves use this_cpu_ops. percpu.h is very basic to the > operation of fundamental primitives for preempt etc. Use of a BUG_ON needs > a seris of includes in percpu.h that cause more trouble. > > If I switch __this_cpu ops to check for preemption then the logic for > preemption etc must use the raw_this_cpu ops. IIUC the issue is that preempt debug checks themselves use per cpu operations that can result in preempt debug checks? Hence a recursion. Do you have an example of that? Also in this case this must be fixed anyway given the checks that already exist in smp_processor_id(), __get_cpu_var(), ... -- 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/