From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753148AbaAQPhS (ORCPT ); Fri, 17 Jan 2014 10:37:18 -0500 Received: from qmta05.emeryville.ca.mail.comcast.net ([76.96.30.48]:47536 "EHLO qmta05.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752155AbaAQPhN (ORCPT ); Fri, 17 Jan 2014 10:37:13 -0500 Message-Id: <20140117151836.033743660@linux.com> Date: Fri, 17 Jan 2014 09:18:28 -0600 From: Christoph Lameter To: Tejun Heo Cc: akpm@linuxfoundation.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Thomas Gleixner Subject: [PATCH 16/41] modules: Use raw_cpu_write for initialization of per cpu refcount. References: <20140117151812.770437629@linux.com> Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=preempt_module Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Patch depends on another patch in this series that introduces raw_cpu_ops] The initialization of a structure is not subject to synchronization. The use of __this_cpu would trigger a false positive with the additional preemption checks for __this_cpu ops. So simply disable the check through the use of raw_cpu ops. Trace: [ 0.668066] __this_cpu_write operation in preemptible [00000000] code: modprobe/286 [ 0.668108] caller is __this_cpu_preempt_check+0x38/0x60 [ 0.668111] CPU: 3 PID: 286 Comm: modprobe Tainted: GF 3.12.0-rc4+ #187 [ 0.668112] Hardware name: FUJITSU CELSIUS W530 Power/D3227-A1, BIOS V4.6.5.4 R1.10.0 for D3227-A1x 09/16/2013 [ 0.668113] 0000000000000003 ffff8807edda1d18 ffffffff816d5a57 ffff8807edda1fd8 [ 0.668117] ffff8807edda1d48 ffffffff8137359c ffff8807edda1ef8 ffffffffa0002178 [ 0.668121] ffffc90000067730 ffff8807edda1e48 ffff8807edda1d88 ffffffff813735f8 [ 0.668124] Call Trace: [ 0.668129] [] dump_stack+0x4e/0x82 [ 0.668132] [] check_preemption_disabled+0xec/0x110 [ 0.668135] [] __this_cpu_preempt_check+0x38/0x60 [ 0.668139] [] load_module+0xcfd/0x2650 [ 0.668143] [] ? page_fault+0x22/0x30 [ 0.668146] [] SyS_init_module+0xa6/0xd0 [ 0.668150] [] tracesys+0xe1/0xe6 Acked-by: Ingo Molnar Signed-off-by: Christoph Lameter Index: linux/kernel/module.c =================================================================== --- linux.orig/kernel/module.c 2013-12-02 16:07:51.644582143 -0600 +++ linux/kernel/module.c 2013-12-02 16:07:51.634582418 -0600 @@ -640,7 +640,7 @@ static int module_unload_init(struct mod INIT_LIST_HEAD(&mod->target_list); /* Hold reference count during initialization. */ - __this_cpu_write(mod->refptr->incs, 1); + raw_cpu_write(mod->refptr->incs, 1); return 0; }