From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752362AbYJ0GOS (ORCPT ); Mon, 27 Oct 2008 02:14:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751246AbYJ0GOL (ORCPT ); Mon, 27 Oct 2008 02:14:11 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:54330 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751133AbYJ0GOK (ORCPT ); Mon, 27 Oct 2008 02:14:10 -0400 Message-ID: <49055BA5.4040702@cn.fujitsu.com> Date: Mon, 27 Oct 2008 14:11:49 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.17 (Windows/20080914) MIME-Version: 1.0 To: Ingo Molnar , Andrew Morton CC: Alexey Dobriyan , Linux Kernel Mailing List Subject: [PATCH resend] x86/proc: fix /proc/cpuinfo cpu offline bug Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In my test, I found that if a cpu has been offline, the next cpus may not be shown in the /proc/cpuinfo. if one read() cannot consume the whole /proc/cpuinfo file, c_start() will be called again in the next read() calls. And *pos has been increased by 1 by the caller(seq_read()). if this time the cpu#*pos is offline, c_start() will return NULL, and the next cpus can not be shown. this fix uses next_cpu_nr(*pos - 1, cpu_online_map) to search the next unshown cpu. the way to reproduce this bug: (cpu#0 cpu#1 cpu#2 must be online before test) step 1) offline cpu#1 step 2) dd ibs=2 if=/proc/cpuinfo now, only cpu#0 's cpuinfo is shown. cpu#2 and cpu#3 .... cannot be shown in /proc/cpuinfo it's a bug. Signed-off-by: Lai Jiangshan --- diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c index a26c480..01b1244 100644 --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -160,14 +160,16 @@ static void *c_start(struct seq_file *m, loff_t *pos) { if (*pos == 0) /* just in case, cpu 0 is not the first */ *pos = first_cpu(cpu_online_map); - if ((*pos) < nr_cpu_ids && cpu_online(*pos)) + else + *pos = next_cpu_nr(*pos - 1, cpu_online_map); + if ((*pos) < nr_cpu_ids) return &cpu_data(*pos); return NULL; } static void *c_next(struct seq_file *m, void *v, loff_t *pos) { - *pos = next_cpu(*pos, cpu_online_map); + (*pos)++; return c_start(m, pos); }