Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756368AbYJQMpb (ORCPT ); Fri, 17 Oct 2008 08:45:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756233AbYJQMox (ORCPT ); Fri, 17 Oct 2008 08:44:53 -0400 Received: from rv-out-0506.google.com ([209.85.198.225]:53693 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756226AbYJQMow (ORCPT ); Fri, 17 Oct 2008 08:44:52 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=DVgCON3Q2tZnobXYvViLq+YbeqwaUcKVHb9Ak0EFM5jS8BlE3IiLBlu9p1+cYYSpem S/EsgcwGQ/2zobf1WNQ/vAAbGzSQplHUi2tXR4ywMs1Gcsmenv4jw6nbVMr++EbgB/7D SsyYKtHU26qeH7Oja5JCmIdJFR6YJ7pHjtUmY= Message-ID: Date: Fri, 17 Oct 2008 20:44:51 +0800 From: "Lai Jiangshan" To: "Alexey Dobriyan" Subject: Re: [PATCH] x86/proc: fix /proc/cpuinfo cpu offline bug Cc: "Lai Jiangshan" , "Ingo Molnar" , linux-kernel@vger.kernel.org In-Reply-To: <20081017114132.GA18994@x200.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <48F852FD.7070108@cn.fujitsu.com> <20081017114132.GA18994@x200.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2437 Lines: 72 On Fri, Oct 17, 2008 at 7:41 PM, Alexey Dobriyan wrote: > On Fri, Oct 17, 2008 at 04:55:25PM +0800, Lai Jiangshan wrote: >> In my test, I found that if a cpu has been offline, >> the next cpus may not be shown in the /proc/cpuinfo. >> >> trivially reproduce this bug: >> >> 1) add these lines in the end of show_cpuinfo() >> if (m->size - m->count - 20 > 0) >> seq_printf(m, "%*s", (int)(m->size - m->count - 20), "show bug\n"); > > What is it? > > Can you just show wrong /proc/cpuinfo ? > > Can someone with at least 4-way box please do so? this is not wrong /proc/cpuinfo, this is an enlarged /proc/cpuinfo this trivial example just use "show bug\n" as the enlarged content. if you boot your machine with enough cpu, your /proc/cpuinfo have been enlarged too, please use this: #!/bin/sh nr_cpus=16 # i386 for ((i=1; i /sys/devices/system/cpu/cpu$i/online cpus=$(grep processor /proc/cpuinfo | wc -l) (( cpus == nr_cpus -1 )) || break; # bug eccur echo 1 > /sys/devices/system/cpu/cpu$i/online done cat /proc/cpuinfo # it shows this bug. Lai > >> 3) offline cpu#1 >> 4) cat /proc/cpuinfo >> cpu#2 and cpu#3 .... cannot be shown in /proc/cpuinfo > >> --- 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); >> } > -- > 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/ > -- 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/