Return-Path: <linux-kernel-owner+w=401wt.eu-S1760243AbXE1Bzj@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1760243AbXE1Bzj (ORCPT <rfc822;w@1wt.eu>);
	Sun, 27 May 2007 21:55:39 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756001AbXE1Bzb
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Sun, 27 May 2007 21:55:31 -0400
Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:40782 "EHLO
	fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755728AbXE1Bzb (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sun, 27 May 2007 21:55:31 -0400
Date: Mon, 28 May 2007 10:54:43 +0900
Message-ID: <87bqg5emqk.wl%takeuchi_satoru@jp.fujitsu.com>
From: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
       Srivatsa Vaddagiri <vatsa@in.ibm.com>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Nathan Lynch <nathanl@austin.ibm.com>,
       Joel Schopp <jschopp@austin.ibm.com>, Ashok Raj <ashok.raj@intel.com>,
       Heiko Carstens <heiko.carstens@de.ibm.com>,
       Gautham R Shenoy <ego@in.ibm.com>,
       Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Subject: CPU hotplug: system hang on CPU hot remove during `pfmon --system-wide'
User-Agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8
 (=?ISO-8859-4?Q?Shij=F2?=) APEL/10.6 Emacs/21.4 (i486-pc-linux-gnu)
 MULE/5.0 (SAKAKI)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1595
Lines: 55

Hi,

I found a bug on CPU hotplug. If `pfmon --system-wide' is running,
CPU hot remove causes system hang. On the other hand, CPU hot add
during that command seems to work fine.

I detected this problem on my ia64 box, and I don't know that this
problem is also occur on any arch or freezer based CPU hotplug.
Since I'm investigating this problem now, I'm glad if someone
reports the test result on other arch or freezer.

Currently I don't know anything about the cause of this problem.

How To Reproduce
================

Assuming you have two terminal, named term A and term B.

1) execute pfmon from term A

$ pfmon --system-wide
<press ENTER to stop session>

2) issue CPU hot remove from term B

# echo 0 >/sys/devices/system/cpu/cpu1/online

3) Press enter from term B

Expected Result
===============

Succeed to offline CPU

Actual Result
=============

System hang occurs and there are the following messages on serial console.

-------------------------------------------------------------------------------
CPU0                       1925600 CPU_CYCLES
CPU1 could not stop monitoring, CPU may be offline, check results
pfm_write_old_pmds error [3] Device or resource busy
pfmon_read_pmds error Device or resource busy
CPU1 read_results error
-------------------------------------------------------------------------------

Thanks,

Satoru
-
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/