From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755863AbaIDJdG (ORCPT <rfc822;w@1wt.eu>);
	Thu, 4 Sep 2014 05:33:06 -0400
Received: from mga11.intel.com ([192.55.52.93]:56562 "EHLO mga11.intel.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1755181AbaIDJc3 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 4 Sep 2014 05:32:29 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; 
   d="scan'208";a="381288758"
Date: Thu, 4 Sep 2014 17:34:14 +0800
From: Wanpeng Li <wanpeng.li@linux.intel.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: hpa@zytor.com, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        Borislav Petkov <bp@alien8.de>,
        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
        David Rientjes <rientjes@google.com>,
        Prarit Bhargava <prarit@redhat.com>,
        Steven Rostedt <srostedt@redhat.com>,
        Jan Kiszka <jan.kiszka@siemens.com>, Toshi Kani <toshi.kani@hp.com>,
        linux-kernel@vger.kernel.org, Zhang Yang <yang.z.zhang@intel.com>,
        Wanpeng Li <wanpeng.li@linux.intel.com>
Subject: Re: [PATCH v4] x86, hotplug: fix llc shared map unreleased during
 cpu hotplug
Message-ID: <20140904093414.GA7296@kernel>
Reply-To: Wanpeng Li <wanpeng.li@linux.intel.com>
References: <1406625883-4972-1-git-send-email-wanpeng.li@linux.intel.com>
 <20140904052034.GA29146@gmail.com>
 <20140904085641.GA6311@kernel>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20140904085641.GA6311@kernel>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Ingo,
On Thu, Sep 04, 2014 at 04:56:41PM +0800, Wanpeng Li wrote:
>On Thu, Sep 04, 2014 at 07:20:34AM +0200, Ingo Molnar wrote:
>>
>>* Wanpeng Li <wanpeng.li@linux.intel.com> wrote:
>>
>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
>>> IP: [..] find_busiest_group
>>> PGD 5a9d5067 PUD 13067 PMD 0
>>> Oops: 0000 [#3] SMP
>>> [...]
>>> Call Trace:
>>> load_balance
>>> ? _raw_spin_unlock_irqrestore
>>> idle_balance
>>> __schedule
>>> schedule
>>> schedule_timeout
>>> ? lock_timer_base
>>> schedule_timeout_uninterruptible
>>> msleep
>>> lock_device_hotplug_sysfs
>>> online_store
>>> dev_attr_store
>>> sysfs_write_file
>>> vfs_write
>>> SyS_write
>>> system_call_fastpath
>>> 
>>> Last level cache shared map is built during cpu up and build sched domain 
>>> routine takes advantage of it to setup sched domain cpu topology, however, 
>>> llc shared map is unreleased during cpu disable which lead to invalid sched 
>>> domain cpu topology. This patch fix it by release llc shared map correctly
>>> during cpu disable.
>>
>>Very little is said in this changelog about how the bug was 
>>found, how likely it is to occur for others, what systems are 
>>affected, etc.
>
>This bug can be triggered by hot add and remove large number of xen 
>domain0's vcpus repeated.
>

If I need to send a new version of the patch or you can pick the patch
w/ the updated changelog for me? ;-)

Regards,
Wanpeng Li 

>Regards,
>Wanpeng Li 
>
>>
>>Thanks,
>>
>>	Ingo