From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <juergen.gross@fujitsu-siemens.com>
Subject: Re: [Patch] avoid deadlock during console output
Date: Mon, 09 Mar 2009 08:45:49 +0100
Message-ID: <49B4C92D.70004@fujitsu-siemens.com>
References: <C5D6995D.4493%keir.fraser@eu.citrix.com>
	<49B4B4B1.9060505@fujitsu-siemens.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <49B4B4B1.9060505@fujitsu-siemens.com>
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

Juergen Gross wrote:
> Keir Fraser wrote:
>> On 06/03/2009 08:46, "Juergen Gross" <juergen.gross@fujitsu-siemens.com>
>> wrote:
>>
>>> to dump the schedulers run-queues. On my 4-core machine I need only about 5
>>> calls to stop the machine.
>>>
>>> The attached patch solves the problem by avoiding sending the event in
>>> critical paths.
>> Ugly. Instead we can defer the dom0 notification to a tasklet. I'll make a
>> patch for that myself.
> 
> Hmm, do you think your patch is okay?
> tasklet_schedule is taking another lock and uses BUG_ON then...
> I would suggest to modify tasklet_schedule:
> 
>         if ( !t->is_scheduled && !t->is_running )
>         {
>             if (!list_empty(&t->list))
>             {
                  t->is_dead = 1;
>                 spin_unlock_irqrestore(&tasklet_lock, flags);
>                 BUG();
>             }
>             list_add_tail(&t->list, &tasklet_list);
>         }

recursion should be avoided, of course!


Juergen

-- 
Juergen Gross                             Principal Developer
IP SW OS6                      Telephone: +49 (0) 89 636 47950
Fujitsu Siemens Computers         e-mail: juergen.gross@fujitsu-siemens.com
Otto-Hahn-Ring 6                Internet: www.fujitsu-siemens.com
D-81739 Muenchen         Company details: www.fujitsu-siemens.com/imprint.html