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 07:18:25 +0100
Message-ID: <49B4B4B1.9060505@fujitsu-siemens.com>
References: <C5D6995D.4493%keir.fraser@eu.citrix.com>
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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))
            {
                spin_unlock_irqrestore(&tasklet_lock, flags);
                BUG();
            }
            list_add_tail(&t->list, &tasklet_list);
        }

Juergen

-- 
Juergen Gross                             Principal Developer
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Fujitsu Siemens Computers         e-mail: juergen.gross@fujitsu-siemens.com
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