Re: [Xen-devel] [Patch] avoid deadlock during console output

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>]

Juergen Gross wrote:
> Keir Fraser wrote:
>> On 06/03/2009 08:46, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxxxxxxx>
>> 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
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