Re: [Xen-devel] xen kernel crash at boot since 23598:b2401831977

To:	Jan Beulich <JBeulich@xxxxxxxxxx>
Subject:	Re: [Xen-devel] xen kernel crash at boot since 23598:b24018319772
From:	Keir Fraser <keir.xen@xxxxxxxxx>
Date:	Fri, 01 Jul 2011 11:18:23 +0100
Cc:	Christoph Egger <Christoph.Egger@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
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On 01/07/2011 11:02, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 30.06.11 at 18:33, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
>> Note that domain_spin_lock_irq_desc() has a retry loop for a reason! It
>> knows that pirq-irq mapping may change under its feet, so it needs to
>> re-check the mapping with the desc_lock held, at which point the mapping
>> cannot change *if* it obtained the correct desc_lock in time!
>> 
>> Perhaps pirq_spin_lock_irq_desc() needs a similar retry loop? Perhaps
> 
> Yes. Will send a patch soon.
> 
>> pirq_spin_lock_irq_desc() should never have been forked from
>> domain_spin_lock_irq_desc(), and all callers should simply use the former?
> 
> I'd rather not - the lookup isn't really inexpensive (and doesn't need
> to be re-done on each iteration either), which is why I created the
> clone in the first place. Instead I think that with adding the retry
> loop here, domain_spin_lock_irq_desc() could become a simple
> wrapper around pirq_spin_lock_irq_desc().

Yes please!

 -- Keir

> Jan
> 



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Re: [Xen-devel] xen kernel crash at boot since 23598:b24018319772