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

To: "Keir Fraser" <keir.xen@xxxxxxxxx>
Subject: Re: [Xen-devel] xen kernel crash at boot since 23598:b24018319772
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Fri, 01 Jul 2011 11:02:40 +0100
Cc: Christoph Egger <Christoph.Egger@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
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>>> 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().


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