Re: [Xen-devel] [PATCH] arm/acpi: Fix the deadlock in function vgic_lock_rank()

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 01/06/16 10:54, Stefano Stabellini wrote:
> > spin_is_locked does not work as you expect. The function will not tell you if
> > the lock was taken by the current CPU, but if the lock was taken by *a* CPU.
> >
> > It would be possible to have CPU A calling this function and have CPU B with
> > the lock taken. So the data structure would be accessed by 2 CPUs
> > concurrently, which is unsafe.
> Damn, you are right. I don't think we have a spin_lock function which
> tells us if the spin_lock was taken by us.
Unfortunately not.

> The only other option I see would be duplicating route_irq_to_guest and
> gic_route_irq_to_guest, introducing a second version of those functions
> which assume that the rank lock was already taken. Very very ugly. I'll
> just revert the commit and wait for better patches from Shannon.
I am working on a patch series to decouple IRQ configuration and 
routing. It should be ready soon.
Regards,

--
Julien Grall

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