Re: [Xen-devel] [PATCH v9 12/12] xen/arm: gic_events_need_delivery and irq priorities

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 18 Jun 2014, Julien Grall wrote:
> On 06/18/2014 11:36 AM, Ian Campbell wrote:
> > AIUI there is no relationship here with "xen/arm: make accesses to
> > desc->status flags atomic" which fixes an issue which already present
> > before this series.
> 
> The error was not really there before. We were "safe" because the flags
> were cleared before EOIing the IRQ.
> 
> Here, we are clearing after EOIing (it has been made by the guest). So
> this race condition can happen more often.

However considering that when IRQ_GUEST is set, IRQ_INPROGRESS is only
read by irq.c, I think the window for errors is extremely small.

That doesn't mean we should expose ourselves to risks, so I still
recommend we apply "make accesses to desc->status flags atomic".

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