Re: [Xen-devel] [PATCH 1/2] xen: allow on_selected_cpus with interrupts disabled

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 3 May 2013, Ian Campbell wrote:
> On Fri, 2013-05-03 at 15:58 +0100, Stefano Stabellini wrote:
> > Allow on_selected_cpus with interrupts disabled, use it with care.
> 
> This is a deadlock waiting to happen. Can we not find a way to do cross
> CPU EOI without it? If we can guarantee that we only need to EOI on one
> CPU then does that make a specialised SGI vector more plausible?
> 
> Can the IPI call not be moved outside the lock? i.e. remove it from the
> list under the lock and then IPI outside?

I think it can: after all if the physical IRQ has not beeing EOIed yet,
we cannot receive a second one at this time with ot without the lock
held. 

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