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Re: [Xen-devel] [PATCH v2] xen: arm: increase priority of SGIs used as IPIs

Hi Ian,

On 03/17/2014 11:31 AM, Ian Campbell wrote:
> Code such as on_selected_cpus expects/requires that an IPI can preempt a
> processor which is just handling a normal interrupt. Lacking this property can
> result in a deadlock between two CPUs trying to IPI each other from interrupt
> context.
> For the time being there is only two priorities, IRQ and IPI, although it is
> also conceivable that in the future some IPIs might be higher priority than
> others. This could be used to implement a better BUG() than we have now, but I
> haven't tackled that yet.
> Tested with a debug patch which sends a local IPI from a keyhandler, which is
> run in serial interrupt context.
> This should also fix the issue reported by Oleksandr in "xen/arm:
> maintenance_interrupt SMP fix" without resorting to trylock.

Sorry, I didn't notice it before. If you plan to keep the last
paragraph, can you add a link to the patch?


Julien Grall

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