RE: [Xen-devel] [PATCH]: Really disable pirq's

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Yes, seems the startup_irq's return value does not matter, even to
request_irq().

-- Yunhong Jiang

Chris Lalancette <mailto:clalance@xxxxxxxxxx> wrote:
> Jiang, Yunhong wrote:
>> Not sure if the change is a bit over-kill, since enable_pirq is has
void
>> return type, while startup_pirq is "int" return type, with
possibility
>> to fail.
> 
> Thanks for looking!
> 
> This is true, startup_pirq() *could* fail; but if you notice
> in the code, it
> doesn't actually have anything but a "return 0", so it doesn't report
errors
> currently anyway.
> 
>> 
>> For example, in following situation, the startup_pirq may fail : 1)
when
>> startup_pirq again, fail to get free port, 2) if another domain try
to
>> bind the pirq with BIND_PIRQ_WILL_SHARE cleared (like to probing,
will
>> it happen?) between the shutdown_pirq/startup_pirq sequence.
> 
> Yes, you are right, this can happen if another domain is probing.
However,
> I'm not sure that it is any different from when you are calling
->startup()
> for the first time; you will just fail to get the event channel.
Without
> introducing another event channel op (which seems like a LOT of
overkill),
> I'm not aware of another way of asking the HV to mask out that IRQ on
the
> IOAPIC. 
> 
> Chris Lalancette

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