Re: [Xen-devel] [PATCH] x86/IO-APIC: refine EOI-ing of migrating level interrupts

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.11.11 at 17:12, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> On 15/11/11 13:14, Jan Beulich wrote:
>> Rather than going through all IO-APICs and calling io_apic_eoi_vector()
>> for the vector in question, just use eoi_IO_APIC_irq().
>>
>> This in turn allows to eliminate quite a bit of other code.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Tested-and-acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> (tested
> via backport to xen-4.1.x)

Now that this is in, could you try (again on the offending system)
whether adding e.g. a WARN_ON(vector != desc->arch.old_vector)
prior to the just added call to eoi_IO_APIC_irq() (but inside the
surrounding if()) would ever trigger (obviously you'd want to make
sure that the code path actually gets executed at all - perhaps
counting and printing the count once in a while would be the easiest
thing to do)?

If it does, we obviously need to stay with passing in vector. If not,
we'd need to do another round of code inspection to determine
whether indeed there's no race when relying on just the stored
data.

Thanks, Jan


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