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xen-devel
Re: [Xen-devel] RE: event delay issue on SMP machine when xen0 is SMPena
On 9 Dec 2005, at 08:59, Tian, Kevin wrote:
I have a question on the following function, why l1 is updated only
one
time, while l2 is updated in each loop? I think they should handle in
the same way. Anyway, in current code, l2 &= ~(1UL << l2i); is not
needed.
Does that mean in the middle of processing l2, some bits previously
active may become inactive due to unmasked by other vcpus? So
conservative check in each loop may be necessary. ;-)
You can reenter evtchn_do_upcall() on the same CPU from within an IRQ
handler that does not specify SA_INTERRUPT. It will then handle all the
pending l2's and the saved l2 in your outer stack activation is now
stale. You then end up double-executing IRQs occasionally which I think
we found to be a bad thing in a few cases.
-- Keir
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