(BTW a lot of thanks for your comments, I've read and understood most of
it, I'll reply in due time - perhaps not until next week, I'll be gone
from this afternoon and until monday).
We cannot always fallback to wait, unfortunately. If irqs are disabled,
you could deadlock between two CPUs each waiting for each others IPI
ack.
So the good question is how to handle the problem. The easiest would be
to return ENOMEM and get rid of the fallback, but the fallback deadlocks
are so far mostly in the theoretical realm since it PROBABLY would not
occur in practice. But still no good enough, so I'm still toying with
ideas on how to make it 100% bullet proof.
--
Jens Axboe
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