Due to code bugs or misbehaving hardware it is possible that we can
receive an interrupt that we have not mapped into a linux irq.  Calling
BUG when that happens is very rude, and if the problem is mild enough
prevents anything else from getting done.

So instead of calling BUG just scream loudly about the problem and
continue running.  We don't have enough knowledge to know which
interrupt triggered this behavior so we don't acknowledge it.  This will
likely prevent a recurrence of the problem by jamming up the works with
an unacknowledged interrupt.

If the interrupt was something important it is quite possible that
nothing productive will happen past this point.  But it is now at least
possible to keep working if the kernel can survive without the interrupt
we dropped on the floor.

Solutions like irqpoll should generally make dropped irqs non-fatal.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>