Quiz 5 Answers
burt rosenberg
oct 2012

1)

interupts    D     T   N
             |     |   |
            -++----++--+----+-------+----------
              |     |  |-w->|       |
handler       D===> |       |       D====x
                    |       N======x
                    T======x
                    
Timer interrupt T interrupts handling of Disk interrupt, will return
Network interrupt pending while timer interrupt completes
Disk interrupt continues after network interrupt is completed

2)

Non-reentrancy of interrupts - This turned out to be slightly
worded badly. Some responses were very good at explaining what
prevents an interrupt from interrupting itself. 

But reading the question again, this answer was already given
in the context of the question, and although it could have been
phrased better, the question to me is clear - what's so wrong
about an interrupt having to interrupt itself that we have to
go through all this trouble to avoid it?

And that's a very good question, and I continue to hope you will
think about it.

3)

No comments

4)

Work loops was full credit. However, this leaves me to wonder
   why so few such primatives in OSX?