I think these tests could be more extensive. For example:
* What happens if you try to perform a non-exclusive wait while an exclusive wait is in progress? i.e. the inverse of the test added here.
* Can we verify that exclusive waits are specific to a given socket (i.e. you can simultaneously do an exclusive wait on two different sockets?)
* Can we test that exclusive waits apply if two unequal sets overlap?
* Can you do an exclusive wait on the same socket from two different threads?
There's also a part of me that would like to know what can possibly be the point of this API; it's hard to even think of what "reasonable" behaviour is otherwise. Do you happen to know?
My best guess is that it's meant to explicitly interrupt poll requests somehow (what, I/O cancellation wasn't good enough for them?), in which case it'd be good to explicitly confirm or refute that the "exclusive" poll really does act like a normal poll, and doesn't e.g. return immediately.