[coyotos-dev] PinSets

[Jonathan S. Shapiro]

Oops. I forgot to say how the victim application learns that the limit
has been reduced.

The PinSet can optionally have a "keeper" specified. Whenever the kernel
reduces the limit, it posts an event to this keeper.

Note that this event is stateless -- the keeper must have external means
to figure out which PinSet went wrong. The problem is that the kernel
cannot permit the limit reduction to be blocked by an unavailable
keeper. In light of this, a posted event is the best we can do. Posted
events are only "prompt" because they do not carry any state.