> For scheduler activations, a way for the kernel to arrange to call a
> specific userlevel function is needed, as well as passing it
> arguments.

Well, the way to go here is to spawn a new kernel thread for this
purpose, and then have it return into a signal-trampoline-like piece
of userspace code.

Understand how signals are delivered into userland, and you will
understand how to do this.

actually, you could probably start a new thread which starts life with
an appropriate signal posted, where the signal means "one of your
threads just blocked; find something better to do".

						- Bill