>There is not semaphore primitive in the kernel, as far as I know.
>If this is really what you want you'll have to implement it using locking
>primitives.

I've implemented kernel semaphors - but never committed them.
I was using them to help coordinate sparc-MP, but the real problem
lay elsewhere and simpler coordination methods have since been
used for the purpose.  So kern_sem.c is in my tree, I can commit it 
if someone has a need - supports sleeping and spinning versions of
the wait operations as well as taking/releasing multiple "counts" at
the same time.

--sjg