IIRC Simon (?) posted some time query about whether he should
commit his in-kernel semaphore implementation. Perhaps that
code can be useful for you? 

Manuel Bouyer wrote:
> On Thu, Mar 14, 2002 at 01:00:56PM +0900, seong@etri.re.kr wrote:
> > I want to use a count semaphore.
> 
> Hum, a semaphore could block. You have to be very carefull with this (you
> don't want to sleep if you're in an interrupt routine for exanple).
> 
> 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.

Jaromir
-- 
Jaromir Dolecek <jdolecek@NetBSD.org> http://www.NetBSD.org/Ports/i386/ps2.html
-=- We should be mindful of the potential goal, but as the tantric    -=-
-=- Buddhist masters say, ``You may notice during meditation that you -=-
-=- sometimes levitate or glow.   Do not let this distract you.''     -=-