[Techtalk] Priority inheritance

coldfire rolick571 at duq.edu
Thu Jan 17 20:45:22 EST 2002

> > For questions like this, it seems like you have to start talking about
> > semaphores and spinlocks and stuff.
> 	Okay, I'm game.  What are those, and how do they work? 

"a semaphore is an integer variable that is accessed only through two
standard atomic operations."  wait and signal.

this definition is quite vague ... basically, a semaphore can be used to
put a process "to sleep" and "wake up" that process at a later time.
spinlocks are semaphores that don't require a context switch when a
process must wait on a lock.  spinlocks are especially usefull in
multiprocessor systems.

basically, semaphores and spinlocks save cpu overhead from processes which
sit in their busy loops to see if it's safe to enter their critical
sections or not ...

if you want more details, let me know ... i didn't want to write a book
here if no one wanted to hear it :)


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