So I'm studying operating systems, and the theory of multi-tasking.

Our last lecture was about semaphores - a really cool idea.

Obviously, they have their problems and that's what I'm getting annoyed by now. The big risk is locking the whole system by having the semaphore code ordered incorrectly but what is the general rule to make sure you've got the semaphores the right way around?

Our lecturer hinted that there may be a question on it in the exam, but I can't seem to find a rule on which way to order the semaphores????

I presume your reading a book by Tanenbaum while doing this module? He probably explains it very well (if not, try your library for an Operating Systems, they are all probably by him).

My damned uni doesn't do an OS module, so I'm wading through it myself, Tanenbaum does very good books on the subject, but I've not had time to do much reading...

Yeah TB is amasing!

The material I'm using does give a few examples of errors with how they can be corrected, but I'm struggling to find a rule from them.

Now the book I would have recomended is Operating System Concepts by Silberschatz, Galvin & Gagne (Lots of dinosaurs) but then that's just the OS book I've read.