How do I implement my own semaphore in C?

Question

I'm working on solving the Producer/Consumer problem through different methods. The one I'm currently working on involves my own implementation of a semaphore, paired with Peterson's solution to protect the semaphore's down() and up() function calls.

The problem is, I'm working in C, and the only way I can think of creating a semaphore would be to use a struct with function pointers for down() and up(). Is this the right idea?

Answer 1

You will likely want to use some OS-provided or hardware-provided synchronization primitive. Examples include system calls (e.g. Linux's futex call, Windows' EnterCriticalSection), hardware swap calls (e.g. cmpxchg on x86, ldrex/strex on ARM), or library functions which use one of these methods (e.g. pthread_mutex).

Trying to do synchronization without any help from the OS or hardware is likely to be quite difficult.

Answer 2

Check futex, it is a user space syn primitive. But I don't think you're looking for something this much complicated.