POSIX threads and fairness (semaphores)

Question

I have created a program in C that creates 2 buffers. The buffer indices hold single characters, \'A\' or \'b\' etc... In order to learn more about multithreading, I creat

Answer 1

The POSIX standard actually says that "the highest priority thread that has been waiting the longest shall be unblocked" only when the SCHED_FIFO or SCHED_RR scheduling policy applies to the blocked thread.

If you're not using one of those two realtime scheduling policies, then the semaphore does not have to be "fair".

Answer 2

Multi-threaded software only makes sense when

1. You have multiple core to play with
2. Some algorithms are easier to program

How do you define fair. Surely it is better if a core has nothing to do then they take on the work. Does it matter if one core never gets a lookin?