Thread can't count, giving wrong result

Question

I wrote this piece of code

#include       /* Input/Output */
#include      /* General Utilities */
#include            


        

Answer 1

Your 2 threads access a shared resource without protection thus a race conditions apply. The increase operation isn't atomic, so you can actually have something like this in terms of machine operations:

Thread 1                   Thread 2
Load value of cnt        
                           Load value of cnt
Increase value of cnt      
Write value of cnt         Increase value of cnt
                           Write value of cnt

Note, that although both threads have increased the cnt, it was actually increased only by 1. If you want the result to be deterministic, you need to protect the shared resource (cnt), e.g. by locking it prior to access.