Okay, consider a multi-threaded program. These programs have multiple threads running on multiple cores. Sometimes you want to coordinate the execution of multi

Okay, consider a multi-threaded program. These programs have multiple threads running on multiple cores. Sometimes you want to coordinate the execution of multiple threads in such programs. A common example is when a thread is in a "critical section" where it is only safe for one thread to access/modify state. Sometimes threads will have to wait for each other. This is where the futex comes in. Instead of the thread to wait while using the processor it can tell the OS that it needs to wait for this futex to become free. The OS will then suspend the thread and find another one to schedule in its place.