mutex lock priority

Question

In multithreading (2 thread) program, I have this code:

while(-1)
{
    m.lock();

    (...)

    m.unlock();
}

m is a mutex (

Answer 1

There are no guarantees provided by C++ or underlying OS.

However, there is some reasonable degree of fairness determined by the thread arrival time to the critical region (mutex in this case). This fairness can be expressed as statistical probability, but not a strict guarantee. Most likely this choice will be down to OS execution scheduler, which will also consider many other factors.