What is the name of the code section that needs to be protected with a mutex?

The code section that needs to be protected using a mutex is called the "critical section".

This is part of the program where access to or modification of shared resources (such as variables, files) occurs, and concurrent execution of this code by multiple threads can lead to errors or inconsistent states.

Using a mutex guarantees that only one thread executes the critical section at any given time, preventing race conditions.