Hi,
In our context we gonna use it as a lock.
It's a kind of distributed lock that all peers gonna be aware of it's state.
The purpose is to know how much lock is placed, each time a masternode start it is closing a lock and when the masternode stop it open the lock. There will be a limited amount of lock available.
In order to have this distributed and sync through all peers, we will use a block to open and close lock.
Usually mutex are used in multithreading environment to avoid having two threads editing the same variable address at the same time.