In prison the cafeteria is sometimes referred to as the Chow Hall.
Although some prisoners or inmates just call it the cafeteria but most commonly a prisoner or inmate and even some guards in prison will refer to the prison cafeteria as the chow hall.
So when it's time to eat in prison they may say it's time for the chow hall.
There's a bunch of different slang terms that are used in prisons to refer to different things and when you're a guard or an inmate in prison you'll get used to those slang terms.