Five philosophers seated around a table with five chopsticks and five rice bowls. Need two chopsticks to eat rice.
Philosophers alternate between thinking and eating.
Want to grant chopsticks while avoiding both deadlock and starvation. Philosophers 1 and 3 might alternate between eating and thinking, but if they never think at the same time, philosopher 2 goes hungry. How to control access. But multiple reads are ok. 2-21, although the writer could starve if readers keep arriving.