Documentation
¶
Overview ¶
This is a simple demonstration of how to solve the Sleeping Barber dilemma, a classic computer science problem which illustrates the complexities that arise when there are multiple operating system processes. Here, we have a finite number of barbers, a finite number of seats in a waiting room, a fixed length of time the barbershop is open, and clients arriving at (roughly) regular intervals. When a barber has nothing to do, he or she checks the waiting room for new clients, and if one or more is there, a haircut takes place. Otherwise, the barber goes to sleep until a new client arrives. So the rules are as follows:
- if there are no customers, the barber falls asleep in the chair
- a customer must wake the barber if he is asleep
- if a customer arrives while the barber is working, the customer leaves if all chairs are occupied and sits in an empty chair if it's available
- when the barber finishes a haircut, he inspects the waiting room to see if there are any waiting customers and falls asleep if there are none
- shop can stop accepting new clients at closing time, but the barbers cannot leave until the waiting room is empty
- after the shop is closed and there are no clients left in the waiting area, the barber goes home
The Sleeping Barber was originally proposed in 1965 by computer science pioneer Edsger Dijkstra.
The point of this problem, and its solution, was to make it clear that in a lot of cases, the use of semaphores (mutexes) is not needed.
Source Files