Concurrency problems

In this repo I tried to solve 4 classical concurrency programming problems using Linux system calls and basic synchronization structures like mutexes and semaphores in C. All programs have adjustable parameters like number of producers or producers in the Producer-consumer problem, or maximum time of philosopher eating in Dining philosophers problem.

Below are formulations of each problems:

Producer-consumer problem

• The producer generates data items and puts them into the buffer with a limited capacity.
• The consumer takes the items, thereby removes them from the buffer, leaving free space.
• At the producer side, the synchronisation problem appears when the buffer is full, so there is no free space for a new (already produced) item.
• At the consumer side, the synchronisation problem appears when the buffer is empty, so there is no item to be taken

Reader-writer problem

• Two kinds of users (readers and writers) use a shared resource (reading room or library).
• Readers can use the resource in the shared mode, i.e. multiple readers can occupy the reading room at the same time.
• Writers can use the resource in the exclusive mode, i.e. a writer in the reading room excludes other users (both readers and other writers).
• The problem of synchronisation is to prevent the user from entering the reading room in an incompatible mode.

Dining philosophers problem

Five philosophers sit at a round table with a bowl of spaghetti.

• Each philosopher alternately thinks and eats.
• To eat spaghetti the philosopher needs two forks.
• Forks are placed between each pair of adjacent philosophers, so each of the five forks is shared by two philosophers.
• Each fork is used by at most one philosopher at a time, therefore at most one of two neighbours can eat.
• The problem is to synchronise the philosopher so that each of them can eventually eat something, avoiding unnecessary waiting and following the rules of access to forks.

Sleeing barbers problem - TODO

There is a barbershop with p chairs in the waiting room and n barber chairs used by barbers to serve their customers.

• When there is a customer in the shop, they wake up a barber, then the barber finds a free chair to serve the customer.
• If no free barber chair is available, the customer takes a seat in the waiting room.
• If there is no free chair in the waiting room, the customer leaves the barbershop.
• The issue here is to synchronise the barbers and the customers, i.e. to lead to the simultaneous state of a barber serving a client and the client being served by the barber.