The dining philosophers problem is a very famous and interesting problem used to demonstrate the concept of deadlock.

To understand what the dining philosophers problem actually is, you can refer this blog:

The Dining Philosopher’s problem

The dining philosopher’s problem is a real life demonstration of the resource sharing problem in operating systems.

anushkaa5000.medium.com

Here, I am going to explain the solution to this problem using the concept of semaphores in C. Here’s the program:

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<semaphore.h>
#include<unistd.h>

sem_t room;
sem_t chopstick[5];

void * philosopher(void *);
void eat(int);
int main()
{
	int i,a[5];
	pthread_t tid[5];

	sem_init(&room,0,4);

	for(i=0;i<5;i++)
		sem_init(&chopstick[i],0,1);

	for(i=0;i<5;i++){
		a[i]=i;
		pthread_create(&tid[i],NULL,philosopher,(void *)&a[i]);
	}
	for(i=0;i<5;i++)
		pthread_join(tid[i],NULL);
}

void * philosopher(void * num)
{
	int phil=*(int *)num;

	sem_wait(&room);
	printf("\nPhilosopher %d has entered room",phil);
	sem_wait(&chopstick[phil]);
	sem_wait(&chopstick[(phil+1)%5]);

	eat(phil);
	sleep(2);
	printf("\nPhilosopher %d has finished eating",phil);

	sem_post(&chopstick[(phil+1)%5]);
	sem_post(&chopstick[phil]);
	sem_post(&room);
}

void eat(int phil)
{
	printf("\nPhilosopher %d is eating",phil);
}
/* BY - ANUSHKA DESHPANDE */

#threads #deadlock #semaphore #c-program #dining-philosophers #c++