Answered: C Code. Dining Philosopher’s problem is…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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C Code. Dining Philosopher’s problem is a famous problem in OS. A deadlock may happen when all philosophers want to start eating at the same time and pick up one chopstick and wait for the other chopstick. We can use semaphores to simulate the availability of chopsticks.

To prevent the deadlock:

a) Use an asymmetric solution: an odd-numbered philosopher picks up first the left chopstick and then the right chopstick. Even-numbered philosopher picks up first the right chopstick and then the left chopstick.

The following program can lead to a deadlock. Based on the program, please implement the above solution to prevent the deadlock.

#include<stdio.h>
#include<semaphore.h>
#include<pthread.h>
#define N 5 //the number of philosophers
sem_t S[N]; //semaphores for chopsticks
void *
void take_chopsticks (int);
void put_chopsticks (int);
philospher (void *num);
int phil_num [N]= {0,1,2,3, 4}; //philosopher ID
int main ()
int i;
pthread_t thread_id[N];
for (i=0;i<N;i++)
sem_init (&S[i],0,1);
for (i=0;i<N;i++)
pthread_create (&thread_id[i],NULL,philospher, &phil_num[i]);
for (i=0;i<N;i++)
pthread_join (thread_id[i] , NULL);
void *philospher (void *num)
{
while (1)
{
int *i = num;
take_chopsticks (*i);
put_chopsticks (*i);
void take_chopsticks (int ph_num)
{
printf("Philosopher %d is Hungry\n",ph_num);
sem_wait (&S[ph_num]);
printf ("Philosopher %d takes chopstick %d \n",ph_num, ph_num);
//take the left chopstick
sleep (1);
sem_wait (&S[ (ph_num+1) %N]);
printf ("Philosopher %d takes chopstick %d \n",ph_num, (ph_num+1) %N);
//take the right chopstick
printf ("Philosopher %d is eating\n", ph_num);
sleep (1);
void put_chopsticks (int ph_num)
{
sem_post (&S[ph_num]); //put the left chopstick
printf("Philosopher %d putting chopstick %d \n",ph_num, ph_num);
sleep (1);
sem_post (&S [ (ph_num+1)%N]); //put the right chopstick
printf("Philosopher %d putting chopstick %d \n",ph_num, (ph_num+1)%N);
printf("Philosopher %d is thinking\n",ph_num);
sleep (1);

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