Program to implement Peterson’s Algorithm for Mutual Exclusion in C

/*
    Peterson’s Algorithm for Mutual Exclusion
    Created By: Pirate
*/

#include <stdio.h>
#include <pthread.h>

void* process(void *s);
int flag[2];
int turn,count=0,mode=0;
const int MAX = 1e9;

void main()
{
    printf("*** Peterson's Algorithm ***\n");
    pthread_t p1,p2,p3,p4;

    printf("\nFirst without Lock\n");

    pthread_create(&p1, NULL, process, (void*)0);
    pthread_create(&p2, NULL, process, (void*)1);

    pthread_join(p1, NULL);
    pthread_join(p2, NULL);

    printf("Actual Count: %d | Expected Count: %d\n",count, MAX*2);

    printf("\n\nNow with Lock\n");
    count = 0;
    mode = 1;
    lock_init();

    pthread_create(&p3, NULL, process, (void*)0);
    pthread_create(&p4, NULL, process, (void*)1);

    pthread_join(p3, NULL);
    pthread_join(p4, NULL);

    printf("Actual Count: %d | Expected Count: %d\n",count, MAX*2);

}

void lock_init()
{
    flag[0] = flag[1] = 0;
    turn = 0;
}

void lock(int current)
{
    flag[current] = 1;

    turn = 1-current;
    while (flag[1-current]==1 && turn==1-current) ;
}

void unlock(int current)
{
    flag[current] = 0;
}

void* process(void *s)
{
    int i = 0;
    int current = (int *)s;
    printf("Process : %d\n", current);

    if(mode == 1)
        lock(current);
    for (i=0; i<MAX; i++)
        count++;

    if(mode == 1)
        unlock(current);
}





Output :