peterson-working

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


#define NUM_THREADS  2
#define MAX_COUNT 1000000L

volatile long count = 0;
volatile int estado[NUM_THREADS];
volatile int turno;

void e_peterson(int id) {
    int other = (id +1) % NUM_THREADS;

    estado[id] = 1;
    turno = other;
    __sync_synchronize();
    while (estado[other] && turno == other);
}

void s_peterson(int id) {
    estado[id] = 0;
}

void *counter(void *threadid) {
    long tid, i, max = MAX_COUNT/NUM_THREADS;
    tid = (long)threadid;

    for (i=0; i < max; i++) {
        e_peterson(tid);
        count++; //SC
        s_peterson(tid);
    }

    pthread_exit(NULL);
}

int main (int argc, char *argv[]) {
    pthread_t threads[NUM_THREADS];
    int rc;
    long t;

    estado[0] = 0;
    estado[1] = 0;
    turno = 0;


    for(t=0; t<NUM_THREADS; t++){
        rc = pthread_create(&threads[t], NULL, counter, (void *)t);
        if (rc){
            printf("ERROR; return code from pthread_create() is %d\n", rc);
            exit(-1);
        }
    }

    for(t=0; t<NUM_THREADS; t++){
        pthread_join(threads[t], NULL);
    }

    float error = (MAX_COUNT-count)/(float) MAX_COUNT *100;

    printf("Final result: %ld Expected: %ld Diff: %ld Error: %3.2f%%\n", count, MAX_COUNT, count-MAX_COUNT, error);

    puts("Bye from main");
    pthread_exit(NULL);
}