For The Best Thing In The World

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#define NLOOP 5000
int counter; /* incremented by threads */ pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;
void *doit(void *);
int main(int argc, char **argv)
{
    pthread_t tidA, tidB;
    pthread_create(&tidA, NULL, doit, NULL); pthread_create(&tidB, NULL, doit, NULL);
    /* wait for both threads to terminate */
    pthread_join(tidA, NULL);
    pthread_join(tidB, NULL);
    return 0;
}

void *doit(void *vptr)
{
    int i, val;
    /*
     * Each thread fetches, prints, and increments the counter
     NLOOP times.
     * The value of the counter should increase monotonically. */
    for (i = 0; i < NLOOP; i++) {
        pthread_mutex_lock(&counter_mutex);
        val = counter;
        printf("%d\t", val +1);
        counter = val + 1;
        pthread_mutex_unlock(&counter_mutex);
    }
    printf("final counter is %d\n", counter);
}