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

pthread_mutex_t count_mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t condition_var = PTHREAD_COND_INITIALIZER;

void *function_count1();
void *function_count2();

int count = 1;

int main()
{
    pthread_t thread1, thread2;
    int ret;

    /* Create independent threads each of which will execute function_count1 */

    if( (ret=pthread_create( &thread1, NULL, &function_count1, "thread1")) )
    {
        printf("Thread 1 creation failed: %dn", ret);
        exit (EXIT_FAILURE);
    }

    if( (ret=pthread_create( &thread2, NULL, &function_count2, "thread2")) )
    {
        printf("Thread 2 creation failed: %dn", ret);
        exit (EXIT_FAILURE);
    }

    pthread_join( thread1, NULL);
    pthread_join( thread2, NULL);

    exit(EXIT_SUCCESS);
}

void *function_count1(void *arg)
{
    while(count <= 10)
    {
        // lock mutex and then wait for signal to release mutex
        pthread_mutex_lock( &count_mutex );
        if (count % 2 != 0)
        {
            pthread_cond_wait(&condition_var, &count_mutex);
            printf("%s : counter = %dn", (char *)arg, count++);
        }
        else
        {
            pthread_cond_signal(&condition_var);
        }
        pthread_mutex_unlock( &count_mutex );
    }
    //return;
}

void *function_count2(void *arg)
{
    while(count <= 10)
    {
        pthread_mutex_lock( &count_mutex );

        if (count % 2 == 0)
        {
            pthread_cond_wait(&condition_var, &count_mutex);
            printf("%s : counter = %dn", (char *)arg, count++);
        }
        else
        {
            pthread_cond_signal(&condition_var);
        }
        pthread_mutex_unlock(&count_mutex);
    }
    //return;
}