// C program to implement cond(), signal()
// and wait() functions
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>

// Declaration of thread condition variable
pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;

// declaring mutex
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

int done = 1;

// Thread function
void* foo()
{

    	sleep(2);
    	// acquire a lock
    	pthread_mutex_lock(&lock);
    	if (done == 1) {

        	// let's wait on condition variable cond1
        	done = 2;
        	printf("Waiting on condition variable cond1\n");
        	pthread_cond_wait(&cond1, &lock);
    	}
    	else {

        	// Let's signal condition variable cond1
        	printf("Signaling condition variable cond1\n");
        	pthread_cond_signal(&cond1);
    	}

    	// release lock
	//    pthread_mutex_unlock(&lock);

    	printf("Returning thread\n");

    	return NULL;
}

// Driver code
int main()
{
    	pthread_t tid1, tid2;

    	// Create thread 1
    	pthread_create(&tid1, NULL, foo, NULL);

    	// sleep for 1 sec so that thread 1
    	// would get a chance to run first
    	sleep(1);

    	// Create thread 2
    	pthread_create(&tid2, NULL, foo, NULL);

    	// wait for the completion of thread 2
    	pthread_join(tid2, NULL);

    	return 0;
}