mutex and condition variable

// C program to implement cond(), signal()

// and wait() functions

#include

#include

#include

 

// 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()

{

 

    // acquire a lock

    pthread_mutex_lock(&lock);

    if (done == 1) {

 

        // let's wait on conition varible 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;

}