Return Values

pthread_cond_signal() returns zero after completing successfully. Any other return value indicates that an error occurred. When the following condition occurs, the function fails and returns the corresponding value.

EINVAL

cv points to an illegal address.

Example 4–8 shows how to use pthread_cond_wait() and pthread_cond_signal().

Example 4–8 Using pthread_cond_wait() and pthread_cond_signal()

pthread_mutex_t count_lock;
pthread_cond_t count_nonzero;
unsigned count;

decrement_count()
{
    pthread_mutex_lock(&count_lock);
    while (count == 0)
        pthread_cond_wait(&count_nonzero, &count_lock);
    count = count - 1;
    pthread_mutex_unlock(&count_lock);
}

increment_count()
{
    pthread_mutex_lock(&count_lock);
    if (count == 0)
        pthread_cond_signal(&count_nonzero);
    count = count + 1;
    pthread_mutex_unlock(&count_lock);
}