anybody who known usage of the cond in cq ?

[ShaoLin]

i'm sorry for my pool english.the question is like this:
in funciton cq_init, initialize a condition (cq->cond).
static void cq_init(CQ *cq) {
    pthread_mutex_init(&cq->lock, NULL);
    pthread_cond_init(&cq->cond, NULL);  //this line
    cq->head = NULL;
    cq->tail = NULL;
}

when a connection from client come in, the listen thread dispath the
task, and call cq_push,

static void cq_push(CQ *cq, CQ_ITEM *item) {
    item->next = NULL;

    pthread_mutex_lock(&cq->lock);
    if (NULL == cq->tail)
        cq->head = item;
    else
        cq->tail->next = item;
    cq->tail = item;
    pthread_cond_signal(&cq->cond);  //this line
    pthread_mutex_unlock(&cq->lock);
}

but i not found the task thread call  pthread_cond_wait(&cq->cond);
what the cq->cond for?
thanks