> how does the event waiter thread determine whether there is a
> suitable/idle worker thread to awaken?

like this?

struct Q {
    struct Q *next;
    pthread_t worker;
    int fd;
    pthread_cond_t sleep;
} *head, *tail;
int Qlen;
pthread_cond_t Qlow;
pthread_mutex_t QLOCK;

void workerthread() {
    struct Q *this;
    while (1) {
        pthread_cond_wait(this->sleep);
        /* work on fd here... */
        this->next=NULL;
        pthread_mutex_lock(QLOCK);
        tail->next=this;
        tail=this;
        ++Qlen;
        pthread_mutex_unlock(QLOCK);
    }
}

void qwatcherthread() {
    struct Q *new;
    while (1) {
        pthread_cond_wait(Qlow);
        new=create_new_worker();
        new->next=NULL;
        pthread_mutex_lock(QLOCK);
        tail->next=new;
        tail=new;
        ++Qlen;
        pthread_mutex_unlock(QLOCK);
    }
}

void acceptor() {
    struct Q *work;
    while (1) {
        if (Qlen<min_workers)
            pthread_cond_signal(Qlow);
        newfd=accept(...);
        pthread_mutex_lock(QLOCK);
        if (head) {
            --Qlen;
            work=head;
            head=head->next;
        } else {
            work=create_new_worker();
        }
        pthread_mutex_unlock(QLOCK);
        work->fd=newfd;
        pthtread_cond_signal(work->sleep);
    }
}

(no, I don't claim this code is correct, but just to illustrate how it
could be done :-)

Olaf


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