#include <pthread.h>

#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

static pthread_t worker1_thr;
static pthread_t worker2_thr;

static pthread_mutex_t worker_mtx;
static pthread_cond_t worker_go;
static pthread_cond_t worker_done;

struct workitem {
	struct workitem *next;
	int a, b;
};

struct workitem *head;

static void *
worker(void *arg)
{
	struct workitem *w;

	pthread_detach(pthread_self());
	fprintf(stderr, "WORKER: started %p\n", arg);

	pthread_mutex_lock(&worker_mtx);
	for (;;) {
		while (head == NULL) {
			pthread_cond_wait(&worker_go, &worker_mtx);
		}
		while (w = head) {
			head = w->next;

			fprintf(stderr, "WORKER: got work a=%d b=%d\n", w->a, w->b);
			free(w);
			pthread_cond_signal(&worker_done);
		}
	}
}

void
work_add(int a, int b)
{
	struct workitem *w;
	int dowake = 0;

	w = calloc(sizeof(*w), 1);
	w->a = a;
	w->b = b;
	pthread_mutex_lock(&worker_mtx);
	if (head == 0)
		dowake = 1;
	w->next = head;
	head = w;
	if (dowake)
		pthread_cond_signal(&worker_go);
	pthread_mutex_unlock(&worker_mtx);
}

int
main()
{
	
        pthread_mutex_init(&worker_mtx, NULL);
        pthread_cond_init(&worker_go, NULL);
        pthread_cond_init(&worker_done, NULL);

	fprintf(stderr, "pthread create\n");
        pthread_create(&worker1_thr, NULL, worker, (void *)1);
        pthread_create(&worker2_thr, NULL, worker, (void *)2);

	work_add(10, 15);
	work_add(11, 22);
	work_add(314, 159);

	pthread_mutex_lock(&worker_mtx);
	while (head != NULL) {
		pthread_cond_wait(&worker_done, &worker_mtx);
	}
	pthread_mutex_unlock(&worker_mtx);

	fprintf(stderr, "job complete\n");
	exit(0);
}