#include <pthread.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>

pthread_mutex_t mtx;
pthread_cond_t cv;

void mutex_lock()
{
	if (pthread_mutex_lock(&mtx) != 0)
		_exit(3);
}

void mutex_unlock()
{
	if (pthread_mutex_unlock(&mtx) != 0)
		_exit(3);
}

int main()
{
	if (0 != pthread_mutex_init(&mtx,0))
		return 1;
	if (0 != pthread_cond_init(&cv,0))
		return 2;

	while(1) {
		int i;
		for (i=0; i<3; ++i) {
			mutex_lock();
			const time_t wait_time = time(0)+1;
			struct timespec tm;
			tm.tv_sec = wait_time;
			tm.tv_nsec = 0;
			const int err = pthread_cond_timedwait(&cv, &mtx, &tm);
			if (err != ETIMEDOUT) {
				printf("error cond\n");
				return 4;
			}
			const time_t end_time = time(0);
			mutex_unlock();
			if (end_time < wait_time) {
				printf("wait:%lu wakeup:%lu\n", (long)wait_time, (long)end_time);
				assert(!"early wakeup");
			}
			printf("OK\n");
		}
		const long s = random() % 100000;
		printf("switch, sleep %l ms\n", s);
		usleep(s);
	}
}