#include <errno.h>
#include <linux/futex.h>
#include <stdio.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <unistd.h>

static inline int futex(int *uaddr, int op, int val,
			const struct timespec *timeout,
			int *uaddr2, int val3)
{
	return syscall(SYS_futex, uaddr, op, val,
		       timeout, uaddr2, val3);
}

static void futex_sleep(int ms)
{
	static int round;
	struct timespec ts;
	int condition = 0;
	int rc;
	fprintf(stderr, "Before sleep %d\n", ++round);
	ts.tv_sec = 0;
	ts.tv_nsec = ms * 1000L * 1000L;
	rc = futex(&condition, FUTEX_WAIT, condition, &ts, NULL, 0);
	fprintf(stderr, "After sleep (error: %s)\n",
		(rc < 0 ? strerror(errno) : "none"));
}

int main()
{
	while(1) {
		futex_sleep(200);
	}
	return 0;
}