Function eventfd_write

freebsd/kern/sys_eventfd.c:189–231

}

static int
eventfd_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{
	struct eventfd *efd;
	eventfd_t count;
	int error;

	if (uio->uio_resid < sizeof(eventfd_t))
		return (EINVAL);

	error = uiomove(&count, sizeof(eventfd_t), uio);
	if (error != 0)
		return (error);
	if (count == UINT64_MAX)
		return (EINVAL);

	efd = fp->f_data;
	mtx_lock(&efd->efd_lock);
retry:
	if (UINT64_MAX - efd->efd_count <= count) {
		if ((fp->f_flag & FNONBLOCK) != 0) {
			mtx_unlock(&efd->efd_lock);
			/* Do not not return the number of bytes written */
			uio->uio_resid += sizeof(eventfd_t);
			return (EAGAIN);
		}
		error = mtx_sleep(&efd->efd_count, &efd->efd_lock,
		    PCATCH, "efdwr", 0);
		if (error == 0)
			goto retry;
	}
	if (error == 0) {
		MPASS(UINT64_MAX - efd->efd_count > count);
		efd->efd_count += count;
		KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
		selwakeup(&efd->efd_sel);
		wakeup(&efd->efd_count);
	}
	mtx_unlock(&efd->efd_lock);

	return (error);
}

static int
eventfd_poll(struct file *fp, int events, struct ucred *active_cred,