atomic_write
if (atomic_write(slp->fd, slp->req, siz) != siz)
if (atomic_write(slp->fd, q, size) != size) {
static int atomic_write(int, const void *, int);
atomic_write(slaves[i].fd, &slaves[(i + 1) % SLAVES].pid,
atomic_write(cmd, &size, sizeof size);