synchronize_kernel();
synchronize_rcu();
static int raid10_remove_disk(mddev_t *mddev, int number){	conf_t *conf = mddev->private;	int err = 0;	mdk_rdev_t *rdev;	mirror_info_t *p = conf->mirrors+ number;	print_conf(conf);	rdev = p->rdev;	if (rdev) {		if (rdev->in_sync ||		    atomic_read(&rdev->nr_pending)) {			err = -EBUSY;			goto abort;		}		p->rdev = NULL;		synchronize_kernel();		if (atomic_read(&rdev->nr_pending)) {			/* lost the race, try later */			err = -EBUSY;			p->rdev = rdev;		}	}abort:	print_conf(conf);	return err;}