static int unlazy_walk(struct nameidata *nd)
{
	struct dentry *parent = nd->path.dentry;

	BUG_ON(!(nd->flags & LOOKUP_RCU));

	nd->flags &= ~LOOKUP_RCU;
	if (unlikely(!legitimize_links(nd)))
		goto out2;
	if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
		goto out1;
	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
		if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq)))
			goto out;
	}
	rcu_read_unlock();
	BUG_ON(nd->inode != parent->d_inode);
	return 0;

out2:
	nd->path.mnt = NULL;
	nd->path.dentry = NULL;
out1:
	if (!(nd->flags & LOOKUP_ROOT))
		nd->root.mnt = NULL;
out:
	rcu_read_unlock();
	return -ECHILD;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.