static void stable_tree_append(struct rmap_item *rmap_item,
			       struct stable_node *stable_node)
{
	rmap_item->head = stable_node;
	rmap_item->address |= STABLE_FLAG;
	hlist_add_head(&rmap_item->hlist, &stable_node->hlist);

	if (rmap_item->hlist.next)
		ksm_pages_sharing++;
	else
		ksm_pages_shared++;
}

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.