static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn,
						 unsigned long end_pfn)
{
	struct rb_node *node;

	for (node = rb_first(&root_stable_tree); node; node = rb_next(node)) {
		struct stable_node *stable_node;

		stable_node = rb_entry(node, struct stable_node, node);
		if (stable_node->kpfn >= start_pfn &&
		    stable_node->kpfn < end_pfn)
			return stable_node;
	}
	return NULL;
}

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.