static void put_ucounts(struct ucounts *ucounts)
{
	unsigned long flags;

	if (atomic_dec_and_test(&ucounts->count)) {
		spin_lock_irqsave(&ucounts_lock, flags);
		hlist_del_init(&ucounts->node);
		spin_unlock_irqrestore(&ucounts_lock, flags);

		kfree(ucounts);
	}
}
The program contains a code sequence that can run concurrently with other code, and the code sequence 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 that is operating concurrently.