void blk_mq_free_queue(struct request_queue *q)
{
	struct blk_mq_tag_set	*set = q->tag_set;

	blk_mq_del_queue_tag_set(q);

	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
	blk_mq_free_hw_queues(q, set);

	percpu_ref_exit(&q->mq_usage_counter);

	kfree(q->mq_map);

	q->mq_map = NULL;

	mutex_lock(&all_q_mutex);
	list_del_init(&q->all_q_node);
	mutex_unlock(&all_q_mutex);
}

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.