struct tcp_md5sig_pool * __percpu *tcp_alloc_md5sig_pool(struct sock *sk)
{
	struct tcp_md5sig_pool * __percpu *pool;
	int alloc = 0;

retry:
	spin_lock_bh(&tcp_md5sig_pool_lock);
	pool = tcp_md5sig_pool;
	if (tcp_md5sig_users++ == 0) {
		alloc = 1;
		spin_unlock_bh(&tcp_md5sig_pool_lock);
	} else if (!pool) {
		tcp_md5sig_users--;
		spin_unlock_bh(&tcp_md5sig_pool_lock);
		cpu_relax();
		goto retry;
	} else
		spin_unlock_bh(&tcp_md5sig_pool_lock);

	if (alloc) {
		/* we cannot hold spinlock here because this may sleep. */
		struct tcp_md5sig_pool * __percpu *p;

		p = __tcp_alloc_md5sig_pool(sk);
		spin_lock_bh(&tcp_md5sig_pool_lock);
		if (!p) {
			tcp_md5sig_users--;
			spin_unlock_bh(&tcp_md5sig_pool_lock);
			return NULL;
		}
		pool = tcp_md5sig_pool;
		if (pool) {
			/* oops, it has already been assigned. */
			spin_unlock_bh(&tcp_md5sig_pool_lock);
			__tcp_free_md5sig_pool(p);
		} else {
			tcp_md5sig_pool = pool = p;
			spin_unlock_bh(&tcp_md5sig_pool_lock);
		}
	}
	return pool;
}
struct tcp_md5sig_pool * __percpu *tcp_alloc_md5sig_pool(struct sock *sk)
{
	struct tcp_md5sig_pool * __percpu *pool;
	int alloc = 0;

retry:
	spin_lock_bh(&tcp_md5sig_pool_lock);
	pool = tcp_md5sig_pool;
	if (tcp_md5sig_users++ == 0) {
		alloc = 1;
		spin_unlock_bh(&tcp_md5sig_pool_lock);
	} else if (!pool) {
		tcp_md5sig_users--;
		spin_unlock_bh(&tcp_md5sig_pool_lock);
		cpu_relax();
		goto retry;
	} else
		spin_unlock_bh(&tcp_md5sig_pool_lock);

	if (alloc) {
		 
		struct tcp_md5sig_pool * __percpu *p;

		p = __tcp_alloc_md5sig_pool(sk);
		spin_lock_bh(&tcp_md5sig_pool_lock);
		if (!p) {
			tcp_md5sig_users--;
			spin_unlock_bh(&tcp_md5sig_pool_lock);
			return NULL;
		}
		pool = tcp_md5sig_pool;
		if (pool) {
			 
			spin_unlock_bh(&tcp_md5sig_pool_lock);
			__tcp_free_md5sig_pool(p);
		} else {
			tcp_md5sig_pool = pool = p;
			spin_unlock_bh(&tcp_md5sig_pool_lock);
		}
	}
	return pool;
}