Subject: Re: [PATCH 1/1] Use RCU for the UDP hash lock

From: Jarek Poplawski <[email-masked]>
Date: Fri, 26 Sep 2008 05:46:00 +0000

On Thu, Sep 25, 2008 at 10:18:33PM -0500, Corey Minyard wrote:
...
> This patch is the second try; I believe I fixed all issues that people
> raised.

Actually, you've skipped my first question, so I still don't know, why
you don't use an _init version of sk_del_node (even if it's safe in the
current implementation), while the non-rcu code uses only this?

...
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 06c5259..65110a6 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
...
>  static inline int sk_unhashed(const struct sock *sk)
>  {
>  	return hlist_unhashed(&sk->sk_node);
> @@ -361,6 +374,27 @@ static __inline__ int sk_del_node_init(struct sock *sk)
>  	return rc;
>  }
>  
> +static inline int __sk_del_node_rcu(struct sock *sk)
> +{
> +	if (sk_hashed(sk)) {
> +		hlist_del_rcu(&sk->sk_node);
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +static inline int sk_del_node_rcu(struct sock *sk)
> +{
> +	int rc = __sk_del_node_rcu(sk);
> +
> +	if (rc) {
> +		/* paranoid for a while -acme */
> +		WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
> +		__sock_put(sk);
> +	}
> +	return rc;
> +}
...

Jarek P.