Re: [PATCH] UDPCP Communication Protocol

Eric Dumazet
2010-12-31T11:25:58Z

Le vendredi 31 décembre 2010 à 10:29 +0100, stefani@seibold.net a
écrit :
> + if (!list_empty(&usk->destlist)) {
> + state->sk = (struct sock *)usk;
> + state->dest = list_first_entry(&usk->destlist,
> + struct udpcp_dest, list);
> + sock_hold(state->sk);
> +
> + if (atomic_read(&state->sk->sk_refcnt) != 1) {
> + spin_unlock_irqrestore(&spinlock, flags);
> + return state;
> + }
> + atomic_dec(&state->sk->sk_refcnt);
> + }
> +

I am trying to understand what you are doing here.

It seems racy to me.

Apparently, what you want is to take a reference only if actual
sk_refcnt is not zero.

I suggest using atomic_inc_notzero(&state->sk->sk_refcnt) to avoid the
race in atomic_dec().