Re: [PATCH v2 tip/core/rcu 07/13] ipv6/ip6_tunnel: Applyrcu_access_pointer() to avoid sparse false positive

[Josh Triplett]

On Wed, Oct 09, 2013 at 03:51:17PM -0700, Eric Dumazet wrote:
> On Wed, 2013-10-09 at 15:36 -0700, Paul E. McKenney wrote:
> 
> > That would work, though it would probably give sparse complaints.
> 
> No sparse error here, as I said types are correct and SPARSE_RCU ready :
> 
> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
> index 583b77e..28f8495 100644
> --- a/net/ipv6/ip6_tunnel.c
> +++ b/net/ipv6/ip6_tunnel.c
> @@ -245,7 +245,7 @@ ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
>              (iter = rtnl_dereference(*tp)) != NULL;
>              tp = &iter->next) {
>                 if (t == iter) {
> -                       rcu_assign_pointer(*tp, t->next);
> +                       ACCESS_ONCE(*tp) = t->next;
>                         break;
>                 }
>         }

I'd be really hesitant to introduce that type of direct assignment to an
__rcu pointer without wrapping it in some appropriately named macro, or
at the very least adding a comment.

- Josh Triplett
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/