Re: Improving use of rt_refcnt

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Sun, Jul 05, 2015 at 02:12:18PM +0900, Ryota Ozaki wrote:
> On Sun, Jul 5, 2015 at 2:35 AM, David Young <dyoung%pobox.com@localhost> wrote:
> > On Sat, Jul 04, 2015 at 09:52:56PM +0900, Ryota Ozaki wrote:
> >> I'm trying to improve use of rt_refcnt: reducing
> >> abuse of it, e.g., rt_refcnt++/rt_refcnt-- outside
> >> route.c and extending it to treat referencing
> >> during packet processing (IOW, references from
> >> local variables) -- currently it handles only
> >> references between routes. The latter is needed for
> >> MP-safe networking.
> >
> > Do you propose to increase/decrease rt_refcnt in the packet processing
> > path, using atomic instructions?
> 
> Atomic instructions aren't used yet, i.e., softnet_lock is still needed.
> I will introduce them later. (Using refcount(9) by riastradh would be
> good once it is committed.)

I think the main point that David wanted to raise is that the normal
path for packets should *not* do any ref count changes at all.

Joerg