On Thu, 2017-03-16 at 15:33 -0700, Alexander Duyck wrote: > On Thu, Mar 16, 2017 at 3:05 PM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> > It is not clear why this patch is needed . > > > > What you describe here is the case we might receive packets for a socket > > coming from different interfaces ? > > > > If skb->napi_id is a sender_cpu, why should we prevent overwriting the > > sk_napi_id with it, knowing that busy polling will simply ignore the > > invalid value ? > > > > Do not get me wrong : > > > > I simply try to understand why the test about napi_id validity is now > > done twice : > > > > 1) At the time we are writing into sk->sk_napi_id > > I would argue that this is the one piece we were missing. > > > 2) At busy polling time when we read sk->sk_napi_id > > Unless there was something recently added I don't think this was ever > checked. Instead we start digging into the hash looking for the ID > that won't ever be there. Maybe we should add something to napi_by_id > that just returns NULL in these cases. But this is exactly what should happen. For invalid ID, we return NULL from napi_by_id() No need to add code for that, since the function is meant to deal with valid cases. > On top of that I think there end up being several spots where once we > lock in a non-NAPI ID it is stuck such as the sk_mark_napi_id_once > call. I figure we are better off locking in an actual NAPI ID rather > than getting a sender_cpu stuck in there. Are you referring to sk_mark_napi_id_once() ? Since this is only used by UDP, I would be OK to avoid the 'locking' for 'sender_cpu' ids.
