Re: [PATCH v3 net-next 1/4] net: implement support for low latencysocket polling

[Eliezer Tamir]

On 20/05/2013 18:29, Eric Dumazet wrote:
> On Mon, 2013-05-20 at 13:16 +0300, Eliezer Tamir wrote:
---
> > +static inline void skb_mark_ll(struct sk_buff *skb, struct napi_struct *napi)
> > +{
> > +	skb->dev_ref = napi;
> > +}
> > +
> > +static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
> > +{
> > +	sk->dev_ref = skb->dev_ref;
> > +}
>
> I do not see why it's safe to keep a pointer to a napi object without
> taking a reference, or something to prevent object being removed.
>
> Using a genid might be enough. (some counter incremented every time a
> napi is dismantled)

I really like this approach and I tried it.
The main problem I had is that you need to increase the size of the skb 
to store the generation id unless you stuff it in the flags2 bitfield.
There appear to be only 7 useful bit left there.
Is it OK to use them all up?


> Alternatively, use a napi_id instead of a pointer.

I'm not sure I understand what you propose.

-Eliezer
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