Re: [net-next PATCH v2 3/4] netdev: replace napi_reschedule with napi_schedule

[Eric Dumazet]

On Fri, Oct 6, 2023 at 8:52 PM Christian Marangi <ansuelsmth@xxxxxxxxx> wrote:
>
> On Thu, Oct 05, 2023 at 06:41:03PM +0200, Eric Dumazet wrote:
> > On Thu, Oct 5, 2023 at 6:32 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
> > >
> > > On Thu, 5 Oct 2023 18:11:56 +0200 Eric Dumazet wrote:
> > > > OK, but I suspect some users of napi_reschedule() might not be race-free...
> > >
> > > What's the race you're thinking of?
> >
> > This sort of thing... the race is in fl_starving() though...
> >
> > diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c
> > b/drivers/net/ethernet/chelsio/cxgb4/sge.c
> > index 98dd78551d89..b5ff2e1a9975 100644
> > --- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
> > +++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
> > @@ -4261,7 +4261,7 @@ static void sge_rx_timer_cb(struct timer_list *t)
> >
> >                         if (fl_starving(adap, fl)) {
> >                                 rxq = container_of(fl, struct sge_eth_rxq, fl);
> > -                               if (napi_reschedule(&rxq->rspq.napi))
> > +                               if (napi_schedule(&rxq->rspq.napi))
> >                                         fl->starving++;
> >                                 else
> >                                         set_bit(id, s->starving_fl);
>
> Ehhh problem is that this is a simple rename so if any race is present,
> it's already there and not caused by this rename :(
>
> Don't know maybe this is out of scope and should be investigated with a
> bug report?
>
> Maybe this should be changed to prep/__schedule to prevent any kind of
> race? But doing so doesn't prevent any kind of ""starving""?
>

I gave a "Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>", meaning
your patch was ok for me.

My remark was orthogonal, I am not asking you to act on it ;)