On Wed, 12 Dec 2007 07:20:34 -0800 (PST)
David Miller <[email protected]> wrote:
> From: Stephen Hemminger <[email protected]>
> Date: Tue, 11 Dec 2007 21:39:39 -0800
>
> > On Wed, 12 Dec 2007 13:01:27 +0900
> > "Joonwoo Park" <[email protected]> wrote:
> >
> > > [NETDEV]: tehuti Fix possible causing oops of net_rx_action
> > >
> > > Signed-off-by: Joonwoo Park <[email protected]>
> > > ---
> > > drivers/net/tehuti.c | 2 ++
> > > 1 files changed, 2 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/drivers/net/tehuti.c b/drivers/net/tehuti.c
> > > index 21230c9..955e749 100644
> > > --- a/drivers/net/tehuti.c
> > > +++ b/drivers/net/tehuti.c
> > > @@ -305,6 +305,8 @@ static int bdx_poll(struct napi_struct *napi, int budget)
> > >
> > > netif_rx_complete(dev, napi);
> > > bdx_enable_interrupts(priv);
> > > + if (unlikely(work_done == napi->weight))
> > > + return work_done - 1;
> > > }
> > > return work_done;
> > > }
> >
> > A better fix would be not going over budget in the first place.
>
> That's not the problem.
>
> They are not going over the budget, rather, they are hitting
> the budget yet doing netif_rx_complete() as well which is
> illegal.
>
> Unless you strictly process less than "weight" packets, you must
> not netif_rx_complete() and re-enable chip interrupts.
>
> I can't believe people are trying to fix this bug like this.
Sorry, I was looking at a different possible problem. The issue
is that if netdev_budget was set smaller (say 128) but device
weight was set larger (say 256). The new code would still allow
the device to do a full swipe (256) packets rather than only
128 as in earlier NAPI. I guess it is an okay behaviour change, because
we don't really guarantee that case.
The problem with the tehuti driver is the logic around priv->napi_stop.
That whole early stop concept should be removed since it just
duplicates the logic of netdev->weight but breaks the assumptions
in the calling netif_rx_action.
--
Stephen Hemminger <[email protected]>
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