netdev - Re: [igb] netconsole triggers warning in netpoll_poll

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Date:   Sun, 21 Nov 2021 13:16:33 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Danielle Ratson <danieller@...dia.com>
Cc:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [igb] netconsole triggers warning in netpoll_poll_dev

On Sun, Nov 21, 2021 at 3:44 AM Danielle Ratson <danieller@...dia.com> wrote:
>
> > > > >  drivers/net/ethernet/intel/igb/igb_main.c | 12 ++++++++----
> > > > >  1 file changed, 8 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> > > > > b/drivers/net/ethernet/intel/igb/igb_main.c
> > > > > index 0cd37ad81b4e..b0a9bed14071 100644
> > > > > --- a/drivers/net/ethernet/intel/igb/igb_main.c
> > > > > +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> > > > > @@ -7991,12 +7991,16 @@ static void igb_ring_irq_enable(struct
> > > > igb_q_vector *q_vector)
> > > > >   **/
> > > > >  static int igb_poll(struct napi_struct *napi, int budget)  {
> > > > > -       struct igb_q_vector *q_vector = container_of(napi,
> > > > > -                                                    struct igb_q_vector,
> > > > > -                                                    napi);
> > > > > -       bool clean_complete = true;
> > > > > +       struct igb_q_vector *q_vector;
> > > > > +       bool clean_complete;
> > > > >         int work_done = 0;
> > > > >
> > > > > +       /* if budget is zero, we have a special case for netconsole, so
> > > > > +        * make sure to set clean_complete to false in that case.
> > > > > +        */
> > > > > +       clean_complete = !!budget;
> > > > > +
> > > > > +       q_vector = container_of(napi, struct igb_q_vector, napi);
> > > > >  #ifdef CONFIG_IGB_DCA
> > > > >         if (q_vector->adapter->flags & IGB_FLAG_DCA_ENABLED)
> > > > >                 igb_update_dca(q_vector);
> > > >
> > > > I'm not a big fan of moving the q_vector init as a part of this
> > > > patch since it just means more backport work.
> > > >
> > > > That said the change itself should be harmless so I am good with it
> > > > either way.
> > > >
> > > > Reviewed-by: Alexander Duyck <alexanderduyck@...com>
> > >
> > > Hi,
> > >
> > > I have lately added the netconsole module, and since then we see the
> > same warning constantly in the logs.
> > > I have tried to apply Jesse's patch but it didn't seem to solve the issue.
> > >
> > > Did anyone managed to solve the issue and can share with us?
> > >
> > > Thanks,
> > > Danielle
> >
> > The one issue I can see is that it basically leaves the igb_poll call stuck in
> > polling mode.
> >
> > The easiest fix for all of this in the in-kernel driver is to just get rid of the
> > "min" at the end and instead just "return work_done;". The extra
> > complication is only needed if you were to be polling multiple queues and
> > that isn't the case here so we should simplify it and get rid of the buggy
> > "budget - 1" return value.
>
> Thank you very much for your reply Alexander!
> It seems to work well!
>
> Are you planning to send it upstream?

No, I was just suggesting it as a possible solution. Feel free to put
together your own patch and submit it if it is working for you.

- Alex