netdev - Re: [PATCH wpan-next v2 11/11] net: mac802154: Add a warning in the slow path

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Date:   Tue, 17 May 2022 15:45:12 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <aahringo@...hat.com>
Cc:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Network Development <netdev@...r.kernel.org>,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH wpan-next v2 11/11] net: mac802154: Add a warning in the
 slow path

Hi Alexander,

aahringo@...hat.com wrote on Sun, 15 May 2022 18:30:28 -0400:

> Hi,
> 
> On Thu, May 12, 2022 at 10:34 AM Miquel Raynal
> <miquel.raynal@...tlin.com> wrote:
> >
> > In order to be able to detect possible conflicts between the net
> > interface core and the ieee802154 core, let's add a warning in the slow
> > path: we want to be sure that whenever we start an asynchronous MLME
> > transmission (which can be fully asynchronous) the net core somehow
> > agrees that this transmission is possible, ie. the device was not
> > stopped. Warning in this case would allow us to track down more easily
> > possible issues with the MLME logic if we ever get reports.
> >
> > Unlike in the hot path, such a situation cannot be handled.
> >
> > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > ---
> >  net/mac802154/tx.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
> > index a3c9f194c025..d61b076239c3 100644
> > --- a/net/mac802154/tx.c
> > +++ b/net/mac802154/tx.c
> > @@ -132,6 +132,25 @@ int ieee802154_sync_and_hold_queue(struct ieee802154_local *local)
> >         return ret;
> >  }
> >
> > +static bool ieee802154_netif_is_down(struct ieee802154_local *local)
> > +{
> > +       struct ieee802154_sub_if_data *sdata;
> > +       bool is_down = false;
> > +
> > +       rcu_read_lock();
> > +       list_for_each_entry_rcu(sdata, &local->interfaces, list) {
> > +               if (!sdata->dev)
> > +                       continue;
> > +
> > +               is_down = !(sdata->dev->flags & IFF_UP);  
> 
> Is there not a helper for this flag?

I was surprised that nobody cared enough about that information to
create a helper. Then I grepped and figured out I was not the first to
to do that...

$ git grep "flags & IFF_UP" | wc -l
289