Re: [PATCH wpan-next v3 09/11] net: mac802154: Introduce a synchronous API for MLME commands

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Alexander,

aahringo@redhat.com wrote on Tue, 17 May 2022 20:41:41 -0400:

> Hi,
> 
> On Tue, May 17, 2022 at 12:35 PM Miquel Raynal
> <miquel.raynal@bootlin.com> wrote:
> >
> > This is the slow path, we need to wait for each command to be processed
> > before continuing so let's introduce an helper which does the
> > transmission and blocks until it gets notified of its asynchronous
> > completion. This helper is going to be used when introducing scan
> > support.
> >
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  net/mac802154/ieee802154_i.h |  1 +
> >  net/mac802154/tx.c           | 46 ++++++++++++++++++++++++++++++++++++
> >  2 files changed, 47 insertions(+)
> >
> > diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
> > index a057827fc48a..b42c6ac789f5 100644
> > --- a/net/mac802154/ieee802154_i.h
> > +++ b/net/mac802154/ieee802154_i.h
> > @@ -125,6 +125,7 @@ extern struct ieee802154_mlme_ops mac802154_mlme_wpan;
> >  void ieee802154_rx(struct ieee802154_local *local, struct sk_buff *skb);
> >  void ieee802154_xmit_sync_worker(struct work_struct *work);
> >  int ieee802154_sync_and_hold_queue(struct ieee802154_local *local);
> > +int ieee802154_mlme_tx_one(struct ieee802154_local *local, struct sk_buff *skb);
> >  netdev_tx_t
> >  ieee802154_monitor_start_xmit(struct sk_buff *skb, struct net_device *dev);
> >  netdev_tx_t
> > diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
> > index 38f74b8b6740..6cc4e5c7ba94 100644
> > --- a/net/mac802154/tx.c
> > +++ b/net/mac802154/tx.c
> > @@ -128,6 +128,52 @@ int ieee802154_sync_and_hold_queue(struct ieee802154_local *local)
> >         return ieee802154_sync_queue(local);
> >  }
> >
> > +static int ieee802154_mlme_op_pre(struct ieee802154_local *local)
> > +{
> > +       return ieee802154_sync_and_hold_queue(local);
> > +}
> > +
> > +static int ieee802154_mlme_tx(struct ieee802154_local *local, struct sk_buff *skb)
> > +{
> > +       int ret;
> > +
> > +       /* Avoid possible calls to ->ndo_stop() when we asynchronously perform
> > +        * MLME transmissions.
> > +        */
> > +       rtnl_lock();
> > +
> > +       /* Ensure the device was not stopped, otherwise error out */
> > +       if (!local->open_count)
> > +               return -EBUSY;
> > +  
> 
> No -EBUSY here, use ?-ENETDOWN?.

Isn't it strange to return "Network is down" while we try to stop the
device but fail to do so because, actually, it is still being used?

> You forgot rtnl_unlock() here.

I've blindly added those rtnl calls, I need to go through all of them
once again and ensure all the error path release the lock.

Thanks,
Miquèl