Re: [PATCH wpan-next v2 09/11] net: mac802154: Introduce a synchronous API for MLME commands

From: Alexander Aring <aahringo@redhat.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Alexander Aring <alex.aring@gmail.com>,
	Stefan Schmidt <stefan@datenfreihafen.org>,
	linux-wpan - ML <linux-wpan@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Network Development <netdev@vger.kernel.org>,
	David Girault <david.girault@qorvo.com>,
	Romuald Despres <romuald.despres@qorvo.com>,
	Frederic Blain <frederic.blain@qorvo.com>,
	Nicolas Schodet <nico@ni.fr.eu.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH wpan-next v2 09/11] net: mac802154: Introduce a synchronous API for MLME commands
Date: Sun, 15 May 2022 18:56:05 -0400	[thread overview]
Message-ID: <CAK-6q+ivVCJOEF+MN-y64K1M-nf2ak0CUqjj0tiiyinaNCAE5w@mail.gmail.com> (raw)
In-Reply-To: <CAK-6q+ipHdD=NJB2N7SHQ0TUvNpc0GQXZ7dWM9nDxqyqNgxdSA@mail.gmail.com>

Hi,

On Sun, May 15, 2022 at 6:28 PM Alexander Aring <aahringo@redhat.com> wrote:
>
> Hi,
>
> On Thu, May 12, 2022 at 10:34 AM 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           | 25 +++++++++++++++++++++++++
> >  2 files changed, 26 insertions(+)
> >
> > diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
> > index a057827fc48a..f8b374810a11 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(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..ec8d872143ee 100644
> > --- a/net/mac802154/tx.c
> > +++ b/net/mac802154/tx.c
> > @@ -128,6 +128,31 @@ int ieee802154_sync_and_hold_queue(struct ieee802154_local *local)
> >         return ieee802154_sync_queue(local);
> >  }
> >
> > +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();
>
> I think we should make an ASSERT_RTNL() here, the lock needs to be
> earlier than that over the whole MLME op. MLME can trigger more than
> one message, the whole sync_hold/release queue should be earlier than
> that... in my opinion is it not right to allow other messages so far
> an MLME op is going on? I am not sure what the standard says to this,
> but I think it should be stopped the whole time? All those sequence
> diagrams show only some specific frames, also remember that on the
> receive side we drop all other frames if MLME op (e.g. scan) is going
> on?

Maybe some mlme_op_pre(), ... mlme_tx(), ..., mlme_tx(), ...,
mlme_op_post() handling?

- Alex