aahringo@xxxxxxxxxx wrote on Tue, 17 May 2022 21:14:03 -0400:
> Hi,
>
> On Tue, May 17, 2022 at 9:30 AM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> >
> >
> > aahringo@xxxxxxxxxx wrote on Sun, 15 May 2022 19:03:53 -0400:
> >
> > > Hi,
> > >
> > > On Sun, May 15, 2022 at 6:28 PM Alexander Aring <aahringo@xxxxxxxxxx> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Thu, May 12, 2022 at 10:34 AM Miquel Raynal
> > > > <miquel.raynal@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > > > > ---
> > > > > 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
> > >
> > > not over the whole MLME_op, that's terrible to hold the rtnl lock so
> > > long... so I think this is fine that some netdev call will interfere
> > > with this transmission.
> > > So forget about the ASSERT_RTNL() here, it's fine (I hope).
> > >
> > > > 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
> > >
> > > Whereas the stop of the netdev queue makes sense for the whole mlme-op
> > > (in my opinion).
> >
> > I might still implement an MLME pre/post helper and do the queue
> > hold/release calls there, while only taking the rtnl from the _tx.
> >
> > And I might create an mlme_tx_one() which does the pre/post calls as
> > well.
> >
> > Would something like this fit?
>
> I think so, I've heard for some transceiver types a scan operation can
> take hours... but I guess whoever triggers that scan in such an
> environment knows that it has some "side-effects"...
Yeah, a scan requires the data queue to be stopped and all incoming
packets to be dropped (others than beacons, ofc), so users must be
aware of this limitation.
