netdev - Re: [PATCH wpan-next 06/11] net: mac802154: Hold the transmit queue when relevant

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Message-ID: <20220510165237.43382f42@xps13>
Date:   Tue, 10 May 2022 16:52:37 +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@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        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 06/11] net: mac802154: Hold the transmit queue
 when relevant

Hi Alex,

> > --- a/net/mac802154/tx.c
> > +++ b/net/mac802154/tx.c
> > @@ -106,6 +106,21 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
> >         return NETDEV_TX_OK;
> >  }
> >
> > +void ieee802154_hold_queue(struct ieee802154_local *local)
> > +{
> > +       atomic_inc(&local->phy->hold_txs);
> > +}
> > +
> > +void ieee802154_release_queue(struct ieee802154_local *local)
> > +{
> > +       atomic_dec(&local->phy->hold_txs);
> > +}
> > +
> > +bool ieee802154_queue_is_held(struct ieee802154_local *local)
> > +{
> > +       return atomic_read(&local->phy->hold_txs);
> > +}  
> 
> I am not getting this, should the release_queue() function not do
> something like:
> 
> if (atomic_dec_and_test(hold_txs))
>       ieee802154_wake_queue(local);
> 
> I think we don't need the test of "ieee802154_queue_is_held()" here,
> then we need to replace all stop_queue/wake_queue with hold and
> release?

That's actually a good idea. I've implemented it and it looks nice too.
I'll clean this up and share a new version with:
- The wake call checked everytime hold_txs gets decremented
- The removal of the _queue_is_held() helper
- _wake/stop_queue() turned static
- _hold/release_queue() used everywhere

Thanks,
Miquèl