From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Alexander Aring <aahringo@redhat.com>
Cc: Alexander Aring <alex.aring@gmail.com>,
Stefan Schmidt <stefan@datenfreihafen.org>,
linux-wpan@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
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 06/11] net: mac802154: Hold the transmit queue when relevant
Date: Thu, 12 May 2022 16:33:07 +0200 [thread overview]
Message-ID: <20220512163307.540d635d@xps13> (raw)
In-Reply-To: <CAK-6q+jeubhGah2gG1JJxfmOW=sNdMrLf+mk_a3X_r+Na=tHXg@mail.gmail.com>
Hi Alexander,
aahringo@redhat.com wrote on Wed, 11 May 2022 09:09:40 -0400:
> Hi,
>
> On Tue, May 10, 2022 at 10:52 AM Miquel Raynal
> <miquel.raynal@bootlin.com> wrote:
> >
> > 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
> >
>
> I think there is also a lock necessary for atomic inc/dec hitting zero
> and the stop/wake call afterwards...
Mmmh that is true, it can race. I've introduced a mutex (I think it's
safe but it can be turned into a spinlock if proven necessary) to
secure these increment/decrement+wakeup operations.
> ,there are also a lot of
> optimization techniques to only hold the lock for hitting zero cases
> in such areas. However we will see...
I am not aware of technical solutions to avoid the locking in these
cases, what do you have in mind? Otherwise I propose just to come up
with a working and hopefully solid solution and then we'll see how to
optimize.
Thanks,
Miquèl
next prev parent reply other threads:[~2022-05-12 14:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-27 16:46 [PATCH wpan-next 00/11] ieee802154: Synchronous Tx support Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 01/11] net: mac802154: Stop exporting ieee802154_wake/stop_queue() Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 02/11] net: mac802154: Change the wake/stop queue prototypes Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 03/11] net: mac802154: Rename the synchronous xmit worker Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 04/11] net: mac802154: Rename the main tx_work struct Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 05/11] net: mac802154: Follow the count of ongoing transmissions Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 06/11] net: mac802154: Hold the transmit queue when relevant Miquel Raynal
2022-05-04 0:51 ` Alexander Aring
2022-05-10 14:52 ` Miquel Raynal
2022-05-11 13:09 ` Alexander Aring
2022-05-12 14:33 ` Miquel Raynal [this message]
2022-05-12 14:44 ` Alexander Aring
2022-05-17 9:13 ` Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 07/11] net: mac802154: Create a hot tx path Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 08/11] net: mac802154: Add a warning in the hot path Miquel Raynal
2022-04-27 18:01 ` Alexander Aring
2022-04-28 7:58 ` Miquel Raynal
2022-05-02 0:21 ` Alexander Aring
2022-05-12 14:33 ` Miquel Raynal
2022-05-13 14:26 ` Alexander Aring
2022-04-27 16:46 ` [PATCH wpan-next 09/11] net: mac802154: Introduce a helper to disable the queue Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 10/11] net: mac802154: Introduce a tx queue flushing mechanism Miquel Raynal
2022-05-04 0:40 ` Alexander Aring
2022-05-10 8:57 ` Miquel Raynal
2022-04-27 16:46 ` [PATCH wpan-next 11/11] net: mac802154: Introduce a synchronous API for MLME commands Miquel Raynal
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