From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Alexander Aring <alex.aring@gmail.com>
Cc: Stefan Schmidt <stefan@datenfreihafen.org>,
linux-wpan - ML <linux-wpan@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
Michael Hennerich <michael.hennerich@analog.com>,
Harry Morris <h.morris@cascoda.com>,
Varka Bhadram <varkabhadram@gmail.com>,
Xue Liu <liuxuenetmail@gmail.com>, Alan Ott <alan@signal11.us>,
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>,
"linux-wireless@vger.kernel.org Wireless"
<linux-wireless@vger.kernel.org>
Subject: Re: [wpan-next v2 18/27] net: mac802154: Handle scan requests
Date: Thu, 13 Jan 2022 18:07:09 +0100 [thread overview]
Message-ID: <20220113180709.0dade123@xps13> (raw)
In-Reply-To: <CAB_54W4PL1ty5XsqRoEKwsy-h8KL9gSGMK6N=HiWJDp6NHsb0A@mail.gmail.com>
Hi Alexander,
alex.aring@gmail.com wrote on Wed, 12 Jan 2022 17:44:02 -0500:
> Hi,
>
> On Wed, 12 Jan 2022 at 12:33, Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> ...
> > + return 0;
> > +}
> > diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
> > index c829e4a75325..40656728c624 100644
> > --- a/net/mac802154/tx.c
> > +++ b/net/mac802154/tx.c
> > @@ -54,6 +54,9 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
> > struct net_device *dev = skb->dev;
> > int ret;
> >
> > + if (unlikely(mac802154_scan_is_ongoing(local)))
> > + return NETDEV_TX_BUSY;
> > +
>
> Please look into the functions "ieee802154_wake_queue()" and
> "ieee802154_stop_queue()" which prevent this function from being
> called. Call stop before starting scanning and wake after scanning is
> done or stopped.
Mmmh all this is already done, isn't it?
- mac802154_trigger_scan_locked() stops the queue before setting the
promiscuous mode
- mac802154_end_of_scan() wakes the queue after resetting the
promiscuous mode to its original state
Should I drop the check which stands for an extra precaution?
But overall I think I don't understand well this part. What is
a bit foggy to me is why the (async) tx implementation does:
*Core* *Driver*
stop_queue()
drv_async_xmit() -------
\------> do something
------- calls ieee802154_xmit_complete()
wakeup_queue() <--------/
So we actually disable the queue for transmitting. Why??
> Also there exists a race which exists in your way and also the one
> mentioned above. There can still be some transmissions going on... We
> need to wait until "all possible" tx completions are done... to be
> sure there are really no transmissions going on. However we need to be
> sure that a wake cannot be done if a tx completion is done, we need to
> avoid it when the scan operation is ongoing as a workaround for this
> race.
>
> This race exists and should be fixed in future work?
Yep, this is true, do you have any pointers? Because I looked at the
code and for now it appears quite unpractical to add some kind of
flushing mechanism on that net queue. I believe we cannot use the netif
interface for that so we would have to implement our own mechanism in
the ieee802154 core.
Thanks,
Miquèl
next prev parent reply other threads:[~2022-01-13 17:07 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-12 17:32 [wpan-next v2 00/27] IEEE 802.15.4 scan support Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 01/27] net: mac802154: Split the set channel hook implementation Miquel Raynal
2022-01-12 22:30 ` Alexander Aring
2022-01-12 22:53 ` Alexander Aring
2022-01-13 11:12 ` Miquel Raynal
2022-01-13 9:32 ` Miquel Raynal
2022-01-13 23:27 ` Alexander Aring
2022-01-12 17:32 ` [wpan-next v2 02/27] net: mac802154: Ensure proper channel selection at probe time Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 03/27] net: ieee802154: Improve the way supported channels are declared Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 04/27] net: ieee802154: Give more details to the core about the channel configurations Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 05/27] net: mac802154: Convert the symbol duration into nanoseconds Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 06/27] net: mac802154: Set the symbol duration automatically Miquel Raynal
2022-01-12 22:25 ` Alexander Aring
2022-01-13 9:52 ` Miquel Raynal
2022-01-13 23:36 ` Alexander Aring
2022-01-14 10:18 ` Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 07/27] net: ieee802154: hwsim: Ensure frame checksum are valid Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 08/27] net: ieee802154: Drop symbol duration settings when the core does it already Miquel Raynal
2022-01-12 22:26 ` Alexander Aring
2022-01-13 11:16 ` Miquel Raynal
2022-01-13 23:34 ` Alexander Aring
2022-01-14 10:21 ` Miquel Raynal
2022-01-16 23:21 ` Alexander Aring
2022-01-17 9:12 ` Miquel Raynal
2022-01-17 23:38 ` Alexander Aring
2022-01-18 10:38 ` Miquel Raynal
2022-01-18 22:43 ` Alexander Aring
2022-01-19 22:26 ` Miquel Raynal
2022-01-19 23:26 ` Alexander Aring
2022-01-12 17:32 ` [wpan-next v2 09/27] net: ieee802154: Move IEEE 802.15.4 Kconfig main entry Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 10/27] net: mac802154: Include the softMAC stack inside the IEEE 802.15.4 menu Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 11/27] net: ieee802154: Move the address structure earlier Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 12/27] net: ieee802154: Add a kernel doc header to the ieee802154_addr structure Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 13/27] net: ieee802154: Return meaningful error codes from the netlink helpers Miquel Raynal
2022-01-12 17:32 ` [wpan-next v2 14/27] net: ieee802154: Add support for internal PAN management Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 15/27] net: ieee802154: Define a beacon frame header Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 16/27] net: ieee802154: Define frame types Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 17/27] net: ieee802154: Add support for scanning requests Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 18/27] net: mac802154: Handle scan requests Miquel Raynal
2022-01-12 22:44 ` Alexander Aring
2022-01-13 17:07 ` Miquel Raynal [this message]
2022-01-14 0:01 ` Alexander Aring
2022-01-14 18:44 ` Miquel Raynal
2022-01-16 22:44 ` Alexander Aring
2022-01-16 22:50 ` Alexander Aring
2022-01-17 9:00 ` Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 19/27] net: ieee802154: Full PAN management Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 20/27] net: ieee802154: Add support for beacon requests Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 21/27] net: mac802154: Handle beacons requests Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 22/27] net: ieee802154: Trace the registration of new PANs Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 23/27] net: mac802154: Add support for active scans Miquel Raynal
2022-01-12 23:16 ` Alexander Aring
2022-01-13 17:14 ` Miquel Raynal
2022-01-14 0:30 ` Alexander Aring
2022-01-14 0:39 ` Alexander Aring
2022-01-12 17:33 ` [wpan-next v2 24/27] net: mac802154: Add support for processing beacon requests Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 25/27] net: mac802154: Inform device drivers about scans Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 26/27] net: mac802154: Inform device drivers about beacon operations Miquel Raynal
2022-01-12 17:33 ` [wpan-next v2 27/27] net: ieee802154: ca8210: Refuse most of the scan operations Miquel Raynal
2022-01-12 22:48 ` Alexander Aring
2022-01-13 9:29 ` Miquel Raynal
2022-01-14 1:00 ` Alexander Aring
2022-01-14 18:37 ` Miquel Raynal
2022-01-16 22:48 ` Alexander Aring
2022-01-17 9:04 ` Miquel Raynal
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