Re: [RFC PATCH net] net: dsa: flush switchdev workqueue before tearing down CPU/DSA ports

Florian Fainelli
2021-09-12T16:24:59Z

On 9/12/2021 9:19 AM, Vladimir Oltean wrote:
> On Sun, Sep 12, 2021 at 09:13:36AM -0700, Florian Fainelli wrote:
>> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
>>
>> Did you post this as a RFC for a particular reason, or just to give
>> reviewers some time?
>
> Both.
>
> In principle there's nothing wrong with what this patch does, only
> perhaps maybe something with what it doesn't do.
>
> We keep saying that a network interface should be ready to pass traffic
> as soon as it's registered, but that "walk dst->ports linearly when
> calling dsa_port_setup" might not really live up to that promise.

That promise most definitively existed back when Lennert wrote this code
and we had an array of ports and the switch drivers brought up their
port in their ->setup() method, nowadays, not so sure anymore because of
the .port_enable() as much as the list.

This is making me wonder whether the occasional messages I am seeing on
system suspend from __dev_queue_xmit: Virtual device %s asks to queue
packet! might have something to do with that and/or the inappropriate
ordering between suspending the switch and the DSA master.

>
> So while we do end up bringing all ports up at the end of
> dsa_tree_setup_switches, I think for consistency we should do the same
> thing there, i.e. bring the shared ports up first, then the user ports.
> That way, the user ports should really be prepared to pass traffic as
> soon as they get registered.
>
> But I don't really know what kind of story to build around that to
> include it as part of this patch, other than consistency. For teardown,
> I think it is much more obvious to see an issue.
>

--
Florian