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

On 9/12/2021 7:12 PM, Vladimir Oltean wrote:

On Sun, Sep 12, 2021 at 07:06:25PM -0700, Florian Fainelli wrote:

quoted

On 9/12/2021 9:33 AM, Vladimir Oltean wrote:

quoted

On Sun, Sep 12, 2021 at 09:24:53AM -0700, Florian Fainelli wrote:

quoted

On 9/12/2021 9:19 AM, Vladimir Oltean wrote:

quoted

On Sun, Sep 12, 2021 at 09:13:36AM -0700, Florian Fainelli wrote:

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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.

Sorry, I have never tested the suspend/resume code path, mostly because
I don't know what would the easiest way be to wake up my systems from
suspend. If you could give me some pointers there I would be glad to
look into it.

If your systems support suspend/resume just do:

echo mem > /sys/power/state
or
echo standby > /sys/power/state

if they don't, then maybe a x86 VM with dsa_loop may precipitate the
problem, but since it uses DSA_TAG_PROTO_NONE, I doubt it, we would need to
pass traffic on the DSA devices for this warning to show up.

I figured out a working combination in the meanwhile, I even found a bug
in the process:
https://patchwork.kernel.org/project/netdevbpf/patch/20210912192805.1394305-1-vladimir.oltean@nxp.com/

However I did not see those messages getting printed while pinging after
system resume (note that none of the DSA switch drivers I tested with
did implement .suspend or .resume), with net-next or with linux-stable/linux-5.14.y.

Is there more to your setup to reproduce this issue?

All switch ports are brought up with a DHCP client, the issue is 
definitively intermittent and not frequent, I don't have suspend/resume 
working on 5.14.y yet, but going as far back as 5.10.y should let you 
see the same kind of messages.
-- 
Florian