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

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Date:   Sun, 12 Sep 2021 19:33:41 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [RFC PATCH net] net: dsa: flush switchdev workqueue before
 tearing down CPU/DSA ports

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