netdev - Re: [PATCH net] net: dsa: lan9303: avoid dsa_switch

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Message-ID: <20240911171932.yqt5emtb4xmrdqgq@skbuf>
Date: Wed, 11 Sep 2024 20:19:32 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
Cc: "andrew@...n.ch" <andrew@...n.ch>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"f.fainelli@...il.com" <f.fainelli@...il.com>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	"kuba@...nel.org" <kuba@...nel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net: dsa: lan9303: avoid dsa_switch_shutdown()

On Wed, Sep 11, 2024 at 05:09:08PM +0000, Sverdlin, Alexander wrote:
> On Wed, 2024-09-11 at 19:04 +0200, Alexander Sverdlin wrote:
> > > > The difference between that and this is the extra lan9303_disable_processing_port()
> > > > calls here. But while that does disable RX on switch ports, it still doesn't wait
> > > > for pending RX frames to be processed. So the race is still open. No?
> > 
> > besides from the below, I've expected this question... In the meanwhile I've tested
> > mv88e6xxx driver, but it (accidentally) has no MDIO race vs shutdown.
> > After some shallow review of the drivers I didn't find dev_get_drvdata <= mdio_read
> > pattern therefore I've posted this tested patch.
> > 
> > If you'd prefer to solve this centrally for all drivers, I can test your patch from
> > the MDIO-drvdata PoV.
> 
> But this would mean throwing away the whole
> "net: dsa: be compatible with masters which unregister on shutdown" work?

I did not propose anything (yet). I'm still trying to form a mental model
of what is broken and what works. Hence the request to test that change.

OTOH, this patch is equally throwing away the whole "net: dsa: be
compatible with masters which unregister on shutdown" work (for lan9303).