Re: [PATCH net-next 2/3] net: stmmac: add support for RZ/N1 GMAC

From: Romain Gantois <romain.gantois@bootlin.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: "Romain Gantois" <romain.gantois@bootlin.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Magnus Damm" <magnus.damm@gmail.com>,
	"Alexandre Torgue" <alexandre.torgue@foss.st.com>,
	"Jose Abreu" <joabreu@synopsys.com>,
	"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
	"Clément Léger" <clement.leger@bootlin.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH net-next 2/3] net: stmmac: add support for RZ/N1 GMAC
Date: Tue, 2 Apr 2024 18:04:20 +0200 (CEST)	[thread overview]
Message-ID: <36a4a94f-494f-2fef-11e1-8b45011c1263@bootlin.com> (raw)
In-Reply-To: <ZgwoygldsA1V8fs9@shell.armlinux.org.uk>

Hello Russell,

On Tue, 2 Apr 2024, Russell King (Oracle) wrote:

> > I'm afraid that this fails at one of the most basic principles of kernel
> > multi-threaded programming. stmmac_dvr_probe() as part of its work calls
> > register_netdev() which publishes to userspace the network device.
> > 
> > Everything that is required must be setup _prior_ to publication to
> > userspace to avoid races, because as soon as the network device is
> > published, userspace can decide to bring that interface up. If one
> > hasn't finished the initialisation, the interface can be brought up
> > before that initialisation is complete.
...
> 
> I'm not going to say that the two patches threaded to this email are
> "sane" but at least it avoids the problem. socfpga still has issues
> with initialisation done after register_netdev() though.

Thanks a lot for providing a fix to this issue, introducing new pcs_init/exit() 
hooks seems like the best solution at this time, I'll make sure to integrate 
those patches in the v2 for this series.

Thanks,

-- 
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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