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

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Date: Tue, 2 Apr 2024 18:04:20 +0200 (CEST)
From: Romain Gantois <romain.gantois@...tlin.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
cc: Romain Gantois <romain.gantois@...tlin.com>, 
    "David S. Miller" <davem@...emloft.net>, 
    Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
    Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>, 
    Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
    Conor Dooley <conor+dt@...nel.org>, 
    Geert Uytterhoeven <geert+renesas@...der.be>, 
    Magnus Damm <magnus.damm@...il.com>, 
    Alexandre Torgue <alexandre.torgue@...s.st.com>, 
    Jose Abreu <joabreu@...opsys.com>, 
    Maxime Coquelin <mcoquelin.stm32@...il.com>, 
    Clément Léger <clement.leger@...tlin.com>, 
    Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org, 
    devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
    linux-renesas-soc@...r.kernel.org, 
    linux-stm32@...md-mailman.stormreply.com, 
    linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net-next 2/3] net: stmmac: add support for RZ/N1 GMAC

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