netdev - Re: [PATCH RFC net-next 2/5] net: stmmac: remove redundant racy tear-down in stmmac_dvr

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Message-ID: <c8117288-5ef9-445c-a14d-28b2756e5944@lunn.ch>
Date: Thu, 27 Feb 2025 23:16:41 +0100
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Jon Hunter <jonathanh@...dia.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>,
	Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH RFC net-next 2/5] net: stmmac: remove redundant racy
 tear-down in stmmac_dvr_remove()

On Thu, Feb 27, 2025 at 03:05:07PM +0000, Russell King (Oracle) wrote:
> While the network device is registered, it is published to userspace,
> and thus userspace can change its state. This means calling
> functions such as stmmac_stop_all_dma() and stmmac_mac_set() are
> racy.
> 
> Moreover, unregister_netdev() will unpublish the network device, and
> then if appropriate call the .ndo_stop() method, which is
> stmmac_release(). This will first call phylink_stop() which will
> synchronously take the link down, resulting in stmmac_mac_link_down()
> and stmmac_mac_set(, false) being called.
> 
> stmmac_release() will also call stmmac_stop_all_dma().
> 
> Consequently, neither of these two functions need to called prior
> to unregister_netdev() as that will safely call paths that will
> result in this work being done if necessary.
> 
> Remove these redundant racy calls.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew