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

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Message-ID: <20250228112840.00003e24@gmail.com>
Date: Fri, 28 Feb 2025 11:28:40 +0800
From: Furong Xu <0x1207@...il.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, 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, 27 Feb 2025 15:05:07 +0000
"Russell King (Oracle)" <rmk+kernel@...linux.org.uk> 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>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 84d8b1c9f6d4..9462d05c40c8 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -7757,8 +7757,6 @@ void stmmac_dvr_remove(struct device *dev)
>  
>  	pm_runtime_get_sync(dev);
>  
> -	stmmac_stop_all_dma(priv);
> -	stmmac_mac_set(priv, priv->ioaddr, false);
>  	unregister_netdev(ndev);
>  
>  #ifdef CONFIG_DEBUG_FS

We always build stmmac driver as built-in.
Tried to build stmmac driver as a module, but some complicated dependencies were
reported in our down-stream kernel :(
I can not test this patch, so:

Reviewed-by: Furong Xu <0x1207@...il.com>