netdev - Re: [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove

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Date: Mon, 27 Nov 2023 08:11:17 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Andrew Lunn <andrew@...n.ch>
Cc: nicolas.ferre@...rochip.com, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, hkallweit1@...il.com,
 linux@...linux.org.uk, jgarzik@...ox.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove



On 26.11.2023 19:13, Andrew Lunn wrote:
>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>> index cebae0f418f2..73d041af3de1 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -5165,11 +5165,11 @@ static void macb_remove(struct platform_device *pdev)
>>  
>>  	if (dev) {
>>  		bp = netdev_priv(dev);
>> +		unregister_netdev(dev);
>>  		phy_exit(bp->sgmii_phy);
>>  		mdiobus_unregister(bp->mii_bus);
>>  		mdiobus_free(bp->mii_bus);
>>  
>> -		unregister_netdev(dev);
>>  		tasklet_kill(&bp->hresp_err_tasklet);
> 
> 
> I don't know this driver...
> 
> What does this tasklet do? 

It handles bus errors that my happens while DMA fetches data from system
memory. It re-initializes the TX/RX, DMA buffers, clear interrupts,
stop/start all tx queues.

> Is it safe for it to run after the netdev
> is unregistered, and the PHY and the mdio bus is gone? 

Not really, as it accesses netdev specific data.

> Maybe this
> tasklet_kill should be after the interrupt is disabled, but before the
> netdev is unregistered?

That would be a better place, indeed.

Thank you,
Claudiu Beznea

> 
> If you have one bug here, there might be others.
> 
> 	Andrew