netdev - Re: [PATCH net] net: dsa: link interfaces with the DSA master to get rid of lockdep warnings

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Message-ID: <20200713164728.GH1078057@lunn.ch>
Date:   Mon, 13 Jul 2020 18:47:28 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, f.fainelli@...il.com,
        vivien.didelot@...il.com, xiyou.wangcong@...il.com,
        ap420073@...il.com
Subject: Re: [PATCH net] net: dsa: link interfaces with the DSA master to get
 rid of lockdep warnings

> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 743caabeaaa6..a951b2a7d79a 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -1994,6 +1994,13 @@ int dsa_slave_create(struct dsa_port *port)
>  			   ret, slave_dev->name);
>  		goto out_phy;
>  	}
> +	rtnl_lock();
> +	ret = netdev_upper_dev_link(master, slave_dev, NULL);
> +	rtnl_unlock();
> +	if (ret) {
> +		unregister_netdevice(slave_dev);
> +		goto out_phy;
> +	}

Hi Vladimir

A common pattern we see in bugs is that the driver sets up something
critical after calling register_netdev(), not realising that that call
can go off and really start using the interface before it returns. So
in general, i like to have register_netdev() last, nothing after it.

Please could you move this before register_netdev().

Thanks
	Andrew