Subject: Re: [PATCH net-next V3] tun: add eBPF based queue selection method

From: Eric Dumazet <[email-masked]>
Date: Thu, 07 Dec 2017 14:11:49 -0800

On Mon, 2017-12-04 at 17:31 +0800, Jason Wang wrote:
> This patch introduces an eBPF based queue selection method. With
> this,
> the policy could be offloaded to userspace completely through a new
> ioctl TUNSETSTEERINGEBPF.

Sorry for the delay, I see this patch was merged already.

...

>  static void tun_free_netdev(struct net_device *dev)
>  {
>  	struct tun_struct *tun = netdev_priv(dev);
> @@ -1996,6 +2068,9 @@ static void tun_free_netdev(struct net_device
> *dev)
>  	free_percpu(tun->pcpu_stats);
>  	tun_flow_uninit(tun);
>  	security_tun_dev_free_security(tun->security);
> +	rtnl_lock();
> +	__tun_set_steering_ebpf(tun, NULL);
> +	rtnl_unlock();
>  }

I am pretty sure tun_free_netdev() (aka ->priv_destructor()) can be
called under RTNL (say from register_netdevice())

So this will dead lock badly ?