From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next V3] tun: add eBPF based queue selection method
Date: Thu, 07 Dec 2017 14:11:49 -0800
Message-ID: <1512684709.25033.18.camel@gmail.com>
References: <1512379883-11887-1-git-send-email-jasowang@redhat.com>
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Cc: mst@redhat.com, willemdebruijn.kernel@gmail.com,
        tom@herbertland.com, aconole@redhat.com, wexu@redhat.com
To: Jason Wang <jasowang@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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In-Reply-To: <1512379883-11887-1-git-send-email-jasowang@redhat.com>
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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 ?