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

[Jason Wang <jasowang@redhat.com>]

On 2017年12月08日 06:11, Eric Dumazet wrote:
> 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 ?
>
>

Unfortunately yes. Will switch to use spinlock (tun->lock) to 
synchronize here.

Thanks