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

[Jason Wang]

On 2017å12æ08æ 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.
>
> ...
>
> >  Âstatic void tun_free_netdev(struct net_device *dev)
> >  Â{
> >  Â	struct tun_struct *tun = netdev_priv(dev);
> > @@ -1996,6 +2068,9 @@ static void tun_free_netdev(struct net_device
> > *dev)
> >  Â	free_percpu(tun->pcpu_stats);
> >  Â	tun_flow_uninit(tun);
> >  Â	security_tun_dev_free_security(tun->security);
> > +	rtnl_lock();
> > +	__tun_set_steering_ebpf(tun, NULL);
> > +	rtnl_unlock();
> >  Â}
> 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