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

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

On Mon, 2017-12-04 at 17:31 +0800, Jason Wang wrote:

quoted

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.

...

quoted

  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