On Thu, 2014-02-27 at 19:45 -0800, John Fastabend wrote: > On 2/27/2014 6:43 PM, Ding Tianhong wrote: > > I run these steps: > > > > modprobe 8021q > > vconfig add eth2 20 > > vconfig add eth2.20 20 > > ifconfig eth2 xx.xx.xx.xx > > > > then the Call Trace happened: > > > > [...] > > > ======================================================================== > > > > The reason is that if add vlan on vlan dev, the vlan dev will create > > vlan_info, > > then the notification will let the real dev to run dev_set_rx_mode() and > > hold > > netif_addr_lock, and then the real dev will call ndo_set_rx_mode(), if the > > real > > dev is vlan dev, the ndo_set_rx_mode() will hold netif_addr_lock again, so > > deadlock > > happened. > > > > Don't allow to add vlan on vlan dev to fix this problem. > > > > Signed-off-by: Ding Tianhong <[email protected]> > > --- > > I'm not sure we can just disable stacked vlans. There might be something > using them today and they have worked in the past. Lets try to find a > better fix.
I don't think there's any deadlock possible here. We try to acquire the addr_list_lock for eth2.20, then the addr_list_lock for eth2. We never try to acquire them in the opposite order. The fix would involve telling lockdep about lock ordering between stacked net_devices (I have no idea how that's done). Ben. -- Ben Hutchings For every complex problem there is a solution that is simple, neat, and wrong.
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