On 2014/3/5 8:10, Ben Hutchings wrote: > 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 <dingtianh...@huawei.com> >>> --- >> >> 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. >
Yep, it is a warning when the lockdep is open, I review the code again, and the deadlock would not happen, just the same class of locks twice, so I think it is not a bugfix, just like a optimization. Regards Ding -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
