netdev - Re: [PATCH net RESEND] vlan: don't allow to add VLAN on VLAN device

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Date:	Thu, 27 Feb 2014 21:41:33 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Ding Tianhong <dingtianhong@...wei.com>
Cc:	John Fastabend <john.r.fastabend@...el.com>,
	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net RESEND] vlan: don't allow to add VLAN on VLAN device

2014-02-27 21:26 GMT-08:00 Ding Tianhong <dingtianhong@...wei.com>:
> On 2014/2/28 11:45, 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 <dingtianhong@...wei.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.
>>
>> .John
>
> Yes, maybe I miss something, can you gave me a scene that the use of eth2.20.30?
> the device is created from vlan device eth2.20, than I will find a better way to fix it.

Is not QinQ (802.1ad) such as case [1]?

[1]: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8ad227ff89a7e6f05d07cd0acfd95ed3a24450ca
--
Florian
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