linux-kernel - Re: netconsole breaks netpoll on bridge

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Message-Id: <CE582178-E749-473F-9D88-E6D7789A3B73@profihost.ag>
Date:	Mon, 16 Jun 2014 21:05:55 +0200
From:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
To:	Cong Wang <cwang@...pensource.com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	David Miller <davem@...emloft.net>,
	"bridge@...ts.linux-foundation.org" 
	<bridge@...ts.linux-foundation.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: netconsole breaks netpoll on bridge


> Am 16.06.2014 um 20:51 schrieb Cong Wang <cwang@...pensource.com>:
> 
> On Mon, Jun 16, 2014 at 11:41 AM, Stefan Priebe - Profihost AG
> <s.priebe@...fihost.ag> wrote:
>> 
>>> Am 16.06.2014 um 20:05 schrieb Cong Wang <cwang@...pensource.com>:
>>> 
>>> On Mon, Jun 16, 2014 at 5:51 AM, Stefan Priebe - Profihost AG
>>> <s.priebe@...fihost.ag> wrote:
>>>> Hi,
>>>> 
>>>> i'm using a vanilla 3.10.43 kernel and netconsole on top of a bridge.
>>>> 
>>>> netconsole is used with vmbr0 (bridge) which is on top of bond0.
>>>> 
>>>> If i want to add another bridge to vmbr0 is fails as long as netconsole
>>>> is in use.
>>>> 
>>>> # brctl addif vmbr0 fwpr2004p0
>>>> can't add fwpr2004p0 to bridge vmbr0: Unknown error 524
>>>> 
>>>> Kernel output:
>>>> netpoll: (null): fwpr2004p0 doesn't support polling, aborting
>>>> 
>>>> If i do rmmod netconsole - everything is working fine again.
>>> 
>>> This is expected, you can't add an interface which doesn't support
>>> netpoll to a bridge which is running netpoll.
>> 
>> Thanks, so i can't use netconsole at a bridge used for vms?
> 
> You can, but you need to make sure all the devices under
> this bridge support netpoll. Not considering mac learning,
> bridge just broadcasts all the packets to its ports, if one of them
> doesn't support netpoll, how could it work?

Ok i was trying to add a veth device so this is the problematic device.

>>> You should stop netpoll before adding it.
>> 
>> How to do that? What disadvantage does this have?
> 
> If you are using a redhat distro, run `service netconsole stop`.
> 
> Or you can disable it via configfs, check
> Documentation/networking/netconsole.txt.

Ok but this means disabling netconsole nothing I want.

Stefan
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