netconsole regression w/ 8d8fc29d

[Rik van Riel]

After commit 8d8fc29d02a33e4bd5f4fa47823c1fd386346093
(netpoll: disable netpoll when enslave a device), it is
no longer possible to use netconsole together with bridged
KVM guests.

I can see why the change looked reasonable from a networking
point of view, but this has completely disabled netconsole
functionality for a common KVM use case.

After the change, netconsole refuses to bind to eth0.

Since the bridge interface does not support polling,
netconsole cannot use that, either.

I am now reduced to taking digital photos of the last screen
of a kernel oops, instead of getting oopses streamed to my
logging server.

To me the "unpredictable results" were way preferable to
what we have now.

Is there a way forward to restore netconsole functionality
for people who use KVM with bridging, or is it best to just
revert this commit?

commit 8d8fc29d02a33e4bd5f4fa47823c1fd386346093
Author: Amerigo Wang <amwang@xxxxxxxxxx>
Date:   Thu May 19 21:39:10 2011 +0000

    netpoll: disable netpoll when enslave a device

    V3: rename NETDEV_ENSLAVE to NETDEV_JOIN

    Currently we do nothing when we enslave a net device which is 
running netcon
    Neil pointed out that we may get weird results in such case, so 
let's disabl
    netpoll on the device being enslaved. I think it is too harsh to 
prevent
    the device being ensalved if it is running netconsole.

    By the way, this patch also removes the NETDEV_GOING_DOWN from 
netconsole
    netdev notifier, because netpoll will check if the device is 
running or not
    and we don't handle NETDEV_PRE_UP neither.

    This patch is based on net-next-2.6.

    Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
    Cc: Neil Horman <nhorman@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>


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