netconsole: don't call __netpoll_cleanup() while atomic

[ Upstream commit 3f315bef23075ea8a98a6fe4221a83b83456d970 ]

__netpoll_cleanup() is called in netconsole_netdev_event() while holding a
spinlock. Release/acquire the spinlock before/after it and restart the
loop. Also, disable the netconsole completely, because we won't have chance
after the restart of the loop, and might end up in a situation where
nt->enabled == 1 and nt->np.dev == NULL.

Change-Id: Ia364ec98e046fd5e7527d7104b384295afb860a6
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Merge "netconsole: don't call __netpoll_cleanup() while atomic" into kk4.4