From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] ibm_newemac: emac_close() needs to call
 netif_carrier_off()
Date: Wed, 19 Aug 2009 14:34:03 -0700 (PDT)
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From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 19 Aug 2009 14:11:36 -0700

> On Wed, 19 Aug 2009 14:00:00 -0700 (PDT)
> Petri Gynther <pgynther@google.com> wrote:
> 
>> When ibm_newemac netdev instance is shutdown with "ifconfig down",
>> the netdev interface does not go properly down. netif_carrier_ok()
>> keeps returning TRUE even after "ifconfig down".
>> 
>> The problem can be seen when ibm_newemac instances are slaves of
>> a bonding interface. The bonding interface code uses netif_carrier_ok()
>> to determine the link status of its slaves. When ibm_newemac slave is
>> shutdown with "ifconfig down", the bonding interface won't detect any
>> link status change because netif_carrier_ok() keeps returning TRUE.
> 
> Bonding should be testing for netif_running() && netif_carrier_ok().
> 
> In many devices state of carrier is undefined when device is down.

But if you check all of the drivers, ethernet in particular, the
convention is to call netif_carrier_off() in foo_close().