Subject: Re: bonding reports interface up with 0 Mbps

From: zhuyj <[email-masked]>
Date: Fri, 5 Feb 2016 13:19:16 +0800

On 02/05/2016 08:43 AM, Tantilov, Emil S wrote:
>> -----Original Message-----
>> From: Jay Vosburgh [mailto:[email-masked]]
>> Sent: Thursday, February 04, 2016 4:37 PM
>> To: Tantilov, Emil S
>> Cc: [email-masked]; [email-masked]; zhuyj;
>> [email-masked]
>> Subject: Re: bonding reports interface up with 0 Mbps
>>
>> Jay Vosburgh <[email-masked]> wrote:
>> [...]
>>> 	Thinking about the trace again... Emil: what happens in the
>>> trace before this?  Is there ever a call to the ixgbe_get_settings?
>>> Does a NETDEV_UP or NETDEV_CHANGE event ever hit the bond_netdev_event
>>> function?
>> 	Emil kindly sent me the trace offline, and I think I see what's
>> going on.  It looks like the sequence of events is:
>>
>> bond_enslave ->
>> 	bond_update_speed_duplex (device is down, thus DUPLEX/SPEED_UNKNOWN)
>> 	[ do rest of enslavement, start miimon periodic work ]
>>
>> 	[ time passes, device goes carrier up ]
>>
>> ixgbe_service_task: eth1: NIC Link is Up 10 Gbps ->
>> 	netif_carrier_on (arranges for NETDEV_CHANGE notifier out of line)
>>
>> 	[ a few microseconds later ]
>>
>> bond_mii_monitor ->
>> 	bond_check_dev_link	(now is carrier up)
>> 	bond_miimon_commit ->	(emits "0 Mbps full duplex" message)
>> 		bond_lower_state_changed ->
>> 			bond_netdev_event (NETDEV_CHANGELOWERSTATE, is ignored)
>> 		bond_3ad_handle_link_change	(sees DUPLEX/SPEED_UNKNOWN)
>>
>> 	[ a few microseconds later, in response to ixgbe's netif_carrier_on ]
>>
>> notifier_call_chain ->
>> 	bond_netdev_event NETDEV_CHANGE ->
>> 		bond_update_speed_duplex (sees correct SPEED_10000/FULL) ->
>> 			bond_3ad_adapter_speed_duplex_changed (updates 802.3ad)
>>
>> 	Basically, the race is that the periodic bond_mii_monitor is
>> squeezing in between the link going up and bonding's update of the speed
>> and duplex in response to the NETDEV_CHANGE triggered by the driver's
>> netif_carrier_on call.  bonding ends up using the stale duplex and speed
>> information obtained at enslavement time.
>>
>> 	I think that, nowadays, the initial speed and duplex will pretty
>> much always be UNKNOWN, at least for real Ethernet devices, because it
>> will take longer to autoneg than the time between the dev_open and
>> bond_update_speed_duplex calls in bond_enslave.
>>
>> 	Adding a case to bond_netdev_event for CHANGELOWERSTATE works
>> because it's a synchronous call from bonding.  For purposes of fixing
>> this, it's more or less equivalent to calling bond_update_speed_duplex
> >from bond_miimon_commit (which is part of a test patch I posted earlier
>> today).
>>
>> 	If the above analysis is correct, then I would expect this patch
>> to make the problem go away:
>>
>> diff --git a/drivers/net/bonding/bond_main.c
>> b/drivers/net/bonding/bond_main.c
>> index 56b560558884..cabaeb61333d 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -2127,6 +2127,7 @@ static void bond_miimon_commit(struct bonding *bond)
>> 			continue;
>>
>> 		case BOND_LINK_UP:
>> +			bond_update_speed_duplex(slave);
>> 			bond_set_slave_link_state(slave, BOND_LINK_UP,
>> 						  BOND_SLAVE_NOTIFY_NOW);
>> 			slave->last_link_up = jiffies;
>>
>>
>> 	Emil, can you give just the above a test?
> Sure I'll fire it up.
Let me know the test result.

Thanks a lot.
Zhu Yanjun
> Thanks,
> Emil