Subject: Re: bonding reports interface up with 0 Mbps

From: zhuyj <[email-masked]>
Date: Thu, 4 Feb 2016 14:44:49 +0800

On 02/04/2016 01:57 PM, Jay Vosburgh wrote:
> Tantilov, Emil S <[email-masked]> wrote:
>
>> We are seeing an occasional issue where the bonding driver may report interface up with 0 Mbps:
>> bond0: link status definitely up for interface eth0, 0 Mbps full duplex
>>
>> So far in all the failed traces I have collected this happens on NETDEV_CHANGELOWERSTATE event:
>>
>> <...>-20533 [000] .... 81811.041241: ixgbe_service_task: eth1: NIC Link is Up 10 Gbps, Flow Control: RX/TX
>> <...>-20533 [000] .... 81811.041257: ixgbe_check_vf_rate_limit <-ixgbe_service_task
>> <...>-20533 [000] .... 81811.041272: ixgbe_ping_all_vfs <-ixgbe_service_task
>> kworker/u48:0-7503  [010] .... 81811.041345: ixgbe_get_stats64 <-dev_get_stats
>> kworker/u48:0-7503  [010] .... 81811.041393: bond_netdev_event: eth1: event: 1b
>> kworker/u48:0-7503  [010] .... 81811.041394: bond_netdev_event: eth1: IFF_SLAVE
>> kworker/u48:0-7503  [010] .... 81811.041395: bond_netdev_event: eth1: slave->speed = ffffffff
>> <...>-20533 [000] .... 81811.041407: ixgbe_ptp_overflow_check <-ixgbe_service_task
>> kworker/u48:0-7503  [010] .... 81811.041407: bond_mii_monitor: bond0: link status definitely up for interface eth1, 0 Mbps full duplex
> 	From looking at the code that prints this, the "full" duplex is
> probably actually DUPLEX_UNKNOWN, but the netdev_info uses the
> expression slave->duplex ? "full" : "half", so DUPLEX_UNKNOWN at 0xff
> would print "full."
>
> 	This is what ixgbe_get_settings returns for speed and duplex if
> it is called when carrier is off.

I agree with you totally. I think it is the root cause.

Best Regards!
Zhu Yanjun

>
>> As a proof of concept I added NETDEV_CHANGELOWERSTATE in bond_slave_netdev_event() along with NETDEV_UP/CHANGE:
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 56b5605..a9dac4c 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -3014,6 +3014,7 @@ static int bond_slave_netdev_event(unsigned long event,
>> 		break;
>> 	case NETDEV_UP:
>> 	case NETDEV_CHANGE:
>> +	case NETDEV_CHANGELOWERSTATE:
>> 		bond_update_speed_duplex(slave);
>> 		if (BOND_MODE(bond) == BOND_MODE_8023AD)
>> 			bond_3ad_adapter_speed_duplex_changed(slave);
>>
>> With this change I have not seen 0 Mbps reported by the bonding driver (around 12 hour test up to this point
>> vs. 2-3 hours otherwise). Although I suppose it could also be some sort of race/timing issue with bond_mii_monitor().
> 	This change as a fix seems kind of odd, since CHANGELOWERSTATE
> is generated by bonding itself.  Perhaps the net effect is to add a
> delay and then update the speed and duplex, masking the actual problem.
>
> 	Emil, if I recall correctly, the test patch I send that uses the
> notifiers directly instead of miimon (specify miimon=0 and have bonding
> respond to the notifiers) handled everything properly, right?  If so I
> can split that up and submit it properly; it seems more like a feature
> than a straightforward bug fix, so I'm not sure it's appropriate for
> net.
>
> 	As a possibly less complex alternative for the miimon > 0 case,
> could you try the following:
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 56b560558884..ac8921e65f26 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -2120,6 +2120,7 @@ static void bond_miimon_commit(struct bonding *bond)
>   {
>   	struct list_head *iter;
>   	struct slave *slave, *primary;
> +	int link_state;
>   
>   	bond_for_each_slave(bond, slave, iter) {
>   		switch (slave->new_link) {
> @@ -2127,6 +2128,10 @@ static void bond_miimon_commit(struct bonding *bond)
>   			continue;
>   
>   		case BOND_LINK_UP:
> +			link_state = bond_check_dev_link(bond, slave->dev, 0);
> +			if (!link_state)
> +				continue;
> +			bond_update_speed_duplex(slave);
>   			bond_set_slave_link_state(slave, BOND_LINK_UP,
>   						  BOND_SLAVE_NOTIFY_NOW);
>   			slave->last_link_up = jiffies;
>
>
> 	This will make bonding recheck the link state and update the
> speed and duplex after it acquires RTNL to commit a link change.  This
> probably still has a race, since the change of carrier state in the
> device is not mutexed by anything bonding can acquire (so it can always
> change as soon as it's checked).
>
> 	Thanks,
>
> 	-J
>
> ---
> 	-Jay Vosburgh, [email-masked]