Subject: Re: [PATCH net-next] bonding: Fix RTNL: assertion failed at net/core/rtnetlink.c for 802.3ad mode

From: Ding Tianhong <[email-masked]>
Date: Wed, 19 Feb 2014 10:26:31 +0800

On 2014/2/19 7:18, Jay Vosburgh wrote:
> Ding Tianhong <[email-masked]> wrote:
> 
>> The problem was introduced by the commit 1d3ee88ae0d
>> (bonding: add netlink attributes to slave link dev).
>> The bond_set_active_slave() and bond_set_backup_slave()
>> will use rtmsg_ifinfo to send slave's states, so these
>> two functions should be called in RTNL.
>>
>> In 802.3ad mode, acquiring RTNL for the __enable_port and
>> __disable_port cases is difficult, as those calls generally
>> already hold the state machine lock, and cannot unconditionally
>> call rtnl_lock because either they already hold RTNL (for calls
>> via bond_3ad_unbind_slave) or due to the potential for deadlock
>> with bond_3ad_adapter_speed_changed, bond_3ad_adapter_duplex_changed,
>> bond_3ad_link_change, or bond_3ad_update_lacp_rate.  All four of
>> those are called with RTNL held, and acquire the state machine lock
>> second.  The calling contexts for __enable_port and __disable_port
>> already hold the state machine lock, and may or may not need RTNL.
>>
>> According to the Jay's opinion, I don't think it is a problem that
>> the slave don't send notify message synchronously when the status
>> changed, normally the state machine is running every 100 ms, send
>> the notify message at the end of the state machine if the slave's
>> state changed should be better.
>>
>> I fix the problem through these steps:
>>
>> 1). add a new function bond_set_slave_state() which could change
>>    the slave's state and call rtmsg_ifinfo() according to the input
>>    parameters called notify.
>>
>> 2). Add a new slave parameter which called should_notify, if the slave's state
>>    changed and don't notify yet, the parameter will be set to 1, and then if
>>    the slave's state changed again, the param will be set to 0, it indicate that
>>    the slave's state has been restored, no need to notify any one.
>>
>> 3). the __enable_port and __disable_port should not call rtmsg_ifinfo
>>    in the state machine lock, any change in the state of slave could
>>    set a flag in the slave, it will indicated that an rtmsg_ifinfo
>>    should be called at the end of the state machine.
>>
>> Cc: Jay Vosburgh <[email-masked]>
>> Cc: Veaceslav Falico <[email-masked]>
>> Cc: Andy Gospodarek <[email-masked]>
>> Signed-off-by: Ding Tianhong <[email-masked]>
>> ---
>> drivers/net/bonding/bond_3ad.c  | 22 ++++++++++++++++++++--
>> drivers/net/bonding/bond_main.c | 30 +++++++++++++++---------------
>> drivers/net/bonding/bonding.h   | 31 ++++++++++++++++++++++++++-----
>> 3 files changed, 61 insertions(+), 22 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
>> index e9edd84..c450d04 100644
>> --- a/drivers/net/bonding/bond_3ad.c
>> +++ b/drivers/net/bonding/bond_3ad.c
>> @@ -181,7 +181,7 @@ static inline int __agg_has_partner(struct aggregator *agg)
>>  */
>> static inline void __disable_port(struct port *port)
>> {
>> -	bond_set_slave_inactive_flags(port->slave);
>> +	bond_set_slave_inactive_flags(port->slave, false);
>> }
>>
>> /**
>> @@ -193,7 +193,7 @@ static inline void __enable_port(struct port *port)
>> 	struct slave *slave = port->slave;
>>
>> 	if ((slave->link == BOND_LINK_UP) && IS_UP(slave->dev))
>> -		bond_set_slave_active_flags(slave);
>> +		bond_set_slave_active_flags(slave, false);
>> }
>>
>> /**
>> @@ -2065,6 +2065,7 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>> 	struct list_head *iter;
>> 	struct slave *slave;
>> 	struct port *port;
>> +	int slave_should_notify = 0;
>>
>> 	read_lock(&bond->lock);
>> 	rcu_read_lock();
>> @@ -2122,8 +2123,25 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
>> 	}
>>
>> re_arm:
>> +	bond_for_each_slave_rcu(bond, slave, iter) {
>> +		if (slave->should_notify) {
>> +			slave_should_notify = 1;
>> +			break;
>> +		}
>> +	}
>> 	rcu_read_unlock();
>> 	read_unlock(&bond->lock);
>> +
>> +	if (slave_should_notify && rtnl_trylock()) {
>> +		bond_for_each_slave(bond, slave, iter) {
>> +			if (slave->should_notify) {
>> +				rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0,
>> +					     GFP_KERNEL);
>> +				slave->should_notify = 0;
>> +			}
>> +		}
>> +		rtnl_unlock();
>> +	}
>> 	queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
>> }
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 3bce855..1c14e64 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -829,21 +829,21 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
>> 	if (bond_is_lb(bond)) {
>> 		bond_alb_handle_active_change(bond, new_active);
>> 		if (old_active)
>> -			bond_set_slave_inactive_flags(old_active);
>> +			bond_set_slave_inactive_flags(old_active, true);
>> 		if (new_active)
>> -			bond_set_slave_active_flags(new_active);
>> +			bond_set_slave_active_flags(new_active, true);
>> 	} else {
>> 		rcu_assign_pointer(bond->curr_active_slave, new_active);
>> 	}
>>
>> 	if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) {
>> 		if (old_active)
>> -			bond_set_slave_inactive_flags(old_active);
>> +			bond_set_slave_inactive_flags(old_active, true);
>>
>> 		if (new_active) {
>> 			bool should_notify_peers = false;
>>
>> -			bond_set_slave_active_flags(new_active);
>> +			bond_set_slave_active_flags(new_active, true);
>>
>> 			if (bond->params.fail_over_mac)
>> 				bond_do_fail_over_mac(bond, new_active,
>> @@ -1462,14 +1462,14 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>>
>> 	switch (bond->params.mode) {
>> 	case BOND_MODE_ACTIVEBACKUP:
>> -		bond_set_slave_inactive_flags(new_slave);
>> +		bond_set_slave_inactive_flags(new_slave, true);
>> 		break;
>> 	case BOND_MODE_8023AD:
>> 		/* in 802.3ad mode, the internal mechanism
>> 		 * will activate the slaves in the selected
>> 		 * aggregator
>> 		 */
>> -		bond_set_slave_inactive_flags(new_slave);
>> +		bond_set_slave_inactive_flags(new_slave, true);
>> 		/* if this is the first slave */
>> 		if (!prev_slave) {
>> 			SLAVE_AD_INFO(new_slave).id = 1;
>> @@ -1487,7 +1487,7 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> 	case BOND_MODE_TLB:
>> 	case BOND_MODE_ALB:
>> 		bond_set_active_slave(new_slave);
>> -		bond_set_slave_inactive_flags(new_slave);
>> +		bond_set_slave_inactive_flags(new_slave, true);
>> 		break;
>> 	default:
>> 		pr_debug("This slave is always active in trunk mode\n");
>> @@ -2009,7 +2009,7 @@ static void bond_miimon_commit(struct bonding *bond)
>>
>> 			if (bond->params.mode == BOND_MODE_ACTIVEBACKUP ||
>> 			    bond->params.mode == BOND_MODE_8023AD)
>> -				bond_set_slave_inactive_flags(slave);
>> +				bond_set_slave_inactive_flags(slave, true);
>>
>> 			pr_info("%s: link status definitely down for interface %s, disabling it\n",
>> 				bond->dev->name, slave->dev->name);
>> @@ -2555,7 +2555,7 @@ static void bond_ab_arp_commit(struct bonding *bond)
>> 				slave->link = BOND_LINK_UP;
>> 				if (bond->current_arp_slave) {
>> 					bond_set_slave_inactive_flags(
>> -						bond->current_arp_slave);
>> +						bond->current_arp_slave, true);
>> 					bond->current_arp_slave = NULL;
>> 				}
>>
>> @@ -2575,7 +2575,7 @@ static void bond_ab_arp_commit(struct bonding *bond)
>> 				slave->link_failure_count++;
>>
>> 			slave->link = BOND_LINK_DOWN;
>> -			bond_set_slave_inactive_flags(slave);
>> +			bond_set_slave_inactive_flags(slave, true);
>>
>> 			pr_info("%s: link status definitely down for interface %s, disabling it\n",
>> 				bond->dev->name, slave->dev->name);
>> @@ -2650,7 +2650,7 @@ static bool bond_ab_arp_probe(struct bonding *bond)
>> 		}
>> 	}
>>
>> -	bond_set_slave_inactive_flags(curr_arp_slave);
>> +	bond_set_slave_inactive_flags(curr_arp_slave, true);
> 
> 	This...
> 
>> 	bond_for_each_slave(bond, slave, iter) {
>> 		if (!found && !before && IS_UP(slave->dev))
>> @@ -2670,7 +2670,7 @@ static bool bond_ab_arp_probe(struct bonding *bond)
>> 			if (slave->link_failure_count < UINT_MAX)
>> 				slave->link_failure_count++;
>>
>> -			bond_set_slave_inactive_flags(slave);
>> +			bond_set_slave_inactive_flags(slave, true);
> 
> 	[ but not this one ]
> 
>> 			pr_info("%s: backup interface %s is now down\n",
>> 				bond->dev->name, slave->dev->name);
>> @@ -2688,7 +2688,7 @@ static bool bond_ab_arp_probe(struct bonding *bond)
>> 	}
>>
>> 	new_slave->link = BOND_LINK_BACK;
>> -	bond_set_slave_active_flags(new_slave);
>> +	bond_set_slave_active_flags(new_slave, true);
> 
> 	and this should arguably never send an rtmsg_ifinfo
> notification.
> 
> 	My presumption is that the notification is to indicate that the
> interface has actually changed state in a meaningful way, but these
> calls are internal settings of the flags to allow the ARP monitor to
> search for a slave to become active when there are no active slaves
> (according to ARP monitor).  The flag setting to active or backup is to
> permit the ARP monitor's response logic to do the right thing when
> deciding if the test slave (current_arp_slave) is up or not.
> 
> 	What will happen here is that, for as long as all slaves are
> down, each cycle through the curr_arp_slave will shift to the next slave
> in the list, the flags will be adjusted for the previous and now-current
> arp slaves, and a pass of the ARP monitor will complete (send ARPs, next
> time through, check for any replies).
> 
> 	As the patch is written, while all slaves are down this will
> generate an rtmsg_ifinfo call for each of two slaves during each pass of
> the ARP monitor, until such time that any slave becomes active.
> 
> 	I haven't heard back from anybody about what the rtmsg_ifinfo
> notifications are used for, so I'm not 100% sure this is incorrect.  It
> doesn't seem like a proper usage, though, since the slave is not
> actually transitioning to an "up" or "down" state that is usable.
> 
> 	The way the code is written in the patch, "false" doesn't mean
> "never notify," it means "notify later," which isn't quite what I had
> meant.
> 
> 	I may be concerned about nothing here, and the extra
> notifications may be harmless.  In the absence of feedback, we could
> apply the patch as-is and if there are issues, fix them later.
> 
Hi, Joe:

I totally agree with you, but this patch is fix for 802.3ad warning message in original idea,
I found the monitors facing the same problem, but I think it would be better to fix them later,
I will review monitor for every mode and fix them, do you agree with me, otherwise I will fix
them in this big patch? 

Regards
Ding

> 	-J
> 
> 
>> 	bond_arp_send_all(bond, new_slave);
>> 	new_slave->jiffies = jiffies;
>> 	rcu_assign_pointer(bond->current_arp_slave, new_slave);
>> @@ -3035,9 +3035,9 @@ static int bond_open(struct net_device *bond_dev)
>> 		bond_for_each_slave(bond, slave, iter) {
>> 			if ((bond->params.mode == BOND_MODE_ACTIVEBACKUP)
>> 				&& (slave != bond->curr_active_slave)) {
>> -				bond_set_slave_inactive_flags(slave);
>> +				bond_set_slave_inactive_flags(slave, true);
>> 			} else {
>> -				bond_set_slave_active_flags(slave);
>> +				bond_set_slave_active_flags(slave, true);
>> 			}
>> 		}
>> 		read_unlock(&bond->curr_slave_lock);
>> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>> index 86ccfb9..1f51a5f 100644
>> --- a/drivers/net/bonding/bonding.h
>> +++ b/drivers/net/bonding/bonding.h
>> @@ -195,7 +195,8 @@ struct slave {
>> 	s8     new_link;
>> 	u8     backup:1,   /* indicates backup slave. Value corresponds with
>> 			      BOND_STATE_ACTIVE and BOND_STATE_BACKUP */
>> -	       inactive:1; /* indicates inactive slave */
>> +	       inactive:1, /* indicates inactive slave */
>> +	       should_notify:1; /* indicateds whether the state changed */
>> 	u8     duplex;
>> 	u32    original_mtu;
>> 	u32    link_failure_count;
>> @@ -303,6 +304,24 @@ static inline void bond_set_backup_slave(struct slave *slave)
>> 	}
>> }
>>
>> +static inline void bond_set_slave_state(struct slave *slave,
>> +					int slave_state, bool notify)
>> +{
>> +	if (slave->backup == slave_state)
>> +		return;
>> +
>> +	slave->backup = slave_state;
>> +	if (notify) {
>> +		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_KERNEL);
>> +		slave->should_notify = 0;
>> +	} else {
>> +		if (slave->should_notify)
>> +			slave->should_notify = 0;
>> +		else
>> +			slave->should_notify = 1;
>> +	}
>> +}
>> +
>> static inline void bond_slave_state_change(struct bonding *bond)
>> {
>> 	struct list_head *iter;
>> @@ -394,17 +413,19 @@ static inline void bond_netpoll_send_skb(const struct slave *slave,
>> }
>> #endif
>>
>> -static inline void bond_set_slave_inactive_flags(struct slave *slave)
>> +static inline void bond_set_slave_inactive_flags(struct slave *slave,
>> +						 bool notify)
>> {
>> 	if (!bond_is_lb(slave->bond))
>> -		bond_set_backup_slave(slave);
>> +		bond_set_slave_state(slave, BOND_STATE_BACKUP, notify);
>> 	if (!slave->bond->params.all_slaves_active)
>> 		slave->inactive = 1;
>> }
>>
>> -static inline void bond_set_slave_active_flags(struct slave *slave)
>> +static inline void bond_set_slave_active_flags(struct slave *slave,
>> +					       bool notify)
>> {
>> -	bond_set_active_slave(slave);
>> +	bond_set_slave_state(slave, BOND_STATE_ACTIVE, notify);
>> 	slave->inactive = 0;
>> }
>>
>> -- 
>> 1.8.0
>>
>>
> 
> ---
> 	-Jay Vosburgh, IBM Linux Technology Center, [email-masked]
> 
> 
> .
>