netdev - Re: 2.6.27.18: bnx2/tg3: BUG: "scheduling while atomic" trying to ifenslave a second interface to my bond

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Date:	Wed, 15 Apr 2009 12:56:42 -0400
From:	Paul Smith <paul@...-scientist.net>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	netdev@...r.kernel.org
Subject: Re: 2.6.27.18: bnx2/tg3: BUG: "scheduling while atomic" trying to
	ifenslave a second interface to my bond

On Tue, 2009-04-14 at 18:12 -0700, Jay Vosburgh wrote:
> 	I think I know what's going on.  I believe this patch will
> resolve things, but I won't be able to test it until tomorrow.  If you
> want to test this, great; if you want to wait, that's fine too.

Hi Jay; as I mentioned last night this patch is working fine for me so
far.

However, looking at the rest of this function it seems to me that there
are other locking issues, at least based on the documentation in the
header file:

 * Here are the locking policies for the two bonding locks:
 *
 * 1) Get bond->lock when reading/writing slave list.
 * 2) Get bond->curr_slave_lock when reading/writing bond->curr_active_slave.
 *    (It is unnecessary when the write-lock is put with bond->lock.)
 * 3) When we lock with bond->curr_slave_lock, we must lock with bond->lock
 *    beforehand.

For example, don't you need to hold bond->curr_slave_lock at least
around the "if (!bond->curr_active_slave)"?  What about around the
"bond_for_each_slave" loop?

Many of the other functions, later, also seem to work with
bond->curr_active_slave and they don't take this lock.

Unless I'm missing something, I think there are still more problems in
the locking in bond_alb_set_mac_address().

Thoughts?

> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index 8dc6fbb..b22467a 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -1708,10 +1708,8 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave
>   * Called with RTNL
>   */
>  int bond_alb_set_mac_address(struct net_device *bond_dev, void *addr)
> -	__releases(&bond->curr_slave_lock)
> -	__releases(&bond->lock)
>  	__acquires(&bond->lock)
> -	__acquires(&bond->curr_slave_lock)
> +	__releases(&bond->lock)
>  {
>  	struct bonding *bond = netdev_priv(bond_dev);
>  	struct sockaddr *sa = addr;
> @@ -1747,9 +1745,6 @@ int bond_alb_set_mac_address(struct net_device *bond_dev, void *addr)
>  		}
>  	}
>  
> -	write_unlock_bh(&bond->curr_slave_lock);
> -	read_unlock(&bond->lock);
> -
>  	if (swap_slave) {
>  		alb_swap_mac_addr(bond, swap_slave, bond->curr_active_slave);
>  		alb_fasten_mac_swap(bond, swap_slave, bond->curr_active_slave);
> @@ -1757,16 +1752,17 @@ int bond_alb_set_mac_address(struct net_device *bond_dev, void *addr)
>  		alb_set_slave_mac_addr(bond->curr_active_slave, bond_dev->dev_addr,
>  				       bond->alb_info.rlb_enabled);
>  
> -		alb_send_learning_packets(bond->curr_active_slave, bond_dev->dev_addr);
> +		read_lock(&bond->lock);
> +		alb_send_learning_packets(bond->curr_active_slave,
> +					  bond_dev->dev_addr);
>  		if (bond->alb_info.rlb_enabled) {
>  			/* inform clients mac address has changed */
> -			rlb_req_update_slave_clients(bond, bond->curr_active_slave);
> +			rlb_req_update_slave_clients(bond,
> +						     bond->curr_active_slave);
>  		}
> +		read_unlock(&bond->lock);
>  	}
>  
> -	read_lock(&bond->lock);
> -	write_lock_bh(&bond->curr_slave_lock);
> -
>  	return 0;
>  }
>  

-- 
Paul Smith <paul@...-scientist.net>

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