netdev - Re: [Patch V2] bonding: fix potential deadlock in bond

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Date:	Wed, 31 Mar 2010 23:12:22 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Amerigo Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Jiri Pirko <jpirko@...hat.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	bonding-devel@...ts.sourceforge.net,
	Jay Vosburgh <fubar@...ibm.com>
Subject: Re: [Patch V2] bonding: fix potential deadlock in bond_uninit()

Amerigo Wang <amwang@...hat.com> writes:

> bond_uninit() is invoked with rtnl_lock held, when it does destroy_workqueue()
> which will potentially flush all works in this workqueue, if we hold rtnl_lock
> again in the work function, it will deadlock.
>
> So move destroy_workqueue() to destructor where rtnl_lock is not held any more,
> suggested by Eric.

The error handling on creating a bond device needs to be updated as well.

Eric


> Signed-off-by: WANG Cong <amwang@...hat.com>
> Cc: Jay Vosburgh <fubar@...ibm.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Stephen Hemminger <shemminger@...tta.com>
> Cc: Jiri Pirko <jpirko@...hat.com>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
>
> ---
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 5b92fbf..9f0aaa2 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4450,6 +4450,14 @@ static const struct net_device_ops bond_netdev_ops = {
>  	.ndo_vlan_rx_kill_vid	= bond_vlan_rx_kill_vid,
>  };
>  
> +static void bond_destructor(struct net_device *bond_dev)
> +{
> +	struct bonding *bond = netdev_priv(bond_dev);
> +	if (bond->wq)
> +		destroy_workqueue(bond->wq);
> +	free_netdev(bond_dev);
> +}
> +
>  static void bond_setup(struct net_device *bond_dev)
>  {
>  	struct bonding *bond = netdev_priv(bond_dev);
> @@ -4470,7 +4478,7 @@ static void bond_setup(struct net_device *bond_dev)
>  	bond_dev->ethtool_ops = &bond_ethtool_ops;
>  	bond_set_mode_ops(bond, bond->params.mode);
>  
> -	bond_dev->destructor = free_netdev;
> +	bond_dev->destructor = bond_destructor;
>  
>  	/* Initialize the device options */
>  	bond_dev->tx_queue_len = 0;
> @@ -4542,9 +4550,6 @@ static void bond_uninit(struct net_device *bond_dev)
>  
>  	bond_remove_proc_entry(bond);
>  
> -	if (bond->wq)
> -		destroy_workqueue(bond->wq);
> -
>  	netif_addr_lock_bh(bond_dev);
>  	bond_mc_list_destroy(bond);
>  	netif_addr_unlock_bh(bond_dev);
--
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