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    Subject[Patch V2] bonding: fix potential deadlock in bond_uninit()

    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.

    Signed-off-by: WANG Cong <amwang@redhat.com>
    Cc: Jay Vosburgh <fubar@us.ibm.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Stephen Hemminger <shemminger@vyatta.com>
    Cc: Jiri Pirko <jpirko@redhat.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.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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