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

[Amerigo Wang <amwang@redhat.com>]

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 unlock rtnl_lock before calling destroy_workqueue().

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..b781728 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4542,8 +4542,11 @@ static void bond_uninit(struct net_device *bond_dev)
 
 	bond_remove_proc_entry(bond);
 
-	if (bond->wq)
+	if (bond->wq) {
+		rtnl_unlock();
 		destroy_workqueue(bond->wq);
+		rtnl_lock();
+	}
 
 	netif_addr_lock_bh(bond_dev);
 	bond_mc_list_destroy(bond);