On Fri, 2016-09-02 at 08:30 -0600, David Ahern wrote: > This check duplicates what netdev_rx_handler_register does. Why not > move the call to netdev_rx_handler_register here and then call > unregister on failure paths?
As soon as you call netdev_rx_handler_register(), incoming packets will hit your driver and we'll likely crash since the enslaving is not done yet. Really think about RCU, we do rcu_assign_pointer() because we want all prior changes being committed to memory before 'enabling' readers to see the updated rcu protected pointer. There are 9 call sites where netdev_rx_handler_register() is used. We can get rid of the extra check in netdev_rx_handler_register() once all of them are using netdev_is_rx_handler_busy() Since this patch takes care of bonding only, we need to keep the existing check in netdev_rx_handler_register() Anyway, we are speaking of control function, an extra check is simply safer, like all the ASSERT_RTNL() we do have...
