From: Kloetzke Jan <Jan.Kloetzke@xxxxxxx> Date: Thu, 18 Apr 2019 08:02:59 +0000 > I think this assumption is not correct. As far as I understand the > networking code it is still possible that the ndo_start_xmit callback > is called while ndo_stop is running and even after ndo_stop has > returned. You can only be sure after unregister_netdev() has returned. > Maybe some networking folks can comment on that. The kernel loops over the devices being unregistered, and first it clears the __LINK_STATE_START on all of them, then it invokes ->ndo_stop() on all of them. __LINK_STATE_START controls what netif_running() returns. All calls to ->ndo_start_xmit() are guarded by netif_running() checks. So when ndo_stop is invoked you should get no more ndo_start_xmit invocations on that device. Otherwise how could you shut down DMA resources and turn off the TX engine properly?
