It seems many drivers do not respect napi_hash_del() contract.
When napi_hash_del() is used before netif_napi_del(), an RCU grace
period is needed before freeing NAPI object.
Fixes: 91815639d880 ("virtio-net: rx busy polling support") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>