[PATCH] igb: reinit_locked() should be called with rtnl_lock

[Francesco Ruggeri]

We observed a panic in igb_reset_task caused by this race condition
when doing a reboot -f:

        kworker                 reboot -f

        igb_reset_task
        igb_reinit_locked
        igb_down
        napi_synchronize
                                __igb_shutdown
                                igb_clear_interrupt_scheme
                                igb_free_q_vectors
                                igb_free_q_vector
                                adapter->q_vector[v_idx] = NULL;
        napi_disable
        Panics trying to access
        adapter->q_vector[v_idx].napi_state

This commit applies to igb the same changes that were applied to ixgbe
in commit 8f4c5c9fb87a ("ixgbe: reinit_locked() should be called with
rtnl_lock") and commit 88adce4ea8f9 ("ixgbe: fix possible race in
reset subtask").

Signed-off-by: Francesco Ruggeri <frugg...@arista.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c 
b/drivers/net/ethernet/intel/igb/igb_main.c
index 8bb3db2cbd41..b79a78e102f3 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6224,9 +6224,11 @@ static void igb_reset_task(struct work_struct *work)
        struct igb_adapter *adapter;
        adapter = container_of(work, struct igb_adapter, reset_task);
 
+       rtnl_lock();
        igb_dump(adapter);
        netdev_err(adapter->netdev, "Reset adapter\n");
        igb_reinit_locked(adapter);
+       rtnl_unlock();
 }
 
 /**