When reloading mlxen there are messages in the logs:

can't re-use a leaf (various leaf names)!

then, when trying to read these leafs - the kernel crashes.

Fix: The order of releasing resources in mlxen needed to be corrected.



-       if (priv->sysctl)
-               sysctl_ctx_free(&priv->conf_ctx);
-
        cancel_delayed_work(&priv->stats_task);
        /* flush any pending task for this netdev */
        flush_workqueue(mdev->workqueue);
@@ -937,6 +934,10 @@ void mlx4_en_destroy_netdev(struct net_device *dev
        mutex_unlock(&mdev->state_lock);

        mlx4_en_free_resources(priv);
+
+       if (priv->sysctl)
+               sysctl_ctx_free(&priv->conf_ctx);
+
        mtx_destroy(&priv->stats_lock.m);
        mtx_destroy(&priv->vlan_lock.m);
        kfree(priv);--uNG4LiJEvBLt5Xf8cNAOunN2O02VJbT6WCktmtc1b291laWA
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Index: sys/ofed/drivers/net/mlx4/en_netdev.c
===================================================================
--- sys/ofed/drivers/net/mlx4/en_netdev.c       (revision 254594)
+++ sys/ofed/drivers/net/mlx4/en_netdev.c       (working copy)
@@ -924,9 +924,6 @@ void mlx4_en_destroy_netdev(struct net_device *dev
        if (priv->allocated)
                mlx4_free_hwq_res(mdev->dev, &priv->res, MLX4_EN_PAGE_SIZE);
How-To-Repeat: reload mlxen then try sysctl -a or a certain problematic leaf.