Re: [Patch v3 03/12] net: mana: Handle vport sharing between devices

[David Miller]

From: longli@xxxxxxxxxxxxxxxxx
Date: Sun, 12 Jun 2022 14:14:45 -0700

> +int mana_cfg_vport(struct mana_port_context *apc, u32 protection_dom_id,
> +		   u32 doorbell_pg_id)
>  {
> +	/* Ethernet driver and IB driver can't take the port at the same time */
> +	refcount_inc(&apc->port_use_count);
> +	if (refcount_read(&apc->port_use_count) > 2) {

This is a racy test, the count could change after the test against
'2'.  It would be nice if there was a primitive to do the increment
and test atomically, but I fail to see one that matches this scenerio
currently.

Thank you.