Re: [RFC PATCH net-next v2 04/10] net: sfp: Add helper to return the SFP bus name

Hi Andrew, Russell,

On Tue, 21 Nov 2023 10:20:43 +0000
"Russell King (Oracle)" [off-list ref] wrote:

On Tue, Nov 21, 2023 at 02:00:58AM +0100, Andrew Lunn wrote:

quoted

quoted

+const char *sfp_get_name(struct sfp_bus *bus)
+{
+	if (bus->sfp_dev)
+		return dev_name(bus->sfp_dev);
+
+	return NULL;
+}  

Locking? Do you assume rtnl? Does this function need to take rtnl?  

Yes, rtnl needs to be held to safely access bus->sfp_dev, and that
either needs to happen in this function, or be documented as being
requried (and ASSERT_RTNL() added here.)

The reason is that sfp_dev is the SFP socket device which can be
unbound via sfp_unregister_socket(), which will set bus->sfp_dev to
NULL. This could race with the above.

That's right, I'll add an assert and document it, thanks for spotting
this.

Maxime