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

From: "Russell King (Oracle)" <[email-masked]>
Date: Tue, 21 Nov 2023 10:20:43 +0000

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

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