Re: [PATCH v2 net-next 10/10] net: dsa: mv88e6xxx: MST Offloading

[Vladimir Oltean]

On Thu, Mar 10, 2022 at 05:25:47PM +0200, Vladimir Oltean wrote:
> > >> +	err = mv88e6xxx_sid_get(chip, attr->orig_dev, vattr->msti, &new_sid);
> > >> +	if (err)
> > >> +		goto unlock;
> > >> +
> > >> +	if (vlan.sid) {
> > >> +		err = mv88e6xxx_sid_put(chip, vlan.sid);
> > >> +		if (err)
> > >> +			goto unlock;
> > >> +	}
> > >> +
> > >> +	vlan.sid = new_sid;
> > >> +	err = mv88e6xxx_vtu_loadpurge(chip, &vlan);
> > >
> > > Maybe you could move mv88e6xxx_sid_put() after this succeeds?
> > 
> > Yep. Also made sure to avoid needless updates of the VTU entry if it
> > already belonged to the correct SID.
> 
> I realize I gave you conflicting advice here, first with inverting the
> refcount_inc() with the refcount_dec(), then with having fast handling
> of noop-changes to vlan.sid. I hope you're able to make some sense out
> of that and avoid the obvious issue with the refcount temporarily
> dropping to zero before going back to 1, which makes the sanity checker
> complain.

Oh wow... I didn't look at the code again, and commented based on a
false memory. Disregard, sorry. You aren't reversing sid_get with sid_put,
nor did I suggest that. There's a lot that happened just in my head,
apparently.