Re: [RFC] New kobject/kset/ktype documentation and example code

Cornelia Huck
2007-11-29T16:28:54Z

On Thu, 29 Nov 2007 10:47:19 -0500 (EST),
Alan Stern <stern@rowland.harvard.edu> wrote:

> On Thu, 29 Nov 2007, Cornelia Huck wrote:
>
> > > The only problem arises when a child's driver retains a reference to
> > > the parent kobject. If things are done properly, this reference should
> > > involve incrementing the module count -- which would prevent the module
> > > from being unloaded in the first place.
> >
> > This still leaves the possibility that random code may grab a reference
> > once the kobject is present in the tree and lookupable. You gave up the
> > control of the number of references to your object once you made it
> > public.
>
> I don't agree with this argument. Code should never grab random
> references without insuring that the owner of the referenced object is
> pinned. This rule applies to everything, not just kobjects.

Of course. You don't necessarily need prevent module unloading, but pin
the module in memory until the last reference is gone.

> Unfortunately kobjects don't have an owner field. In practice this
> means that it isn't possible to pin the owner of some random kobject --
> you have to know where the kobject came from or what it's embedded in.
> All users of kobjects need to work this way.

Yeah, that is what the-patchset-I-have-to-dig-around-for does:
Introduce an owner field in the kobject for pinning the module. (IIRC,
you even did some of the patches?)