Date: Thu, 29 Nov 2007 17:28:33 +0100
From: Cornelia Huck <cornelia.huck@de.ibm.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg KH <greg@kroah.com>, <linux-kernel@vger.kernel.org>,
       Kay Sievers <kay.sievers@vrfy.org>, Jonathan Corbet <corbet@lwn.net>,
       Randy Dunlap <randy.dunlap@oracle.com>
Subject: Re: [RFC] New kobject/kset/ktype documentation and example code
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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?)
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