linux-kernel - Re: [RFC] kobject: add kobject_init_ng, kobject_add_ng, and kobject_init_and

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Message-ID: <20071204110112.14488ece@gondolin.boeblingen.de.ibm.com>
Date:	Tue, 4 Dec 2007 11:01:12 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Greg KH <greg@...ah.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Kay Sievers <kay.sievers@...y.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jonathan Corbet <corbet@....net>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: [RFC] kobject: add kobject_init_ng, kobject_add_ng, and
 kobject_init_and_add functions

On Mon, 3 Dec 2007 11:06:26 -0800,
Greg KH <greg@...ah.com> wrote:

> On Mon, Dec 03, 2007 at 01:00:03PM +0100, Cornelia Huck wrote:
> > On Fri, 30 Nov 2007 22:29:39 -0500 (EST),
> > Alan Stern <stern@...land.harvard.edu> wrote:
> > 
> > > On Fri, 30 Nov 2007, Greg KH wrote:
> > > 
> > > > +/**
> > > > + * kobject_add_ng - the main kobject add function
> > > > + * @kobj: the kobject to add
> > > > + * @parent: pointer to the parent of the kobject.
> > > > + *
> > > > + * The kobject name is set and added to the kobject hierarchy in this
> > > > + * function.
> > > > + *
> > > > + * If @parent is set, then the parent of the @kobj will be set to it.
> > > > + * If @parent is NULL, then the parent of the @kobj will be set to the
> > > > + * kobject associted with the kset assigned to this kobject.  If no kset
> > > > + * is assigned to the kobject, then the kobject will be located in the
> > > > + * root of the sysfs tree.
> > > > + *
> > > > + * If this function returns an error, kobject_put() must be called to
> > > > + * properly clean up the memory associated with the object.
> > > > + *
> > > > + * If the function is successful, the only way to properly clean up the
> > > > + * memory is with a call to kobject_del().
> > > 
> > > In which case kobject_put() isn't needed?
> > 
> > kobject_del() should only undo what kobject_add() did. So kobject_put()
> > will still be needed to clean up the memory. Perhaps the wording should
> > be:
> > 
> > If the function is successful, the only way to properly clean up the
> > kobject is to call kobject_del() for removing the kobject from the
> > hierarchy and to subsequently call kobject_put() to clean up the memory.
> 
> But that's not what the code does today in the kobject_del() function.

Hm, if I'm not completely confused, kobject_del() just gives up the
extra reference obtained by kobject_add(). That leaves the initial
reference we got via kobject_init(_ng)(). If we want to clean up the
memory, we need to give up that reference as well.
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