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

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Message-ID: <Pine.LNX.4.44L0.0712041023400.4321-100000@iolanthe.rowland.org>
Date:	Tue, 4 Dec 2007 10:28:24 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
cc:	Greg KH <greg@...ah.com>, 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 Tue, 4 Dec 2007, Cornelia Huck wrote:

> > > > > + * 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.

That's right.  Furthermore there are other parts of the kernel that 
expect to do the kobject_del() and the final kobject_put() separately.  
For example, the driver core does kobject_del() as part of device_del() 
and then it does the final kobject_put() as part of put_device().

Alan Stern

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