linux-kernel - Re: [PATCH] kobject: make sure kobj->ktype is set before kobject

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Date:	Thu, 29 Nov 2007 10:54:26 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Kay Sievers <kay.sievers@...y.org>
cc:	Cornelia Huck <cornelia.huck@...ibm.com>, Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jonathan Corbet <corbet@....net>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: [PATCH] kobject: make sure kobj->ktype is set before kobject_init

On Thu, 29 Nov 2007, Kay Sievers wrote:

> > And if someone calls kobject_put() after kobject_init() to clean up,
> > their release function will not be called if they didn't set the ktype.
> > So the check really belongs into kobject_init() IMO.

Right.  And even though cleaning up no longer needs to drop a reference
to the kset, it still might need to free the kobject's name.  So for 
example, either of these sequences:

	kobject_init();			kobject_set_name();
	kobject_set_name();		kobject_init();
	...				...
	kobject_free();			kobject_free();

would leak memory.

In fact, if we were designing the kobject API from scratch, I'd suggest 
making the ktype value an argument to kobject_init() so that it 
_couldn't_ be omitted.

> Hmm, will one expect that the whole object will also be free'd when we
> suggest to call kobject_put() to cleanup? That might be pretty
> unexpected, right?

I don't understand the question.  People _already_ expect the cleanup 
routine to free the kobject when the last reference is dropped.  Why 
should there be any confusion over this?

Alan Stern

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