linux-kernel - Re: on static kobjects and double frees...

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Message-ID: <20080610164241.GA13928@kroah.com>
Date:	Tue, 10 Jun 2008 09:42:41 -0700
From:	Greg KH <greg@...ah.com>
To:	Arthur Jones <ajones@...erbed.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Doug Thompson <norsk5@...oo.com>,
	"bluesmoke-devel@...ts.sourceforge.net" 
	<bluesmoke-devel@...ts.sourceforge.net>
Subject: Re: on static kobjects and double frees...

On Tue, Jun 10, 2008 at 09:38:00AM -0700, Arthur Jones wrote:
> Hi Greg, ...
> 
> On Tue, Jun 10, 2008 at 09:23:41AM -0700, Greg KH wrote:
> > On Tue, Jun 10, 2008 at 08:58:50AM -0700, Arthur Jones wrote:
> > > Hi Greg,  The edac pci sysfs generic layer uses a static
> > > kobject as a placeholder parent where edac pci drivers
> > > are inserted.
> > 
> > Hm, stop right there.
> > 
> > kobjects are not supposed to be static, bad things happen if you do that
> > (including the kernel itself will warn you about them, unless you gave
> > it an empty release function, and if so, then see
> > Documentation/kobject.txt and prepare to be mocked...)
> 
> OK, I wondered about this, but I didn't see anything
> in Documentation/kobject.txt that said that kobjects
> can not be static.  But now that I've fixed the double
> free bug, I'm seeing the warning you mentioned above...

Hm, there is the following text in that file:
	Because kobjects are dynamic, they must not be declared
	statically or on the stack, but instead, always allocated
	dynamically.  Future versions of the kernel will contain a
	run-time check for kobjects that are created statically and will
	warn the developer of this improper usage.

> I don't know how the current code came to be, so I
> can't speak to your issues below.  But, with these
> pointers, I think I can get things cleaned up properly.

Great, if you want me to review it, I'd be glad to do so.

thanks,

greg k-h
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