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Date: Tue, 8 Oct 2002 14:57:58 -0700 (PDT)
From: Patrick Mochel <mochel@osdl.org>
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To: Kai Germaschewski <kai-germaschewski@uiowa.edu>
cc: Alexander Viro <viro@math.psu.edu>,
       Linus Torvalds <torvalds@transmeta.com>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>, <andre@linux-ide.org>,
       <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] embedded struct device Re: [patch] IDE driver model update
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On Tue, 8 Oct 2002, Kai Germaschewski wrote:

> On Tue, 8 Oct 2002, Alexander Viro wrote:
> 
> > That would be nice, if it worked that way.  As it is we have
> > 
> > driver allocates foo
> > driver grabs a reference to foo->dev
> > ....
> > somebody else grabs/drops temporary references to foo->dev
> > ....
> > driver call put_device(&foo->dev)
> > driver frees structures refered from foo.
> > driver frees foo.
> > 
> > _IF_ the last two steps were done by ->release(), your arguments would
> > work.  Actually they are done by driver right after the put_device() call.
> > 
> > If you are willing to change that (== move all destruction into ->release()) -
> > yeah, then embedded struct device will work.  It's a hell of a work though.
> > 
> > Comments?
> 
> Just a short note, since I have gotta run: The latter won't work very well 
> with modules, since obviously ->release() has to MOD_DEC_USE_COUNT, to 
> avoid having ->release() unloaded before it's executed. So for one, that's 
> a DoS making delaying module unload indefinitely by keep /driversfs/... 
> open, but even worse, rmmod will refuse to unload the module, since the 
> use count is > zero. 
> 
> That's because normally pci_unregister_driver() or whatever is called in
> cleanup_module(), but obviously to be able to call it the refcount has to 
> be zero already...

That's true for drivers, but not for devices. Nonetheless, it's a big 
problem that I've hoped would magically go away. Of course it won't, but I 
don't have a solution for it off hand...

	-pat

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