Re: [RFC] embedded struct device Re: [patch] IDE driver model update

Patrick Mochel
2002-10-08T21:52:45Z

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