Re: [PATCH] release_resource() check for NULL resource

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Mon, Oct 03, 2005 at 11:59:01AM +0200, Jesper Juhl wrote:
> On 10/3/05, Ben Dooks <ben-linux@fluff.org> wrote:
> > On Sun, Oct 02, 2005 at 10:39:22AM -0700, Randy.Dunlap wrote:
> > > On Sun, 2 Oct 2005 18:03:18 +0100 Ben Dooks wrote:
> > >
> > > > If release_resource() is passed a NULL resource
> > > > the kernel will OOPS.
> > >
> > > does this actually happen?  you are fixing a real oops?
> > > if so, what driver caused it?
> >
> > I was developing a couple of new drivers, and found
> > that this does not behave like kfree() which does check
> > for NULL paramemters. I belive it would be helpful if
> > functions like this followed the example of kfree().
> >
> I would agree that it makes sense for resource release functions to be
> written defensively and be able to cope with being passed a NULL
> resource, just like kfree(), vfree(), crypto_free_tfm() and others are
> already doing.
> Seems safer and allows us to get rid of checks for NULL before calling
> such functions thus making code simpler, more readable and in some
> cases smaller.

I'm not convinced - release_resource() isn't like kfree() - it's more
like device_unregister().

It makes sense for kfree() to ignore NULL pointers, but does it really
make sense for *_unregister() to do so too?  Surely you want to only
unregister things which you know have previously been registered?

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core