Re: [RFC PATCH 8/9] livepatch: allow patch modules to be removed

Josh Poimboeuf
2015-02-10T19:57:13Z

On Tue, Feb 10, 2015 at 08:02:34PM +0100, Jiri Slaby wrote:
> On 02/09/2015, 06:31 PM, Josh Poimboeuf wrote:
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> ...
> > @@ -497,10 +500,6 @@ static struct attribute *klp_patch_attrs[] = {
> >
> > static void klp_kobj_release_patch(struct kobject *kobj)
> > {
> > - /*
> > - * Once we have a consistency model we'll need to module_put() the
> > - * patch module here. See klp_register_patch() for more details.
> > - */
>
> I deliberately let you write the note in there :). What happens when I
> leave some attribute in /sys open and you remove the module in the meantime?

You're right, as was I the first time :-)

The only problem is that it would be nice if we could call
klp_unregister_patch() from the patch module's exit function, so that
doing an rmmod on the patch module unregisters it. But if we put
module_put() in the patch release function, then we have a circular
dependency and we could never rmmod it.

How about instead we do a klp_is_patch_registered() at the beginning of
all the attribute accessor functions? It's kind of ugly, but I can't
think of a better idea at the moment.

--
Josh