Re: 2.6.30-rc6: Reported regressions from 2.6.29

Greg KH
2009-05-17T15:34:07Z

On Sat, May 16, 2009 at 07:13:59PM -0700, Linus Torvalds wrote:
>
>
> On Sun, 17 May 2009, Kay Sievers wrote:
> >
> > This makes the oops in the driver-core, caused by the rtc driver
> > unregister, go away. The original issue is also fixed in the rtc driver
> > itself.
>
> I don't think this is sufficient.
>
> > --- a/drivers/base/driver.c
> > +++ b/drivers/base/driver.c
> > @@ -257,6 +257,8 @@ EXPORT_SYMBOL_GPL(driver_register);
> > */
> > void driver_unregister(struct device_driver *drv)
> > {
> > + if (!drv || !drv->p)
> > + return;
> > driver_remove_groups(drv, drv->groups);
> > bus_remove_driver(drv);
> > }
>
> Ok, fine so far, but look at "driver_register()".
>
> It will set drv->p, but then not unset it if it fails! (For a certain
> class of failures)
>
> So for a certain failure pattern, drv->p will point to some stale value.
> Should we not clear drv->p in the "out_unregister" patch?
>
> To confuse the thing more, there are actually "half-way failures" that
> _succeed_ in driver registration, but then return an error code. See that
> whole
>
>
> kobject_uevent(&priv->kobj, KOBJ_ADD);
> return error;
>
> case in the "success" path driver_register(). We may return an error
> despite the fact that we actually attached the driver to bus, but
> "add_bind_files()" failed. A caller would be understandable very unhappy.
>
> So I suspect we should do something like the appended (in addition to your
> patch). Comments?

That looks good. I'll add the WARN_ON that Ingo pointed out, and merge
this with Kay's patch. Give me a few hours to wake up...

thanks,

greg k-h