Re: Fw: Re: 2.6.21-rc4-mm1 + 4 hotfixes -- BUG: unable to handle kernel paging request at virtual address 6b6b6ceb -- EIP is at module_put+0x7/0x1f

Greg KH
2007-03-28T04:51:32Z

On Tue, Mar 27, 2007 at 09:27:19PM -0700, Andrew Morton wrote:
> On Tue, 27 Mar 2007 21:19:58 -0700 Greg KH <greg@kroah.com> wrote:
>
> > On Wed, Mar 28, 2007 at 11:52:33AM +0800, Shaohua Li wrote:
> > > +static void cpuidle_state_sysfs_release(struct kobject *kobj)
> > > +{
> > > + /* Nothing required to do here, just workaround kobject warning*/
> > > +}
> >
> > NO!!!
>
> heh. This happens rather a lot.
>
> > Do people think that I add warnings to the kernel so that people can
> > just work around them by passing empty functions to the driver core?
> >
> > Sometimes I wonder why I even try...
> >
> > Please fix this code, it is wrong.
> >
>
> Is it documented anywhere? I always forget the reasoning so I have to
> cc you each time I see it happening.

The fact that the kernel itself spits out a message saying:
"Device '%s' does not have a release() function, it is broken
and must be fixed."

isn't enough? What should I change it to, something like this:

"Device '%s' does not have a release() function, it is broken
and must be fixed, and if you just provide an empty function to
remove this warning, rabid echidnas will track you down and
puncture your spleen."

The reason for this is that the device is a reference counted object,
and you have to free the memory in the release function, otherwise you
can easily be accessing memory that is freed already.

Now note, this patch used a completion function to wait for the object
to be destroyed, which isn't the nicest. But if you are going to do
this, do it in the release function, like the code did a bit earlier.

And if you are doing this because you have two kobjects in the same
structure, well, your code is so messed up beyond belief that it needs
to be fixed. And yes scsi developers, I'm pointing at you...

So, where do I need to put this information so that people stop trying
to be smarter than the kernel...

ugh.

greg k-h