Greg KH writes:
> On Sat, Mar 08, 2008 at 04:56:39PM +0100, Mikael Pettersson wrote:
> > In kernels up to and including 2.6.24, it was possible to
> > register-then-unregister a sysdev_class/sys_device pair
> > multiple times. Starting with the 2.6.24-git1 kernel, doing
> > so causes a warning
> >
> > kobject (f88e96c8): tried to init an initialized object, something is seriously wrong
>
> This is a warning only, I have a patch queued up to fix this. I've
> included it below.
>
> > the second time the class/device pair is registered, followed
> > soon thereafter by random BUG()s and a kernel panic.
>
> That's odd. I don't think that is related, but it might be. Can you
> try the patch and let me know if it still happens?
The patch silenced the warning, but I still got a BUG() in
cache_alloc_refill() shortly after loading the test module.
(The machine needs some activity before the BUG() happens,
a few sync;dmesg;ps commands suffice for me.)
If I change the test module to do the sysdev_register stuff
once in module_init and the unregister stuff once in module_exit,
as opposed to once per "session" using the device, then things
work fine and I can't crash the kernel even if I repeatedly
insmod and rmmod the module. This indicates that some other part
of the sysdev object's state, apart from the state_initialized
flag, must also be cleaned up in the unregister() path.
I'll continue investigating this tomorrow.
/Mikael
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