[ofa-general] IB kernel modules and the kobject release() method

[Bart Van Assche]

On Thu, Aug 6, 2009 at 7:37 PM, Roland Dreier <rdreier at cisco.com> wrote:
>
>  >
>  > After having enabled CONFIG_DEBUG_KOBJECT=y in the kernel config I
>  > noticed that messages appeared in the kernel log about the IB modules
>  > missing a kobject release() method. This happens both with a vanilla
>  > 2.6.30.4 kernel and with a 2.6.27.29 kernel + OFED 1.4.1. Has anyone
>  > noticed this before ?
>  >
>  > An example of the messages logged in /var/log/messages:
>  >
>  > ...
>  > kobject: 'ib_cm' (ffffffffa067a810): does not have a release()
>  > function, it is broken and must be fixed.
>
> I don't see anything similar with CONFIG_DEBUG_KOBJECT enabled on
> 2.6.31-rc5 (without adding in any OFED confusion).
>
> It seems as if you get this message for every module being loaded; do
> you see it for any non-RDMA-related modules?  (Do you have any such
> modules in your config?)  I can imagine the OFED build system messing
> things up, but if you're just building the modules as part of the normal
> kernel build (ie your vanilla 2.6.30 kernel) then I don't see anything
> that would make ib_cm or iw_cm any different from any other module.
>
> For example, if I load ib_cm on my kernel, the only log messages I see
> from "dmesg|grep ib_cm" are:
>
>    kobject: 'ib_cm' (ffffffffa024c8f0): kobject_add_internal: parent: 'module', set: 'module'
>    kobject: 'holders' (ffff88022c1c9df8): kobject_add_internal: parent: 'ib_cm', set: '<NULL>'
>    kobject: 'ib_cm' (ffffffffa024c8f0): kobject_uevent_env
>    kobject: 'ib_cm' (ffffffffa024c8f0): fill_kobj_path: path = '/module/ib_cm'
>    kobject: 'notes' (ffff88022c1c9be8): kobject_add_internal: parent: 'ib_cm', set: '<NULL>'

Just to be sure that I'm working with the vanilla 2.6.30.4 kernel
drives and not with the OFED drivers, I ran the following commands
before any IB modules were loaded:

rm -rf /lib/modules/$(uname -r)
cd /usr/src/linux-2.6.30.4
make modules_install

Next I started (/etc/init.d/openibd start; /etc/init.d/opensmd start)
and then stopped (/etc/init.d/opensmd stop; /etc/init.d/openibd stop)
the IB subsystem. The "broken" message was logged during module unload
only, not during module load.

The "broken" message was also logged for the following non-IB kernel
modules: snd_seq_dummy, snd_pcm_oss, snd_mixer_oss, snd_seq,
snd_seq_device and scsi_tgt.

Bart.

Bart.