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    SubjectRe: Oops in microcode sysfs registration,
    On Tue, 29 Jul 2008 14:57:58 +0100
    Alistair John Strachan <> wrote:

    > Noticing pq's mmiotrace was merged I tried to get a trace of the proprietary
    > NVIDIA blob. Normally I wouldn't waste your time posting a tainted oops,
    > however in this case it doesn't look related to the proprietary garbage and I
    > think there's a real bug somewhere.
    > As I understand it, the mmiotrace tracing framework requires only one logical
    > CPU to be active, automatically offlining the other CPUs. When mmiotrace is
    > disabled, it automatically re-enables the CPUs it offlined. If I offline the
    > spare CPUs myself, prior to enabling mmiotrace, I do not see the issue I'm
    > about to describe. That's why tracing people have been CCed, even though that
    > could be a red herring.

    I have a wild hunch...
    Could you try the following:
    1. with all cpus enabled, load the nvidia proprietary driver
    2. start and quit X
    3. disable a cpu by hand
    4. unload the proprietary driver
    5. enable the cpu by hand

    I have a vague recollection of the nvidia blob doing something bad
    with notifiers, so if that crashes, and it does not crash when you
    leave step 4 out, it's an nvidia problem. I assume you unloaded the
    blob before disabling mmiotrace, right?

    You may need to alter the sequence of things, but my guess is that
    the blob may leave a notifier registered even when it is unloaded,
    so it crashes when the notifier chain is traversed. I'm not sure the
    backtrace really supports this scenario, but worth to try.

    > The full dmesg and kernel config are available from
    > Also, I'm sure this is reproducible without the NVIDIA garbage, but I was too lazy
    > to test it. If you want me to repeat the experiment without the driver I would be
    > more than happy to do so.

    I'm not sure people are willing to look into this without a clean report,
    so this would be cool. There's even a test module for mmiotrace in the
    kernel, but I doubt it would make difference to use it or not, when trying
    to reproduce the crash without the blob.


    Pekka Paalanen

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