On Tue, 29 Jul 2008 14:57:58 +0100
Alistair John Strachan <alistair@devzero.co.uk> wrote:

quoted text
> 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.

quoted text
> The full dmesg and kernel config are available from
> http://devzero.co.uk/~alistair/2.6.27-rc1-mc-oops/
...
quoted text
> 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.

Thanks.

-- 
Pekka Paalanen
http://www.iki.fi/pq/
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