Re: [Bug #14270] Cannot boot on a PIII Celeron

Michael Tokarev
2009-10-04T12:15:26Z

Michael Tokarev wrote:
> Cyrill Gorcunov wrote:
>> On 10/2/09, Michael Tokarev <mjt@tls.msk.ru> wrote:
>>> Michael Tokarev wrote:
>>>> Cyrill Gorcunov wrote:
>>>>> On 10/1/09, Rafael J. Wysocki <rjw@sisk.pl> wrote:
>>>>>> This message has been generated automatically as a part of a report
>>>>>> of regressions introduced between 2.6.30 and 2.6.31.
>>>>>>
>>>>>> The following bug entry is on the current list of known regressions
>>>>>> introduced between 2.6.30 and 2.6.31. Please verify if it still
>>>>>> should
>>>>>> be listed and let me know (either way).
>>>>> Michael has been asked to bisect it (if possible). I cant reproduce it
>>>>> in kvm unfortunately.
>>>> Yes, and that's what I'll be trying to do shortly.
>>>> I had other issues to sort out and wasn't able to
>>>> get to it in few last days.
>>>>
>>>> Also I've a few other suspects. For example, in this .31
>>>> config I changed from bzip to lzma compression - and that's
>>>> where (or near) kernel is rebooting.
>>> And that was the problem. After switching from LZMA
>>> to BZIP2 kernel boots again.
>>>
>>> Dunno if it can be treated as a regression, but it's
>>> definitely a bug.
>>
>> thanks for tracking it down Michael!
>> Rafael, who is responsible for LZMA now?
>> Cc him please.
>
> Please hold on for a while.
>
> I switched to BZIP2, it booted fine. I switched back to LZMA -
> and that one now boots too. Original bzImage, which were built
> by the same compiler from the same source using the same
> options reboots.
>
> So um... I'm now trying to reproduce it ;)

I performed about 20 kernel recompiles, and finally have some "statistics".
The problem is almost reproduceable, in a sense that I was able to get 6
more cases behaving the same way (rebooting right at early boot on a cel).
And all 3 "non-working" cases were with ccache. Ie, about half out of ~25
compiles done with ccache, and 7 of the resulting kernels are buggy. No
single failure without ccache so far.

Maybe it's some stale .o file cached by ccache (and it indeed looks like
that) -- I didn't try to remove the cache yet (but my guess is that I
wont be able to reproduce the issue with clean cache anymore).

What puzzles me most is the "failure mode". The difference between the
two processors is minimal. Having a corrupt .o file and almost-working
kernel is almost impossible by its own. And hitting this difference with
a corrupt .o file is.. unbelievable.

So I'm declaring it's a false alarm for now, and closing the bug.

/mjt