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

[Michael Tokarev]

Michael Tokarev wrote:
> Cyrill Gorcunov wrote:
> > On 10/2/09, Michael Tokarev <mjt@xxxxxxxxxx> wrote:
> > > Michael Tokarev wrote:
> > > > Cyrill Gorcunov wrote:
> > > > > On 10/1/09, Rafael J. Wysocki <rjw@xxxxxxx> 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
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