Bug 14270

On Sunday 04 October 2009, Michael Tokarev wrote:
> 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.

References : http://marc.info/?l=linux-kernel&m=125509847805427&w=4