Bug#652119: Bad pagetable 000f

[Jonathan Nieder <jrnieder@gmail.com>]

Matthew Wakeling wrote:

> Thanks. I tried GhostBSD, which didn't have par2 included and
> couldn't run executables from my hard drive, and Knoppix which was
> an i386 kernel (albeit very recent 3.0.something), so also couldn't
> run my amd64 par2 from my hard drive. A rescue environment may be
> the way forward, but how do I get a recent kernel and par2 onto it?
> I have to admit I am not well-versed in setting that up.

To test a recent kernel, there should be no need for a rescue
environment.  Just installing initramfs-tools, linux-base, and a
kernel image from sid should work fine.  (Everything else can stay at
the version from squeeze.)

Does GhostBSD include a C compiler?  If so, it should be possible to
build par2 from source to use there.

> I think I have spotted another condition for the bug to be
> triggered. I ran par2 with a different configuration, and it worked.
> I think par2 does interleaved word by word access to n memory areas,
> where n is configurable. When it crashed, n was 1400, and when it
> worked n was 140. I also noticed the program worked much faster when
> n was smaller. Now, the number of TLB entries on my processor is
> 1024, so it is quite possible that every single word access causes a
> TLB miss.

Thanks for these updates.  I suppose I should also mention

 - http://linux-mm.org/, the memory management subsystem wiki
 - linux-mm@kvack.org, the mailing list

since they are more likely to be able to say what makes sense and what
doesn't in explaining your symptoms, even when working with an old
kernel.

Please cc either me or this bug log if writing to them so we can track
it.

Thanks for your patience and sorry for the lack of progress.
Jonathan