Re: [RFC PATCH v2] gdb: Add drgn-why-sleeping command

[Kevin Buettner <kevinb@redhat.com>]

On Thu, 1 Oct 2026 11:01:19 +0200
Alexandra Petlanova Hajkova <ahajkova@redhat.com> wrote:

> > Summary: this is a useful idea, and v2 fixes the concrete v1
> > problems.  Before v3, I'd like to see the "does this belong in
> > GDB" question settled with the maintainers.  On the code side, I'd
> > most like to see M1 (PID namespace), M2 (partial debuginfo), M3
> > (unhandled drgn exceptions) and the drgn.internal / sys.executable
> > dependency (M4) fixed.
> 
> thank you very much for the insightful review. I'd love to get more
> feedback
> on  "does this belong in GDB" question.

[earlier reples trimmed somewhat]

I've given it some more thought.  I don't think we should introduce a
drgn-why-sleeping facility into GDB as a "first class citizen", i.e.
something which is part of GDB that gets regular testing.

The requirements / dependencies are onerous:

1. You must have drgn installed; this part is the easiest since it's
   just a 'pip install'.
2. kernel debuginfo - this is pretty big.  When I had it tested on
   Fedora 44, it was a 1.3 GiB download and it takes 5.5 GiB on disk.
   Moreover, the debuginfo must match the currently running kernel.
   New debuginfo would need to be updated every time that the kernel
   is updated.
3. Read access to /proc/kcore is required. Drgn's sudo helper passes
   the descriptor back to GDB so that GDB itself stays unprivileged,
   but the descriptor conveys read access to the whole of kernel
   memory - the same access root would have. Care should, therefore,
   be taken on production systems where kernel-memory secrets must
   not be disclosed.
4. Secure Boot plus lockdown=confidentiality prevents it from working.
   (My AI tells me that Secure Boot enabled with lockdown set to
   'integrity' will work, but this is not something I've tested.)

If we had some sort of user-facing contrib directory, it could be
placed there.  Alternately, as the AI reviewer suggested, it could
go into a contrib directory in the drgn package.

Kevin