Re: [PATCH] m68k: Fix backtraces for non-running tasks

[Geert Uytterhoeven]

Hi Karl,

On Thu, 23 Jul 2026 at 06:12, Karl Mehltretter <kmehltretter@xxxxxxxxx> wrote:
> When no stack pointer is supplied, show_stack() starts at thread.esp0.
> This is the saved userspace register frame, not where a task was switched
> out. For kernel threads it points to the zeroed frame created by
> copy_thread(), so sched_show_task() prints no useful backtrace.
>
> Use thread.ksp for non-current tasks. It is saved by switch_to() and is
> already used by __get_wchan(). For current, start at the current stack
> frame, as is already done when no task is supplied.
>
> Tested on qemu-system-m68k -M virt using SysRq-t. All task dumps contained
> resolved frames.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Karl Mehltretter <kmehltretter@xxxxxxxxx>

Thanks, LGTM, and does make all SysRq-t dumps look sensible, so
Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
i.e. will queue in the m68k tree for v7.3.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds