Re: [PATCH v3] printk: fix zero-valued printk timestamps in early boot

Geert Uytterhoeven
2026-03-31T08:17:25Z

Hi TIm,

On Mon, 30 Mar 2026 at 22:42, Bird, Tim <Tim.Bird@sony.com> wrote:
> > From: Thomas Gleixner <tglx@kernel.org>
> > > There are other approaches, but none really work early enough in the
> > > kernel boot to not be a pain. The goal is to provide timing info
> > > before: timekeeping init, jiffies startup, and even CPU features
> > > determination,
> >
> > As I pointed out before that's wishful thinking:
> >
> > You _cannot_ access a resource before it has been determined to be
> > available.
> >
> > Period.
> >
> > It does not matter at all if _you_ know for sure that it is the case in
> > _your_ personal setup.
>
> I used get_cycles(), which has a check for availability in it, so the patch didn't
> access a resource before it was determined to be available.

Note that such a check is only available in the MIPS and x86 versions.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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