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Re: GRUB really slow to boot

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On 18/12/2021 16:08, Greg Wooledge wrote:
> Today I rebooted my machine for the first time in quite a while, after
> the kernel update that was released along with Debian 11.2.
>
> When it reached the GRUB screen, I pressed Enter, and nothing happened
> as far as I could see.  I was initially worried that it had stopped
> seeing my USB keyboard (a thing that I've experienced with GRUB and
> certain USB slots on certain machines in the past).  This keyboard
> plugged into this same USB slot had worked in previous versions of GRUB
> on this machine, though.
>
> The next thing I observed was that after 5 seconds, it still hadn't
> booted, nor had the coundown ("will automatically boot in 5s" or whatever)
> advanced.  It appeared to be hung.
>
> I waited a bit longer, and the 5s changed to 4s.  It just took a really
> long time (like 15+ seconds for each second on the timer).
>
> Eventually, after a minute or two, the system booted.  Everything is
> working normally now, post-GRUB.
>
> Has anyone experienced this, or does anyone have ideas about how to
> prevent it happening again?  I am not interested in trial and error
> for this, because it's far too annoying and disruptive.  But if there
> are well-known ideas about things I could try (e.g. "grub 2.04 is known
> to have bugs on Intel motherboards, revert to 2.03") then I'm game.

Not a definitive answer here, but to me, this sounds like the sort of 
behaviour a program would have when having to process lots of 
interrupts. You say that pressing Enter does nothing and that the 
countdown happens really slowly. Imagine you had a stuck key - something 
which was repeatedly sending keypresses to GRUB, but which weren't 
triggering the "cancel timer" branch. Something like CTRL or Shift, 
maybe. Or an ACPI key etc.

I see that you say you're not interested in trial-and-error and I can 
understand that. If you can, try using a different keyboard. Or just 
unplug the keyboard entirely (You may need to configure your BIOS to 
allow booting without the keyboard or just allow the BIOS enough time to 
see the keyboard and THEN unplug it before GRUB sees it).

https://sources.debian.org/src/grub2/2.04-20/grub-core/normal/menu.c/#L601 
seems to be the loop of code that GRUB executes while waiting for a key. 
I can see some functions there that, if not written carefully, COULD 
take some time to return.

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GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-18 17:10 +0100
  Re: GRUB really slow to boot James Dutton <james.dutton@gmail.com> - 2021-12-18 23:30 +0100
    Re: GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-18 23:40 +0100
      Re: GRUB really slow to boot James Dutton <james.dutton@gmail.com> - 2021-12-19 00:50 +0100
        Re: GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-19 01:00 +0100
          Re: GRUB really slow to boot James Dutton <james.dutton@gmail.com> - 2021-12-19 14:00 +0100
            Re: GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-19 15:20 +0100
          Re: GRUB really slow to boot Curt <curty@free.fr> - 2021-12-19 15:20 +0100
            Re: GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-19 15:30 +0100
              Re: GRUB really slow to boot James Dutton <james.dutton@gmail.com> - 2021-12-19 15:40 +0100
      Re: GRUB really slow to boot Felix Miata <mrmazda@earthlink.net> - 2021-12-19 04:10 +0100
  Re: GRUB really slow to boot Dan Ritter <dsr@randomstring.org> - 2021-12-19 00:10 +0100
    Re: GRUB really slow to boot Tim Woodall <debianuser@woodall.me.uk> - 2021-12-19 08:30 +0100
      Re: GRUB really slow to boot Greg Wooledge <greg@wooledge.org> - 2021-12-19 15:30 +0100
        Re: GRUB really slow to boot Tim Woodall <debianuser@woodall.me.uk> - 2021-12-19 16:10 +0100
  Re: GRUB really slow to boot Brian <ad44@cityscape.co.uk> - 2021-12-19 13:10 +0100
  Re: GRUB really slow to boot Darac Marjal <mailinglist@darac.org.uk> - 2021-12-19 15:50 +0100
  Re: GRUB really slow to boot David Wright <deblis@lionunicorn.co.uk> - 2022-01-03 03:50 +0100
    Re: GRUB really slow to boot David Wright <deblis@lionunicorn.co.uk> - 2022-01-20 17:30 +0100

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