Fujitsu lifebook A544, after bios update, kacpid using processor

[Colin Law]

On Sun, 26 Jul 2020 at 14:42, Colin Law <clanlaw at gmail.com> wrote:
>
> I booted into Windows on my Fujitsu Lifebook A544 and was notified
> that there was an important BIOS upgrade which would make it less
> likely that my battery would self ignite, so I upgraded it to the
> latest (1.25).  Now, however, in Ubuntu, the system monitor shows that
> something is permanently using about 60% of one of the cores, but the
> process list shows nothing using anything like that amount of
> processor.
> Using htop and hitting K, which I think then shows kernel threads, it
> appears to show that the culprits are kworkers kacpid, kacpi_notify.
> Googling suggests that others with similar problems have solved it by
> various means including installing acpi (no difference) and adding
> kernel parameter noapic (which made it worse).  Has anyone any other
> ideas which might help?

Found it, it seems to be the re-appearance in a slightly different
guise of an issue that first appeared with BIOS version 1.15, but then
went away with version 1.20.  I don't really understand what causes
it.  It is documented in
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/887793.  The fix
(or perhaps it is a workaround) is to run
sudo sh -c 'echo "disable" > /sys/firmware/acpi/interrupts/gpe13'
which works until a reboot, or to make it persistent add to the root
crontab (using sudo crontab -e)
@reboot echo "disable" > /sys/firmware/acpi/interrupts/gpe13

Whether that has any side effects I don't know, but it doesn't seem to
be causing a problem.  If anyone actually understands what this is all
about I would be interested to learn.

Thanks all for the help.

Colin


>
> Colin