Changing the kernel loglevel associated with "quiet" from 4 to 3.

[Hans de Goede]

Hi All,

As some of you have probably heard I'm working on making Fedora
be less "chatty" during boot, part of this is:

https://fedoraproject.org/wiki/Changes/HiddenGrubMenu

But that only makes grub quiet.

We've been passing to the kernel for a long time for the
same reasons. Unfortunately quiet is not really always
quiet.

There are simply many false-positive or at least
completely harmless messages printed by the kernel
with a loglevel of KERN_ERR. Currently we display all
these. For at least the last year or so I've been sending
patches to the upstream kernel to silence these, but
new ones always pop up. So this is an endless and
hopeless game of whack-a-mole.

Therefor I propose to instead of keep whacking the moles,
we change the loglevel associated with "quiet" from 4 to 3,
so that only messages with a higher severity then KERN_ERR
(CRIT, ALERT, EMERG) get printed on the console.

Note all messages will still be available in dmesg and the
journal. This is purely about which messages get printed
on the console and thus get thrown in the users face.

Besides improving the boot experience by not needlessly
showing scary messages to end users, this should also
help to reduce the amount of bugs we receive about
these kind of errors. Here is a quick and in no way
complete list of bugs which I believe fall into this
category:

   1413342 - Linux 4.9.3: ACPI Error: [_OSI] Namespace lookup failure, AE_NOT_FOU
   1415853 - ACPI Error: Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-
   1514937 - ACPI Error: AE_NOT_FOUND
   1527870 - ACPI Error: [\_SB_.PCI0.SAT1] Namespace lookup failure, AE_NOT_FOUND
   1552580 - ACPI Error: Method parse/execution failed
   1553320 - Kernel errors at bootup -- system runs okay
   1556967 - ACPI Error: [SMIC] Namespace lookup failure, AE_ALREADY_EXISTS
   1582825 - ACPI Error: Method parse/execution failed
   https://bugzilla.kernel.org/show_bug.cgi?id=109511
   https://bugzilla.kernel.org/show_bug.cgi?id=194687

Esp. the bugzilla.kernel.org ones are interesting and
then esp.:

https://bugzilla.kernel.org/show_bug.cgi?id=109511
109511 - ACPI error messages caused by undefined object - Dell XPS 13 9350

Which is about a completely harmless ACPI DSDT problem which
many machines have, resulting in an AE_NOT_FOUND error. I've
done multiple attempts to get the upstream ACPICA people to
drop the loglevel of AE_NOT_FOUND errors to KERN_WARNING, also
see the 194687 bug. But upstream ACPICA refuses to change this
instead insisting that:

a) Vendors should fix there DSDTs to be perfect; and
b) end-users should then update their BIOS to fix this

Neither of which is a realistic expectation in anyway,
this just goes to show that getting the kernel to not
log harmless errors is a loosing proposition.

###

TL;DR: kernel is still too verbose at loglevel 4, lets
change quiet to mean 3. To achieve this without needing
downstream patches I've posted a patch upstream to make
this configurable from Kconfig:

https://lkml.org/lkml/2018/6/19/462

My question to the Fedora kernel team now is, are you
ok with changing the log-level associated with "quiet"
from 4 to 3?

I can take care of making the necessary changes.

Regards,

Hans