Re: [PATCH] printk: Make CONSOLE_LOGLEVEL_QUIET configurable

Petr Mladek
2018-06-25T14:56:58Z

On Wed 2018-06-20 15:37:47, Hans de Goede wrote:
> Hi,
>
> On 20-06-18 13:03, Petr Mladek wrote:
> > On Tue 2018-06-19 13:57:26, Hans de Goede wrote:
> > > The goal of passing the "quiet" option to the kernel is for the kernel
> > > to be quiet unless something really is wrong.
> > >
> > > Sofar passing quiet has been (mostly) equivalent to passing
> > > loglevel=4 on the kernel commandline. Which means to show any messages
> > > with a level of KERN_ERR or higher severity on the console.
> > >
> > > In practice this often does not result in a quiet boot though, since
> > > there are many false-positive or otherwise harmless error messages printed,
> > > defeating the purpose of the quiet option. Esp. the ACPICA code is really
> > > bad wrt this, but there are plenty of others too.
> >
> > I see your pain. But this sounds like a workaround for a broken code.
> > This change might just encourage people to create even more mess.
>
> I've been submitting patches upstream to fix false-positive KERN_ERR
> messages for more then a year now and getting a KERN_ERR free kernel
> (on more then 1 specific model hw) is just undoable. Every release some
> new nonsense error comes up, like e.g.:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1568276
>
> Besides this random KERN_ERR cases (of which there are plenty
> by themselves) I've also had long discussions with the ACPICA upstream
> maintainers, but they refuse 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.

Thanks for the many examples. It would help me to argue if anyone
later complains about this change ;-)

> > > This commit makes CONSOLE_LOGLEVEL_QUIET configurable.
> > >
> > > This for example will allow distros which want quiet to really mean quiet
> > > to set CONSOLE_LOGLEVEL_QUIET so that only messages with a higher severity
> > > then KERN_ERR (CRIT, ALERT, EMERG) get printed, avoiding an endless game
> > > of whack-a-mole silencing harmless error messages.
> >
> > I find it a bit confusing that "quiet" would mean something different
> > on different systems.
>
> The kernel is so configurable already that I don't think this really is much
> of an issue, quiet will still mean quiet on all systems, some might just
> be a tad more quiet (or actually be quiet) compared to others.

Just for record. Some people actually do a lot to prevent adding new
configure options. The many possibilities cause troubles to users
and even experienced developers.

A common argument against adding new options is: "How users could be
able to choose reasonable value when even experts (maintainers,
developers) are not able to agree on it".

> I went with making this configurable because I expect that to
> be a controversial change.

Exactly, I thought about changing the default. But it might just
bring a lot of bike-shedding.

I do not see any other good option. More people like this patch.
So I pushed it into printk.git, branch for-4.19.

Best Regards,
Petr