linux-kernel - Re: [PATCH v5 1/5] bug/kunit: Core support for suppressing warning backtraces

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Message-ID: <aD7fJxQWggfGekOf@phenom.ffwll.local>
Date: Tue, 3 Jun 2025 13:40:23 +0200
From: Simona Vetter <simona.vetter@...ll.ch>
To: Maxime Ripard <mripard@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Kees Cook <kees@...nel.org>,
	Alessandro Carminati <acarmina@...hat.com>,
	linux-kselftest@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Daniel Diaz <daniel.diaz@...aro.org>,
	David Gow <davidgow@...gle.com>,
	Arthur Grillo <arthurgrillo@...eup.net>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ville Syrjala <ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>, Guenter Roeck <linux@...ck-us.net>,
	Alessandro Carminati <alessandro.carminati@...il.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Linux Kernel Functional Testing <lkft@...aro.org>,
	dri-devel@...ts.freedesktop.org, kunit-dev@...glegroups.com,
	linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v5 1/5] bug/kunit: Core support for suppressing warning
 backtraces

On Mon, Jun 02, 2025 at 12:38:10PM +0200, Maxime Ripard wrote:
> On Mon, Jun 02, 2025 at 09:57:07AM +0200, Peter Zijlstra wrote:
> > On Sat, May 31, 2025 at 06:51:50AM -0700, Kees Cook wrote:
> > 
> > > It's not for you, then. :) I can't operate ftrace, but I use kunit
> > > almost daily. Ignoring WARNs makes this much nicer, and especially for
> > > CIs.
> > 
> > I'm thinking you are more than capable of ignoring WARNs too. This
> > leaves the CI thing.
> > 
> > So all this is really about telling CIs which WARNs are to be ignored,
> > and which are not? Surely the easiest way to achieve that is by
> > printing more/better identifying information instead of suppressing
> > things?
> 
> You might also want to test that the warn is indeed emitted, and it not
> being emitted result in a test failure.
> 
> And I can see a future where we would fail a test that would trigger an
> unexpected WARN.
> 
> Doing either, or none, would be pretty terrible UX for !CI users too.
> How on earth would you know if the hundreds of WARN you got from the
> tests output are legitimate or not, and if you introduced new ones
> you're supposed to fix?

Yeah we'd like to make sure that when drivers misuse subsystem api, things
blow up. Kunit that makes sure we hit the warn we put in place for that
seems like the best way to go about that, because in the past we've had
cases where we thought we should have caught abuse but didn't. And this
isn't the only thing we use, it's just one tool in the box among many
others to keep the flood of driver issues at a manageable level.

Cheers, Sima
-- 
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch