On Tue, Apr 21, 2026 at 1:51 PM Jani Nikula <[email protected]> wrote: > > On Tue, 21 Apr 2026, Albert Esteve <[email protected]> wrote: > > On Mon, Apr 20, 2026 at 4:47 PM Peter Zijlstra <[email protected]> wrote: > >> > >> On Mon, Apr 20, 2026 at 02:28:06PM +0200, Albert Esteve wrote: > >> > From: Guenter Roeck <[email protected]> > >> > > >> > The drm_test_rect_calc_hscale and drm_test_rect_calc_vscale unit tests > >> > intentionally trigger warning backtraces by providing bad parameters to > >> > the tested functions. What is tested is the return value, not the > >> > existence > >> > of a warning backtrace. Suppress the backtraces to avoid clogging the > >> > kernel log and distraction from real problems. > >> > > >> > Tested-by: Linux Kernel Functional Testing <[email protected]> > >> > Acked-by: Dan Carpenter <[email protected]> > >> > Acked-by: Maíra Canal <[email protected]> > >> > Cc: Maarten Lankhorst <[email protected]> > >> > Cc: David Airlie <[email protected]> > >> > Cc: Daniel Vetter <[email protected]> > >> > Signed-off-by: Guenter Roeck <[email protected]> > >> > Signed-off-by: Alessandro Carminati <[email protected]> > >> > Signed-off-by: Albert Esteve <[email protected]> > >> > --- > >> > drivers/gpu/drm/tests/drm_rect_test.c | 14 ++++++++++++++ > >> > 1 file changed, 14 insertions(+) > >> > > >> > diff --git a/drivers/gpu/drm/tests/drm_rect_test.c > >> > b/drivers/gpu/drm/tests/drm_rect_test.c > >> > index 17e1f34b76101..1dd7d819165e7 100644 > >> > --- a/drivers/gpu/drm/tests/drm_rect_test.c > >> > +++ b/drivers/gpu/drm/tests/drm_rect_test.c > >> > @@ -409,8 +409,15 @@ static void drm_test_rect_calc_hscale(struct kunit > >> > *test) > >> > const struct drm_rect_scale_case *params = test->param_value; > >> > int scaling_factor; > >> > > >> > + /* > >> > + * drm_rect_calc_hscale() generates a warning backtrace whenever > >> > bad > >> > + * parameters are passed to it. This affects all unit tests with an > >> > + * error code in expected_scaling_factor. > >> > + */ > >> > + KUNIT_START_SUPPRESSED_WARNING(test); > >> > scaling_factor = drm_rect_calc_hscale(¶ms->src, ¶ms->dst, > >> > params->min_range, > >> > params->max_range); > >> > + KUNIT_END_SUPPRESSED_WARNING(test); > >> > >> Would not something like: > >> > >> scoped_kunit_suppress() { > >> scaling_factor = drm_rect_calc_hscale(¶ms->src, > >> ¶ms->dst, > >> params->min_range, > >> params->max_range); > >> } > >> > >> be better? > > > > Since KUnit already has a few macros in its API it didn't occur to me. > > Good idea, I like it. And I guess the scope approach matches well with > > your __cleanup comment in the first patch. If no one opposes, I will > > work toward that pattern for the next version. > > There's a catch with kunit and __cleanup and thus (scoped) guards. Kunit > runs in ktreads, asserts lead to kthread_exit() and the __cleanup won't > be called.
Hi Jani, Good point. In this specific case, the actual cleanup is handled by kunit_add_action_or_reset(), so __cleanup not firing on assert is harmless. > > Warning suppression being part of kunit infrastructure, asserts can and > should end the suppression too. But setting the example (scoped) guards > are safe in kunit tests in general feels like a trap waiting to happen. > ... but I agree it sets a misleading precedent. I'll stick with the explicit start/end API, then? Or maybe we can clearly document why the scoped approach is safe in this case and use it. > > BR, > Jani. > > > > > >> > >> Also, how can you stand all this screaming in the code? > >> > > > > Again, KUnit already contains many macros, so this use didn't register > > as such. Now I will not be able to unsee it. > > > > > > -- > Jani Nikula, Intel >
