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 <20220714235137.GA485839@roeck-us.net>
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From:   Daniel Latypov <dlatypov@google.com>
Date:   Thu, 14 Jul 2022 17:03:07 -0700
Message-ID: <CAGS_qxrhy3=pST9f85fvxubKQShOq1XF6ZHALzMhXDOf5gnaUg@mail.gmail.com>
Subject: Re: [PATCH v5 4/9] drm: selftest: convert drm_format selftest to KUnit
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     =?UTF-8?B?TWHDrXJhIENhbmFs?= <maira.canal@usp.br>,
        Isabella Basso <isabbasso@riseup.net>, magalilemes00@gmail.com,
        tales.aparecida@gmail.com, mwen@igalia.com, andrealmeid@riseup.net,
        siqueirajordao@riseup.net, Trevor Woerner <twoerner@gmail.com>,
        leandro.ribeiro@collabora.com, n@nfraprado.net,
        Daniel Vetter <daniel@ffwll.ch>,
        Shuah Khan <skhan@linuxfoundation.org>,
        David Airlie <airlied@linux.ie>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        michal.winiarski@intel.com,
        Javier Martinez Canillas <javierm@redhat.com>,
        =?UTF-8?B?Sm9zw6kgRXhww7NzaXRv?= <jose.exposito89@gmail.com>,
        David Gow <davidgow@google.com>, brendanhiggins@google.com,
        kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
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On Thu, Jul 14, 2022 at 4:51 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, Jul 08, 2022 at 05:30:47PM -0300, Ma=C3=ADra Canal wrote:
> > Considering the current adoption of the KUnit framework, convert the
> > DRM format selftest to the KUnit API.
> >
> > Tested-by: David Gow <davidgow@google.com>
> > Acked-by: Daniel Latypov <dlatypov@google.com>
> > Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
> > Signed-off-by: Ma=C3=ADra Canal <maira.canal@usp.br>
>
> This patch results in:
>
> Building powerpc:allmodconfig ... failed
> --------------
> Error log:
> drivers/gpu/drm/tests/drm_format_test.c: In function 'igt_check_drm_forma=
t_min_pitch':
> drivers/gpu/drm/tests/drm_format_test.c:271:1: error: the frame size of 3=
712 bytes is larger than 2048 bytes
>
> presumably due to function nesting.

This can happen when there's a lot of KUNIT_EXPECT_* calls in a single func=
tion.
See [1] for some related context.
There were a number of patches that went into 5.18 ([2] and others) to
try and mitigate this, but it's not always enough.

Ideally the compiler would see that the stack-local variables used in
these macros don't need to stick around, but it doesn't always
happen...
One workaround would be to split up the test case functions into smaller ch=
unks.

[1] https://lore.kernel.org/linux-kselftest/20210929212713.1213476-1-brenda=
nhiggins@google.com/
[2] https://lore.kernel.org/linux-kselftest/20220113165931.451305-1-dlatypo=
v@google.com/

Daniel