linux-kernel - Re: [PATCH] drm/tests: reduce drm_mm

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Date:   Fri, 16 Dec 2022 16:12:36 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Maíra Canal <maira.canal@....br>,
        Daniel Latypov <dlatypov@...gle.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] drm/tests: reduce drm_mm_test stack usage

On Thu, Dec 15, 2022 at 05:34:49PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The check_reserve_boundaries function uses a lot of kernel stack,
> and it gets inlined by clang, which makes __drm_test_mm_reserve
> use even more of it, to the point of hitting the warning limit:
> 
> drivers/gpu/drm/tests/drm_mm_test.c:344:12: error: stack frame size (1048) exceeds limit (1024) in '__drm_test_mm_reserve' [-Werror,-Wframe-larger-than]
> 
> When building with gcc, this does not happen, but the structleak
> plugin can similarly increase the stack usage and needs to be
> disabled, as we do for all other kunit users.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  drivers/gpu/drm/tests/Makefile      | 2 ++
>  drivers/gpu/drm/tests/drm_mm_test.c | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tests/Makefile b/drivers/gpu/drm/tests/Makefile
> index b29ef1085cad..f896ef85c2f2 100644
> --- a/drivers/gpu/drm/tests/Makefile
> +++ b/drivers/gpu/drm/tests/Makefile
> @@ -12,3 +12,5 @@ obj-$(CONFIG_DRM_KUNIT_TEST) += \
>  	drm_mm_test.o \
>  	drm_plane_helper_test.o \
>  	drm_rect_test.o
> +
> +CFLAGS_drm_mm_test.o := $(DISABLE_STRUCTLEAK_PLUGIN)
> diff --git a/drivers/gpu/drm/tests/drm_mm_test.c b/drivers/gpu/drm/tests/drm_mm_test.c
> index 89f12d3b4a21..90a5becc99b8 100644
> --- a/drivers/gpu/drm/tests/drm_mm_test.c
> +++ b/drivers/gpu/drm/tests/drm_mm_test.c
> @@ -298,7 +298,7 @@ static bool expect_reserve_fail(struct kunit *test, struct drm_mm *mm, struct dr
>  	return false;
>  }
>  
> -static bool check_reserve_boundaries(struct kunit *test, struct drm_mm *mm,
> +static bool noinline_for_stack check_reserve_boundaries(struct kunit *test, struct drm_mm *mm,
>  				     unsigned int count,
>  				     u64 size)
>  {
> -- 
> 2.35.1
>