Hey Nathan,
On 17.12.2024 10:46, Nathan Chancellor wrote:
Hi Sebastian,
On Tue, Nov 19, 2024 at 12:02:26PM +0100, Sebastian Fricke wrote:
Hey Nathan,
On 18.11.2024 13:06, Nathan Chancellor wrote:
> On Fri, Oct 18, 2024 at 03:14:42PM +0000, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > With KASAN enabled, clang fails to optimize the inline version of
> > vdec_vp9_slice_map_counts_eob_coef() properly, leading to kilobytes
> > of temporary values spilled to the stack:
> >
> > drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c:1526:12: error: stack frame size (2160) exceeds limit (2048) in 'vdec_vp9_slice_update_prob' [-Werror,-Wframe-larger-than]
> >
> > This seems to affect all versions of clang including the latest (clang-20),
> > but the degree of stack overhead is different per release.
> >
> > Marking the function as noinline_for_stack is harmless here and avoids
> > the problem completely.
> >
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>
> Unfortunately, I have seen no moment on my upstream report and this
> warning is breaking allmodconfig builds because of -Werror. Can this be
> applied as a workaround for now (preferrably with a Cc: stable on it)?
>
> Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
I'll handle it asap, it will be part of 6.13
Is there any update here? I don't see this patch applied in -next.
I have sent out the PR and it has been applied to the -fixes branch in
the media tree, due to the holiday period there might be some delays but
I expect the change to soon land in Linux-next.
Cheers,
Nathan
Regards,
Sebastian
> > ---
> > I have not come to a conclusion on how exactly clang fails to do this
> > right, but can provide the .config and/or preprocessed source files
> > and command line if we think this should be fixed in clang.
> > ---
> > .../mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
> > index eea709d93820..47c302745c1d 100644
> > --- a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
> > +++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
> > @@ -1188,7 +1188,8 @@ static int vdec_vp9_slice_setup_lat(struct vdec_vp9_slice_instance *instance,
> > return ret;
> > }
> >
> > -static
> > +/* clang stack usage explodes if this is inlined */
> > +static noinline_for_stack
> > void vdec_vp9_slice_map_counts_eob_coef(unsigned int i, unsigned int j, unsigned int k,
> > struct vdec_vp9_slice_frame_counts *counts,
> > struct v4l2_vp9_frame_symbol_counts *counts_helper)
> > --
> > 2.39.5
> >
>
Sebastian Fricke
Consultant Software Engineer
Collabora Ltd
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales no 5513718.
