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Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds
To:     Guenter Roeck <linux@roeck-us.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Arnd Bergmann <arnd@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com>
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From:   Nathan Chancellor <nathan@kernel.org>
Message-ID: <4063ef23-d769-167f-75b4-6a27cee5ecba@kernel.org>
Date:   Tue, 7 Sep 2021 12:12:19 -0700
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On 9/7/2021 10:48 AM, Guenter Roeck wrote:
> On 9/7/21 10:10 AM, Linus Torvalds wrote:
>> On Tue, Sep 7, 2021 at 2:11 AM Arnd Bergmann <arnd@kernel.org> wrote:
>>>
>>>> x86_64-alpine.log:drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:452:13: 
>>>> error: stack frame size (1800) exceeds limit (1280) in function 
>>>> 'dcn_bw_calc_rq_dlg_ttu' [-Werror,-Wframe-larger-than]
>>>> x86_64-alpine.log:drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn21/display_rq_dlg_calc_21.c:1657:6: 
>>>> error: stack frame size (1336) exceeds limit (1280) in function 
>>>> 'dml21_rq_dlg_get_dlg_reg' [-Werror,-Wframe-larger-than]
>>>> x86_64-alpine.log:drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn30/display_rq_dlg_calc_30.c:1831:6: 
>>>> error: stack frame size (1352) exceeds limit (1280) in function 
>>>> 'dml30_rq_dlg_get_dlg_reg' [-Werror,-Wframe-larger-than]
>>>> x86_64-alpine.log:drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_rq_dlg_calc_31.c:1676:6: 
>>>> error: stack frame size (1336) exceeds limit (1280) in function 
>>>> 'dml31_rq_dlg_get_dlg_reg' [-Werror,-Wframe-larger-than]
>>>> x86_64-alpine.log:drivers/vhost/scsi.c:1831:12: error: stack frame 
>>>> size (1320) exceeds limit (1280) in function 'vhost_scsi_release' 
>>>> [-Werror,-Wframe-larger-than]
>>>>
> 
> FWIW, the above is because of
> 
> static void vhost_scsi_flush(struct vhost_scsi *vs)
> {
>          struct vhost_scsi_inflight *old_inflight[VHOST_SCSI_MAX_VQ];
> 
> where VHOST_SCSI_MAX_VQ=128. Presumably some versions of clang inline
> this function. gcc has the same problem here - its stack frame size is
> also > 1024 for vhost_scsi_flush().

Good to know. When investigating these, I intend to compare against GCC 
to see what the difference is to know if it is a problem with the code 
or a compiler issue.

Cheers,
Nathan