linux-kernel - Re: [PATCH v2 1/2] padata: Mark padata_work_init() as _

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Message-ID: <20221207195623.mk4jt5vkc76s77cf@parnassus.localdomain>
Date:   Wed, 7 Dec 2022 14:56:23 -0500
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Nicolas Schier <nicolas@...sle.eu>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Vincent Donnefort <vdonnefort@...gle.com>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev,
        Steffen Klassert <steffen.klassert@...unet.com>,
        linux-crypto@...r.kernel.org
Subject: Re: [PATCH v2 1/2] padata: Mark padata_work_init() as __ref

On Wed, Dec 07, 2022 at 12:16:56PM -0700, Nathan Chancellor wrote:
> When building arm64 allmodconfig + ThinLTO with clang and a proposed
> modpost update to account for -ffuncton-sections, the following warning
> appears:
> 
>   WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)
>   WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text)
> 
> LLVM has optimized padata_work_init() to include the address of
> padata_mt_helper() directly, which causes modpost to complain since
> padata_work_init() is not __init, whereas padata_mt_helper() is. In
> reality, padata_work_init() is only called with padata_mt_helper() as
> the work_fn argument in code that is __init, so this warning will not
> result in any problems. Silence it with __ref, which makes it clear to
> modpost that padata_work_init() can only use padata_mt_helper() in
> __init code.

Thanks!

Acked-by: Daniel Jordan <daniel.m.jordan@...cle.com>

> Suggested-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> Cc: Steffen Klassert <steffen.klassert@...unet.com>
> Cc: Daniel Jordan <daniel.m.jordan@...cle.com>
> Cc: linux-crypto@...r.kernel.org
> ---
>  kernel/padata.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/padata.c b/kernel/padata.c
> index e5819bb8bd1d..4c3137fe8449 100644
> --- a/kernel/padata.c
> +++ b/kernel/padata.c
> @@ -83,8 +83,8 @@ static struct padata_work *padata_work_alloc(void)
>  	return pw;
>  }
>  
> -static void padata_work_init(struct padata_work *pw, work_func_t work_fn,
> -			     void *data, int flags)
> +static __ref void padata_work_init(struct padata_work *pw, work_func_t work_fn,
> +				   void *data, int flags)
>  {
>  	if (flags & PADATA_WORK_ONSTACK)
>  		INIT_WORK_ONSTACK(&pw->pw_work, work_fn);
> 
> base-commit: 76dcd734eca23168cb008912c0f69ff408905235
> -- 
> 2.38.1
>