linux-kernel - Re: [PATCH] kbuild: mark "FORCE" target as secondary

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Message-ID: <CAK7LNASOtyqJMET7YuuFzTCkwg02p850PnqCC57-BZNJhyKT7Q@mail.gmail.com>
Date: Thu, 18 Jul 2024 00:18:13 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Arnd Bergmann <arnd@...db.de>, 
	linux-kbuild@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas@...sle.eu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kbuild: mark "FORCE" target as secondary

On Wed, Jul 17, 2024 at 9:43 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> Starting with make-4.4.1, Kbuild uses the special .NOTINTERMEDIATE
> target to mark all targets as not intermediate, which slightly changes
> the behavior compared to older versions of make.
>
> This causes a build regression with my change to the system call table
> scripts now in scripts/Makefile.asm-headers, forcing a rebuild of the
> generated files with every make invocation and effectively breaking
> incremental builds.
>
> I have narrowed down the change in behavior to the way that the
> 'FORCE' target is treated: If this is marked as not intermediate,
> the $(if_changed) macro always evaluates it as a missing prerequisite,
> but if it is marked as .SECONDARY, it works like before.
>
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> Cc: linux-kbuild@...r.kernel.org
> Fixes: 875ef1a57f32 ("kbuild: use .NOTINTERMEDIATE for future GNU Make versions")
> Fixes: fbb5c0606fa4 ("kbuild: add syscall table generation to scripts/Makefile.asm-headers")
> Closes: https://lore.kernel.org/lkml/91b10591-1554-4860-8843-01c6cfd7de13@app.fastmail.com/T/#m4c979c42d0c086f616e41b4ca76f2873902b8a25
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ----
> I'm still a bit confused by the way this works in detail, hopefully
> Masahiro Yamada can either confirm that this is a correct fix or provide
> a better one.


Of course, NACK.

Now I am surprised that this broken series was quickly merged
into the mainline.
I really dislike how you changed scripts/Makefile.asm-headers


I will send a correct fix.
Please do not break Kbuild even further.




> ---
>  scripts/Kbuild.include | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index faf37bafa3f8..aa1ffaeb8fc0 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -267,6 +267,7 @@ endif
>  # deleted files.
>  ifneq ($(and $(filter notintermediate, $(.FEATURES)),$(filter-out 4.4,$(MAKE_VERSION))),)
>  .NOTINTERMEDIATE:
> +.SECONDARY: FORCE
>  else
>  .SECONDARY:
>  endif
> --
> 2.39.2
>
>


-- 
Best Regards
Masahiro Yamada