Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
MIME-Version: 1.0
References: <20220426155229.436681-1-mailhol.vincent@wanadoo.fr>
 <20220507131146.834810-1-mailhol.vincent@wanadoo.fr> <20220507131146.834810-3-mailhol.vincent@wanadoo.fr>
In-Reply-To: <20220507131146.834810-3-mailhol.vincent@wanadoo.fr>
From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Sat, 14 May 2022 04:01:18 +0900
Message-ID: <CAK7LNATuvQhiZZ8A9+RcLYKmbugi6S61Aw5CStc3xbfGM-L34Q@mail.gmail.com>
Subject: Re: [RFC PATCH v2 2/2] kbuild: call check-atomics.sh only if
 prerequisites change
To:     Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc:     Michal Marek <michal.lkml@markovi.net>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Rikard Falkeborn <rikard.falkeborn@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Sat, May 7, 2022 at 10:13 PM Vincent Mailhol
<mailhol.vincent@wanadoo.fr> wrote:
>
> check-atomics.sh is executed unconditionally. Most developers will not
> modify the files being checked by this script and thus do not need to
> execute it again for each iterative make.
>
> We first add an additional dependency to include/linux/atomic/* to
> make sure that the script gets executed again if the headers are
> modified. We then use the if_change macro instead of cmd. c.f. [1] and
> create the dot file scripts/atomic/.check-atomics which is used for
> the target timestamp. Finally, the dot file is added to the
> CLEAN_FILES target.
>
> [1] https://www.kernel.org/doc/html/latest/kbuild/makefiles.html#command-change-detection
>
> Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>


I do not like this approach.

I wrote a different patch.
https://lore.kernel.org/lkml/20220513185340.239753-1-masahiroy@kernel.org/T/#u

This naturally works by comparing the timestamp
between *_shipped and include/generated/*.


> ---
>  Kbuild   | 7 ++++---
>  Makefile | 3 ++-
>  2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/Kbuild b/Kbuild
> index fa441b98c9f6..c3cb76ebcbaf 100644
> --- a/Kbuild
> +++ b/Kbuild
> @@ -50,10 +50,11 @@ missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
>  #####
>  # Check atomic headers are up-to-date
>
> -always-y += old-atomics
> +always-y += scripts/atomic/.check-atomics
>
>  quiet_cmd_atomics = CALL    $<
>        cmd_atomics = $(CONFIG_SHELL) $<
>
> -old-atomics: scripts/atomic/check-atomics.sh FORCE
> -       $(call cmd,atomics)
> +scripts/atomic/.check-atomics: scripts/atomic/check-atomics.sh $(wildcard include/linux/atomic/*) FORCE
> +       $(call if_changed,atomics)
> +       @touch $@
> diff --git a/Makefile b/Makefile
> index 9a820c525b86..9e815c8bb0b6 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1483,7 +1483,8 @@ endif # CONFIG_MODULES
>  # Directories & files removed with 'make clean'
>  CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \
>                modules.builtin modules.builtin.modinfo modules.nsdeps \
> -              compile_commands.json .thinlto-cache
> +              compile_commands.json .thinlto-cache \
> +              scripts/atomic/.check-atomics
>
>  # Directories & files removed with 'make mrproper'
>  MRPROPER_FILES += include/config include/generated          \
> --
> 2.35.1
>


-- 
Best Regards
Masahiro Yamada