linux-kernel - Re: [PATCH] scripts/jobserver-exec: parse the last --jobserver-auth= option

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Message-ID: <Y3KutB2fPCXX2Amn@fjasle.eu>
Date:   Mon, 14 Nov 2022 22:10:12 +0100
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/jobserver-exec: parse the last --jobserver-auth=
 option

On Tue, Nov 15, 2022 at 03:10:55AM +0900, Masahiro Yamada wrote:
> In the GNU Make manual, the section "Sharing Job Slots with GNU make"
> says:
> 
>     Be aware that the MAKEFLAGS variable may contain multiple instances
>     of the --jobserver-auth= option. Only the last instance is relevant.
> 
> Take the last element of the array, not the first.
> 
> Link: https://www.gnu.org/software/make/manual/html_node/Job-Slots.html
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  scripts/jobserver-exec | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/jobserver-exec b/scripts/jobserver-exec
> index 8762887a970c..4192855f5b8b 100755
> --- a/scripts/jobserver-exec
> +++ b/scripts/jobserver-exec
> @@ -23,7 +23,9 @@ try:
>  	opts = [x for x in flags.split(" ") if x.startswith("--jobserver")]
>  
>  	# Parse out R,W file descriptor numbers and set them nonblocking.
> -	fds = opts[0].split("=", 1)[1]
> +	# If the MAKEFLAGS variable contains multiple instances of the
> +	# --jobserver-auth= option, the last one is relevant.
> +	fds = opts[-1].split("=", 1)[1]
>  	reader, writer = [int(x) for x in fds.split(",", 1)]
>  	# Open a private copy of reader to avoid setting nonblocking
>  	# on an unexpecting process with the same reader fd.
> -- 
> 2.34.1

I think it feels a bit odd to check for '--jobserver' (w/o '-auth'), but
"fixing" it would require depending on make >= 4.2 (May 2016).  That's probably
not yet old enough, isn't it?

Reviewed-by: Nicolas Schier <nicolas@...sle.eu>


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