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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 12 Aug 2021 13:32:59 +0200
Message-ID: <CAMuHMdUjn8H8651XVOjBrBFqQs1bKR8kZbSPJWRhr071xk_kaw@mail.gmail.com>
Subject: Re: [PATCH net-next v3 01/16] mctp: Add MCTP base
To:     Jeremy Kerr <jk@codeconstruct.com.au>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        netdev <netdev@vger.kernel.org>,
        linux-kbuild <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Matt Johnston <matt@codeconstruct.com.au>,
        Andrew Jeffery <andrew@aj.id.au>
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Hi Jeremy,

On Thu, Aug 12, 2021 at 1:15 PM Jeremy Kerr <jk@codeconstruct.com.au> wrote:
> > When building an allmodconfig kernel, I got:
>
> [...]
>
> I don't see this on a clean allmodconfig build, nor when building the
> previous commit then the MCTP commit with something like:
>
>   git checkout bc49d81^
>   make O=obj.allmodconfig allmodconfig
>   make O=obj.allmodconfig -j16
>   git checkout bc49d81
>   make O=obj.allmodconfig -j16
>
> - but it seems like it might be up to the ordering of a parallel build.
>
> From your description, it does sound like it's not regenerating flask.h;
> the kbuild rules would seem to have a classmap.h -> flask.h dependency:
>
>   $(addprefix $(obj)/,$(selinux-y)): $(obj)/flask.h
>
>   quiet_cmd_flask = GEN     $(obj)/flask.h $(obj)/av_permissions.h
>         cmd_flask = scripts/selinux/genheaders/genheaders $(obj)/flask.h $(obj)/av_permissions.h
>
>   targets += flask.h av_permissions.h
>   $(obj)/flask.h: $(src)/include/classmap.h FORCE
>         $(call if_changed,flask)
>
> however, classmap.h is #include-ed as part of the genheaders binary
> build, rather than read at runtime; maybe $(obj)/flask.h should depend
> on the genheaders binary, rather than $(src)/include/classmap.h ?
>
> If you can reproduce, can you compare the ctimes with:
>
>   stat scripts/selinux/genheaders/genheaders security/selinux/flask.h
>
> in your object dir?

Unfortunately I can't seem to reproduce this anymore.
Goodbye, Heisenbug!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds