linux-kernel - Re: [PATCH v3 2/2] kbuild: Don't mess with the .cache.mk when root

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Date:   Tue, 13 Mar 2018 16:33:48 +0000
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        malat@...ian.org, dave.hansen@...el.com, yang.s@...baba-inc.com,
        linux@...ck-us.net, Matthias Kaehlcke <mka@...omium.org>,
        Cao jin <caoj.fnst@...fujitsu.com>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Charlebois <charlebm@...il.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        a.p.zijlstra@...llo.nl, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 2/2] kbuild: Don't mess with the .cache.mk when root

On Mon, Mar 12, 2018 at 11:23 PM Doug Anderson <dianders@...omium.org>
wrote:

> Hi,

> On Mon, Mar 12, 2018 at 11:16 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Douglas Anderson <dianders@...omium.org> wrote:
> >
> >> +# Don't create Makefile caches if running as root since they can't be
deleted
> >> +# easily; in the real world we might be root when doing "sudo make
install"
> >> +ifeq ($(shell id -u),0)
> >> +export KBUILD_NOCACHE := 1
> >> +endif
> >
> > Please don't do this - many prominent kernel developers build their
kernels as
> > root - this makes the build slower for them, and also bifurcates
testing.

> Ah, interesting.  I hadn't realized that!

> I'm OK with dropping this patch myself.  It was mostly addressing a
> potential problem pointed out by Masahiro Yamada when we were talking
> about .cache.mk, but I don't think anyone has actually experienced the
> problems listed in the CL description.

>    /bin/sh: ./.cache.mk: Permission denied

I feel like I've definitely seen that permission error before.

Is there any issue if I:

$ make clean
$ make
$ sudo make install
<hack around>
$ make

Or it's only a problem if:

$ make clean
$ sudo make install
<hack around>
$ make
--
Thanks,
~Nick Desaulniers