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

[Doug Anderson]

Hi,

On Tue, Mar 13, 2018 at 9:33 AM, Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
> On Mon, Mar 12, 2018 at 11:23 PM Doug Anderson <dianders@xxxxxxxxxxxx>
> wrote:
>
>> Hi,
>
>> On Mon, Mar 12, 2018 at 11:16 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>> >
>> > * Douglas Anderson <dianders@xxxxxxxxxxxx> 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.

Hopefully the error message was obvious enough that it didn't take you
too long to think to type "sudo make clean"?  I know it's better for
people not to have to figure this out, but my hope is at least it's
not too arcane of an errror message.


> Is there any issue if I:
>
> $ make clean
> $ make
> $ sudo make install
> <hack around>
> $ make

I don't personally know of any problems with the above flow.


> Or it's only a problem if:
>
> $ make clean
> $ sudo make install
> <hack around>
> $ make

Yeah, just that one.

NOTE: as Masahiro noted in response to the cover letter [1], he's come
up with a better solution to the problem that was solved by the
.cache.mk and he's planning to remove it shortly.


[1] https://lkml.org/lkml/2018/3/13/100