[Buildroot] [PATCH v8 RESEND 0/8] Add support for top-level parallel make

[Arnout Vandecappelle <arnout@mind.be>]

On 12/11/13 09:39, Fabio Porcedda wrote:
> On Mon, Nov 11, 2013 at 2:49 PM, Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com> wrote:
>> Fabio, Arnout,
>>
>> On Fri, 18 Oct 2013 11:34:12 +0200, Fabio Porcedda wrote:
>>
>>> this is a patch set for adding support for top-level parallel make in
>>> buildroot, the common problem scattered in buildroot's top-level
>>> makefiles is that in the rules it relies on the order of evaluation of
>>> the prerequisites, to be able to use top-level parallel make instead
>>> of reling on the left to right ordering of evaluation of the
>>> prerequisites we must add an explicit rule to describe the
>>> dependencies.
>>
>> I'd like to agree on a plan with this patch series. At the latest
>> Buildroot Developer Day in Edinburgh, I think we agreed that:
>>
>>   (1) Enabling top-level parallel without having per-package sysroot was
>>       not desirable, as it would make the builds non-reproducible.
>
> What do you think if we provide an easy way to use top-level parallel make
> that warns about the problems:
>
> ifeq ($(P),1)
> $(warning Not reproducible builds use at your own risk!)

  Such a warning will not really be visible, because it appears at the 
very beginning of the build and is immediately followed by all of the 
build output...

> BR2_JLEVEL=
> else
> # This top-level Makefile can *not* be executed in parallel
> .NOTPARALLEL:
> endif

  Since you only need to make this simple change in the Makefile (remove 
.NOTPARALLEL), I think it's a lot more effective for people who want 
top-level parallel builds to remove this line in their copy of buildroot. 
We also agreed at the BR developer meeting that we would add an 
explanatory comment at that location to make it clear why we disable 
parallel builds. That way, someone who wants to enable it will be aware 
of the risks.


  Regards,
  Arnout


>
>
>    make P=1 -j5
[snip]


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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