Re: [PATCH 2/4] selftests/mm: serialize local_config generation for parallel builds

[Andrew Morton]

On Tue, 31 Mar 2026 12:01:54 +0800 Li Wang <liwang@xxxxxxxxxx> wrote:

> The mm selftests generate both local_config.mk and local_config.h from
> check_config.sh. With high parallelism (-jN), this can race and lead to
> incomplete target builds (e.g. only a few binaries get built after
> 'make -j100', while 'make -j1' builds everything).
> 
> Switch to a stamp-based dependency:
> 
>   local_config.stamp: check_config.sh
>         ... run check_config.sh ...
>         touch local_config.stamp
> 
> and make local_config.mk/local_config.h depend on the stamp.
> 
> This ensures check_config.sh is executed once per update decision and
> removes the parallel race window. Also hook local_config.stamp into
> EXTRA_CLEAN.
> 
> No functional change intended for non-parallel builds.
> 
> Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

Well, the wind changed direction.  I saw this race a single time today
but now I'm trying to produce a reliable before-and-after report, it
isn't cooperating - everything is now building with -j100 with and
without this patch.

So not very helpful, sorry.