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

[Li Wang]

On Mon, Mar 30, 2026 at 10:29:48PM -0700, Andrew Morton wrote:
> 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.

No worries, we can hang this one as well.

Let me send to kbuild ML with the two valid fix (1/4, 4/4),
I will reformat them.

-- 
Regards,
Li Wang