From: Li Wang <liwang@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com,
vbabka@kernel.org, rppt@kernel.org, surenb@google.com,
mhocko@suse.com, shuah@kernel.org, linux-mm@kvack.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] selftests/mm: serialize local_config generation for parallel builds
Date: Tue, 31 Mar 2026 17:16:23 +0800 [thread overview]
Message-ID: <acuQ51e_qd6yfa46@redhat.com> (raw)
In-Reply-To: <20260330222948.c2cc6544492e68ded355abca@linux-foundation.org>
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@redhat.com> 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@linux-foundation.org>
>
> 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
next prev parent reply other threads:[~2026-03-31 9:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-31 4:01 [PATCH 1/4] selftests/mm: respect build verbosity settings for 32/64-bit targets Li Wang
2026-03-31 4:01 ` [PATCH 2/4] selftests/mm: serialize local_config generation for parallel builds Li Wang
2026-03-31 5:29 ` Andrew Morton
2026-03-31 9:16 ` Li Wang [this message]
2026-03-31 4:01 ` [PATCH 3/4] selftests/lib.mk: set PWD from CURDIR to avoid wrong extmod path Li Wang
2026-03-31 5:30 ` Andrew Morton
2026-03-31 7:19 ` Li Wang
2026-03-31 4:01 ` [PATCH 4/4] selftests/mm: fix cow/gup_longterm link failures when liburing flags are missing Li Wang
2026-03-31 7:13 ` Li Wang
2026-04-01 13:44 ` David Hildenbrand (Arm)
2026-03-31 5:29 ` [PATCH 1/4] selftests/mm: respect build verbosity settings for 32/64-bit targets Andrew Morton
2026-03-31 9:50 ` Li Wang
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