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b=HE/NV2dha6cd2OtUwR78Q437KzC1h6ofgAfUZm9jM9WofymJUN2njFrAFLeB1kXPn gef3tSe4IhSNi7rCJF4iHKGa4at3yroDe4DpECVgZJDDJPgKp9cUNSZxtMJ/k5pc0w 2bp/9qroFHA0km+6DDkzHuGC+KMaEz8W9ADsVlOI= Date: Mon, 30 Mar 2026 22:29:48 -0700 From: Andrew Morton To: Li Wang 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 Message-Id: <20260330222948.c2cc6544492e68ded355abca@linux-foundation.org> In-Reply-To: <20260331040156.119158-2-liwang@redhat.com> References: <20260331040156.119158-1-liwang@redhat.com> <20260331040156.119158-2-liwang@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 4zudqxim8s78fzoe8eke7tqi6k9gfe83 X-Rspamd-Queue-Id: 4C6A91C0005 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1774934990-901013 X-HE-Meta: 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 wo1+PQ/9 etg0A Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 31 Mar 2026 12:01:54 +0800 Li Wang 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 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.