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Tue, 31 Mar 2026 02:16:26 -0700 (PDT) Received: from redhat.com ([209.132.188.88]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35dbe6fcea1sm998457a91.16.2026.03.31.02.16.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 02:16:25 -0700 (PDT) Date: Tue, 31 Mar 2026 17:16:23 +0800 From: Li Wang To: Andrew Morton 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: References: <20260331040156.119158-1-liwang@redhat.com> <20260331040156.119158-2-liwang@redhat.com> <20260330222948.c2cc6544492e68ded355abca@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 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. 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