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Thu, 30 Apr 2026 07:54:26 -0700 (PDT) X-Received: by 2002:a05:6214:5549:b0:89c:4b37:7106 with SMTP id 6a1803df08f44-8b4000f7fdbmr35628096d6.34.1777560866347; Thu, 30 Apr 2026 07:54:26 -0700 (PDT) Received: from [192.168.2.110] ([70.53.202.134]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8b3ff439c2csm19482476d6.23.2026.04.30.07.54.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Apr 2026 07:54:25 -0700 (PDT) Message-ID: <6f8de9a3-2adc-4d96-bc0e-5171bcbba60f@redhat.com> Date: Thu, 30 Apr 2026 10:54:14 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 04/54] selftests/mm: migration: properly cleanup fork()ed processes To: Mike Rapoport Cc: Andrew Morton , David Hildenbrand , Baolin Wang , Barry Song , Dev Jain , Donet Tom , Jason Gunthorpe , John Hubbard , "Liam R. Howlett" , Lance Yang , Leon Romanovsky , Lorenzo Stoakes , Mark Brown , Michal Hocko , Nico Pache , Peter Xu , Ryan Roberts , Sarthak Sharma , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org References: <20260428204240.1924129-1-rppt@kernel.org> <20260428204240.1924129-5-rppt@kernel.org> <6b12453b-2683-41cc-bb4c-602eda6bf9d8@redhat.com> From: Luiz Capitulino In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: FesRWRIX9gczpjzsip6LD-7wzj0CZVPR3RDHR8xO1jI_1777560867 X-Mimecast-Originator: redhat.com Content-Language: en-US, en-CA Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DBA6F2000E X-Stat-Signature: ysdpxbyd36161st4aegf67a8jotn495r X-Rspam-User: X-HE-Tag: 1777560869-526032 X-HE-Meta: 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 gOegcxC8 lGtpvJgpV/5TYmjwEDXIhEKZGtOkR3q6fIIXZ87gos+uv1upoF7LPqOMbaPheuOfE5GbBrt8o9uycWKnzzSfwrh5WV7wDZd0iGM8p8u2Gwk9D/41JyY9nK4o8Dqbv9RmasBheMAJRv5hYG5SHhy4O5s6Im2daD0HKtUpB5QYw6zc95YopSNISf4Zqq/Q5iILnqY2t15S6RET7GevwAEXiEAzX+VTeYNzsiVGBP4FPvmQwNgSHu9wqJYpJbA6yxOfLbotK9emMe+yMeTxULPH2VUBtn3AUPixJWpeHnr43iT2kMHrj+Mg5QsIVeL2iiFeAodgrxM1wiZKiLPlPgt9GlpSf1ND0rBigOl3WTGIZlZT3a3mPlwtOrUT2b+vudk/5/BnFP/+XwnecHbz5oISLLEGQvDpsgLKTZ7aO8EXEvGBZZ5y4PaLuFsPNYUyiX+091p3EaoLzlsMYBtDKNjhur5O2tdz2mG4A6GRg Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-04-30 10:40, Mike Rapoport wrote: > On Thu, Apr 30, 2026 at 09:37:43AM -0400, Luiz Capitulino wrote: >> On 2026-04-28 16:41, Mike Rapoport wrote: >>> From: "Mike Rapoport (Microsoft)" >>> >>> Several migration test use fork() to create worker processes. These >>> processes are later killed, but nothing collects their exit status and they >>> remain as zombies in the system. >>> >>> Add a helper function that kills the worker processes, waitpid()s for >>> them and verifies the exit status. >>> >>> Replace the loops that call kill() for each process with a call to that >>> helper. >>> >>> The addition of waitpid() calls also makes sure the migrating process never >>> exits before the processes accessing the memory, so it's possible to drop >>> the call to prctl(PR_SET_PDEATHSIG, SIGHUP). >>> >>> Reported-by: Luiz Capitulino >>> Signed-off-by: Mike Rapoport (Microsoft) >>> --- >>> tools/testing/selftests/mm/migration.c | 54 +++++++++++++------------- >>> 1 file changed, 27 insertions(+), 27 deletions(-) >>> >>> diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c >>> index 3630f2fb0800..76e380b74658 100644 >>> --- a/tools/testing/selftests/mm/migration.c >>> +++ b/tools/testing/selftests/mm/migration.c >>> @@ -67,6 +67,24 @@ FIXTURE_TEARDOWN(migration) >>> free(self->pids); >>> } >>> +static bool kill_children(FIXTURE_DATA(migration) * self) >>> +{ >>> + int i, status; >>> + pid_t pid; >>> + >>> + for (i = 0; i < self->nthreads; i++) { >>> + pid = self->pids[i]; >>> + if (kill(pid, SIGTERM)) >>> + return false; >>> + if (pid != waitpid(pid, &status, 0)) >>> + return false; >>> + if (!WIFSIGNALED(status) || WTERMSIG(status) != SIGTERM) >>> + return false; >>> + } >> >> Why do we stop at the first error? Wouldn't it be better to kill & >> collect all of them and then return false if at least one fails? > > Yep, makes sense. > >>> + >>> + return true; >>> +} >>> + >>> int migrate(uint64_t *ptr, int n1, int n2) >>> { >>> int ret, tmp; >>> @@ -160,20 +178,14 @@ TEST_F_TIMEOUT(migration, shared_anon, 2*RUNTIME) >>> memset(ptr, 0xde, TWOMEG); >>> for (i = 0; i < self->nthreads; i++) { >>> pid = fork(); >>> - if (!pid) { >>> - prctl(PR_SET_PDEATHSIG, SIGHUP); >>> - /* Parent may have died before prctl so check now. */ >>> - if (getppid() == 1) >>> - kill(getpid(), SIGHUP); >> >> This goes beyond this series, but I wonder if we should have this check >> in access_mem() in case the parent dies in migrate(). > > With added kill() + waitpid() this should not happen. I was thinking in the case of a crash, but looking at it again it seems to be impossible so it's fine.