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Mon, 27 Apr 2026 05:56:39 -0700 (PDT) Received: from [192.168.2.110] ([69.159.169.238]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8b02aa4f1f9sm256378186d6.0.2026.04.27.05.56.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Apr 2026 05:56:38 -0700 (PDT) Message-ID: <67d7b067-97a8-4600-a9a6-46f3e797ffed@redhat.com> Date: Mon, 27 Apr 2026 08:56:27 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 43/53] selftests/mm: migration: add setup of HugeTLB pages 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: <20260418105539.1261536-1-rppt@kernel.org> <20260418105539.1261536-44-rppt@kernel.org> Content-Language: en-US, en-CA From: Luiz Capitulino In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2026-04-26 06:58, Mike Rapoport wrote: > On Fri, Apr 24, 2026 at 01:11:45PM -0400, Luiz Capitulino wrote: >> On 2026-04-18 06:55, Mike Rapoport wrote: >>> From: "Mike Rapoport (Microsoft)" >>> >>> migration skips HugeTLB tests if there are no free huge pages >>> prepared by a wrapper script. >>> >>> Add setup of HugeTLB pages to the test and make sure that the original >>> settings are restored on the test exit. >>> >>> Since kselftest_harness runs fixture setup and the tests in child >>> processes, use HUGETLB_SETUP_DEFAULT_PAGES() that defines a constructor >>> that runs in the main process and add verification that there are enough >>> free huge pages to the tests that use them. >>> >>> Signed-off-by: Mike Rapoport (Microsoft) >>> --- >>> tools/testing/selftests/mm/migration.c | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c >>> index ccf42002ce86..61fb00953f83 100644 >>> --- a/tools/testing/selftests/mm/migration.c >>> +++ b/tools/testing/selftests/mm/migration.c >>> @@ -23,6 +23,8 @@ >>> #define MAX_RETRIES 100 >>> #define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) >>> +HUGETLB_SETUP_DEFAULT_PAGES(1) >> >> Hey Mike, >> >> I've been reviewing and testing this series and got a reproducible issue >> with this test when running it on a x86 KVM guest with 88 vCPUs. >> >> The issue is that, when executing the full MM suite with >> sudo ./run_vmtests.sh -d -a, all 6 migration test pass but it doesn't exit. >> Instead, it gets stuck after this output: >> >> """ >> # # PASSED: 6 / 6 tests passed. >> # # Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0 >> """ >> >> Getting a backtrace from gdb I see: >> >> """ >> #0 0x00007efd2f2c247b in __lll_lock_wait_private () from /lib64/libc.so.6 >> #1 0x00007efd2f26fa88 in __run_exit_handlers () from /lib64/libc.so.6 >> #2 0x00007efd2f26fabe in exit () from /lib64/libc.so.6 >> #3 0x0000000000404f2e in hugepage_restore_settings_sighandler () >> #4 >> #5 0x00007efd2f32f416 in __unregister_atfork () from /lib64/libc.so.6 >> #6 0x00007efd2f26f338 in __cxa_finalize () from /lib64/libc.so.6 >> #7 0x00007efd2f4548c7 in __do_global_dtors_aux () from /lib64/libm.so.6 >> #8 0x00007ffd66ae0320 in ?? () >> #9 0x00007efd2f55b2d2 in _dl_call_fini (closure_map=0x7efd2f5500c0) at dl-call_fini.c:43 >> """ >> >> Could we be messing with libc internal state somehow? I also get systemd >> services hung when I try to reboot. > > I don't think we are messing with libc internal state, but we surely leave > zombies around. > All the tests that fork() terminate the children with kill() but they never > call wait*() to collect the exit status. Right! >> Some of the migration tests fork() and then kill() their children >> processes. Won't those all restore the hugetlb state concurrently >> from hugepage_restore_settings_atexit()? > > Yeah, I missed the kill()s :/ > >> Also, for shared_anon_htlb, don't we need to reserve a HugeTLB page per >> children? > > We only mmap() a single huge page in the parent, the children don't create > new mappings. You're right, I missed the fact that the children only read from the page. >> And there's another issue: when running the migration test individually, >> private_anon_htlb gets skipped. I guess it's because the previous test >> is restoring the HugeTLB state: > > It could be. > > I pushed the updated version that has the fixes for both zombie and > signal issues: > > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=mm-selftest/v3 > > Would be great if you can test it in your setup. This works! Both issues are fixed: the migration test completes w/o hanging and when I run it individually all tests run. One last question: should we munmap() the mappings in this test? Though I understand this goes beyond your series goal.