`test_tracemalloc_track_race` segfault on buildbot

Crash report

Seen on the ARM Raspbian 3.x buildbot, but I suspect it's not Raspbian specific:

https://buildbot.python.org/#/builders/424/builds/12446/steps/6/logs/stdio

0:02:36 load avg: 3.51 [177/497/1] test_tracemalloc worker non-zero exit code (Exit code -11 (SIGSEGV))
test_late_untrack (test.test_tracemalloc.TestCAPI.test_late_untrack) ... ok
test_stop_track (test.test_tracemalloc.TestCAPI.test_stop_track) ... ok
test_stop_untrack (test.test_tracemalloc.TestCAPI.test_stop_untrack) ... ok
test_tracemalloc_track_race (test.test_tracemalloc.TestCAPI.test_tracemalloc_track_race) ... Fatal Python error: Segmentation fault

Thread 0xf4afe400 [python] (most recent call first):

Thread 0xf52ff400 [python] (most recent call first):
  <freed thread state>

<freed thread state>

Current thread's C stack trace (most recent call first):
  <system returned no stack trace>

Extension modules: math.integer, _testcapi, _testinternalcapi (total: 3)

从 test.test_tracemalloc.TestCAPI.test_tracemalloc_track_race 开始，复现或检查 issue 中链接的 ARM Raspbian buildbot 日志。跟踪 SIGSEGV，并确认在受影响的 buildbot 配置上，测试完成时没有 worker 以非零退出码退出。