bpo-40692: Run more test_concurrent_futures tests (GH-20239)

In the case of multiprocessing.synchronize() being missing, the
test_concurrent_futures test suite now skips only the tests that
require multiprocessing.synchronize().

Validate that multiprocessing.synchronize exists as part of
_check_system_limits(), allowing ProcessPoolExecutor to raise
NotImplementedError during __init__, rather than crashing with
ImportError during __init__ when creating a lock imported from
multiprocessing.synchronize.

Use _check_system_limits() to disable tests of
ProcessPoolExecutor on systems without multiprocessing.synchronize.

Running the test suite without multiprocessing.synchronize reveals
that Lib/compileall.py crashes when it uses a ProcessPoolExecutor.
Therefore, change Lib/compileall.py to call _check_system_limits()
before creating the ProcessPoolExecutor.

Note that both Lib/compileall.py and Lib/test/test_compileall.py
were attempting to sanity-check ProcessPoolExecutor by expecting
ImportError. In multiprocessing.resource_tracker, sem_unlink() is also absent
on platforms where POSIX semaphores aren't available. Avoid using
sem_unlink() if it, too, does not exist.

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
This commit is contained in:
Asheesh Laroia 2021-02-07 19:15:51 -08:00 committed by GitHub
parent 30a8b28396
commit bf2e7e55d7
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6 changed files with 49 additions and 10 deletions

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@ -37,8 +37,16 @@ if os.name == 'posix':
import _multiprocessing
import _posixshmem
# Use sem_unlink() to clean up named semaphores.
#
# sem_unlink() may be missing if the Python build process detected the
# absence of POSIX named semaphores. In that case, no named semaphores were
# ever opened, so no cleanup would be necessary.
if hasattr(_multiprocessing, 'sem_unlink'):
_CLEANUP_FUNCS.update({
'semaphore': _multiprocessing.sem_unlink,
})
_CLEANUP_FUNCS.update({
'semaphore': _multiprocessing.sem_unlink,
'shared_memory': _posixshmem.shm_unlink,
})