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>
diff --git a/Lib/multiprocessing/resource_tracker.py b/Lib/multiprocessing/resource_tracker.py
index c9bfa9b..cc42dbd 100644
--- a/Lib/multiprocessing/resource_tracker.py
+++ b/Lib/multiprocessing/resource_tracker.py
@@ -37,8 +37,16 @@
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,
})