diff --git a/Lib/multiprocessing/context.py b/Lib/multiprocessing/context.py
index 8d0525d5d62179..b1960ea296fe20 100644
--- a/Lib/multiprocessing/context.py
+++ b/Lib/multiprocessing/context.py
@@ -223,6 +223,10 @@ class Process(process.BaseProcess):
def _Popen(process_obj):
return _default_context.get_context().Process._Popen(process_obj)
+ @staticmethod
+ def _after_fork():
+ return _default_context.get_context().Process._after_fork()
+
class DefaultContext(BaseContext):
Process = Process
@@ -283,6 +287,11 @@ def _Popen(process_obj):
from .popen_spawn_posix import Popen
return Popen(process_obj)
+ @staticmethod
+ def _after_fork():
+ # process is spawned, nothing to do
+ pass
+
class ForkServerProcess(process.BaseProcess):
_start_method = 'forkserver'
@staticmethod
@@ -326,6 +335,11 @@ def _Popen(process_obj):
from .popen_spawn_win32 import Popen
return Popen(process_obj)
+ @staticmethod
+ def _after_fork():
+ # process is spawned, nothing to do
+ pass
+
class SpawnContext(BaseContext):
_name = 'spawn'
Process = SpawnProcess
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index 0b2e0b45b2397b..2d5372e6d947c8 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -304,8 +304,7 @@ def _bootstrap(self, parent_sentinel=None):
if threading._HAVE_THREAD_NATIVE_ID:
threading.main_thread()._set_native_id()
try:
- util._finalizer_registry.clear()
- util._run_after_forkers()
+ self._after_fork()
finally:
# delay finalization of the old process object until after
# _run_after_forkers() is executed
@@ -336,6 +335,13 @@ def _bootstrap(self, parent_sentinel=None):
return exitcode
+ @staticmethod
+ def _after_fork():
+ from . import util
+ util._finalizer_registry.clear()
+ util._run_after_forkers()
+
+
#
# We subclass bytes to avoid accidental transmission of auth keys over network
#
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 04657c08db92c0..1b55cb31c30304 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -5,6 +5,7 @@
import unittest
import unittest.mock
import queue as pyqueue
+import textwrap
import time
import io
import itertools
@@ -5699,6 +5700,35 @@ def test_namespace(self):
self.run_worker(self._test_namespace, o)
+class TestNamedResource(unittest.TestCase):
+ def test_global_named_resource_spawn(self):
+ #
+ # gh-90549: Check that global named resources in main module
+ # will not leak by a subprocess, in spawn context.
+ #
+ testfn = os_helper.TESTFN
+ self.addCleanup(os_helper.unlink, testfn)
+ with open(testfn, 'w', encoding='utf-8') as f:
+ f.write(textwrap.dedent('''\
+ import multiprocessing as mp
+
+ ctx = mp.get_context('spawn')
+
+ global_resource = ctx.Semaphore()
+
+ def submain(): pass
+
+ if __name__ == '__main__':
+ p = ctx.Process(target=submain)
+ p.start()
+ p.join()
+ '''))
+ rc, out, err = test.support.script_helper.assert_python_ok(testfn)
+ # on error, err = 'UserWarning: resource_tracker: There appear to
+ # be 1 leaked semaphore objects to clean up at shutdown'
+ self.assertEqual(err, b'')
+
+
class MiscTestCase(unittest.TestCase):
def test__all__(self):
# Just make sure names in not_exported are excluded
diff --git a/Misc/NEWS.d/next/Library/2022-06-07-14-53-46.gh-issue-90549.T4FMKY.rst b/Misc/NEWS.d/next/Library/2022-06-07-14-53-46.gh-issue-90549.T4FMKY.rst
new file mode 100644
index 00000000000000..6ebdc394900e63
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-06-07-14-53-46.gh-issue-90549.T4FMKY.rst
@@ -0,0 +1,2 @@
+Fix a multiprocessing bug where a global named resource (such as a semaphore)
+could leak when a child process is spawned (as opposed to forked).
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