Issue #22853: Fixed a deadlock when use multiprocessing.Queue at import time.

Patch by Florian Finkernagel and Davin Potts.

1 files changed, 20 insertions, 0 deletions

diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index ec4507e..b1e75b5 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -620,6 +620,26 @@ class _TestQueue(BaseTestCase):
         for p in workers:
             p.join()
 
+    def test_no_import_lock_contention(self):
+        with test_support.temp_cwd():
+            module_name = 'imported_by_an_imported_module'
+            with open(module_name + '.py', 'w') as f:
+                f.write("""if 1:
+                    import multiprocessing
+
+                    q = multiprocessing.Queue()
+                    q.put('knock knock')
+                    q.get(timeout=3)
+                    q.close()
+                """)
+
+            with test_support.DirsOnSysPath(os.getcwd()):
+                try:
+                    __import__(module_name)
+                except Queue.Empty:
+                    self.fail("Probable regression on import lock contention;"
+                              " see Issue #22853")
+
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