bpo-35424: Fix test_multiprocessing_main_handling (GH-11223) (GH-11227)

Fix test_multiprocessing_main_handling: use multiprocessing.Pool with a context manager and then explicitly join the pool. (cherry picked from commit 6cdce3d) Co-authored-by: Victor Stinner <vstinner@redhat.com>

Author: miss-islington

Lib/test/test_multiprocessing_main_handling.py

@@ -54,18 +54,21 @@ def f(x):
 if __name__ == '__main__':
  start_method = sys.argv[1]
  set_start_method(start_method)
- p = Pool(5)
  results = []
- p.map_async(f, [1, 2, 3], callback=results.extend)
- start_time = time.monotonic()
- while not results:
- time.sleep(0.05)
- # up to 1 min to report the results
- dt = time.monotonic() - start_time
- if dt > 60.0:
- raise RuntimeError("Timed out waiting for results (%.1f sec)" % dt)
+ with Pool(5) as pool:
+ pool.map_async(f, [1, 2, 3], callback=results.extend)
+ start_time = time.monotonic()
+ while not results:
+ time.sleep(0.05)
+ # up to 1 min to report the results
+ dt = time.monotonic() - start_time
+ if dt > 60.0:
+ raise RuntimeError("Timed out waiting for results (%.1f sec)" % dt)
+
  results.sort()
  print(start_method, "->", results)
+
+ pool.join()
 """
 
 test_source_main_skipped_in_children = """\
@@ -84,18 +87,21 @@ def f(x):
 
 start_method = sys.argv[1]
 set_start_method(start_method)
-p = Pool(5)
 results = []
-p.map_async(int, [1, 4, 9], callback=results.extend)
-start_time = time.monotonic()
-while not results:
- time.sleep(0.05)
- # up to 1 min to report the results
- dt = time.monotonic() - start_time
- if dt > 60.0:
- raise RuntimeError("Timed out waiting for results (%.1f sec)" % dt)
+with Pool(5) as pool:
+ pool.map_async(int, [1, 4, 9], callback=results.extend)
+ start_time = time.monotonic()
+ while not results:
+ time.sleep(0.05)
+ # up to 1 min to report the results
+ dt = time.monotonic() - start_time
+ if dt > 60.0:
+ raise RuntimeError("Timed out waiting for results (%.1f sec)" % dt)
+
 results.sort()
 print(start_method, "->", results)
+
+pool.join()
 """
 
 # These helpers were copied from test_cmd_line_script & tweaked a bit...

Misc/NEWS.d/next/Tests/2018-12-18-22-36-53.bpo-35424.1Pz4IS.rst

@@ -0,0 +1,2 @@
+Fix test_multiprocessing_main_handling: use :class:`multiprocessing.Pool` with
+a context manager and then explicitly join the pool.