Close the call queue in concurrent.futures.ProcessPoolExecutor when
shutdown() is called, without waiting for the garbage collector to kick in.
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index ff566d3..8082940 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -232,6 +232,7 @@
                 # X.
                 for p in processes:
                     p.join()
+                call_queue.close()
                 return
             else:
                 # Start shutting down by telling a process it can exit.
diff --git a/Misc/NEWS b/Misc/NEWS
index 02b59dc..bf33745 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -30,6 +30,9 @@
 Library
 -------
 
+- Close the call queue in concurrent.futures.ProcessPoolExecutor when
+  shutdown() is called, without waiting for the garbage collector to kick in.
+
 - Issue #11603: Fix a crash when __str__ is rebound as __repr__.  Patch by
   Andreas Stührk.