From: Charles-François Natali <neologix@free.fr>
Date: Mon, 24 Oct 2011 16:43:51 +0000 (+0200)
Subject: Issue #10332: multiprocessing: fix a race condition when a Pool is closed
X-Git-Tag: v2.7.3rc1~381^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=46f990e58cb462bbf98fef88a3ba41ffa4a4e35d;p=python

Issue #10332: multiprocessing: fix a race condition when a Pool is closed
before all tasks have completed.
---

diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index c66876a856..bcbf7e3503 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -294,7 +294,11 @@ class Pool(object):
 
     @staticmethod
     def _handle_workers(pool):
-        while pool._worker_handler._state == RUN and pool._state == RUN:
+        thread = threading.current_thread()
+
+        # Keep maintaining workers until the cache gets drained, unless the pool
+        # is terminated.
+        while thread._state == RUN or (pool._cache and thread._state != TERMINATE):
             pool._maintain_pool()
             time.sleep(0.1)
         # send sentinel to stop workers
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 201fa98e4a..14847d92a1 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1168,6 +1168,20 @@ class _TestPoolWorkerLifetime(BaseTestCase):
         p.close()
         p.join()
 
+    def test_pool_worker_lifetime_early_close(self):
+        # Issue #10332: closing a pool whose workers have limited lifetimes
+        # before all the tasks completed would make join() hang.
+        p = multiprocessing.Pool(3, maxtasksperchild=1)
+        results = []
+        for i in range(6):
+            results.append(p.apply_async(sqr, (i, 0.3)))
+        p.close()
+        p.join()
+        # check the results
+        for (j, res) in enumerate(results):
+            self.assertEqual(res.get(), sqr(j))
+
+
 #
 # Test that manager has expected number of shared objects left
 #
diff --git a/Misc/NEWS b/Misc/NEWS
index a501954a93..10daf5b56a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -66,6 +66,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #10332: multiprocessing: fix a race condition when a Pool is closed
+  before all tasks have completed.
+
 - Issue #1548891: The cStringIO.StringIO() constructor now encodes unicode
   arguments with the system default encoding just like the write() method
   does, instead of converting it to a raw buffer.  This also fixes handling of