[Python-checkins] cpython (2.7): Issue #14308: Fix an exception when a "dummy" thread is in the threading

[antoine.pitrou]

http://hg.python.org/cpython/rev/ab9d6c4907e7
changeset:   76420:ab9d6c4907e7
branch:      2.7
parent:      76413:36c901fcfcda
user:        Antoine Pitrou <solipsis at pitrou.net>
date:        Thu Apr 19 23:55:01 2012 +0200
summary:
  Issue #14308: Fix an exception when a "dummy" thread is in the threading module's active list after a fork().

files:
  Lib/test/test_threading.py |  29 ++++++++++++++++++++++++++
  Lib/threading.py           |   4 +++
  Misc/NEWS                  |   3 ++
  3 files changed, 36 insertions(+), 0 deletions(-)


diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -2,6 +2,8 @@
 
 import test.test_support
 from test.test_support import verbose
+from test.script_helper import assert_python_ok
+
 import random
 import re
 import sys
@@ -414,6 +416,33 @@
                          msg=('%d references still around' %
                               sys.getrefcount(weak_raising_cyclic_object())))
 
+    @unittest.skipUnless(hasattr(os, 'fork'), 'test needs fork()')
+    def test_dummy_thread_after_fork(self):
+        # Issue #14308: a dummy thread in the active list doesn't mess up
+        # the after-fork mechanism.
+        code = """if 1:
+            import thread, threading, os, time
+
+            def background_thread(evt):
+                # Creates and registers the _DummyThread instance
+                threading.current_thread()
+                evt.set()
+                time.sleep(10)
+
+            evt = threading.Event()
+            thread.start_new_thread(background_thread, (evt,))
+            evt.wait()
+            assert threading.active_count() == 2, threading.active_count()
+            if os.fork() == 0:
+                assert threading.active_count() == 1, threading.active_count()
+                os._exit(0)
+            else:
+                os.wait()
+        """
+        _, out, err = assert_python_ok("-c", code)
+        self.assertEqual(out, '')
+        self.assertEqual(err, '')
+
 
 class ThreadJoinOnShutdown(BaseTestCase):
 
diff --git a/Lib/threading.py b/Lib/threading.py
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -605,6 +605,10 @@
                     pass
 
     def __stop(self):
+        # DummyThreads delete self.__block, but they have no waiters to
+        # notify anyway (join() is forbidden on them).
+        if not hasattr(self, '_Thread__block'):
+            return
         self.__block.acquire()
         self.__stopped = True
         self.__block.notify_all()
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -50,6 +50,9 @@
 Library
 -------
 
+- Issue #14308: Fix an exception when a "dummy" thread is in the threading
+  module's active list after a fork().
+
 - Issue #14538: HTMLParser can now parse correctly start tags that contain
   a bare '/'.
 

-- 
Repository URL: http://hg.python.org/cpython