From 9939cc89a4ee54ab50719a597a8b8a0795a691f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Charles-Fran=C3=A7ois=20Natali?= <cf.natali@gmail.com>
Date: Fri, 30 Aug 2013 23:32:53 +0200
Subject: Issue #18418: After fork(), reinit all threads states, not only
 active ones. Patch by A. Jesse Jiryu Davis.

---
 Lib/test/test_threading.py | 21 +++++++++++++++++++++
 Lib/threading.py           |  2 +-
 Misc/ACKS                  |  1 +
 Misc/NEWS                  |  3 +++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 79967dc..bd019cd 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -444,6 +444,27 @@ class ThreadTests(BaseTestCase):
         self.assertEqual(out, b'')
         self.assertEqual(err, b'')
 
+    @unittest.skipUnless(hasattr(os, 'fork'), "needs os.fork()")
+    def test_is_alive_after_fork(self):
+        # Try hard to trigger #18418: is_alive() could sometimes be True on
+        # threads that vanished after a fork.
+        old_interval = sys.getswitchinterval()
+        self.addCleanup(sys.setswitchinterval, old_interval)
+
+        # Make the bug more likely to manifest.
+        sys.setswitchinterval(1e-6)
+
+        for i in range(20):
+            t = threading.Thread(target=lambda: None)
+            t.start()
+            self.addCleanup(t.join)
+            pid = os.fork()
+            if pid == 0:
+                os._exit(1 if t.is_alive() else 0)
+            else:
+                pid, status = os.waitpid(pid, 0)
+                self.assertEqual(0, status)
+
 
 class ThreadJoinOnShutdown(BaseTestCase):
 
diff --git a/Lib/threading.py b/Lib/threading.py
index aaece74..c98a006 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -935,7 +935,7 @@ def _after_fork():
     new_active = {}
     current = current_thread()
     with _active_limbo_lock:
-        for thread in _active.values():
+        for thread in _enumerate():
             # Any lock/condition variable may be currently locked or in an
             # invalid state, so we reinitialize them.
             thread._reset_internal_locks()
diff --git a/Misc/ACKS b/Misc/ACKS
index 9596db7..20eeafd 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -279,6 +279,7 @@ Ben Darnell
 Kushal Das
 Jonathan Dasteel
 Pierre-Yves David
+A. Jesse Jiryu Davis
 John DeGood
 Ned Deily
 Vincent Delft
diff --git a/Misc/NEWS b/Misc/NEWS
index 4572ae6..d859de1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -66,6 +66,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #18418: After fork(), reinit all threads states, not only active ones.
+  Patch by A. Jesse Jiryu Davis.
+
 - Issue #16611: http.cookie now correctly parses the 'secure' and 'httponly'
   cookie flags.
 
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