From a64b92edd3b7c9145e014aac9a15821d7b05b71a Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Fri, 29 Aug 2014 23:26:36 +0200
Subject: Issue #22185: Fix an occasional RuntimeError in
 threading.Condition.wait() caused by mutation of the waiters queue without
 holding the lock.

Patch by Doug Zongker.
---
 Lib/threading.py | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

(limited to 'Lib/threading.py')

diff --git a/Lib/threading.py b/Lib/threading.py
index 34070830e7..dfe9d41b9f 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -284,6 +284,7 @@ class Condition:
         waiter.acquire()
         self._waiters.append(waiter)
         saved_state = self._release_save()
+        gotit = False
         try:    # restore state no matter what (e.g., KeyboardInterrupt)
             if timeout is None:
                 waiter.acquire()
@@ -293,14 +294,14 @@ class Condition:
                     gotit = waiter.acquire(True, timeout)
                 else:
                     gotit = waiter.acquire(False)
-                if not gotit:
-                    try:
-                        self._waiters.remove(waiter)
-                    except ValueError:
-                        pass
             return gotit
         finally:
             self._acquire_restore(saved_state)
+            if not gotit:
+                try:
+                    self._waiters.remove(waiter)
+                except ValueError:
+                    pass
 
     def wait_for(self, predicate, timeout=None):
         """Wait until a condition evaluates to True.
-- 
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