[Python-checkins] cpython (2.7): Issue 19158: a rare race in BoundedSemaphore could allow .release() too often.

[tim.peters]

http://hg.python.org/cpython/rev/cb4fd7515cb4
changeset:   86167:cb4fd7515cb4
branch:      2.7
parent:      86161:0bde9bf22c0a
user:        Tim Peters <tim at python.org>
date:        Tue Oct 08 20:55:51 2013 -0500
summary:
  Issue 19158:  a rare race in BoundedSemaphore could allow .release() too often.
(grafted from e06edc0c7a4951327f0c95ebeebccba6879a6063)

files:
  Lib/test/test_threading.py |  17 +++++++++++++++++
  Lib/threading.py           |   8 +++++---
  2 files changed, 22 insertions(+), 3 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
@@ -466,6 +466,23 @@
         finally:
             sys.setcheckinterval(old_interval)
 
+    def test_BoundedSemaphore_limit(self):
+        # BoundedSemaphore should raise ValueError if released too often.
+        for limit in range(1, 10):
+            bs = threading.BoundedSemaphore(limit)
+            threads = [threading.Thread(target=bs.acquire)
+                       for _ in range(limit)]
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+            threads = [threading.Thread(target=bs.release)
+                       for _ in range(limit)]
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+            self.assertRaises(ValueError, bs.release)
 
 class ThreadJoinOnShutdown(BaseTestCase):
 
diff --git a/Lib/threading.py b/Lib/threading.py
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -531,9 +531,11 @@
         raise a ValueError.
 
         """
-        if self._Semaphore__value >= self._initial_value:
-            raise ValueError("Semaphore released too many times")
-        return _Semaphore.release(self)
+        with self._cond:
+            if self._value >= self._initial_value:
+                raise ValueError("Semaphore released too many times")
+            self._value += 1
+            self._cond.notify()
 
 
 def Event(*args, **kwargs):

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