intermediate changes

ref:ac52b2b4969cd1562fcebef15e16af428f77648b

1 files changed, 9 insertions, 6 deletions

diff --git a/contrib/tools/python3/src/Lib/asyncio/locks.py b/contrib/tools/python3/src/Lib/asyncio/locks.py
index f1ce7324785..d17d7ccd813 100644
--- a/contrib/tools/python3/src/Lib/asyncio/locks.py
+++ b/contrib/tools/python3/src/Lib/asyncio/locks.py
@@ -378,6 +378,7 @@ class Semaphore(_ContextManagerMixin):
             warnings.warn("The loop argument is deprecated since Python 3.8, "
                           "and scheduled for removal in Python 3.10.",
                           DeprecationWarning, stacklevel=2)
+        self._wakeup_scheduled = False
 
     def __repr__(self):
         res = super().__repr__()
@@ -391,6 +392,7 @@ class Semaphore(_ContextManagerMixin):
             waiter = self._waiters.popleft()
             if not waiter.done():
                 waiter.set_result(None)
+                self._wakeup_scheduled = True
                 return
 
     def locked(self):
@@ -406,16 +408,17 @@ class Semaphore(_ContextManagerMixin):
         called release() to make it larger than 0, and then return
         True.
         """
-        while self._value <= 0:
+        # _wakeup_scheduled is set if *another* task is scheduled to wakeup
+        # but its acquire() is not resumed yet
+        while self._wakeup_scheduled or self._value <= 0:
             fut = self._loop.create_future()
             self._waiters.append(fut)
             try:
                 await fut
-            except:
-                # See the similar code in Queue.get.
-                fut.cancel()
-                if self._value > 0 and not fut.cancelled():
-                    self._wake_up_next()
+                # reset _wakeup_scheduled *after* waiting for a future
+                self._wakeup_scheduled = False
+            except exceptions.CancelledError:
+                self._wake_up_next()
                 raise
         self._value -= 1
         return True