gh-92530: Fix an issue that occurred after interrupting threading.Condition.notify...

If Condition.notify() was interrupted just after it released the waiter lock,
but before removing it from the queue, the following calls of notify() failed
with RuntimeError: cannot release un-acquired lock.

diff --git a/Lib/threading.py b/Lib/threading.py
index 40edcde11539d65521550f323cd2e81f1d68e382..a3df587f10666cbb52497fcb4de6b20f5da5a9eb 100644 (file)
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -368,14 +368,21 @@ class Condition:
         """
         if not self._is_owned():
             raise RuntimeError("cannot notify on un-acquired lock")
-        all_waiters = self._waiters
-        waiters_to_notify = _deque(_islice(all_waiters, n))
-        if not waiters_to_notify:
-            return
-        for waiter in waiters_to_notify:
-            waiter.release()
+        waiters = self._waiters
+        while waiters and n > 0:
+            waiter = waiters[0]
+            try:
+                waiter.release()
+            except RuntimeError:
+                # gh-92530: The previous call of notify() released the lock,
+                # but was interrupted before removing it from the queue.
+                # It can happen if a signal handler raises an exception,
+                # like CTRL+C which raises KeyboardInterrupt.
+                pass
+            else:
+                n -= 1
             try:
-                all_waiters.remove(waiter)
+                waiters.remove(waiter)
             except ValueError:
                 pass
 

diff --git a/Misc/NEWS.d/next/Library/2022-05-09-09-28-02.gh-issue-92530.M4Q1RS.rst b/Misc/NEWS.d/next/Library/2022-05-09-09-28-02.gh-issue-92530.M4Q1RS.rst
new file mode 100644 (file)
index 0000000..8bb8ca0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-05-09-09-28-02.gh-issue-92530.M4Q1RS.rst
@@ -0,0 +1,2 @@
+Fix an issue that occurred after interrupting
+:func:`threading.Condition.notify`.