pythongh-125541: Make Ctrl-C interrupt threading.Lock.acquire() on Windows

Author: colesbury

Doc/library/_thread.rst

@@ -187,6 +187,9 @@ Lock objects have the following methods:
    .. versionchanged:: 3.2
       Lock acquires can now be interrupted by signals on POSIX.
 
+   .. versionchanged:: 3.14
+      Lock acquires can now be interrupted by signals on Windows.
+
 
 .. method:: lock.release()
 

Misc/NEWS.d/next/Library/2024-10-15-16-50-03.gh-issue-125541.FfhmWo.rst

@@ -0,0 +1,3 @@
+Pressing :kbd:`Ctrl-C` while blocked in :meth:`threading.Lock.acquire` now
+interrupts the function and raises a :exc:`KeyboardInterrupt` exception on
+Windows, similar to how it behaves on macOS and Linux.

Python/parking_lot.c

@@ -111,15 +111,27 @@ _PySemaphore_PlatformWait(_PySemaphore *sema, PyTime_t timeout)
             millis = (DWORD) div;
         }
     }
-    wait = WaitForSingleObjectEx(sema->platform_sem, millis, FALSE);
+
+    // NOTE: we wait on the sigint event even in non-main threads to match the
+    // behavior of the other platforms. Non-main threads will ignore the
+    // Py_PARK_INTR result.
+    HANDLE sigint_event = _PyOS_SigintEvent();
+    HANDLE handles[2] = {sema->platform_sem, sigint_event};
+    wait = WaitForMultipleObjectsEx(2, handles, FALSE, millis, FALSE);
     if (wait == WAIT_OBJECT_0) {
         res = Py_PARK_OK;
     }
+    else if (wait == WAIT_OBJECT_0 + 1) {
+        ResetEvent(sigint_event);
+        res = Py_PARK_INTR;
+    }
     else if (wait == WAIT_TIMEOUT) {
         res = Py_PARK_TIMEOUT;
     }
     else {
-        res = Py_PARK_INTR;
+        _Py_FatalErrorFormat(__func__,
+            "unexpected error from semaphore: %u (error: %u)",
+            wait, GetLastError());
     }
 #elif defined(_Py_USE_SEMAPHORES)
     int err;