Issue #19740: Use WaitForSingleObject() instead of trusting TimerOrWaitFired.
diff --git a/Lib/asyncio/windows_events.py b/Lib/asyncio/windows_events.py
index 64fe386..b2ed241 100644
--- a/Lib/asyncio/windows_events.py
+++ b/Lib/asyncio/windows_events.py
@@ -327,14 +327,21 @@
handle, self._iocp, ov.address, ms)
f = _WaitHandleFuture(wh, loop=self._loop)
- def finish(timed_out, _, ov):
+ def finish(trans, key, ov):
if not f.cancelled():
try:
_overlapped.UnregisterWait(wh)
except OSError as e:
if e.winerror != _overlapped.ERROR_IO_PENDING:
raise
- return not timed_out
+ # Note that this second wait means that we should only use
+ # this with handles types where a successful wait has no
+ # effect. So events or processes are all right, but locks
+ # or semaphores are not. Also note if the handle is
+ # signalled and then quickly reset, then we may return
+ # False even though we have not timed out.
+ return (_winapi.WaitForSingleObject(handle, 0) ==
+ _winapi.WAIT_OBJECT_0)
self._cache[ov.address] = (f, ov, None, finish)
return f