Code review.

Author: cykerway

Lib/asyncio/locks.py

@@ -408,17 +408,10 @@ def _wake_up_first(self):
         """Wake up the first waiter if it isn't done."""
         if not self._waiters:
             return
-        try:
-            fut = next(iter(self._waiters))
-        except StopIteration:
-            return
-
-        # .done() necessarily means that a waiter will wake up later on and
-        # either take the lock, or, if it was cancelled and lock wasn't
-        # taken already, will hit this again and wake up a new waiter.
-        if not fut.done():
-            fut.set_result(True)
-
+        for fut in self._waiters:
+            if not fut.done():
+                fut.set_result(True)
+                break
 
 class BoundedSemaphore(Semaphore):
     """A bounded semaphore implementation.

Lib/test/test_asyncio/test_locks.py

@@ -846,7 +846,7 @@ async def c4(result):
         sem.release()
         self.assertEqual(2, sem._value)
 
-        await asyncio.sleep(0.01)
+        await asyncio.sleep(0)
         self.assertEqual(0, sem._value)
         self.assertEqual(3, len(result))
         self.assertTrue(sem.locked())
@@ -888,7 +888,7 @@ async def test_acquire_cancel_before_awoken(self):
         t2.cancel()
         sem.release()
 
-        await asyncio.sleep(0.01)
+        await asyncio.sleep(0)
         num_done = sum(t.done() for t in [t3, t4])
         self.assertEqual(num_done, 1)
         self.assertTrue(t3.done())