Merge pull request #3164 from graingert/patch-1

make existing_loop check atomic
tornadoweb · Jun 21, 2022 · 7a80716 · 7a80716
2 parents 1de5e68 + a619885
commit 7a80716
Showing 1 changed file with 2 additions and 4 deletions.
diff --git a/tornado/platform/asyncio.py b/tornado/platform/asyncio.py
@@ -131,14 +131,12 @@ def initialize(  # type: ignore
                     pass
 
         # Make sure we don't already have an IOLoop for this asyncio loop
-        if asyncio_loop in IOLoop._ioloop_for_asyncio:
-            existing_loop = IOLoop._ioloop_for_asyncio[asyncio_loop]
+        existing_loop = IOLoop._ioloop_for_asyncio.setdefault(asyncio_loop, self)
+        if existing_loop is not self:
             raise RuntimeError(
                 f"IOLoop {existing_loop} already associated with asyncio loop {asyncio_loop}"
             )
 
-        IOLoop._ioloop_for_asyncio[asyncio_loop] = self
-
         self._thread_identity = 0
 
         super().initialize(**kwargs)