From 7dae88f0f5c17a16a298aac97df097e4caca977d Mon Sep 17 00:00:00 2001
From: David Wilson <dw@botanicus.net>
Date: Sun, 27 Jan 2019 18:46:03 +0000
Subject: [PATCH] issue #490: have Side._on_fork() empty _fork_refs

This is mostly to avoid ugly debugging that depends on the state of GC.
Discard sides from _fork_refs after they have been closed.
---
 mitogen/core.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mitogen/core.py b/mitogen/core.py
index 7a698f43..5cb7761f 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -1415,7 +1415,9 @@ class Side(object):
 
     @classmethod
     def _on_fork(cls):
-        for side in list(cls._fork_refs.values()):
+        while cls._fork_refs:
+            _, side = cls._fork_refs.popitem()
+            _vv and IOLOG.debug('Side._on_fork() closing %r', side)
             side.close()
 
     def close(self):