From 08ddc335ea34829df756c164ceb13c56f0377d37 Mon Sep 17 00:00:00 2001
From: Koichi Sasada <ko1@atdot.net>
Date: Fri, 30 Oct 2020 16:47:08 +0900
Subject: [PATCH] sync vm->waiting_fds correctly.

vm->waiting_fds is global resource so we need to lock it correctly.
(forgot to sync one place)
---
 thread.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/thread.c b/thread.c
index 007a5cbc7b..1512d645ed 100644
--- a/thread.c
+++ b/thread.c
@@ -4504,7 +4504,13 @@ rb_thread_wait_for_single_fd(int fd, int events, struct timeval *timeout)
         } while (wait_retryable(&result, lerrno, to, end));
     }
     EC_POP_TAG();
-    list_del(&wfd.wfd_node);
+
+    RB_VM_LOCK_ENTER();
+    {
+        list_del(&wfd.wfd_node);
+    }
+    RB_VM_LOCK_LEAVE();
+
     if (state) {
         EC_JUMP_TAG(wfd.th->ec, state);
     }