From d7ad53f249de459190d88bcb16c819411226be46 Mon Sep 17 00:00:00 2001
From: John Hawthorn <john@hawthorn.email>
Date: Tue, 6 May 2025 19:08:02 -0700
Subject: [PATCH] Acquire VM lock around fork

Otherwise it might be held by another Ractor, causing a deadlock in the
new process.
---
 process.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/process.c b/process.c
index 3aea80495d..605821853e 100644
--- a/process.c
+++ b/process.c
@@ -4132,8 +4132,12 @@ rb_fork_ruby(int *status)
         rb_thread_acquire_fork_lock();
         disable_child_handler_before_fork(&old);
 
-        child.pid = pid = rb_fork();
-        child.error = err = errno;
+        RB_VM_LOCK_ENTER();
+        {
+            child.pid = pid = rb_fork();
+            child.error = err = errno;
+        }
+        RB_VM_LOCK_LEAVE();
 
         disable_child_handler_fork_parent(&old); /* yes, bad name */
         if (