From 5faeea873ba4249c685c7f390e939560d736fea8 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Fri, 8 May 2026 18:02:12 -0400
Subject: Set EC in rb_gc_event_hook

The event hook may use the EC and it will be null when it is running from
a GC thread.
---
 gc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/gc.c b/gc.c
index 0976d6b7b0..1d3f6fa6ed 100644
--- a/gc.c
+++ b/gc.c
@@ -242,7 +242,30 @@ rb_gc_event_hook(VALUE obj, rb_event_flag_t event)
     rb_execution_context_t *ec = rb_gc_get_ec();
     if (!ec->cfp) return;
 
+#if USE_MODULAR_GC
+    bool gc_thread_p = false;
+    if (!GET_EC()) {
+        gc_thread_p = true;
+
+# ifdef RB_THREAD_LOCAL_SPECIFIER
+        rb_current_ec_set(ec);
+# else
+        native_tls_set(ruby_current_ec_key, ec);
+# endif
+    }
+#endif
+
     EXEC_EVENT_HOOK(ec, event, ec->cfp->self, 0, 0, 0, obj);
+
+#if USE_MODULAR_GC
+    if (gc_thread_p) {
+# ifdef RB_THREAD_LOCAL_SPECIFIER
+        rb_current_ec_set(NULL);
+# else
+        native_tls_set(ruby_current_ec_key, NULL);
+# endif
+    }
+#endif
 }
 
 void *
-- 
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