Revert "Turn on concurrent set deletions in sweep thread"

This reverts commit c3ae962.

Author: luke-gruber

gc.c

@@ -2298,6 +2298,10 @@ bool
 rb_gc_obj_has_blacklisted_vm_weak_references(VALUE obj)
 {
     switch (BUILTIN_TYPE(obj)) {
+      case T_STRING:
+        return FL_TEST_RAW(obj, RSTRING_FSTR);
+      case T_SYMBOL:
+        return true;
       case T_IMEMO:
         switch (imemo_type(obj)) {
           case imemo_callcache: {
@@ -2325,18 +2329,6 @@ rb_gc_obj_free_whitelisted_vm_weak_references_in_sweep_thread(VALUE obj)
         bool freed_generic = rb_free_generic_ivar(obj);
         if (!freed_generic) result = false;
     }
-    switch (BUILTIN_TYPE(obj)) {
-      case T_STRING:
-        if (FL_TEST_RAW(obj, RSTRING_FSTR)) {
-            rb_gc_free_fstring(obj);
-        }
-        break;
-      case T_SYMBOL:
-        rb_gc_free_dsymbol(obj);
-        break;
-      default:
-        break;
-    }
     return result;
 }
 

gc/default/default.c

@@ -4480,7 +4480,6 @@ gc_pre_sweep_plane(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *p
               case T_BIGNUM:
               case T_OBJECT:
               case T_STRING:
-              case T_SYMBOL:
               case T_ARRAY:
               case T_HASH:
               case T_STRUCT:
@@ -4497,7 +4496,7 @@ gc_pre_sweep_plane(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *p
                 }
                 break;
               }
-              default: // ex: T_CLASS/T_MODULE/T_ICLASS
+              default: // ex: T_CLASS/T_MODULE/T_ICLASS/T_SYMBOL
                 debug_free_check(objspace, vp);
                 if (!rb_gc_obj_needs_cleanup_p(vp)) {
                     heap_page_add_deferred_freeobj(objspace, page, vp);