Sync the zombie objspace hook with Ruby master

gc/gc.h

@@ -79,10 +79,7 @@ MODULAR_GC_FN void rb_gc_vm_each_objspace(void (*func)(void *objspace, void *dat
 MODULAR_GC_FN void rb_gc_each_registered_addr(rb_gc_registered_addr_cb func, void *data);
 /* Verifier support, valid only with the world stopped (no extra locking inside). */
 MODULAR_GC_FN bool rb_gc_registered_addr_owned_by_registrant_p(VALUE *addr, void *objspace);
-MODULAR_GC_FN bool rb_gc_vm_zombie_objspace_p(void *objspace);
-MODULAR_GC_FN size_t rb_gc_vm_zombie_total_pages(void);
 MODULAR_GC_FN unsigned int rb_gc_vm_ractor_count(void);
-MODULAR_GC_FN void rb_gc_vm_refresh_zombie_pages(void);
 /* No MODULAR_GC_FN: the VM side (ractor.c) calls this too, so it needs external
  * linkage even in a non-modular build (see internal/gc.h). */
 bool rb_gc_single_objspace_p(void);

gc/gc_impl.h

@@ -153,7 +153,11 @@ GC_IMPL_FN bool rb_gc_impl_during_postmortem_p(void *objspace_ptr);
  * objspace impl. */
 GC_IMPL_FN bool rb_gc_impl_obj_foreign_p(void *objspace_ptr, VALUE obj);
 GC_IMPL_FN bool rb_gc_impl_shref_marked_p(void *objspace_ptr, VALUE obj);
-GC_IMPL_FN size_t rb_gc_impl_zombie_heap_page_count(void *objspace_ptr);
+/* gc.c parked objspace_ptr in its zombie table: a terminated Ractor's objspace that
+ * rb_gc_impl_objspace_absorb later merges.  Called under the VM lock, possibly from
+ * inside a global GC sweep (an unjoined Ractor's dfree disowns its objspace), so it
+ * must not allocate through the GC or expect to take a barrier. */
+GC_IMPL_FN void rb_gc_impl_objspace_zombify(void *objspace_ptr);
 GC_IMPL_FN void rb_gc_impl_objspace_absorb(void *dst_ptr, void *src_ptr);
 GC_IMPL_FN void rb_gc_impl_each_object(void *objspace_ptr, void (*func)(VALUE obj, void *data), void *data);
 // Finalizers
@@ -172,7 +176,7 @@ GC_IMPL_FN unsigned long long rb_gc_impl_get_total_time(void *objspace_ptr);
 GC_IMPL_FN size_t rb_gc_impl_gc_count(void *objspace_ptr);
 GC_IMPL_FN VALUE rb_gc_impl_latest_gc_info(void *objspace_ptr, VALUE key);
 /* A NULL objspace requests cumulative process-wide statistics. Collectors that
- * do not support this scope must raise NotImplementedError. */
+ * do not support them must raise NotImplementedError. */
 GC_IMPL_FN VALUE rb_gc_impl_stat(void *objspace_ptr, VALUE hash_or_sym);
 GC_IMPL_FN VALUE rb_gc_impl_stat_heap(void *objspace_ptr, VALUE heap_name, VALUE hash_or_sym);
 GC_IMPL_FN const char *rb_gc_impl_active_gc_name(void);

gc/mmtk/mmtk.c

@@ -1858,11 +1858,10 @@ rb_gc_impl_shref_marked_p(void *objspace_ptr, VALUE obj)
     return true;
 }
 
-size_t
-rb_gc_impl_zombie_heap_page_count(void *objspace_ptr)
+void
+rb_gc_impl_objspace_zombify(void *objspace_ptr)
 {
     /* With a single objspace zombie_objspaces is always empty. */
-    return 0;
 }
 
 void