Merge pull request #75 from ruby/pz-sync-16830

Reverse sync ruby/ruby@06fc5c2

Author: peterzhu2118

gc/gc.h

@@ -11,15 +11,13 @@
  */
 #include "ruby/ruby.h"
 
-#if USE_MODULAR_GC
 #include "ruby/thread_native.h"
 
 struct rb_gc_vm_context {
     rb_nativethread_lock_t lock;
 
     struct rb_execution_context_struct *ec;
 };
-#endif
 
 typedef int (*vm_table_foreach_callback_func)(VALUE value, void *data);
 typedef int (*vm_table_update_callback_func)(VALUE *value, void *data);

gc/gc_impl.h

@@ -54,6 +54,7 @@ GC_IMPL_FN void rb_gc_impl_stress_set(void *objspace_ptr, VALUE flag);
 GC_IMPL_FN VALUE rb_gc_impl_stress_get(void *objspace_ptr);
 GC_IMPL_FN VALUE rb_gc_impl_config_get(void *objspace_ptr);
 GC_IMPL_FN void rb_gc_impl_config_set(void *objspace_ptr, VALUE hash);
+GC_IMPL_FN struct rb_gc_vm_context *rb_gc_impl_get_vm_context(void *objspace_ptr);
 // Object allocation
 GC_IMPL_FN VALUE rb_gc_impl_new_obj(void *objspace_ptr, void *cache_ptr, VALUE klass, VALUE flags, bool wb_protected, size_t alloc_size);
 GC_IMPL_FN size_t rb_gc_impl_obj_slot_size(VALUE obj);

gc/mmtk/mmtk.c

@@ -253,11 +253,7 @@ rb_mmtk_scan_gc_roots(void)
 {
     struct objspace *objspace = rb_gc_get_objspace();
 
-    // FIXME: Make `rb_gc_mark_roots` aware that the current thread may not have EC.
-    // See: https://github.com/ruby/mmtk/issues/22
-    rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
     rb_gc_mark_roots(objspace, NULL);
-    rb_gc_worker_thread_unset_vm_context(&objspace->vm_context);
 }
 
 static int
@@ -784,6 +780,14 @@ rb_gc_impl_config_set(void *objspace_ptr, VALUE hash)
     // TODO
 }
 
+struct rb_gc_vm_context *
+rb_gc_impl_get_vm_context(void *objspace_ptr)
+{
+    struct objspace *objspace = objspace_ptr;
+
+    return &objspace->vm_context;
+}
+
 // Object allocation
 
 static VALUE