[vm, gc] Require a safepoint for heap iteration.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/address_sanitizer.h"
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
@@ skipping 95 matching lines @@
   delete memory_;
 
   // For a heap page from a snapshot, the HeapPage object lives in the malloc
   // heap rather than the page itself.
   if (image_page) {
     free(this);
   }
 }
 
 void HeapPage::VisitObjects(ObjectVisitor* visitor) const {
+  ASSERT(Thread::Current()->IsAtSafepoint());
   NoSafepointScope no_safepoint;
   uword obj_addr = object_start();
   uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     visitor->VisitObject(raw_obj);
     obj_addr += raw_obj->Size();
   }
   ASSERT(obj_addr == end_addr);
 }
 
 void HeapPage::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
+  ASSERT(Thread::Current()->IsAtSafepoint());
   NoSafepointScope no_safepoint;
   uword obj_addr = object_start();
   uword end_addr = object_end();
   while (obj_addr < end_addr) {
     RawObject* raw_obj = RawObject::FromAddr(obj_addr);
     obj_addr += raw_obj->VisitPointers(visitor);
   }
   ASSERT(obj_addr == end_addr);
 }
 
@@ skipping 607 matching lines @@
                        static_cast<intptr_t>(kObjectAlignment));
   heap_map.AddProperty("pageSizeBytes", kPageSizeInWords * kWordSize);
   {
     JSONObject class_list(&heap_map, "classList");
     isolate->class_table()->PrintToJSONObject(&class_list);
   }
   {
     // "pages" is an array [page0, page1, ..., pageN], each page of the form
     // {"object_start": "0x...", "objects": [size, class id, size, ...]}
     // TODO(19445): Use ExclusivePageIterator once HeapMap supports large pages.
+    HeapIterationScope iteration(Thread::Current());
     MutexLocker ml(pages_lock_);
     MakeIterable();
-    NoSafepointScope no_safepoint;
     JSONArray all_pages(&heap_map, "pages");
     for (HeapPage* page = pages_; page != NULL; page = page->next()) {
       JSONObject page_container(&all_pages);
       page_container.AddPropertyF("objectStart", "0x%" Px "",
                                   page->object_start());
       JSONArray page_map(&page_container, "objects");
       HeapMapAsJSONVisitor printer(&page_map);
       page->VisitObjects(&printer);
     }
     for (HeapPage* page = exec_pages_; page != NULL; page = page->next()) {
@@ skipping 506 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>(
         (static_cast<double>(gc_time) / static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart