Enable iterating over roots from helper threads by moving stack walking.

This will be needed for helper threads to invoke GC.

BUG=
R=johnmccutchan@google.com

Review URL: https://codereview.chromium.org//1282423003 .

runtime/vm/heap.cc

@@ -231,12 +231,15 @@ HeapIterationScope::HeapIterationScope()
   MonitorLocker ml(old_space_->tasks_lock());
 #if defined(DEBUG)
   // We currently don't support nesting of HeapIterationScopes.
-  ASSERT(!old_space_->is_iterating_);
-  old_space_->is_iterating_ = true;
+  ASSERT(old_space_->iterating_thread_ != thread());
 #endif
   while (old_space_->tasks() > 0) {
     ml.Wait();
   }
+#if defined(DEBUG)
+  ASSERT(old_space_->iterating_thread_ == NULL);
+  old_space_->iterating_thread_ = thread();
+#endif
   old_space_->set_tasks(1);
 }
 
@@ -244,8 +247,8 @@ HeapIterationScope::HeapIterationScope()
 HeapIterationScope::~HeapIterationScope() {
   MonitorLocker ml(old_space_->tasks_lock());
 #if defined(DEBUG)
-  ASSERT(old_space_->is_iterating_);
-  old_space_->is_iterating_ = false;
+  ASSERT(old_space_->iterating_thread_ == thread());
+  old_space_->iterating_thread_ = NULL;
 #endif
   ASSERT(old_space_->tasks() == 1);
   old_space_->set_tasks(0);

runtime/vm/isolate.cc

@@ -1598,14 +1598,6 @@ void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
   // Visit objects in isolate specific handles area.
   reusable_handles_.VisitObjectPointers(visitor);
 
-  // Iterate over all the stack frames and visit objects on the stack.
-  StackFrameIterator frames_iterator(validate_frames);
-  StackFrame* frame = frames_iterator.NextFrame();
-  while (frame != NULL) {
-    frame->VisitObjectPointers(visitor);
-    frame = frames_iterator.NextFrame();
-  }
-
   // Visit the dart api state for all local and persistent handles.
   if (api_state() != NULL) {
     api_state()->VisitObjectPointers(visitor, visit_prologue_weak_handles);

runtime/vm/pages.cc

@@ -161,7 +161,7 @@ PageSpace::PageSpace(Heap* heap,
       tasks_lock_(new Monitor()),
       tasks_(0),
 #if defined(DEBUG)
-      is_iterating_(false),
+      iterating_thread_(NULL),
 #endif
       page_space_controller_(heap,
                              FLAG_old_gen_growth_space_ratio,

runtime/vm/pages.h

@@ -427,7 +427,7 @@ class PageSpace {
   Monitor* tasks_lock_;
   intptr_t tasks_;
 #if defined(DEBUG)
-  bool is_iterating_;
+  Thread* iterating_thread_;
 #endif
   PageSpaceController page_space_controller_;
 

runtime/vm/thread.h

@@ -262,6 +262,7 @@ CACHED_CONSTANTS_LIST(DECLARE_MEMBERS)
   friend class ApiZone;
   friend class Isolate;
   friend class StackZone;
+  friend class ThreadRegistry;
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 

runtime/vm/thread_registry.h

@@ -9,6 +9,7 @@
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
+#include "vm/stack_frame.h"
 #include "vm/thread.h"
 
 namespace dart {
@@ -118,9 +119,19 @@ class ThreadRegistry {
     MonitorLocker ml(monitor_);
     for (int i = 0; i < entries_.length(); ++i) {
       const Entry& entry = entries_[i];
-      Zone* zone = entry.scheduled ? entry.thread->zone() : entry.state.zone;
-      if (zone != NULL) {
-        zone->VisitObjectPointers(visitor);
+      const Thread::State& state =
+          entry.scheduled ? entry.thread->state_ : entry.state;
+      if (state.zone != NULL) {
+        state.zone->VisitObjectPointers(visitor);
+      }
+      // Iterate over all the stack frames and visit objects on the stack.
+      uword efi = state.top_exit_frame_info;
+      if (efi == 0) continue;
+      StackFrameIterator frames_iterator(efi, false);
+      StackFrame* frame = frames_iterator.NextFrame();
+      while (frame != NULL) {
+        frame->VisitObjectPointers(visitor);
+        frame = frames_iterator.NextFrame();
       }
     }
   }

runtime/vm/thread_test.cc

@@ -133,8 +133,9 @@ class TaskWithZoneAllocation : public ThreadPool::Task {
       EXPECT(smi.Value() == unique_smi);
       ObjectCounter counter(isolate_, &smi);
       // Ensure that our particular zone is visited.
-      // TODO(koda): Remove "->thread_registry()" after updating stack walker.
-      isolate_->thread_registry()->VisitObjectPointers(&counter);
+      isolate_->IterateObjectPointers(&counter,
+                                      /* visit_prologue_weak_handles = */ true,
+                                      /* validate_frames = */ true);
       EXPECT_EQ(1, counter.count());
 
       char* unique_chars = zone->PrintToString("unique_str_%" Pd, id_);