Clean up the locks around Heap::VisitObjects().

This is so that we could support suspending all threads when visiting
objects in the presence of a concurrent, moving collector.

Bug: 12687968
Change-Id: Icc8e60630465afde948ebc6ea91d4ebaff5d7837

1 files changed, 12 insertions, 23 deletions

diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index 8c7d611d8..ba02338c2 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -501,19 +501,14 @@ void ImageWriter::ProcessStrings() {
   size_t total_strings = 0;
   gc::Heap* heap = Runtime::Current()->GetHeap();
   ClassLinker* cl = Runtime::Current()->GetClassLinker();
-  {
-    ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    heap->VisitObjects(CountStringsCallback, &total_strings);  // Count the strings.
-  }
+  // Count the strings.
+  heap->VisitObjects(CountStringsCallback, &total_strings);
   Thread* self = Thread::Current();
   StackHandleScope<1> hs(self);
   auto strings = hs.NewHandle(cl->AllocStringArray(self, total_strings));
   StringCollector string_collector(strings, 0U);
-  {
-    ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    // Read strings into the array.
-    heap->VisitObjects(StringCollector::Callback, &string_collector);
-  }
+  // Read strings into the array.
+  heap->VisitObjects(StringCollector::Callback, &string_collector);
   // Some strings could have gotten freed if AllocStringArray caused a GC.
   CHECK_LE(string_collector.GetIndex(), total_strings);
   total_strings = string_collector.GetIndex();
@@ -595,7 +590,6 @@ void ImageWriter::ComputeEagerResolvedStringsCallback(Object* obj, void* arg ATT
 }
 
 void ImageWriter::ComputeEagerResolvedStrings() {
-  ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
   Runtime::Current()->GetHeap()->VisitObjects(ComputeEagerResolvedStringsCallback, this);
 }
 
@@ -668,7 +662,6 @@ bool ImageWriter::NonImageClassesVisitor(Class* klass, void* arg) {
 void ImageWriter::CheckNonImageClassesRemoved() {
   if (compiler_driver_.GetImageClasses() != nullptr) {
     gc::Heap* heap = Runtime::Current()->GetHeap();
-    ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
     heap->VisitObjects(CheckNonImageClassesRemovedCallback, this);
   }
 }
@@ -869,17 +862,14 @@ void ImageWriter::CalculateNewObjectOffsets() {
   // know where image_roots is going to end up
   image_end_ += RoundUp(sizeof(ImageHeader), kObjectAlignment);  // 64-bit-alignment
 
-  {
-    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
-    // TODO: Image spaces only?
-    DCHECK_LT(image_end_, image_->Size());
-    image_objects_offset_begin_ = image_end_;
-    // Clear any pre-existing monitors which may have been in the monitor words, assign bin slots.
-    heap->VisitObjects(WalkFieldsCallback, this);
-    // Transform each object's bin slot into an offset which will be used to do the final copy.
-    heap->VisitObjects(UnbinObjectsIntoOffsetCallback, this);
-    DCHECK(saved_hashes_map_.empty());  // All binslot hashes should've been put into vector by now.
-  }
+  // TODO: Image spaces only?
+  DCHECK_LT(image_end_, image_->Size());
+  image_objects_offset_begin_ = image_end_;
+  // Clear any pre-existing monitors which may have been in the monitor words, assign bin slots.
+  heap->VisitObjects(WalkFieldsCallback, this);
+  // Transform each object's bin slot into an offset which will be used to do the final copy.
+  heap->VisitObjects(UnbinObjectsIntoOffsetCallback, this);
+  DCHECK(saved_hashes_map_.empty());  // All binslot hashes should've been put into vector by now.
 
   DCHECK_GT(image_end_, GetBinSizeSum());
 
@@ -920,7 +910,6 @@ void ImageWriter::CopyAndFixupObjects() {
   // TODO: heap validation can't handle this fix up pass
   heap->DisableObjectValidation();
   // TODO: Image spaces only?
-  WriterMutexLock mu(ants.Self(), *Locks::heap_bitmap_lock_);
   heap->VisitObjects(CopyAndFixupObjectsCallback, this);
   // Fix up the object previously had hash codes.
   for (const std::pair<mirror::Object*, uint32_t>& hash_pair : saved_hashes_) {