commit 024d69fb9936ca5a0031d35c9f248853cbc25d3f
author Vladimir Marko <vmarko@google.com> Thu Jun 13 10:52:32 2019 +0100
committer Vladimir Marko <vmarko@google.com> Mon Jun 17 09:30:53 2019 +0000
tree c1eeddf91ea15eda5d139d4592ac7f0df80e9be0
parent 43ae4acf219fe25a56e2055ebcebc4d08020a25d

Use cleared JNI weak sentinel from boot image.

We were already adding the sentinel to the boot image,
so we may as well reuse the boot image copy.

Also move pre-allocated objects from class roots to the
boot image live objects.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: aosp_taimen-userdebug boots.
Change-Id: I635dcdd146ca2c6b55d187e9a545a9990b0b35ca

runtime/class_linker.cc

diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 1343b16..b2e7d99 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -951,12 +951,12 @@
   gc::Heap* const heap = runtime->GetHeap();
   std::vector<gc::space::ImageSpace*> spaces = heap->GetBootImageSpaces();
   CHECK(!spaces.empty());
-  uint32_t pointer_size_unchecked = spaces[0]->GetImageHeader().GetPointerSizeUnchecked();
+  const ImageHeader& image_header = spaces[0]->GetImageHeader();
+  uint32_t pointer_size_unchecked = image_header.GetPointerSizeUnchecked();
   if (!ValidPointerSize(pointer_size_unchecked)) {
     *error_msg = StringPrintf("Invalid image pointer size: %u", pointer_size_unchecked);
     return false;
   }
-  const ImageHeader& image_header = spaces[0]->GetImageHeader();
   image_pointer_size_ = image_header.GetPointerSize();
   if (!runtime->IsAotCompiler()) {
     // Only the Aot compiler supports having an image with a different pointer size than the
@@ -1057,15 +1057,15 @@
 
   class_roots_ = GcRoot<mirror::ObjectArray<mirror::Class>>(
       ObjPtr<mirror::ObjectArray<mirror::Class>>::DownCast(
-          spaces[0]->GetImageHeader().GetImageRoot(ImageHeader::kClassRoots)));
+          image_header.GetImageRoot(ImageHeader::kClassRoots)));
   DCHECK_EQ(GetClassRoot<mirror::Class>(this)->GetClassFlags(), mirror::kClassFlagClass);
 
-  ObjPtr<mirror::Class> java_lang_Object = GetClassRoot<mirror::Object>(this);
-  java_lang_Object->SetObjectSize(sizeof(mirror::Object));
-  // Allocate in non-movable so that it's possible to check if a JNI weak global ref has been
-  // cleared without triggering the read barrier and unintentionally mark the sentinel alive.
-  runtime->SetSentinel(heap->AllocNonMovableObject(
-      self, java_lang_Object, java_lang_Object->GetObjectSize(), VoidFunctor()));
+  DCHECK_EQ(GetClassRoot<mirror::Object>(this)->GetObjectSize(), sizeof(mirror::Object));
+  ObjPtr<mirror::ObjectArray<mirror::Object>> boot_image_live_objects =
+      ObjPtr<mirror::ObjectArray<mirror::Object>>::DownCast(
+          image_header.GetImageRoot(ImageHeader::kBootImageLiveObjects));
+  runtime->SetSentinel(boot_image_live_objects->Get(ImageHeader::kClearedJniWeakSentinel));
+  DCHECK(runtime->GetSentinel().Read()->GetClass() == GetClassRoot<mirror::Object>(this));
 
   const std::vector<std::string>& boot_class_path_locations = runtime->GetBootClassPathLocations();
   CHECK_LE(spaces.size(), boot_class_path_locations.size());