Change intern table to not use WaitHoldingLocks

Bug: 22423014
Change-Id: I9e16b8cb4def72fff73f1783a182877105feb7aa
diff --git a/runtime/gc/collector/mark_sweep.cc b/runtime/gc/collector/mark_sweep.cc
index 4035143..abb1d3d 100644
--- a/runtime/gc/collector/mark_sweep.cc
+++ b/runtime/gc/collector/mark_sweep.cc
@@ -1006,7 +1006,7 @@
 
 void MarkSweep::SweepSystemWeaks(Thread* self) {
   TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings());
-  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
+  ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
   Runtime::Current()->SweepSystemWeaks(this);
 }
 
diff --git a/runtime/gc/weak_root_state.h b/runtime/gc/weak_root_state.h
new file mode 100644
index 0000000..b66f19d
--- /dev/null
+++ b/runtime/gc/weak_root_state.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_GC_WEAK_ROOT_STATE_H_
+#define ART_RUNTIME_GC_WEAK_ROOT_STATE_H_
+
+#include <iosfwd>
+
+namespace art {
+namespace gc {
+
+enum WeakRootState {
+  // Can read or add weak roots.
+  kWeakRootStateNormal,
+  // Need to wait until we can read weak roots.
+  kWeakRootStateNoReadsOrWrites,
+  // Need to mark new weak roots to make sure they don't get swept.
+  kWeakRootStateMarkNewRoots,
+};
+
+std::ostream& operator<<(std::ostream& os, const WeakRootState&);
+
+}  // namespace gc
+}  // namespace art
+
+#endif  // ART_RUNTIME_GC_WEAK_ROOT_STATE_H_