Fix GC race condition in visit roots

While GC visits roots other code can change the set pending exception
due to lack of synchronization.

Change-Id: If387944ac933a66fe176df066c3a0ea52131cad4
Signed-off-by: Serguei Katkov <serguei.i.katkov@intel.com>

3 files changed, 7 insertions, 3 deletions

diff --git a/compiler/driver/compiler_driver_test.cc b/compiler/driver/compiler_driver_test.cc
index 964dfeb..ca956aa 100644
--- a/compiler/driver/compiler_driver_test.cc
+++ b/compiler/driver/compiler_driver_test.cc
@@ -173,7 +173,10 @@ TEST_F(CompilerDriverTest, AbstractMethodErrorStub) {
   env_->ExceptionClear();
   jclass jlame = env_->FindClass("java/lang/AbstractMethodError");
   EXPECT_TRUE(env_->IsInstanceOf(exception, jlame));
-  Thread::Current()->ClearException();
+  {
+    ScopedObjectAccess soa(Thread::Current());
+    Thread::Current()->ClearException();
+  }
 }
 
 // TODO: need check-cast test (when stub complete & we can throw/catch
diff --git a/runtime/jni_internal.cc b/runtime/jni_internal.cc
index f1284db..9ca3c85 100644
--- a/runtime/jni_internal.cc
+++ b/runtime/jni_internal.cc
@@ -669,7 +669,8 @@ class JNI {
   }
 
   static void ExceptionClear(JNIEnv* env) {
-    static_cast<JNIEnvExt*>(env)->self->ClearException();
+    ScopedObjectAccess soa(env);
+    soa.Self()->ClearException();
   }
 
   static void ExceptionDescribe(JNIEnv* env) {
diff --git a/runtime/thread.h b/runtime/thread.h
index 88b4b0d..6569a96 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -326,7 +326,7 @@ class Thread {
     tlsPtr_.throw_location = throw_location;
   }
 
-  void ClearException() {
+  void ClearException() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     tlsPtr_.exception = nullptr;
     tlsPtr_.throw_location.Clear();
   }