# HG changeset patch

# User mdoerr

# Date 1473159687 -7200

#      Tue Sep 06 13:01:27 2016 +0200

# Node ID 7f6e1069a5719c8908b53774d3560ce851c7cd70

# Parent  b8fc1e640c4c7f38ca94131279cb67c4d3de6961

8165489, PR3589: Missing G1 barrier in Unsafe_GetObjectVolatile

Summary: Add missing barrier, sharing code with Unsafe_GetObject.

Reviewed-by: kbarrett, mgerdin, pliden, tschatzl

diff --git openjdk.orig/hotspot/src/share/vm/prims/unsafe.cpp openjdk/hotspot/src/share/vm/prims/unsafe.cpp

--- openjdk.orig/hotspot/src/share/vm/prims/unsafe.cpp

+++ openjdk/hotspot/src/share/vm/prims/unsafe.cpp

@@ -199,37 +199,40 @@

 // Get/SetObject must be special-cased, since it works with handles.

+// We could be accessing the referent field in a reference

+// object. If G1 is enabled then we need to register non-null

+// referent with the SATB barrier.

+

+#if INCLUDE_ALL_GCS

+static bool is_java_lang_ref_Reference_access(oop o, jlong offset) {

+  if (offset == java_lang_ref_Reference::referent_offset && o != NULL) {

+    Klass* k = o->klass();

+    if (InstanceKlass::cast(k)->reference_type() != REF_NONE) {

+      assert(InstanceKlass::cast(k)->is_subclass_of(SystemDictionary::Reference_klass()), "sanity");

+      return true;

+    }

+  }

+ return false;

+}

+#endif

+

+static void ensure_satb_referent_alive(oop o, jlong offset, oop v) {

+#if INCLUDE_ALL_GCS

+  if (UseG1GC && v != NULL && is_java_lang_ref_Reference_access(o, offset)) {

+    G1SATBCardTableModRefBS::enqueue(v);

+  }

+#endif

+}

+

 // The xxx140 variants for backward compatibility do not allow a full-width offset.

 UNSAFE_ENTRY(jobject, Unsafe_GetObject140(JNIEnv *env, jobject unsafe, jobject obj, jint offset))

   UnsafeWrapper("Unsafe_GetObject");

   if (obj == NULL)  THROW_0(vmSymbols::java_lang_NullPointerException());

   GET_OOP_FIELD(obj, offset, v)

-  jobject ret = JNIHandles::make_local(env, v);

-#if INCLUDE_ALL_GCS

-  // We could be accessing the referent field in a reference

-  // object. If G1 is enabled then we need to register a non-null

-  // referent with the SATB barrier.

-  if (UseG1GC) {

-    bool needs_barrier = false;

-    if (ret != NULL) {

-      if (offset == java_lang_ref_Reference::referent_offset) {

-        oop o = JNIHandles::resolve_non_null(obj);

-        Klass* k = o->klass();

-        if (InstanceKlass::cast(k)->reference_type() != REF_NONE) {

-          assert(InstanceKlass::cast(k)->is_subclass_of(SystemDictionary::Reference_klass()), "sanity");

-          needs_barrier = true;

-        }

-      }

-    }

+  ensure_satb_referent_alive(p, offset, v);

-    if (needs_barrier) {

-      oop referent = JNIHandles::resolve(ret);

-      G1SATBCardTableModRefBS::enqueue(referent);

-    }

-  }

-#endif // INCLUDE_ALL_GCS

-  return ret;

+  return JNIHandles::make_local(env, v);

 UNSAFE_END

 UNSAFE_ENTRY(void, Unsafe_SetObject140(JNIEnv *env, jobject unsafe, jobject obj, jint offset, jobject x_h))

@@ -262,32 +265,10 @@

 UNSAFE_ENTRY(jobject, Unsafe_GetObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset))

   UnsafeWrapper("Unsafe_GetObject");

   GET_OOP_FIELD(obj, offset, v)

-  jobject ret = JNIHandles::make_local(env, v);

-#if INCLUDE_ALL_GCS

-  // We could be accessing the referent field in a reference

-  // object. If G1 is enabled then we need to register non-null

-  // referent with the SATB barrier.

-  if (UseG1GC) {

-    bool needs_barrier = false;

-    if (ret != NULL) {

-      if (offset == java_lang_ref_Reference::referent_offset && obj != NULL) {

-        oop o = JNIHandles::resolve(obj);

-        Klass* k = o->klass();

-        if (InstanceKlass::cast(k)->reference_type() != REF_NONE) {

-          assert(InstanceKlass::cast(k)->is_subclass_of(SystemDictionary::Reference_klass()), "sanity");

-          needs_barrier = true;

-        }

-      }

-    }

+  ensure_satb_referent_alive(p, offset, v);

-    if (needs_barrier) {

-      oop referent = JNIHandles::resolve(ret);

-      G1SATBCardTableModRefBS::enqueue(referent);

-    }

-  }

-#endif // INCLUDE_ALL_GCS

-  return ret;

+  return JNIHandles::make_local(env, v);

 UNSAFE_END

 UNSAFE_ENTRY(void, Unsafe_SetObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h))

@@ -312,6 +293,9 @@

   } else {

     (void)const_cast<oop&>(v = *(volatile oop*) addr);

   }

+

+  ensure_satb_referent_alive(p, offset, v);

+

   OrderAccess::acquire();

   return JNIHandles::make_local(env, v);

 UNSAFE_END