8165489: Missing G1 barrier in Unsafe_GetObjectVolatile
Summary: Add missing barrier, sharing code with Unsafe_GetObject.
Reviewed-by: kbarrett, mgerdin, pliden
--- a/hotspot/src/share/vm/prims/unsafe.cpp Fri Sep 16 13:15:01 2016 -0700
+++ b/hotspot/src/share/vm/prims/unsafe.cpp Tue Sep 06 13:01:27 2016 +0200
@@ -272,6 +272,31 @@
// Get/PutObject 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
+}
+
// These functions allow a null base pointer with an arbitrary address.
// But if the base pointer is non-null, the offset should make some sense.
// That is, it should be in the range [0, MAX_OBJECT_SIZE].
@@ -286,34 +311,9 @@
v = *(oop*)index_oop_from_field_offset_long(p, offset);
}
- 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;
+ ensure_satb_referent_alive(p, offset, v);
- 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;
- }
- }
- }
-
- 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_PutObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
@@ -344,6 +344,8 @@
(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