src/share/vm/prims/unsafe.cpp

rev 11983 : 8165489: Missing G1 barrier in Unsafe_GetObjectVolatile
Reviewed-by: mgerdin

*** 270,279 ****
--- 270,302 ----
  #endif
  };
  
  // 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.
+ 
+ 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;
+ }
+ 
+ static void ensure_referent_alive(oop v) {
+ #if INCLUDE_ALL_GCS
+   if (UseG1GC && v != NULL) {
+     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].
  UNSAFE_ENTRY(jobject, Unsafe_GetObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset)) {
    oop p = JNIHandles::resolve(obj);
*** 284,321 ****
      v = oopDesc::decode_heap_oop(n);
    } else {
      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;
! 
!     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;
  } UNSAFE_END
  
  UNSAFE_ENTRY(void, Unsafe_PutObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
    oop x = JNIHandles::resolve(x_h);
    oop p = JNIHandles::resolve(obj);
--- 307,321 ----
      v = oopDesc::decode_heap_oop(n);
    } else {
      v = *(oop*)index_oop_from_field_offset_long(p, offset);
    }
  
!   if (is_java_lang_ref_Reference_access(p, offset)) {
!     ensure_referent_alive(v);
    }
  
!   return JNIHandles::make_local(env, v);
  } UNSAFE_END
  
  UNSAFE_ENTRY(void, Unsafe_PutObject(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {
    oop x = JNIHandles::resolve(x_h);
    oop p = JNIHandles::resolve(obj);
*** 342,351 ****
--- 342,355 ----
      (void)const_cast<oop&>(v = oopDesc::decode_heap_oop(n));
    } else {
      (void)const_cast<oop&>(v = *(volatile oop*) addr);
    }
  
+   if (is_java_lang_ref_Reference_access(p, offset)) {
+     ensure_referent_alive(v);
+   }
+ 
    OrderAccess::acquire();
    return JNIHandles::make_local(env, v);
  } UNSAFE_END
  
  UNSAFE_ENTRY(void, Unsafe_PutObjectVolatile(JNIEnv *env, jobject unsafe, jobject obj, jlong offset, jobject x_h)) {