[concurrency-interest] jdk9 VarHandle and Fence methods

thurstonn thurston at nomagicsoftware.com
Sun Aug 23 12:17:32 EDT 2015


from unsafe.cpp:

UNSAFE_ENTRY(jboolean, Unsafe_CompareAndSwapObject(JNIEnv *env, jobject
unsafe, jobject obj, jlong offset, jobject e_h, jobject x_h))

  UnsafeWrapper("Unsafe_CompareAndSwapObject");

  oop x = JNIHandles::resolve(x_h);

  oop e = JNIHandles::resolve(e_h);

  oop p = JNIHandles::resolve(obj);

  HeapWord* addr = (HeapWord *)index_oop_from_field_offset_long(p, offset);

  oop res = oopDesc::atomic_compare_exchange_oop(x, addr, e, true);

  jboolean success  = (res == e);

 * if (success)

    update_barrier_set((void*)addr, x);*

  return success;

UNSAFE_END

That's what I was referring to; I  presumed update_barrier_set resulted in
some sort of store fence



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