IssueTracker

In https://android.googlesource.com/platform/art/+/refs/heads/main/runtime/gc/collector/concurrent_copying.cc, ConcurrentCopying::Copy:

  memcpy(reinterpret_cast<uint8_t*>(to_ref) + kObjectHeaderSize,
         reinterpret_cast<const uint8_t*>(from_ref) + kObjectHeaderSize,
         obj_size - kObjectHeaderSize);
  while (true) {
    ......
    bool success = from_ref->CasLockWord(old_lock_word,
                                         new_lock_word,
                                         CASMode::kWeak,
                                         std::memory_order_release);
    if (LIKELY(success)) {
      // The CAS succeeded.
      ......
      QuasiAtomic::ThreadFenceForConstructor();
      ......
    } else {
      ......
    }
  }

There is a release when CAS the LockWord for from_ref, and later a fence to make the memory in to_ref visiable if CAS success.

But if another thread read the fwd_ptr(to_ref) and then try to load its field between the CAS and fence, is the visibility guaranteed?