message: fixed a dead lock after fork.
diff: @@ -625,6 +625,7 @@ void MeshableArena::prepareForFork() {
  // debug("%d: prepare fork", getpid());
  runtime().heap().lock();
  runtime().lock();
  + internal::Heap().lock();
  int r = mprotect(_arenaBegin, kArenaSize, PROT_READ);
  hard_assert(r == 0);
  @@ -640,6 +641,8 @@ void MeshableArena::afterForkParent() {
  return;
  }
  + internal::Heap().unlock();
  +
  close(_forkPipe[1]);
  char buf[8];
  @@ -684,6 +687,7 @@ void MeshableArena::afterForkChild() {
  }
  // debug("%d: after fork child", getpid());
  + internal::Heap().unlock();
  runtime().unlock();
  runtime().heap().unlock();
  