Move __syncthread and fence into barrier.

csrc/kernels/utils.cuh

@@ -438,11 +438,14 @@ __forceinline__ __device__ out_dtype_t extract_required_scale_format(float value
     }
 }
 
-template <int kNumRanks>
+template <int kNumRanks, bool fence=true>
 __forceinline__ __device__ void
 barrier_block(int** barrier_signal_ptrs, int rank) {
     auto thread_id = static_cast<int>(threadIdx.x);
 
+    if (fence)
+        memory_fence();
+
     // Add self-ranks, sub other ranks
     if (thread_id < kNumRanks) {
         atomicAdd_system(barrier_signal_ptrs[rank] + thread_id, FINISHED_SUM_TAG);