fix the hang bugs of memory copying. test=develop

paddle/fluid/operators/fake_quantize_op.cu

@@ -235,11 +235,13 @@ struct FindRangeAbsMaxFunctor<platform::CUDADeviceContext, T> {
 
     int g_find_max;
     memory::Copy(platform::CPUPlace(), &g_find_max, gpu_place, find_max,
-                 sizeof(int), 0);
+                 sizeof(int), ctx.stream());
+    ctx.Wait();
     if (g_find_max) {
       int len;
       memory::Copy(platform::CPUPlace(), &len, gpu_place, out_size_data,
-                   sizeof(int), 0);
+                   sizeof(int), ctx.stream());
+      ctx.Wait();
       FindAbsMaxFunctor<platform::CUDADeviceContext, T>()(ctx, scale_arr, len,
                                                           out_scale_data);
     }
@@ -258,25 +260,26 @@ struct FindMovingAverageAbsMaxFunctor<platform::CUDADeviceContext, T> {
     const auto gpu_place = boost::get<platform::CUDAPlace>(ctx.GetPlace());
 
     T accum;
-    memory::Copy(platform::CPUPlace(), &accum, gpu_place, in_accum.data<T>(),
-                 sizeof(T), 0);
     T state;
-    memory::Copy(platform::CPUPlace(), &state, gpu_place, in_state.data<T>(),
-                 sizeof(T), 0);
     T scale;
+    memory::Copy(platform::CPUPlace(), &accum, gpu_place, in_accum.data<T>(),
+                 sizeof(T), ctx.stream());
+    memory::Copy(platform::CPUPlace(), &state, gpu_place, in_state.data<T>(),
+                 sizeof(T), ctx.stream());
     memory::Copy(platform::CPUPlace(), &scale, gpu_place, cur_scale, sizeof(T),
-                 0);
-
+                 ctx.stream());
+    ctx.Wait();
     state = rate * state + 1;
     accum = rate * accum + scale;
     scale = accum / state;
 
     memory::Copy(gpu_place, out_accum->mutable_data<T>(gpu_place),
-                 platform::CPUPlace(), &accum, sizeof(T), 0);
+                 platform::CPUPlace(), &accum, sizeof(T), ctx.stream());
     memory::Copy(gpu_place, out_state->mutable_data<T>(gpu_place),
-                 platform::CPUPlace(), &state, sizeof(T), 0);
+                 platform::CPUPlace(), &state, sizeof(T), ctx.stream());
     memory::Copy(gpu_place, out_scale->mutable_data<T>(gpu_place),
-                 platform::CPUPlace(), &scale, sizeof(T), 0);
+                 platform::CPUPlace(), &scale, sizeof(T), ctx.stream());
+    ctx.Wait();
   }
 };