temoprarily disable the code of use kCUDNN, test=develop (#16205)

* temoprarily disable the code of use kCUDNN, test=develop

* add TODO comment, test=develop

paddle/fluid/operators/activation_op.cc

@@ -76,12 +76,16 @@ framework::OpKernelType GetKernelType(const framework::ExecutionContext& ctx,
                                       const std::string& name) {
   framework::LibraryType library{framework::LibraryType::kPlain};
   framework::DataLayout layout = framework::DataLayout::kAnyLayout;
-#ifdef PADDLE_WITH_CUDA
-  auto it1 = oper.Attrs().find("use_cudnn");
-  if (it1 != oper.Attrs().end() && platform::CanCUDNNBeUsed(ctx)) {
-    library = framework::LibraryType::kCUDNN;
-  }
-#endif
+// FIXME(liuwei1031) temporarily disable the code to unblock users
+// TODO(liuwei1031) figure out the reason behind
+// https://github.com/PaddlePaddle/Paddle/issues/16096
+// and re-enable this in the future
+// #ifdef PADDLE_WITH_CUDA
+//   auto it1 = oper.Attrs().find("use_cudnn");
+//   if (it1 != oper.Attrs().end() && platform::CanCUDNNBeUsed(ctx)) {
+//     library = framework::LibraryType::kCUDNN;
+//   }
+// #endif
 #ifdef PADDLE_WITH_MKLDNN
   auto it = oper.Attrs().find("use_mkldnn");
   if (library == framework::LibraryType::kPlain && it != oper.Attrs().end() &&