fix cached kernel bug when fallback to cpu (#45676)

paddle/fluid/framework/operator.cc

@@ -1447,6 +1447,7 @@ void OperatorWithKernel::RunImpl(const Scope& scope,
                                  const platform::Place& place,
                                  RuntimeContext* runtime_ctx) const {
   platform::DeviceContextPool& pool = platform::DeviceContextPool::Instance();
+  bool fallback_to_cpu = false;
   auto* dev_ctx = pool.Get(place);
 
 #ifdef PADDLE_WITH_ASCEND_CL
@@ -1637,6 +1638,7 @@ void OperatorWithKernel::RunImpl(const Scope& scope,
           || (is_xpu_unsupport && !is_xpu_kp_support)
 #endif
       ) {
+        fallback_to_cpu = true;
         auto phi_cpu_kernel_key =
             FallBackToCpu(*kernel_type_.get(), phi_kernel_key, *this);
         phi_kernel_.reset(
@@ -1720,6 +1722,9 @@ void OperatorWithKernel::RunImpl(const Scope& scope,
       (*kernel_func_)(
           ExecutionContext(*this, exec_scope, *dev_ctx, *runtime_ctx));
     }
+    if (fallback_to_cpu) {
+      phi_kernel_.release();
+    }
   }
 
   if (!transfered_inplace_vars.empty()) {