Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752876AbdCWD2n (ORCPT ); Wed, 22 Mar 2017 23:28:43 -0400 Received: from mail-qk0-f181.google.com ([209.85.220.181]:33101 "EHLO mail-qk0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753043AbdCWD2Q (ORCPT ); Wed, 22 Mar 2017 23:28:16 -0400 MIME-Version: 1.0 From: Zong Li Date: Thu, 23 Mar 2017 11:28:03 +0800 Message-ID: Subject: Ftrace: Static function graph not work To: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1637 Lines: 57 Hi all, I test the static function graph for ARM, x86 and x86_64 architecture on linux-3.10 and linux-4.9, and I find it works correctly only for x86_64 on linux-4.9. After the following commit, the function tracer also be registered when registering the function graph tracer. commit 2940c25bec92f40a3f7f32504b8ea115d1701892 Author: Steven Rostedt (Red Hat) CommitDate: Wed Dec 4 10:57:05 2013 -0800 ftrace: Fix function graph with loading of modules The arch-depend code implement the mcount function pseudo code like: void mcount(void) { ... if (ftrace_trace_function != ftrace_stub) goto do_trace; #ifdef CONFIG_FUNCTION_GRAPH_TRACER if (ftrace_graph_return != ftrace_stub || ftrace_graph_entry != ftrace_graph_entry_stub) ftrace_graph_caller(); #endif return; do_trace: ... } The function pointer 'ftrace_trace_function' will not be 'ftrace_stub' because function tracer is registered too, so the function graph part will not be executed. On the other hand, I find the another patch to resolve this situation, and it is reason that x86_64 architecture can work correctly. commit 62a207d748dd9224140a634786b274fdb6ece0b9 Author: Steven Rostedt (Red Hat) CommitDate: Mon Nov 24 15:02:25 2014 -0500 ftrace/x86: Have static function tracing always test for function graph so, is this problem tending to handle by each architecture? or maybe it is need to solve by generic code? This is my first mail to mailing list, please excuse having mistake and let me know. Thank a lot !