From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 22 Oct 2009 18:17:10 +0200 (CEST) Received: from mail3.caviumnetworks.com ([12.108.191.235]:17080 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by ftp.linux-mips.org with ESMTP id S1493711AbZJVQRE (ORCPT ); Thu, 22 Oct 2009 18:17:04 +0200 Received: from caexch01.caveonetworks.com (Not Verified[192.168.16.9]) by mail3.caviumnetworks.com with MailMarshal (v6,5,4,7535) id ; Thu, 22 Oct 2009 09:17:00 -0700 Received: from caexch01.caveonetworks.com ([192.168.16.9]) by caexch01.caveonetworks.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 22 Oct 2009 09:16:25 -0700 Received: from dd1.caveonetworks.com ([12.108.191.236]) by caexch01.caveonetworks.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959); Thu, 22 Oct 2009 09:16:25 -0700 Message-ID: <4AE08559.40806@caviumnetworks.com> Date: Thu, 22 Oct 2009 09:16:25 -0700 From: David Daney User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: rostedt@goodmis.org CC: wuzhangjin@gmail.com, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, Thomas Gleixner , Ralf Baechle , Nicholas Mc Guire Subject: Re: [PATCH -v4 9/9] tracing: add function graph tracer support for MIPS References: <028867b99ec532b84963a35e7d552becc783cafc.1256135456.git.wuzhangjin@gmail.com> <96110ea5dd4d3d54eb97d0bb708a5bd81c7a50b5.1256135456.git.wuzhangjin@gmail.com> <5dda13e8e3a9c9dba4bb7179183941bda502604f.1256135456.git.wuzhangjin@gmail.com> <53bdfdd95ec4fa00d4cc505bb5972cf21243a14d.1256135456.git.wuzhangjin@gmail.com> <1256141540.18347.3118.camel@gandalf.stny.rr.com> <4ADF38D5.9060100@caviumnetworks.com> <1256143568.18347.3169.camel@gandalf.stny.rr.com> <4ADF3FE0.5090104@caviumnetworks.com> <1256145813.18347.3210.camel@gandalf.stny.rr.com> <1256211516.3852.47.camel@falcon> <4AE08173.7070500@caviumnetworks.com> <1256227916.20866.784.camel@gandalf.stny.rr.com> In-Reply-To: <1256227916.20866.784.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 22 Oct 2009 16:16:25.0743 (UTC) FILETIME=[00ECB1F0:01CA5333] Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 24445 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ddaney@caviumnetworks.com Precedence: bulk X-list: linux-mips Steven Rostedt wrote: > On Thu, 2009-10-22 at 08:59 -0700, David Daney wrote: > >> This is what I was talking about up-thread. Leaf functions may have no >> function prolog. If you do code scanning you will fail. While scanning >> backwards, there is no way to know when you have entered a new function. >> Looking for function return sequences 'jr ra' doesn't work as there >> may be functions with multiple return sites, functions that never >> return, or arbitrary data before the function. I think you have to >> force a frame pointer to be established if you want this to work. > > Functions that run off into another function?? I guess the compiler > could do that, but with -pg enable, I would think is broken. > Use of GCC-4.5's __builtin_unreachable() can lead to this, as well as functions that call noreturn functions. Note to self: Time to resend the __builtin_unreachable() patch set again... David Daney