From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from buildserver.ru.mvista.com (unknown [213.79.90.228]) by ozlabs.org (Postfix) with ESMTP id AC229DDEDA for ; Sat, 2 May 2009 10:13:32 +1000 (EST) Date: Sat, 2 May 2009 04:13:29 +0400 From: Anton Vorontsov To: Ingo Molnar Subject: [PATCH v5 0/3] Tracers vs. CALLER_ADDR on PowerPC Message-ID: <20090502001329.GA11549@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Cc: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Steven Rostedt , Paul Mackerras , Sam Ravnborg Reply-To: avorontsov@ru.mvista.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi all, In v5 there are few fixes suggested by Sam Ravnborg: - Use 8 spaces for indentation in Makefile; - Rename ARCH_HAS_NORMAL_FRAME_POINTERS to HAVE_NORMAL_FRAME_POINTER; Thanks, --- Preface for those who don't know or forgot what the problem is: Gcc frame pointers do nothing useful on PowerPC (they're harmful, actually), and thus lib/Kconfig.debug makes CONFIG_FRAME_POINTER unselectable on PPC targets, but CALLER_ADDR macros are available only with CONFIG_FRAME_POINTER, therefore tracing is completely useless on PowerPC: [...] -0 0X.h3 2us+: 0:140:R + [000] 1733:120:S mvtsd -0 0X.h3 9us+: 0 (0) -0 0X..3 72us : 0 (0) -0 0X..3 73us : 0:140:R ==> [000] 1733:120:R mvtsd While it should look like this: [...] -0 0X.h3 2us+: 0:140:R + [000] 1740:120:S mvtsd -0 0X.h3 9us+: hrtimer_wakeup (__run_hrtimer) -0 0X..3 87us : cpu_idle (__got2_end) -0 0X..3 89us : 0:140:R ==> [000] 1740:120:R mvtsd I've tried to fix the issue via expanding the #ifdef in the ftrace.h: http://lkml.org/lkml/2009/1/31/141 Then Steven Rostedt suggested to implement something more generic, i.e. HAVE_NORMAL_FRAME_POINTERS Kconfig symbol. I found a way to solve the problem w/o additional symbols, but with some Makefile magic (http://lkml.org/lkml/2009/2/4/273). But because of top-level Makefile issues on other arches (http://lkml.org/lkml/2009/2/14/89) I had to abandon the approach. So, this patch set combines Steven Rostedt's idea and a small Makefile change, so that now only top-level Makefile has to know about the new symbol, and the rest of the kernel can stay with using CONFIG_FRAME_POINTER. I'm aware of commit c79a61f55773d2519fd0525bf58385f7d20752d3 Author: Uwe Kleine-Koenig Date: Fri Feb 27 21:30:03 2009 +0100 tracing: make CALLER_ADDRx overwriteable But I think the patch set is still applicable, considering that it removes gcc bug workaround in a nice way, and makes CONFIG_FRAME_POINTER available on PowerPC, thus other code can rely on that. If not, I can just fill-in the asm/ftrace.h for PowerPC. -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758631AbZEBANk (ORCPT ); Fri, 1 May 2009 20:13:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753249AbZEBANb (ORCPT ); Fri, 1 May 2009 20:13:31 -0400 Received: from ru.mvista.com ([213.79.90.228]:7128 "EHLO buildserver.ru.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750933AbZEBANa (ORCPT ); Fri, 1 May 2009 20:13:30 -0400 Date: Sat, 2 May 2009 04:13:29 +0400 From: Anton Vorontsov To: Ingo Molnar Cc: Steven Rostedt , Sam Ravnborg , Paul Mackerras , Benjamin Herrenschmidt , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 0/3] Tracers vs. CALLER_ADDR on PowerPC Message-ID: <20090502001329.GA11549@oksana.dev.rtsoft.ru> Reply-To: avorontsov@ru.mvista.com MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, In v5 there are few fixes suggested by Sam Ravnborg: - Use 8 spaces for indentation in Makefile; - Rename ARCH_HAS_NORMAL_FRAME_POINTERS to HAVE_NORMAL_FRAME_POINTER; Thanks, --- Preface for those who don't know or forgot what the problem is: Gcc frame pointers do nothing useful on PowerPC (they're harmful, actually), and thus lib/Kconfig.debug makes CONFIG_FRAME_POINTER unselectable on PPC targets, but CALLER_ADDR macros are available only with CONFIG_FRAME_POINTER, therefore tracing is completely useless on PowerPC: [...] -0 0X.h3 2us+: 0:140:R + [000] 1733:120:S mvtsd -0 0X.h3 9us+: 0 (0) -0 0X..3 72us : 0 (0) -0 0X..3 73us : 0:140:R ==> [000] 1733:120:R mvtsd While it should look like this: [...] -0 0X.h3 2us+: 0:140:R + [000] 1740:120:S mvtsd -0 0X.h3 9us+: hrtimer_wakeup (__run_hrtimer) -0 0X..3 87us : cpu_idle (__got2_end) -0 0X..3 89us : 0:140:R ==> [000] 1740:120:R mvtsd I've tried to fix the issue via expanding the #ifdef in the ftrace.h: http://lkml.org/lkml/2009/1/31/141 Then Steven Rostedt suggested to implement something more generic, i.e. HAVE_NORMAL_FRAME_POINTERS Kconfig symbol. I found a way to solve the problem w/o additional symbols, but with some Makefile magic (http://lkml.org/lkml/2009/2/4/273). But because of top-level Makefile issues on other arches (http://lkml.org/lkml/2009/2/14/89) I had to abandon the approach. So, this patch set combines Steven Rostedt's idea and a small Makefile change, so that now only top-level Makefile has to know about the new symbol, and the rest of the kernel can stay with using CONFIG_FRAME_POINTER. I'm aware of commit c79a61f55773d2519fd0525bf58385f7d20752d3 Author: Uwe Kleine-Koenig Date: Fri Feb 27 21:30:03 2009 +0100 tracing: make CALLER_ADDRx overwriteable But I think the patch set is still applicable, considering that it removes gcc bug workaround in a nice way, and makes CONFIG_FRAME_POINTER available on PowerPC, thus other code can rely on that. If not, I can just fill-in the asm/ftrace.h for PowerPC. -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2