From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755461AbaHHCgP (ORCPT ); Thu, 7 Aug 2014 22:36:15 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:15119 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752825AbaHHCgJ convert rfc822-to-8bit (ORCPT ); Thu, 7 Aug 2014 22:36:09 -0400 Date: Thu, 7 Aug 2014 22:35:53 -0400 From: Steven Rostedt To: Nicolas Pitre Cc: Ingo Molnar , Daniel Lezcano , Russell King - ARM Linux , Catalin Marinas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org Subject: Re: [PATCH v2 1/5] tracing: Do not do anything special with tracepoint_string when tracing is disabled Message-ID: <20140807223553.541eada9@gandalf.local.home> In-Reply-To: <1406318733-26754-2-git-send-email-nicolas.pitre@linaro.org> References: <1406318733-26754-1-git-send-email-nicolas.pitre@linaro.org> <1406318733-26754-2-git-send-email-nicolas.pitre@linaro.org> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Because ftrace_events.h is not included when config tracing is not enabled, I got error messages when compiling arm and arm64 without tracing enabled. This is the new patch I'm now testing that moves the tracepoint_string code to include/linux/tracepoint.h as well. -- Steve >>From 3c49b52b155d0f723792377e1a4480a0e7ca0ba2 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 25 Jul 2014 16:05:29 -0400 Subject: [PATCH] tracing: Do not do anything special with tracepoint_string when tracing is disabled When CONFIG_TRACING is not enabled, there's no reason to save the trace strings either by the linker or as a static variable that can be referenced later. Simply pass back the string that is given to tracepoint_string(). Had to move the define to include/linux/tracepoint.h so that it is still visible when CONFIG_TRACING is not set. Link: http://lkml.kernel.org/p/1406318733-26754-2-git-send-email-nicolas.pitre@linaro.org Suggested-by: Nicolas Pitre Signed-off-by: Steven Rostedt --- include/linux/ftrace_event.h | 34 ---------------------------------- include/linux/tracepoint.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 44 insertions(+), 34 deletions(-) diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index cff3106ffe2c..c9f619a2070f 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -574,40 +574,6 @@ do { \ __trace_printk(ip, fmt, ##args); \ } while (0) -/** - * tracepoint_string - register constant persistent string to trace system - * @str - a constant persistent string that will be referenced in tracepoints - * - * If constant strings are being used in tracepoints, it is faster and - * more efficient to just save the pointer to the string and reference - * that with a printf "%s" instead of saving the string in the ring buffer - * and wasting space and time. - * - * The problem with the above approach is that userspace tools that read - * the binary output of the trace buffers do not have access to the string. - * Instead they just show the address of the string which is not very - * useful to users. - * - * With tracepoint_string(), the string will be registered to the tracing - * system and exported to userspace via the debugfs/tracing/printk_formats - * file that maps the string address to the string text. This way userspace - * tools that read the binary buffers have a way to map the pointers to - * the ASCII strings they represent. - * - * The @str used must be a constant string and persistent as it would not - * make sense to show a string that no longer exists. But it is still fine - * to be used with modules, because when modules are unloaded, if they - * had tracepoints, the ring buffers are cleared too. As long as the string - * does not change during the life of the module, it is fine to use - * tracepoint_string() within a module. - */ -#define tracepoint_string(str) \ - ({ \ - static const char *___tp_str __tracepoint_string = str; \ - ___tp_str; \ - }) -#define __tracepoint_string __attribute__((section("__tracepoint_str"))) - #ifdef CONFIG_PERF_EVENTS struct perf_event; diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 2e2a5f7717e5..b1293f15f592 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -249,6 +249,50 @@ extern void syscall_unregfunc(void); #endif /* CONFIG_TRACEPOINTS */ +#ifdef CONFIG_TRACING +/** + * tracepoint_string - register constant persistent string to trace system + * @str - a constant persistent string that will be referenced in tracepoints + * + * If constant strings are being used in tracepoints, it is faster and + * more efficient to just save the pointer to the string and reference + * that with a printf "%s" instead of saving the string in the ring buffer + * and wasting space and time. + * + * The problem with the above approach is that userspace tools that read + * the binary output of the trace buffers do not have access to the string. + * Instead they just show the address of the string which is not very + * useful to users. + * + * With tracepoint_string(), the string will be registered to the tracing + * system and exported to userspace via the debugfs/tracing/printk_formats + * file that maps the string address to the string text. This way userspace + * tools that read the binary buffers have a way to map the pointers to + * the ASCII strings they represent. + * + * The @str used must be a constant string and persistent as it would not + * make sense to show a string that no longer exists. But it is still fine + * to be used with modules, because when modules are unloaded, if they + * had tracepoints, the ring buffers are cleared too. As long as the string + * does not change during the life of the module, it is fine to use + * tracepoint_string() within a module. + */ +#define tracepoint_string(str) \ + ({ \ + static const char *___tp_str __tracepoint_string = str; \ + ___tp_str; \ + }) +#define __tracepoint_string __attribute__((section("__tracepoint_str"))) +#else +/* + * tracepoint_string() is used to save the string address for userspace + * tracing tools. When tracing isn't configured, there's no need to save + * anything. + */ +# define tracepoint_string(str) str +# define __tracepoint_string +#endif + /* * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype * (void). "void" is a special value in a function prototype and can -- 2.0.1