From 3c49b52b155d0f723792377e1a4480a0e7ca0ba2 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 25 Jul 2014 16:05:29 -0400 Subject: 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 ---------------------------------- 1 file changed, 34 deletions(-) (limited to 'include/linux/ftrace_event.h') 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; -- cgit v1.2.3