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authorSteven Rostedt <rostedt@goodmis.org>2014-07-25 16:05:29 -0400
committerSteven Rostedt <rostedt@goodmis.org>2014-08-07 20:39:36 -0400
commit3c49b52b155d0f723792377e1a4480a0e7ca0ba2 (patch)
tree651052ab8141bb7b0a28d23ea02624727632f311 /include/linux/ftrace_event.h
parent19583ca584d6f574384e17fe7613dfaeadcdc4a6 (diff)
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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 <nico@linaro.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/ftrace_event.h')
-rw-r--r--include/linux/ftrace_event.h34
1 files changed, 0 insertions, 34 deletions
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index cff3106..c9f619a 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;
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