Commit a0bca6a5 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Ingo Molnar
Browse files

markers: create DEFINE_MARKER and GET_MARKER (new API) 



Impact: new API.

Allow markers to be used only for declaration, without function call
associated. Useful to create specialized probes.

The problem we had is that two function calls were required when one
wanted to put a marker in a tracepoint probe. Now the marker can be used
simply for trace data type declaration, leaving the trace write work
within the tracepoint probe without any additional function call.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c1df1bd2

Documentation/markers.txt

+14 −0
Original line number Diff line number Diff line
@@ -70,6 +70,20 @@ a printk warning which identifies the inconsistency: 


"Format mismatch for probe probe_name (format), marker (format)"



Another way to use markers is to simply define the marker without generating any

function call to actually call into the marker. This is useful in combination

with tracepoint probes in a scheme like this :



void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk);



DEFINE_MARKER_TP(marker_eventname, tracepoint_name, probe_tracepoint_name,

	"arg1 %u pid %d");



notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk)

{

	struct marker *marker = &GET_MARKER(kernel_irq_entry);

	/* write data to trace buffers ... */

}



* Probe / marker example

include/linux/marker.h

+23 −16
Original line number Diff line number Diff line
@@ -55,6 +55,22 @@ struct marker { 


#ifdef CONFIG_MARKERS



#define _DEFINE_MARKER(name, tp_name_str, tp_cb, format)		\

		static const char __mstrtab_##name[]			\

		__attribute__((section("__markers_strings")))		\

		= #name "\0" format;					\

		static struct marker __mark_##name			\

		__attribute__((section("__markers"), aligned(8))) =	\

		{ __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],	\

		  0, 0, marker_probe_cb, { __mark_empty_function, NULL},\

		  NULL, tp_name_str, tp_cb }



#define DEFINE_MARKER(name, format)					\

		_DEFINE_MARKER(name, NULL, NULL, format)



#define DEFINE_MARKER_TP(name, tp_name, tp_cb, format)			\

		_DEFINE_MARKER(name, #tp_name, tp_cb, format)



/*

 * Note : the empty asm volatile with read constraint is used here instead of a

 * "used" attribute to fix a gcc 4.1.x bug.
@@ -68,14 +84,7 @@ struct marker { 
 */

#define __trace_mark(generic, name, call_private, format, args...)	\

	do {								\

		static const char __mstrtab_##name[]			\

		__attribute__((section("__markers_strings")))		\

		= #name "\0" format;					\

		static struct marker __mark_##name			\

		__attribute__((section("__markers"), aligned(8))) =	\

		{ __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],	\

		0, 0, marker_probe_cb,					\

		{ __mark_empty_function, NULL}, NULL, NULL, NULL };	\

		DEFINE_MARKER(name, format);				\

		__mark_check_format(format, ## args);			\

		if (unlikely(__mark_##name.state)) {			\

			(*__mark_##name.call)				\
@@ -89,14 +98,7 @@ struct marker { 
		{							\

			register_trace_##tp_name(tp_cb);		\

		}							\

		static const char __mstrtab_##name[]			\

		__attribute__((section("__markers_strings")))		\

		= #name "\0" format;					\

		static struct marker __mark_##name			\

		__attribute__((section("__markers"), aligned(8))) =	\

		{ __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],	\

		0, 0, marker_probe_cb,					\

		{ __mark_empty_function, NULL}, NULL, #tp_name, tp_cb };\

		DEFINE_MARKER_TP(name, tp_name, tp_cb, format);		\

		__mark_check_format(format, ## args);			\

		(*__mark_##name.call)(&__mark_##name, call_private,	\

					## args);			\
@@ -104,7 +106,11 @@ struct marker { 


extern void marker_update_probe_range(struct marker *begin,

	struct marker *end);



#define GET_MARKER(name)	(__mark_##name)



#else /* !CONFIG_MARKERS */

#define DEFINE_MARKER(name, tp_name, tp_cb, format)

#define __trace_mark(generic, name, call_private, format, args...) \

		__mark_check_format(format, ## args)

#define __trace_mark_tp(name, call_private, tp_name, tp_cb, format, args...) \
@@ -118,6 +124,7 @@ extern void marker_update_probe_range(struct marker *begin, 
static inline void marker_update_probe_range(struct marker *begin,

	struct marker *end)

{ }

#define GET_MARKER(name)

#endif /* CONFIG_MARKERS */



/**

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