Commit c1df1bd2 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Ingo Molnar
Browse files

markers: auto enable tracepoints (new API : trace_mark_tp()) 



Impact: new API

Add a new API trace_mark_tp(), which declares a marker within a
tracepoint probe. When the marker is activated, the tracepoint is
automatically enabled.

No branch test is used at the marker site, because it would be a
duplicate of the branch already present in the tracepoint.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a419246a

include/linux/marker.h

+44 −1
Original line number Diff line number Diff line
@@ -49,6 +49,8 @@ struct marker { 
	void (*call)(const struct marker *mdata, void *call_private, ...);

	struct marker_probe_closure single;

	struct marker_probe_closure *multi;

	const char *tp_name;	/* Optional tracepoint name */

	void *tp_cb;		/* Optional tracepoint callback */

} __attribute__((aligned(8)));



#ifdef CONFIG_MARKERS
@@ -73,7 +75,7 @@ struct marker { 
		__attribute__((section("__markers"), aligned(8))) =	\

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

		0, 0, marker_probe_cb,					\

		{ __mark_empty_function, NULL}, NULL };			\

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

		__mark_check_format(format, ## args);			\

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

			(*__mark_##name.call)				\
@@ -81,11 +83,38 @@ struct marker { 
		}							\

	} while (0)



#define __trace_mark_tp(name, call_private, tp_name, tp_cb, format, args...) \

	do {								\

		void __check_tp_type(void)				\

		{							\

			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 };\

		__mark_check_format(format, ## args);			\

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

					## args);			\

	} while (0)



extern void marker_update_probe_range(struct marker *begin,

	struct marker *end);

#else /* !CONFIG_MARKERS */

#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...) \

	do {								\

		void __check_tp_type(void)				\

		{							\

			register_trace_##tp_name(tp_cb);		\

		}							\

		__mark_check_format(format, ## args);			\

	} while (0)

static inline void marker_update_probe_range(struct marker *begin,

	struct marker *end)

{ }
@@ -117,6 +146,20 @@ static inline void marker_update_probe_range(struct marker *begin, 
#define _trace_mark(name, format, args...) \

	__trace_mark(1, name, NULL, format, ## args)



/**

 * trace_mark_tp - Marker in a tracepoint callback

 * @name: marker name, not quoted.

 * @tp_name: tracepoint name, not quoted.

 * @tp_cb: tracepoint callback. Should have an associated global symbol so it

 *         is not optimized away by the compiler (should not be static).

 * @format: format string

 * @args...: variable argument list

 *

 * Places a marker in a tracepoint callback.

 */

#define trace_mark_tp(name, tp_name, tp_cb, format, args...)	\

	__trace_mark_tp(name, NULL, tp_name, tp_cb, format, ## args)



/**

 * MARK_NOARGS - Format string for a marker with no argument.

 */

init/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -808,6 +808,7 @@ config TRACEPOINTS 


config MARKERS

	bool "Activate markers"

	depends on TRACEPOINTS

	help

	  Place an empty function call at each marker site. Can be

	  dynamically changed for a probe function.

kernel/marker.c

+51 −2
Original line number Diff line number Diff line
@@ -479,7 +479,7 @@ static int marker_set_format(struct marker_entry *entry, const char *format) 
static int set_marker(struct marker_entry *entry, struct marker *elem,

		int active)

{

	int ret;

	int ret = 0;

	WARN_ON(strcmp(entry->name, elem->name) != 0);



	if (entry->format) {
@@ -531,9 +531,40 @@ static int set_marker(struct marker_entry *entry, struct marker *elem, 
	 */

	smp_wmb();

	elem->ptype = entry->ptype;



	if (elem->tp_name && (active ^ elem->state)) {

		WARN_ON(!elem->tp_cb);

		/*

		 * It is ok to directly call the probe registration because type

		 * checking has been done in the __trace_mark_tp() macro.

		 */



		if (active) {

			/*

			 * try_module_get should always succeed because we hold

			 * lock_module() to get the tp_cb address.

			 */

			ret = try_module_get(__module_text_address(

				(unsigned long)elem->tp_cb));

			BUG_ON(!ret);

			ret = tracepoint_probe_register_noupdate(

				elem->tp_name,

				elem->tp_cb);

		} else {

			ret = tracepoint_probe_unregister_noupdate(

				elem->tp_name,

				elem->tp_cb);

			/*

			 * tracepoint_probe_update_all() must be called

			 * before the module containing tp_cb is unloaded.

			 */

			module_put(__module_text_address(

				(unsigned long)elem->tp_cb));

		}

	}

	elem->state = active;



	return 0;

	return ret;

}



/*
@@ -544,7 +575,24 @@ static int set_marker(struct marker_entry *entry, struct marker *elem, 
 */

static void disable_marker(struct marker *elem)

{

	int ret;



	/* leave "call" as is. It is known statically. */

	if (elem->tp_name && elem->state) {

		WARN_ON(!elem->tp_cb);

		/*

		 * It is ok to directly call the probe registration because type

		 * checking has been done in the __trace_mark_tp() macro.

		 */

		ret = tracepoint_probe_unregister_noupdate(elem->tp_name,

			elem->tp_cb);

		WARN_ON(ret);

		/*

		 * tracepoint_probe_update_all() must be called

		 * before the module containing tp_cb is unloaded.

		 */

		module_put(__module_text_address((unsigned long)elem->tp_cb));

	}

	elem->state = 0;

	elem->single.func = __mark_empty_function;

	/* Update the function before setting the ptype */
@@ -608,6 +656,7 @@ static void marker_update_probes(void) 
	marker_update_probe_range(__start___markers, __stop___markers);

	/* Markers in modules. */

	module_update_markers();

	tracepoint_probe_update_all();

}



/**

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