linux-kernel - [PATCH 04/13] jump label v9: tracepoint support

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Date:	Wed, 9 Jun 2010 17:39:04 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, mathieu.desnoyers@...ymtl.ca, hpa@...or.com,
	tglx@...utronix.de, rostedt@...dmis.org, andi@...stfloor.org,
	roland@...hat.com, rth@...hat.com, mhiramat@...hat.com,
	fweisbec@...il.com, avi@...hat.com, davem@...emloft.net,
	vgoyal@...hat.com, sam@...nborg.org
Subject: [PATCH 04/13] jump label v9: tracepoint support

Make use of the jump label infrastructure for tracepoints.

Signed-off-by: Jason Baron <jbaron@...hat.com>
---
 include/linux/tracepoint.h |    8 ++++++--
 kernel/tracepoint.c        |    8 ++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 9a59d1f..883df16 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -16,6 +16,7 @@
 
 #include <linux/types.h>
 #include <linux/rcupdate.h>
+#include <linux/jump_label.h>
 
 struct module;
 struct tracepoint;
@@ -144,7 +145,9 @@ static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 	extern struct tracepoint __tracepoint_##name;			\
 	static inline void trace_##name(proto)				\
 	{								\
-		if (unlikely(__tracepoint_##name.state))		\
+		JUMP_LABEL(&__tracepoint_##name, do_trace, __tracepoint_##name.state);\
+		return;							\
+do_trace:								\
 			__DO_TRACE(&__tracepoint_##name,		\
 				TP_PROTO(data_proto),			\
 				TP_ARGS(data_args));			\
@@ -171,7 +174,8 @@ static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 	__attribute__((section("__tracepoints_strings"))) = #name;	\
 	struct tracepoint __tracepoint_##name				\
 	__attribute__((section("__tracepoints"), aligned(32))) =	\
-		{ __tpstrtab_##name, 0, reg, unreg, NULL }
+		{ __tpstrtab_##name, 0, reg, unreg, NULL };		\
+	DEFINE_JUMP_LABEL(name);
 
 #define DEFINE_TRACE(name)						\
 	DEFINE_TRACE_FN(name, NULL, NULL);
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index c77f3ec..b16d873 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -25,6 +25,7 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/jump_label.h>
 
 extern struct tracepoint __start___tracepoints[];
 extern struct tracepoint __stop___tracepoints[];
@@ -263,6 +264,10 @@ static void set_tracepoint(struct tracepoint_entry **entry,
 	 * is used.
 	 */
 	rcu_assign_pointer(elem->funcs, (*entry)->funcs);
+	if (!elem->state && active)
+		enable_jump_label(elem->name);
+	if (elem->state && !active)
+		disable_jump_label(elem->name);
 	elem->state = active;
 }
 
@@ -277,6 +282,9 @@ static void disable_tracepoint(struct tracepoint *elem)
 	if (elem->unregfunc && elem->state)
 		elem->unregfunc();
 
+	if (elem->state)
+		disable_jump_label(elem->name);
+
 	elem->state = 0;
 	rcu_assign_pointer(elem->funcs, NULL);
 }
-- 
1.7.1

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