linux-kernel - [RFC PATCH] Tracepoint: introduce tracepoint() API

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Message-ID: <20111117205053.GA26484@Krystal>
Date:	Thu, 17 Nov 2011 15:50:53 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Christoph Lameter <cl@...ux-foundation.org>,
	rostedt <rostedt@...dmis.org>
Subject: [RFC PATCH] Tracepoint: introduce tracepoint() API

Introduce:

  tracepoint(event_name, arg1, arg2, ...)

while keeping the old tracepoint API in place, e.g.:

  trace_event_name(arg1, arg2, ...)

This allows skipping parameter side-effects (pointer dereference,
function calls, ...) when the tracepoint is not dynamically activated.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
---
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index d530a44..c9c73f7 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -107,6 +107,12 @@ void tracepoint_update_probe_range(struct tracepoint * const *begin,
 
 #ifdef CONFIG_TRACEPOINTS
 
+#define tracepoint(name, args...)					\
+	do {								\
+		if (static_branch(&__tracepoint_##name.key))		\
+			__trace_##name(args);				\
+	} while (0)
+
 /*
  * it_func[0] is never NULL because there is at least one element in the array
  * when the array itself is non NULL.
@@ -144,13 +150,17 @@ void tracepoint_update_probe_range(struct tracepoint * const *begin,
  */
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args)	\
 	extern struct tracepoint __tracepoint_##name;			\
+	static inline void __trace_##name(proto)			\
+	{								\
+		__DO_TRACE(&__tracepoint_##name,			\
+			TP_PROTO(data_proto),				\
+			TP_ARGS(data_args),				\
+			TP_CONDITION(cond));				\
+	}								\
 	static inline void trace_##name(proto)				\
 	{								\
 		if (static_branch(&__tracepoint_##name.key))		\
-			__DO_TRACE(&__tracepoint_##name,		\
-				TP_PROTO(data_proto),			\
-				TP_ARGS(data_args),			\
-				TP_CONDITION(cond));			\
+			__trace_##name(args);				\
 	}								\
 	static inline int						\
 	register_trace_##name(void (*probe)(data_proto), void *data)	\
@@ -193,7 +203,12 @@ void tracepoint_update_probe_range(struct tracepoint * const *begin,
 	EXPORT_SYMBOL(__tracepoint_##name)
 
 #else /* !CONFIG_TRACEPOINTS */
+
+#define tracepoint(name, args...)	__trace_##name(args)
+
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args)	\
+	static inline void __trace_##name(proto)			\
+	{ }								\
 	static inline void trace_##name(proto)				\
 	{ }								\
 	static inline int						\

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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