[for-next][PATCH 17/19] tracing: introduce TRACE_EVENT_NOP()

[Steven Rostedt]

From: Yafang Shao <laoar.shao@xxxxxxxxx>

Sometimes we want to define a tracepoint as a do-nothing function.
So I introduce TRACE_EVENT_NOP, DECLARE_EVENT_CLASS_NOP and
DEFINE_EVENT_NOP for this kind of usage.

Link: http://lkml.kernel.org/r/1553602391-11926-2-git-send-email-laoar.shao@xxxxxxxxx

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 include/linux/tracepoint.h   | 15 +++++++++++++++
 include/trace/define_trace.h |  8 ++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 9c3186578ce0..86b019aa2839 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -548,4 +548,19 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 
 #define TRACE_EVENT_PERF_PERM(event, expr...)
 
+#define DECLARE_EVENT_NOP(name, proto, args)				\
+	static inline void trace_##name(proto)				\
+	{ }								\
+	static inline bool trace_##name##_enabled(void)			\
+	{								\
+		return false;						\
+	}
+
+#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)	\
+	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
+
+#define DECLARE_EVENT_CLASS_NOP(name, proto, args, tstruct, assign, print)
+#define DEFINE_EVENT_NOP(template, name, proto, args)			\
+	DECLARE_EVENT_NOP(name, PARAMS(proto), PARAMS(args))
+
 #endif /* ifdef TRACE_EVENT (see note above) */
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index cb30c5532144..bd75f97867b9 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -46,6 +46,12 @@
 		assign, print, reg, unreg)			\
 	DEFINE_TRACE_FN(name, reg, unreg)
 
+#undef TRACE_EVENT_NOP
+#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)
+
+#undef DEFINE_EVENT_NOP
+#define DEFINE_EVENT_NOP(template, name, proto, args)
+
 #undef DEFINE_EVENT
 #define DEFINE_EVENT(template, name, proto, args) \
 	DEFINE_TRACE(name)
@@ -102,6 +108,8 @@
 #undef TRACE_EVENT_FN
 #undef TRACE_EVENT_FN_COND
 #undef TRACE_EVENT_CONDITION
+#undef TRACE_EVENT_NOP
+#undef DEFINE_EVENT_NOP
 #undef DECLARE_EVENT_CLASS
 #undef DEFINE_EVENT
 #undef DEFINE_EVENT_FN
-- 
2.20.1