tracing: introduce TRACE_EVENT_NOP()

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@gmail.com

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 15 insertions, 0 deletions

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) */