[PATCH 0/3] tracing: introduce TRACE_EVENT_NONE and use it

[Yafang Shao]

In this patchset, I introduce a new macro TRACE_EVENT_NONE(), which will
define a tracepoint as a do-nothing inline function.
	#define TRACE_EVENT_NONE(name, proto)			\
		static inline void trace_##name(proto)		\
		{ }						\
		static inline bool trace_##name##_enabled(void)	\
		{						\
			return false;				\
		}

Let's take some example for why this macro is needed.

- sched
The tracepoints trace_sched_stat_{iowait, blocked, wait, sleep} should
be not exposed to user if CONFIG_SCHEDSTATS is not set.
We can place #ifdef in the kernel/sched/fair.c to fix it, but we don't want
to sprinkle #ifdef.
So with TRACE_EVENT_NONE(), we can fix it in include/trace/events/sched.h.

- rcu
When CONFIG_RCU_TRACE is not set, some rcu tracepoints are define as
do-nothing macro without validating arguments, that is not proper.
We should validate the arguments.

Yafang Shao (3):
  tracing: introduce TRACE_EVENT_NONE()
  sched/fair: do not expose some tracepoints to user if
    CONFIG_SCHEDSTATS is not set
  rcu: validate arguments for rcu tracepoints

 include/linux/tracepoint.h   |  8 +++++
 include/trace/define_trace.h |  4 +++
 include/trace/events/rcu.h   | 84 ++++++++++++++++++++++++++++----------------
 include/trace/events/sched.h | 14 ++++++++
 kernel/rcu/rcu.h             |  9 ++---
 kernel/rcu/tree.c            |  8 ++---
 6 files changed, 86 insertions(+), 41 deletions(-)

-- 
1.8.3.1