Messages in this thread | | | Date | Mon, 25 Mar 2019 22:17:45 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 0/3] tracing: introduce TRACE_EVENT_NONE and use it |
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On Tue, 26 Mar 2019 09:40:04 +0800 Yafang Shao <laoar.shao@gmail.com> wrote:
> 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; \ > } >
BTW, I prefer a name of TRACE_EVENT_DISABLED()
Which shows that it is disabled, or TRACE_EVENT_UNDEF(), or TRACE_EVENT_NOP(). Something that states it is turned off. When I first saw NONE() I thought it was another attempt to introduce zero parameter trace events.
> 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.
But you still sprinkle #ifdef in the header, but the part I don't like is the need to duplicate the prototypes and the like.
> 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 >
See my reply in the next patch.
-- Steve
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