[lttng-dev] notrace missing in lttng-ust

[Mathieu Desnoyers]

* Woegerer, Paul (Paul_Woegerer at mentor.com) wrote:
> Hi Mathieu,
>
> libust 0.x uses notrace (__attribute__((no_instrument_function)) for all  
> functions that are involved in event emitting.
>
> For example:
> ./libust/marker.c:122:notrace void __ust_marker_empty_function(const  
> struct ust_marker *mdata,
> ./libust/marker.c:137:notrace void ust_marker_probe_cb(const struct  
> ust_marker *mdata,
> ./libust/marker.c:197:static notrace void  
> ust_marker_probe_cb_noarg(const struct ust_marker *mdata,
>
> I just realized that this is no more the case for lttng-ust.
> Was it a conscious decision not to use notrace for LTTng 2.0 lttng-ust,  
> or is it just missing ?

just missing. only needed for -finstrument-functions.

>
> I would like to have notrace also in lttng-ust, at least for the  
> _DECLARE_TRACEPOINT macro in tracepoint.h.

I guess the probes generated by ust-tracepoint-event.h would need that
too. A patch that adds those noinline everywhere where it's needed
(hint: all functions called on the tracing patch within public headers
of lttng-ust 2.0 would be a good start). Please test the patch by
tracing a program automatically instrumented by -finstrument-functions
and see if things blow up.

Thanks,

Mathieu

> Like this for example:
>
> diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
> index 5bab476..71665dc 100644
> --- a/include/lttng/tracepoint.h
> +++ b/include/lttng/tracepoint.h
> @@ -137,6 +137,7 @@ extern "C" {
>
>  #define _DECLARE_TRACEPOINT(_provider, _name, ...)     \
>  extern struct tracepoint __tracepoint_##_provider##___##_name;           
>   \
> +static inline void  
> __tracepoint_cb_##_provider##___##_name(_TP_ARGS_PROTO(__VA_ARGS__))  
> __attribute__ ((no_instrument_function));    \
>  static inline void  
> __tracepoint_cb_##_provider##___##_name(_TP_ARGS_PROTO(__VA_ARGS__)) \
>  {                                            \
>      struct tracepoint_probe *__tp_probe;                        \
> @@ -158,12 +159,16 @@ end:     \
>      tp_rcu_read_unlock_bp();                            \
>  }                                            \
>  static inline void __tracepoint_register_##_provider##___##_name(char  
> *name,        \
> +        void (*func)(void), void *data) __attribute__  
> ((no_instrument_function));    \
> +static inline void __tracepoint_register_##_provider##___##_name(char  
> *name,        \
>          void (*func)(void), void *data) \
>  {                                            \
>      __tracepoint_probe_register(name, func, data,     \
>          __tracepoint_##_provider##___##_name.signature); \
>  }                                            \
>  static inline void __tracepoint_unregister_##_provider##___##_name(char 
> *name,        \
> +        void (*func)(void), void *data) __attribute__  
> ((no_instrument_function));    \
> +static inline void __tracepoint_unregister_##_provider##___##_name(char  
> *name,        \
>          void (*func)(void), void *data) \
>  {                                            \
>      __tracepoint_probe_unregister(name, func, data); \
>
> Greetings,
> Paul
>
> -- 
> Paul Woegerer | SW Development Engineer
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com