[ltt-dev] [UST PATCH] Tracepoints: add noargs support

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

* Nils Carlson (nils.carlson at ericsson.com) wrote:
> Again, what do you think of UST_ prefixing the "externally visible"  
> macros?

I plan to make tracepoints more widely adoped that just UST. So I would
go for e.g.:

tracepoint(name, args)
register_tracepoint(name, ...)
unregister_tracepoint(name, ...)

And about the integration with TRACE_EVENT, we could also start it soon,
but I would keep it as a separate step. I plan to come up with a
different name than "trace event" because ours will be slightly
different than the in-kernel incarnation, and I don't want to confuse
users.

Thanks,

Mathieu

>
> /Nils
>
> On Mon, 11 Apr 2011, Mathieu Desnoyers wrote:
>
>> Add support for tracepoints receiving no argument as parameters. Copied
>> from Linux kernel:
>>
>> commit 38516ab59fbc5b3bb278cf5e1fe2867c70cff32e
>> Author: Steven Rostedt <srostedt at redhat.com>
>> Date:   Tue Apr 20 17:04:50 2010 -0400
>>
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
>> CC: Nils Carlson <nils.carlson at ericsson.com>
>> CC: Steven Rostedt <srostedt at redhat.com>
>> ---
>> include/ust/tracepoint.h |   25 +++++++++++++++++++++----
>> 1 file changed, 21 insertions(+), 4 deletions(-)
>>
>> Index: ust/include/ust/tracepoint.h
>> ===================================================================
>> --- ust.orig/include/ust/tracepoint.h
>> +++ ust/include/ust/tracepoint.h
>> @@ -175,10 +175,27 @@ static inline void tracepoint_update_pro
>> { }
>> #endif /* CONFIG_TRACEPOINTS */
>>
>> -#define DECLARE_TRACE(name, proto, args)			\
>> -	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),	\
>> -			PARAMS(void *__data, proto),		\
>> -			PARAMS(__data, args))
>> +/*
>> + * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
>> + * (void). "void" is a special value in a function prototype and can
>> + * not be combined with other arguments. Since the DECLARE_TRACE()
>> + * macro adds a data element at the beginning of the prototype,
>> + * we need a way to differentiate "(void *data, proto)" from
>> + * "(void *data, void)". The second prototype is invalid.
>> + *
>> + * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
>> + * and "void *__data" as the callback prototype.
>> + *
>> + * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
>> + * "void *__data, proto" as the callback prototype.
>> + */
>> +#define DECLARE_TRACE_NOARGS(name)					\
>> +		__DECLARE_TRACE(name, void, , void *__data, __data)
>> +
>> +#define DECLARE_TRACE(name, proto, args)				\
>> +		__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),	\
>> +				PARAMS(void *__data, proto),		\
>> +				PARAMS(__data, args))
>>
>> /*
>>  * Connect a probe to a tracepoint.
>>
>> -- 
>> Mathieu Desnoyers
>> Operating System Efficiency R&D Consultant
>> EfficiOS Inc.
>> http://www.efficios.com
>>

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com