Re: TRACE_EVENT_ABI ?

[Steven Rostedt]

On Mon, 2009-09-21 at 15:28 +0200, Arjan van de Ven wrote:
> On Mon, 21 Sep 2009 09:26:41 -0400 (EDT)
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> 
> > 
> > [ Resending due to wrong SMTP server ]
> > 
> > 
> > On Mon, 21 Sep 2009, Arjan van de Ven wrote:
> > 
> > > Hi,
> > > 
> > > Ingo suggested to make a TRACE_EVENT_ABI, which is equivalent in
> > > implementation to TRACE_EVENT, except that it signals a stable
> > > interface.
> > > 
> > > In trying to implement this I'm running into a wall where
> > > TRACE_EVENT keeps being defined in many different ways all over the
> > > place, making this a really nasty hack to make it just an alias.
> > > 
> > > Do you have any clever ideas on how to make this an alias without
> > > fouling up the whole tracing system?
> > > 
> > 
> > I don't know what you've done so far, but can't you simply in
> > tracepoint.h define:
> > 
> > #define TRACE_EVENT_API(a,b,c,d,e) TRACE_EVENT(a,b,c,d,e)
> 
> unfortunately, due to the preprocessor trickery around TRACE_EVENT this
> completely barfs.

I forgot to tell you about PARAMS.

This patch compiled for me;

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 63a3f7a..9a983d6 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -280,6 +280,10 @@ static inline void tracepoint_synchronize_unregister(void)
  * TRACE_EVENT_FN to perform any (un)registration work.
  */
 
+#define TRACE_EVENT_API(name, proto, args, tstruct, assign, print)	\
+	TRACE_EVENT(name, PARAMS(proto), PARAMS(args),			\
+		    PARAMS(tstruct), PARAMS(assign), PARAMS(print))
+
 #define TRACE_EVENT(name, proto, args, struct, assign, print)	\
 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
 #define TRACE_EVENT_FN(name, proto, args, struct,		\
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index b48f1ad..0ee1eb6 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -149,7 +149,7 @@ TRACE_EVENT(sched_wakeup_new,
  * (NOTE: the 'rq' argument is not used by generic trace events,
  *        but used by the latency tracer plugin. )
  */
-TRACE_EVENT(sched_switch,
+TRACE_EVENT_API(sched_switch,
 
 	TP_PROTO(struct rq *rq, struct task_struct *prev,
 		 struct task_struct *next),


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