Re: [PATCH] Fix tracing infrastructure to support multiple includes when defining CREATE_TRACE_POINTS

[Neil Horman <nhorman@tuxdriver.com>]

On Mon, Dec 07, 2009 at 03:04:42PM -0500, Steven Rostedt wrote:
> On Thu, 2009-12-03 at 14:35 -0500, Neil Horman wrote:
> 
> > Fix tracing infrastructure to allow multiple header files with TRACE_EVENTS to
> > be included with CREATE_TRACE_EVENTS defined
> > 
> > I've been workingon adding a few tracepoints to the network stack, and in so
> > doing it was convienient for me to add a second include file to
> > net/core/net-traces.c with TRACE_EVENTS defined in them.  net-traces.c defines
> > CREATE_TRACE_EVENTS, and during the build it was failing, complaining about
> > duplicate definitions of __tpstrtab_<name>.  I tracked down the bug to find that
> > define_trace.h redefined DECLARE_TRACE to be DEFINE_TRACE, so after the first
> > run through define_trace.h (which is included from skb.h, included in
> > net-trace.c first), the DECLARE_TRACE macro was left with an improper definition
> > to start a new cycle with the next header.
> > 
> > The fix I came up with was to make sure that DECLARE_TRACE was undefined at the
> > end of define_trace.h, and to add a conditional re-definition in tracepoint.h.
> > This places us back in the proper state to define a new set of tracepoints in a
> > subsequent header file.
> > 
> > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> > 
> 
> By itself, this patch breaks the build (for me). I take it that you
> converted the napi.h file to use TRACE_EVENT. Currently it uses a
> DECLARE_TRACE, which will break with this patch. We need a patch that
> removes that DECLARE_TRACE before we can apply this patch.
> 
Yes, I did that conversion, sorry, wasn't thinking about how that might affect
the build.  Given that converting to a TRACE_EVENT shouldn't be noticible to any
of the users of that tracepoint (it can still be hooked in an identical
fashion), I'd vote for just doing a monolitic patch.  please find that below.

Regards
Neil



Fix tracing infrastructure to allow multiple header files with TRACE_EVENTS to
be included with CREATE_TRACE_EVENTS defined

I've been workingon adding a few tracepoints to the network stack, and in so
doing it was convienient for me to add a second include file to
net/core/net-traces.c with TRACE_EVENTS defined in them.  net-traces.c defines
CREATE_TRACE_EVENTS, and during the build it was failing, complaining about
duplicate definitions of __tpstrtab_<name>.  I tracked down the bug to find that
define_trace.h redefined DECLARE_TRACE to be DEFINE_TRACE, so after the first
run through define_trace.h (which is included from skb.h, included in
net-trace.c first), the DECLARE_TRACE macro was left with an improper definition
to start a new cycle with the next header.

The fix I came up with was to make sure that DECLARE_TRACE was undefined at the
end of define_trace.h, and to add a conditional re-definition in tracepoint.h.
This places us back in the proper state to define a new set of tracepoints in a
subsequent header file.


Note this patch also converts the napi_poll tracepoint to a TRACE_EVENT.  This
is done so that the TRACE_EVENT fix doesn't break the build, and because its
rather pointless I think given the current tracing infrastructure to not have
napi_poll be an independent event.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>


linux/tracepoint.h   |   45 +++++++++++++++++++++++----------------------
trace/define_trace.h |    1 +
trace/events/napi.h  |   25 ++++++++++++++++++++++---
3 files changed, 46 insertions(+), 25 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 2aac8a8..311abbf 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -58,28 +58,6 @@ struct tracepoint {
 		rcu_read_unlock_sched_notrace();			\
 	} while (0)
 
-/*
- * Make sure the alignment of the structure in the __tracepoints section will
- * not add unwanted padding between the beginning of the section and the
- * structure. Force alignment to the same alignment as the section start.
- */
-#define DECLARE_TRACE(name, proto, args)				\
-	extern struct tracepoint __tracepoint_##name;			\
-	static inline void trace_##name(proto)				\
-	{								\
-		if (unlikely(__tracepoint_##name.state))		\
-			__DO_TRACE(&__tracepoint_##name,		\
-				TP_PROTO(proto), TP_ARGS(args));	\
-	}								\
-	static inline int register_trace_##name(void (*probe)(proto))	\
-	{								\
-		return tracepoint_probe_register(#name, (void *)probe);	\
-	}								\
-	static inline int unregister_trace_##name(void (*probe)(proto))	\
-	{								\
-		return tracepoint_probe_unregister(#name, (void *)probe);\
-	}
-
 
 #define DEFINE_TRACE_FN(name, reg, unreg)				\
 	static const char __tpstrtab_##name[]				\
@@ -173,6 +151,29 @@ static inline void tracepoint_synchronize_unregister(void)
  *  trace event headers under one "CREATE_TRACE_POINTS" the first include
  *  will override the TRACE_EVENT and break the second include.
  */
+#if defined(CONFIG_TRACEPOINTS) && !defined(DECLARE_TRACE)
+/*
+ * Make sure the alignment of the structure in the __tracepoints section will
+ * not add unwanted padding between the beginning of the section and the
+ * structure. Force alignment to the same alignment as the section start.
+ */
+#define DECLARE_TRACE(name, proto, args)                                \
+	extern struct tracepoint __tracepoint_##name;                   \
+	static inline void trace_##name(proto)                          \
+	{                                                               \
+		if (unlikely(__tracepoint_##name.state))                \
+			__DO_TRACE(&__tracepoint_##name,                \
+				TP_PROTO(proto), TP_ARGS(args));        \
+	}                                                               \
+	static inline int register_trace_##name(void (*probe)(proto))   \
+	{                                                               \
+		return tracepoint_probe_register(#name, (void *)probe); \
+	}                                                               \
+	static inline int unregister_trace_##name(void (*probe)(proto)) \
+	{                                                               \
+		return tracepoint_probe_unregister(#name, (void *)probe);\
+	}
+#endif
 
 #ifndef TRACE_EVENT
 /*
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index 2a4b3bf..a3e0095 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -64,6 +64,7 @@
 #undef TRACE_EVENT
 #undef TRACE_EVENT_FN
 #undef TRACE_HEADER_MULTI_READ
+#undef DECLARE_TRACE
 
 /* Only undef what we defined in this file */
 #ifdef UNDEF_TRACE_INCLUDE_FILE
diff --git a/include/trace/events/napi.h b/include/trace/events/napi.h
index a8989c4..25a1709 100644
--- a/include/trace/events/napi.h
+++ b/include/trace/events/napi.h
@@ -1,11 +1,30 @@
-#ifndef _TRACE_NAPI_H_
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM napi
+
+#if !defined(_TRACE_NAPI_H_) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_NAPI_H_
 
 #include <linux/netdevice.h>
 #include <linux/tracepoint.h>
 
-DECLARE_TRACE(napi_poll,
+TRACE_EVENT(napi_poll,
+
 	TP_PROTO(struct napi_struct *napi),
-	TP_ARGS(napi));
+
+	TP_ARGS(napi),
+
+	TP_STRUCT__entry(
+		__field(        struct napi_struct *,	napi)
+        ),
+
+        TP_fast_assign(
+                __entry->napi = napi;
+        ),
+
+        TP_printk("napi poll on napi struct %p for device %s",
+		__entry->napi, __entry->napi->dev->name)
+);
 
 #endif
+
+#include <trace/define_trace.h>