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Subject[PATCH] Fix tracing infrastructure to support multiple includes when defining CREATE_TRACE_POINTS
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. Not sure if theres a better way to handle this, but
this worked well for me, allowing me to include multiple headers with
TRACE_EVENT macros in a c file with CREATE_TRACE_POINTS defined.

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


linux/tracepoint.h | 18 ++++++++++++++++++
trace/define_trace.h | 1 +
2 files changed, 19 insertions(+)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 2aac8a8..562d8ba 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -173,6 +173,24 @@ 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.
*/
+#ifndef DECLARE_TRACE
+#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

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