From: Steven Rostedt <srostedt@redhat.com>
Date: Wed, 26 Aug 2009 04:32:37 +0000 (-0400)
Subject: tracing: add comments to explain TRACE_EVENT out of protection
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7cb2e3ee2aeec5b83ecadba929a2dc575dd4008f;p=linux-beck.git

tracing: add comments to explain TRACE_EVENT out of protection

The commit:
  commit 5ac35daa9343936038a3c9c4f4d6d3fe6a2a7bd8
  Author: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
  tracing/events: fix the include file dependencies

Moved the TRACE_EVENT out of the ifdef protection of tracepoints.h
but uses the define of TRACE_EVENT itself as protection. This patch
adds comments to explain why.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 81709854f7ab..0341f2e2698a 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -180,7 +180,15 @@ static inline void tracepoint_synchronize_unregister(void)
 }
 
 #define PARAMS(args...) args
-#endif
+
+#endif /* _LINUX_TRACEPOINT_H */
+
+/*
+ * Note: we keep the TRACE_EVENT outside the include file ifdef protection.
+ *  This is due to the way trace events work. If a file includes two
+ *  trace event headers under one "CREATE_TRACE_POINTS" the first include
+ *  will override the TRACE_EVENT and break the second include.
+ */
 
 #ifndef TRACE_EVENT
 /*
@@ -287,4 +295,5 @@ static inline void tracepoint_synchronize_unregister(void)
 
 #define TRACE_EVENT(name, proto, args, struct, assign, print)	\
 	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
-#endif
+
+#endif /* ifdef TRACE_EVENT (see note above) */