tracing/events: Add trace_define_common_fields()

Extract duplicate code. Also prepare for the later patch.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A8BAFB8.1010304@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_events.c

@@ -62,6 +62,28 @@ err:
 }
 EXPORT_SYMBOL_GPL(trace_define_field);
 
+#define __common_field(type, item)					\
+	ret = trace_define_field(call, #type, "common_" #item,		\
+				 offsetof(typeof(ent), item),		\
+				 sizeof(ent.item),			\
+				 is_signed_type(type));			\
+	if (ret)							\
+		return ret;
+
+int trace_define_common_fields(struct ftrace_event_call *call)
+{
+	int ret;
+	struct trace_entry ent;
+
+	__common_field(unsigned short, type);
+	__common_field(unsigned char, flags);
+	__common_field(unsigned char, preempt_count);
+	__common_field(int, pid);
+	__common_field(int, tgid);
+
+	return ret;
+}
+
 #ifdef CONFIG_MODULES
 
 static void trace_destroy_fields(struct ftrace_event_call *call)

kernel/trace/trace_export.c

@@ -189,11 +189,9 @@ ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
 	struct args field;						\
 	int ret;							\
 									\
-	__common_field(unsigned char, type, 0);				\
-	__common_field(unsigned char, flags, 0);			\
-	__common_field(unsigned char, preempt_count, 0);		\
-	__common_field(int, pid, 1);					\
-	__common_field(int, tgid, 1);					\
+	ret = trace_define_common_fields(event_call);			\
+	if (ret)							\
+		return ret;						\
 									\
 	tstruct;							\
 									\