tracing/core: Make the stack entry helpers global

Make the stacktrace event insertion helpers globals.
This has two effects:

- Prepare for moving the sched events insertion helpers to
  the sched switch tracer file.
- Move some ifdef outside function definitions

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c7e9273..116524d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -489,9 +489,31 @@
 void update_max_tr_single(struct trace_array *tr,
 			  struct task_struct *tsk, int cpu);
 
-void __trace_stack(struct trace_array *tr,
-		   unsigned long flags,
-		   int skip, int pc);
+#ifdef CONFIG_STACKTRACE
+void ftrace_trace_stack(struct trace_array *tr, unsigned long flags,
+			int skip, int pc);
+
+void ftrace_trace_userstack(struct trace_array *tr, unsigned long flags,
+			    int pc);
+
+void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
+		   int pc);
+#else
+static inline void ftrace_trace_stack(struct trace_array *tr,
+				      unsigned long flags, int skip, int pc)
+{
+}
+
+static inline void ftrace_trace_userstack(struct trace_array *tr,
+					  unsigned long flags, int pc)
+{
+}
+
+static inline void __trace_stack(struct trace_array *tr, unsigned long flags,
+				 int skip, int pc)
+{
+}
+#endif /* CONFIG_STACKTRACE */
 
 extern cycle_t ftrace_now(int cpu);