x86, ftrace: call trace->open() before stopping tracing; add trace->print_header()

Index: ftrace/kernel/trace/trace.c
===================================================================
@@ -2298,7 +2298,9 @@
 			seq_printf(m, "# tracer: %s\n", iter->trace->name);
 			seq_puts(m, "#\n");
 		}
-		if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
+		if (iter->trace && iter->trace->print_header)
+			iter->trace->print_header(m);
+		else if (iter->iter_flags & TRACE_FILE_LAT_FMT) {
 			/* print nothing if the buffers are empty */
 			if (trace_empty(iter))
 				return 0;

@@ -2350,6 +2352,10 @@
 	iter->trace = current_trace;
 	iter->pos = -1;
 
+	/* Notify the tracer early; before we stop tracing. */
+	if (iter->trace && iter->trace->open)
+			iter->trace->open(iter);
+
 	/* Annotate start of buffers if we had overruns */
 	if (ring_buffer_overruns(iter->tr->buffer))
 		iter->iter_flags |= TRACE_FILE_ANNOTATE;

@@ -2375,9 +2381,6 @@
 	/* stop the trace while dumping */
 	tracing_stop();
 
-	if (iter->trace && iter->trace->open)
-			iter->trace->open(iter);
-
 	mutex_unlock(&trace_types_lock);
 
  out:

Index: ftrace/kernel/trace/trace.h
===================================================================
@@ -311,6 +311,7 @@
 	int			(*selftest)(struct tracer *trace,
 					    struct trace_array *tr);
 #endif
+	void			(*print_header)(struct seq_file *m);
 	enum print_line_t	(*print_line)(struct trace_iterator *iter);
 	/* If you handled the flag setting, return 0 */
 	int			(*set_flag)(u32 old_flags, u32 bit, int set);