tracing: Fix branch tracer header

Before patch:

  # tracer: branch
  #
  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
  #              | |       |          |         |
             <...>-2981  [000] 24008.872738: [  ok  ] trace_irq_handler_exit:irq_event_types.h:41
             <...>-2981  [000] 24008.872742: [  ok  ] note_interrupt:spurious.c:229
  ...

After patch:

  # tracer: branch
  #
  #           TASK-PID    CPU#    TIMESTAMP  CORRECT  FUNC:FILE:LINE
  #              | |       |          |         |       |
             <...>-2985  [000] 26329.142970: [  ok  ] slab_free:slub.c:1776
             <...>-2985  [000] 26329.142972: [  ok  ] trace_kmem_cache_free:kmem_event_types.h:191
  ...
Signed-off-by: NZhao Lei <zhaolei@cn.fujitsu.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <49E2F19A.3040006@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/trace_branch.c

@@ -155,6 +155,13 @@ static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 	return TRACE_TYPE_HANDLED;
 }
 
+static void branch_print_header(struct seq_file *s)
+{
+	seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
+		"  FUNC:FILE:LINE\n");
+	seq_puts(s, "#              | |       |          |         |   "
+		"    |\n");
+}
 
 static struct trace_event trace_branch_event = {
 	.type		= TRACE_BRANCH,
@@ -169,6 +176,7 @@ static struct tracer branch_trace __read_mostly =
 #ifdef CONFIG_FTRACE_SELFTEST
 	.selftest	= trace_selftest_startup_branch,
 #endif /* CONFIG_FTRACE_SELFTEST */
+	.print_header	= branch_print_header,
 };
 
 __init static int init_branch_tracer(void)