tracing/stack_trace: Skip 4 instead of 3 when using ftrace_ops_list_func

When using ftrace_ops_list_func, we should skip 4 instead of 3,
to avoid ftrace_call+0x5/0xb appearing in the stack trace:

        Depth    Size   Location    (110 entries)
        -----    ----   --------
  0)     2956       0   update_curr+0xe/0x1e0
  1)     2956      68   ftrace_call+0x5/0xb
  2)     2888      92   enqueue_entity+0x53/0xe80
  3)     2796      80   enqueue_task_fair+0x47/0x7e0
  4)     2716      28   enqueue_task+0x45/0x70
  5)     2688      12   activate_task+0x22/0x30

Add a function using_ftrace_ops_list_func() to test for this while keeping
ftrace_ops_list_func to remain static.

Link: http://lkml.kernel.org/p/1398006644-5935-2-git-send-email-wangjiaxing@insigma.com.cn

Signed-off-by: Jiaxing Wang <wangjiaxing@insigma.com.cn>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 846888ea2ba4..3cfeb66bda67 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -313,6 +313,11 @@ static void update_ftrace_function(void)
 	ftrace_trace_function = func;
 }
 
+int using_ftrace_ops_list_func(void)
+{
+	return ftrace_trace_function == ftrace_ops_list_func;
+}
+
 static void add_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops)
 {
 	ops->next = *list;