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>

3 files changed, 12 insertions, 2 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;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 5d2f07d6746c..8624b5041466 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -830,6 +830,7 @@ void ftrace_destroy_function_files(struct trace_array *tr);
 void ftrace_init_global_array_ops(struct trace_array *tr);
 void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func);
 void ftrace_reset_array_ops(struct trace_array *tr);
+int using_ftrace_ops_list_func(void);
 #else
 static inline int ftrace_trace_task(struct task_struct *task)
 {
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 21b320e5d163..5aa9a5b9b6e2 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -85,8 +85,12 @@ check_stack(unsigned long ip, unsigned long *stack)
 
         max_stack_size = this_size;
 
-        max_stack_trace.nr_entries      = 0;
-        max_stack_trace.skip            = 3;
+        max_stack_trace.nr_entries = 0;
+
+        if (using_ftrace_ops_list_func())
+                max_stack_trace.skip = 4;
+        else
+                max_stack_trace.skip = 3;
 
         save_stack_trace(&max_stack_trace);