ftrace_graph_get_ret_stack
ret_stack = ftrace_graph_get_ret_stack(task, *graph);
ret_stack = ftrace_graph_get_ret_stack(current, 0);
WARN_ON(ftrace_graph_get_ret_stack(current, 1));
ret_stack = ftrace_graph_get_ret_stack(current,
ret_stack = ftrace_graph_get_ret_stack(t,
ret_stack = ftrace_graph_get_ret_stack(tsk, graph);
ftrace_graph_get_ret_stack(struct task_struct *task, int skip);