if (likely(disabled == 1)) {
                pc = preempt_count();
+               trace_function(tr, data, ip, parent_ip, flags, pc);
                /*
                 * skip over 5 funcs:
                 *    __ftrace_trace_stack,
        .func = function_trace_call,
 };
 
-void tracing_start_function_trace(void)
-{
-       ftrace_function_enabled = 0;
-
-       if (trace_flags & TRACE_ITER_PREEMPTONLY)
-               trace_ops.func = function_trace_call_preempt_only;
-       else
-               trace_ops.func = function_trace_call;
-
-       register_ftrace_function(&trace_ops);
-       ftrace_function_enabled = 1;
-}
-
-void tracing_stop_function_trace(void)
-{
-       ftrace_function_enabled = 0;
-       unregister_ftrace_function(&trace_ops);
-}
 static struct ftrace_ops trace_stack_ops __read_mostly =
 {
        .func = function_stack_trace_call,
        .opts = func_opts
 };
 
+void tracing_start_function_trace(void)
+{
+       ftrace_function_enabled = 0;
+
+       if (trace_flags & TRACE_ITER_PREEMPTONLY)
+               trace_ops.func = function_trace_call_preempt_only;
+       else
+               trace_ops.func = function_trace_call;
+
+       if (func_flags.val & TRACE_FUNC_OPT_STACK)
+               register_ftrace_function(&trace_stack_ops);
+       else
+               register_ftrace_function(&trace_ops);
+
+       ftrace_function_enabled = 1;
+}
+
+void tracing_stop_function_trace(void)
+{
+       ftrace_function_enabled = 0;
+       /* OK if they are not registered */
+       unregister_ftrace_function(&trace_stack_ops);
+       unregister_ftrace_function(&trace_ops);
+}
+
 static int func_set_flag(u32 old_flags, u32 bit, int set)
 {
        if (bit == TRACE_FUNC_OPT_STACK) {
                if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
                        return 0;
 
-               if (set)
+               if (set) {
+                       unregister_ftrace_function(&trace_ops);
                        register_ftrace_function(&trace_stack_ops);
-               else
+               } else {
                        unregister_ftrace_function(&trace_stack_ops);
+                       register_ftrace_function(&trace_ops);
+               }
 
                return 0;
        }
 
 static struct tracer function_trace __read_mostly =
 {
-       .name        = "function",
-       .init        = function_trace_init,
-       .reset       = function_trace_reset,
-       .start       = function_trace_start,
+       .name           = "function",
+       .init           = function_trace_init,
+       .reset          = function_trace_reset,
+       .start          = function_trace_start,
        .flags          = &func_flags,
        .set_flag       = func_set_flag,
 #ifdef CONFIG_FTRACE_SELFTEST
-       .selftest    = trace_selftest_startup_function,
+       .selftest       = trace_selftest_startup_function,
 #endif
 };