ftrace: prevent recursion

Impact: prevent unnecessary stack recursion

if the resched flag was set before we entered, then don't reschedule.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/ring_buffer.c

@@ -1215,7 +1215,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
 
  out:
 	if (resched)
-		preempt_enable_notrace();
+		preempt_enable_no_resched_notrace();
 	else
 		preempt_enable_notrace();
 	return NULL;