ftrace: Narrow down the protected area of graph_lock

The parser set up is just a generic utility that uses local variables
allocated by the function. There's no need to hold the graph_lock for
this set up.

This also makes the code simpler.

Link: http://lkml.kernel.org/r/1381739066-7531-4-git-send-email-namhyung@kernel.org

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -3973,37 +3973,33 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos)
 {
 	struct trace_parser parser;
-	ssize_t read, ret;
+	ssize_t read, ret = 0;
 	struct ftrace_graph_data *fgd = file->private_data;
 
 	if (!cnt)
 		return 0;
 
-	mutex_lock(&graph_lock);
-
-	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
-		ret = -ENOMEM;
-		goto out_unlock;
-	}
+	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX))
+		return -ENOMEM;
 
 	read = trace_get_user(&parser, ubuf, cnt, ppos);
 
 	if (read >= 0 && trace_parser_loaded((&parser))) {
 		parser.buffer[parser.idx] = 0;
 
+		mutex_lock(&graph_lock);
+
 		/* we allow only one expression at a time */
 		ret = ftrace_set_func(fgd->table, fgd->count, fgd->size,
 				      parser.buffer);
-		if (ret)
-			goto out_free;
+
+		mutex_unlock(&graph_lock);
 	}
 
-	ret = read;
+	if (!ret)
+		ret = read;
 
-out_free:
 	trace_parser_put(&parser);
-out_unlock:
-	mutex_unlock(&graph_lock);
 
 	return ret;
 }