diff --git a/logs/file.go b/logs/file.go
index 9d3f78a0..672823fa 100644
--- a/logs/file.go
+++ b/logs/file.go
@@ -30,7 +30,7 @@ import (
 // fileLogWriter implements LoggerInterface.
 // It writes messages by lines limit, file size limit, or time frequency.
 type fileLogWriter struct {
-	sync.Mutex // write log order by order and  atomic incr maxLinesCurLines and maxSizeCurSize
+	sync.RWMutex // write log order by order and  atomic incr maxLinesCurLines and maxSizeCurSize
 	// The opened file
 	Filename   string `json:"filename"`
 	fileWriter *os.File
@@ -77,7 +77,7 @@ func newFileWriter() Logger {
 //	{
 //	"filename":"logs/beego.log",
 //	"maxLines":10000,
-//	"maxsize":1<<30,
+//	"maxsize":1024,
 //	"daily":true,
 //	"maxDays":15,
 //	"rotate":true,
@@ -128,7 +128,9 @@ func (w *fileLogWriter) WriteMsg(when time.Time, msg string, level int) error {
 	h, d := formatTimeHeader(when)
 	msg = string(h) + msg + "\n"
 	if w.Rotate {
+		w.RLock()
 		if w.needRotate(len(msg), d) {
+			w.RUnlock()
 			w.Lock()
 			if w.needRotate(len(msg), d) {
 				if err := w.doRotate(when); err != nil {
@@ -136,6 +138,8 @@ func (w *fileLogWriter) WriteMsg(when time.Time, msg string, level int) error {
 				}
 			}
 			w.Unlock()
+		} else {
+			w.RUnlock()
 		}
 	}