From 7386306bcf697928e9e8fffd34776a7e339f4cd7 Mon Sep 17 00:00:00 2001
From: clchen <clchen@leyantech.com>
Date: Fri, 12 Aug 2016 17:31:39 +0800
Subject: [PATCH] fix backend data race

---
 backend.go | 16 +++++++++++-----
 logger.go  |  4 ++--
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/backend.go b/backend.go
index 74d9201..6c34e25 100644
--- a/backend.go
+++ b/backend.go
@@ -4,8 +4,12 @@
 
 package logging
 
+import (
+	"sync/atomic"
+)
+
 // defaultBackend is the backend used for all logging calls.
-var defaultBackend LeveledBackend
+var defaultBackend atomic.Value
 
 // Backend is the interface which a log backend need to implement to be able to
 // be used as a logging backend.
@@ -23,17 +27,19 @@ func SetBackend(backends ...Backend) LeveledBackend {
 		backend = MultiLogger(backends...)
 	}
 
-	defaultBackend = AddModuleLevel(backend)
-	return defaultBackend
+	newDefaultBackend := AddModuleLevel(backend)
+	defaultBackend.Store(&newDefaultBackend)
+
+	return *defaultBackend.Load().(*LeveledBackend)
 }
 
 // SetLevel sets the logging level for the specified module. The module
 // corresponds to the string specified in GetLogger.
 func SetLevel(level Level, module string) {
-	defaultBackend.SetLevel(level, module)
+	(*defaultBackend.Load().(*LeveledBackend)).SetLevel(level, module)
 }
 
 // GetLevel returns the logging level for the specified module.
 func GetLevel(module string) Level {
-	return defaultBackend.GetLevel(module)
+	return (*defaultBackend.Load().(*LeveledBackend)).GetLevel(module)
 }
diff --git a/logger.go b/logger.go
index 535ed9b..9f24739 100644
--- a/logger.go
+++ b/logger.go
@@ -137,7 +137,7 @@ func Reset() {
 
 // IsEnabledFor returns true if the logger is enabled for the given level.
 func (l *Logger) IsEnabledFor(level Level) bool {
-	return defaultBackend.IsEnabledFor(level, l.Module)
+	return (*defaultBackend.Load().(*LeveledBackend)).IsEnabledFor(level, l.Module)
 }
 
 func (l *Logger) log(lvl Level, format *string, args ...interface{}) {
@@ -167,7 +167,7 @@ func (l *Logger) log(lvl Level, format *string, args ...interface{}) {
 		return
 	}
 
-	defaultBackend.Log(lvl, 2+l.ExtraCalldepth, record)
+	(*defaultBackend.Load().(*LeveledBackend)).Log(lvl, 2+l.ExtraCalldepth, record)
 }
 
 // Fatal is equivalent to l.Critical(fmt.Sprint()) followed by a call to os.Exit(1).