diff --git a/core/box.go b/core/box.go
index e682fc6..172ca11 100644
--- a/core/box.go
+++ b/core/box.go
@@ -489,6 +489,7 @@ func (s *Box) Close() error {
 		close(s.done)
 	}
 	var err error
+	s.logger.Info("closing sing-box")
 	for _, closeItem := range []struct {
 		name    string
 		service adapter.Lifecycle
@@ -552,6 +553,7 @@ func (s *Box) Close() error {
 	}
 	err = errors.Join(err, closeErr)
 	s.logger.Trace("close logger completed (", F.Seconds(time.Since(startTime).Seconds()), "s)")
+	s.logger.Info("sing-box closed (live time: ", F.Seconds(time.Since(s.createdAt).Seconds()), "s)")
 	return err
 }
 
diff --git a/core/main.go b/core/main.go
index bbdf4e5..e43eb94 100644
--- a/core/main.go
+++ b/core/main.go
@@ -2,7 +2,6 @@ package core
 
 import (
 	"context"
-	"sync"
 
 	"github.com/alireza0/s-ui/logger"
 
@@ -29,7 +28,6 @@ var (
 )
 
 type Core struct {
-	mu        sync.RWMutex
 	isRunning bool
 	instance  *Box
 }
@@ -48,15 +46,10 @@ func (c *Core) GetCtx() context.Context {
 }
 
 func (c *Core) GetInstance() *Box {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
 	return c.instance
 }
 
 func (c *Core) Start(sbConfig []byte) error {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
 	var opt option.Options
 	err := opt.UnmarshalJSONContext(globalCtx, sbConfig)
 	if err != nil {
@@ -90,9 +83,6 @@ func (c *Core) Start(sbConfig []byte) error {
 }
 
 func (c *Core) Stop() error {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
 	c.isRunning = false
 	if c.instance == nil {
 		return nil
@@ -103,7 +93,5 @@ func (c *Core) Stop() error {
 }
 
 func (c *Core) IsRunning() bool {
-	c.mu.RLock()
-	defer c.mu.RUnlock()
 	return c.isRunning
 }
diff --git a/service/config.go b/service/config.go
index d2a130c..91ec07d 100644
--- a/service/config.go
+++ b/service/config.go
@@ -96,6 +96,7 @@ func (s *ConfigService) StartCore() error {
 		return nil
 	}
 	if time.Since(lastStartFailTime) < startCooldown {
+		logger.Info("start core cooldown ", startCooldown/time.Second, " seconds")
 		startCoreMu.Unlock()
 		return nil
 	}
@@ -133,6 +134,19 @@ func (s *ConfigService) RestartCore() error {
 }
 
 func (s *ConfigService) restartCoreWithConfig(config json.RawMessage) error {
+	startCoreMu.Lock()
+	if startCoreInProgress {
+		startCoreMu.Unlock()
+		return nil
+	}
+	startCoreInProgress = true
+	startCoreMu.Unlock()
+	defer func() {
+		startCoreMu.Lock()
+		startCoreInProgress = false
+		startCoreMu.Unlock()
+	}()
+
 	if corePtr.IsRunning() {
 		if err := corePtr.Stop(); err != nil {
 			logger.Error("restart sing-box err (stop):", err.Error())