diff --git a/common/mux/client.go b/common/mux/client.go
index b6148fbc..f73fc509 100644
--- a/common/mux/client.go
+++ b/common/mux/client.go
@@ -174,7 +174,6 @@ type ClientWorker struct {
 	link           transport.Link
 	done           *done.Instance
 	strategy       ClientStrategy
-	access         sync.Mutex
 }
 
 var (
@@ -277,6 +276,8 @@ func (m *ClientWorker) IsClosing() bool {
 	return false
 }
 
+// IsFull returns true if this ClientWorker is unable to accept more connections.
+// it might be because it is closing, or the number of connections has reached the limit.
 func (m *ClientWorker) IsFull() bool {
 	if m.IsClosing() || m.Closed() {
 		return true
@@ -290,14 +291,12 @@ func (m *ClientWorker) IsFull() bool {
 }
 
 func (m *ClientWorker) Dispatch(ctx context.Context, link *transport.Link) bool {
-	m.access.Lock()
-	defer m.access.Unlock()
 	if m.IsFull() {
 		return false
 	}
 
 	sm := m.sessionManager
-	s := sm.Allocate()
+	s := sm.Allocate(int(m.strategy.MaxConcurrency))
 	if s == nil {
 		return false
 	}