statistics: remove h.mu.Lock when creating NewSessionStatsCollector (#…

…44510)

close #44502

statistics/handle/update.go

@@ -234,9 +234,6 @@ func (s *SessionStatsCollector) UpdateColStatsUsage(colMap colStatsUsageMap) {
 
 // NewSessionStatsCollector allocates a stats collector for a session.
 func (h *Handle) NewSessionStatsCollector() *SessionStatsCollector {
-	h.mu.Lock()
-	defer h.mu.Unlock()
-
 	h.listHead.Lock()
 	defer h.listHead.Unlock()
 	newCollector := &SessionStatsCollector{
@@ -315,8 +312,6 @@ func (s *SessionIndexUsageCollector) Delete() {
 // idxUsageListHead always points to an empty SessionIndexUsageCollector as a sentinel node. So we let idxUsageListHead.next
 // points to new item. It's helpful to sweepIdxUsageList.
 func (h *Handle) NewSessionIndexUsageCollector() *SessionIndexUsageCollector {
-	h.mu.Lock()
-	defer h.mu.Unlock()
 	h.idxUsageListHead.Lock()
 	defer h.idxUsageListHead.Unlock()
 	newCollector := &SessionIndexUsageCollector{