les: avoid shutdown hang (ethereum#23139)

Author: holiman

les/servingqueue.go

@@ -159,27 +159,23 @@ func (sq *servingQueue) newTask(peer *clientPeer, maxTime uint64, priority int64
 // run tokens from the token channel and allow the corresponding tasks to run
 // without entering the priority queue.
 func (sq *servingQueue) threadController() {
+	defer sq.wg.Done()
 	for {
 		token := make(runToken)
 		select {
 		case best := <-sq.queueBestCh:
 			best.tokenCh <- token
 		case <-sq.stopThreadCh:
-			sq.wg.Done()
 			return
 		case <-sq.quit:
-			sq.wg.Done()
 			return
 		}
-		<-token
 		select {
 		case <-sq.stopThreadCh:
-			sq.wg.Done()
 			return
 		case <-sq.quit:
-			sq.wg.Done()
 			return
-		default:
+		case <-token:
 		}
 	}
 }
@@ -298,6 +294,7 @@ func (sq *servingQueue) addTask(task *servingTask) {
 // and always tries to send the highest priority task to queueBestCh. Successfully sent
 // tasks are removed from the queue.
 func (sq *servingQueue) queueLoop() {
+	defer sq.wg.Done()
 	for {
 		if sq.best != nil {
 			expTime := sq.best.expTime
@@ -316,15 +313,13 @@ func (sq *servingQueue) queueLoop() {
 					sq.best, _ = sq.queue.PopItem().(*servingTask)
 				}
 			case <-sq.quit:
-				sq.wg.Done()
 				return
 			}
 		} else {
 			select {
 			case task := <-sq.queueAddCh:
 				sq.addTask(task)
 			case <-sq.quit:
-				sq.wg.Done()
 				return
 			}
 		}
@@ -335,6 +330,7 @@ func (sq *servingQueue) queueLoop() {
 // of active thread controller goroutines.
 func (sq *servingQueue) threadCountLoop() {
 	var threadCountTarget int
+	defer sq.wg.Done()
 	for {
 		for threadCountTarget > sq.threadCount {
 			sq.wg.Add(1)
@@ -347,14 +343,12 @@ func (sq *servingQueue) threadCountLoop() {
 			case sq.stopThreadCh <- struct{}{}:
 				sq.threadCount--
 			case <-sq.quit:
-				sq.wg.Done()
 				return
 			}
 		} else {
 			select {
 			case threadCountTarget = <-sq.setThreadsCh:
 			case <-sq.quit:
-				sq.wg.Done()
 				return
 			}
 		}