Ensure the miner is closed

Also make miner and worker wait for goroutines to end at Shutdown.

Without this change, when shutting down its possible for the worker to
try and access the db after it has been closed, which results in a
critical failure and runs the risk of corrupting the db.

eth/backend.go

@@ -555,6 +555,7 @@ func (s *Ethereum) Stop() error {
 	close(s.closeBloomHandler)
 	s.txPool.Stop()
 	s.miner.Stop()
+	s.miner.Close()
 	s.blockchain.Stop()
 	s.engine.Close()
 	rawdb.PopUncleanShutdownMarker(s.chainDb)

miner/miner.go

@@ -139,6 +139,7 @@ func (miner *Miner) update() {
 			miner.worker.stop()
 		case <-miner.exitCh:
 			miner.worker.close()
+			miner.exitCh <- struct{}{}
 			return
 		}
 	}
@@ -153,7 +154,8 @@ func (miner *Miner) Stop() {
 }
 
 func (miner *Miner) Close() {
-	close(miner.exitCh)
+	miner.exitCh <- struct{}{}
+	<-miner.exitCh
 }
 
 func (miner *Miner) Mining() bool {

miner/worker.go

@@ -147,6 +147,7 @@ type worker struct {
 	resultCh           chan *types.Block
 	startCh            chan struct{}
 	exitCh             chan struct{}
+	wg                 sync.WaitGroup
 	resubmitIntervalCh chan time.Duration
 	resubmitAdjustCh   chan *intervalAdjust
 
@@ -225,10 +226,23 @@ func newWorker(config *Config, chainConfig *params.ChainConfig, engine consensus
 		recommit = minRecommitInterval
 	}
 
-	go worker.mainLoop()
-	go worker.newWorkLoop(recommit)
-	go worker.resultLoop()
-	go worker.taskLoop()
+	worker.wg.Add(4)
+	go func() {
+		defer worker.wg.Done()
+		worker.mainLoop()
+	}()
+	go func() {
+		defer worker.wg.Done()
+		worker.newWorkLoop(recommit)
+	}()
+	go func() {
+		defer worker.wg.Done()
+		worker.resultLoop()
+	}()
+	go func() {
+		defer worker.wg.Done()
+		worker.taskLoop()
+	}()
 
 	// Submit first work to initialize pending state.
 	if init {
@@ -323,6 +337,7 @@ func (w *worker) close() {
 	}
 	atomic.StoreInt32(&w.running, 0)
 	close(w.exitCh)
+	w.wg.Wait()
 }
 
 // recalcRecommit recalculates the resubmitting interval upon feedback.