eth: close miner on exit (instead of just stopping) (ethereum#21992)

This ensures that all miner goroutines have exited before stopping the blockchain. 

Co-authored-by: Felix Lange <fjl@twurst.com>

eth/backend.go

@@ -554,7 +554,7 @@ func (s *Ethereum) Stop() error {
 	s.bloomIndexer.Close()
 	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

@@ -20,6 +20,7 @@ package miner
 import (
 	"fmt"
 	"math/big"
+	"sync"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -63,6 +64,8 @@ type Miner struct {
 	exitCh   chan struct{}
 	startCh  chan common.Address
 	stopCh   chan struct{}
+
+	wg sync.WaitGroup
 }
 
 func New(eth Backend, config *Config, chainConfig *params.ChainConfig, mux *event.TypeMux, engine consensus.Engine, isLocalBlock func(block *types.Block) bool) *Miner {
@@ -75,8 +78,8 @@ func New(eth Backend, config *Config, chainConfig *params.ChainConfig, mux *even
 		stopCh:  make(chan struct{}),
 		worker:  newWorker(config, chainConfig, engine, eth, mux, isLocalBlock, true),
 	}
+	miner.wg.Add(1)
 	go miner.update()
-
 	return miner
 }
 
@@ -85,6 +88,8 @@ func New(eth Backend, config *Config, chainConfig *params.ChainConfig, mux *even
 // the loop is exited. This to prevent a major security vuln where external parties can DOS you with blocks
 // and halt your mining operation for as long as the DOS continues.
 func (miner *Miner) update() {
+	defer miner.wg.Done()
+
 	events := miner.mux.Subscribe(downloader.StartEvent{}, downloader.DoneEvent{}, downloader.FailedEvent{})
 	defer func() {
 		if !events.Closed() {
@@ -154,6 +159,7 @@ func (miner *Miner) Stop() {
 
 func (miner *Miner) Close() {
 	close(miner.exitCh)
+	miner.wg.Wait()
 }
 
 func (miner *Miner) Mining() bool {

miner/worker.go

@@ -150,6 +150,8 @@ type worker struct {
 	resubmitIntervalCh chan time.Duration
 	resubmitAdjustCh   chan *intervalAdjust
 
+	wg sync.WaitGroup
+
 	current      *environment                 // An environment for current running cycle.
 	localUncles  map[common.Hash]*types.Block // A set of side blocks generated locally as the possible uncle blocks.
 	remoteUncles map[common.Hash]*types.Block // A set of side blocks as the possible uncle blocks.
@@ -225,6 +227,7 @@ func newWorker(config *Config, chainConfig *params.ChainConfig, engine consensus
 		recommit = minRecommitInterval
 	}
 
+	worker.wg.Add(4)
 	go worker.mainLoop()
 	go worker.newWorkLoop(recommit)
 	go worker.resultLoop()
@@ -323,6 +326,7 @@ func (w *worker) close() {
 	}
 	atomic.StoreInt32(&w.running, 0)
 	close(w.exitCh)
+	w.wg.Wait()
 }
 
 // recalcRecommit recalculates the resubmitting interval upon feedback.
@@ -349,6 +353,7 @@ func recalcRecommit(minRecommit, prev time.Duration, target float64, inc bool) t
 
 // newWorkLoop is a standalone goroutine to submit new mining work upon received events.
 func (w *worker) newWorkLoop(recommit time.Duration) {
+	defer w.wg.Done()
 	var (
 		interrupt   *int32
 		minRecommit = recommit // minimal resubmit interval specified by user.
@@ -446,6 +451,7 @@ func (w *worker) newWorkLoop(recommit time.Duration) {
 
 // mainLoop is a standalone goroutine to regenerate the sealing task based on the received event.
 func (w *worker) mainLoop() {
+	defer w.wg.Done()
 	defer w.txsSub.Unsubscribe()
 	defer w.chainHeadSub.Unsubscribe()
 	defer w.chainSideSub.Unsubscribe()
@@ -548,6 +554,7 @@ func (w *worker) mainLoop() {
 // taskLoop is a standalone goroutine to fetch sealing task from the generator and
 // push them to consensus engine.
 func (w *worker) taskLoop() {
+	defer w.wg.Done()
 	var (
 		stopCh chan struct{}
 		prev   common.Hash
@@ -595,6 +602,7 @@ func (w *worker) taskLoop() {
 // resultLoop is a standalone goroutine to handle sealing result submitting
 // and flush relative data to the database.
 func (w *worker) resultLoop() {
+	defer w.wg.Done()
 	for {
 		select {
 		case block := <-w.resultCh: