fix doube close channel of subfetcher (#366)

core/state/trie_prefetcher.go

@@ -25,6 +25,8 @@ import (
 	"github.com/ethereum/go-ethereum/metrics"
 )
 
+const abortChanSize = 64
+
 var (
 	// triePrefetchMetricsPrefix is the prefix under which to publis the metrics.
 	triePrefetchMetricsPrefix = "trie/prefetch/"
@@ -41,6 +43,9 @@ type triePrefetcher struct {
 	fetches  map[common.Hash]Trie        // Partially or fully fetcher tries
 	fetchers map[common.Hash]*subfetcher // Subfetchers for each trie
 
+	abortChan chan *subfetcher
+	closeChan chan struct{}
+
 	deliveryMissMeter metrics.Meter
 	accountLoadMeter  metrics.Meter
 	accountDupMeter   metrics.Meter
@@ -56,9 +61,11 @@ type triePrefetcher struct {
 func newTriePrefetcher(db Database, root common.Hash, namespace string) *triePrefetcher {
 	prefix := triePrefetchMetricsPrefix + namespace
 	p := &triePrefetcher{
-		db:       db,
-		root:     root,
-		fetchers: make(map[common.Hash]*subfetcher), // Active prefetchers use the fetchers map
+		db:        db,
+		root:      root,
+		fetchers:  make(map[common.Hash]*subfetcher), // Active prefetchers use the fetchers map
+		abortChan: make(chan *subfetcher, abortChanSize),
+		closeChan: make(chan struct{}),
 
 		deliveryMissMeter: metrics.GetOrRegisterMeter(prefix+"/deliverymiss", nil),
 		accountLoadMeter:  metrics.GetOrRegisterMeter(prefix+"/account/load", nil),
@@ -70,14 +77,34 @@ func newTriePrefetcher(db Database, root common.Hash, namespace string) *triePre
 		storageSkipMeter:  metrics.GetOrRegisterMeter(prefix+"/storage/skip", nil),
 		storageWasteMeter: metrics.GetOrRegisterMeter(prefix+"/storage/waste", nil),
 	}
+	go p.abortLoop()
 	return p
 }
 
+func (p *triePrefetcher) abortLoop() {
+	for {
+		select {
+		case fetcher := <-p.abortChan:
+			fetcher.abort()
+		case <-p.closeChan:
+			// drain fetcher channel
+			for {
+				select {
+				case fetcher := <-p.abortChan:
+					fetcher.abort()
+				default:
+					return
+				}
+			}
+		}
+	}
+}
+
 // close iterates over all the subfetchers, aborts any that were left spinning
 // and reports the stats to the metrics subsystem.
 func (p *triePrefetcher) close() {
 	for _, fetcher := range p.fetchers {
-		fetcher.abort() // safe to do multiple times
+		p.abortChan <- fetcher // safe to do multiple times
 
 		if metrics.Enabled {
 			if fetcher.root == p.root {
@@ -101,6 +128,7 @@ func (p *triePrefetcher) close() {
 			}
 		}
 	}
+	close(p.closeChan)
 	// Clear out all fetchers (will crash on a second call, deliberate)
 	p.fetchers = nil
 }
@@ -174,7 +202,7 @@ func (p *triePrefetcher) trie(root common.Hash) Trie {
 	}
 	// Interrupt the prefetcher if it's by any chance still running and return
 	// a copy of any pre-loaded trie.
-	fetcher.abort() // safe to do multiple times
+	p.abortChan <- fetcher // safe to do multiple times
 
 	trie := fetcher.peek()
 	if trie == nil {