eth/downloader: always reenter processing if not exiting

eth/downloader/downloader.go

@@ -48,7 +48,6 @@ var (
 	errCrossCheckFailed = errors.New("block cross-check failed")
 	errCancelHashFetch  = errors.New("hash fetching canceled (requested)")
 	errCancelBlockFetch = errors.New("block downloading canceled (requested)")
-	errCancelChainImport = errors.New("chain importing canceled (requested)")
 	errNoSyncActive     = errors.New("no sync active")
 )
 
@@ -719,7 +718,7 @@ func (d *Downloader) banBlocks(peerId string, head common.Hash) error {
 //       between these state changes, a block may have arrived, but a processing
 //       attempt denied, so we need to re-enter to ensure the block isn't left
 //       to idle in the cache.
-func (d *Downloader) process() (err error) {
+func (d *Downloader) process() {
 	// Make sure only one goroutine is ever allowed to process blocks at once
 	if !atomic.CompareAndSwapInt32(&d.processing, 0, 1) {
 		return
@@ -729,8 +728,8 @@ func (d *Downloader) process() (err error) {
 	// the fresh blocks might have been rejected entry to to this present thread
 	// not yet releasing the `processing` state.
 	defer func() {
-		if err == nil && d.queue.GetHeadBlock() != nil {
-			err = d.process()
+		if atomic.LoadInt32(&d.interrupt) == 0 && d.queue.GetHeadBlock() != nil {
+			d.process()
 		}
 	}()
 	// Release the lock upon exit (note, before checking for reentry!), and set
@@ -748,7 +747,7 @@ func (d *Downloader) process() (err error) {
 		// Fetch the next batch of blocks
 		blocks := d.queue.TakeBlocks()
 		if len(blocks) == 0 {
-			return nil
+			return
 		}
 		// Reset the import statistics
 		d.importLock.Lock()
@@ -762,7 +761,7 @@ func (d *Downloader) process() (err error) {
 		for len(blocks) != 0 {
 			// Check for any termination requests
 			if atomic.LoadInt32(&d.interrupt) == 1 {
-				return errCancelChainImport
+				return
 			}
 			// Retrieve the first batch of blocks to insert
 			max := int(math.Min(float64(len(blocks)), float64(maxBlockProcess)))
@@ -776,7 +775,7 @@ func (d *Downloader) process() (err error) {
 				glog.V(logger.Debug).Infof("Block #%d import failed: %v", raw[index].NumberU64(), err)
 				d.dropPeer(blocks[index].OriginPeer)
 				d.cancel()
-				return errCancelChainImport
+				return
 			}
 			blocks = blocks[max:]
 		}

eth/downloader/downloader_test.go

@@ -764,7 +764,6 @@ func TestHashAttackerDropping(t *testing.T) {
 		{errCrossCheckFailed, true},  // Hash-origin failed to pass a block cross check, drop
 		{errCancelHashFetch, false},  // Synchronisation was canceled, origin may be innocent, don't drop
 		{errCancelBlockFetch, false}, // Synchronisation was canceled, origin may be innocent, don't drop
-		{errCancelChainImport, false}, // Synchronisation was canceled, origin may be innocent, don't drop
 	}
 	// Run the tests and check disconnection status
 	tester := newTester()