consensus: polish a bit

consensus/clique/clique.go

@@ -672,7 +672,7 @@ func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
 	return new(big.Int).Set(diffNoTurn)
 }
 
-// Close implements consensus.Engine, returning internal error and close the clique.
+// Close implements consensus.Engine. It's a noop for clique as there is are no background threads.
 func (c *Clique) Close() error {
 	return nil
 }

consensus/consensus.go

@@ -97,7 +97,7 @@ type Engine interface {
 	// APIs returns the RPC APIs this consensus engine provides.
 	APIs(chain ChainReader) []rpc.API
 
-	// Close closes the consensus engine.
+	// Close terminates any background threads maintained by the consensus engine.
 	Close() error
 }
 

consensus/ethash/api.go

@@ -24,10 +24,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 )
 
-var (
+var errEthashStopped = errors.New("ethash stopped")
-	errEthashStopped   = errors.New("ethash stopped")
-	errAPINotSupported = errors.New("the current ethash running mode does not support this API")
-)
 
 // API exposes ethash related methods for the RPC interface.
 type API struct {
@@ -42,26 +39,27 @@ type API struct {
 //   result[2] - 32 bytes hex encoded boundary condition ("target"), 2^256/difficulty
 func (api *API) GetWork() ([3]string, error) {
 	if api.ethash.config.PowMode != ModeNormal && api.ethash.config.PowMode != ModeTest {
-		return [3]string{}, errAPINotSupported
+		return [3]string{}, errors.New("not supported")
 	}
 
 	var (
 		workCh = make(chan [3]string, 1)
-		errCh  = make(chan error, 1)
+		errc   = make(chan error, 1)
-		err    error
 	)
 
 	select {
-	case api.ethash.fetchWorkCh <- &sealWork{errCh: errCh, resCh: workCh}:
+	case api.ethash.fetchWorkCh <- &sealWork{errc: errc, res: workCh}:
 	case <-api.ethash.exitCh:
 		return [3]string{}, errEthashStopped
 	}
 
-	if err = <-errCh; err == nil {
+	select {
-		return <-workCh, nil
+	case work := <-workCh:
-	}
+		return work, nil
+	case err := <-errc:
 		return [3]string{}, err
 	}
+}
 
 // SubmitWork can be used by external miner to submit their POW solution.
 // It returns an indication if the work was accepted.
@@ -71,20 +69,20 @@ func (api *API) SubmitWork(nonce types.BlockNonce, hash, digest common.Hash) boo
 		return false
 	}
 
-	var errCh = make(chan error, 1)
+	var errc = make(chan error, 1)
 
 	select {
 	case api.ethash.submitWorkCh <- &mineResult{
 		nonce:     nonce,
 		mixDigest: digest,
 		hash:      hash,
-		errCh:     errCh,
+		errc:      errc,
 	}:
 	case <-api.ethash.exitCh:
 		return false
 	}
 
-	err := <-errCh
+	err := <-errc
 	return err == nil
 }
 
@@ -99,16 +97,16 @@ func (api *API) SubmitHashRate(rate hexutil.Uint64, id common.Hash) bool {
 		return false
 	}
 
-	var doneCh = make(chan struct{}, 1)
+	var done = make(chan struct{}, 1)
 
 	select {
-	case api.ethash.submitRateCh <- &hashrate{done: doneCh, rate: uint64(rate), id: id}:
+	case api.ethash.submitRateCh <- &hashrate{done: done, rate: uint64(rate), id: id}:
 	case <-api.ethash.exitCh:
 		return false
 	}
 
 	// Block until hash rate submitted successfully.
-	<-doneCh
+	<-done
 
 	return true
 }

consensus/ethash/ethash.go

@@ -397,7 +397,7 @@ type mineResult struct {
 	mixDigest common.Hash
 	hash      common.Hash
 
-	errCh chan error
+	errc chan error
 }
 
 // hashrate wraps the hash rate submitted by the remote sealer.
@@ -411,8 +411,8 @@ type hashrate struct {
 
 // sealWork wraps a seal work package for remote sealer.
 type sealWork struct {
-	errCh chan error
+	errc chan error
-	resCh chan [3]string
+	res  chan [3]string
 }
 
 // Ethash is a consensus engine based on proof-of-work implementing the ethash
@@ -447,7 +447,7 @@ type Ethash struct {
 	exitCh    chan chan error // Notification channel to exiting backend threads
 }
 
-// New creates a full sized ethash PoW scheme.
+// New creates a full sized ethash PoW scheme and starts a background thread for remote mining.
 func New(config Config) *Ethash {
 	if config.CachesInMem <= 0 {
 		log.Warn("One ethash cache must always be in memory", "requested", config.CachesInMem)
@@ -557,9 +557,9 @@ func (ethash *Ethash) Close() error {
 		if ethash.exitCh == nil {
 			return
 		}
-		errCh := make(chan error)
+		errc := make(chan error)
-		ethash.exitCh <- errCh
+		ethash.exitCh <- errc
-		err = <-errCh
+		err = <-errc
 		close(ethash.exitCh)
 	})
 	return err
@@ -644,18 +644,17 @@ func (ethash *Ethash) Hashrate() float64 {
 	if ethash.config.PowMode != ModeNormal && ethash.config.PowMode != ModeTest {
 		return ethash.hashrate.Rate1()
 	}
-	var resCh = make(chan uint64, 1)
+	var res = make(chan uint64, 1)
 
 	select {
-	case ethash.fetchRateCh <- resCh:
+	case ethash.fetchRateCh <- res:
 	case <-ethash.exitCh:
 		// Return local hashrate only if ethash is stopped.
 		return ethash.hashrate.Rate1()
 	}
 
 	// Gather total submitted hash rate of remote sealers.
-	total := <-resCh
+	return ethash.hashrate.Rate1() + float64(<-res)
-	return ethash.hashrate.Rate1() + float64(total)
 }
 
 // APIs implements consensus.Engine, returning the user facing RPC APIs.

consensus/ethash/sealer.go

@@ -235,7 +235,6 @@ func (ethash *Ethash) remote() {
 	ticker := time.NewTicker(5 * time.Second)
 	defer ticker.Stop()
 
-running:
 	for {
 		select {
 		case block := <-ethash.workCh:
@@ -251,18 +250,17 @@ running:
 			// Return current mining work to remote miner.
 			miningWork, err := getWork()
 			if err != nil {
-				work.errCh <- err
+				work.errc <- err
 			} else {
-				close(work.errCh)
+				work.res <- miningWork
-				work.resCh <- miningWork
 			}
 
 		case result := <-ethash.submitWorkCh:
 			// Verify submitted PoW solution based on maintained mining blocks.
 			if submitWork(result.nonce, result.mixDigest, result.hash) {
-				close(result.errCh)
+				result.errc <- nil
 			} else {
-				result.errCh <- errInvalidSealResult
+				result.errc <- errInvalidSealResult
 			}
 
 		case result := <-ethash.submitRateCh:
@@ -287,11 +285,11 @@ running:
 				}
 			}
 
-		case errCh := <-ethash.exitCh:
+		case errc := <-ethash.exitCh:
 			// Exit remote loop if ethash is closed and return relevant error.
-			errCh <- nil
+			errc <- nil
-			break running
-		}
-	}
 			log.Trace("Ethash remote sealer is exiting")
+			return
+		}
+	}
 }