miner: use channels instead of atomics in update loop (#21536)

This PR changes several different things:

- Adds test cases for the miner loop
- Stops the worker if it wasn't already stopped in worker.Close()
- Uses channels instead of atomics in the miner.update() loop

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

miner/miner.go

@@ -20,7 +20,6 @@ package miner
 import (
 	"fmt"
 	"math/big"
-	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -61,9 +60,8 @@ type Miner struct {
 	eth      Backend
 	engine   consensus.Engine
 	exitCh   chan struct{}
-
-	canStart    int32 // can start indicates whether we can start the mining operation
-	shouldStart int32 // should start indicates whether we should start after sync
+	startCh  chan common.Address
+	stopCh   chan struct{}
 }
 
 func New(eth Backend, config *Config, chainConfig *params.ChainConfig, mux *event.TypeMux, engine consensus.Engine, isLocalBlock func(block *types.Block) bool) *Miner {
@@ -72,8 +70,9 @@ func New(eth Backend, config *Config, chainConfig *params.ChainConfig, mux *even
 		mux:     mux,
 		engine:  engine,
 		exitCh:  make(chan struct{}),
+		startCh: make(chan common.Address),
+		stopCh:  make(chan struct{}),
 		worker:  newWorker(config, chainConfig, engine, eth, mux, isLocalBlock, true),
-		canStart: 1,
 	}
 	go miner.update()
 
@@ -88,6 +87,7 @@ func (miner *Miner) update() {
 	events := miner.mux.Subscribe(downloader.StartEvent{}, downloader.DoneEvent{}, downloader.FailedEvent{})
 	defer events.Unsubscribe()
 
+	shouldStart := false
 	for {
 		select {
 		case ev := <-events.Chan():
@@ -96,47 +96,40 @@ func (miner *Miner) update() {
 			}
 			switch ev.Data.(type) {
 			case downloader.StartEvent:
-				atomic.StoreInt32(&miner.canStart, 0)
-				if miner.Mining() {
-					miner.Stop()
-					atomic.StoreInt32(&miner.shouldStart, 1)
+				wasMining := miner.Mining()
+				miner.worker.stop()
+				if wasMining {
+					// Resume mining after sync was finished
+					shouldStart = true
 					log.Info("Mining aborted due to sync")
 				}
 			case downloader.DoneEvent, downloader.FailedEvent:
-				shouldStart := atomic.LoadInt32(&miner.shouldStart) == 1
-
-				atomic.StoreInt32(&miner.canStart, 1)
-				atomic.StoreInt32(&miner.shouldStart, 0)
 				if shouldStart {
-					miner.Start(miner.coinbase)
+					miner.SetEtherbase(miner.coinbase)
+					miner.worker.start()
 				}
-				// stop immediately and ignore all further pending events
-				return
 			}
+		case addr := <-miner.startCh:
+			miner.SetEtherbase(addr)
+			miner.worker.start()
+		case <-miner.stopCh:
+			miner.worker.stop()
 		case <-miner.exitCh:
+			miner.worker.close()
 			return
 		}
 	}
 }
 
 func (miner *Miner) Start(coinbase common.Address) {
-	atomic.StoreInt32(&miner.shouldStart, 1)
-	miner.SetEtherbase(coinbase)
-
-	if atomic.LoadInt32(&miner.canStart) == 0 {
-		log.Info("Network syncing, will start miner afterwards")
-		return
-	}
-	miner.worker.start()
+	miner.startCh <- coinbase
 }
 
 func (miner *Miner) Stop() {
-	miner.worker.stop()
-	atomic.StoreInt32(&miner.shouldStart, 0)
+	miner.stopCh <- struct{}{}
 }
 
 func (miner *Miner) Close() {
-	miner.worker.close()
 	close(miner.exitCh)
 }
 

miner/miner_test.go

@@ -0,0 +1,170 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package miner implements Ethereum block creation and mining.
+package miner
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/eth/downloader"
+	"github.com/ethereum/go-ethereum/ethdb/memorydb"
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+type mockBackend struct {
+	bc     *core.BlockChain
+	txPool *core.TxPool
+}
+
+func NewMockBackend(bc *core.BlockChain, txPool *core.TxPool) *mockBackend {
+	return &mockBackend{
+		bc:     bc,
+		txPool: txPool,
+	}
+}
+
+func (m *mockBackend) BlockChain() *core.BlockChain {
+	return m.bc
+}
+
+func (m *mockBackend) TxPool() *core.TxPool {
+	return m.txPool
+}
+
+type testBlockChain struct {
+	statedb       *state.StateDB
+	gasLimit      uint64
+	chainHeadFeed *event.Feed
+}
+
+func (bc *testBlockChain) CurrentBlock() *types.Block {
+	return types.NewBlock(&types.Header{
+		GasLimit: bc.gasLimit,
+	}, nil, nil, nil, new(trie.Trie))
+}
+
+func (bc *testBlockChain) GetBlock(hash common.Hash, number uint64) *types.Block {
+	return bc.CurrentBlock()
+}
+
+func (bc *testBlockChain) StateAt(common.Hash) (*state.StateDB, error) {
+	return bc.statedb, nil
+}
+
+func (bc *testBlockChain) SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription {
+	return bc.chainHeadFeed.Subscribe(ch)
+}
+
+func TestMiner(t *testing.T) {
+	miner, mux := createMiner(t)
+	miner.Start(common.HexToAddress("0x12345"))
+	waitForMiningState(t, miner, true)
+	// Start the downloader
+	mux.Post(downloader.StartEvent{})
+	waitForMiningState(t, miner, false)
+	// Stop the downloader and wait for the update loop to run
+	mux.Post(downloader.DoneEvent{})
+	waitForMiningState(t, miner, true)
+	// Start the downloader and wait for the update loop to run
+	mux.Post(downloader.StartEvent{})
+	waitForMiningState(t, miner, false)
+	// Stop the downloader and wait for the update loop to run
+	mux.Post(downloader.FailedEvent{})
+	waitForMiningState(t, miner, true)
+}
+
+func TestStartStopMiner(t *testing.T) {
+	miner, _ := createMiner(t)
+	waitForMiningState(t, miner, false)
+	miner.Start(common.HexToAddress("0x12345"))
+	waitForMiningState(t, miner, true)
+	miner.Stop()
+	waitForMiningState(t, miner, false)
+}
+
+func TestCloseMiner(t *testing.T) {
+	miner, _ := createMiner(t)
+	waitForMiningState(t, miner, false)
+	miner.Start(common.HexToAddress("0x12345"))
+	waitForMiningState(t, miner, true)
+	// Terminate the miner and wait for the update loop to run
+	miner.Close()
+	waitForMiningState(t, miner, false)
+}
+
+// waitForMiningState waits until either
+// * the desired mining state was reached
+// * a timeout was reached which fails the test
+func waitForMiningState(t *testing.T, m *Miner, mining bool) {
+	t.Helper()
+
+	var state bool
+	for i := 0; i < 100; i++ {
+		if state = m.Mining(); state == mining {
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatalf("Mining() == %t, want %t", state, mining)
+}
+
+func createMiner(t *testing.T) (*Miner, *event.TypeMux) {
+	// Create Ethash config
+	config := Config{
+		Etherbase: common.HexToAddress("123456789"),
+	}
+	// Create chainConfig
+	memdb := memorydb.New()
+	chainDB := rawdb.NewDatabase(memdb)
+	genesis := core.DeveloperGenesisBlock(15, common.HexToAddress("12345"))
+	chainConfig, _, err := core.SetupGenesisBlock(chainDB, genesis)
+	if err != nil {
+		t.Fatalf("can't create new chain config: %v", err)
+	}
+	// Create event Mux
+	mux := new(event.TypeMux)
+	// Create consensus engine
+	engine := ethash.New(ethash.Config{}, []string{}, false)
+	engine.SetThreads(-1)
+	// Create isLocalBlock
+	isLocalBlock := func(block *types.Block) bool {
+		return true
+	}
+	// Create Ethereum backend
+	limit := uint64(1000)
+	bc, err := core.NewBlockChain(chainDB, new(core.CacheConfig), chainConfig, engine, vm.Config{}, isLocalBlock, &limit)
+	if err != nil {
+		t.Fatalf("can't create new chain %v", err)
+	}
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(rawdb.NewMemoryDatabase()), nil)
+	blockchain := &testBlockChain{statedb, 10000000, new(event.Feed)}
+
+	pool := core.NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
+	backend := NewMockBackend(bc, pool)
+	// Create Miner
+	return New(backend, &config, chainConfig, mux, engine, isLocalBlock), mux
+}

miner/worker.go

@@ -303,6 +303,7 @@ func (w *worker) isRunning() bool {
 // close terminates all background threads maintained by the worker.
 // Note the worker does not support being closed multiple times.
 func (w *worker) close() {
+	atomic.StoreInt32(&w.running, 0)
 	close(w.exitCh)
 }