eth/filter: check nil pointer when unsubscribe (ethereum#16682)

* eth/filter: check nil pointer when unsubscribe

* eth/filters, accounts, rpc: abort system if subscribe failed

* eth/filter: add crit log before exit

* eth/filter, event: minor fixes

eth/filters/filter_system.go

@@ -31,6 +31,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/event"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rpc"
 )
 
@@ -92,8 +93,21 @@ type EventSystem struct {
 	backend   Backend
 	lightMode bool
 	lastHead  *types.Header
-	install   chan *subscription // install filter for event notification
-	uninstall chan *subscription // remove filter for event notification
+
+	// Subscriptions
+	txSub         event.Subscription         // Subscription for new transaction event
+	logsSub       event.Subscription         // Subscription for new log event
+	rmLogsSub     event.Subscription         // Subscription for removed log event
+	chainSub      event.Subscription         // Subscription for new chain event
+	pendingLogSub *event.TypeMuxSubscription // Subscription for pending log event
+
+	// Channels
+	install   chan *subscription         // install filter for event notification
+	uninstall chan *subscription         // remove filter for event notification
+	txCh      chan core.TxPreEvent       // Channel to receive new transaction event
+	logsCh    chan []*types.Log          // Channel to receive new log event
+	rmLogsCh  chan core.RemovedLogsEvent // Channel to receive removed log event
+	chainCh   chan core.ChainEvent       // Channel to receive new chain event
 }
 
 // NewEventSystem creates a new manager that listens for event on the given mux,
@@ -109,10 +123,27 @@ func NewEventSystem(mux *event.TypeMux, backend Backend, lightMode bool) *EventS
 		lightMode: lightMode,
 		install:   make(chan *subscription),
 		uninstall: make(chan *subscription),
+		txCh:      make(chan core.TxPreEvent, txChanSize),
+		logsCh:    make(chan []*types.Log, logsChanSize),
+		rmLogsCh:  make(chan core.RemovedLogsEvent, rmLogsChanSize),
+		chainCh:   make(chan core.ChainEvent, chainEvChanSize),
 	}
 
-	go m.eventLoop()
+	// Subscribe events
+	m.txSub = m.backend.SubscribeTxPreEvent(m.txCh)
+	m.logsSub = m.backend.SubscribeLogsEvent(m.logsCh)
+	m.rmLogsSub = m.backend.SubscribeRemovedLogsEvent(m.rmLogsCh)
+	m.chainSub = m.backend.SubscribeChainEvent(m.chainCh)
+	// TODO(rjl493456442): use feed to subscribe pending log event
+	m.pendingLogSub = m.mux.Subscribe(core.PendingLogsEvent{})
+
+	// Make sure none of the subscriptions are empty
+	if m.txSub == nil || m.logsSub == nil || m.rmLogsSub == nil || m.chainSub == nil ||
+		m.pendingLogSub.Closed() {
+		log.Crit("Subscribe for event system failed")
+	}
 
+	go m.eventLoop()
 	return m
 }
 
@@ -412,50 +443,35 @@ func (es *EventSystem) lightFilterLogs(header *types.Header, addresses []common.
 
 // eventLoop (un)installs filters and processes mux events.
 func (es *EventSystem) eventLoop() {
-	var (
-		index = make(filterIndex)
-		sub   = es.mux.Subscribe(core.PendingLogsEvent{})
-		// Subscribe TxPreEvent form txpool
-		txCh  = make(chan core.TxPreEvent, txChanSize)
-		txSub = es.backend.SubscribeTxPreEvent(txCh)
-		// Subscribe RemovedLogsEvent
-		rmLogsCh  = make(chan core.RemovedLogsEvent, rmLogsChanSize)
-		rmLogsSub = es.backend.SubscribeRemovedLogsEvent(rmLogsCh)
-		// Subscribe []*types.Log
-		logsCh  = make(chan []*types.Log, logsChanSize)
-		logsSub = es.backend.SubscribeLogsEvent(logsCh)
-		// Subscribe ChainEvent
-		chainEvCh  = make(chan core.ChainEvent, chainEvChanSize)
-		chainEvSub = es.backend.SubscribeChainEvent(chainEvCh)
-	)
-
-	// Unsubscribe all events
-	defer sub.Unsubscribe()
-	defer txSub.Unsubscribe()
-	defer rmLogsSub.Unsubscribe()
-	defer logsSub.Unsubscribe()
-	defer chainEvSub.Unsubscribe()
-
+	// Ensure all subscriptions get cleaned up
+	defer func() {
+		es.pendingLogSub.Unsubscribe()
+		es.txSub.Unsubscribe()
+		es.logsSub.Unsubscribe()
+		es.rmLogsSub.Unsubscribe()
+		es.chainSub.Unsubscribe()
+	}()
+
+	index := make(filterIndex)
 	for i := UnknownSubscription; i < LastIndexSubscription; i++ {
 		index[i] = make(map[rpc.ID]*subscription)
 	}
 
 	for {
 		select {
-		case ev, active := <-sub.Chan():
-			if !active { // system stopped
-				return
-			}
-			es.broadcast(index, ev)
-
 		// Handle subscribed events
-		case ev := <-txCh:
+		case ev := <-es.txCh:
 			es.broadcast(index, ev)
-		case ev := <-rmLogsCh:
+		case ev := <-es.logsCh:
 			es.broadcast(index, ev)
-		case ev := <-logsCh:
+		case ev := <-es.rmLogsCh:
 			es.broadcast(index, ev)
-		case ev := <-chainEvCh:
+		case ev := <-es.chainCh:
+			es.broadcast(index, ev)
+		case ev, active := <-es.pendingLogSub.Chan():
+			if !active { // system stopped
+				return
+			}
 			es.broadcast(index, ev)
 
 		case f := <-es.install:
@@ -467,6 +483,7 @@ func (es *EventSystem) eventLoop() {
 				index[f.typ][f.id] = f
 			}
 			close(f.installed)
+
 		case f := <-es.uninstall:
 			if f.typ == MinedAndPendingLogsSubscription {
 				// the type are logs and pending logs subscriptions
@@ -478,13 +495,13 @@ func (es *EventSystem) eventLoop() {
 			close(f.err)
 
 		// System stopped
-		case <-txSub.Err():
+		case <-es.txSub.Err():
 			return
-		case <-rmLogsSub.Err():
+		case <-es.logsSub.Err():
 			return
-		case <-logsSub.Err():
+		case <-es.rmLogsSub.Err():
 			return
-		case <-chainEvSub.Err():
+		case <-es.chainSub.Err():
 			return
 		}
 	}

event/event.go

@@ -180,6 +180,12 @@ func (s *TypeMuxSubscription) Unsubscribe() {
 	s.closewait()
 }
 
+func (s *TypeMuxSubscription) Closed() bool {
+	s.closeMu.Lock()
+	defer s.closeMu.Unlock()
+	return s.closed
+}
+
 func (s *TypeMuxSubscription) closewait() {
 	s.closeMu.Lock()
 	defer s.closeMu.Unlock()