Merge pull request #13875 from ahrtr/be_race

fix WARNING: DATA RACE issue when multiple goroutines access the backend

server/etcdserver/adapters.go

@@ -74,6 +74,10 @@ func (s *serverVersionAdapter) GetMembersVersions() map[string]*version.Versions
 }
 
 func (s *serverVersionAdapter) GetStorageVersion() *semver.Version {
+	// `applySnapshot` sets a new backend instance, so we need to acquire the bemu lock.
+	s.bemu.RLock()
+	defer s.bemu.RUnlock()
+
 	tx := s.be.BatchTx()
 	tx.Lock()
 	defer tx.Unlock()
@@ -85,6 +89,10 @@ func (s *serverVersionAdapter) GetStorageVersion() *semver.Version {
 }
 
 func (s *serverVersionAdapter) UpdateStorageVersion(target semver.Version) error {
+	// `applySnapshot` sets a new backend instance, so we need to acquire the bemu lock.
+	s.bemu.RLock()
+	defer s.bemu.RUnlock()
+
 	tx := s.be.BatchTx()
 	tx.Lock()
 	defer tx.Unlock()

server/etcdserver/server.go

@@ -256,7 +256,7 @@ type EtcdServer struct {
 
 	kv         mvcc.WatchableKV
 	lessor     lease.Lessor
-	bemu       sync.Mutex
+	bemu       sync.RWMutex
 	be         backend.Backend
 	beHooks    *serverstorage.BackendHooks
 	authStore  auth.AuthStore
@@ -2229,8 +2229,8 @@ func (s *EtcdServer) parseProposeCtxErr(err error, start time.Time) error {
 
 func (s *EtcdServer) KV() mvcc.WatchableKV { return s.kv }
 func (s *EtcdServer) Backend() backend.Backend {
-	s.bemu.Lock()
-	defer s.bemu.Unlock()
+	s.bemu.RLock()
+	defer s.bemu.RUnlock()
 	return s.be
 }
 

server/etcdserver/v3_server.go

@@ -237,7 +237,11 @@ func (s *EtcdServer) Compact(ctx context.Context, r *pb.CompactionRequest) (*pb.
 		// the hash may revert to a hash prior to compaction completing
 		// if the compaction resumes. Force the finished compaction to
 		// commit so it won't resume following a crash.
+		//
+		// `applySnapshot` sets a new backend instance, so we need to acquire the bemu lock.
+		s.bemu.RLock()
 		s.be.ForceCommit()
+		s.bemu.RUnlock()
 		trace.Step("physically apply compaction")
 	}
 	if err != nil {

server/storage/backend/backend.go

@@ -419,6 +419,8 @@ func (b *backend) run() {
 func (b *backend) Close() error {
 	close(b.stopc)
 	<-b.donec
+	b.mu.Lock()
+	defer b.mu.Unlock()
 	return b.db.Close()
 }