vendor: Update github.com/syndtr/goleveldb

vendor/github.com/syndtr/goleveldb/leveldb/db_state.go

@@ -67,12 +67,11 @@ func (db *DB) sampleSeek(ikey internalKey) {
 }
 
 func (db *DB) mpoolPut(mem *memdb.DB) {
-	defer func() {
-		recover()
-	}()
-	select {
-	case db.memPool <- mem:
-	default:
+	if !db.isClosed() {
+		select {
+		case db.memPool <- mem:
+		default:
+		}
 	}
 }
 
@@ -101,6 +100,12 @@ func (db *DB) mpoolDrain() {
 			default:
 			}
 		case _, _ = <-db.closeC:
+			ticker.Stop()
+			// Make sure the pool is drained.
+			select {
+			case <-db.memPool:
+			case <-time.After(time.Second):
+			}
 			close(db.memPool)
 			return
 		}
@@ -148,10 +153,11 @@ func (db *DB) newMem(n int) (mem *memDB, err error) {
 func (db *DB) getMems() (e, f *memDB) {
 	db.memMu.RLock()
 	defer db.memMu.RUnlock()
-	if db.mem == nil {
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
 		panic("nil effective mem")
 	}
-	db.mem.incref()
 	if db.frozenMem != nil {
 		db.frozenMem.incref()
 	}
@@ -162,10 +168,11 @@ func (db *DB) getMems() (e, f *memDB) {
 func (db *DB) getEffectiveMem() *memDB {
 	db.memMu.RLock()
 	defer db.memMu.RUnlock()
-	if db.mem == nil {
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
 		panic("nil effective mem")
 	}
-	db.mem.incref()
 	return db.mem
 }
 
@@ -200,6 +207,14 @@ func (db *DB) dropFrozenMem() {
 	db.memMu.Unlock()
 }
 
+// Clear mems ptr; used by DB.Close().
+func (db *DB) clearMems() {
+	db.memMu.Lock()
+	db.mem = nil
+	db.frozenMem = nil
+	db.memMu.Unlock()
+}
+
 // Set closed flag; return true if not already closed.
 func (db *DB) setClosed() bool {
 	return atomic.CompareAndSwapUint32(&db.closed, 0, 1)