Revert "fix deadlock and goroutine leak in chunk restore (pingcap#149)…

…" (pingcap#152)

This reverts commit 852c5e9.

lightning/restore/restore.go

@@ -1399,25 +1399,8 @@ func (cr *chunkRestore) restore(
 	}
 	block.cond = sync.NewCond(new(sync.Mutex))
 	deliverCompleteCh := make(chan error, 1)
-	deliveryClosedCh, deliveryCancel := context.WithCancel(ctx)
-
-	deliveryExitFn := func() {
-		deliveryCancel()
-		block.cond.Signal()
-	}
-
-	encodeExitFn := func() {
-		block.cond.L.Lock()
-		block.encodeCompleted = true
-		block.cond.Signal()
-		block.cond.L.Unlock()
-	}
-
-	defer encodeExitFn()
 
 	go func() {
-		defer deliveryExitFn()
-
 		var dataKVs, indexKVs []kvenc.KvPair
 		for {
 			block.cond.L.Lock()
@@ -1531,13 +1514,10 @@ func (cr *chunkRestore) restore(
 	}()
 
 	var buffer bytes.Buffer
-encodeLoop:
 	for {
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
-		case <-deliveryClosedCh.Done():
-			break encodeLoop
 		default:
 		}
 
@@ -1625,7 +1605,10 @@ encodeLoop:
 		block.cond.L.Unlock()
 	}
 
-	encodeExitFn()
+	block.cond.L.Lock()
+	block.encodeCompleted = true
+	block.cond.Signal()
+	block.cond.L.Unlock()
 
 	select {
 	case err := <-deliverCompleteCh: