4 files changed, 17 insertions, 46 deletions

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index f33aa334a..fb023c7dd 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -144,18 +144,8 @@ func (d *Downloader) Synchronise(id string, hash common.Hash) error {
 }
 
 // TakeBlocks takes blocks from the queue and yields them to the caller.
-func (d *Downloader) TakeBlocks() (types.Blocks, error) {
-	// If the head block is missing, no blocks are ready
-	head := d.queue.GetHeadBlock()
-	if head == nil {
-		return nil, nil
-	}
-	// If the parent hash of the head is unknown, notify the caller
-	if !d.hasBlock(head.ParentHash()) {
-		return nil, ErrUnknownParent
-	}
-	// Otherwise retrieve a full batch of blocks
-	return d.queue.TakeBlocks(head), nil
+func (d *Downloader) TakeBlocks() types.Blocks {
+	return d.queue.TakeBlocks()
 }
 
 func (d *Downloader) Has(hash common.Hash) bool {
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index c3d1b2e00..2a95b3d8e 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -197,10 +197,7 @@ func TestTaking(t *testing.T) {
 	if err != nil {
 		t.Error("download error", err)
 	}
-	bs, err := tester.downloader.TakeBlocks()
-	if err != nil {
-		t.Fatalf("failed to take blocks: %v", err)
-	}
+	bs := tester.downloader.TakeBlocks()
 	if len(bs) != targetBlocks {
 		t.Error("retrieved block mismatch: have %v, want %v", len(bs), targetBlocks)
 	}
@@ -280,8 +277,7 @@ func TestThrottling(t *testing.T) {
 				time.Sleep(time.Millisecond)
 			}
 			// Take a batch of blocks and accumulate
-			blocks, _ := tester.downloader.TakeBlocks()
-			took = append(took, blocks...)
+			took = append(took, tester.downloader.TakeBlocks()...)
 		}
 		done <- struct{}{}
 	}()
@@ -315,14 +311,13 @@ func TestNonExistingParentAttack(t *testing.T) {
 	if err := tester.sync("attack", hashes[0]); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
-	bs, err := tester.downloader.TakeBlocks()
-	if err != ErrUnknownParent {
-		t.Fatalf("take error mismatch: have %v, want %v", err, ErrUnknownParent)
+	bs := tester.downloader.TakeBlocks()
+	if len(bs) != 1 {
+		t.Fatalf("retrieved block mismatch: have %v, want %v", len(bs), 1)
 	}
-	if len(bs) != 0 {
-		t.Error("retrieved block mismatch: have %v, want %v", len(bs), 0)
+	if tester.hasBlock(bs[0].ParentHash()) {
+		t.Fatalf("tester knows about the unknown hash")
 	}
-	// Cancel the download due to the parent attack
 	tester.downloader.Cancel()
 
 	// Reconstruct a valid chain, and try to synchronize with it
@@ -331,11 +326,8 @@ func TestNonExistingParentAttack(t *testing.T) {
 	if err := tester.sync("valid", hashes[0]); err != nil {
 		t.Fatalf("failed to synchronise blocks: %v", err)
 	}
-	bs, err = tester.downloader.TakeBlocks()
-	if err != nil {
-		t.Fatalf("failed to retrieve blocks: %v", err)
-	}
+	bs = tester.downloader.TakeBlocks()
 	if len(bs) != 1 {
-		t.Error("retrieved block mismatch: have %v, want %v", len(bs), 1)
+		t.Fatalf("retrieved block mismatch: have %v, want %v", len(bs), 1)
 	}
 }
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index 40749698c..6ad915757 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -172,17 +172,11 @@ func (q *queue) GetBlock(hash common.Hash) *types.Block {
 }
 
 // TakeBlocks retrieves and permanently removes a batch of blocks from the cache.
-// The head parameter is required to prevent a race condition where concurrent
-// takes may fail parent verifications.
-func (q *queue) TakeBlocks(head *types.Block) types.Blocks {
+func (q *queue) TakeBlocks() types.Blocks {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
-	// Short circuit if the head block's different
-	if len(q.blockCache) == 0 || q.blockCache[0] != head {
-		return nil
-	}
-	// Otherwise accumulate all available blocks
+	// Accumulate all available blocks
 	var blocks types.Blocks
 	for _, block := range q.blockCache {
 		if block == nil {
diff --git a/eth/sync.go b/eth/sync.go
index b51fb7c10..c89f34596 100644
--- a/eth/sync.go
+++ b/eth/sync.go
@@ -40,9 +40,7 @@ func (pm *ProtocolManager) update() {
 			// Try to pull some blocks from the downloaded
 			if atomic.CompareAndSwapInt32(&blockProcPend, 0, 1) {
 				go func() {
-					if err := pm.processBlocks(); err != nil {
-						pm.downloader.Cancel()
-					}
+					pm.processBlocks()
 					atomic.StoreInt32(&blockProcPend, 0)
 				}()
 			}
@@ -61,12 +59,8 @@ func (pm *ProtocolManager) processBlocks() error {
 	pm.wg.Add(1)
 	defer pm.wg.Done()
 
-	// Take a batch of blocks, but abort if there's an invalid head or if the chain's empty
-	blocks, err := pm.downloader.TakeBlocks()
-	if err != nil {
-		glog.V(logger.Warn).Infof("Block processing failed: %v", err)
-		return err
-	}
+	// Short circuit if no blocks are available for insertion
+	blocks := pm.downloader.TakeBlocks()
 	if len(blocks) == 0 {
 		return nil
 	}
@@ -77,6 +71,7 @@ func (pm *ProtocolManager) processBlocks() error {
 		_, err := pm.chainman.InsertChain(blocks[:max])
 		if err != nil {
 			glog.V(logger.Warn).Infof("Block insertion failed: %v", err)
+			pm.downloader.Cancel()
 			return err
 		}
 		blocks = blocks[max:]