core/syncer: fix a bug in ForceSync (#499)

1 files changed, 8 insertions, 5 deletions

diff --git a/core/syncer/consensus.go b/core/syncer/consensus.go
index f2f8f9e..8d89d07 100644
--- a/core/syncer/consensus.go
+++ b/core/syncer/consensus.go
@@ -263,11 +263,14 @@ func (con *Consensus) ForceSync(skip bool) {
 	con.setupConfigsUntilRound(block.Position.Round + core.ConfigRoundShift - 1)
 	con.syncedLastBlock = &block
 	con.stopBuffering()
-	con.dummyCancel, con.dummyFinished = utils.LaunchDummyReceiver(
-		context.Background(), con.network.ReceiveChan(),
-		func(msg interface{}) {
-			con.dummyMsgBuffer = append(con.dummyMsgBuffer, msg)
-		})
+	// We might call stopBuffering without calling assureBuffering.
+	if con.dummyCancel == nil {
+		con.dummyCancel, con.dummyFinished = utils.LaunchDummyReceiver(
+			context.Background(), con.network.ReceiveChan(),
+			func(msg interface{}) {
+				con.dummyMsgBuffer = append(con.dummyMsgBuffer, msg)
+			})
+	}
 	con.syncedSkipNext = skip
 }