netsync: Remove unneeded ForceReorganization.

This removes the ForceReorganization method and infrastructure from the
sync manager as it is no longer needed since the blockchain is safe for
concurrent access and the additional mempool pruning the version in sync
manager currently does is not necessary since all siblings that could be
the target of a head reorganization are necessarily at the same height
and have the same stake difficulty.

internal/netsync/manager.go

@@ -136,21 +136,6 @@ type tipGenerationMsg struct {
 	reply chan tipGenerationResponse
 }
 
-// forceReorganizationResponse is a response sent to the reply channel of a
-// forceReorganizationMsg query.
-type forceReorganizationResponse struct {
-	err error
-}
-
-// forceReorganizationMsg is a message type to be sent across the message
-// channel for requesting that the block on head be reorganized to one of its
-// adjacent orphans.
-type forceReorganizationMsg struct {
-	formerBest chainhash.Hash
-	newBest    chainhash.Hash
-	reply      chan forceReorganizationResponse
-}
-
 // processBlockResponse is a response sent to the reply channel of a
 // processBlockMsg.
 type processBlockResponse struct {
@@ -1598,22 +1583,6 @@ out:
 					err: err,
 				}
 
-			case forceReorganizationMsg:
-				err := m.cfg.Chain.ForceHeadReorganization(
-					msg.formerBest, msg.newBest)
-
-				if err == nil {
-					// Prune invalidated transactions.
-					best := m.cfg.Chain.BestSnapshot()
-					m.cfg.TxMemPool.PruneStakeTx(best.NextStakeDiff,
-						best.Height)
-					m.cfg.TxMemPool.PruneExpiredTx()
-				}
-
-				msg.reply <- forceReorganizationResponse{
-					err: err,
-				}
-
 			case tipGenerationMsg:
 				g, err := m.cfg.Chain.TipGeneration()
 				msg.reply <- tipGenerationResponse{
@@ -1868,20 +1837,6 @@ func (m *SyncManager) requestFromPeer(p *peerpkg.Peer, blocks, txs []*chainhash.
 	return nil
 }
 
-// ForceReorganization forces a reorganization of the block chain to the block
-// hash requested, so long as it matches up with the current organization of the
-// best chain.  It is funneled through the sync manager since blockchain is not
-// safe for concurrent access.
-func (m *SyncManager) ForceReorganization(formerBest, newBest chainhash.Hash) error {
-	reply := make(chan forceReorganizationResponse)
-	m.msgChan <- forceReorganizationMsg{
-		formerBest: formerBest,
-		newBest:    newBest,
-		reply:      reply}
-	response := <-reply
-	return response.err
-}
-
 // TipGeneration returns the hashes of all the children of the current best
 // chain tip.  It is funneled through the sync manager since blockchain is not
 // safe for concurrent access.

server.go

@@ -3731,7 +3731,7 @@ func newServer(ctx context.Context, listenAddrs []string, db database.DB, chainP
 				return blockchain.ValidateTransactionScripts(tx, utxoView, flags,
 					s.sigCache)
 			},
-			ForceReorganization: s.syncManager.ForceReorganization,
+			ForceReorganization: s.chain.ForceHeadReorganization,
 		})
 
 		s.bg = mining.NewBgBlkTmplGenerator(&mining.BgBlkTmplConfig{