From 4696d16ed421fc1ce0fe688e66d88872581a1e5e Mon Sep 17 00:00:00 2001
From: cjepson <info@companyzero.com>
Date: Mon, 30 Mar 2015 13:16:23 -0400
Subject: [PATCH] Fix race in FetchTransactionStore
Because FetchTransactionStore in GetBlockTemplate occasionally accesses
the internal blockchain memory structure while it is being read or modified,
a race can occur. To prevent this, FetchTransactionStore is instead
routed through the internal channel for blockchain requests.
---
blockmanager.go | 30 ++++++++++++++++++++++++++++++
mining.go | 3 +--
2 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/blockmanager.go b/blockmanager.go
index cb72fe2f..1f5250b7 100644
--- a/blockmanager.go
+++ b/blockmanager.go
@@ -107,6 +107,20 @@ type processBlockResponse struct {
err error
}
+// fetchTransactionStoreResponse is a response sent to the reply channel of a
+// fetchTransactionStoreMsg.
+type fetchTransactionStoreResponse struct {
+ TxStore blockchain.TxStore
+ err error
+}
+
+// fetchTransactionStoreMsg is a message type to be sent across the message
+// channel fetching the tx input store for some Tx.
+type fetchTransactionStoreMsg struct {
+ tx *btcutil.Tx
+ reply chan fetchTransactionStoreResponse
+}
+
// processBlockMsg is a message type to be sent across the message channel
// for requested a block is processed. Note this call differs from blockMsg
// above in that blockMsg is intended for blocks that came from peers and have
@@ -1109,6 +1123,13 @@ out:
err: err,
}
+ case fetchTransactionStoreMsg:
+ txStore, err := b.blockChain.FetchTransactionStore(msg.tx)
+ msg.reply <- fetchTransactionStoreResponse{
+ TxStore: txStore,
+ err: err,
+ }
+
case processBlockMsg:
isOrphan, err := b.blockChain.ProcessBlock(
msg.block, b.server.timeSource,
@@ -1371,6 +1392,15 @@ func (b *blockManager) CalcNextRequiredDifficulty(timestamp time.Time) (uint32,
return response.difficulty, response.err
}
+// FetchTransactionStore makes use of FetchTransactionStore on an internal
+// instance of a block chain. It is safe for concurrent access.
+func (b *blockManager) FetchTransactionStore(tx *btcutil.Tx) (blockchain.TxStore, error) {
+ reply := make(chan fetchTransactionStoreResponse, 1)
+ b.msgChan <- fetchTransactionStoreMsg{tx: tx, reply: reply}
+ response := <-reply
+ return response.TxStore, response.err
+}
+
// ProcessBlock makes use of ProcessBlock on an internal instance of a block
// chain. It is funneled through the block manager since btcchain is not safe
// for concurrent access.
diff --git a/mining.go b/mining.go
index 13edafe6..7af39cbd 100644
--- a/mining.go
+++ b/mining.go
@@ -369,7 +369,6 @@ func NewBlockTemplate(mempool *txMemPool, payToAddress btcutil.Address) (*BlockT
blockManager := mempool.server.blockManager
timeSource := mempool.server.timeSource
chainState := &blockManager.chainState
- chain := blockManager.blockChain
// Extend the most recently known best block.
chainState.Lock()
@@ -458,7 +457,7 @@ mempoolLoop:
// inputs from the mempool since a transaction which depends on
// other transactions in the mempool must come after those
// dependencies in the final generated block.
- txStore, err := chain.FetchTransactionStore(tx)
+ txStore, err := blockManager.FetchTransactionStore(tx)
if err != nil {
minrLog.Warnf("Unable to fetch transaction store for "+
"tx %s: %v", tx.Sha(), err)