Merge pull request #4148

18e7216 Push cs_mains down in ProcessBlock (Pieter Wuille)
202e019 Move all post-chaintip-change notifications to ActivateBestChain (Pieter Wuille)
4e0eed8 Allow ActivateBestChain to release its lock on cs_main (Pieter Wuille)
77339e5 Get rid of the static chainMostWork (optimization) (Pieter Wuille)

1 files changed, 120 insertions, 98 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 429473d8f8..16d1cba6ef 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -40,7 +40,6 @@ CTxMemPool mempool;
 
 map<uint256, CBlockIndex*> mapBlockIndex;
 CChain chainActive;
-CChain chainMostWork;
 int64_t nTimeBestReceived = 0;
 int nScriptCheckThreads = 0;
 bool fImporting = false;
@@ -398,6 +397,12 @@ CBlockIndex *CChain::FindFork(const CBlockLocator &locator) const {
     return Genesis();
 }
 
+CBlockIndex *CChain::FindFork(CBlockIndex *pindex) const {
+    while (pindex && !Contains(pindex))
+        pindex = pindex->pprev;
+    return pindex;
+}
+
 CCoinsViewCache *pcoinsTip = NULL;
 CBlockTreeDB *pblocktree = NULL;
 
@@ -1890,6 +1895,11 @@ bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, C
     for (unsigned int i = 0; i < block.vtx.size(); i++)
         g_signals.SyncTransaction(block.GetTxHash(i), block.vtx[i], &block);
 
+    // Watch for changes to the previous coinbase transaction.
+    static uint256 hashPrevBestCoinBase;
+    g_signals.UpdatedTransaction(hashPrevBestCoinBase);
+    hashPrevBestCoinBase = block.GetTxHash(0);
+
     return true;
 }
 
@@ -2035,23 +2045,17 @@ bool static ConnectTip(CValidationState &state, CBlockIndex *pindexNew) {
     return true;
 }
 
-// Make chainMostWork correspond to the chain with the most work in it, that isn't
+// Return the tip of the chain with the most work in it, that isn't
 // known to be invalid (it's however far from certain to be valid).
-void static FindMostWorkChain() {
-    CBlockIndex *pindexNew = NULL;
-
-    // In case the current best is invalid, do not consider it.
-    while (chainMostWork.Tip() && (chainMostWork.Tip()->nStatus & BLOCK_FAILED_MASK)) {
-        setBlockIndexValid.erase(chainMostWork.Tip());
-        chainMostWork.SetTip(chainMostWork.Tip()->pprev);
-    }
-
+static CBlockIndex* FindMostWorkChain() {
     do {
+        CBlockIndex *pindexNew = NULL;
+
         // Find the best candidate header.
         {
             std::set<CBlockIndex*, CBlockIndexWorkComparator>::reverse_iterator it = setBlockIndexValid.rbegin();
             if (it == setBlockIndexValid.rend())
-                return;
+                return NULL;
             pindexNew = *it;
         }
 
@@ -2075,70 +2079,111 @@ void static FindMostWorkChain() {
             }
             pindexTest = pindexTest->pprev;
         }
-        if (fInvalidAncestor)
-            continue;
-
-        break;
+        if (!fInvalidAncestor)
+            return pindexNew;
     } while(true);
-
-    // Check whether it's actually an improvement.
-    if (chainMostWork.Tip() && !CBlockIndexWorkComparator()(chainMostWork.Tip(), pindexNew))
-        return;
-
-    // We have a new best.
-    chainMostWork.SetTip(pindexNew);
 }
 
-// Try to activate to the most-work chain (thereby connecting it).
-bool ActivateBestChain(CValidationState &state) {
-    LOCK(cs_main);
+// Try to make some progress towards making pindexMostWork the active block.
+static bool ActivateBestChainStep(CValidationState &state, CBlockIndex *pindexMostWork) {
+    AssertLockHeld(cs_main);
+    bool fInvalidFound = false;
     CBlockIndex *pindexOldTip = chainActive.Tip();
-    bool fComplete = false;
-    while (!fComplete) {
-        FindMostWorkChain();
-        fComplete = true;
+    CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
 
-        // Check whether we have something to do.
-        if (chainMostWork.Tip() == NULL) break;
+    // Disconnect active blocks which are no longer in the best chain.
+    while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
+        if (!DisconnectTip(state))
+            return false;
+    }
 
-        // Disconnect active blocks which are no longer in the best chain.
-        while (chainActive.Tip() && !chainMostWork.Contains(chainActive.Tip())) {
-            if (!DisconnectTip(state))
-                return false;
-        }
+    // Build list of new blocks to connect.
+    std::vector<CBlockIndex*> vpindexToConnect;
+    vpindexToConnect.reserve(pindexMostWork->nHeight - (pindexFork ? pindexFork->nHeight : -1));
+    while (pindexMostWork && pindexMostWork != pindexFork) {
+        vpindexToConnect.push_back(pindexMostWork);
+        pindexMostWork = pindexMostWork->pprev;
+    }
 
-        // Connect new blocks.
-        while (!chainActive.Contains(chainMostWork.Tip())) {
-            CBlockIndex *pindexConnect = chainMostWork[chainActive.Height() + 1];
-            if (!ConnectTip(state, pindexConnect)) {
-                if (state.IsInvalid()) {
-                    // The block violates a consensus rule.
-                    if (!state.CorruptionPossible())
-                        InvalidChainFound(chainMostWork.Tip());
-                    fComplete = false;
-                    state = CValidationState();
-                    break;
-                } else {
-                    // A system error occurred (disk space, database error, ...).
-                    return false;
-                }
+    // Connect new blocks.
+    BOOST_REVERSE_FOREACH(CBlockIndex *pindexConnect, vpindexToConnect) {
+        if (!ConnectTip(state, pindexConnect)) {
+            if (state.IsInvalid()) {
+                // The block violates a consensus rule.
+                if (!state.CorruptionPossible())
+                    InvalidChainFound(vpindexToConnect.back());
+                state = CValidationState();
+                fInvalidFound = true;
+                break;
+            } else {
+                // A system error occurred (disk space, database error, ...).
+                return false;
+            }
+        } else {
+            if (!pindexOldTip || chainActive.Tip()->nChainWork > pindexOldTip->nChainWork) {
+                // We're in a better position than we were. Return temporarily to release the lock.
+                break;
             }
         }
     }
 
-    if (chainActive.Tip() != pindexOldTip) {
-        std::string strCmd = GetArg("-blocknotify", "");
-        if (!IsInitialBlockDownload() && !strCmd.empty())
+    // Callbacks/notifications for a new best chain.
+    if (fInvalidFound)
+        CheckForkWarningConditionsOnNewFork(vpindexToConnect.back());
+    else
+        CheckForkWarningConditions();
+
+    if (!pblocktree->Flush())
+        return state.Abort(_("Failed to sync block index"));
+
+    return true;
+}
+
+bool ActivateBestChain(CValidationState &state) {
+    CBlockIndex *pindexNewTip = NULL;
+    CBlockIndex *pindexMostWork = NULL;
+    do {
+        boost::this_thread::interruption_point();
+
+        bool fInitialDownload;
         {
-            boost::replace_all(strCmd, "%s", chainActive.Tip()->GetBlockHash().GetHex());
-            boost::thread t(runCommand, strCmd); // thread runs free
+            LOCK(cs_main);
+            pindexMostWork = FindMostWorkChain();
+
+            // Whether we have anything to do at all.
+            if (pindexMostWork == NULL || pindexMostWork == chainActive.Tip())
+                return true;
+
+            if (!ActivateBestChainStep(state, pindexMostWork))
+                return false;
+
+            pindexNewTip = chainActive.Tip();
+            fInitialDownload = IsInitialBlockDownload();
         }
-    }
+        // When we reach this point, we switched to a new tip (stored in pindexNewTip).
+
+        // Notifications/callbacks that can run without cs_main
+        if (!fInitialDownload) {
+            uint256 hashNewTip = pindexNewTip->GetBlockHash();
+            // Relay inventory, but don't relay old inventory during initial block download.
+            int nBlockEstimate = Checkpoints::GetTotalBlocksEstimate();
+            LOCK(cs_vNodes);
+            BOOST_FOREACH(CNode* pnode, vNodes)
+                if (chainActive.Height() > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate))
+                    pnode->PushInventory(CInv(MSG_BLOCK, hashNewTip));
+
+            std::string strCmd = GetArg("-blocknotify", "");
+            if (!strCmd.empty()) {
+                boost::replace_all(strCmd, "%s", hashNewTip.GetHex());
+                boost::thread t(runCommand, strCmd); // thread runs free
+            }
+        }
+        uiInterface.NotifyBlocksChanged();
+    } while(pindexMostWork != chainActive.Tip());
 
     return true;
 }
 
-
 CBlockIndex* AddToBlockIndex(CBlockHeader& block)
 {
     // Check for duplicate
@@ -2198,26 +2243,6 @@ bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBl
     if (!pblocktree->WriteBlockIndex(CDiskBlockIndex(pindexNew)))
         return state.Abort(_("Failed to write block index"));
 
-    // New best?
-    if (!ActivateBestChain(state))
-        return false;
-
-    LOCK(cs_main);
-    if (pindexNew == chainActive.Tip())
-    {
-        // Clear fork warning if its no longer applicable
-        CheckForkWarningConditions();
-        // Notify UI to display prev block's coinbase if it was ours
-        static uint256 hashPrevBestCoinBase;
-        g_signals.UpdatedTransaction(hashPrevBestCoinBase);
-        hashPrevBestCoinBase = block.GetTxHash(0);
-    } else
-        CheckForkWarningConditionsOnNewFork(pindexNew);
-
-    if (!pblocktree->Flush())
-        return state.Abort(_("Failed to sync block index"));
-
-    uiInterface.NotifyBlocksChanged();
     return true;
 }
 
@@ -2494,7 +2519,6 @@ bool AcceptBlock(CBlock& block, CValidationState& state, CBlockIndex** ppindex,
     }
 
     int nHeight = pindex->nHeight;
-    uint256 hash = pindex->GetBlockHash();
 
     // Check that all transactions are finalized
     BOOST_FOREACH(const CTransaction& tx, block.vtx)
@@ -2538,16 +2562,6 @@ bool AcceptBlock(CBlock& block, CValidationState& state, CBlockIndex** ppindex,
         return state.Abort(_("System error: ") + e.what());
     }
 
-    // Relay inventory, but don't relay old inventory during initial block download
-    int nBlockEstimate = Checkpoints::GetTotalBlocksEstimate();
-    if (chainActive.Tip()->GetBlockHash() == hash)
-    {
-        LOCK(cs_vNodes);
-        BOOST_FOREACH(CNode* pnode, vNodes)
-            if (chainActive.Height() > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate))
-                pnode->PushInventory(CInv(MSG_BLOCK, hash));
-    }
-
     return true;
 }
 
@@ -2577,10 +2591,11 @@ void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd)
 
 bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBlockPos *dbp)
 {
-    AssertLockHeld(cs_main);
-
     // Check for duplicate
     uint256 hash = pblock->GetHash();
+
+    {
+    LOCK(cs_main);
     if (mapBlockIndex.count(hash))
         return state.Invalid(error("ProcessBlock() : already have block %d %s", mapBlockIndex[hash]->nHeight, hash.ToString()), 0, "duplicate");
     if (mapOrphanBlocks.count(hash))
@@ -2649,7 +2664,11 @@ bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBl
         mapOrphanBlocksByPrev.erase(hashPrev);
     }
 
-    LogPrintf("ProcessBlock: ACCEPTED\n");
+    }
+
+    if (!ActivateBestChain(state))
+        return error("ProcessBlock() : ActivateBestChain failed");
+
     return true;
 }
 
@@ -3085,6 +3104,8 @@ bool InitBlockIndex() {
             CBlockIndex *pindex = AddToBlockIndex(block);
             if (!ReceivedBlockTransactions(block, state, pindex, blockPos))
                 return error("LoadBlockIndex() : genesis block not accepted");
+            if (!ActivateBestChain(state))
+                return error("LoadBlockIndex() : genesis block cannot be activated");
         } catch(std::runtime_error &e) {
             return error("LoadBlockIndex() : failed to initialize block database: %s", e.what());
         }
@@ -3214,7 +3235,6 @@ bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
 
                 // process block
                 if (nBlockPos >= nStartByte) {
-                    LOCK(cs_main);
                     if (dbp)
                         dbp->nPos = nBlockPos;
                     CValidationState state;
@@ -3903,10 +3923,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         CInv inv(MSG_BLOCK, block.GetHash());
         pfrom->AddInventoryKnown(inv);
 
-        LOCK(cs_main);
-        // Remember who we got this block from.
-        mapBlockSource[inv.hash] = pfrom->GetId();
-        MarkBlockAsReceived(inv.hash, pfrom->GetId());
+        {
+            LOCK(cs_main);
+            // Remember who we got this block from.
+            mapBlockSource[inv.hash] = pfrom->GetId();
+            MarkBlockAsReceived(inv.hash, pfrom->GetId());
+        }
 
         CValidationState state;
         ProcessBlock(state, pfrom, &block);