Avoid pemanent cs_main/cs_wallet lock during wallet rescans

3 files changed, 245 insertions, 194 deletions

diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 645e776b68..1711b400e3 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -101,61 +101,60 @@ UniValue importprivkey(const JSONRPCRequest& request)
         );
 
 
-    LOCK2(cs_main, pwallet->cs_wallet);
-
-    EnsureWalletIsUnlocked(pwallet);
-
-    std::string strSecret = request.params[0].get_str();
-    std::string strLabel = "";
-    if (!request.params[1].isNull())
-        strLabel = request.params[1].get_str();
-
-    // Whether to perform rescan after import
     bool fRescan = true;
-    if (!request.params[2].isNull())
-        fRescan = request.params[2].get_bool();
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
 
-    if (fRescan && fPruneMode)
-        throw JSONRPCError(RPC_WALLET_ERROR, "Rescan is disabled in pruned mode");
+        EnsureWalletIsUnlocked(pwallet);
 
-    CBitcoinSecret vchSecret;
-    bool fGood = vchSecret.SetString(strSecret);
+        std::string strSecret = request.params[0].get_str();
+        std::string strLabel = "";
+        if (!request.params[1].isNull())
+            strLabel = request.params[1].get_str();
 
-    if (!fGood) throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key encoding");
+        // Whether to perform rescan after import
+        if (!request.params[2].isNull())
+            fRescan = request.params[2].get_bool();
 
-    CKey key = vchSecret.GetKey();
-    if (!key.IsValid()) throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Private key outside allowed range");
+        if (fRescan && fPruneMode)
+            throw JSONRPCError(RPC_WALLET_ERROR, "Rescan is disabled in pruned mode");
 
-    CPubKey pubkey = key.GetPubKey();
-    assert(key.VerifyPubKey(pubkey));
-    CKeyID vchAddress = pubkey.GetID();
-    {
-        pwallet->MarkDirty();
+        CBitcoinSecret vchSecret;
+        bool fGood = vchSecret.SetString(strSecret);
 
-        // We don't know which corresponding address will be used; label them all
-        for (const auto& dest : GetAllDestinationsForKey(pubkey)) {
-            pwallet->SetAddressBook(dest, strLabel, "receive");
-        }
+        if (!fGood) throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key encoding");
 
-        // Don't throw error in case a key is already there
-        if (pwallet->HaveKey(vchAddress)) {
-            return NullUniValue;
-        }
+        CKey key = vchSecret.GetKey();
+        if (!key.IsValid()) throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Private key outside allowed range");
 
-        pwallet->mapKeyMetadata[vchAddress].nCreateTime = 1;
+        CPubKey pubkey = key.GetPubKey();
+        assert(key.VerifyPubKey(pubkey));
+        CKeyID vchAddress = pubkey.GetID();
+        {
+            pwallet->MarkDirty();
+            // We don't know which corresponding address will be used; label them all
+            for (const auto& dest : GetAllDestinationsForKey(pubkey)) {
+                pwallet->SetAddressBook(dest, strLabel, "receive");
+            }
 
-        if (!pwallet->AddKeyPubKey(key, pubkey)) {
-            throw JSONRPCError(RPC_WALLET_ERROR, "Error adding key to wallet");
-        }
-        pwallet->LearnAllRelatedScripts(pubkey);
+            // Don't throw error in case a key is already there
+            if (pwallet->HaveKey(vchAddress)) {
+                return NullUniValue;
+            }
 
-        // whenever a key is imported, we need to scan the whole chain
-        pwallet->UpdateTimeFirstKey(1);
+            // whenever a key is imported, we need to scan the whole chain
+            pwallet->UpdateTimeFirstKey(1);
+            pwallet->mapKeyMetadata[vchAddress].nCreateTime = 1;
 
-        if (fRescan) {
-            pwallet->RescanFromTime(TIMESTAMP_MIN, true /* update */);
+            if (!pwallet->AddKeyPubKey(key, pubkey)) {
+                throw JSONRPCError(RPC_WALLET_ERROR, "Error adding key to wallet");
+            }
+            pwallet->LearnAllRelatedScripts(pubkey);
         }
     }
+    if (fRescan) {
+        pwallet->RescanFromTime(TIMESTAMP_MIN, true /* update */);
+    }
 
     return NullUniValue;
 }
@@ -268,21 +267,22 @@ UniValue importaddress(const JSONRPCRequest& request)
     if (!request.params[3].isNull())
         fP2SH = request.params[3].get_bool();
 
-    LOCK2(cs_main, pwallet->cs_wallet);
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
 
-    CTxDestination dest = DecodeDestination(request.params[0].get_str());
-    if (IsValidDestination(dest)) {
-        if (fP2SH) {
-            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Cannot use the p2sh flag with an address - use a script instead");
+        CTxDestination dest = DecodeDestination(request.params[0].get_str());
+        if (IsValidDestination(dest)) {
+            if (fP2SH) {
+                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Cannot use the p2sh flag with an address - use a script instead");
+            }
+            ImportAddress(pwallet, dest, strLabel);
+        } else if (IsHex(request.params[0].get_str())) {
+            std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
+            ImportScript(pwallet, CScript(data.begin(), data.end()), strLabel, fP2SH);
+        } else {
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address or script");
         }
-        ImportAddress(pwallet, dest, strLabel);
-    } else if (IsHex(request.params[0].get_str())) {
-        std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
-        ImportScript(pwallet, CScript(data.begin(), data.end()), strLabel, fP2SH);
-    } else {
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address or script");
     }
-
     if (fRescan)
     {
         pwallet->RescanFromTime(TIMESTAMP_MIN, true /* update */);
@@ -436,14 +436,15 @@ UniValue importpubkey(const JSONRPCRequest& request)
     if (!pubKey.IsFullyValid())
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey is not a valid public key");
 
-    LOCK2(cs_main, pwallet->cs_wallet);
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
 
-    for (const auto& dest : GetAllDestinationsForKey(pubKey)) {
-        ImportAddress(pwallet, dest, strLabel);
+        for (const auto& dest : GetAllDestinationsForKey(pubKey)) {
+            ImportAddress(pwallet, dest, strLabel);
+        }
+        ImportScript(pwallet, GetScriptForRawPubKey(pubKey), strLabel, false);
+        pwallet->LearnAllRelatedScripts(pubKey);
     }
-    ImportScript(pwallet, GetScriptForRawPubKey(pubKey), strLabel, false);
-    pwallet->LearnAllRelatedScripts(pubKey);
-
     if (fRescan)
     {
         pwallet->RescanFromTime(TIMESTAMP_MIN, true /* update */);
@@ -479,90 +480,92 @@ UniValue importwallet(const JSONRPCRequest& request)
     if (fPruneMode)
         throw JSONRPCError(RPC_WALLET_ERROR, "Importing wallets is disabled in pruned mode");
 
-    LOCK2(cs_main, pwallet->cs_wallet);
+    int64_t nTimeBegin = 0;
+    bool fGood = true;
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
 
-    EnsureWalletIsUnlocked(pwallet);
+        EnsureWalletIsUnlocked(pwallet);
 
-    std::ifstream file;
-    file.open(request.params[0].get_str().c_str(), std::ios::in | std::ios::ate);
-    if (!file.is_open())
-        throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
+        std::ifstream file;
+        file.open(request.params[0].get_str().c_str(), std::ios::in | std::ios::ate);
+        if (!file.is_open()) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
+        }
+        nTimeBegin = chainActive.Tip()->GetBlockTime();
 
-    int64_t nTimeBegin = chainActive.Tip()->GetBlockTime();
+        int64_t nFilesize = std::max((int64_t)1, (int64_t)file.tellg());
+        file.seekg(0, file.beg);
 
-    bool fGood = true;
+        pwallet->ShowProgress(_("Importing..."), 0); // show progress dialog in GUI
+        while (file.good()) {
+            pwallet->ShowProgress("", std::max(1, std::min(99, (int)(((double)file.tellg() / (double)nFilesize) * 100))));
+            std::string line;
+            std::getline(file, line);
+            if (line.empty() || line[0] == '#')
+                continue;
 
-    int64_t nFilesize = std::max((int64_t)1, (int64_t)file.tellg());
-    file.seekg(0, file.beg);
-
-    pwallet->ShowProgress(_("Importing..."), 0); // show progress dialog in GUI
-    while (file.good()) {
-        pwallet->ShowProgress("", std::max(1, std::min(99, (int)(((double)file.tellg() / (double)nFilesize) * 100))));
-        std::string line;
-        std::getline(file, line);
-        if (line.empty() || line[0] == '#')
-            continue;
-
-        std::vector<std::string> vstr;
-        boost::split(vstr, line, boost::is_any_of(" "));
-        if (vstr.size() < 2)
-            continue;
-        CBitcoinSecret vchSecret;
-        if (vchSecret.SetString(vstr[0])) {
-            CKey key = vchSecret.GetKey();
-            CPubKey pubkey = key.GetPubKey();
-            assert(key.VerifyPubKey(pubkey));
-            CKeyID keyid = pubkey.GetID();
-            if (pwallet->HaveKey(keyid)) {
-                LogPrintf("Skipping import of %s (key already present)\n", EncodeDestination(keyid));
+            std::vector<std::string> vstr;
+            boost::split(vstr, line, boost::is_any_of(" "));
+            if (vstr.size() < 2)
                 continue;
-            }
-            int64_t nTime = DecodeDumpTime(vstr[1]);
-            std::string strLabel;
-            bool fLabel = true;
-            for (unsigned int nStr = 2; nStr < vstr.size(); nStr++) {
-                if (boost::algorithm::starts_with(vstr[nStr], "#"))
-                    break;
-                if (vstr[nStr] == "change=1")
-                    fLabel = false;
-                if (vstr[nStr] == "reserve=1")
-                    fLabel = false;
-                if (boost::algorithm::starts_with(vstr[nStr], "label=")) {
-                    strLabel = DecodeDumpString(vstr[nStr].substr(6));
-                    fLabel = true;
+            CBitcoinSecret vchSecret;
+            if (vchSecret.SetString(vstr[0])) {
+                CKey key = vchSecret.GetKey();
+                CPubKey pubkey = key.GetPubKey();
+                assert(key.VerifyPubKey(pubkey));
+                CKeyID keyid = pubkey.GetID();
+                if (pwallet->HaveKey(keyid)) {
+                    LogPrintf("Skipping import of %s (key already present)\n", EncodeDestination(keyid));
+                    continue;
                 }
+                int64_t nTime = DecodeDumpTime(vstr[1]);
+                std::string strLabel;
+                bool fLabel = true;
+                for (unsigned int nStr = 2; nStr < vstr.size(); nStr++) {
+                    if (boost::algorithm::starts_with(vstr[nStr], "#"))
+                        break;
+                    if (vstr[nStr] == "change=1")
+                        fLabel = false;
+                    if (vstr[nStr] == "reserve=1")
+                        fLabel = false;
+                    if (boost::algorithm::starts_with(vstr[nStr], "label=")) {
+                        strLabel = DecodeDumpString(vstr[nStr].substr(6));
+                        fLabel = true;
+                    }
+                }
+                LogPrintf("Importing %s...\n", EncodeDestination(keyid));
+                if (!pwallet->AddKeyPubKey(key, pubkey)) {
+                    fGood = false;
+                    continue;
+                }
+                pwallet->mapKeyMetadata[keyid].nCreateTime = nTime;
+                if (fLabel)
+                    pwallet->SetAddressBook(keyid, strLabel, "receive");
+                nTimeBegin = std::min(nTimeBegin, nTime);
+            } else if(IsHex(vstr[0])) {
+               std::vector<unsigned char> vData(ParseHex(vstr[0]));
+               CScript script = CScript(vData.begin(), vData.end());
+               if (pwallet->HaveCScript(script)) {
+                   LogPrintf("Skipping import of %s (script already present)\n", vstr[0]);
+                   continue;
+               }
+               if(!pwallet->AddCScript(script)) {
+                   LogPrintf("Error importing script %s\n", vstr[0]);
+                   fGood = false;
+                   continue;
+               }
+               int64_t birth_time = DecodeDumpTime(vstr[1]);
+               if (birth_time > 0) {
+                   pwallet->m_script_metadata[CScriptID(script)].nCreateTime = birth_time;
+                   nTimeBegin = std::min(nTimeBegin, birth_time);
+               }
             }
-            LogPrintf("Importing %s...\n", EncodeDestination(keyid));
-            if (!pwallet->AddKeyPubKey(key, pubkey)) {
-                fGood = false;
-                continue;
-            }
-            pwallet->mapKeyMetadata[keyid].nCreateTime = nTime;
-            if (fLabel)
-                pwallet->SetAddressBook(keyid, strLabel, "receive");
-            nTimeBegin = std::min(nTimeBegin, nTime);
-        } else if(IsHex(vstr[0])) {
-           std::vector<unsigned char> vData(ParseHex(vstr[0]));
-           CScript script = CScript(vData.begin(), vData.end());
-           if (pwallet->HaveCScript(script)) {
-               LogPrintf("Skipping import of %s (script already present)\n", vstr[0]);
-               continue;
-           }
-           if(!pwallet->AddCScript(script)) {
-               LogPrintf("Error importing script %s\n", vstr[0]);
-               fGood = false;
-               continue;
-           }
-           int64_t birth_time = DecodeDumpTime(vstr[1]);
-           if (birth_time > 0) {
-               pwallet->m_script_metadata[CScriptID(script)].nCreateTime = birth_time;
-               nTimeBegin = std::min(nTimeBegin, birth_time);
-           }
         }
+        file.close();
+        pwallet->ShowProgress("", 100); // hide progress dialog in GUI
+        pwallet->UpdateTimeFirstKey(nTimeBegin);
     }
-    file.close();
-    pwallet->ShowProgress("", 100); // hide progress dialog in GUI
-    pwallet->UpdateTimeFirstKey(nTimeBegin);
     pwallet->RescanFromTime(nTimeBegin, false /* update */);
     pwallet->MarkDirty();
 
@@ -685,7 +688,7 @@ UniValue dumpwallet(const JSONRPCRequest& request)
     file << strprintf("#   mined on %s\n", EncodeDumpTime(chainActive.Tip()->GetBlockTime()));
     file << "\n";
 
-    // add the base58check encoded extended master if the wallet uses HD 
+    // add the base58check encoded extended master if the wallet uses HD
     CKeyID masterKeyID = pwallet->GetHDChain().masterKeyID;
     if (!masterKeyID.IsNull())
     {
@@ -1135,47 +1138,48 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
         }
     }
 
-    LOCK2(cs_main, pwallet->cs_wallet);
-    EnsureWalletIsUnlocked(pwallet);
-
-    // Verify all timestamps are present before importing any keys.
-    const int64_t now = chainActive.Tip() ? chainActive.Tip()->GetMedianTimePast() : 0;
-    for (const UniValue& data : requests.getValues()) {
-        GetImportTimestamp(data, now);
-    }
-
+    int64_t now = 0;
     bool fRunScan = false;
-    const int64_t minimumTimestamp = 1;
     int64_t nLowestTimestamp = 0;
-
-    if (fRescan && chainActive.Tip()) {
-        nLowestTimestamp = chainActive.Tip()->GetBlockTime();
-    } else {
-        fRescan = false;
-    }
-
     UniValue response(UniValue::VARR);
+    {
+        LOCK2(cs_main, pwallet->cs_wallet);
+        EnsureWalletIsUnlocked(pwallet);
 
-    for (const UniValue& data : requests.getValues()) {
-        const int64_t timestamp = std::max(GetImportTimestamp(data, now), minimumTimestamp);
-        const UniValue result = ProcessImport(pwallet, data, timestamp);
-        response.push_back(result);
-
-        if (!fRescan) {
-            continue;
+        // Verify all timestamps are present before importing any keys.
+        now = chainActive.Tip() ? chainActive.Tip()->GetMedianTimePast() : 0;
+        for (const UniValue& data : requests.getValues()) {
+            GetImportTimestamp(data, now);
         }
 
-        // If at least one request was successful then allow rescan.
-        if (result["success"].get_bool()) {
-            fRunScan = true;
+        const int64_t minimumTimestamp = 1;
+
+        if (fRescan && chainActive.Tip()) {
+            nLowestTimestamp = chainActive.Tip()->GetBlockTime();
+        } else {
+            fRescan = false;
         }
 
-        // Get the lowest timestamp.
-        if (timestamp < nLowestTimestamp) {
-            nLowestTimestamp = timestamp;
+        for (const UniValue& data : requests.getValues()) {
+            const int64_t timestamp = std::max(GetImportTimestamp(data, now), minimumTimestamp);
+            const UniValue result = ProcessImport(pwallet, data, timestamp);
+            response.push_back(result);
+
+            if (!fRescan) {
+                continue;
+            }
+
+            // If at least one request was successful then allow rescan.
+            if (result["success"].get_bool()) {
+                fRunScan = true;
+            }
+
+            // Get the lowest timestamp.
+            if (timestamp < nLowestTimestamp) {
+                nLowestTimestamp = timestamp;
+            }
         }
     }
-
     if (fRescan && fRunScan && requests.size()) {
         int64_t scannedTime = pwallet->RescanFromTime(nLowestTimestamp, true /* update */);
         pwallet->ReacceptWalletTransactions();
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index e307623fd5..bc0d544aab 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3398,30 +3398,40 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
             );
     }
 
-    LOCK2(cs_main, pwallet->cs_wallet);
+    if (pwallet->IsScanning()) {
+        throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
+    }
 
-    CBlockIndex *pindexStart = chainActive.Genesis();
+    CBlockIndex *pindexStart = nullptr;
     CBlockIndex *pindexStop = nullptr;
-    if (!request.params[0].isNull()) {
-        pindexStart = chainActive[request.params[0].get_int()];
-        if (!pindexStart) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid start_height");
-        }
-    }
+    CBlockIndex *pChainTip = nullptr;
+    {
+        LOCK(cs_main);
+        pindexStart = chainActive.Genesis();
+        pChainTip = chainActive.Tip();
 
-    if (!request.params[1].isNull()) {
-        pindexStop = chainActive[request.params[1].get_int()];
-        if (!pindexStop) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid stop_height");
+        if (!request.params[0].isNull()) {
+            pindexStart = chainActive[request.params[0].get_int()];
+            if (!pindexStart) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid start_height");
+            }
         }
-        else if (pindexStop->nHeight < pindexStart->nHeight) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "stop_height must be greater then start_height");
+
+        if (!request.params[1].isNull()) {
+            pindexStop = chainActive[request.params[1].get_int()];
+            if (!pindexStop) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid stop_height");
+            }
+            else if (pindexStop->nHeight < pindexStart->nHeight) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "stop_height must be greater then start_height");
+            }
         }
     }
 
     // We can't rescan beyond non-pruned blocks, stop and throw an error
     if (fPruneMode) {
-        CBlockIndex *block = pindexStop ? pindexStop : chainActive.Tip();
+        LOCK(cs_main);
+        CBlockIndex *block = pindexStop ? pindexStop : pChainTip;
         while (block && block->nHeight >= pindexStart->nHeight) {
             if (!(block->nStatus & BLOCK_HAVE_DATA)) {
                 throw JSONRPCError(RPC_MISC_ERROR, "Can't rescan beyond pruned data. Use RPC call getblockchaininfo to determine your pruned height.");
@@ -3436,12 +3446,11 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
             throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
         }
         // if we got a nullptr returned, ScanForWalletTransactions did rescan up to the requested stopindex
-        stopBlock = pindexStop ? pindexStop : chainActive.Tip();
+        stopBlock = pindexStop ? pindexStop : pChainTip;
     }
     else {
         throw JSONRPCError(RPC_MISC_ERROR, "Rescan failed. Potentially corrupted data files.");
     }
-
     UniValue response(UniValue::VOBJ);
     response.pushKV("start_height", pindexStart->nHeight);
     response.pushKV("stop_height", stopBlock->nHeight);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index da721ea008..450ef4c49c 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1614,14 +1614,15 @@ void CWalletTx::GetAmounts(std::list<COutputEntry>& listReceived,
  */
 int64_t CWallet::RescanFromTime(int64_t startTime, bool update)
 {
-    AssertLockHeld(cs_main);
-    AssertLockHeld(cs_wallet);
-
     // Find starting block. May be null if nCreateTime is greater than the
     // highest blockchain timestamp, in which case there is nothing that needs
     // to be scanned.
-    CBlockIndex* const startBlock = chainActive.FindEarliestAtLeast(startTime - TIMESTAMP_WINDOW);
-    LogPrintf("%s: Rescanning last %i blocks\n", __func__, startBlock ? chainActive.Height() - startBlock->nHeight + 1 : 0);
+    CBlockIndex* startBlock = nullptr;
+    {
+        LOCK(cs_main);
+        startBlock = chainActive.FindEarliestAtLeast(startTime - TIMESTAMP_WINDOW);
+        LogPrintf("%s: Rescanning last %i blocks\n", __func__, startBlock ? chainActive.Height() - startBlock->nHeight + 1 : 0);
+    }
 
     if (startBlock) {
         const CBlockIndex* const failedBlock = ScanForWalletTransactions(startBlock, nullptr, update);
@@ -1643,6 +1644,10 @@ int64_t CWallet::RescanFromTime(int64_t startTime, bool update)
  *
  * If pindexStop is not a nullptr, the scan will stop at the block-index
  * defined by pindexStop
+ *
+ * Caller needs to make sure pindexStop (and the optional pindexStart) are on
+ * the main chain after to the addition of any new keys you want to detect
+ * transactions for.
  */
 CBlockIndex* CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, CBlockIndex* pindexStop, bool fUpdate)
 {
@@ -1656,24 +1661,49 @@ CBlockIndex* CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, CBlock
     CBlockIndex* pindex = pindexStart;
     CBlockIndex* ret = nullptr;
     {
-        LOCK2(cs_main, cs_wallet);
         fAbortRescan = false;
         fScanningWallet = true;
 
         ShowProgress(_("Rescanning..."), 0); // show rescan progress in GUI as dialog or on splashscreen, if -rescan on startup
-        double dProgressStart = GuessVerificationProgress(chainParams.TxData(), pindex);
-        double dProgressTip = GuessVerificationProgress(chainParams.TxData(), chainActive.Tip());
+        CBlockIndex* tip = nullptr;
+        double dProgressStart;
+        double dProgressTip;
+        {
+            LOCK(cs_main);
+            tip = chainActive.Tip();
+            dProgressStart = GuessVerificationProgress(chainParams.TxData(), pindex);
+            dProgressTip = GuessVerificationProgress(chainParams.TxData(), tip);
+        }
         while (pindex && !fAbortRescan)
         {
-            if (pindex->nHeight % 100 == 0 && dProgressTip - dProgressStart > 0.0)
-                ShowProgress(_("Rescanning..."), std::max(1, std::min(99, (int)((GuessVerificationProgress(chainParams.TxData(), pindex) - dProgressStart) / (dProgressTip - dProgressStart) * 100))));
+            if (pindex->nHeight % 100 == 0 && dProgressTip - dProgressStart > 0.0) {
+                double gvp = 0;
+                {
+                    LOCK(cs_main);
+                    gvp = GuessVerificationProgress(chainParams.TxData(), pindex);
+                }
+                ShowProgress(_("Rescanning..."), std::max(1, std::min(99, (int)((gvp - dProgressStart) / (dProgressTip - dProgressStart) * 100))));
+            }
             if (GetTime() >= nNow + 60) {
                 nNow = GetTime();
+                LOCK(cs_main);
                 LogPrintf("Still rescanning. At block %d. Progress=%f\n", pindex->nHeight, GuessVerificationProgress(chainParams.TxData(), pindex));
             }
 
+            bool readRet = false;
             CBlock block;
-            if (ReadBlockFromDisk(block, pindex, Params().GetConsensus())) {
+            {
+                LOCK(cs_main);
+                readRet = ReadBlockFromDisk(block, pindex, Params().GetConsensus());
+            }
+            if (readRet) {
+                LOCK2(cs_main, cs_wallet);
+                if (pindex && !chainActive.Contains(pindex)) {
+                    // Abort scan if current block is no longer active, to prevent
+                    // marking transactions as coming from the wrong block.
+                    ret = pindex;
+                    break;
+                }
                 for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
                     AddToWalletIfInvolvingMe(block.vtx[posInBlock], pindex, posInBlock, fUpdate);
                 }
@@ -1683,7 +1713,15 @@ CBlockIndex* CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, CBlock
             if (pindex == pindexStop) {
                 break;
             }
-            pindex = chainActive.Next(pindex);
+            {
+                LOCK(cs_main);
+                pindex = chainActive.Next(pindex);
+                if (tip != chainActive.Tip()) {
+                    tip = chainActive.Tip();
+                    // in case the tip has changed, update progress max
+                    dProgressTip = GuessVerificationProgress(chainParams.TxData(), tip);
+                }
+            }
         }
         if (pindex && fAbortRescan) {
             LogPrintf("Rescan aborted at block %d. Progress=%f\n", pindex->nHeight, GuessVerificationProgress(chainParams.TxData(), pindex));