Merge bitcoin/bitcoin#30111: locks: introduce mutex for tx download, flush rejection filters once per tip change

c85accecafc20f6a6ae94bdf6cdd3ba9747218fd [refactor] delete EraseTxNoLock, just use EraseTx (glozow)
6ff84069a5dd92303ed2ec28f0ec7c96bbda3938 remove obsoleted TxOrphanage::m_mutex (glozow)
61745c7451ec64b26c74f672c688e82efb3b96aa lock m_recent_confirmed_transactions using m_tx_download_mutex (glozow)
723ea0f9a5b5e3f3f58ea049a98299ff0ebde468 remove obsoleted hashRecentRejectsChainTip (glozow)
18a43552509603ddf83b752fd7b4b973ba1dcf82 update recent_rejects filters on ActiveTipChange (glozow)
36f170d87924e50d0ff9be2a1b0f2a8f13950a9b add ValidationInterface::ActiveTipChange (glozow)
3eb1307df0a38ac4ea52995fbb03ead37387b41e guard TxRequest and rejection caches with new mutex (glozow)

Pull request description:

  See #27463 for full project tracking.

  This contains the first few commits of #30110, which require some thinking about thread safety in review.
  - Introduce a new `m_tx_download_mutex` which guards the transaction download data structures including `m_txrequest`, the rolling bloom filters, and `m_orphanage`. Later this should become the mutex guarding `TxDownloadManager`.
    - `m_txrequest` doesn't need to be guarded using `cs_main` anymore
    - `m_recent_confirmed_transactions` doesn't need its own lock anymore
    - `m_orphanage` doesn't need its own lock anymore
  - Adds a new `ValidationInterface` event, `ActiveTipChanged`, which is a synchronous callback whenever the tip of the active chainstate changes.
  - Flush `m_recent_rejects` and `m_recent_rejects_reconsiderable` on `ActiveTipChanged` just once instead of checking the tip every time `AlreadyHaveTx` is called. This should speed up calls to that function (no longer comparing a block hash each time) and removes the need to lock `cs_main` every time it is called.

  Motivation:
  - These data structures need synchronization. While we are holding `m_tx_download_mutex`, these should hold:
    - a tx hash in `m_txrequest` is not also in `m_orphanage`
    - a tx hash in `m_txrequest` is not also in `m_recent_rejects` or `m_recent_confirmed_transactions`
    - In the future, orphan resolution tracking should also be synchronized. If a tx has an entry in the orphan resolution tracker, it is also in `m_orphanage`, and not in `m_txrequest`, etc.
  - Currently, `cs_main` is used to e.g. sync accesses to `m_txrequest`. We should not broaden the scope of things it locks.
  - Currently, we need to know the current chainstate every time we call `AlreadyHaveTx` so we can decide whether we should update it. Every call compares the current tip hash with `hashRecentRejectsChainTip`. It is more efficient to have a validation interface callback that updates the rejection filters whenever the chain tip changes.

ACKs for top commit:
  instagibbs:
    reACK c85accecafc20f6a6ae94bdf6cdd3ba9747218fd
  dergoegge:
    Code review ACK c85accecafc20f6a6ae94bdf6cdd3ba9747218fd
  theStack:
    Light code-review ACK c85accecafc20f6a6ae94bdf6cdd3ba9747218fd
  hebasto:
    ACK c85accecafc20f6a6ae94bdf6cdd3ba9747218fd, I have reviewed the code and it looks OK.

Tree-SHA512: c3bd524b5de1cafc9a10770dadb484cc479d6d4c687d80dd0f176d339fd95f73b85cb44cb3b6b464d38a52e20feda00aa2a1da5a73339e31831687e4bd0aa0c5

7 files changed, 128 insertions, 124 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index d674758abd..c241994763 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -489,10 +489,12 @@ public:
                     CTxMemPool& pool, node::Warnings& warnings, Options opts);
 
     /** Overridden from CValidationInterface. */
+    void ActiveTipChange(const CBlockIndex* new_tip, bool) override
+        EXCLUSIVE_LOCKS_REQUIRED(!m_tx_download_mutex);
     void BlockConnected(ChainstateRole role, const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override
-        EXCLUSIVE_LOCKS_REQUIRED(!m_recent_confirmed_transactions_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_tx_download_mutex);
     void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) override
-        EXCLUSIVE_LOCKS_REQUIRED(!m_recent_confirmed_transactions_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_tx_download_mutex);
     void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override
         EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
     void BlockChecked(const CBlock& block, const BlockValidationState& state) override
@@ -501,13 +503,13 @@ public:
         EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex);
 
     /** Implement NetEventsInterface */
-    void InitializeNode(const CNode& node, ServiceFlags our_services) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
-    void FinalizeNode(const CNode& node) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_headers_presync_mutex);
+    void InitializeNode(const CNode& node, ServiceFlags our_services) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_tx_download_mutex);
+    void FinalizeNode(const CNode& node) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_headers_presync_mutex, !m_tx_download_mutex);
     bool HasAllDesirableServiceFlags(ServiceFlags services) const override;
     bool ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt) override
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_recent_confirmed_transactions_mutex, !m_most_recent_block_mutex, !m_headers_presync_mutex, g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_most_recent_block_mutex, !m_headers_presync_mutex, g_msgproc_mutex, !m_tx_download_mutex);
     bool SendMessages(CNode* pto) override
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_recent_confirmed_transactions_mutex, !m_most_recent_block_mutex, g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_most_recent_block_mutex, g_msgproc_mutex, !m_tx_download_mutex);
 
     /** Implement PeerManager */
     void StartScheduledTasks(CScheduler& scheduler) override;
@@ -526,7 +528,7 @@ public:
     void UnitTestMisbehaving(NodeId peer_id) override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex) { Misbehaving(*Assert(GetPeerRef(peer_id)), ""); };
     void ProcessMessage(CNode& pfrom, const std::string& msg_type, DataStream& vRecv,
                         const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc) override
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_recent_confirmed_transactions_mutex, !m_most_recent_block_mutex, !m_headers_presync_mutex, g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_most_recent_block_mutex, !m_headers_presync_mutex, g_msgproc_mutex, !m_tx_download_mutex);
     void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds) override;
     ServiceFlags GetDesirableServiceFlags(ServiceFlags services) const override;
 
@@ -585,12 +587,12 @@ private:
      * Updates m_txrequest, m_recent_rejects, m_recent_rejects_reconsiderable, m_orphanage, and vExtraTxnForCompact. */
     void ProcessInvalidTx(NodeId nodeid, const CTransactionRef& tx, const TxValidationState& result,
                           bool maybe_add_extra_compact_tx)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, m_tx_download_mutex);
 
     /** Handle a transaction whose result was MempoolAcceptResult::ResultType::VALID.
      * Updates m_txrequest, m_orphanage, and vExtraTxnForCompact. Also queues the tx for relay. */
     void ProcessValidTx(NodeId nodeid, const CTransactionRef& tx, const std::list<CTransactionRef>& replaced_transactions)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, m_tx_download_mutex);
 
     struct PackageToValidate {
         const Package m_txns;
@@ -620,13 +622,13 @@ private:
      * individual transactions, and caches rejection for the package as a group.
      */
     void ProcessPackageResult(const PackageToValidate& package_to_validate, const PackageMempoolAcceptResult& package_result)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, m_tx_download_mutex);
 
     /** Look for a child of this transaction in the orphanage to form a 1-parent-1-child package,
      * skipping any combinations that have already been tried. Return the resulting package along with
      * the senders of its respective transactions, or std::nullopt if no package is found. */
     std::optional<PackageToValidate> Find1P1CPackage(const CTransactionRef& ptx, NodeId nodeid)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, m_tx_download_mutex);
 
     /**
      * Reconsider orphan transactions after a parent has been accepted to the mempool.
@@ -640,7 +642,7 @@ private:
      *                     will be empty.
      */
     bool ProcessOrphanTx(Peer& peer)
-        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, !m_tx_download_mutex);
 
     /** Process a single headers message from a peer.
      *
@@ -722,7 +724,7 @@ private:
      *  peer. The announcement parameters are decided in PeerManager and then
      *  passed to TxRequestTracker. */
     void AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
-        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
+        EXCLUSIVE_LOCKS_REQUIRED(::cs_main, m_tx_download_mutex);
 
     /** Send a message to a peer */
     void PushMessage(CNode& node, CSerializedNetMsg&& msg) const { m_connman.PushMessage(&node, std::move(msg)); }
@@ -770,7 +772,19 @@ private:
     BanMan* const m_banman;
     ChainstateManager& m_chainman;
     CTxMemPool& m_mempool;
-    TxRequestTracker m_txrequest GUARDED_BY(::cs_main);
+
+    /** Synchronizes tx download including TxRequestTracker, rejection filters, and TxOrphanage.
+     * Lock invariants:
+     * - A txhash (txid or wtxid) in m_txrequest is not also in m_orphanage.
+     * - A txhash (txid or wtxid) in m_txrequest is not also in m_recent_rejects.
+     * - A txhash (txid or wtxid) in m_txrequest is not also in m_recent_rejects_reconsiderable.
+     * - A txhash (txid or wtxid) in m_txrequest is not also in m_recent_confirmed_transactions.
+     * - Each data structure's limits hold (m_orphanage max size, m_txrequest per-peer limits, etc).
+     *
+     * m_tx_download_mutex must be acquired before mempool.cs
+     */
+    Mutex m_tx_download_mutex;
+    TxRequestTracker m_txrequest GUARDED_BY(m_tx_download_mutex);
     std::unique_ptr<TxReconciliationTracker> m_txreconciliation;
 
     /** The height of the best chain */
@@ -847,11 +861,9 @@ private:
      *  - m_recent_rejects
      *  - m_recent_rejects_reconsiderable (if include_reconsiderable = true)
      *  - m_recent_confirmed_transactions
-     * Also responsible for resetting m_recent_rejects and m_recent_rejects_reconsiderable if the
-     * chain tip has changed.
      *  */
     bool AlreadyHaveTx(const GenTxid& gtxid, bool include_reconsiderable)
-        EXCLUSIVE_LOCKS_REQUIRED(cs_main, !m_recent_confirmed_transactions_mutex);
+        EXCLUSIVE_LOCKS_REQUIRED(m_tx_download_mutex);
 
     /**
      * Filter for transactions that were recently rejected by the mempool.
@@ -887,10 +899,7 @@ private:
      *
      * Memory used: 1.3 MB
      */
-    CRollingBloomFilter m_recent_rejects GUARDED_BY(::cs_main){120'000, 0.000'001};
-    /** Block hash of chain tip the last time we reset m_recent_rejects and
-     * m_recent_rejects_reconsiderable. */
-    uint256 hashRecentRejectsChainTip GUARDED_BY(cs_main);
+    CRollingBloomFilter m_recent_rejects GUARDED_BY(m_tx_download_mutex){120'000, 0.000'001};
 
     /**
      * Filter for:
@@ -912,7 +921,7 @@ private:
      *
      * Parameters are picked to be the same as m_recent_rejects, with the same rationale.
      */
-    CRollingBloomFilter m_recent_rejects_reconsiderable GUARDED_BY(::cs_main){120'000, 0.000'001};
+    CRollingBloomFilter m_recent_rejects_reconsiderable GUARDED_BY(m_tx_download_mutex){120'000, 0.000'001};
 
     /*
      * Filter for transactions that have been recently confirmed.
@@ -929,8 +938,7 @@ private:
      * transaction per day that would be inadvertently ignored (which is the
      * same probability that we have in the reject filter).
      */
-    Mutex m_recent_confirmed_transactions_mutex;
-    CRollingBloomFilter m_recent_confirmed_transactions GUARDED_BY(m_recent_confirmed_transactions_mutex){48'000, 0.000'001};
+    CRollingBloomFilter m_recent_confirmed_transactions GUARDED_BY(m_tx_download_mutex){48'000, 0.000'001};
 
     /**
      * For sending `inv`s to inbound peers, we use a single (exponentially
@@ -1067,7 +1075,7 @@ private:
     int m_peers_downloading_from GUARDED_BY(cs_main) = 0;
 
     /** Storage for orphan information */
-    TxOrphanage m_orphanage;
+    TxOrphanage m_orphanage GUARDED_BY(m_tx_download_mutex);
 
     void AddToCompactExtraTransactions(const CTransactionRef& tx) EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
@@ -1630,7 +1638,8 @@ void PeerManagerImpl::PushNodeVersion(CNode& pnode, const Peer& peer)
 
 void PeerManagerImpl::AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
 {
-    AssertLockHeld(::cs_main); // For m_txrequest
+    AssertLockHeld(::cs_main); // for State
+    AssertLockHeld(m_tx_download_mutex); // For m_txrequest
     NodeId nodeid = node.GetId();
     if (!node.HasPermission(NetPermissionFlags::Relay) && m_txrequest.Count(nodeid) >= MAX_PEER_TX_ANNOUNCEMENTS) {
         // Too many queued announcements from this peer
@@ -1666,8 +1675,11 @@ void PeerManagerImpl::InitializeNode(const CNode& node, ServiceFlags our_service
 {
     NodeId nodeid = node.GetId();
     {
-        LOCK(cs_main);
+        LOCK(cs_main); // For m_node_states
         m_node_states.emplace_hint(m_node_states.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(node.IsInboundConn()));
+    }
+    {
+        LOCK(m_tx_download_mutex);
         assert(m_txrequest.Count(nodeid) == 0);
     }
 
@@ -1735,8 +1747,11 @@ void PeerManagerImpl::FinalizeNode(const CNode& node)
             }
         }
     }
-    m_orphanage.EraseForPeer(nodeid);
-    m_txrequest.DisconnectedPeer(nodeid);
+    {
+        LOCK(m_tx_download_mutex);
+        m_orphanage.EraseForPeer(nodeid);
+        m_txrequest.DisconnectedPeer(nodeid);
+    }
     if (m_txreconciliation) m_txreconciliation->ForgetPeer(nodeid);
     m_num_preferred_download_peers -= state->fPreferredDownload;
     m_peers_downloading_from -= (!state->vBlocksInFlight.empty());
@@ -1753,6 +1768,7 @@ void PeerManagerImpl::FinalizeNode(const CNode& node)
         assert(m_peers_downloading_from == 0);
         assert(m_outbound_peers_with_protect_from_disconnect == 0);
         assert(m_wtxid_relay_peers == 0);
+        LOCK(m_tx_download_mutex);
         assert(m_txrequest.Size() == 0);
         assert(m_orphanage.Size() == 0);
     }
@@ -2054,6 +2070,21 @@ void PeerManagerImpl::StartScheduledTasks(CScheduler& scheduler)
     scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); }, delta);
 }
 
+void PeerManagerImpl::ActiveTipChange(const CBlockIndex* new_tip, bool is_ibd)
+{
+    AssertLockNotHeld(m_mempool.cs);
+    AssertLockNotHeld(m_tx_download_mutex);
+
+    if (!is_ibd) {
+        LOCK(m_tx_download_mutex);
+        // If the chain tip has changed, previously rejected transactions might now be valid, e.g. due
+        // to a timelock. Reset the rejection filters to give those transactions another chance if we
+        // see them again.
+        m_recent_rejects.reset();
+        m_recent_rejects_reconsiderable.reset();
+    }
+}
+
 /**
  * Evict orphan txn pool entries based on a newly connected
  * block, remember the recently confirmed transactions, and delete tracked
@@ -2084,23 +2115,18 @@ void PeerManagerImpl::BlockConnected(
     if (role == ChainstateRole::BACKGROUND) {
         return;
     }
+    LOCK(m_tx_download_mutex);
     m_orphanage.EraseForBlock(*pblock);
 
-    {
-        LOCK(m_recent_confirmed_transactions_mutex);
-        for (const auto& ptx : pblock->vtx) {
-            m_recent_confirmed_transactions.insert(ptx->GetHash().ToUint256());
-            if (ptx->HasWitness()) {
-                m_recent_confirmed_transactions.insert(ptx->GetWitnessHash().ToUint256());
-            }
+    for (const auto& ptx : pblock->vtx) {
+        m_recent_confirmed_transactions.insert(ptx->GetHash().ToUint256());
+        if (ptx->HasWitness()) {
+            m_recent_confirmed_transactions.insert(ptx->GetWitnessHash().ToUint256());
         }
     }
-    {
-        LOCK(cs_main);
-        for (const auto& ptx : pblock->vtx) {
-            m_txrequest.ForgetTxHash(ptx->GetHash());
-            m_txrequest.ForgetTxHash(ptx->GetWitnessHash());
-        }
+    for (const auto& ptx : pblock->vtx) {
+        m_txrequest.ForgetTxHash(ptx->GetHash());
+        m_txrequest.ForgetTxHash(ptx->GetWitnessHash());
     }
 }
 
@@ -2114,7 +2140,7 @@ void PeerManagerImpl::BlockDisconnected(const std::shared_ptr<const CBlock> &blo
     // block's worth of transactions in it, but that should be fine, since
     // presumably the most common case of relaying a confirmed transaction
     // should be just after a new block containing it is found.
-    LOCK(m_recent_confirmed_transactions_mutex);
+    LOCK(m_tx_download_mutex);
     m_recent_confirmed_transactions.reset();
 }
 
@@ -2254,15 +2280,7 @@ void PeerManagerImpl::BlockChecked(const CBlock& block, const BlockValidationSta
 
 bool PeerManagerImpl::AlreadyHaveTx(const GenTxid& gtxid, bool include_reconsiderable)
 {
-    if (m_chainman.ActiveChain().Tip()->GetBlockHash() != hashRecentRejectsChainTip) {
-        // If the chain tip has changed previously rejected transactions
-        // might be now valid, e.g. due to a nLockTime'd tx becoming valid,
-        // or a double-spend. Reset the rejects filter and give those
-        // txs a second chance.
-        hashRecentRejectsChainTip = m_chainman.ActiveChain().Tip()->GetBlockHash();
-        m_recent_rejects.reset();
-        m_recent_rejects_reconsiderable.reset();
-    }
+    AssertLockHeld(m_tx_download_mutex);
 
     const uint256& hash = gtxid.GetHash();
 
@@ -2286,10 +2304,7 @@ bool PeerManagerImpl::AlreadyHaveTx(const GenTxid& gtxid, bool include_reconside
 
     if (include_reconsiderable && m_recent_rejects_reconsiderable.contains(hash)) return true;
 
-    {
-        LOCK(m_recent_confirmed_transactions_mutex);
-        if (m_recent_confirmed_transactions.contains(hash)) return true;
-    }
+    if (m_recent_confirmed_transactions.contains(hash)) return true;
 
     return m_recent_rejects.contains(hash) || m_mempool.exists(gtxid);
 }
@@ -3154,7 +3169,7 @@ void PeerManagerImpl::ProcessInvalidTx(NodeId nodeid, const CTransactionRef& ptx
 {
     AssertLockNotHeld(m_peer_mutex);
     AssertLockHeld(g_msgproc_mutex);
-    AssertLockHeld(cs_main);
+    AssertLockHeld(m_tx_download_mutex);
 
     LogDebug(BCLog::MEMPOOLREJ, "%s (wtxid=%s) from peer=%d was not accepted: %s\n",
         ptx->GetHash().ToString(),
@@ -3219,7 +3234,7 @@ void PeerManagerImpl::ProcessValidTx(NodeId nodeid, const CTransactionRef& tx, c
 {
     AssertLockNotHeld(m_peer_mutex);
     AssertLockHeld(g_msgproc_mutex);
-    AssertLockHeld(cs_main);
+    AssertLockHeld(m_tx_download_mutex);
 
     // As this version of the transaction was acceptable, we can forget about any requests for it.
     // No-op if the tx is not in txrequest.
@@ -3247,7 +3262,7 @@ void PeerManagerImpl::ProcessPackageResult(const PackageToValidate& package_to_v
 {
     AssertLockNotHeld(m_peer_mutex);
     AssertLockHeld(g_msgproc_mutex);
-    AssertLockHeld(cs_main);
+    AssertLockHeld(m_tx_download_mutex);
 
     const auto& package = package_to_validate.m_txns;
     const auto& senders = package_to_validate.m_senders;
@@ -3303,7 +3318,7 @@ std::optional<PeerManagerImpl::PackageToValidate> PeerManagerImpl::Find1P1CPacka
 {
     AssertLockNotHeld(m_peer_mutex);
     AssertLockHeld(g_msgproc_mutex);
-    AssertLockHeld(cs_main);
+    AssertLockHeld(m_tx_download_mutex);
 
     const auto& parent_wtxid{ptx->GetWitnessHash()};
 
@@ -3356,7 +3371,7 @@ std::optional<PeerManagerImpl::PackageToValidate> PeerManagerImpl::Find1P1CPacka
 bool PeerManagerImpl::ProcessOrphanTx(Peer& peer)
 {
     AssertLockHeld(g_msgproc_mutex);
-    LOCK(cs_main);
+    LOCK2(::cs_main, m_tx_download_mutex);
 
     CTransactionRef porphanTx = nullptr;
 
@@ -4173,7 +4188,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
 
         const bool reject_tx_invs{RejectIncomingTxs(pfrom)};
 
-        LOCK(cs_main);
+        LOCK2(cs_main, m_tx_download_mutex);
 
         const auto current_time{GetTime<std::chrono::microseconds>()};
         uint256* best_block{nullptr};
@@ -4506,7 +4521,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
         const uint256& hash = peer->m_wtxid_relay ? wtxid : txid;
         AddKnownTx(*peer, hash);
 
-        LOCK(cs_main);
+        LOCK2(cs_main, m_tx_download_mutex);
 
         m_txrequest.ReceivedResponse(pfrom.GetId(), txid);
         if (tx.HasWitness()) m_txrequest.ReceivedResponse(pfrom.GetId(), wtxid);
@@ -5263,7 +5278,7 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
         std::vector<CInv> vInv;
         vRecv >> vInv;
         if (vInv.size() <= MAX_PEER_TX_ANNOUNCEMENTS + MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
-            LOCK(::cs_main);
+            LOCK(m_tx_download_mutex);
             for (CInv &inv : vInv) {
                 if (inv.IsGenTxMsg()) {
                     // If we receive a NOTFOUND message for a tx we requested, mark the announcement for it as
@@ -5388,6 +5403,7 @@ bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt
         //  by another peer that was already processed; in that case,
         //  the extra work may not be noticed, possibly resulting in an
         //  unnecessary 100ms delay)
+        LOCK(m_tx_download_mutex);
         if (m_orphanage.HaveTxToReconsider(peer->m_id)) fMoreWork = true;
     } catch (const std::exception& e) {
         LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' (%s) caught\n", __func__, SanitizeString(msg.m_type), msg.m_message_size, e.what(), typeid(e).name());
@@ -6281,6 +6297,7 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
         //
         // Message: getdata (transactions)
         //
+        LOCK(m_tx_download_mutex);
         std::vector<std::pair<NodeId, GenTxid>> expired;
         auto requestable = m_txrequest.GetRequestable(pto->GetId(), current_time, &expired);
         for (const auto& entry : expired) {
diff --git a/src/test/orphanage_tests.cpp b/src/test/orphanage_tests.cpp
index 3459aa9f0e..082d090d7c 100644
--- a/src/test/orphanage_tests.cpp
+++ b/src/test/orphanage_tests.cpp
@@ -21,15 +21,13 @@ BOOST_FIXTURE_TEST_SUITE(orphanage_tests, TestingSetup)
 class TxOrphanageTest : public TxOrphanage
 {
 public:
-    inline size_t CountOrphans() const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    inline size_t CountOrphans() const
     {
-        LOCK(m_mutex);
         return m_orphans.size();
     }
 
-    CTransactionRef RandomOrphan() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    CTransactionRef RandomOrphan()
     {
-        LOCK(m_mutex);
         std::map<Wtxid, OrphanTx>::iterator it;
         it = m_orphans.lower_bound(Wtxid::FromUint256(InsecureRand256()));
         if (it == m_orphans.end())
diff --git a/src/txorphanage.cpp b/src/txorphanage.cpp
index 3eaf53939d..df9b96e64d 100644
--- a/src/txorphanage.cpp
+++ b/src/txorphanage.cpp
@@ -20,8 +20,6 @@ static constexpr auto ORPHAN_TX_EXPIRE_INTERVAL{5min};
 
 bool TxOrphanage::AddTx(const CTransactionRef& tx, NodeId peer)
 {
-    LOCK(m_mutex);
-
     const Txid& hash = tx->GetHash();
     const Wtxid& wtxid = tx->GetWitnessHash();
     if (m_orphans.count(wtxid))
@@ -55,13 +53,6 @@ bool TxOrphanage::AddTx(const CTransactionRef& tx, NodeId peer)
 
 int TxOrphanage::EraseTx(const Wtxid& wtxid)
 {
-    LOCK(m_mutex);
-    return EraseTxNoLock(wtxid);
-}
-
-int TxOrphanage::EraseTxNoLock(const Wtxid& wtxid)
-{
-    AssertLockHeld(m_mutex);
     std::map<Wtxid, OrphanTx>::iterator it = m_orphans.find(wtxid);
     if (it == m_orphans.end())
         return 0;
@@ -97,8 +88,6 @@ int TxOrphanage::EraseTxNoLock(const Wtxid& wtxid)
 
 void TxOrphanage::EraseForPeer(NodeId peer)
 {
-    LOCK(m_mutex);
-
     m_peer_work_set.erase(peer);
 
     int nErased = 0;
@@ -108,7 +97,7 @@ void TxOrphanage::EraseForPeer(NodeId peer)
         // increment to avoid iterator becoming invalid after erasure
         const auto& [wtxid, orphan] = *iter++;
         if (orphan.fromPeer == peer) {
-            nErased += EraseTxNoLock(wtxid);
+            nErased += EraseTx(wtxid);
         }
     }
     if (nErased > 0) LogPrint(BCLog::TXPACKAGES, "Erased %d orphan transaction(s) from peer=%d\n", nErased, peer);
@@ -116,8 +105,6 @@ void TxOrphanage::EraseForPeer(NodeId peer)
 
 void TxOrphanage::LimitOrphans(unsigned int max_orphans, FastRandomContext& rng)
 {
-    LOCK(m_mutex);
-
     unsigned int nEvicted = 0;
     auto nNow{Now<NodeSeconds>()};
     if (m_next_sweep <= nNow) {
@@ -129,7 +116,7 @@ void TxOrphanage::LimitOrphans(unsigned int max_orphans, FastRandomContext& rng)
         {
             std::map<Wtxid, OrphanTx>::iterator maybeErase = iter++;
             if (maybeErase->second.nTimeExpire <= nNow) {
-                nErased += EraseTxNoLock(maybeErase->second.tx->GetWitnessHash());
+                nErased += EraseTx(maybeErase->second.tx->GetWitnessHash());
             } else {
                 nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
             }
@@ -142,7 +129,7 @@ void TxOrphanage::LimitOrphans(unsigned int max_orphans, FastRandomContext& rng)
     {
         // Evict a random orphan:
         size_t randompos = rng.randrange(m_orphan_list.size());
-        EraseTxNoLock(m_orphan_list[randompos]->second.tx->GetWitnessHash());
+        EraseTx(m_orphan_list[randompos]->second.tx->GetWitnessHash());
         ++nEvicted;
     }
     if (nEvicted > 0) LogPrint(BCLog::TXPACKAGES, "orphanage overflow, removed %u tx\n", nEvicted);
@@ -150,9 +137,6 @@ void TxOrphanage::LimitOrphans(unsigned int max_orphans, FastRandomContext& rng)
 
 void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx)
 {
-    LOCK(m_mutex);
-
-
     for (unsigned int i = 0; i < tx.vout.size(); i++) {
         const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(tx.GetHash(), i));
         if (it_by_prev != m_outpoint_to_orphan_it.end()) {
@@ -171,14 +155,11 @@ void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx)
 
 bool TxOrphanage::HaveTx(const Wtxid& wtxid) const
 {
-    LOCK(m_mutex);
     return m_orphans.count(wtxid);
 }
 
 CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer)
 {
-    LOCK(m_mutex);
-
     auto work_set_it = m_peer_work_set.find(peer);
     if (work_set_it != m_peer_work_set.end()) {
         auto& work_set = work_set_it->second;
@@ -197,8 +178,6 @@ CTransactionRef TxOrphanage::GetTxToReconsider(NodeId peer)
 
 bool TxOrphanage::HaveTxToReconsider(NodeId peer)
 {
-    LOCK(m_mutex);
-
     auto work_set_it = m_peer_work_set.find(peer);
     if (work_set_it != m_peer_work_set.end()) {
         auto& work_set = work_set_it->second;
@@ -209,8 +188,6 @@ bool TxOrphanage::HaveTxToReconsider(NodeId peer)
 
 void TxOrphanage::EraseForBlock(const CBlock& block)
 {
-    LOCK(m_mutex);
-
     std::vector<Wtxid> vOrphanErase;
 
     for (const CTransactionRef& ptx : block.vtx) {
@@ -231,7 +208,7 @@ void TxOrphanage::EraseForBlock(const CBlock& block)
     if (vOrphanErase.size()) {
         int nErased = 0;
         for (const auto& orphanHash : vOrphanErase) {
-            nErased += EraseTxNoLock(orphanHash);
+            nErased += EraseTx(orphanHash);
         }
         LogPrint(BCLog::TXPACKAGES, "Erased %d orphan transaction(s) included or conflicted by block\n", nErased);
     }
@@ -239,8 +216,6 @@ void TxOrphanage::EraseForBlock(const CBlock& block)
 
 std::vector<CTransactionRef> TxOrphanage::GetChildrenFromSamePeer(const CTransactionRef& parent, NodeId nodeid) const
 {
-    LOCK(m_mutex);
-
     // First construct a vector of iterators to ensure we do not return duplicates of the same tx
     // and so we can sort by nTimeExpire.
     std::vector<OrphanMap::iterator> iters;
@@ -281,8 +256,6 @@ std::vector<CTransactionRef> TxOrphanage::GetChildrenFromSamePeer(const CTransac
 
 std::vector<std::pair<CTransactionRef, NodeId>> TxOrphanage::GetChildrenFromDifferentPeer(const CTransactionRef& parent, NodeId nodeid) const
 {
-    LOCK(m_mutex);
-
     // First construct vector of iterators to ensure we do not return duplicates of the same tx.
     std::vector<OrphanMap::iterator> iters;
 
diff --git a/src/txorphanage.h b/src/txorphanage.h
index 3083c8467f..207b79e009 100644
--- a/src/txorphanage.h
+++ b/src/txorphanage.h
@@ -22,55 +22,51 @@
 class TxOrphanage {
 public:
     /** Add a new orphan transaction */
-    bool AddTx(const CTransactionRef& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    bool AddTx(const CTransactionRef& tx, NodeId peer);
 
     /** Check if we already have an orphan transaction (by wtxid only) */
-    bool HaveTx(const Wtxid& wtxid) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    bool HaveTx(const Wtxid& wtxid) const;
 
     /** Extract a transaction from a peer's work set
      *  Returns nullptr if there are no transactions to work on.
      *  Otherwise returns the transaction reference, and removes
      *  it from the work set.
      */
-    CTransactionRef GetTxToReconsider(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    CTransactionRef GetTxToReconsider(NodeId peer);
 
     /** Erase an orphan by wtxid */
-    int EraseTx(const Wtxid& wtxid) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    int EraseTx(const Wtxid& wtxid);
 
     /** Erase all orphans announced by a peer (eg, after that peer disconnects) */
-    void EraseForPeer(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    void EraseForPeer(NodeId peer);
 
     /** Erase all orphans included in or invalidated by a new block */
-    void EraseForBlock(const CBlock& block) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    void EraseForBlock(const CBlock& block);
 
     /** Limit the orphanage to the given maximum */
-    void LimitOrphans(unsigned int max_orphans, FastRandomContext& rng) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    void LimitOrphans(unsigned int max_orphans, FastRandomContext& rng);
 
     /** Add any orphans that list a particular tx as a parent into the from peer's work set */
-    void AddChildrenToWorkSet(const CTransaction& tx) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);;
+    void AddChildrenToWorkSet(const CTransaction& tx);
 
     /** Does this peer have any work to do? */
-    bool HaveTxToReconsider(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);;
+    bool HaveTxToReconsider(NodeId peer);
 
     /** Get all children that spend from this tx and were received from nodeid. Sorted from most
      * recent to least recent. */
-    std::vector<CTransactionRef> GetChildrenFromSamePeer(const CTransactionRef& parent, NodeId nodeid) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    std::vector<CTransactionRef> GetChildrenFromSamePeer(const CTransactionRef& parent, NodeId nodeid) const;
 
     /** Get all children that spend from this tx but were not received from nodeid. Also return
      * which peer provided each tx. */
-    std::vector<std::pair<CTransactionRef, NodeId>> GetChildrenFromDifferentPeer(const CTransactionRef& parent, NodeId nodeid) const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+    std::vector<std::pair<CTransactionRef, NodeId>> GetChildrenFromDifferentPeer(const CTransactionRef& parent, NodeId nodeid) const;
 
     /** Return how many entries exist in the orphange */
-    size_t Size() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)
+    size_t Size()
     {
-        LOCK(m_mutex);
         return m_orphans.size();
     }
 
 protected:
-    /** Guards orphan transactions */
-    mutable Mutex m_mutex;
-
     struct OrphanTx {
         CTransactionRef tx;
         NodeId fromPeer;
@@ -80,10 +76,10 @@ protected:
 
     /** Map from wtxid to orphan transaction record. Limited by
      *  -maxorphantx/DEFAULT_MAX_ORPHAN_TRANSACTIONS */
-    std::map<Wtxid, OrphanTx> m_orphans GUARDED_BY(m_mutex);
+    std::map<Wtxid, OrphanTx> m_orphans;
 
     /** Which peer provided the orphans that need to be reconsidered */
-    std::map<NodeId, std::set<Wtxid>> m_peer_work_set GUARDED_BY(m_mutex);
+    std::map<NodeId, std::set<Wtxid>> m_peer_work_set;
 
     using OrphanMap = decltype(m_orphans);
 
@@ -98,16 +94,13 @@ protected:
 
     /** Index from the parents' COutPoint into the m_orphans. Used
      *  to remove orphan transactions from the m_orphans */
-    std::map<COutPoint, std::set<OrphanMap::iterator, IteratorComparator>> m_outpoint_to_orphan_it GUARDED_BY(m_mutex);
+    std::map<COutPoint, std::set<OrphanMap::iterator, IteratorComparator>> m_outpoint_to_orphan_it;
 
     /** Orphan transactions in vector for quick random eviction */
-    std::vector<OrphanMap::iterator> m_orphan_list GUARDED_BY(m_mutex);
-
-    /** Erase an orphan by wtxid */
-    int EraseTxNoLock(const Wtxid& wtxid) EXCLUSIVE_LOCKS_REQUIRED(m_mutex);
+    std::vector<OrphanMap::iterator> m_orphan_list;
 
     /** Timestamp for the next scheduled sweep of expired orphans */
-    NodeSeconds m_next_sweep GUARDED_BY(m_mutex){0s};
+    NodeSeconds m_next_sweep{0s};
 };
 
 #endif // BITCOIN_TXORPHANAGE_H
diff --git a/src/validation.cpp b/src/validation.cpp
index 2b8f64e81a..b90fe48ca5 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -3473,6 +3473,7 @@ bool Chainstate::ActivateBestChain(BlockValidationState& state, std::shared_ptr<
 
         {
             LOCK(cs_main);
+            {
             // Lock transaction pool for at least as long as it takes for connectTrace to be consumed
             LOCK(MempoolMutex());
             const bool was_in_ibd = m_chainman.IsInitialBlockDownload();
@@ -3549,7 +3550,12 @@ bool Chainstate::ActivateBestChain(BlockValidationState& state, std::shared_ptr<
                     break;
                 }
             }
-        }
+            } // release MempoolMutex
+            // Notify external listeners about the new tip, even if pindexFork == pindexNewTip.
+            if (m_chainman.m_options.signals && this == &m_chainman.ActiveChainstate()) {
+                m_chainman.m_options.signals->ActiveTipChange(pindexNewTip, m_chainman.IsInitialBlockDownload());
+            }
+        } // release cs_main
         // When we reach this point, we switched to a new tip (stored in pindexNewTip).
 
         if (exited_ibd) {
@@ -3768,6 +3774,12 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
         // distinguish user-initiated invalidateblock changes from other
         // changes.
         (void)m_chainman.GetNotifications().blockTip(GetSynchronizationState(m_chainman.IsInitialBlockDownload(), m_chainman.m_blockman.m_blockfiles_indexed), *to_mark_failed->pprev);
+
+        // Fire ActiveTipChange now for the current chain tip to make sure clients are notified.
+        // ActivateBestChain may call this as well, but not necessarily.
+        if (m_chainman.m_options.signals) {
+            m_chainman.m_options.signals->ActiveTipChange(m_chain.Tip(), m_chainman.IsInitialBlockDownload());
+        }
     }
     return true;
 }
diff --git a/src/validationinterface.cpp b/src/validationinterface.cpp
index 579444a065..f5baa16c99 100644
--- a/src/validationinterface.cpp
+++ b/src/validationinterface.cpp
@@ -183,6 +183,12 @@ void ValidationSignals::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlo
                           fInitialDownload);
 }
 
+void ValidationSignals::ActiveTipChange(const CBlockIndex *new_tip, bool is_ibd)
+{
+    LOG_EVENT("%s: new block hash=%s block height=%d", __func__, new_tip->GetBlockHash().ToString(), new_tip->nHeight);
+    m_internals->Iterate([&](CValidationInterface& callbacks) { callbacks.ActiveTipChange(new_tip, is_ibd); });
+}
+
 void ValidationSignals::TransactionAddedToMempool(const NewMempoolTransactionInfo& tx, uint64_t mempool_sequence)
 {
     auto event = [tx, mempool_sequence, this] {
diff --git a/src/validationinterface.h b/src/validationinterface.h
index 6f49a73c93..3cc3566a60 100644
--- a/src/validationinterface.h
+++ b/src/validationinterface.h
@@ -62,6 +62,10 @@ protected:
      */
     virtual void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {}
     /**
+     * Notifies listeners any time the block chain tip changes, synchronously.
+     */
+    virtual void ActiveTipChange(const CBlockIndex* new_tip, bool is_ibd) {};
+    /**
      * Notifies listeners of a transaction having been added to mempool.
      *
      * Called on a background thread.
@@ -214,6 +218,7 @@ public:
     void SyncWithValidationInterfaceQueue() LOCKS_EXCLUDED(cs_main);
 
     void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
+    void ActiveTipChange(const CBlockIndex*, bool);
     void TransactionAddedToMempool(const NewMempoolTransactionInfo&, uint64_t mempool_sequence);
     void TransactionRemovedFromMempool(const CTransactionRef&, MemPoolRemovalReason, uint64_t mempool_sequence);
     void MempoolTransactionsRemovedForBlock(const std::vector<RemovedMempoolTransactionInfo>&, unsigned int nBlockHeight);