Merge bitcoin/bitcoin#22014: refactor: Make m_cs_fee_estimator non-recursive

8c277b19c8f262e550cffe263e6d910b687ac882 refactor: Make m_cs_fee_estimator non-recursive (Hennadii Stepanov)
5ee5b696b588695ff78aaac08d5d85154f1953cf refactor: Add non-thread-safe CBlockPolicyEstimator::_removeTx helper (Hennadii Stepanov)
5c3033d45e5ec15499ce7a0222ffa0210a0f66bc Add thread safety annotations to CBlockPolicyEstimator public functions (Hennadii Stepanov)

Pull request description:

  This PR eliminates the only place that `m_cs_fee_estimator` is recursively locked by refactoring out `_removeTx` member function.

  Related to #19303.

ACKs for top commit:
  theStack:
    Code-review ACK 8c277b19c8f262e550cffe263e6d910b687ac882
  amadeuszpawlik:
    ACK 8c277b19c8f262e550cffe263e6d910b687ac882 reviewed, built and ran tests

Tree-SHA512: 65b0b59460d3d5fadf7e75e916b2898b0dcfafdf5b278ef8c3975660f67c9f88ae4b937944313bd36d7513a7a53e1e5859aaf4a6deb4a1aea089936b101635a1

2 files changed, 37 insertions, 14 deletions

diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index d8c21bd833..36cf786bd5 100644
--- a/src/policy/fees.cpp
+++ b/src/policy/fees.cpp
@@ -493,6 +493,12 @@ void TxConfirmStats::removeTx(unsigned int entryHeight, unsigned int nBestSeenHe
 bool CBlockPolicyEstimator::removeTx(uint256 hash, bool inBlock)
 {
     LOCK(m_cs_fee_estimator);
+    return _removeTx(hash, inBlock);
+}
+
+bool CBlockPolicyEstimator::_removeTx(const uint256& hash, bool inBlock)
+{
+    AssertLockHeld(m_cs_fee_estimator);
     std::map<uint256, TxStatsInfo>::iterator pos = mapMemPoolTxs.find(hash);
     if (pos != mapMemPoolTxs.end()) {
         feeStats->removeTx(pos->second.blockHeight, nBestSeenHeight, pos->second.bucketIndex, inBlock);
@@ -576,7 +582,8 @@ void CBlockPolicyEstimator::processTransaction(const CTxMemPoolEntry& entry, boo
 
 bool CBlockPolicyEstimator::processBlockTx(unsigned int nBlockHeight, const CTxMemPoolEntry* entry)
 {
-    if (!removeTx(entry->GetTx().GetHash(), true)) {
+    AssertLockHeld(m_cs_fee_estimator);
+    if (!_removeTx(entry->GetTx().GetHash(), true)) {
         // This transaction wasn't being tracked for fee estimation
         return false;
     }
@@ -985,7 +992,7 @@ void CBlockPolicyEstimator::FlushUnconfirmed() {
     // Remove every entry in mapMemPoolTxs
     while (!mapMemPoolTxs.empty()) {
         auto mi = mapMemPoolTxs.begin();
-        removeTx(mi->first, false); // this calls erase() on mapMemPoolTxs
+        _removeTx(mi->first, false); // this calls erase() on mapMemPoolTxs
     }
     int64_t endclear = GetTimeMicros();
     LogPrint(BCLog::ESTIMATEFEE, "Recorded %u unconfirmed txs from mempool in %gs\n", num_entries, (endclear - startclear)*0.000001);
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 27f9120c64..37a7051045 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -186,47 +186,59 @@ public:
 
     /** Process all the transactions that have been included in a block */
     void processBlock(unsigned int nBlockHeight,
-                      std::vector<const CTxMemPoolEntry*>& entries);
+                      std::vector<const CTxMemPoolEntry*>& entries)
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Process a transaction accepted to the mempool*/
-    void processTransaction(const CTxMemPoolEntry& entry, bool validFeeEstimate);
+    void processTransaction(const CTxMemPoolEntry& entry, bool validFeeEstimate)
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Remove a transaction from the mempool tracking stats*/
-    bool removeTx(uint256 hash, bool inBlock);
+    bool removeTx(uint256 hash, bool inBlock)
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** DEPRECATED. Return a feerate estimate */
-    CFeeRate estimateFee(int confTarget) const;
+    CFeeRate estimateFee(int confTarget) const
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Estimate feerate needed to get be included in a block within confTarget
      *  blocks. If no answer can be given at confTarget, return an estimate at
      *  the closest target where one can be given.  'conservative' estimates are
      *  valid over longer time horizons also.
      */
-    CFeeRate estimateSmartFee(int confTarget, FeeCalculation *feeCalc, bool conservative) const;
+    CFeeRate estimateSmartFee(int confTarget, FeeCalculation *feeCalc, bool conservative) const
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Return a specific fee estimate calculation with a given success
      * threshold and time horizon, and optionally return detailed data about
      * calculation
      */
-    CFeeRate estimateRawFee(int confTarget, double successThreshold, FeeEstimateHorizon horizon, EstimationResult *result = nullptr) const;
+    CFeeRate estimateRawFee(int confTarget, double successThreshold, FeeEstimateHorizon horizon,
+                            EstimationResult* result = nullptr) const
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Write estimation data to a file */
-    bool Write(CAutoFile& fileout) const;
+    bool Write(CAutoFile& fileout) const
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Read estimation data from a file */
-    bool Read(CAutoFile& filein);
+    bool Read(CAutoFile& filein)
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Empty mempool transactions on shutdown to record failure to confirm for txs still in mempool */
-    void FlushUnconfirmed();
+    void FlushUnconfirmed()
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Calculation of highest target that estimates are tracked for */
-    unsigned int HighestTargetTracked(FeeEstimateHorizon horizon) const;
+    unsigned int HighestTargetTracked(FeeEstimateHorizon horizon) const
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
     /** Drop still unconfirmed transactions and record current estimations, if the fee estimation file is present. */
-    void Flush();
+    void Flush()
+        EXCLUSIVE_LOCKS_REQUIRED(!m_cs_fee_estimator);
 
 private:
-    mutable RecursiveMutex m_cs_fee_estimator;
+    mutable Mutex m_cs_fee_estimator;
 
     unsigned int nBestSeenHeight GUARDED_BY(m_cs_fee_estimator);
     unsigned int firstRecordedHeight GUARDED_BY(m_cs_fee_estimator);
@@ -267,6 +279,10 @@ private:
     unsigned int HistoricalBlockSpan() const EXCLUSIVE_LOCKS_REQUIRED(m_cs_fee_estimator);
     /** Calculation of highest target that reasonable estimate can be provided for */
     unsigned int MaxUsableEstimate() const EXCLUSIVE_LOCKS_REQUIRED(m_cs_fee_estimator);
+
+    /** A non-thread-safe helper for the removeTx function */
+    bool _removeTx(const uint256& hash, bool inBlock)
+        EXCLUSIVE_LOCKS_REQUIRED(m_cs_fee_estimator);
 };
 
 class FeeFilterRounder