1 files changed, 38 insertions, 8 deletions

diff --git a/src/validationinterface.h b/src/validationinterface.h
index ed6c560944..f9a359b7ad 100644
--- a/src/validationinterface.h
+++ b/src/validationinterface.h
@@ -30,6 +30,14 @@ void RegisterValidationInterface(CValidationInterface* pwalletIn);
 void UnregisterValidationInterface(CValidationInterface* pwalletIn);
 /** Unregister all wallets from core */
 void UnregisterAllValidationInterfaces();
+
+// Alternate registration functions that release a shared_ptr after the last
+// notification is sent. These are useful for race-free cleanup, since
+// unregistration is nonblocking and can return before the last notification is
+// processed.
+void RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
+void UnregisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
+
 /**
  * Pushes a function to callback onto the notification queue, guaranteeing any
  * callbacks generated prior to now are finished when the function is called.
@@ -92,10 +100,32 @@ protected:
     /**
      * Notifies listeners of a transaction leaving mempool.
      *
-     * This only fires for transactions which leave mempool because of expiry,
-     * size limiting, reorg (changes in lock times/coinbase maturity), or
-     * replacement. This does not include any transactions which are included
-     * in BlockConnectedDisconnected either in block->vtx or in txnConflicted.
+     * This notification fires for transactions that are removed from the
+     * mempool for the following reasons:
+     *
+     * - EXPIRY (expired from mempool after -mempoolexpiry hours)
+     * - SIZELIMIT (removed in size limiting if the mempool exceeds -maxmempool megabytes)
+     * - REORG (removed during a reorg)
+     * - CONFLICT (removed because it conflicts with in-block transaction)
+     * - REPLACED (removed due to RBF replacement)
+     *
+     * This does not fire for transactions that are removed from the mempool
+     * because they have been included in a block. Any client that is interested
+     * in transactions removed from the mempool for inclusion in a block can learn
+     * about those transactions from the BlockConnected notification.
+     *
+     * Transactions that are removed from the mempool because they conflict
+     * with a transaction in the new block will have
+     * TransactionRemovedFromMempool events fired *before* the BlockConnected
+     * event is fired. If multiple blocks are connected in one step, then the
+     * ordering could be:
+     *
+     * - TransactionRemovedFromMempool(tx1 from block A)
+     * - TransactionRemovedFromMempool(tx2 from block A)
+     * - TransactionRemovedFromMempool(tx1 from block B)
+     * - TransactionRemovedFromMempool(tx2 from block B)
+     * - BlockConnected(A)
+     * - BlockConnected(B)
      *
      * Called on a background thread.
      */
@@ -106,7 +136,7 @@ protected:
      *
      * Called on a background thread.
      */
-    virtual void BlockConnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex, const std::vector<CTransactionRef> &txnConflicted) {}
+    virtual void BlockConnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex) {}
     /**
      * Notifies listeners of a block being disconnected
      *
@@ -141,7 +171,7 @@ protected:
      * Notifies listeners that a block which builds directly on our current tip
      * has been received and connected to the headers tree, though not validated yet */
     virtual void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& block) {};
-    friend void ::RegisterValidationInterface(CValidationInterface*);
+    friend void ::RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface>);
     friend void ::UnregisterValidationInterface(CValidationInterface*);
     friend void ::UnregisterAllValidationInterfaces();
 };
@@ -151,7 +181,7 @@ class CMainSignals {
 private:
     std::unique_ptr<MainSignalsInstance> m_internals;
 
-    friend void ::RegisterValidationInterface(CValidationInterface*);
+    friend void ::RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface>);
     friend void ::UnregisterValidationInterface(CValidationInterface*);
     friend void ::UnregisterAllValidationInterfaces();
     friend void ::CallFunctionInValidationInterfaceQueue(std::function<void ()> func);
@@ -170,7 +200,7 @@ public:
     void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
     void TransactionAddedToMempool(const CTransactionRef &);
     void TransactionRemovedFromMempool(const CTransactionRef &);
-    void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex, const std::shared_ptr<const std::vector<CTransactionRef>> &);
+    void BlockConnected(const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex);
     void BlockDisconnected(const std::shared_ptr<const CBlock> &, const CBlockIndex* pindex);
     void ChainStateFlushed(const CBlockLocator &);
     void BlockChecked(const CBlock&, const BlockValidationState&);