refactor: replace isPotentialtip/waitForNotifications by higher method

Add GUARDED_BY(cs_wallet) annotation to m_last_block_processed, given
that its now guarded by cs_wallet instead of cs_main

Author: Antoine Riard

src/interfaces/chain.cpp

@@ -136,12 +136,6 @@ class LockImpl : public Chain::Lock
         }
         return nullopt;
     }
-    bool isPotentialTip(const uint256& hash) override
-    {
-        if (::chainActive.Tip()->GetBlockHash() == hash) return true;
-        CBlockIndex* block = LookupBlockIndex(hash);
-        return block && block->GetAncestor(::chainActive.Height()) == ::chainActive.Tip();
-    }
     CBlockLocator getTipLocator() override { return ::chainActive.GetLocator(); }
     Optional<int> findLocatorFork(const CBlockLocator& locator) override
     {
@@ -358,7 +352,16 @@ class ChainImpl : public Chain
     {
         return MakeUnique<NotificationsHandlerImpl>(*this, notifications);
     }
-    void waitForNotifications() override { SyncWithValidationInterfaceQueue(); }
+    void waitForNotificationsIfNewBlocksConnected(const uint256& old_tip) override
+    {
+        if (!old_tip.IsNull()) {
+            LOCK(::cs_main);
+            if (old_tip == ::chainActive.Tip()->GetBlockHash()) return;
+            CBlockIndex* block = LookupBlockIndex(old_tip);
+            if (block && block->GetAncestor(::chainActive.Height()) == ::chainActive.Tip()) return;
+        }
+        SyncWithValidationInterfaceQueue();
+    }
     std::unique_ptr<Handler> handleRpc(const CRPCCommand& command) override
     {
         return MakeUnique<RpcHandlerImpl>(command);

src/interfaces/chain.h

@@ -43,12 +43,6 @@ class Wallet;
 //!   asynchronously
 //!   (https://github.com/bitcoin/bitcoin/pull/10973#issuecomment-380101269).
 //!
-//! * The isPotentialTip() and waitForNotifications() methods are too low-level
-//!   and should be replaced with a higher level
-//!   waitForNotificationsUpTo(block_hash) method that the wallet can call
-//!   instead
-//!   (https://github.com/bitcoin/bitcoin/pull/10973#discussion_r266995234).
-//!
 //! * The relayTransactions() and submitToMemoryPool() methods could be replaced
 //!   with a higher-level broadcastTransaction method
 //!   (https://github.com/bitcoin/bitcoin/pull/14978#issuecomment-459373984).
@@ -132,11 +126,6 @@ class Chain
         //! information is desired).
         virtual Optional<int> findFork(const uint256& hash, Optional<int>* height) = 0;
 
-        //! Return true if block hash points to the current chain tip, or to a
-        //! possible descendant of the current chain tip that isn't currently
-        //! connected.
-        virtual bool isPotentialTip(const uint256& hash) = 0;
-
         //! Get locator for the current chain tip.
         virtual CBlockLocator getTipLocator() = 0;
 
@@ -271,8 +260,10 @@ class Chain
     //! Register handler for notifications.
     virtual std::unique_ptr<Handler> handleNotifications(Notifications& notifications) = 0;
 
-    //! Wait for pending notifications to be handled.
-    virtual void waitForNotifications() = 0;
+    //! Wait for pending notifications to be processed unless block hash points to the current
+    //! chain tip, or to a possible descendant of the current chain tip that isn't currently
+    //! connected.
+    virtual void waitForNotificationsIfNewBlocksConnected(const uint256& old_tip) = 0;
 
     //! Register handler for RPC. Command is not copied, so reference
     //! needs to remain valid until Handler is disconnected.

src/wallet/wallet.cpp

@@ -1288,24 +1288,12 @@ void CWallet::UpdatedBlockTip()
 
 void CWallet::BlockUntilSyncedToCurrentChain() {
     AssertLockNotHeld(cs_wallet);
-
-    {
-        // Skip the queue-draining stuff if we know we're caught up with
-        // chainActive.Tip()...
-        // We could also take cs_wallet here, and call m_last_block_processed
-        // protected by cs_wallet instead of cs_main, but as long as we need
-        // cs_main here anyway, it's easier to just call it cs_main-protected.
-        auto locked_chain = chain().lock();
-
-        if (!m_last_block_processed.IsNull() && locked_chain->isPotentialTip(m_last_block_processed)) {
-            return;
-        }
-    }
-
-    // ...otherwise put a callback in the validation interface queue and wait
+    // Skip the queue-draining stuff if we know we're caught up with
+    // chainActive.Tip(), otherwise put a callback in the validation interface queue and wait
     // for the queue to drain enough to execute it (indicating we are caught up
     // at least with the time we entered this function).
-    chain().waitForNotifications();
+    uint256 last_block_hash = WITH_LOCK(cs_wallet, return m_last_block_processed);
+    chain().waitForNotificationsIfNewBlocksConnected(last_block_hash);
 }
 
 

src/wallet/wallet.h

@@ -720,7 +720,7 @@ class CWallet final : public CCryptoKeyStore, private interfaces::Chain::Notific
      * to have seen all transactions in the chain, but is only used to track
      * live BlockConnected callbacks.
      */
-    uint256 m_last_block_processed;
+    uint256 m_last_block_processed GUARDED_BY(cs_wallet);
 
 public:
     /*