1 files changed, 37 insertions, 28 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index daa33d3f5a..477b3e1550 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2666,45 +2666,53 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
             SyncWithValidationInterfaceQueue();
         }
 
-        const CBlockIndex *pindexFork;
-        bool fInitialDownload;
         {
             LOCK(cs_main);
-            ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+            CBlockIndex* starting_tip = chainActive.Tip();
+            bool blocks_connected = false;
+            do {
+                // We absolutely may not unlock cs_main until we've made forward progress
+                // (with the exception of shutdown due to hardware issues, low disk space, etc).
+                ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+
+                if (pindexMostWork == nullptr) {
+                    pindexMostWork = FindMostWorkChain();
+                }
 
-            CBlockIndex *pindexOldTip = chainActive.Tip();
-            if (pindexMostWork == nullptr) {
-                pindexMostWork = FindMostWorkChain();
-            }
+                // Whether we have anything to do at all.
+                if (pindexMostWork == nullptr || pindexMostWork == chainActive.Tip()) {
+                    break;
+                }
 
-            // Whether we have anything to do at all.
-            if (pindexMostWork == nullptr || pindexMostWork == chainActive.Tip())
-                return true;
+                bool fInvalidFound = false;
+                std::shared_ptr<const CBlock> nullBlockPtr;
+                if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
+                    return false;
+                blocks_connected = true;
 
-            bool fInvalidFound = false;
-            std::shared_ptr<const CBlock> nullBlockPtr;
-            if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
-                return false;
+                if (fInvalidFound) {
+                    // Wipe cache, we may need another branch now.
+                    pindexMostWork = nullptr;
+                }
+                pindexNewTip = chainActive.Tip();
 
-            if (fInvalidFound) {
-                // Wipe cache, we may need another branch now.
-                pindexMostWork = nullptr;
-            }
-            pindexNewTip = chainActive.Tip();
-            pindexFork = chainActive.FindFork(pindexOldTip);
-            fInitialDownload = IsInitialBlockDownload();
+                for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
+                    assert(trace.pblock && trace.pindex);
+                    GetMainSignals().BlockConnected(trace.pblock, trace.pindex, trace.conflictedTxs);
+                }
+            } while (!chainActive.Tip() || (starting_tip && CBlockIndexWorkComparator()(chainActive.Tip(), starting_tip)));
+            if (!blocks_connected) return true;
 
-            for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
-                assert(trace.pblock && trace.pindex);
-                GetMainSignals().BlockConnected(trace.pblock, trace.pindex, trace.conflictedTxs);
-            }
+            const CBlockIndex* pindexFork = chainActive.FindFork(starting_tip);
+            bool fInitialDownload = IsInitialBlockDownload();
 
             // Notify external listeners about the new tip.
             // Enqueue while holding cs_main to ensure that UpdatedBlockTip is called in the order in which blocks are connected
-            GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
-
-            // Always notify the UI if a new block tip was connected
             if (pindexFork != pindexNewTip) {
+                // Notify ValidationInterface subscribers
+                GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
+
+                // Always notify the UI if a new block tip was connected
                 uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
             }
         }
@@ -2728,6 +2736,7 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
 
     return true;
 }
+
 bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) {
     return g_chainstate.ActivateBestChain(state, chainparams, std::move(pblock));
 }