Merge #12367: Fix two fast-shutdown bugs

dd2de47 Fix fast-shutdown crash if genesis block was not loaded (Matt Corallo)
1c9394a Fix fast-shutdown hang on ThreadImport+GenesisWait (Matt Corallo)

Pull request description:

  The second commit is a much simpler alternative fix for the issue fixed in #12349. To test I made ShutdownRequested() always StartShutdown() after a certain number of calls, which turned up one other hang, fixed in the first commit.

Tree-SHA512: 86bde6ac4b8b4e2cb99fff87dafeed02c0d9514acee6d94455637fb2da9ffc274b5ad31b0a6b9f5bd7b700ae35395f28ddb14ffc65ddda3619aa28df28a5607d

1 files changed, 7 insertions, 3 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 16b656c7f5..f1abe6f46d 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2581,9 +2581,6 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
             SyncWithValidationInterfaceQueue();
         }
 
-        if (ShutdownRequested())
-            break;
-
         const CBlockIndex *pindexFork;
         bool fInitialDownload;
         {
@@ -2630,6 +2627,13 @@ bool CChainState::ActivateBestChain(CValidationState &state, const CChainParams&
         }
 
         if (nStopAtHeight && pindexNewTip && pindexNewTip->nHeight >= nStopAtHeight) StartShutdown();
+
+        // We check shutdown only after giving ActivateBestChainStep a chance to run once so that we
+        // never shutdown before connecting the genesis block during LoadChainTip(). Previously this
+        // caused an assert() failure during shutdown in such cases as the UTXO DB flushing checks
+        // that the best block hash is non-null.
+        if (ShutdownRequested())
+            break;
     } while (pindexNewTip != pindexMostWork);
     CheckBlockIndex(chainparams.GetConsensus());