`LockAnnotation lock(::cs_main)` is a guarantee to the compiler thread analysis that `::cs_main` is locked (when it couldn't be determined otherwise).

Despite being annotated with the locking guarantee ...

https://github.com/bitcoin/bitcoin/blob/65526fc8666fef35ef908dbc225f706bef642c7e/src/interfaces/chain.cpp#L134-L138

... `getTipLocator()` reads `chainActive` (via `::ChainActive()`) without holding `cs_main`.

This can be verified by adding the following `AssertLockHeld(cs_main)`:

```
$ git diff
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 59623284d..9fc693a0f 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -134,6 +134,7 @@ class LockImpl : public Chain::Lock
     CBlockLocator getTipLocator() override
     {
         LockAnnotation lock(::cs_main);
+        AssertLockHeld(::cs_main);
         return ::ChainActive().GetLocator();
     }
     Optional<int> findLocatorFork(const CBlockLocator& locator) override
$ make check
../build-aux/test-driver: line 107: 12881 Aborted                 "$@" > $log_file 2>&1
FAIL: qt/test/test_bitcoin-qt
```
}
        
        if (walletInstance->CanSupportFeature(FEATURE_HD_SPLIT)) {
            walletInstance->WalletLogPrintf("Upgrading wallet to use HD chain split\n");
            walletInstance->SetMinVersion(FEATURE_PRE_SPLIT_KEYPOOL);
            split_upgrade = FEATURE_HD_SPLIT > prev_version;
        }
        
        if (split_upgrade) {
            walletInstance->MarkPreSplitKeys();
        }
        
        if (hd_upgrade) {
            if (!walletInstance->TopUpKeyPool()) {
                chain.initError(_("Unable to generate keys"));
                return nullptr;
            }
        }
    }
    if (fFirstRun)
    {
        
        walletInstance->SetMinVersion(FEATURE_LATEST);
        if ((wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
            
            walletInstance->SetWalletFlag(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
        } else if (wallet_creation_flags & WALLET_FLAG_BLANK_WALLET) {
            walletInstance->SetWalletFlag(WALLET_FLAG_BLANK_WALLET);
        } else {