`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
```
balances[addr] += n;
            }
        }
    }
    return balances;
}
std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
{
    AssertLockHeld(cs_wallet);
    std::set< std::set<CTxDestination> > groupings;
    std::set<CTxDestination> grouping;
    for (const auto& walletEntry : mapWallet)
    {
        const CWalletTx& wtx = walletEntry.second;
        if (wtx.tx->vin.size() > 0)
        {
            bool any_mine = false;
            
            for (const CTxIn& txin : wtx.tx->vin)
            {
                CTxDestination address;
                if(!IsMine(txin)) 
                    continue;
                if(!ExtractDestination(mapWallet.at(txin.prevout.hash).tx->vout[txin.prevout.n].scriptPubKey, address))
                    continue;
                grouping.insert(address);
                any_mine = true;
            }
            
            if (any_mine)