`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
```
{
    Balance ret;
    {
        auto locked_chain = chain().lock();
        LOCK(cs_wallet);
        for (const auto& entry : mapWallet)
        {
            const CWalletTx& wtx = entry.second;
            const bool is_trusted{wtx.IsTrusted(*locked_chain)};
            const int tx_depth{wtx.GetDepthInMainChain(*locked_chain)};
            const CAmount tx_credit_mine{wtx.GetAvailableCredit(*locked_chain,  true, ISMINE_SPENDABLE)};
            const CAmount tx_credit_watchonly{wtx.GetAvailableCredit(*locked_chain,  true, ISMINE_WATCH_ONLY)};
            if (is_trusted && tx_depth >= min_depth) {
                ret.m_mine_trusted += tx_credit_mine;
                ret.m_watchonly_trusted += tx_credit_watchonly;
            }
            if (!is_trusted && tx_depth == 0 && wtx.InMempool()) {
                ret.m_mine_untrusted_pending += tx_credit_mine;
                ret.m_watchonly_untrusted_pending += tx_credit_watchonly;
            }
            ret.m_mine_immature += wtx.GetImmatureCredit(*locked_chain);
            ret.m_watchonly_immature += wtx.GetImmatureWatchOnlyCredit(*locked_chain);
        }
    }
    return ret;
}
CAmount CWallet::GetAvailableBalance(const CCoinControl* coinControl) const