`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
```
{
    AssertLockHeld(cs_wallet);
    return setExternalKeyPool.size() + set_pre_split_keypool.size();
}
void CWallet::LoadKeyPool(int64_t nIndex, const CKeyPool &keypool)
{
    AssertLockHeld(cs_wallet);
    if (keypool.m_pre_split) {
        set_pre_split_keypool.insert(nIndex);
    } else if (keypool.fInternal) {
        setInternalKeyPool.insert(nIndex);
    } else {
        setExternalKeyPool.insert(nIndex);
    }
    m_max_keypool_index = std::max(m_max_keypool_index, nIndex);
    m_pool_key_to_index[keypool.vchPubKey.GetID()] = nIndex;
    
    
    
    CKeyID keyid = keypool.vchPubKey.GetID();
    if (mapKeyMetadata.count(keyid) == 0)
        mapKeyMetadata[keyid] = CKeyMetadata(keypool.nTime);
}
bool CWallet::TopUpKeyPool(unsigned int kpSize)