`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
```
{
    assert(!IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
    assert(!IsWalletFlagSet(WALLET_FLAG_BLANK_WALLET));
    AssertLockHeld(cs_wallet);
    bool fCompressed = CanSupportFeature(FEATURE_COMPRPUBKEY); 
    CKey secret;
    
    int64_t nCreationTime = GetTime();
    CKeyMetadata metadata(nCreationTime);
    
    if (IsHDEnabled()) {
        DeriveNewChildKey(batch, metadata, secret, (CanSupportFeature(FEATURE_HD_SPLIT) ? internal : false));
    } else {
        secret.MakeNewKey(fCompressed);
    }
    
    if (fCompressed) {
        SetMinVersion(FEATURE_COMPRPUBKEY);
    }
    CPubKey pubkey = secret.GetPubKey();
    assert(secret.VerifyPubKey(pubkey));
    mapKeyMetadata[pubkey.GetID()] = metadata;
    UpdateTimeFirstKey(nCreationTime);
    if (!AddKeyPubKeyWithDB(batch, secret, pubkey)) {
        throw std::runtime_error(std::string(__func__) + ": AddKey failed");
    }
    return pubkey;
}
void CWallet::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata& metadata, CKey& secret, bool internal)