`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
```
std::vector<OutputGroup> groups;
    std::map<CTxDestination, OutputGroup> gmap;
    CTxDestination dst;
    for (const auto& output : outputs) {
        if (output.fSpendable) {
            CInputCoin input_coin = output.GetInputCoin();
            size_t ancestors, descendants;
            chain().getTransactionAncestry(output.tx->GetHash(), ancestors, descendants);
            if (!single_coin && ExtractDestination(output.tx->tx->vout[output.i].scriptPubKey, dst)) {
                
                
                
                if (gmap[dst].m_outputs.size() >= OUTPUT_GROUP_MAX_ENTRIES) {
                    groups.push_back(gmap[dst]);
                    gmap.erase(dst);
                }
                gmap[dst].Insert(input_coin, output.nDepth, output.tx->IsFromMe(ISMINE_ALL), ancestors, descendants);
            } else {
                groups.emplace_back(input_coin, output.nDepth, output.tx->IsFromMe(ISMINE_ALL), ancestors, descendants);
            }
        }
    }
    if (!single_coin) {
        for (const auto& it : gmap) groups.push_back(it.second);
    }
    return groups;
}
bool CWallet::GetKeyOrigin(const CKeyID& keyID, KeyOriginInfo& info) const