`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
```
#include <key_io.h>
#include <keystore.h>
#include <net.h>
#include <policy/fees.h>
#include <policy/policy.h>
#include <policy/rbf.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <script/descriptor.h>
#include <script/script.h>
#include <shutdown.h>
#include <timedata.h>
#include <txmempool.h>
#include <util/bip32.h>
#include <util/error.h>
#include <util/fees.h>
#include <util/moneystr.h>
#include <util/rbf.h>
#include <util/validation.h>
#include <validation.h>
#include <wallet/coincontrol.h>
#include <wallet/fees.h>
#include <algorithm>
#include <assert.h>
#include <future>
#include <boost/algorithm/string/replace.hpp>
static const size_t OUTPUT_GROUP_MAX_ENTRIES = 10;
static CCriticalSection cs_wallets;
static std::vector<std::shared_ptr<CWallet>> vpwallets GUARDED_BY(cs_wallets);
bool AddWallet(const std::shared_ptr<CWallet>& wallet)