`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
```
nLastResend = GetTime();
    int relayed_tx_count = 0;
    { 
        auto locked_chain = chain().lock();
        LOCK(cs_wallet);
        
        for (std::pair<const uint256, CWalletTx>& item : mapWallet) {
            CWalletTx& wtx = item.second;
            
            
            if (wtx.nTimeReceived > m_best_block_time - 5 * 60) continue;
            if (wtx.RelayWalletTransaction(*locked_chain)) ++relayed_tx_count;
        }
    } 
    if (relayed_tx_count > 0) {
        WalletLogPrintf("%s: rebroadcast %u unconfirmed transactions\n", __func__, relayed_tx_count);
    }
}
 
void MaybeResendWalletTxs()
{
    for (const std::shared_ptr<CWallet>& pwallet : GetWallets()) {
        pwallet->ResendWalletTransactions();
    }
}
/** @defgroup Actions
 *
 * @{
 */
CWallet::Balance CWallet::GetBalance(const int min_depth) const