`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
```
* - If receiving a transaction outside a block, assign its timestamp to the
 *   current time.
 * - If receiving a block with a future timestamp, assign all its (not already
 *   known) transactions' timestamps to the current time.
 * - If receiving a block with a past timestamp, before the most recent known
 *   transaction (that we care about), assign all its (not already known)
 *   transactions' timestamps to the same timestamp as that most-recent-known
 *   transaction.
 * - If receiving a block with a past timestamp, but after the most recent known
 *   transaction, assign all its (not already known) transactions' timestamps to
 *   the block time.
 *
 * For more information see CWalletTx::nTimeSmart,
 * https:bitcointalk.org/?topic=54527, or
 * https:github.com/bitcoin/bitcoin/pull/1393.
 */
unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
{
    unsigned int nTimeSmart = wtx.nTimeReceived;
    if (!wtx.hashUnset()) {
        int64_t blocktime;
        if (chain().findBlock(wtx.hashBlock, nullptr , &blocktime)) {
            int64_t latestNow = wtx.nTimeReceived;
            int64_t latestEntry = 0;
            
            int64_t latestTolerated = latestNow + 300;
            const TxItems& txOrdered = wtxOrdered;
            for (auto it = txOrdered.rbegin(); it != txOrdered.rend(); ++it) {
                CWalletTx* const pwtx = it->second;
                if (pwtx == &wtx) {