address comment

br/pkg/streamhelper/advancer.go

@@ -505,8 +505,7 @@ func (c *CheckpointAdvancer) optionalTick(cx context.Context) error {
 	// lastCheckpoint is not increased too long enough.
 	// assume the cluster has expired locks for whatever reasons.
 	var targets []spans.Valued
-	if c.lastCheckpoint != nil && c.lastCheckpoint.needResolveLocks() && !c.inResolvingLock.Load() {
-		c.inResolvingLock.Store(true)
+	if c.lastCheckpoint != nil && c.lastCheckpoint.needResolveLocks() && c.inResolvingLock.CompareAndSwap(false, true) {
 		c.WithCheckpoints(func(vsf *spans.ValueSortedFull) {
 			// when get locks here. assume these locks are not belong to same txn,
 			// but these locks' start ts are close to 1 minute. try resolve these locks at one time