address review feedback

miner/payload_building.go

@@ -260,7 +260,11 @@ func (miner *Miner) buildPayload(args *BuildPayloadArgs, witness bool) (*Payload
 		for {
 			select {
 			case <-timer.C:
-				// Select is random, so we need to check if the payload has been stopped
+				// When block building takes close to the full recommit interval,
+				// the timer fires near-instantly on the next iteration. If the
+				// payload was resolved during that build, both timer.C and
+				// payload.stop are ready and Go's select picks one at random.
+				// Check payload.stop first to avoid an unnecessary generateWork.
 				select {
 				case <-payload.stop:
 					log.Info("Stopping work on payload", "id", payload.id, "reason", "delivery")