refine comments.

Author: jinxing

core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala

@@ -1189,10 +1189,9 @@ class DAGScheduler(
               // This task was for the currently running attempt of the stage. Since the task
               // completed successfully from the perspective of the TaskSetManager, mark it as
               // no longer pending (the TaskSetManager may consider the task complete even
-              // when the output needs to be ignored because the task's epoch is too small below,
-              // if so, this can result in inconsistency between pending partitions and output
-              // locations of stage. When pending partitions is empty, the scheduler will check
-              // output locations, if there is missing, the stage will be resubmitted.
+              // when the output needs to be ignored because the task's epoch is too small below.
+              // In this case, when pending partitions is empty, there will still be missing
+              // output locations, which will cause the DAGScheduler to resubmit the stage below.)
               shuffleStage.pendingPartitions -= task.partitionId
             }
             if (failedEpoch.contains(execId) && smt.epoch <= failedEpoch(execId)) {