diff --git a/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala b/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
index 684db6646765f..11bd2d3b939de 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
@@ -152,17 +152,24 @@ class DAGScheduler(
   // may lead to more delay in scheduling if those locations are busy.
   private[scheduler] val REDUCER_PREF_LOCS_FRACTION = 0.2
 
-  // Called by TaskScheduler to report task's starting.
+  /**
+   * Called by the TaskSetManager to report task's starting.
+   */
   def taskStarted(task: Task[_], taskInfo: TaskInfo) {
     eventProcessLoop.post(BeginEvent(task, taskInfo))
   }
 
-  // Called to report that a task has completed and results are being fetched remotely.
+  /**
+   * Called by the TaskSetManager to report that a task has completed
+   * and results are being fetched remotely.
+   */
   def taskGettingResult(taskInfo: TaskInfo) {
     eventProcessLoop.post(GettingResultEvent(taskInfo))
   }
 
-  // Called by TaskScheduler to report task completions or failures.
+  /**
+   * Called by the TaskSetManager to report task completions or failures.
+   */
   def taskEnded(
       task: Task[_],
       reason: TaskEndReason,
@@ -188,18 +195,24 @@ class DAGScheduler(
       BlockManagerHeartbeat(blockManagerId), new RpcTimeout(600 seconds, "BlockManagerHeartbeat"))
   }
 
-  // Called by TaskScheduler when an executor fails.
+  /**
+   * Called by TaskScheduler implementation when an executor fails.
+   */
   def executorLost(execId: String): Unit = {
     eventProcessLoop.post(ExecutorLost(execId))
   }
 
-  // Called by TaskScheduler when a host is added
+  /**
+   * Called by TaskScheduler implementation when a host is added.
+   */
   def executorAdded(execId: String, host: String): Unit = {
     eventProcessLoop.post(ExecutorAdded(execId, host))
   }
 
-  // Called by TaskScheduler to cancel an entire TaskSet due to either repeated failures or
-  // cancellation of the job itself.
+  /**
+   * Called by the TaskSetManager to cancel an entire TaskSet due to either repeated failures or
+   * cancellation of the job itself.
+   */
   def taskSetFailed(taskSet: TaskSet, reason: String, exception: Option[Throwable]): Unit = {
     eventProcessLoop.post(TaskSetFailed(taskSet, reason, exception))
   }
@@ -352,7 +365,9 @@ class DAGScheduler(
     parents.toList
   }
 
-  /** Find ancestor missing shuffle dependencies and register into shuffleToMapStage */
+  /**
+   * Find ancestor missing shuffle dependencies and register into shuffleToMapStage.
+   */
   private def registerShuffleDependencies(shuffleDep: ShuffleDependency[_, _, _], firstJobId: Int) {
     val parentsWithNoMapStage = getAncestorShuffleDependencies(shuffleDep.rdd)
     while (parentsWithNoMapStage.nonEmpty) {
@@ -362,7 +377,9 @@ class DAGScheduler(
     }
   }
 
-  /** Find ancestor shuffle dependencies that are not registered in shuffleToMapStage yet */
+  /**
+   * Find ancestor shuffle dependencies that are not registered in shuffleToMapStage yet.
+   */
   private def getAncestorShuffleDependencies(rdd: RDD[_]): Stack[ShuffleDependency[_, _, _]] = {
     val parents = new Stack[ShuffleDependency[_, _, _]]
     val visited = new HashSet[RDD[_]]
@@ -646,7 +663,9 @@ class DAGScheduler(
     }
   }
 
-  /** Finds the earliest-created active job that needs the stage */
+  /**
+   * Finds the earliest-created active job that needs the stage.
+   */
   // TODO: Probably should actually find among the active jobs that need this
   // stage the one with the highest priority (highest-priority pool, earliest created).
   // That should take care of at least part of the priority inversion problem with
@@ -746,7 +765,9 @@ class DAGScheduler(
     submitWaitingStages()
   }
 
-  /** Submits stage, but first recursively submits any missing parents. */
+  /**
+   * Submits stage, but first recursively submits any missing parents.
+   */
   private def submitStage(stage: Stage) {
     val jobId = activeJobForStage(stage)
     if (jobId.isDefined) {
@@ -769,7 +790,9 @@ class DAGScheduler(
     }
   }
 
-  /** Called when stage's parents are available and we can now do its task. */
+  /**
+   * Called when stage's parents are available and we can now do its task.
+   */
   private def submitMissingTasks(stage: Stage, jobId: Int) {
     logDebug("submitMissingTasks(" + stage + ")")
     // Get our pending tasks and remember them in our pendingTasks entry
@@ -912,7 +935,9 @@ class DAGScheduler(
     }
   }
 
-  /** Merge updates from a task to our local accumulator values */
+  /**
+   * Merge updates from a task to our local accumulator values.
+   */
   private def updateAccumulators(event: CompletionEvent): Unit = {
     val task = event.task
     val stage = stageIdToStage(task.stageId)
@@ -1259,7 +1284,9 @@ class DAGScheduler(
     }
   }
 
-  /** Fails a job and all stages that are only used by that job, and cleans up relevant state. */
+  /**
+   * Fails a job and all stages that are only used by that job, and cleans up relevant state.
+   */
   private def failJobAndIndependentStages(
       job: ActiveJob,
       failureReason: String,
@@ -1309,7 +1336,9 @@ class DAGScheduler(
     }
   }
 
-  /** Return true if one of stage's ancestors is target. */
+  /**
+   * Return true if one of stage's ancestors is target.
+   */
   private def stageDependsOn(stage: Stage, target: Stage): Boolean = {
     if (stage == target) {
       return true