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Author: zsxwing

core/src/main/scala/org/apache/spark/status/api/v1/ExecutorListResource.scala

@@ -29,6 +29,8 @@ private[v1] class ExecutorListResource(ui: SparkUI) {
   def executorList(): Seq[ExecutorSummary] = {
     val listener = ui.executorsListener
     listener.synchronized {
+      // The follow codes should be protected by `listener` to make sure no executors will be
+      // removed before we query their status. See SPARK-12784.
       val storageStatusList = listener.storageStatusList
       (0 until storageStatusList.size).map { statusId =>
         ExecutorsPage.getExecInfo(listener, statusId)

core/src/main/scala/org/apache/spark/ui/exec/ExecutorsPage.scala

@@ -53,6 +53,8 @@ private[ui] class ExecutorsPage(
 
   def render(request: HttpServletRequest): Seq[Node] = {
     val (storageStatusList, execInfo) = listener.synchronized {
+      // The follow codes should be protected by `listener` to make sure no executors will be
+      // removed before we query their status. See SPARK-12784.
       val _storageStatusList = listener.storageStatusList
       val _execInfo = {
         for (statusId <- 0 until _storageStatusList.size)