diff --git a/core/src/main/scala/org/apache/spark/SparkStatusTracker.scala b/core/src/main/scala/org/apache/spark/SparkStatusTracker.scala
index 52c4656c271bc..22a553e68439a 100644
--- a/core/src/main/scala/org/apache/spark/SparkStatusTracker.scala
+++ b/core/src/main/scala/org/apache/spark/SparkStatusTracker.scala
@@ -112,7 +112,7 @@ class SparkStatusTracker private[spark] (sc: SparkContext) {
    */
   def getExecutorInfos: Array[SparkExecutorInfo] = {
     val executorIdToRunningTasks: Map[String, Int] =
-      sc.taskScheduler.asInstanceOf[TaskSchedulerImpl].runningTasksByExecutors()
+      sc.taskScheduler.asInstanceOf[TaskSchedulerImpl].runningTasksByExecutors
 
     sc.getExecutorStorageStatus.map { status =>
       val bmId = status.blockManagerId
diff --git a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
index b2ef41e126871..feab4be31e40b 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
@@ -91,7 +91,7 @@ private[spark] class TaskSchedulerImpl(
   // IDs of the tasks running on each executor
   private val executorIdToRunningTaskIds = new HashMap[String, HashSet[Long]]
 
-  def runningTasksByExecutors(): Map[String, Int] = {
+  def runningTasksByExecutors: Map[String, Int] = synchronized {
     executorIdToRunningTaskIds.toMap.mapValues(_.size)
   }
 
diff --git a/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
index 19b6fec9aec83..46c6a935f92a2 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/TaskSchedulerImplSuite.scala
@@ -304,7 +304,7 @@ class TaskSchedulerImplSuite extends SparkFunSuite with LocalSparkContext with L
     // Check that state associated with the lost task attempt is cleaned up:
     assert(taskScheduler.taskIdToExecutorId.isEmpty)
     assert(taskScheduler.taskIdToTaskSetManager.isEmpty)
-    assert(taskScheduler.runningTasksByExecutors().get("executor0").isEmpty)
+    assert(taskScheduler.runningTasksByExecutors.get("executor0").isEmpty)
   }
 
   test("if a task finishes with TaskState.LOST its executor is marked as dead") {
@@ -335,7 +335,7 @@ class TaskSchedulerImplSuite extends SparkFunSuite with LocalSparkContext with L
     // Check that state associated with the lost task attempt is cleaned up:
     assert(taskScheduler.taskIdToExecutorId.isEmpty)
     assert(taskScheduler.taskIdToTaskSetManager.isEmpty)
-    assert(taskScheduler.runningTasksByExecutors().get("executor0").isEmpty)
+    assert(taskScheduler.runningTasksByExecutors.get("executor0").isEmpty)
 
     // Check that the executor has been marked as dead
     assert(!taskScheduler.isExecutorAlive("executor0"))