address review comments

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

@@ -1115,8 +1115,8 @@ private[spark] class TaskSetManager(
 
   def executorDecommission(execId: String): Unit = {
     recomputeLocality()
-    if (executorDecommissionKillInterval.nonEmpty) {
-      val executorKillTime = clock.getTimeMillis() + executorDecommissionKillInterval.get
+    executorDecommissionKillInterval.foreach { interval =>
+      val executorKillTime = clock.getTimeMillis() + interval
       runningTasksSet.filter(taskInfos(_).executorId == execId).foreach { tid =>
         tidToExecutorKillTimeMapping(tid) = executorKillTime
       }

core/src/test/scala/org/apache/spark/scheduler/TaskSetManagerSuite.scala

@@ -1942,6 +1942,9 @@ class TaskSetManagerSuite
     //   executorDecommissionSpeculationTriggerTimeoutOpt
     // (TASK2 -> 15, TASK3 -> 15)
     manager.executorDecommission("exec2")
+    assert(manager.tidToExecutorKillTimeMapping.keySet === Set(2, 3))
+    assert(manager.tidToExecutorKillTimeMapping(2) === 15)
+    assert(manager.tidToExecutorKillTimeMapping(3) === 15)
 
     assert(manager.checkSpeculatableTasks(0))
     // Task2 started at t=0, so it can still finish before t=15 (Median task runtime = 10)
@@ -1952,7 +1955,7 @@ class TaskSetManagerSuite
 
     // Offer resource to start the speculative attempt for the running task
     val taskOption3New = manager.resourceOffer("exec3", "host3", NO_PREF)._1
-    // Offer more resources. Noting should get scheduled now.
+    // Offer more resources. Nothing should get scheduled now.
     assert(manager.resourceOffer("exec3", "host3", NO_PREF)._1.isEmpty)
     assert(taskOption3New.isDefined)
 
@@ -1970,8 +1973,8 @@ class TaskSetManagerSuite
     assert(manager.copiesRunning(3) === 2)
 
     clock.advance(5) // time = 16 ms
-    // At t=16 ms, Task 4 has completed 16 ms. It is more than the
-    // SPECULATION_MULTIPLIER * medianRuntime = 1.5 * 10 = 15 ms. So now Task 4 will
+    // At t=16 ms, Task 2 has been running for 16 ms. It is more than the
+    // SPECULATION_MULTIPLIER * medianRuntime = 1.5 * 10 = 15 ms. So now Task 2 will
     // be selected for speculation. Here we are verifying that regular speculation configs
     // should still take effect even when a EXECUTOR_DECOMMISSION_KILL_INTERVAL is provided and
     // corresponding executor is decommissioned
@@ -1993,8 +1996,6 @@ class TaskSetManagerSuite
 
     // Offering additional resources should not lead to any speculative tasks being respawned
     assert(manager.resourceOffer("exec1", "host1", ANY)._1.isEmpty)
-    assert(manager.resourceOffer("exec2", "host2", ANY)._1.isEmpty)
-    assert(manager.resourceOffer("exec3", "host3", ANY)._1.isEmpty)
   }
 
   test("SPARK-21040: Check speculative tasks are not launched when an executor" +