Made changes based on PR comments.

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -865,26 +865,25 @@ private[spark] object Utils extends Logging {
   }
 
   /** Default filtering function for finding call sites using `getCallSite`. */
-  private def defaultCallSiteFilterFunc(className: String): Boolean = {
+  private def coreExclusionFunction(className: String): Boolean = {
     // A regular expression to match classes of the "core" Spark API that we want to skip when
     // finding the call site of a method.
     val SPARK_CORE_CLASS_REGEX = """^org\.apache\.spark(\.api\.java)?(\.util)?(\.rdd)?\.[A-Z]""".r
     val SCALA_CLASS_REGEX = """^scala""".r
-    val isSparkClass = SPARK_CORE_CLASS_REGEX.findFirstIn(className).isDefined
+    val isSparkCoreClass = SPARK_CORE_CLASS_REGEX.findFirstIn(className).isDefined
     val isScalaClass = SCALA_CLASS_REGEX.findFirstIn(className).isDefined
-    // If the class neither belongs to Spark nor is a simple Scala class, then it is a
-    // user-defined class
-    !isSparkClass && !isScalaClass
+    // If the class is a Spark internal class or a Scala class, then exclude.
+    isSparkCoreClass || isScalaClass
   }
 
   /**
    * When called inside a class in the spark package, returns the name of the user code class
    * (outside the spark package) that called into Spark, as well as which Spark method they called.
    * This is used, for example, to tell users where in their code each RDD got created.
    *
-   * @param classFilterFunc Function that returns true if the given class belongs to user code
+   * @param skipClass Function that is used to exclude non-user-code classes.
    */
-  def getCallSite(classFilterFunc: String => Boolean = defaultCallSiteFilterFunc): CallSite = {
+  def getCallSite(skipClass: String => Boolean = coreExclusionFunction): CallSite = {
     val trace = Thread.currentThread.getStackTrace()
       .filterNot { ste:StackTraceElement =>
         // When running under some profilers, the current stack trace might contain some bogus
@@ -905,7 +904,7 @@ private[spark] object Utils extends Logging {
 
     for (el <- trace) {
       if (insideSpark) {
-        if (!classFilterFunc(el.getClassName)) {
+        if (skipClass(el.getClassName)) {
           lastSparkMethod = if (el.getMethodName == "<init>") {
             // Spark method is a constructor; get its class name
             el.getClassName.substring(el.getClassName.lastIndexOf('.') + 1)

streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala

@@ -447,7 +447,7 @@ class StreamingContext private[streaming] (
       throw new SparkException("StreamingContext has already been stopped")
     }
     validate()
-    sparkContext.setCallSite(DStream.getCallSite())
+    sparkContext.setCallSite(DStream.getCreationSite())
     scheduler.start()
     state = Started
   }

streaming/src/main/scala/org/apache/spark/streaming/dstream/DStream.scala

@@ -108,7 +108,7 @@ abstract class DStream[T: ClassTag] (
   def context = ssc
 
   /* Set the creation call site */
-  private[streaming] val creationSite = DStream.getCallSite()
+  private[streaming] val creationSite = DStream.getCreationSite()
 
   /** Persist the RDDs of this DStream with the given storage level */
   def persist(level: StorageLevel): DStream[T] = {
@@ -805,25 +805,25 @@ abstract class DStream[T: ClassTag] (
 private[streaming] object DStream {
 
   /** Get the creation site of a DStream from the stack trace of when the DStream is created. */
-  def getCallSite(): CallSite = {
+  def getCreationSite(): CallSite = {
     val SPARK_CLASS_REGEX = """^org\.apache\.spark""".r
     val SPARK_STREAMING_TESTCLASS_REGEX = """^org\.apache\.spark\.streaming\.test""".r
     val SPARK_EXAMPLES_CLASS_REGEX = """^org\.apache\.spark\.examples""".r
     val SCALA_CLASS_REGEX = """^scala""".r
 
-    /** Filtering function that returns true for classes that belong to a streaming application */
-    def streamingClassFilterFunc(className: String): Boolean = {
+    /** Filtering function that excludes non-user classes for a streaming application */
+    def streamingExclustionFunction(className: String): Boolean = {
       def doesMatch(r: Regex) = r.findFirstIn(className).isDefined
       val isSparkClass = doesMatch(SPARK_CLASS_REGEX)
       val isSparkExampleClass = doesMatch(SPARK_EXAMPLES_CLASS_REGEX)
       val isSparkStreamingTestClass = doesMatch(SPARK_STREAMING_TESTCLASS_REGEX)
       val isScalaClass = doesMatch(SCALA_CLASS_REGEX)
 
       // If the class is a spark example class or a streaming test class then it is considered
-      // as a streaming application class. Otherwise, consider any non-Spark and non-Scala class
-      // as streaming application class.
-      isSparkExampleClass || isSparkStreamingTestClass || !(isSparkClass || isScalaClass)
+      // as a streaming application class and don't exclude. Otherwise, exclude any
+      // non-Spark and non-Scala class, as the rest would streaming application classes.
+      (isSparkClass || isScalaClass) && !isSparkExampleClass && !isSparkStreamingTestClass
     }
-    org.apache.spark.util.Utils.getCallSite(streamingClassFilterFunc)
+    org.apache.spark.util.Utils.getCallSite(streamingExclustionFunction)
   }
 }