3 files changed, 13 insertions, 15 deletions
diff --git a/src/library/scala/collection/concurrent/TrieMap.scala b/src/library/scala/collection/concurrent/TrieMap.scala
index 08e9125bd8..2d8217551a 100644
--- a/src/library/scala/collection/concurrent/TrieMap.scala
+++ b/src/library/scala/collection/concurrent/TrieMap.scala
@@ -473,7 +473,11 @@ extends CNodeBase[K, V] {
   private def computeSize(ct: TrieMap[K, V]): Int = {
     var i = 0
     var sz = 0
-    val offset = math.abs(util.Random.nextInt()) % array.length
+    val offset =
+      if (array.length > 0)
+        //util.Random.nextInt(array.length) /* <-- benchmarks show that this causes observable contention */
+        scala.concurrent.forkjoin.ThreadLocalRandom.current.nextInt(0, array.length)
+      else 0
     while (i < array.length) {
       val pos = (i + offset) % array.length
       array(pos) match {
diff --git a/src/library/scala/collection/mutable/ArrayOps.scala b/src/library/scala/collection/mutable/ArrayOps.scala
index 01636eb54e..7a595f211d 100644
--- a/src/library/scala/collection/mutable/ArrayOps.scala
+++ b/src/library/scala/collection/mutable/ArrayOps.scala
@@ -64,7 +64,7 @@ abstract class ArrayOps[T] extends ArrayLike[T, Array[T]] with CustomParalleliza
    *  @param asTrav    A function that converts elements of this array to rows - arrays of type `U`.
    *  @return          An array obtained by concatenating rows of this array.
    */
-  def flatten[U, To](implicit asTrav: T => collection.Traversable[U], m: ClassTag[U]): Array[U] = {
+  def flatten[U](implicit asTrav: T => collection.Traversable[U], m: ClassTag[U]): Array[U] = {
     val b = Array.newBuilder[U]
     b.sizeHint(map{case is: collection.IndexedSeq[_] => is.size case _ => 0}.sum)
     for (xs <- this)
diff --git a/src/library/scala/concurrent/SyncVar.scala b/src/library/scala/concurrent/SyncVar.scala
index 292014706d..5a6d95c2ed 100644
--- a/src/library/scala/concurrent/SyncVar.scala
+++ b/src/library/scala/concurrent/SyncVar.scala
@@ -53,8 +53,6 @@ class SyncVar[A] {
     value
   }
 
-  /** Waits for this SyncVar to become defined and returns
-   *  the result */
   def take(): A = synchronized {
     try get
     finally unsetVal()
@@ -66,8 +64,7 @@ class SyncVar[A] {
    *  the SyncVar.
    *
    *  @param timeout     the amount of milliseconds to wait, 0 means forever
-   *  @return            the value or a throws an exception if the timeout occurs
-   *  @throws NoSuchElementException on timeout
+   *  @return            `None` if variable is undefined after `timeout`, `Some(value)` otherwise
    */
   def take(timeout: Long): A = synchronized {
     try get(timeout).get
@@ -75,28 +72,25 @@ class SyncVar[A] {
   }
 
   // TODO: this method should be private
-  // [Heather] the reason why: it doesn't take into consideration
+  // [Heather] the reason why: it doesn't take into consideration 
   // whether or not the SyncVar is already defined. So, set has been
   // deprecated in order to eventually be able to make "setting" private
   @deprecated("Use `put` instead, as `set` is potentionally error-prone", "2.10.0")
   def set(x: A): Unit = setVal(x)
 
-  /** Places a value in the SyncVar. If the SyncVar already has a stored value,
-   * it waits until another thread takes it */
   def put(x: A): Unit = synchronized {
     while (isDefined) wait()
     setVal(x)
   }
 
-  /** Checks whether a value is stored in the synchronized variable */
   def isSet: Boolean = synchronized {
     isDefined
   }
 
   // TODO: this method should be private
-  // [Heather] the reason why: it doesn't take into consideration
+  // [Heather] the reason why: it doesn't take into consideration 
   // whether or not the SyncVar is already defined. So, unset has been
-  // deprecated in order to eventually be able to make "unsetting" private
+  // deprecated in order to eventually be able to make "unsetting" private  
   @deprecated("Use `take` instead, as `unset` is potentionally error-prone", "2.10.0")
   def unset(): Unit = synchronized {
     isDefined = false
@@ -104,7 +98,7 @@ class SyncVar[A] {
     notifyAll()
   }
 
-  // `setVal` exists so as to retroactively deprecate `set` without
+  // `setVal` exists so as to retroactively deprecate `set` without 
   // deprecation warnings where we use `set` internally. The
   // implementation of `set` was moved to `setVal` to achieve this
   private def setVal(x: A): Unit = synchronized {
@@ -113,13 +107,13 @@ class SyncVar[A] {
     notifyAll()
   }
 
-  // `unsetVal` exists so as to retroactively deprecate `unset` without
+  // `unsetVal` exists so as to retroactively deprecate `unset` without 
   // deprecation warnings where we use `unset` internally. The
   // implementation of `unset` was moved to `unsetVal` to achieve this
   private def unsetVal(): Unit = synchronized {
     isDefined = false
     value = None
-    notifyAll()
+    notifyAll()    
   }
 
 }