Made use of random number generator in ForkJoin...

Made use of random number generator in ForkJoinScheduler's fair mode
thread safe. Review by plocinic.

1 files changed, 10 insertions, 4 deletions

diff --git a/src/actors/scala/actors/scheduler/ForkJoinScheduler.scala b/src/actors/scala/actors/scheduler/ForkJoinScheduler.scala
index ab4fca04ca..4aaef16661 100644
--- a/src/actors/scala/actors/scheduler/ForkJoinScheduler.scala
+++ b/src/actors/scala/actors/scheduler/ForkJoinScheduler.scala
@@ -3,7 +3,6 @@ package scheduler
 
 import java.util.{Collection, ArrayList}
 import scala.concurrent.forkjoin._
-import scala.util.Random
 
 /** The <code>ForkJoinScheduler</code> is backed by a lightweight
  *  fork-join task execution framework.
@@ -23,12 +22,19 @@ class ForkJoinScheduler(val initCoreSize: Int, val maxSize: Int, daemon: Boolean
 
   protected val CHECK_FREQ = 10
 
+  // this random number generator is only used in fair mode
+  private lazy val random = new java.util.Random // guarded by random
+
+  def this(d: Boolean, f: Boolean) {
+    this(ThreadPoolConfig.corePoolSize, ThreadPoolConfig.maxPoolSize, d, f)
+  }
+
   def this(d: Boolean) {
-    this(ThreadPoolConfig.corePoolSize, ThreadPoolConfig.maxPoolSize, d, true)
+    this(d, true) // default is fair
   }
 
   def this() {
-    this(false)
+    this(false) // default is non-daemon
   }
 
   private def makeNewPool(): DrainableForkJoinPool = {
@@ -109,7 +115,7 @@ class ForkJoinScheduler(val initCoreSize: Int, val maxSize: Int, daemon: Boolean
 
   override def executeFromActor(task: Runnable) {
     // in fair mode: 2% chance of submitting to global task queue
-    if (fair && Random.nextInt(50) == 1)
+    if (fair && random.synchronized { random.nextInt(50) == 1 })
       pool.execute(task)
     else
       task.asInstanceOf[RecursiveAction].fork()